Nghiên cứu sữa part 2

When an exemplarysample is found, it may be maintained in the refrigerator and used as an inoculumfor production of future training samples.5 3.4.2 Cottage Cheese 3.4.2./ Introduction Co

Figure 3.8 Composite diagram of the skin in cross-section Tactile sensations are transmitted from the variety of nerve endings, for example, the free nerve endings and the tactile discs

in the epidermis, and the meissner corpuscles, end bulbs of Krause, Ruffini endings, and pacinian corpuscles in the dermis (Reproduced with permission from ref 35.)

Swiss style strawberry yogurt were added With the exception of a few war years, the contest has been held annually Fifty-nine schools have fielded teams with as many as 33 participating in 1956 5 ' 37 Several regional collegiate contests are also held each year At the high school level, the Future Farmers of America conducts

an annual state and national dairy foods evaluation contest These have served to give thousand of students training in the recognition of dairy product defects, their causes, and control.

Many other food industries have developed their *'expert" tasters resources These experts obtained experience through the years and were charged wih the re- sponsibility of determining the material blend or judging the quality of raw materials They also judge the quality of finished product and identify sources of problems and suggestions for correction when the products are less than perfect These experts include the perfumers, flavorists, brew masters, wine makers, and coffee and tea tasters In most of these industries, such as the dairy industry, scorecards and point systems have been developed to help set standards.

Nerve ending

wound hair Subcutaneous fat corpuscle Padnian ItNMt gland Duct of Ruffini ending

Free nerve endings Tactile discs

Dermis Epidermis

Smooth muscle

Meissner's corpuscle Sebaceous gland -

Hair End bulbs of Krause

With the growth of the food industry and the expansion of product lines within companies, it has become almost impossible to have dependable expert judges of all products It has been necessary to develop sensory evaluation systems that are more universally applicable Sensory evaluation of foods in general with methodology appropriate for either consensus or statistically sound evaluation of foods began to develop in the 1940s and 1950s at the U.S Army Quartermaster Food and Container Institute in Chicago 39 ' 40 Development began also in the private sector The Arthur

D Little Company pioneered descriptive analysis by developing a Flavor Profile Method that uses a consensus of a small group of people who are trained to the product in a way that is universally applicable The single expert was replaced with five or six trained people 41 The University of California at Davis began to offer courses on sensory evaluation in the 1950s The literature at that time reflects sig- nificant development in the application of sensory evaluation Discrimination tests were developed by Boggs and Hansen, 42 Girardot et al., 43 and Peryam et al 39 Rank- ing and hedonic scales began to be used for consumer acceptance information Com- mittee E-18 of the American Society for Testing Materials, the Food and Agriculture Section of the American Chemical Society, the European Chemoreception Organi- zation, and the Sensory Evaluation Division of the Institute of Food Technologists got involved by organizing activities focusing attention on sensory evaluation and measurement of flavor and publishing information assisting the food industry in application of the new techniques 40 These methods are all applicable to dairy prod- uct evaluation.

Hedonic scales are used to rate the degree of liking of products An example of

a nine-point hedonic scale is shown in Figure 3.9 There are a wide variety of hedonic

or liking scales that can be and have been used Recommended scales are balanced with an odd number of choices, with the middle choice being neutral "Neither like nor dislike." Choices above neutral are positive, with the top being "Like ex- tremely" and the choices below neutral being negative and balanced with those above and the bottom being "Dislike extremely." The data can be treated para- metrically, yielding means and standard deviations Liking of products can be com-

pared using the t test or analysis of variance (ANOVA) Parametric treatment

as-sumes that data are distributed normally and that intervals on the scale are equal There has been considerable discussion about the validity of these assumptions but the practical value of this approach continues to be demonstrated The data can be converted to preference or ranking and analyzed binomially 40 ' 44 ' 45

Another affective tool is preference testing Panelists have the opportunity in preference testing to tell which of two samples they prefer (paired comparison) or

Please check a box indicating your feeling about this product.

Like extremely Like very much Like moderately Like slightly Neither like nor dislike Dislike slightly Dislike moderately Dislike very much Dislike extremely

Figure 3.9 An example of the nine-point hedonic scale The subjects indicate to what extent they like or dislike the sample by checking a box by the most correct statement.

Please check a box indicating your feeling about the moistness/dryness of this product

Much too moist Slightly too moist Just about right Slightly too dry Much too dry

Figure 3.10 An example of a Just-about-right scale The purpose of the judgment is to establish how close to ideal a product is in an easily understood attribute The subject checks the box by the statement that best describes his or her feelings about the correctness of the level of that attribute.

to rank more than two samples in order of preference It is important that each sample

is tasted first and last its share of the time to avoid order bias Analysis of the paired comparison test utilizes binomial statistics Tables are available giving the number

of subjects that must prefer one sample given a certain number of participants for the preference to be significant 46 When ranking is used, tables and formulas are available showing the rank sum difference required for significantly different ranking given the number of samples compared and number of panelists used 47

An effective tool to determine the ideality of easily understood attributes is the Just-about-right scale This is the three- or five-point scale with "Just about right" being the middle response with balanced descriptors of the attribute extremes going

up and down from ideal (Fig 3.10) Stone suggests two methods of analyzing the

data to determine if each product deviates significantly from ideal and one method

to determine if the samples deviate from one another in ideality 40 One involves

using the binomial table of Roessler et al (p = 0.5, two-tailed) to determine if the

number of judgments on one side of ideal is more than can be explained by chance 46

The number of nonideal judgments is n and the number on one side of ideal is found

in the column under the appropriate confidence level.

The appropriate type of panelist for all affective tests is a "naive" consumer, one who has no knowledge of the objective of the comparison or the technology involved

in making the products The subjects may be screened to be representative of the demographics of a certain target consumer group Trained panelists who are used in descriptive or discrimination tests should not be used because of their analytical approach which may bias affective judgments 40

3.2.3 Discrimination Testing

Discrimination testing is a very useful sensory evaluation tool that enables one to determine if a perceived difference exists between two products Often it is prelim- inary to other types of testing If no perceived difference exists, it is not necessary

to determine which one is preferred or what the difference in the descriptive acteristics are 40 If a development objective is to have no perceived difference, this test can establish that the objective has been met and subsequent sensory testing may not be necessary There are several methods that may be used to establish whether there is a perceived difference Methods include paired-comparison, duo-trio, and triangle tests.

char-The paired comparison test is a two-sample test with the task being to determine whether the products are the same or different, or it may be to choose which of the two samples has more of a particular attribute When the subject is asked if the products are the same or different, it is important that half the panelists receive samples that are the same and half receive samples that are different In interpreting the data, the number of correct choices are compared with the number of correct selections that can be explained by chance When the assignment is to indicate which sample has more or less of a certain attribute, it is assumed that the subject recognizes that attribute in the product It is important that the attributes be simple and easily recognizable If the number of correct selections if greater than can be explained by chance, one can conclude that the samples are different Interpretation involves bi- nomial statistics A table and formula for the significant number of correct judgments

is published by Roessler et al 46 The correct table and formula would be those where the probability of being right by chance in one selection is one in two (p = 0.5) It

is a one-tailed test The tail of interest is being correct more frequently than can be explained by chance The other tail not of interest is being wrong more frequently than can be explained by chance Protection against a type I error (finding difference when none exists) is selected by selecting the column with the appropriate a An a

of 0.05 would allow for a 5% chance of a type I error.48

The duo-trio test was developed by Peryam and Swartz as a way to minimize the number of comparisons that have to be made The subject is given a reference

sample and two coded samples One of the coded samples is the same as the reference sample The subject is asked to indicate which sample is the same as (or different from) the reference In variations of the test, the reference sample may be removed after it is tasted to force the use of memory for comparison Reliance on memory decreases the sensitivity of the test The same sample may be used as the reference through the entire test, or each sample may take its turn as the reference It is im- portant that the order of tasting the two samples be rotated so that each sample is tasted immediately after the reference with equal frequency The data are evaluated using the same formula and tables as for paired comparisons 46 The probability of

being correct on one decision is one in two (p = 0.5) and interest is in one tail

(being right more frequently than can be explained by chance).

The most frequently used discrimination test is the triangle test It was initially developed by a beer company 49 In this test, the panelist is presented three coded samples Two are the same and one is different The panelist evaluates all three and determines which one is different or which two are most alike This test requires more tasting than the others Three pairs are compared in making the judgment Again binomial statistics are used to evaluate the results The probability of being

right by chance (p) in one selection is one in three and it is a one-tailed test (the

probability of being wrong more frequently than is explained by chance is the tail that is not of interest) 40 The table and formula provided by Roessler et al are used

to determine when the frequency of correct selection exceeds chance 46

Subjects for discrimination tests should like the product, be familiar with the test procedure, have frequent practice with the test, have a record of exceeding chance

in choosing correctly in previous tests, and have no specific knowledge about the samples 40 The number of panelists used should be no more than 40 and may be as few as 12 to 15 Too many panelists will result in significant differences when the differences are very subtle and of no practical importance Too few will allow for a large type II error (finding no difference when difference exists) 30 ' 48

It is important to guard against unintended differences For example, it is easy to have slight temperature, serving amount, piece shape or size, or color differences that are not intended Panelists are playing a game and will look for any clues that will reveal the different sample If a conclusion is reached, due to inadvertent hints that samples are different when they are not, the results can be misleading and expensive Further development or costly consumer or descriptive testing may be mandated.

3.2.4 Descriptive Analysis

Descriptive analysis is the process of developing a total sensory description of a product In its complete form it involves identifying each flavor, aroma, and textural quality detectable in the product and quantifying each The time sequence of the detection of the qualities can also be included in the profile Affective judgments as

to the desirability of the sensory qualities are generally not a part of descriptive analysis It is important that the panel members are highly trained to recognize all

of the qualities of the product and to use a standardized terminology to describe

them Developing and proving a descriptive panel requires skill on the part of the leaders, and dedication, time, patience, and attention to detail on the part of panel leaders and panelists 30 ' 40 Several methods of descriptive analysis have been devel- oped Three that represent the development of descriptive analysis and slightly dif- ferent philosophies are the Flavor Profile, Texture Profile, and Quantitative Descrip- tive Analysis (QDA).

The Flavor Profile method was developed by Arthur D Little, Inc in the late 1940s A small panel of four to six trained judges analyze a product's perceived aroma and flavor qualities, and their order of detection, intensity, and aftertaste They also assess the degree to which various flavor or aroma characteristics fit together

and their appropriateness in the product and call this characteristic amplitude 41 ' 50

Prospective panelists are screened for their ability to detect and discriminate tastes and odors Their interest and availability and ability to work with a group are as- sessed in a personal interview Selected panelists are trained with product examples that represent the extremes of the different qualities that may be encountered Product

is made with a variety of ingredients and processes to produce a wide variety of product In the actual evaluation session, trained panelists first evaluate a product individually while seated together around a table The results are reported to the panel leader who leads a discussion that results in a consensus profile More than one sample can be profiled in a session but they are done one at a time without tasting back and forth Once a panel is trained, profiles can be obtained easily 10 ' 40

General Foods developed the Texture Profile method to do for texture analysis what the Flavor Profile method had done for flavor and aroma 51 " 53 It was different from flavor profiling in that the terminology for different texture qualities was standardized (Table 3.2) The anchors used to standardize the scales were also pre- defined Odd numbered categorical scales for each quality were developed Later quality descriptors were added for semisolid foods, beverages, 54 ' 55 and skin-feel products 56 Prospective panelists are screened based on interest, availability, and attitude They are further selected on the basis of ability to discriminate known textural differences in the product to be tested They are introduced to the principles involved in the product to be tested An evaluation of a product after the panel is trained involves independent evaluation by each panelist using one of a number of possible scales, then the generation of a panel verdict The verdict may be obtained

by discussion and group consensus similar to the method for obtaining a flavor profile

or by statistical analysis of the data.

Quantitative Descriptive Analysis was developed to overcome weaknesses in the descriptive test previously described It was designed to be responsive to flavor, aroma, and texture simultaneously, to be applicable to a broad range of products, to

be quantitative in evaluation of panelists' qualifications and in development of files, to use a small number of panelists, and to have flexible panel-generated ter- minology Subjects are qualified before participation They must be available and be users of the product class They must demonstrate ability to perceive differences within the class of products and to articulate those differences The terms used to describe qualities may be available from previous work If so, the panel learns and experiences the definitions of all the qualities If not, the terms describing the qual-

pro-Figure 3.11 An example of a horizontal line scale used by descriptive panelists to indicate

the strength of a particular flavor or aroma quality The subjects marks the position of the linethat describes the intensity of the quality

ities are selected and defined by the panelist as they train Reference materials thatare examples of the qualities are used to aid in definition of qualities When evalu-ating actual product, if new qualities are found, the panel reconvenes to define andtrain on that quality Scales used are horizontal lines of a consistent length with worddescriptors at or near the ends (Fig 3.11) Intensity always increases from left toright and the subject marks the line at a position that is appropriate for the intensity

of the quality Evaluation during training and on actual product is done individually

Reproduced with permission from ref 52.

P l e a s e m a r k this line in a position that indicates h o w

w e a k / f i r m you feel this yogurt body to b e

Extremely

weak

Extremely firm

Table 3,2 RELATIONSHIP BETWEEN TEXTURAL PARAMETERS AND

Particle size and shape

Particle shape and orientation

Primary Parameters

Moisture content

Fat content

Mechanical Characteristics Secondary Parameters

Brittleness Chewiness Gumminess

Geometrical characteristics

Other Characteristics Secondary Parameters

Oiliness Greasiness

Popular Terms Soft, firm, hard Crumbly, crunchy, brittle Tender, chewy, tough Short, mealy, pasty, gummy Thin, viscous

Plastic, elastic Sticky, tacky, gooey

Examples Gritty, grainy, coarse, etc Fibrous, cellular, crystalline, etc.

Popular Terms Dry, moist, wet, watery Oily

Greasy

Figure 3.12 Visual display of the sensory characteristics based on the results of a

Quanti-tiative Descriptive Analysis (QDA) test For each characteristic, the relative intensity increases

as it goes further from the center (Reproduced with permission from ref 40.)

and usually in isolated sensory booths to ensure independent analysis Replicatesamples are included so that ANOVA can be applied to evaluate the panelists' con-sistency as well as to statistically compare the intensity of qualities of the differentsamples The panelists who are best able to replicate themselves on all the qualitiesand who agree best with the rest of the panel on each of the qualities are best qualified

to evaluate product Usually between 8 and 12 qualified subjects constitute a panel.The product QDA profile is a listing of the qualities and the means for each of thosequalities Significance of difference between samples in each quality is obtained byANOVA.40 Multiple-range tests are applied to establish the significance of differ-ences between multiple samples Profiles of individual samples can be shown in anumber of formats A "spider web" format is shown in Figure 3.12 Each quality

is depicted as a "spoke" of a wheel with its length being indicative of the intensity

of the quality With the ends of the "spokes" connected, a shape is formed that isdistinct A change of intensity in one attribute produces a readily distinguishabledifference in shape

3.3 Application of Sensory Analysis to Dairy Products

The system for evaluating dairy products for defects was developed long before thegenerally applicable tools of affective, difference, and descriptive analysis These

Bitterness

Malt Flavor

SourCrunch

(initial)

Crunch(final)

Sweet

Aroma

Aftertaste

newer generally applicable tools are as useful for dairy products as they are for other foods and are essential when sensory information needs to be quantified for research purposes Any treatment of sensory analysis of dairy products without their mention would be incomplete The remainder of this chapter, however, will focus on evalu- ation of dairy products for defects or judging of dairy products This ability, although not designed for statistical analysis or research, is still very useful to dairy product manufacturers, enabling them to recognize defects, identify causes and take correc- tive action.

3.3.1 The Philosophy of Judging of Dairy Products

Judging of dairy products is related to descriptive analysis It is similar in that flavor (including aroma), texture, and appearance can all be evaluated It is similar too in that the names of the qualities and their definitions are standardized The quality terms and definitions have evolved over the years with USDA and industry "ex- perts" involved and a committee of collegiate coaches, who serve as the American Dairy Science Committee on Dairy Product Evaluation, periodically modifying the terms and definitions It is different from descriptive analysis in that normal ideal base qualities of the products are not identified and only the defects are noted The judges score the products on flavor, texture, and appearance Score ranges are es- tablished for each defect Defects that are indicative of serious problems have lower score ranges than less serious defects Higher scores in that range are given if the defect is slight and scores at the lower end of the range are given when defects are pronounced In the event of multiple defects, the score is based on the defect that would result in the lowest score In that way, scoring takes into account the mag- nitude and seriousness of the defects as determined by these "experts." No attempt has been made to tie the scores to consumer acceptance of the products.

3.4 Descriptive Sensory Defects of Dairy Products

3.4.1 Fluid Milk and Cream

3.4.1.1 Introduction

Fluid milk is the material from which all other dairy products are made Defects in milk will cany over into those products so it is important that these defects be recognized first Coaches of collegiate judging teams spend a generous amount of time on fluid milk because the defects of milk are closely related to the resulting defects in products, and because "doctoring" milk to simulate the defects is rela- tively easy 5 A wide variety of fluid milk and cream products are available A listing

of products is shown in Table 3.3 Complete evaluation of fluid milk can include examination and scoring of a sediment disk, evaluation of the package, storage tem- perature, and bacteria count 5 Table 3.4 shows flavor defects that can be found in milk and the range of scores that can be assigned A score card that includes all these important defect descriptors is shown in Figure 3.13 It is based on a possible 25

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newer generally applicable tools are as useful for dairy products as they are for other foods and are essential when sensory information needs to be quantified for research purposes Any treatment of sensory analysis of dairy products without their mention would be incomplete The remainder of this chapter, however, will focus on evalu- ation of dairy products for defects or judging of dairy products This ability, although not designed for statistical analysis or research, is still very useful to dairy product manufacturers, enabling them to recognize defects, identify causes and take correc- tive action.

3.3.1 The Philosophy of Judging of Dairy Products

Judging of dairy products is related to descriptive analysis It is similar in that flavor (including aroma), texture, and appearance can all be evaluated It is similar too in that the names of the qualities and their definitions are standardized The quality terms and definitions have evolved over the years with USDA and industry "ex- perts" involved and a committee of collegiate coaches, who serve as the American Dairy Science Committee on Dairy Product Evaluation, periodically modifying the terms and definitions It is different from descriptive analysis in that normal ideal base qualities of the products are not identified and only the defects are noted The judges score the products on flavor, texture, and appearance Score ranges are es- tablished for each defect Defects that are indicative of serious problems have lower score ranges than less serious defects Higher scores in that range are given if the defect is slight and scores at the lower end of the range are given when defects are pronounced In the event of multiple defects, the score is based on the defect that would result in the lowest score In that way, scoring takes into account the mag- nitude and seriousness of the defects as determined by these "experts." No attempt has been made to tie the scores to consumer acceptance of the products.

3.4 Descriptive Sensory Defects of Dairy Products

3.4.1 Fluid Milk and Cream

3.4.1.1 Introduction

Fluid milk is the material from which all other dairy products are made Defects in milk will cany over into those products so it is important that these defects be recognized first Coaches of collegiate judging teams spend a generous amount of time on fluid milk because the defects of milk are closely related to the resulting defects in products, and because "doctoring" milk to simulate the defects is rela- tively easy 5 A wide variety of fluid milk and cream products are available A listing

of products is shown in Table 3.3 Complete evaluation of fluid milk can include examination and scoring of a sediment disk, evaluation of the package, storage tem- perature, and bacteria count 5 Table 3.4 shows flavor defects that can be found in milk and the range of scores that can be assigned A score card that includes all these important defect descriptors is shown in Figure 3.13 It is based on a possible 25

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Source: American Dairy Science Association, 1990.

a "No criticisms'' is assigned a score of 10 Normal range is 1 - 1 0 for salable product.

b An assigned score of 0 (zero) is indicative of unsalable product.

points with 10 possible on flavor, three on sediment, five on package, five on bacteriacount, and two on temperature The electronic score card now used in collegiatecompetition in which only flavor is judged is shown in Figure 3.14 The flavor ofmilk is usually judged after sediment, closure, and container are judged This treat-ment will cover only flavor For information on how the other factors are judged seeBodyfelt.5 To best judge flavor, the milk or cream should be tempered to 12.8 to18°C The judge should swirl the bottle and then smell the milk or cream Swirlingserves to mix the sample and to spread a fine film on the inside of the containerwhich gives maximum opportunity for volatiles to fill the headspace A small amount

of sample should be poured into a clean odorless container Glass is preferred butplastic or paper is acceptable The judge should then take a sample into his or hermouth, and move it around in the mouth making sure to coat all the surfaces of the

Table 3.3 A USTING OF FRESH MILK AND CREAM

PRODUCTS WITH FAT CONTENT INPARENTHESES57

Table 3.4 THE ADSA SCORING GUIDE FOR OFF-FLAVORS

ON MILK AND CREAM

3 5 8 6 5 9 5 5 8 6 5 5 4 8 3

Definite 1 3 8 4 3 8 3 3 7 4 3 3 1 6 1

Pronounced

0 b

1 6 1 1 7 1 1 6 1 1 1 0 4 0

SCORE CARD FOR MILK QUALITY

SAMPLE NO.

Signatures of evaluators

Figure 3.13 A modified and expanded version of the ADSA milk score card (Reproduced

from ref 5, with permission of the ADSA, Champaign, IL.)

Oxidized light induced

Oxidized metal induced

Figure 3.14 Collegiate contest milk score card (Reproduced from ref 5, with permission

of the ADSA, Champaign, IL.)

mouth from the front to deep in the back down to the throat, noting any off-flavors.While the sample is in the mouth, airis moved up through the nose to enhance odordetection The sample should then be expectorated and a few moments allowed toobserve aftertaste Aftertaste and aroma sensation are enhanced by exhaling slowlythrough the nose Swallowing sample is not advised According to Bodyfelt,5 theflavor of whole milk should be pleasant and sweet and with neither a foretaste nor

an aftertaste other than that imparted by the natural richness A listing of flavorcriticisms with a scoring guide is shown in Table 3.4 A list of these defects, andtheir verbal descriptions, causes, and methods of preparing training samples follows

3.4.1.2 Flavor Defects

Acid or Sour Milk

Description Acid or sour is detected by both the senses of taste and smell The

tip of the tongue is sensitive to the "peeling" or "tingling" sensation A generalfeeling of "cleanliness" and enhanced ability to taste is part of the sensation Otherflavors such as diacetyl may accompany acid as byproducts of fermentation.5

Cause Acid or sour milk is a result of bacterial action on lactose converting it to

lactic acid It can be produced by culture organisms such as Lactococcus lactis ssp.

lactis, or Lactococcus lactis ssp cremoris or by any other lactic acid fermenting

organism that purposely or accidentally is present in milk and is allowed to grow

Training Sample Preparation Small amounts of lactic acid can be dissolved in

milk until the desired intensity of acid is obtained Addition of 25 ± 5 to 10 ml offresh cultured buttermilk can be added to 575 ml of fresh milk It should be prepared

1 or 2 days before tasting and held refrigerated until use.5 Usually a diacetyl flavoraccompanies the acid flavor

Astringent

Description This sensory defect is actually a tactile sensation Other descriptive

words used are mouth coating, dry, puckery, chalky, and powdery It is classifiedhere with flavor because it is sensed when the product is taken into the mouth It isnot a common defect in beverage milk After expectoration, the lining of the mouthmay feel shriveled or puckered

Cause Not all the causes are known but it is usually associated with high heat

treatment of milk that has caused some aggregation of milk proteins A specificparticle size of milk proteins or other milk constituents is thought to be responsiblefor the sensation

Training Green persimmon or alum are extreme examples of astringency They

may be used to demonstrate the sensation

Barny

Description The flavors ' 'cowy," ' 'barny," and * 'unclean'' seem to be quite alike

but differ in intensity and cause The descriptive term "barny" is quite accurate,

referring to the typical smell of a poorly maintained bam atmosphere It is noticedimmediately after the milk is expectorated.5

Cause The smells of the barn are thought to be transmitted to the milk through

the cow's respiratory system when cows are stabled and milked in a foul smellingbarn environment

Training Trainees could be taken to some milking operations and the atmospheric

aroma noted Milk could be collected from cows that are kept in this type of closedenvironment, lab pasteurized, and used soon after as training samples

Bitter

Description Bitter is a taste sensation with no associated aroma It is detected at

the base of the tongue The reaction time is fairly slow so it is most strongly sensedafter the milk is expectorated The intensity builds and it is hard to rinse away andrefresh the tongue It seems to be a component of "rancid" and "soapy" flavors.5

Cause It is generally acknowledged that some protein fragments taste bitter These

fragments can be produced by enzymatic breakdown of milk proteins Enzymesources in milk are likely psychrotrophic microorganisms that have grown in thecool milk Milk that is stored at temperatures at or slightly above 4°C for severaldays will become bitter if these contaminating organisms are present Under thoseconditions they will grow to large populations and release proteases Certain weedsconsumed by the cow will also impart bitterness to the milk Conditions that producerancidity may be to blame for bitterness that is a component of rancidity

Preparation of Training Samples Traces of quinine dihydrochloride or quinine

sulfate added to milk will give a clean bitter flavor A 1 % stock milk or water solutioncan be made and added at the rate of 1 to 2 ml per 600 ml of milk.5

Cooked

Description Four kinds of heat-induced flavors have been recognized: sulfurous,

rich, caramelized, and scorched All are easily identified.58 They are detected mediately as the sample is placed in the mouth and are usually considered to bepleasant The sulfurous and rich descriptors are common in milk The detection of

im-a cooked egg white smell is chim-arim-acteristic of this defect

Cause The mild sulfurous flavor develops when milk reaches 76°C to 78°C.59 This

is slightly above HTST pasteurization temperatures Its development is associatedwith the breaking of disulfide bonds and the development of conditions that dis-courage oxidation The more severe flavors of scorched and caramelized develop athigher temperatures and by a different mechanism and are not normal in beveragemilk The heated flavor is what remains after cooked milk is stored cold for a period

of time Caramelized flavor frequently intensifies and becomes more objectionablewith age.5

Preparation of Training Samples Fresh pasteurized/homogenized milk is heated

to 800C and held for 1 min and then cooled.5 This can be done on a plate pasteurizer,

in a water bath, or in a pan on a stove top with continual stirring

Cowy

Description Usually a "cowy" flavor suggests a cows-breath-like odor and a

chemical aftertaste It seems to be associated with the presence of acetone bodies inmilk.5

Cause Cows that have acetonemia or ketosis will give milk with this off-flavor

defect

Feed

Description A "feed" flavor is aromatic and sometimes pleasant After the milk

is expectorated a mild aftertaste of "cleanliness" can be present that disappearsrather quickly, leaving the mouth free of off flavors Cowy, barny, and uncleanflavors by contrast persist with an accompanying unpleasant or "dirty" aftertaste.Feed flavor varies with the type of feed consumed The odor is characteristic ofthe feed.5

Cause High-volume roughage feeds consumed within 3 h of milking impart flavors

and aromas to the milk.5 Silage, some hays, and brewery waste are particularlynotable for this A change of feed from dry hay to fresh green pasture often initiates

a strong feed flavor in the milk If 3 h is allowed to pass between consumption andmilking, almost all feed flavors are absent from the milk.5

Preparation of Training Samples An alfalfa flavor can be simulated by adding

and placing 2 to 3 g of alfalfa hay in 100 ml of fresh pasteurized and homogenizedmilk and holding for 20 min The milk is then strained through a cheesecloth orpaper towel and used as a stock solution To 575 ml of fresh pasteurized and ho-mogenized milk, add 20 to 35 ml of this stock milk solution Grass or corn silagecan be used to prepare feed flavored milks in the same manner.5

Fermented/Fruity

Description This defect is detected by its odor which resembles the odor of

sauer-kraut, vinegar, pineapple, or apple There will also be an unpleasant flavor that willlinger long after the sample has been expectorated

Cause This flavor is often found in bulk raw milk after lengthy storage Certain

microorganisms such as Pseudomonas fragi and other Pseudomonas species are

among those that produce aromatic fermentation products.60

Preparation of Training Samples Bodyfelt suggests the preparation of a stock

solution of 1% ethyl hexanoate About 1.0 to 1.25 ml of this solution is added to

600 ml of fresh pasteurized and homogenized milk.5

Description Flat milk gives a watery sensation or a lack of flavor richness No

aroma is associated with flat flavor but the lack of sweet and salty notes becomesapparent immediately as the milk enters the mouth and the subtle thinner mouth feelmay also be notable.5

Cause Flat flavor is generally caused by dilution with water It can happen at the

farm or in the plant by allowing too much rinse water to pass into the milk before

it is diverted Purposeful dilution with water is also possible

Preparation of Training Samples To prepare slightly flat samples add 75 to 100

ml of good quality tap water to 500 ml of fresh pasteurized and homogenized milk.For definite flat use 110 to 120 ml of water to 485 ml of milk.5

Foreign

Description The term *'foreign" is used to describe a number of flavors that are

imparted by addition of detergents, disinfectants, and sanitizers to milk The flavor

is characteristic of the chemical that has been added The flavors are atypical of milkand do not develop in milk In some cases the chemical may be detected by smellbut in others it may not be detected until it is tasted

Cause Adding milk to a vat or running milk through piping that has been washed

or sanitized but not rinsed can cause a foreign flavor especially if allowed to cominglewith a considerable amount of liquid containing the chemical Other possible causesinclude treating the udder with ointments or medication, contamination with insec-ticides, and drenching the cow with chemical treatments

Preparation of Training Samples Bodyfelt et al suggests that a foreign flavor

may be created by adding 3 to 4 ml of twofold vanilla extract to 600 ml of milk and

that a foreign flavor caused by sanitizer can be produced by adding 1.0 ml of a 5%

sodium hyperchloride solution to 600 ml of good quality milk.5 Samples can bemade by adding traces of other nontoxic chemical cleaners and sanitizers to milk atlow concentrations

Garlic/Onion (Weedy)

Description These flavors are identified by their characteristic pungent flavor and

aroma and persistent after taste

Cause Milk is tainted with these flavors during the warm months when cows are

feeding in pastures that are infested with onion, garlic, or other weeds that impartthese flavors to the milk They are especially strong when the cows consume theseplants shortly before they are milked

Preparation of Training Samples To produce a definite garlic/onion intensity, add

0.15 g of garlic or onion salt or two drops of extract to 600 ml of good qualitypasteurized and homogenized milk Vary the amounts to get the desired flavorstrength

Lacks Freshness

Description This flavor lacks descriptive characteristics It suggests the loss of

fine taste qualities typically noted in good milk It is not as pleasantly sweet andrefreshing or as free of an aftertaste as is typically desired in milk Frequently low-fat milks when compared with whole milk will exhibit this characteristic

Cause The ' 'lacks freshness" characteristic is often considered to be early stages

of the development of oxidized or rancid flavor or it could be the beginning ofdegradation by psychrotrophic bacteria

Preparation of Training Samples This characteristic is often present in milk that

is approaching its pull date about a week and a half to two weeks after processing

It can also be simulated by addition of 10 to 15 g nonfat dry milk powder to

600 ml of pasteurized and homogenized milk.5

Malty

Description As is suggested by the descriptive term, this flavor is suggestive of

malt Malt, which is grain (barley) softened by steeping and allowed to germinate,has this characteristic flavor This flavor can be detected by smelling or tasting themilk and is often accompanied by or is the forerunner of an acid taste.5

Cause This flavor in milk is usually caused by the growth of Streptococcus lactis

ssp lactis var maltigenes bacteria They grow well when the temperature is allowed

to rise above 18.2°C for 2 to 3 h.60

Preparation of Training Samples This flavor can be easily transferred from malted

cereals to milk A stock solution is made by soaking 15 g of Grape Nuts in 100 g

of milk for 30 min The milk is filtered through cheesecloth or a napkin Thirteenmilliliters of the stock solution is added to 590 ml of pasteurized and homogenizedmilk to give a malty flavored milk of definite intensity

Oxidized (Metal-Induced)

Description This flavor is a result of lipid oxidation that is induced by catalytic

action of certain metals Other synonymous terms are metallic, oily, cappy, boardy, stale, tallowy, painty, and fishy It is characterized by an immediate tastereaction on placing the sample in the mouth and a moderate aftertaste A puckerymouth feel characterizes high-intensity oxidized flavors It is similar to the flavor ofmetal foil, a rusty nail, or an old penny.5

card-Cause The presence of this flavor usually means that some corrodible metal has

come in contact with the milk It usually can be traced to a fitting or some pipingthat is made of "white" metal For years, dairy plants and equipment have beenmade entirely of stainless steel to avoid the development of this defect Oxidation

of the phospholipids that were originally in the fat globule membrane is blamed forthe majority of the flavor Two oxidative products, 2-octenal and 2-nonenal, havethis characteristic flavor at <1 ppm.61

Preparation of Training Samples The flavor can be generated by soaking clean

pennies in milk until the flavor intensity reaches the desired level Another method

is to prepare a 1% stock solution of CuSO4 and add the following amounts to 600

ml of milk: 0.75 ml for slight, 1.2 ml for definite, and 1.8 ml for pronounced Thesesamples are held refrigerated for 1 to 2 days before use.5

Oxidized (light-Induced)

Description Synonymous descriptive terms that have been used for this flavor are

burnt, burnt protein, burnt feathers, cabbagey, and medicinal Some synonymousterms designating cause are light-activated and sunlight flavor

Cause Two reactions are involved in the development of this flavor which

devel-ops when milk is exposed to sunlight or fluorescent lights One is produced by lipidoxidation as described for metallic oxidized flavor, and the other by amino aciddegradation involving riboflavin It is proposed that methionine is degraded to3-methylthiopropanal (methional) by a Strecker degradationlike reaction yieldingammonia and carbon dioxide.36'62 Methional has an odor similar to that of light-exposed milk Without riboflavin methional does not develop.36

Preparation of Training Samples Milk with the light-induced oxidized flavor can

be prepared by exposing milk in clear or translucent containers to bright directsunlight for 8 to 15 min The shorter times will produce slight levels of the defectand the longer time will give definite and pronounced levels.5 Similarly the flavorcan be produced by exposing milk to bright fluorescent light for 2 to 8 h Overnightexposure next to a 40-watt fluorescent light will produce pronounced flavor Lessintense samples can be prepared by diluting strongly flavored samples

Rancid

Description There are several characteristics of rancid off-flavor There is a

char-acteristic odor derived from volatile fatty acids that have been hydrolyzed from thefat Immediately after putting the sample in the mouth, the objectionable flavor maynot be apparent but as the sample reaches the back of the mouth, soapy, bitter, andpossibly unclean flavors are perceived The soapy and bitter notes reside long afterthe sample is expectorated A high percentage of prospective judges do not detect

or have a high threshold for the soapy and bitter notes.5

Cause Rancid flavor is usually caused by disrupting the milk fat globule while

active lipase is present The lipase enzyme, which catalyzes the deesterification ofthe fatty acids from the glycerol, is able to get to its substrate when the fat globulemembrane is disturbed This happens when raw milk is held static in a runningcentrifugal pump, when raw milk is homogenized before it is pasteurized, or whenraw milk is inadvertently mixed with homogenized milk It may also occur whenmicroorganisms, particularly psychrotrophs, produce and release Upases into ho-mogenized milk.5

Preparation of Training Samples Rancid milk can be prepared by adding equal

quantities of raw milk to freshly pasteurized and homogenized milk and holding

several hours cold while the flavor develops Bodyfelt suggests mixing 100 ml ofraw milk with 100 ml of pasteurized and homogenized milk in a Waring blender or

a similar mixer for 2 min, then making it up to 600 ml with pasteurized and mogenized milk He suggests making it up 2 to 3 days ahead and holding cold whilethe flavor develops In both cases, it is important to heat the milk to 700C for 5 to

ho-10 min and cool after the flavor has developed.5

Salty

Description The descriptive term "salty" is commonly known and a good term

to describe this flavor It is perceived quickly on placing the sample in the mouth

No aroma or odor accompanies the salty flavor It lends a cleansing feeling to themouth.5 The author perceives the salty sensation as "warm" and lacking refreshingcharacter

Cause Cows in the advanced stages of lactation and cows that have clinical stages

of mastitis often have high salt content in their milk and a salty flavor Comingledmilk seldom has an abnormal salt level nor a salty taste

Preparation of Training Samples Add a pinch of sodium chloride at a time to

pasteurized and homogenized milk while stirring to dissolve the salt until it is at thedesired strength

Unclean

Description Milk with an "unclean" flavor is readily noted when the sample

enters the mouth The flavor and odor are offensive, suggesting extreme staleness,mustiness, putrid, "dirty sock," or spoiled The flavor fails to clean up after themilk is expectorated

Cause This flavor develops in milk when psychotropic bacteria are allowed to

grow to high numbers in milk and particularly when held at temperatures above7.2°C The presence of psychrotrophs is usually due to poor on-farm sanitation Highnumbers are generally due to poor bulk tank cooling

Preparation of Training Samples To find ' 'unclean'' flavored milk, examine

sev-eral samples of milk that are beyond their pull date If the flavor is not found, incubatethem for 4 to 12 h at room temperature and reexamine them When an exemplarysample is found, it may be maintained in the refrigerator and used as an inoculumfor production of future training samples.5

3.4.2 Cottage Cheese

3.4.2./ Introduction

Cottage cheese is a curd that is formed by the acid coagulation of pasteurized skimmilk The acid may be formed by lactic acid bacteria that are added to the milkwhich consume lactose and convert it to lactic acid In one successful method, part

of the acid is added to the milk as acid and the rest is added as an acid anhydridewhich slowly converts to acid and drops the pH of the quiet skim milk to the isoe-lectric pH where the curd forms.64 The curd is cut into cubes, cooked to expel thewhey and firm the curd, washed to cool the curd and remove lactose, then saltedand creamed The cream contains enough fat to bring the final fat content to the

desired level which is commonly 2% or 4% It is sometimes cultured with lactic

acid fermenting and flavor producing bacteria to add flavor and extend shelf life.Variations on the process will produce various curd sizes or a curd mass called''baker's" cheese These products are held below 40C throughout distribution andconsumed within 2 to 3 weeks.5

Good creamed cottage cheese should have a clean, slightly acidic flavor with aslight cultured or "diacetyl" flavor It should be slightly salty sufficient to give abalanced flavor The body should have a meaty consistency without being too firm

or rubbery As the product is masticated, the texture should be smooth The curdparticles should appear fairly uniform in size and shape without shattered curd Thecream should adhere to the curd particles and give moderate but not excessive gloss

or sheen

A listing of defects that can be found in cottage cheese and the resulting scoreranges is shown in Table 3.5 The ADSA contest score card is shown in Figure 3.15and the Collegiate Contest Scorecard is shown in Figure 3.16

3.4.2.2 Flavor Defects

Bitter

Description Bitter is a taste sensation with no associated aroma It is detected at

the base of the tongue The reaction time is fairly slow so it is most strongly sensedafter the cottage cheese is expectorated The intensity builds and it is hard to rinseaway and refresh the tongue

Cause Cottage cheese that is stored at temperatures at or slightly above 4°C for

several days will become bitter when psychrotrophic organisms are present Underthose conditions they will grow to large populations and release proteases Certainweeds consumed by the cow will also impart bitterness to cottage cheese made fromthe milk

Preparation of Samples for Training Solutions of 1% quinine sulfate may be

added to creamed cottage cheese Add 2 ml/lb for a slight and 4 for definite.5

Cooked

Description A sulfurous aroma is detected as the product is smelled and may be

sensed soon after the sample is placed in the mouth The flavor is usually considered

to be pleasant The detection of a cooked egg white smell is characteristic of thisdefect

Source: American Dairy Science Association, 1990.

a "No criticisms" is assigned a score of 10 for flavor and 5 for body and appearance Normal range is 1-10 for flavor and 1-5 for body and appearance for salable product.

b An assigned score of 0 (zero) is indicative of unsalable product.

Cause This flavor can originate from high heat treatment of the skim milk before

cottage cheese is made for the creaming mixture that is added to the curd

Preparation of Samples for Training Wash the cream from cottage cheese curd

and replace it with half and half that has been heated sufficiently to 8O0C Salt curdand cream to taste

Table 3.5 THE ASDA SCORING GUIDE FOR SENSORY DEFECTS OF

CREAMED COTTAGE CHEESE

9 7 9 9 5 9 7 9 9 9 6 5 5 5 4 6 4

4 3 4 4 3 4

4 4 4 4 4 2

Definite

7 5 7 7 3 8 4 8 7 5 4 3 3 3 2 3 1

2 2 2 3 2 3

2 2 3 2 3

0 b

Pronounced

5 1 6 5 1 7 1 7 6 1 1 1 1 1 1 1 1

1 1 1 2 1 2

1 1 2 1 2 0

Figure 3.15 The ADSA contest score card for the sensory evaluation of cottage cheese.

(Reproduced from ref 5, with permission of the ADSA, Champaign, IL.)

Final grade Rank

Source: American Dairy Science Association (1987)

CONTEST COTTAGE CHEESE SCORE CARD

A.D.S.A Contestant No:

Grade

Score Criticism Acid (high)

COTTAGE CHEESE

NCS Tnra-Optic* MP30-7363S-321 A2400SAMPLE NUMBER

MARKING INSTRUCTIONS

IMPROPER

MARKS PROPERMARK

ERASE CHANGES CLEANLY ANO

Figure 3.16 Collegiate contest cottage cheese score card (Reproduced from ref 5, with

permission of the ADSA, Champaign, EL.)

VM NO: TMNCIl <S*tVf

CONTESTANT NO DAUPR

Description Diacetyl is a pleasant and desirable ' 'buttery" flavor in cottage cheese

and cultured products This description is for situations where the flavor overpowersacidity and other flavor and aroma notes

Cause This results when Lactococcus lactis ssp lactis var diacetylactis or conostoc sp has grown better or faster than the lactic culture so that excessive flavor

Leu-and aroma components have been produced

Preparation of Samples for Training Slight or definite cottage cheese can be

simulated by adding 0.1 or 0.2 ml of food grade diacetyl to 400 g of creamed cottagecheese.5 A stock solution of diacetyl in milk can be made to make measurementeasier

Feed

Description Feed flavor in cottage cheese is a result of feed flavor in the milk

from which it is made or the milk from which the creaming solution was made A

"feed" flavor is aromatic and sometimes pleasant After the cottage cheese is pectorated a mild aftertaste of "cleanliness" can be present that disappears ratherquickly, leaving the mouth free of off-flavors Feed flavor varies with the type offeed consumed The odor is characteristic of the feed.5

ex-Cause High-volume roughage feed within 3 h of milking impart aromas to the

milk Silage, some hays, and brewery waste are particularly notable for this Achange of feed from dry hay to fresh green pasture often initiates a strong feed flavor

in the milk Almost all feed flavors disappear if 3 h is allowed to pass betweenconsumption and milking.5

Preparation of Samples for Training Half and half can be treated to have a feed

flavor as described in the section on milk and cream The treated cream can be added

to creamed cottage cheese or to washed curd A little salt may be needed to give atypical salt flavor level.1

Fermented/Fruity

Description A "whiff" of a freshly opened package of cottage cheese with this

defect will be suggestive of pineapple, apples, bananas, or strawberries The tastewill confirm those qualities but coming on late may be an unpleasant, lingeringaftertaste

Cause Some psychrotrophic bacteria produce these characteristic aromatic

com-pounds The package will be near its sell-by date or will have been stored at slightlyelevated temperatures

Preparation of Samples for Training Addition of 1 Vi tsp of banana or pineapple

yogurt to 400 g of cottage cheese will simulate fermented/fruity flavor Addition of

1 to 11 A ml of 1% aqueous solution of food grade ethyl hexanoate to 400 g of cheese

will give slight to definite levels of this flavor

Description The absence of characteristic flavor and aroma is called "flat." The

absence of culture or diacetyl flavor and absence of salt gives that impression

Cause Insufficient flavor producing culture in the cream and insufficient salt will

give this flavor The early stages of oxidized flavor may tend to give a flat taste andaroma The delayed flavor perception may give the impression of a metallic flavor.5

Preparation of Samples for Training The flat flavor may be simulated by washing

the curd and replacing the cream with half and half Salt may be added but less thanenough to give the optimum saltiness

Foreign (Chemical, Medicinal)

Description A foreign off-flavor is one that is entirely unlike any off-flavor that

might be anticipated to develop in cottage cheese

Cause Most of these atypical flavors are caused by cleaning compounds, chlorine,

iodine, or phenol Any one of many compounds that are inadvertently added toproduct or whose fumes are absorbed by product may be responsible for the flavor

Preparation of Samples for Training Foreign flavor caused by sanitizer can be

produced by adding 1 A ml of a 5% sodium hyperchloride solution to 300 ml of good

half and half.5 That cream could be lightly salted to taste and used to cream goodquality washed cottage cheese curd In the same manner, traces of other nontoxicchemical cleaners and sanitizers could be used to taint cream which in turn will taintcottage cheese

High Acid (Sour)

Description Acid is a normal component of good cottage cheese flavor It is a

clean and sharp sensation that generally cleans up well and leaves no aftertaste.When it gets high enough that the flavor predominates over other natural components

of the flavor and covers the desirable flavors, it should be criticized

Cause The culture organism can slowly work on remaining lactose in the curd

until it is gone High moisture facilitates this acid production If the curd is ciently washed, then lactose will be present in the curd and this defect will develop

insuffi-Preparation of Samples for Training For a slight high acid defect, add 15 to

20 ml of cultured skim milk to 385 g of cottage cheese For a definite acid flavorintensity use 30 to 40 ml of cultured.skim milk in 365 g of creamed cheese

High Salt

Description The "high salt" flavor is characterized by a sharp, biting sensation.

The reaction and adaptation time are both short The initial piercing sensation sides and it is replaced by copious flow of saliva

sub-Cause High salt is a formulation error resulting from addition of excessive salt to

the creaming mixture or the curd or both The proper amount is 0.6% to 1.0%

Preparation of Samples for Training Salty cottage cheese can be made by adding

an additional Vi to 1% additional salt to properly salted, good quality creamed cottage

cheese Stir and allow to dissolve

Lacks Fine Flavor (Acetaldehyde)

Description This is a "green" or "green apple" or plain yogurt flavor atypical

of the mild diacetyl or buttery flavor that is characteristic of cottage cheese

Cause An improper lactic culture has been used to make the cream dressing or a

contaminating lactic culture has grown up that produced a lot of acetaldehyde gurt has a characteristic acetaldehyde flavor

Yo-Preparation of Samples for Training Cottage cheese that has this defect can be

made by adding a tsp of plain yogurt to 400 g of cottage cheese.5

Lacks Freshness (Stale or Storage)

Description This is a group of closely related off-flavors All are related to the

age of the product Stale is a more obvious, more intense version of lacks freshness.Lacks freshness just lacks the refreshing fresh flavor of recently made product Stor-age flavor is the changing of character due to absorption of flavors from the productsand materials stored around it

Cause Lacks freshness and stale defects are caused by the occurrence of

micro-biological and chemical changes resulting in deterioration of typical flavor This isexpected to occur to even the best product near the end of its 2- to 3-week shelf life.Occasionally this will begin prematurely due to contamination of the product orstorage at elevated temperatures The storage flavor is sometimes called absorbedflavor It is due to absorbed flavors of products that are stored in the same refriger-ation unit

Preparation of Samples for Training Low-fat cottage cheese may demonstrate

this defect One could also obtain cottage cheese samples that are near their pull dateand screen them to select samples that demonstrate the lacks freshness or stale defect

Malty

Description This flavor resembles malted milk or the flavor of Grape Nuts cereal.

A sourness may accompany the malty flavor The malting process of steeping barleyand allowing it to start to sprout causes this flavor to develop It generally has aquick reaction time and the aftertaste is not prolonged

Cause The bacteria Streptococcus lactis spp lactis var maltigenes produces that

defect in milk if it is able to grow

Preparation of Samples for Training Half and half or milk may be soaked in

Grape Nuts for 30 min and then filtered through a paper towel The filtrate is added

to and stirred into good flavored cottage cheese Sufficient is added to give the level

of intensity desired.66

Musty

Description This is a serious but seldom encountered defect that resembles the

aroma of a damp, poorly ventilated cellar

Cause This defect is due to the growth of a variety of microbial contaminants

including molds The curd may have become contaminated with Pseudomonas

tae-trolens which are psychrotrophic bacteria Poor plant sanitation is responsible for

allowing them into the product and marginal cooling temperatures are responsiblefor allowing their outgrowth.5

Training No method is suggested in the literature for preparation of samples.

Exemplary samples may be found among survey samples that have been held beyondtheir pull date or held at slightly elevated temperatures

Oxidized, Metallic Oxidized, Sunlight Oxidized

Description These three flavors are grouped together because they are thought to

be chemically related.' 'Metallic'' has a slight astringent character and a ' 'rusty nail''like taste "Oxidized" has a flavor similar to wet cardboard or paper "Sunlight"flavor is described as burnt, burnt protein, burnt feathers, cabbagey, and medicinal

Cause AU three flavors are thought to be due to milk fat autoxidation in the cream

used to produce the cottage cheese cream It can be catalyzed by traces of copper orcorrodible metal "Sunlight" flavor also is caused by exposure to sunlight or flu-orescent lights which causes an amino acid degradation involving riboflavin Meth-ional produced in the reaction may cause the flavor.5

Preparation of samples For "metallic" flavor add 3 to 3 ml of 1% aqueous

CuSO4-5H2O solution to 5 ml of milk or half and half which in turn is added to

400 g of creamed cottage cheese Allow 24 h for the flavor to develop A sunlightoxidized flavor can be developed by exposing milk or half and half to bright flu-orescent light for 6 h and then adding that to the creamed cottage cheese

Rancid

Description "Rancidity" in cottage cheese as in milk may be described as an

astringent, puckery feeling at the base of the tongue and throat A bitter and soapyaftertaste may be associated with it There is a slow response time to this flavor.After expectoration it is difficult to clean the flavor out of the mouth

Cause This flavor is due to enzymatic action of lipase on milk fat Ester bonds

are broken, leaving free fatty acids and mono- and diglycerides The shorter freefatty acids, particularly butyric, are flavorful Mid-length fatty acids taste soapy Raw

milk contains lipase and some psychrotrophs produce lipase Conditions are idealfor lipolytic action when these enzymes are present and when the fat is disturbedand new interface is produced Inadvertent mixing of raw and freshly homogenizedmilk is such a case Homogenized milk in which psychrotrophic organisms havegrown to great numbers is another If the cottage cheese cream has been subjected

to those conditions, rancidity will probably occur.5

Preparation of Samples for Training Add rancid milk, prepared according to the

directions in the section on milk, to the creamed cottage cheese mixture Be sure therancid milk has been laboratory pasteurized Try 10 to 15 ml in 400 g of creamedcottage cheese

Unclean

Description The terms "dirty" and "dirty sock" have been used to describe this

flavor The flavor of limburger cheese has been used to simulate it An "unclean"flavor is readily noted when the sample enters the mouth The flavor and odor areoffensive suggesting extreme staleness, mustiness, putrid, or spoiled The flavor fails

to clean up after the cottage cheese is expectorated

Cause This flavor develops in cottage cheese when psychrotrophic bacteria are

allowed to grow to high numbers in milk and particularly when held at temperaturesabove 7.2°C The presence of the psychrotrophs is usually due to poor on-farmsanitation and the high numbers are generally due to poor bulk tank cooling.5

Preparation of Training Samples To obtain product with this defect, screen

sev-eral old cottage cheese samples for unclean flavor If none are unclean, subject them

to 4 to 12 h at room temperature, then rescreen the samples looking for this defect

Yeasty (Vinegarlike)

Description The "yeasty" and "earthy" flavor and aroma reminiscent of rising

bread dough is a good demonstration of the "yeasty" flavor It is often associatedwith an acetic acid or "vinegar" flavor

Cause Growth of yeast is usually responsible for this flavor but it may be due to

bacterial fermentation Certain kinds of psychrotrophic bacteria can be responsiblefor this objectionable off-flavor It is due to poor sanitation and lack of temperaturecontrol.67-68

Preparation of Samples for Training High-quality half and half could be

pur-posely inoculated with yeast and sugar and allowed to ferment for a few hours atroom temperature until the flavor begins to develop It could be lightly salted andused to cream cottage cheese to give it this defect This flavor and aroma can belearned by smelling and tasting yeast leavened bread dough as it is rising

3.4.2.3 Body and Texture Defects

Description and probable causes for body and texture defects are listed here aration of samples to simulate the defects is extremely difficult It is recommended

Prep-that a number of commercial samples be surveyed There will likely be productreadily available that exemplifies the body and texture defects.

Rrm/Rubbery

Description Curd that is too firm will be overly resistant to deformation between

the roof of the mouth and the tongue Resistance to mastication will also be noticed

Cause Firm curd may be due to use of too much rennet, curd cooking temperatures

that are too high, cooking the curd for too long, or pH too high at the time of setting

or cutting too soon

Gelatinous

Description Sticky or ' 'jellylike'' translucent curd is indicative of this defect The

curd may resemble tapioca pudding A bitter flavor may also be present

Cause This defect is usually due to growth of psychrotrophic bacteria in the

cot-tage cheese The product is often unpalatable and unsalable An attempt to make acottage cheese product with rennet without sufficient acid will result in gelatinous,translucent curd.5

Mealy/Grainy

Description This very common defect can be detected by masticating the curd and

then pressing the curd against the roof of the mouth with the tongue and noticingthe presence of gritty or cornmeallike sensation Another way to detect this defect

is to knead washed curd and smear it between the fingers The kneaded curd should

be silky smooth A rough gritty mass is indicative of this defect.5

Cause This defect is caused by overdeveloping the acid during curd formation or

too low a moisture level in the curd It can also be caused by nonuniform cutting ofthe curd, uneven heating during cooking, cooking too fast, inadequate agitation dur-ing cooking, or allowing portions of the curd to come in contact with hot surfacesduring cooking.5

Overstabilized (Slick)

Description Individual curd particles will be surrounded by a thick, pasty, slick

coating

Cause The use of too much stabilizer in the cottage cheese dressing is the cause

of this defect Processors will often thicken the dressing excessively in an attempt

to minimize free cream or free whey Reduction in the amount of stabilizer in thecream will usually overcome this defect

Description Other descriptors for this defect are sticky and doughy This is closely

associated with and considered to be the advanced stages of soft and weak curd(discussed next) The curd particles tend to stick together in clumps.5

Cause See the causes of weak/soft curd(next).

Weak/Soft (Mushy)

Description Weak and soft curd is high in moisture The curd offers too little

resistance to deformation when pressed between the tongue and the roof of themouth Rather than the desired meaty texture, the curd has almost no body andreduces to a liquid on minimal mastication

Cause Conditions that encourage excessive water to be retained in the curd thereby

giving a weak curd are excessively high pasteurization temperatures of the skim milkwhich denatures the whey protein and predisposes them to bind more water, cuttingthe curd too late after the curd is excessively firm and the pH is too low therebyhindering expulsion of water during cooking, curd cooking temperatures too low,and overdressing the curd.5

3.4.2.4 Appearance and Color Defects

Free Cream

Description When creamed cottage cheese is placed on a plate in a mound, as

with an ice cream scoop, the cream should cling to the curd with minimal creamrunning free at the base of the mound of curd Excessive cream flowing out on theplate is evidence of this defect

Cause Conditions that can cause the free cream defect are excessively firm curd

that does not absorb cream, insufficient washing of the curd after cooking, cuttingthe curd while the pH is too high thereby producing firm nonadsorbing curd, andtoo rapid a temperature rise during cooking causing the surface of the curd to resistthe adsorption of cream.5

Preparation of Samples for Training Add half and half or whole milk to creamed

cottage cheese until the amount and viscosity of the cream is sufficient to give azone of free cream around a dollop of cottage cheese

Free Whey

Description No clear solution should be evident at the edges of the cream at the

base of a dollop of cottage cheese Presence of a clear solution is evidence of thisdefect and that destabilization of the cream has occurred

Cause Free whey can be caused by the following conditions: undercooked curd

that is retaining excessive amounts of whey, insufficient washing of the curd such

that excessive whey is still present in the curd, and cutting the curd at too high a

pH, making it unable to adsorb liquid.5

Preparation of Samples for Training Add sufficient whey from wheyed off

but-termilk, yogurt, or even tap water to cottage cheese so that clear fluid appears at theedge of the cream when a dollop of the product is placed on a plate

Lacks Cream

Description When insufficient cottage cheese cream is added to the curd, it will

appear dry and no cream at all will run to the bottom of a mound or scoop of cottagecheese

Cause This problem is generally caused simply by under-creaming It is often

done purposely for food service customers to avoid any free cream and to facilitate

a mound of cottage cheese that does not flow or flatten

Preparation of Samples for Training This defect may be staged by obtaining

some uncreamed curd and blending it with ideal product to give the appropriateappearance Dry curd may be obtained by rinsing cottage cheese curd free of creamwith warm water and then draining off the water

Matted

Description Ideally the curd particles in cottage cheese should be individual Curd

exhibiting the matted defect will have curds tightly stuck together into large clumps

Cause Conditions that will cause matted curd are cutting of the curd at too high

a pH so that the curd will be sticky during the initial stages of cooking, insufficientagitation during the first stages of cooking so that curd particles are allowed to matt,

or cooking the curd too rapidly so that high moisture curd will become sticky andtend to clump.5

Preparation of Samples for Training This defect is so common that finding some

matted curd will be quite easy Matted curd can be ' 'planted'' on a dollop of creamedcottage cheese to demonstrate this defect

Shattered Curd

Description Ideal cottage cheese will have curd particles of uniform size with no

fine particles or "dust." These curd particles can be observed on the creamed surface

of the curd Usually this defect is not called unless at least four or more curd dustparticles are present on each curd particle They can also be seen on the back of aspoon used to sample cottage cheese.5

Cause Shattering of curd to cause these fine particles can be caused by the

fol-lowing conditions: excessive heat treatment of skim milk causing the curd to befragile, cutting at too low a pH when the curd mass has set to some extent making

it difficult to cut without shattering, low-solids milk producing fragile curd, overly

severe agitation, excessive amounts of coagulator use, and rough handling of curdduring draining, creaming, pumping, and packaging.

Preparation of Samples for Training This defect is also common Examples of

this problem will probably be easy to find in commercial cottage cheese The moredifficult task will be to find a sample that is free of this defect Such a sample could

be made by washing curd free of cream on a sieve that allows the passage of curddust, then recreaming with half and half

3.4.3 Butter

3.4.3.1 Introduction

Butter is made by agitating chilled cream to first form granules and then a buttermass The butter mass is drained of serum (buttermilk) and it may be washed Themass is worked to reduce the size of the water droplets, and to disperse and dissolvesalt Butter may be made in a churn but most is made in continuous butter makersthat take in a steady stream of cream, perform all the operations, and produce asteady stream of butter and buttermilk

As defined in the Code of Federal Regulation, butter contains no less than 80%milk fat and is made from pasteurized cream.20 The majority of the butter marketed

in the United States is sweet cream butter made from cream with a titratable acidity

of 0.20% or less If acid has developed in the cream to higher acidities, then theproduct is sour cream butter Cultured butter is made by adding lactic cultures thatproduce aromatic butter flavored compounds to the cream just before churning Salt

is generally added to butter Lightly salted butter contains about 1.5% salt.5 A ber of spreads emulate butter Margarine, butter-margarine blends, and reduced fatspreads are currently available Their sensory properties vary widely and, althoughtheir defects are not treated here, they should be free of off-flavors and perform asintended Butter is the standard for these other spreads and the list of possible defectsthat apply to butter can occur in them

num-Butter is sampled with a curved bladed double-edged tool known as a trier that

is inserted into the block of butter, rotated 180°, and removed It extracts a cylinder

of butter for examination The butter on the trier is passed slowly under the nosewhile inhaling The aroma is noted The color uniformity is next evaluated Thejudge then examines the body and texture by pressing the ball of the thumb againstthe sides of the butter cylinder until it breaks The smoothness of the break is noted

as is the presence or absence of beads of water and the clarity of any water Thejudge then breaks off a piece of butter from the end of the plug, usually with aspatula, and places it into the mouth The sample is chewed while it melts in themouth As it is melting, the presence of grit or undissolved salt is noted between theteeth by biting down It may be observed between the tongue and the roof of themouth The melted sample is moved around in the mouth while noting flavors andaromas The sample is then expectorated The judge then notices if any aftertaste oroff flavor persists The trier is then cleaned with a soft cloth or paper towel

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severe agitation, excessive amounts of coagulator use, and rough handling of curdduring draining, creaming, pumping, and packaging.

Preparation of Samples for Training This defect is also common Examples of

this problem will probably be easy to find in commercial cottage cheese The moredifficult task will be to find a sample that is free of this defect Such a sample could

be made by washing curd free of cream on a sieve that allows the passage of curddust, then recreaming with half and half

3.4.3 Butter

3.4.3.1 Introduction

Butter is made by agitating chilled cream to first form granules and then a buttermass The butter mass is drained of serum (buttermilk) and it may be washed Themass is worked to reduce the size of the water droplets, and to disperse and dissolvesalt Butter may be made in a churn but most is made in continuous butter makersthat take in a steady stream of cream, perform all the operations, and produce asteady stream of butter and buttermilk

As defined in the Code of Federal Regulation, butter contains no less than 80%milk fat and is made from pasteurized cream.20 The majority of the butter marketed

in the United States is sweet cream butter made from cream with a titratable acidity

of 0.20% or less If acid has developed in the cream to higher acidities, then theproduct is sour cream butter Cultured butter is made by adding lactic cultures thatproduce aromatic butter flavored compounds to the cream just before churning Salt

is generally added to butter Lightly salted butter contains about 1.5% salt.5 A ber of spreads emulate butter Margarine, butter-margarine blends, and reduced fatspreads are currently available Their sensory properties vary widely and, althoughtheir defects are not treated here, they should be free of off-flavors and perform asintended Butter is the standard for these other spreads and the list of possible defectsthat apply to butter can occur in them

num-Butter is sampled with a curved bladed double-edged tool known as a trier that

is inserted into the block of butter, rotated 180°, and removed It extracts a cylinder

of butter for examination The butter on the trier is passed slowly under the nosewhile inhaling The aroma is noted The color uniformity is next evaluated Thejudge then examines the body and texture by pressing the ball of the thumb againstthe sides of the butter cylinder until it breaks The smoothness of the break is noted

as is the presence or absence of beads of water and the clarity of any water Thejudge then breaks off a piece of butter from the end of the plug, usually with aspatula, and places it into the mouth The sample is chewed while it melts in themouth As it is melting, the presence of grit or undissolved salt is noted between theteeth by biting down It may be observed between the tongue and the roof of themouth The melted sample is moved around in the mouth while noting flavors andaromas The sample is then expectorated The judge then notices if any aftertaste oroff flavor persists The trier is then cleaned with a soft cloth or paper towel

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Table 3.6 U.S GRADE CLASSIFICATION OF

BUTTER ACCORDING TO FLAVOR CHARACTERISTICS 5

Identified Flavors

by Grading 3

Feed Cooked Acid Aged Bitter Coarse Flat Smothered Storage Malty Musty Neutralizer Scorched Utensil Weed Whey Old cream

B P D D D

D D S S S S S S S D

Source: Code of Federal Regulations (1987).

3 When more than one flavor is discernible the lowest classification establishes the grade b U.S Butter Grade as determined by offi- cial USDA grading standards c Defect intensity: S = slight;

D = definite; P = pronounced.

The USDA grades much of the butter produced in the United States Before 1977,butter scoring was on a 100-point scale Now only the letter designation is used Thepoint system is still occasionally referenced Grade AA butter scored 93 or morepoints, A grade required 92 points, and B grade required a minimum of 90 points.Table 3.6 shows flavor grades that are assigned based on flavors present and theirintensity The only flavor defects allowed in Grade AA butter are slight feed andcooked Any other flavors result in downgrading Table 3.7 shows how many de-rating points are assigned for body, color, and salt defects Derating up to 1 A total

points does not reduce the grade below the assigned flavor grade Each 1 A derated

point beyond that reduces the butter one additional grade.20

The American Dairy Science Association uses a 25-point system with 10 pointsfor flavor, 5 for body and texture, 5 for color and appearance, 3 for salt, and 2 forthe package In collegiate contests only the flavor is judged The ADSA Flavorscoring guide is shown in Table 3.8 and a body and texture guide is shown in Table3.9 A sensory scorecard using a 25-point system is shown in Figure 3.17 and theCollegiate Contest Butter Score Card is shown in Figure 3.18

Table 3.7 CHARACTERISTICS AND DISRATINGS

FOR BODY, COLOR, AND SALT FOR U.S BUTTER GRADES 5

Butter Characteristics Body

Crumbly Gummy Leaky Mealy or grainy Short

Weak Sticky Ragged boring Color

Wavy Mottled Streaked Color specks Salt

Sharp Gritty

Disratings b

S

0.5 0.5 0.5 0.5 0.5 0.5 0.5 1

0.5 1 1 1

0.5 1

D

1 1 1 1 1 1 1 2

1 2 2 2

1 2

P

2

a U.S Butter Grade as determined by official USDA grading standards.

b Defense intensity: S = slight; D = definite; P = pronounced.

3.4.3.2 Flavor Defects

Acid

Description Acid and sour are synonymous and refer to a sharp taste on the tip of

the tongue as well as an associated "sour" aroma The sour taste is quickly detected

as the sample is placed in the mouth The acid flavor cleans up quickly after thesample is expectorated, leaving no aftertaste

Cause Acid tasting butter usually is a result of churning overripe or acid cream.

It may be caused by leaving too much ripened buttermilk in the butter after churning

Preparation of Samples for Training Acid butter or butter with any of the defects

may be obtained by surveying product on the market or by asking processors to be

on the watch for exemplary product It can be made by culturing cream with

Strep-tococcus lactis ssp lactis organisms until it is overly ripe and then churning the

cream Acid butter can be kneaded together with good butter to obtain product withthe desired level of acid

Table 3.8 THE ADSA SCORING GUIDE FOR SENSORY

DEFECT OF BUTTER (SUGGESTED FLAVOR SCORES FOR DESIGNATED DEFECT INTENSITIES) 5

6 6 3 8 9 9 3 4 5 5 6 4 4 7 6 5 6 4

Definite 5 5 2 7 8 8 2 3 4 4 5 3 2 5 5 4 5 3

Pronounced 4 4 1 6 6 7 1 1 2 3 4 2 1 3 4 3 3 2

Source: American Dairy Association, 1990

a "No criticisms" is assigned a score of 10 Normal range is 1-10 for salable product.

Bitter

Description Bitterness is recognized by the sense of taste alone Once the butter

sample has melted in the mouth, it can be best detected when the sample is moved

to the back center of the tongue where the taste buds are most sensitive to bitter

Cause Bitterness in butter may be caused by action of certain microorganisms or

enzymes, consumption of certain feeds or weeds by the cow, impurities in the saltadded to the butter, and inappropriate use of some neutralizes.5

Preparation of Samples for Training Quinine sulfate has strong, clean, bitter

flavor in very dilute concentrations Addition of 1 to 2 ml or 1% quinine sulfatesolution to a pint of cream before churning will result in bitter butter Alternatively,quinine sulfate solution can be kneaded into butter The level of bitterness can beadjusted by kneading bitter and good butter together in appropriate ratios

Cheesy

Description Cheesy butter resembles cheddar cheese in flavor and aroma The

flavor is noticed immediately after the sample is placed in the mouth It also lingersafter the sample is expectorated Clean up of the flavor is slow

Table 3.9 A SUGGESTED SCORING GUIDE FOR BODY AND TEXTURE

AND COLOR AND APPEARANCE IN BUTTER

Body and texture defect*

3 0 0 3 3 4 0 4

Moderate

3 3 3 3 3 3 3 3

2 0 0 2 2 3 0 3

Definite

2 2 2 2 2 2 2 2

1 0 0 1 1 2 0 2

Strong

1 1 1 1 1 1 1 1

0 0 0 0 0 1 0 1

Pronounced c

d

o e 0

0 0 0 0 0 0 0 0

Reproduced with permission from ref 5.

a "No criticism" is assigned a numerical score o f ' 5 " Normal range is 1 to 5 for a salable product b Highest assignable score for a defect of slight intensity c Highest assignable score for a defect of pronounced intensity However, a sample may be assigned a score of " 0 " (zero) (unsalable product) d a dash (—) indicates that the defect is unlikely to be present at this intensity level c When a product is determined to be unsalable for a given sensory defect, a " 0 " (zero) numerical score is assigned to the sample for the quality attribute(s) in question.

Cause This flavor results when soured cream is held refrigerated and proteolytic

organisms are allowed to grow When this cream is churned, cheesy butter results.Tendency to develop this flavor is related to the curd content of the butter Washingthe butter well as it is being churned is a precaution against cheesy flavor.5

Preparation of Samples for Training Cheesy flavored butter can be made by

adding cheddar cheese flavor to cream prior to churning or by kneading cheese flavorsolution into softened butter It should be tried with a variety of cheese flavors toensure that one will have the desired flavor

Coarse

Description Coarse butter is one that lacks the pleasing, delicate flavor that is

typical of good quality fresh butter It is really employed when the butter lacks thetypical flavor but no other criticism is appropriate It can be considered the earlystages of the "old cream" or "storage" defects but no particular defect has devel-oped, only a flavor that is off ideal

Cause Coarse butter generally results when cream that is a little old and perhaps

slightly acidic is churned The defects are not strong enough to be criticized as oldcream, acid, or storage

Preparation of Samples for Training Blending a little slightly aged cream with

high quality cream and then churning may result in product that will be criticized

as coarse This defect is quite prevalent among the products on the market It shouldnot be hard to find product that has this defect

Feed

Description Feed flavors can usually be detected using the sense of smell, then

verified by tasting They are flavors reminiscent of the feeds eaten by the cow

Cause Feed flavor in product is a result of consumption of feeds within 3 h of

milking Some feeds are particularly potent Fresh clover and alfalfa are potent inthis respect The spring of the year when the cow goes on pasture is a vulnerabletime

Preparation of Samples for Training An alfalfa flavor can be simulated by adding

and holding 2 to 3 g of alfalfa hay to 100 ml of fresh pasteurized and homogenizedmilk for 20 min The milk is then strained through a cheesecloth or a paper toweland used as a stock solution To 575 ml of fresh pasteurized cream add 20 to 35 ml

of this stock milk solution Grass or corn silage can be used to prepare feed flavoredmilks in the same manner The cream is then churned into butter which will have afeed flavor corresponding to the material used.5

Flat

Description When the full characteristic buttery flavor is lacking the flavor is

considered to be flat It is noticed very soon after the sample has been placed in themouth and as the sample melts and is moved around in the mouth It is not to beconfused with a low or unsalted flavor It is possible for the salt to be absent but thediacetyl and volatile acid flavor notes to be sufficiently present Lack of salt doessuppress the butter flavor though

Cause Lack of diacetyl and volatile acids are the cause of flat butter Excessive

washing of butter granules can result in flat tasting butter Consumption of certainfeeds has been blamed for milk fat with a low level of volatile flavors A slightcooked flavor to the cream or culturing the cream are effective ways to give buttersome flavor

Preparation of Samples for Training Flat butter can be prepared by kneading

good quality butter in cool clean water to remove some of the water-soluble flavorcomponents

Garlic/Onion

Description The distinctive odors and flavors characteristic of garlic or onion are

the trademarks of this defect Both are quite odorous and similar in butter that has

BUTTER SCORE CARD