the relationship between cnsumer acceptability and descriptive sensory attributes in cheddar cheese

the relationship between cnsumer acceptability and descriptive sensory attributes in cheddar cheese

IN CHEDDAR CHEESE*

E.L CASPIA1, P.C COGGINS1,2, M.W SCHILLING1, Y YOON1and

C.H WHITE1

1Department of Food Science, Nutrition and Health Promotion

Mississippi State University Mississippi State, MS 39762

Accepted for publication November 8, 2005

ABSTRACT

The relationship between the consumer acceptability of Cheddar cheese and its descriptive sensory attributes was determined using preference mapping and logistic regression for three Cheddar cheeses A trained panel

The overall order of consumer preference (P ⬍ 0.05) for the three cheeses was

9, 7 and 12 months of aging time, respectively The trained panel characterized the 7- and 9-month-old cheeses as having young/undeveloped flavors such

as “cooked,” “buttery” and “creamy” flavors, and had volatiles that were responsible for the creamy flavor in cheeses The 12-month-old cheese was characterized by aged/developed flavors and included volatile compounds responsible for fruity aromas and sulfurous, earthy and free fatty acid flavors External preference mapping revealed six clusters of consumers with varying Cheddar cheese preferences; 74, 95 and 61% of the consumers found 7-, 9-and 12-month-old cheeses to be acceptable, respectively.

INTRODUCTION

The demand for dairy products has significantly increased over the past

* Approved for publication as Journal Article No J-10789 of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State University, CRIS No 501070.

2 Corresponding author: TEL: (662) 325-4002; FAX: (662) 325-8728; EMAIL: pcoggins@ ra.msstate.edu

Journal of Sensory Studies 21 (2006) 112–127 All Rights Reserved.

© 2006, The Author(s) Journal compilation © 2006, Blackwell Publishing

112

2004) Per capita consumption of cheese in the U.S.A accounted for 13.6 kg

in 2003, out of which 4.2 kg consisted of Cheddar cheese (USDA 2004) Consumers have a wide variety of cheese products to choose from, and depending on population segments and regional locations, flavor preferences

of consumers also vary Therefore, understanding the development and varia-tions in taste that occur during the maturation process of Cheddar cheese is an important tool in defining consumers’ expectations of taste Aroma and texture

of Cheddar cheese also change over ripening time, and although taste changes more readily than other sensory attributes, all may be useful in discriminating Cheddar cheese as well as explaining consumer preferences The heteroge-neous nature of milk predisposes its derived products, such as cheese, to a complex biochemical process in which three major catabolic pathways – glycolysis, lipolysis and proteolysis – are involved (McSweeney and Sousa 2000) As a result, new flavor compounds are produced with each reaction Flavor variations are also closely linked to the manufacturing process starting with the quality of the milk, and the aging and maturation conditions

At 6–8 months of age, Cheddar cheese develops most of its flavor, and

a full Cheddar cheese flavor is generally developed after 1 year of ripening The use of a sensory language for Cheddar cheese is important for research and marketing purposes, and although validated flavor lexicons for Cheddar

cheese exist (Drake et al 2001), a variation of references and terms

some-times is needed to best fit with the sensory characteristics of specific Cheddar cheeses

Both logistic regression and preference mapping may be useful in explaining the relationship between consumer acceptability, trained descrip-tive analysis and flavor chemistry Logistic regression is a unique way to link explanatory variables to discrete response ones (Hosmer and Lemeshow 2000) Logistic regression is very similar to multiple linear regression The only major difference in the analyses is the nature of the response variable In multiple linear regression, the response is a continuous variable, while in logistic regression, the response is a categorical/discrete one This analysis has vast applications and is underutilized in sensory experimentation, but it has shown merit in explaining consumer acceptability of tenderness in chicken

breasts (Schilling et al 2003) Such statistical modeling may be useful in

determining the consumer acceptability of Cheddar cheese, and its usefulness

in explaining consumer acceptability should be compared to preference mapping because it is the method most frequently used to relate consumer acceptability data to descriptive sensory attributes The objectives of this study were to determine how descriptive attributes including taste, aroma and tex-tural attributes in commonly consumed Cheddar cheeses as well as volatile compounds present at concentrations greater than 100 ppb relate to consumer acceptability using preference mapping and logistic regression

MATERIALS AND METHODS Cheddar Cheese Sampling

Cheddar cheese (9.1 kg) blocks were ripened for 7, 9 and 12 months and then sampled in triplicate (three replications of each aged Cheddar cheese from three different batches of milk) from the Mississippi State University Dairy Plant After aging, the cheese blocks (9.1 kg) were cut into 0.45-kg ones, waxed, vacuum-sealed and stored at 7C in the dark for 4 months prior to starting the study Each panelist received triplicate samples from each 7-, 9-and 12-month-treatment block (9.1 kg) for each replication

Training of Panelists

Nine panelists (six women and three men) were selected from the Uni-versity based on availability, previous training and liking of cheese The panelists were trained for 30 h using previously identified languages for sensory evaluation of Cheddar cheese (Murray and Delahunty 2000; Drake

et al 2001), and the majority of them had greater than 100 h of training

regarding the evaluation of dairy products Food and chemical references as well as cheese samples were used in the training A 15-point intensity line

sensory attributes was used Some anchors in the scale were generated during the panelists’ training

Sample Preparation

Each 0.45-kg block of Cheddar cheese used for panelists’ training was cut

cheese blocks were prepared 1 h prior to testing, wrapped in aluminum foil and placed on plastic plates (RS6BPY, 125/5 7/8 in., Sweetheart Cup Company, Inc Chicago, IL) The temperature of the cheese was approximately 10C

(Avsar et al 2004) at the time of serving The panelists were provided with

unsalted crackers (Premium, Nabisco, NJ), water (Mountain Spring Water, Blue Ridge, GA) and expectoration cups to cleanse their palate between samples Testing was conducted at the same time every day

References were prepared according to the spectrum intensity scale

values of the four basic tastes or intensity references (Meilgaard et al 1991).

Flavor terms and references were obtained from standards selected to refer-ence terms of Cheddar cheese flavor language (Murray and Delahunty 2000)

and the Cheddar cheese lexicon (Drake et al 2001) Some of the reference

terms, definitions and food references from these lexicons were screened and modified by the panel during the training sessions for suitability with the

cheese analyzed Flavor terms of the Cheddar cheese lexicon consist of 17 terms, some of which were modified such as the case of the terms “diacetyl” and “milkfat,” which were replaced by “buttery” and “creamy,” respectively, as used by Murray and Delahunty (2000) Spectrum references were also used for panelist training for aroma and textural attributes

After the training period, the panel, without access to references, evalu-ated three samples of Cheddar cheese, one for each ripening period for 3 days This analysis was performed in triplicate during three consecutive months The presentation of the sample was the same as for each of the training sessions Each plate had a three-digit random number The panelists were provided with unsalted crackers and ambient temperature spring water (Mountain Spring Water) for cleansing the palate The panelists evaluated the cheese samples in

an odor-free room dedicated to sensory analysis

Consumer Acceptability

Consumer acceptability was evaluated in three consecutive months, each within 2 weeks of the cheese descriptive evaluation by the trained panel The

illumi-nated with white lighting The samples were assigned with three-digit random numbers and served under identical conditions to the trained descriptive testing Consumers ranked the three cheeses in their order of preference, and then evaluated them using a hedonic scale ranging from 1 (“dislike

extremely”) to 9 (“like extremely”) (Meilgaard et al 1991) Each consumer

evaluated each cheese for overall acceptability, overall flavor, aroma, texture and appearance

Instrumental Analysis of Cheddar Cheese

Extraction of Volatile Compounds Samples were prepared first by

removing a 0.2-cm layer from each surface of the cheese to minimize flavor migration The cheese was grated using a manual cheese grater Nineteen grams of sample was then placed in a 40-mL amber glass vial (Supelco, Bellefonte, PA), which was tightly closed Each cap possessed a 1.5-cm-wide hole in the center equipped with Teflon-faced silicone septum

at 60C in a water bath (Isotemp 1016S, Fischer Scientific, Inc., Pittsburgh, PA)

for 40 min (Chin et al 1996) Solid phase microextraction (SPME) was used

to analyze the volatile flavor compounds in the Cheddar cheese treatments A two-phase fiber (carboxen/polydimethylsiloxane, Supelco) was inserted into the vial through the septum, exposed to the headspace and held for 20 min at the same temperature (60C)

Gas Chromatography-Flame Ionization Detector The analyses of the

volatile compounds adsorbed on the fiber were carried out in triplicate for each cheese treatment over three consecutive months using a Varian CP-3800 gas chromatograph (GC) equipped with a flame ionization detector (Varian Analytical Instruments, Walnut Creek, CA) and Star 5.0 Workstation data acquisition software (Palo Alto, CA) The type of column used was a

(J&W Scientific, Folsom, CA) The samples were analyzed under the follow-ing GC conditions: (1) 42-min total run time; (2) 225C injector temperature; (3) 40–250C column temperature at 5C/min ramp rate; and (4) 250C detector temperature To obtain the retention indexes of the different compounds,

program conditions, and volatile compounds were identified using Flavor Net (Acree and Arn 2004)

Statistical Analyses

A randomized complete block design with three replications was used to

Cheddar cheese treatments for flavor, aroma and textural attributes Least significant difference test was used to separate means when differences occurred The descriptive data were further analyzed using principal compo-nent analysis (PCA, SAS 8.1, Cary, NC) (SAS Institute, Inc 1999) to differ-entiate among Cheddar cheese treatments

A randomized complete block design with three replications was used to analyze the effects of three different ripening periods of Cheddar cheese on consumer acceptability Agglomerate hierarchical clustering was performed to cluster consumers together based on their liking of Cheddar cheese Both external preference mapping and logistic regression were conducted on the descriptive attribute data and the consumer acceptability scores to determine the relationship between sensory attributes and consumer preference This analysis was performed on nine products (three treatments replicated thrice to make preference mapping and PCA possible)

RESULTS AND DISCUSSION Descriptive Analysis

Flavor The descriptive flavor attribute intensity means (n= 9) for 7-, 9-and 12-month Cheddar cheeses are listed in Table 1 Taste attributes such as whey, brothy, nutty, cowy, yeasty, earthy and salty were not significantly

different (P⬎ 0.05) among the three ripening periods These results were first based on differences among treatments (yeasty and salty) and then on pane-lists’ treatment interaction (whey, brothy, nutty, cowy and earthy) When the interaction plots among panelists revealed a large amount of variation among panelists for a certain attribute and did not follow the same or similar trend, the data produced led to nonsignificant differences These irregular trends in the interaction among panelists could mean that the panelists did not distinguish differences among treatments or that no perceivable differences existed among the treatments

As found by Young et al (2004), most of the intensities for the different

attributes fall between 0 and 4 on a 15-point line scale The Cheddar cheeses that were ripened for an average of 7 and 9 months had higher intensity scores

undeveloped flavors by Drake et al (2001) such as “cooked,” “buttery”

(diacetyl) and “creamy” (milkfat) (Table 1, Fig 1) The Cheddar cheese that

attributes classified as aged/developed flavors such as “sulfur,” “free fatty

TABLE 1.

DESCRIPTIVE FLAVOR ATTRIBUTE INTENSITY

MEANS (n= 9) FOR THE THREE MATURITY LEVELS

OF CHEDDAR CHEESE*

Cheese flavor terms 7-month 9-month 12-month

Free fatty acid 2.6 b 2.1 b 4.1 a

Means in a row with different superscript letters (a, b and c)

repre-sent significant difference (P⬍ 0.05).

* Intensities scored on a 15-point line scale.

acid,” and “earthy,” “pungent,” “prickle bite,” “bitter” and “sour.” Young et al.

(2004), characterized the flavor attribute terms of 1-, 2- and 4-month-ripened Cheddar cheeses as cooked/milky, whey, diacetyl and milkfat/lactone Cheeses with more than 1 year of ripening were characterized by “sulfur,” “brothy,”

“nutty,” “free fatty acid” and “catty” attribute terms (Young et al 2004) In

comparison with results obtained in this research, flavor attribute terms such as

“brothy” and “nutty” were not significantly different among the three cheeses, and the term “catty” was only used to characterize aroma Bitterness is usually

regarded as a defect in Cheddar cheese (Suriyaphan et al 2001) The sensory

term “fruity” was excluded from the data after the initial statistical analysis of taste attributes (during training) because of a low perceivable intensity of this attribute by the panelists; however, a slight fruity aroma was present in all Cheddar cheese samples (Table 2)

The principal component analysis biplot for flavor (Fig 1) reveals that the 9-month-ripened cheese had a more cooked, buttery and creamy taste than the other cheeses The 12-month-ripened Cheddar cheese was differentiated from the other two cheeses because it possessed the characteristic aged Cheddar cheese tastes, such as “sulfur” and “free fatty acid” flavors This cheese was

Prickle bite Pungent Bitter

Sour Free fatty acid Sulfur Earthy

Umami

Sweet

Buttery Creamy Cooked

Principal component 2 (15%)

Principal component 1 (70%)

9-month

12-month

7-month

FIG 1 PRINCIPAL COMPONENT BIPLOT OF DESCRIPTIVE ANALYSIS FOR FLAVOR ATTRIBUTES OF CHEDDAR CHEESES AGED 7, 9 AND 12 MONTHS

also bitterer, sourer and earthier, and had a more “prickle bite” taste than the 7- and 9-month-aged Cheddar cheeses According to the eigenvalues (percent-age by which variation is explained in the biplot), 70% of the variation is explained by dimension 1, and almost 15% of the variation is explained by dimension 2 This means that taste attributes that are closer to dimension 1 (horizontal) are major determinants of variation in the three maturation levels

of Cheddar cheese It is apparent from the taste data that Cheddar cheeses between 7 and 12 months of aging can be differentiated from each other using descriptive taste attributes

Aroma The results for aroma were similar to those found in flavor.

undeveloped flavors and aged/developed flavors (Table 2) Aroma attributes such as “fruity,” “sulfur,” “free fatty acid” and “pungent” were noticeably higher in the 12-month-ripened cheese The 7- and 9-month-ripened cheeses were clearly characterized by “cooked,” “whey,” “buttery” and “creamy” aromas

During maturation of Cheddar cheese, there is an increase in the ratings

for sulfur aroma (Muir et al 1995) According to Dacremont and Vickers

(1994), the most important compounds for Cheddar cheese aroma are butyric

TABLE 2.

DESCRIPTIVE AROMA ATTRIBUTE INTENSITY

MEANS (n= 9) FOR THE THREE MATURITY LEVELS

OF CHEDDAR CHEESE*

Cheese aroma terms 7-month 9-month 12-month

Free fatty acid 2.1 b 1.7 c 3.2 a

Means in a row with different superscript letters (a, b and c)

repre-sent significant difference (P⬍ 0.05).

* Intensities scored on a 15-point scale.

acid, diacetyl and methional In the aroma attribute terms used in the descrip-tive analysis, these can be described as “free fatty acid,” “buttery” and “sulfur” aromas The principal component analysis biplot for aroma (Fig 2) clearly differentiates the three cheeses Sulfur-containing compounds and free fatty acids are mainly responsible for the aroma in Cheddar cheese and have a much higher content in the oldest cheese

Texture Texture terms with significant differences among treatments

were firmness and slipperiness for mouth evaluation terms, and firmness and slipperiness for hand evaluation terms This reveals that texture may change as

a result of ripening, but is not as helpful at differentiating the evaluated cheeses

as taste and aroma Using texture profile analysis methodology, Creamer and

Olson (1982) and Charalambides et al (1995) found significant differences in

firmness and crumbliness after analyzing cheeses from 1 to 12 months of age

As shown by their results, differences may be able to be measured instrumen-tally for cheeses with ripening periods from 7 to 11 months but were not highly

perceivable by panelists in this experiment According to Pollard et al (2003),

firmness of cheese decreases during maturation because of the breakdown of

Cooked

Creamy Buttery

Sulfur

Fruity

Free fatty acid Pungent

7-month

9-month

12-month

Principal component 2 (3.94%) Principal component 1 (93.06%)

FIG 2 PRINCIPAL COMPONENT BIPLOT OF DESCRIPTIVE ANALYSIS FOR AROMA ATTRIBUTES OF CHEDDAR CHEESES AGED 7, 9 AND 12 MONTHS

the casein matrix in proteolysis and a slight increase in solid fat because of moisture loss

Volatile Compounds

Volatile compounds identified by the SPME method using the GC-flame ionization detector were shown in Table 3 Odorant compounds responsible for fruity aromas identified in the 12-month Cheddar cheese were ethyl butyrate and hexanone Compounds such as acethylthiophene were respon-sible for sulfur flavors found in the 9-month Cheddar cheese Hexanoic and decanoic acids are free fatty acids defined as strong contributors of rancid and sweaty flavors Other compounds identified include isobutyl methoxypyrazine, which contributes to an earthy flavor, and ketones such as nonanone and

hexanone responsible for green, fruity flavors, etc Suriyaphan et al (2001)

confirmed that an “earthy” flavor in cheese was because of 2-isopropyl-3-methoxypyrazine and at much lower odor intensity, this same compound contributed to a “bell pepper-like” note Some of the identified odorants of the 7- and 9-month cheeses were 2-hexenol with a green leaf/wine odor, and some

Ethyl butyrate was only found in the 12-month cheese This compound has an apple odor Manning and Robinson (1973) characterized Cheddar cheese as mainly containing volatile compounds such as hydrogen sulfide, methanethiol and dimethyl sulfide Dimethyl pyrazine was only identified in the 9-month-ripened cheese According to Christensen and Reineccius (1995), other volatile compounds indicative of age in Cheddar cheese are ethyl acetate,

ethyl caproate, 1-octen-3-one, acetic acid, methional, propionic acid, butyric acid, valeric acid, caproic acid, capric acid and lauric acid

Consumer Acceptability

consumer acceptability (Table 4) The 9-month Cheddar cheese received the highest mean score of 7.53 for overall liking, which corresponds to between

“like moderately” and “like very much” in the hedonic scale According to the descriptive analysis performed by the trained panel (Fig 3), this cheese had stronger “cooked,” “creamy” and “buttery” flavors compared with the other cheeses (7- and 12-month) The 12-month-ripened cheese had the lowest mean score of liking of 5.75, which is categorized as between “like slightly” and

“neither like nor dislike” in the 9-point hedonic scale On average, consumers found the 12-month cheese acceptable Bitter flavors were highly perceivable