new topics in food engineering (food science and technology)

C ONTENTS Chapter 1 Tempering, Polymorphism and Fat Crystallization During Industrial Chocolate Manufacture: Regimes, Behaviours and their Effects on Emmanuel Ohene Afoakwa and Alistair

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FOOD SCIENCE AND TECHNOLOGY

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F OOD S CIENCE AND T ECHNOLOGY

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FOOD SCIENCE AND TECHNOLOGY

M ARIANN A C OMEAU

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C ONTENTS

Chapter 1 Tempering, Polymorphism and Fat Crystallization During Industrial

Chocolate Manufacture: Regimes, Behaviours and their Effects on

Emmanuel Ohene Afoakwa and Alistair Paterson

Chapter 2 Non-linear Modeling of Quality of Cooked Ground Beef Patties

Sreekala G Bajwa and Jason K Apple

Chapter 3 Molecular Size Distribution in Long-aged Food Beverages and

Alcoholic Drinks: A Preliminary Inquiry towards Understanding

Pasquale Massimiliano Falcone and Paolo Giudici

Chapter 4 Hyperspectral Waveband Selection for Detection of Almonds

Songyot Nakariyakul

Chapter 5 High Frequency Ultrasonic Techniques Dedicated to Food

D Laux, J Y Ferrandis, V Cereser Camara, H Blasco and M Valente

Chapter 6 Trends in High Pressure Processing of Foods: Food Quality

Shirani Gamlath and Lara Wakeling

Chapter 7 Thermodynamic and Kinetic Criteria to Study the

Cesar I Beristain, Eduardo J Vernon-Carter and Ebner Azuara

Chapter 8 Development of Vacuum Spray Drying System for Probiotics

Yutaka Kitamura and Yukari Yanase

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Contents

vi

Chapter 9 Application of Vacuum Impregnation and Edible Films to Improve

Pau Talens and María José Fabra

Chapter 10 Food Packaging: Innovative Concept and Necessities 249

Kelen Cristina Dos Reis

Chapter 11 Predictive Modelling of Thermal Properties of Foods 261

James K Carson

Chapter 12 Applications of Membrane Contactors in the Food Industry 279

Catherine Charcosset

Chapter 13 Possibilities for Removal of Glucose From Various

K Bélafi-Bakó

Chapter 14 Instant Rice Physicochemical Properties and Eating Quality 301

Prisana Suwannaporn

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P REFACE

In the development of food engineering, one of the many challenges is to employ modern tools and knowledge to develop new products and processes Simultaneously, improving quality, safety, and security remain critical issues in food engineering Additionally, process control and automation regularly appear among the top priorities identified in food engineering This book presents topical research in the study of food engineering, including: ozone technology in the food industry; current trends in drying and dehydration of foods; strategies for extending the shelf-life of foods using antimicrobial edible films; developments

in high-pressure food processing; as well as tempering and polymorphism during chocolate manufacture

Chapter 1 - Tempering, a technique of shearing chocolate mass at controlled temperatures

is used to promote cocoa butter crystallization in a thermodynamically stable polymorphic form During chocolate manufacture, the process is used to obtain the stable form V (or ß2) of cocoa butter having a melting temperature of 32-34 °C, which gives the desired glossy appearance, good snap, contraction and enhanced shelf life characteristics However, the tempering sequences, their behaviour during pre-crystallization, the consequential regimes attained and their effects on product quality characteristics are not very well understood Variations in temper regimes attained during pre-crystallization of chocolates influence their crystallinity, polymorphic status and other physical quality characteristics Over-tempering causes increases in product hardness, stickiness with reduced gloss and darkening of product surfaces Under-tempering induces fat bloom in products with consequential quality defects in structure, texture, melting properties and appearance (colour and surface gloss) Thus, the different temper regimes attained during pre-crystallization result in wide variations in product quality attributes with varied influences on quality In a modern competitive confectionery market, understanding the variables leading to chocolate pre-crystallization during tempering and effects of the regimes attained on the quality of the finished products are vital to assurances in quality and shelf characteristics

Chapter 2 - Chemometric models based on partial least square regression (PLSR) have been successfully used to estimate nutrient content of different raw meat products from spectroscopic measurements Preliminary studies to establish a chemometric model for estimating nutrient concentration of cooked ground beef patties from spectroscopic data indicated that the linear PLSR models are not adequate to represent fat and calories Therefore, this study was conducted to examine two non-linear modeling methods using PLSR and artificial neural networks (ANN) In this study, spectral absorbance in the visible and near infrared (VNIR) region along with data from proximate analysis was utilized to

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Mariann A Comeau viii

develop and validate the two non-linear models for predicting fat, calories, cholesterol and moisture content of cooked ground beef patties When compared to a linear chemometric model based on PLSR, both non-linear models performed significantly better The ANN model exhibited the best performance which was indicated by a validation R2 value of 0.93 and residual predictive deviation (RPD) of 3.3 and 3.4 for fat and calories respectively Both non-linear models resulted in RPD ≥ 3 under validation, indicating that they are acceptable However, the model performance was only fair for cholesterol and moisture content

Chapter 3 - The present study supports the idea that physical- and sensory-related properties of long-aged beverages and alcoholic drinks containing reducing sugars would be described not by an unique value rather as a distribution of values due to the time-dependent increase of molecular heterogeneity in molecular sizes and structure A wide range of beverages and alcoholic drinks obtained after different aging periods at room temperature were fractioned by Size-Exclusion Chromatography (SEC), then the elution profiles were analyzed by using a chemical-groups sensitive detector, i.e an ultraviolet-visible (UV-VIS), coupled to a mass-sensitive detector i.e a differential refractive device (DRI) The analysis

of the probability density function as well as of the cumulative density function allowed comparing the distribution properties over a wide range among the investigated samples This

is because, unlike small molecules, such liquid matrices undergo accumulation of high molecular size biopolymers (melanoidins) throughout the aging period In general, results

proved that all the investigated matrices would be defined as heterogeneous mixtures of chromophore-labeled copolymers, uncolored and brown, highly polydispersed with respect to their molecular size (ranging between 0.2kDa to over 2000kDa) and their chemical structure

In particular, the molecular size distribution of the end-products was attributed to the raw materials used for their production; while, the relative content of the biopolymers is strictly related to the extent of the thermal treatment applied along to the making process (when it is applied) as well as to the length of the storage time at room temperature

Chapter 4 - Detection of concealed damage in almonds is an important production inspection application Internally damaged almonds are not easily distinguished from normal ones by their external appearances, and, when cooked, they taste bitter Prior study showed that using the whole spectrum of hyperspectral data from 700-1400 nm could distinguish internally damaged nuts from normal ones at an error rates as low as 12.4% However, the hyperspectral system is rather slow and cannot achieve an inspection rate of 40 nuts/s required by almond processing plants Thus, a feature selection algorithm is needed to choose only a small subset of useful wavebands from hyperspectral data for use in a real-time multispectral camera In this study, author introduce two novel feature selection techniques; one method is developed to select an optimal subset of individual wavebands, while the other aims to find good sets of band ratios Author thoroughly discuss the advantages and disadvantages of both algorithms Experimental results demonstrate that the author proposed methods give higher classification rates than other state-of-the-art algorithms

Chapter 5 - Usually, viscoleastic properties of materials (complex shear moduli and viscosity) are evaluated with rheometers which can give G’, G’’ for instance, on wide bandwidths thanks to the Time Temperature Superposition principle It is clear that the knowledge of such properties is very interesting on a fundamental point of view because information on material microstructure can be deduced from master curves On a more practical point of view, it can be used to improve fabrication processes, to perform quality controls, especially in food industry and engineering This powerful method can fail to give

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Preface ix

large bandwidth information in several cases: phase transition of the material with temperature, volume to be analyzed too small, bad morphology of the sample In order to overcome such a difficulty, it is possible to use ultrasonic waves This paper, dedicated to high frequency methods (from a few kHz to many MHz) presents a review of existing methods and improvements developed in the author labs Several applications in the domain

of food engineering will be given in order to prove the huge interest of high frequency approaches which are sometimes neglected compared to classical low frequency rheology Chapter 6 - High pressure processing (HPP) is a non-thermal food processing technology that offers great potential for the processing of a wide range of food products Application of HPP can inactivate micro-organisms, affect food-related enzymes and modify structures with minimal changes to nutritional and sensory quality aspects of foods The effects of high pressure on the inactivation of micro-organisms in food have been thoroughly reviewed Recent research on HPP has mainly focused on fruits and vegetables with an emphasis on food quality and bioactive components This chapter highlights the current trends in HPP research and provides a summary of the available findings on the effect of HPP on chemical, nutritional and bioactive components and health related properties of a wider range of commodities Strategies to maintain the quality attributes and health related components in HPP foods and identification of the gaps for future research in HPP are also discussed

Chapter 7 - In order to assure the quality of dry foods it is important to maintain a strict control over the moisture content and temperature conditions during storage Quality loss in dry foods can be due to enzymatic and non-enzymatic browning, lipid oxidation, loss of nutrients, loss of flow and microbial contamination, among other factors properties Determining the optimum moisture content and temperature conditions that minimize the detrimental processes of foods is a difficult task that requires a profound understanding of the interactions of water with other food ingredients Despite the use of increasingly sophisticated analytical techniques that seek to shed information regarding water-food interactions and water-water interactions, the water sorption mechanism in foods is not still understood wholly The majority of foods can be considered as complex colloidal systems in which amorphous and crystalline regions occur, with water acting as a plasticizer Water is a solvent that may take part in detrimental reactions, but in most cases, acts as a medium that provides mobility to reactants allowing them to come into close contact and react Thus, it is convenient to control the participation of water within foods Up to date there is still not a 100% reliable method for predicting and controlling food stability Both, the water activity and the glass transition, are parameters that have been accepted as of food stability criteria worldwide However, several scientific studies have demonstrated that both parameters exhibit great limitations, and that it is necessary to approach this problem from a fresh point

of view Regarding this, two factors are worthwhile considering: (1) equilibrium or thermodynamic considerations, and (2) rate or kinetic processes A reaction may not take place if the thermodynamic parameters are unfavorable Thus, management of the thermodynamic parameters that describe the state of a food is a good starting point for achieving a better understanding of the stability of stored food On the other hand, even when

a reaction is thermodynamically feasible, it cannot occur if the process kinetics does not occur

at a feasible rate In this chapter the thermodynamic and rate processes are proposed as criteria for establishing the stability of stored dry foods It will also be shown that these two factors are closely interrelated, as the equilibrium state of a system depends in great measure

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is currently an important added value for the food industry, and the development and applications of functional foods are being actively advanced Among various functional foods, probiotics is one of the materials that have attracted considerable attention (Sashihara

et al., 2005) Probiotics are living microbes that exert healthful effects on the living body, lactic acid bacteria being a typical example The wide-ranging health effects of various types

of bacteria have been reported, as shown in Table 1.1 Further, epidemiological studies on probiotics for disease prevention and scientific study and commercial development involving useful lactic acid bacteria are being pursued (Watanabe et al., 2005) Probiotic foods are able

to ameliorate the effects of environmental factors, and are useful in disease prevention; establishing the safety of probiotics is easy as compared to doing so for medical chemicals, because the bacterial cells of probiotics have long been used for storing and improving the flavor of food Therefore, various probiotic foods are being researched, developed, and produced These will be indispensable functional ingredients in the future food industry in Japan, where health consciousness is increasing

Chapter 9 - The shelf life of multicomponent food systems depends, among others things,

on how fast the water transfer between components takes place This moisture migration can result in undesirable physical and chemical changes in the system, affecting its quality and shelf life Several factors influence the amount and rate of moisture migration in multicomponent foods However, water activity equilibrium and rate of diffusion are the two main factors To control this migration, several principles can be utilized A raisin-cereal mixture is one of the multicomponent food systems whose quality and shelf life is affected by moisture migration between components In this system, water is transported from the raisin

to the cereals, resulting in quality deterioration to both components One way to reduce the moisture migration in this system is to reduce the water activity of raisins The problem is that the raisin texture, one of most important factors governing their quality, becomes unacceptably hard when their water activity decreases below 0.40 Another possibility for controlling moisture migration is to add an edible barrier between components

In this study, in order to try to reduce the water activity of raisins, while maintaining their softness, raisins were infused with a glycerol-water solution (5:1) applied by vacuum impregnation Mechanical properties, weight changes and water activity were evaluated before and after infusion to study the effect of the glycerol on raisins On the other hand, in order to try to reduce the moisture transfer between components, the raisins were coated by directly applying starch and beeswax to them or by using different film forming emulsions made with whey protein, beeswax and glycerol at different protein:lipid:plasticizer ratios The results of these application procedures have shown that the use of combined solute infusion and vacuum impregnation methods are an effective way of reducing the water activity properties of the raisins as well as serving as an alternative formula towards maintaining raisins at their best possible conditions for keeping a homogenous raisin-cereal system After 1 hour of treatment with glycerol, testing revealed that the water activity of the raisins decreased, thus decreasing the gradient of water activity between both components

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Preface xi

Furthermore, testing has indicated that this treatment does not affect the texture of raisins The hardness of the raisin skin was not influenced by the presence of glycerol, allowing for a produced softness inside the raisins As regards to the testing of various coating effects, the direct application of beeswax seemed to be the best protection from water loss Among the film forming emulsions based on whey protein, the higher plasticizer content lead to a decrease in the water loss protection; although, these differences were not significant In spite

of the fact that the tested films have different water vapour permeabilities when they are treated as independent structures, it seems that the interactions that transpired, between these films and the surface of the product, eliminated the above mentioned differences

Chapter 10 - The type of packaging used has an important role in determining the shelf life of a food and the main purpose of food packaging is to protect the food from microbial and chemical contamination, oxygen, water vapour and light Innovative food packaging concepts has been introduced as a response to the continuous changes in current consumer demands and market trends

Chapter 11 - Thermal properties of foods are vital inputs for many food process models With the recent advances in mathematical modelling and significant reduction in the cost of computational power, uncertainties in model inputs are more and more becoming the limiting factor in model accuracy rather than the model formulation or solution process In this chapter methods and models are presented for predicting thermal properties based solely on data for the composition of the food in terms of its basic components (liquid water, ice, protein, fat, carbohydrate, ash and air) This type of model provides genuine predictions of thermal properties since no thermal property measurements are required, as is necessary with some effective property models that may be found in the literature Foods are divided into different classes, depending on the difficulties they pose for thermal properties prediction Simple guidelines for thermal property prediction are presented along with worked examples to serve

Chapter 13 - In many areas of food industry removal of glucose is considered as an important step in the processing line In some raw materials – like eggs – glucose concentration should be reduced to avoid undesired co-reaction during drying process In the beverage industry glucose level of certain fruit juices needs to be controlled/lowered either to produce low-caloric beverages or to get low-alcohol wine after fermentation (e.g grape must) In addition glucose removal is a significant step in some enzymatic processes like polysaccharide hydrolysis or fructo-oligosaccharide synthesis, where glucose is an inhibitory by-product Separation methods applicable for glucose removal are discussed and compared

in this chapter

Chapter 14 - Instant, or quick-cooking, rice is becoming more popular nowadays However, it still poses problems with respect to rehydration time and quality The effects of processing factors which are: moisture content, pressure and drying temperature has a significant effect on its physicochemical properties and eating quality The hardness and chewiness of rice decreased as moisture content and pressure increased Higher drying

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Mariann A Comeau xii

temperatures caused increases in hardness and chewiness Only pressure and moisture content affected density, rehydration ratio, and increase in the volume of instant rice, which was due to the porosity of the kernels Rehydration ratio had a negative correlation with density (r= -0.886) but a positive correlation with volume increase (r = 0.637) Pressure was the main factor influencing the pasting properties of instant rice All pasting properties of instant rice were far lower than those of milled rice, but instant rice had higher cold paste viscosity, which

is typical of pregelatinized flour This indicated rapid water absorption and shorter cooking time Instant rice processing also caused development of amylose-lipid complexes observed

as the V-type pattern in an X-ray diffractometer

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Chapter 1

T EMPERING , P OLYMORPHISM AND F AT

C RYSTALLIZATION D URING I NDUSTRIAL

C HOCOLATE M ANUFACTURE : R EGIMES ,

B EHAVIOURS AND THEIR E FFECTS ON F INISHED

C HOCOLATE Q UALITY

Emmanuel Ohene Afoakwa1 *

and Alistair Paterson2

1Department of Nutrition and Food Science, University of Ghana

P O Box LG 134, Legon – Accra, Ghana

2Centre for Food Quality, Strathclyde Institute of Pharmacy and Biomedical Sciences,

University of Strathclyde, Royal College Building,

204 George Street, Glasgow G1 1XW, U K

Tempering, a technique of shearing chocolate mass at controlled temperatures is used to promote cocoa butter crystallization in a thermodynamically stable polymorphic form During chocolate manufacture, the process is used to obtain the stable form V (or

ß2) of cocoa butter having a melting temperature of 32-34 °C, which gives the desired glossy appearance, good snap, contraction and enhanced shelf life characteristics However, the tempering sequences, their behaviour during pre-crystallization, the consequential regimes attained and their effects on product quality characteristics are not very well understood Variations in temper regimes attained during pre-crystallization of chocolates influence their crystallinity, polymorphic status and other physical quality characteristics Over-tempering causes increases in product hardness, stickiness with reduced gloss and darkening of product surfaces Under-tempering induces fat bloom in products with consequential quality defects in structure, texture, melting properties and appearance (colour and surface gloss) Thus, the different temper regimes attained during

* Corresponding author: e_afoakwa@yahoo.com / eafoakwa@ug.edu.gh

Tel: +233 (0) 244685893

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Emmanuel Ohene Afoakwa and Alistair Paterson 14

pre-crystallization result in wide variations in product quality attributes with varied influences on quality In a modern competitive confectionery market, understanding the variables leading to chocolate pre-crystallization during tempering and effects of the regimes attained on the quality of the finished products are vital to assurances in quality and shelf characteristics

Keyword: Chocolate, cocoa, cocoa butter, tempering, crystallization, polymorphism, melting,

appearance, microstructure

Chocolate manufacturing involves several complex physical and chemical processes requiring numerous technological operations and the addition of different ingredients, to achieve products of suitable physical and chemical attributes and an attractive appearance and taste Most of the parameters involved influence the rheological characteristics, flavour development and sensory perception [1, 2] During chocolate processing, a process known as tempering is used to promote cocoa butter crystallization in a thermodynamically stable polymorphic form Temperature adjustment is utilized to promote formation of seed crystals

in the correct polymorphic forms to effect good product snap, contraction, gloss and shelf life characteristics

Tempering involves pre-crystallization of a small proportion of triacylglycerols (TAGs), with crystals forming nuclei (1 – 3% total) for remaining lipid to set in the correct form, resulting from a nucleation process which is highly dependent on the process parameters used The final crystal form depends critically on the shear-temperature-time process which the material has undergone The tempered chocolate is then deposited in moulds and cooled

so that subsequent crystal growth occurs upon the existing seed crystals Tempering has four key steps: melting the chocolate mass to completion (at 50°C), cooling to point of crystallization (at 32°C), crystallization (at 27°C), and conversion of any unstable crystals (at 29-31°C) (Figure 1), and it is a function of recipe, equipment, particle size and the final purpose [2-8] Poorly tempered chocolates result in unstable crystal growth and poor setting characteristics, making products more susceptible to fat bloom, a physical imperfection that often manifests itself as a white or greyish-white layer on the surface of the chocolate product during storage Afoakwa et al [9] noted that fat bloom occurs when a lower and unstable crystal form IV changes into a higher and more stable form VI The most important physical and functional characteristics (i.e texture, snap and gloss) of chocolates are dictated by the crystal network formed by its constituent lipid during crystallization [5, 10-12] In industrial chocolate manufacture, tempering is vital, influencing quality characteristics such as colour, hardness, handling, finish and shelf-life characteristics [5, 12, 13-18]

Fat crystallization is a complex process influenced by processing conditions that determines chocolate microstructure and physical properties and thus crucially important to the final quality of finished chocolates The control of crystallization is critical for texture, melting properties and other quality characteristics [11, 12, 16, 19-21] Several authors have studied the melting profiles of chocolates using pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC) [6, 8, 22-24]

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Tempering, Polymorphism and Fat Crystallization … 15

Figure 1 Tempering sequence during lipid crystallization in chocolates [1]

Polymorphism - the existence of two or more distinct crystalline forms of the same substance - is a critical concept in the study of fat crystal structure In fat systems, TAG molecules are able to pack in different crystalline arrangements or polymorphs and exhibit significant melting temperatures [25] Cocoa butter can crystallize in a number of different forms, as a function of triglyceride composition, with fatty acid composition influencing how the liquid fat solidifies Six polymorphic forms (I – VI), have been identified, the principal being α, β and β' (Figure 2); following the two main identified nomenclature schemes [26, 27].Form V, a β polymorph, is the most desirable form in well-tempered chocolate, giving a glossy appearance, good snap, contraction and resistance to bloom [1] In cocoa butter, Forms

VI is the most stable form and difficult to generate although formed on lengthy storage of tempered chocolate accompanied by fat bloom In addition Form VI has a high melting temperature (36°C), and crystals that are large and gritty on the tongue The unstable Form I has a melting point of 17°C and is rapidly converted into Form II that transforms more slowly into III and IV Polymorphic triglyceride forms differ in distance between fatty acid chains, angle of tilt relative to plane of chain end methyl group and manner in which triglycerides pack in crystallization [3] Polymorphic form is determined by processing conditions Fatty acids crystallize in a double- or triple-chain form depending on triglyceride composition and positional distribution All the polymorphic forms could be formed directly from melted TAGs, or via melt-mediated or solid-state monotropic phase transformations [28]

Solid

chocolate

All fats melted

Correct number of stable

Unstable crystals melted

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Figure 2 Temperature regimes and degree of stability of six polymorphic forms of cocoa butter [3].Phase transitions in cocoa butter polymorphs from less to more stable forms are irreversible and dependent on temperature and time Polymorphism in relation to solid continuous phases of cocoa butter has a large impact on chocolate quality, dictating their structural properties [29] Structural factors such as microstructural elements and microstructure characteristics can provide quantitative information about the mechanical properties of the network, and therefore information about the sensory hardness of the network [30] Polymorphic changes can be observed as overall contraction of chocolate, appearance, or undesirable fat bloom formation dependent on relative stabilities of crystal forms and temperature

As information on cocoa butter isothermal phase behaviour during chocolate manufacture

is important for optimizing production processes that maintain product quality, this chapter would provide vital information on current industrial tempering processes, polymorphic behaviours and pre-crystallization regimes during chocolate tempering, and their effects on the microstructure and melting properties of fat systems during industrial chocolate manufacture Additionally, it would provide valuable quality control indicators to ensure the structure and other quality attributes of fat networks being produced on a production line during chocolate manufacture are consistent and would yield the desired mechanical and sensory qualities during post-processing handling, supply chain management and consumption Understanding these processes is important for process design and assurances in quality of products

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Chocolate was hand-tempered before the advent of tempering machines, a strategy still occasionally used by Chocolatiers who produce relatively small quantities of hand-made confections Currently, tempering machines are used and consist of multistage heat exchangers through which chocolate passes at widely differing rates making it difficult to identify optimum conditions Time-temperature combinations are of paramount importance in process design and in continuous tempering; molten chocolate is usually held at 45°C then gently cooled to initiate crystal growth Tempermeters are then used to measure the cooling curves on a chart recorder and the degree of temper determined by the shape of the curve based

on operators experience More recently Tricor Systems in the USA have produced a tempermeter that uses a built-in algorithm to calculate the degree of temper in chocolate temper units (CTUs) and slope (temper index); these can then be used numerically to define the state of temper

In recent times, a number of innovative technologies have been initiated in the confectionery industry to enhance process efficiency and product improvement Two Swiss technologists Windhab (ETH Zurich) and Mehrle (Buhler AG, Uzwil), working with the Buhler "Masterseeder", found that increasing shear during seed tempering can be beneficial

as the kinetics of fat crystal nucleation and polymorphic transformations (α → β2 → β'1) are greatly accelerated The outcome is enhanced overall product quality with reductions in fat bloom Chocolate can also be tempered by the use of high pressure with molten chocolate compressed to 150 bar This increases chocolate melting point and causes it to solidify into solid crystals of all polymorphic forms When pressure is released, lower polymorphic forms melt leaving behind tempered chocolate Subsequent batches can be seeded with stable fat crystals Cocoa butter equivalents (CBEs) and replacers (CBRs) may also find application in the chocolate industry While cocoa butter equivalents are compatible with cocoa butter, cocoa butter replacers (CBRs), which do not require tempering, can only be used if almost all the cocoa butter is replaced These CBRs melt in the same temperature range as cocoa butter, but crystallise only in the β' form [3, 33, 34] As well, effects of shear on chocolate or cocoa butter tempering in a number of different flow geometries have been reported Important studies of scraped surface heat exchangers with cocoa butter and chocolate [35], Couette geometries with milk chocolate [36] and cocoa butter [37], cone and plate systems with cocoa butter [37, 38], parallel plate viscometers with milk chocolate [39], and a helical ribbon device with cocoa butter [15], have been reported with significant application in modern chocolate confectionery industry

Tricor has recently introduced its latest Model 225 Chocolate Temper Meter: a single, compact, low-cost, easy-to-operate unit that can be used in the laboratory or on the production line It allows operators to fill a sample cup with chocolate, place it in the unit and print or display the temper results within minutes, thereby allowing corrective action to be taken before production yield and quality or shelf life are affected A specially designed thermoelectric cooling system combined with a design that controls sample size, probe depth and probe insertion temperature is said to eliminate measurement errors In another development, the chocolate equipment specialist, Sollich, recently unveiled its latest TurboTemper Champ TCN technology, which is designed to improve the tempering process

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in all known chocolate and fat masses It is fitted with a Tempergraph that measures and saves the tempering conditions throughout production for continuous monitoring of the temper quality Sollich can supply the system with an integrated decrystallisation function or with a Turbo Temper AIRO for aeration of chocolate masses for fat-based fillings

Four different regimes have been reported by several authors to exist during chocolate tempering, comprising un-tempering, under-tempering, optimal tempering and over-tempering Each of these regimes show different pre-crystallization behaviours, attain varied polymorphic status with some associated transformations and varied consequential effects on the structure and quality of finished chocolates during processing, post-processing handling and supply chain management [2, 5, 12, 40-44]

Optimal Tempering

During the formation of optimal temper, the temperature of the chocolate being crystallized drops rapidly during cooling until it reaches thermodynamic equilibrium At this point, the crystallization heat released is balanced by an equal amount of cooling energy rending a rather flat time-temperature curve (with a zero slope) The equilibration temperature attained promotes formation of stable fat crystals, which subsequently undergo further growth and maturity during cooling and storage to effect shelf stability of the product The temperature of the chocolate then dropped further when the liquid cocoa butter is transformed into solid crystals resulting in solidification of the products (Figure 3) Fat crystallization process can also be followed by means of viscosity changes as function of time [31] Before crystallization starts, the melt shows Newtonian behaviour but with the formation and growth

of crystals, the viscosity increases almost linearly with the amount of crystals in the suspension until it reaches a thermodynamic equilibrium [45] This technique has also been used to follow the isothermal crystallization of refined palm oil, chocolate and palm stearin in sesame oil [15, 46, 47] Properly tempered chocolate leads to the formation of Form V (β2), the most desirable polymorphic form Well tempered chocolate has the following properties; good shape, colour, gloss, good contraction from the mould, good weight control, good stability (harder and more heat resistant with fewer finger marks during packaging) and longer shelf-life The tempering regime for milk chocolate slightly differs from that for dark due to the influence of milk fat molecules on crystal lattice formation Milk chocolate contains a proportion of butter fat that causes eutectic effect, which prevents bloom formation, results in a low melting point, softening of texture and lowering of temperature to obtain crystal seed for the tempering process (around 29.4°C compared to 34.5°C for plain chocolate)

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Figure 3 Pre-crystallization curves of the different temper regimes in chocolate manufacture [5]

Under-Tempering and Untempering

Under-tempering (insufficient tempering) is caused by the relatively higher temperatures released between multi-stage heat exchangers during tempering The process causes development of more crystallization heat within the product during solidification, effecting quick cooling, as more liquid fat is transformed quickly into solid form The distinct increase

in temperature observed at the beginning of the crystallization, declined again after reaching a maximum point where most of the stable crystals formed were re-melted prior to cooling, resulting in the formation of very few stable fat crystals (Figure 3) Previous studies revealed that un-tempering – an insufficient temper regime, produces no stable fat crystals as the heat

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exchange system generated higher crystallization heat during cooling, resulting in consistent cooling of the completely melted product with no inflexion point for stable fat crystal formation [5] The crystallization processes in both un-tempered and under-tempered chocolates lead to the formation of unstable Form IV (β'1) polymorph, which quickly transforms into Form V within a few hours and with further transformations into a more stable Form VI (β1) polymorph during storage The phenomenon leads to fat bloom, appearance of whitish or dull-white particulate spots on the surface of chocolate, rendering products unacceptable for human consumption [1, 5] Fat bloom arises from changes in the fat structure in chocolate and is caused by a variety of factors, including poor tempering of the chocolate, incorrect cooling methods and the presence of soft fats in the centres of chocolates Warm storage conditions, and the addition of fats that are incompatible with cocoa butter, can also cause fat bloom It frequently results in significant product losses for confectionary manufacturers as, although it does not affect the taste, the tell-tale sign of the bloom – a white frosting – is unacceptable to consumers Additionally, it has been reported that untempering and under-tempering regimes exhibit different crystallization behaviours but results in similar unstable fat crystal nucleation and growth, with similar associated storage polymorphic transformations and defects in textural properties and appearance of products [5]

Over-Tempering

Over-tempering occurs when relatively lower temperatures are exchanged between the multi-stage heat exchangers of the tempering equipment This causes significant part of the liquid fat to solidify within the continuous phase of the chocolate, transforming the product into solid form when less liquid fat was available for pumping it through the multiple coolant regions of the temperer The process effects very slow cooling as very little crystallization heat is released during the process, rendering a rather flat and slow cooling curve causing the chocolate to solidify very quickly (Figure 3) In over-tempering, the crystallization heat released is balanced by an equal amount of cooling energy causing nucleation of stable fat crystals (β2) to effect shelf stability of the product However, the period of equilibrium is very short relative to that of optimal tempering, and this is suspected to affect the crystal size, mass (number), strengths and adequacy of the fat crystals formed and thus possible defects in structure and product shelf stability [41, 43] As a substantial part of the phase transition (from liquid to solid) took place before the chocolate reached the mould, less contraction occurred in the mould, leading to demoulding problems with defects in final product texture and appearance (gloss and colour) and consequential effects on shelf life of products [5, 42]

Effects on Mechanical and Textural Properties

The temper regime attained during pre-crystallization of chocolate has a dramatic influence on the mechanical properties (hardness and stickiness) of finished products Previous reported findings showed varying degrees of hardness and stickiness of products

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with different temper regimes [5] Under-tempered products had the greatest hardness (texture), attributable to the re-crystallization process undergone by the fat in the chocolates resulting in intense hardening of products This trend in hardness was followed by over-tempered samples with the optimal-tempered products possessing relatively lesser hardness levels These suggest that over-tempering of chocolates leads to increased hardness in chocolates as compared to their respective optimally-tempered products However, the degree

to which these changes occur depend on the particle size distribution of the chocolate Particle sizes have been reported to be important determinants of hardness of fat crystal networks in many confectionery products [10, 11, 16, 48] Earlier studies showed inverse relationships of hardness in tempered dark chocolates with particle sizes at varying fat and lecithin levels [49], attributed to the relative strengths of their particle-to-particle interactions [11, 50] Consistent reductions in hardness (texture) of milk chocolates with increasing particle sizes has also been reported [51]

Other important parameter defining the mechanical properties of chocolates is the level of stickiness Stickiness in confectionery gives information about their deformability related to oral sensory characters, an index that defines the rate of melting of products during oral processing – lower stickiness levels is an indication of fast melting character whereas higher levels suggests prolonged melting [52] Previous report explained that temper regime attained during pre-crystallization of chocolates has remarkable effects on their stickiness levels, with

an inverse relationship with increasing particle sizes [5] Over-tempered products had the greatest stickiness levels, followed by the optimally-tempered products with the under-tempered samples having the least The behaviour of fats during crystallization heavily influences the microstructure and physical properties of products such as margarine and chocolates, and ultimately affect the final product structure, texture and quality [20]

Attainment of optimal-temper during pre-crystallization of chocolate is therefore vital to controlling the mechanical properties (hardness and stickiness) during processing and post-processing quality, the knowledge of which are important for quality control and in new product development

Effect on Appearance (Colour, Gloss and Product Image)

Appearance involves all visual phenomena characterizing objects, including gloss, colour, shape, roughness, surface texture, shininess, haze and translucency [53] Work done

on chocolates revealed that temper regime affects to varying levels all colour and gloss measurements [5] Under-tempering has been reported to attain relatively higher L*-values than both the optimally-tempered and over-tempered samples within 14 days after processing,

as a result of blooming effect on products As well, under-tempering causes great reductions

in C* and h° at all PS Components of colour such as L*, C* and h° respectively represent food diffuse reflectance of light, degree of saturation and hue luminance, which are dependent

on particulate distribution, absorptivity and scattering factors or coefficients In a densely packed medium, scattering factor is inversely related to particle diameter [54, 55] Chocolates with varying temper regimes differ in structure and particulate arrangements influencing light scattering coefficients and thus appearance [5] Over-tempered chocolates were found to possess relatively lower L* values at all PS as compared to their corresponding optimally-tempered products These suggest that over-tempering reduces the degree of lightness in

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chocolates, effecting product darkening and thus affecting quality of finished chocolates However, no noticeable effect on C* and h° were observed among the optimally- and over-tempered products Under-tempered (bloomed) chocolates tend to scatter more light, appear lighter and less saturated than over-tempered and optimally-tempered products The blooming process results in higher scattering coefficients, with subsequent paleness (whitening) - higher L* values The whitish haze in bloomed chocolate is caused by the dispersion of light of fat crystals [41] Colour of foods may be affected by various optical phenomena among them are scattering and surface morphology, therefore an accurate understanding of the influence of appearance on measured colour is essential

Gloss relates to capacity of a surface to reflect directed light at a specular reflectance angle with respect to normal surface plane [56] Differences in temper regime have been reported to influence gloss measurements in chocolates to varying levels Blooming of under-tempered samples result in drastic reductions in gloss values than their respective optimally-tempered and over-tempered samples In our previous work, under-tempered chocolates were found to possess the lowest gloss values, followed by the over-tempered and then optimally-tempered products [5] Under-tempering was shown to exhibit the greatest influence on appearance and gloss of products but differences between optimally- and over-tempered products were significant with the over-tempered showing relatively slightly reduced gloss,

an indication that tempering is a key determinant of chocolate gloss In under-tempered chocolates light scattering is affected by reductions in surface regularity Gloss stability of edible coating formulations of chocolates have been studied [57-59] Gloss is an important quality attribute in chocolate and tempering a key processing step to control it [60] The relationship between colour and gloss of chocolates are of current interest to many manufacturers

Digital images of dark chocolates (18 µm PS) assembled to show surface appearances of the optimally-, under- and over-tempered products before and after the 14 days conditioning (Figure 4) showed similar initially smooth and glossy surface appearances soon after tempering but after 14 days, clear differences were apparent The optimally- and over-tempered chocolates maintained their characteristic glossy appearance and dark brown colour but the under-tempered samples bloomed, with appearance of surface whitish spots, rendering them dull and hazy in colour (Figure 4) Similar increases in whiteness in under-tempered and untempered (bloomed) chocolates have been reported [17, 42, 43] This phenomenon has been attributed to re-crystallisation of fats from a less stable Form IV to a more stable Form

VI polymorph, with changes in light dispersion on small surface fat crystals (> 5µm), consequently impacting on both appearance and textural attributes [12, 41] Fat bloom development, mechanisms and effects on chocolate appearance, quality and marketability has been extensively studied [7, 9, 17, 19, 22, 23, 42, 43, 61] Given that chocolate products are meant to respond to consumers acquired expectations, their appearance is one of the most important commercial attributes Attention to tempering is therefore necessary for consistency

in chocolate appearance during product development and quality control

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Figure 4 Photographic images of (a) fresh and (b) matured (conditioned) optimally-tempered, tempered and over-tempered dark chocolates (18 µm PS) [5]

under-Effects on Melting Properties

Thermal properties of cocoa butter and chocolates have been studied using pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC) and together they

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provide information on the phase behaviour of the inherent fats during both mechanical and oral processing [3, 6, 8, 22, 24] In a publication, it was found that typical DSC thermograms

of chocolates manufactured from the optimally-tempered, over-tempered and under-tempered regimes exhibited similar distinct single endothermic transitions between 15 and 55 °C with

peak onset (T onset,), corresponding to the temperature at which a specific crystal form starts to

melt; peak maximum (T peak ), that at which melting rate is greatest; end of melting (T end),

completion of liquefaction and enthalpy of melting (ΔH fat), the energy required to effect complete melting [12] All these information relate to the crystal type, and predicts the polymorphic status of the product Peak height, position and resolution are dependent on sample composition and crystalline state distribution [63]

Differences in temper regime result in varying degrees of crystallinity and melting properties using DSC (Figure 5) The observed differences in the peaks were explained to suggest that variations in crystallisation behaviour in chocolates exist during tempering and influence the degree of crystallinity and crystal size distribution (CSD) of their derived products Under-tempered (bloomed) chocolates showed the greatest peak width, followed by the over-tempered samples having slightly wider CSD than the optimally-tempered products with resultant variation in their melting profiles (Figure 5) The distribution of crystal sizes in foods play key roles in final product quality, defined by the total and specific characteristics

of their crystalline material Number of crystals and range of sizes, shapes, and polymorphic stability, as well as arrangements in network structures dictates mechanical and rheological properties [2, 19] Knowledge and control of CSD can be important for optimizing processing conditions

Figure 5 Typical DSC thermograms of fat melting profile showing optimally-tempered, over-tempered and under-tempered (bloomed) dark chocolates [12]

Under-tempered chocolate were reported to complete melting at higher temperatures than

optimally- and over-tempered products The changing melting end (T end) values the products showed that the crystallites in optimally and over-tempered chocolates were in ßV polymorph

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while that of under-tempered, ßVI Similar melting temperatures and polymorphic status have been reported [41, 42] However, these polymorphic statuses are best identified by powder X-ray diffraction patterns and could be a subject for further investigation The mechanism of identification and principle of the technique has been explained.20 Similarly, under-tempered (bloomed) chocolate had higher melting duration index than their corresponding optimal and over-tempered products, suggesting that the under-tempered chocolate might require longer time to melt than the optimally and over-tempered products Likewise, over-tempered samples were noted to require longer melting durations than the optimally-tempered, with the prediction that the differences found would have likely impact on their behaviour during consumption, attributable to the relative strengths of their mechanical properties (hardness and stickiness), a significant finding for process quality control

Thermal behaviours and ratio of sugar/fat melting enthalpies in chocolates differing in temper regime were studied using DSC to provide information on differences in fat and sugar structure The DSC thermograms (Figure 6) showed differences in fat melting profile, resulting from the widened peak width in the under-tempered (bloomed) sample; but no differences were noted in the sugar melting profiles, explaining the structural (polymorphic) transformations in the fat component in the under-tempered product The report indicated that

the DSC data on fat and sugar melting properties (T onset , T end , T peak , ΔH fat , ΔH sugar and

ΔH sugar /ΔH fat) related to temper regime were similar to the trends for fat (Figure 4) - fat melting profiles suggested the ßV polymorph in both optimally- and over-tempered

chocolates with T end of 32.3 °C and 32.9 °C respectively, and a more stable ßVI polymorph in

under-tempered sample with T end of 35.8°C, with significant influences on T onset , T peak , ΔH fat

in chocolates

Figure 6 Typical DSC thermograms showing (A) fat and (B) sugar melting profiles of tempered, over-tempered and under-tempered (bloomed) dark chocolates at 18 μm PS [12]

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optimally-Emmanuel Ohene Afoakwa and Alistair Paterson 26

Contrary, results of the sugar melting properties showed only marginal differences in all

the melting properties (Tonset , T end , T peak , ΔH sugar) with the different temper regimes, suggesting that no structural change in sugar were found in products from the three temper regimes [12] Similarly, the ratios of sugar to fat melting enthalpies in products from optimal-, over- and under-tempered samples were 1.25, 1.24 and 1.17 respectively with no significant

difference among them These explain that the lower ΔH sugar /ΔH fat ratio noted in the

under-tempered sample resulted from the higher ΔH fat as a result of recrystallization of fat [19, 42] These findings support our earlier report that fat and sugar components are present in similar quantities in both bloomed and optimally-tempered dark chocolates [12], but contrast with the report that the melting peak of fat in untempered (bloomed) chocolate was almost non-

existence with ΔH fat being ten-fold smaller than that obtained for optimally-tempered chocolate [43], concluding that the whitish spots in bloomed chocolates were mainly composed of sugar crystals and cocoa powder and nearly devoid of fat The presence of fat components in bloomed dark chocolate has also been reported [64], suggesting the mechanisms of bloom development in chocolate involves phase separation associated with the growth of xenomorphic fat crystals

Effects on Microstructure

Microstructural examination using stereoscopic binocular microscopy after 14 days of conditioning showed clear variations in both surface and internal peripheries of chocolates from varying temper regimes (Figure 7) [12] Over-tempered products had relatively darker surfaces and internal appearances than optimally-tempered confirming the reported relative differences in L* Under-tempered products showed both bloomed surface and internal periphery with large whitish, and distinct smaller brown spots (Figure 7) The observed whitish appearance on surfaces and internal peripheries appear to be mixtures of fat and sugar crystals, and the small brown spots, cocoa solids These whitish spots were primarily sugar crystals and cocoa powder and nearly devoid of fat [42, 43] These differences in interpretation are recommended as the subject for further investigations Microstructural examination using scanning electron microscopy after 14 days of conditioning showed clear variations in crystalline network structure, inter-particle interactions and spatial distributions

of network mass among optimally-, over- and under-tempered samples, becoming well defined (Figure 8) Microscopy of the optimally-tempered chocolate showed an even spatial distribution of small number of dense crystalline network with well defined inter-particle connections among the crystals suggesting stable β-polymorph (Figure 8) Similarly, micrographs of the over-tempered chocolate showed a spatial distribution of a dense mass of smaller crystals (relative to those of the optimally-tempered) within a network structure of both well- and ill-defined particle-to-particles crystal connections suggesting their β-polymorph stability [12] These larger numbers of small crystalline networks noted in the over-tempered samples is suspected to result from early nucleation and growth of seed crystals due to the slow cooling (Figure 8), leading to the formation of sub-micron primary crystallites from the melt, with the resulting fat crystal network stabilized by van der Waals forces, possibly with steric and Coulombic forces [10, 65, 66]

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Figure 7 Micrographs of surface (a) and internal (b) structures respectively of (1) optimally-tempered, (2) under-tempered and (3) over-tempered dark chocolate (18 µm PS) [12]

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(A)

(B)

(C)

Figure 8 Scanning electron micrographs showing crystalline network microstructures at magnifications

of x 1,500 of (a) tempered, b) over-tempered and (c) under-tempered (bloomed) chocolates at 18 μm

PS C shows some of the well-defined crystal structures; iC shows some of the ill-defined crystal structures; i shows some of the inter-crystal connections The arrows indicate some of the pores, cracks and crevices; B shows some of solid bridges; L shows some of the large (crystal) lumps on the crystal structure [12]

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Under-tempered (bloomed) chocolates showed dissolution, arrangement and

re-crystallisation of the numerous small crystals noted in the over- and optimally-tempered products to a smaller number of larger (lumps) fat crystals (Ostwald ripening), and polymorphic transformation, nucleation and growth of new large crystals in a more stable polymorphic form These observations induced formation of solid bridges with weak and less inter-crystal connections made up of pores, pits and crevices within the crystalline network structures (Figure 8) This phenomenon is attributed to the thermodynamic differences in equilibrium between large and small crystals within a network structure leading to re-crystallization of unstable fat polymorphs [41] In another study, surface imperfections - pores, pits, in filled chocolates were reported on the microstructure of bloomed chocolate [67] Similar findings were reported while studying fat bloom formation and development during storage of under-tempered dark chocolates [9] Both reports explained that morphological changes on the surface of the chocolate were dominated by the growth of needle-like crystals and spherulites on the chocolate with large crystals ~ 100 µm in length, and concluded that from a microstructural perspective, both diffusion and capillarity appear to

be involved in fat bloom formation and development, though temperature, particle size distribution of the product and the presence of a filling fat strongly dictate the rate and type of mechanism that dominate the process

Thus, differences in crystallization behaviour during tempering leads to formation of different microstructural organizations of crystal network structure with associated physical changes in chocolates Characterizing the nature of crystals in confectionery is an important step in quantifying the physical and sensory properties, as the resulting three-dimensional fat crystal network along with the phase behaviour and structural arrangements impact on mechanical, rheological, and melting properties and shelf life [11, 16, 19] Parameters such as cooling rate and thermal history (i.e., crystallization temperature and tempering) influence kinetics and ultimate physical properties of the crystallized fat systems during processing

Fat crystallization behaviour during tempering of chocolates plays a key role in defining their ultimate structure, texture, appearance and melting properties Variations in temper regimes attained during pre-crystallization of products influence their crystallinity, polymorphic status and other physical quality characteristics Over-tempering causes increases in product hardness, stickiness with reduced gloss and darkening of product surfaces Under-tempering induces fat bloom in products with consequential quality defects in texture and appearance (colour and surface gloss) Structure of under-tempered products

causes dissolution of a large number of small crystals through arrangement and

re-crystallization, into a small number of larger (lumps) fat crystals (Ostwald ripening) In this process there is polymorphic transformation, nucleation and growth of new large crystals in a more stable polymorphic form with formation of solid bridges with weak and fewer inter-crystal connections within the chocolate matrix Thus, attainment of optimal temper regime during pre-crystallization of chocolate is necessary for the achievement of premium quality products and avoidance of defects in structure, texture, appearance and melting character

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With the competitiveness in modern confectionery market, manufacturers want to eradicate or minimise the occurrence of fat bloom during chocolate manufacture, and have been involved in rigorous research to resolve this problem Fat bloom caused by temperature damage is more or less under control, where manufacturers know that their chocolate needs to

be stored at a controlled temperature However, fat bloom or fat migration due to inappropriate tempering (untempering and under-tempering) is still a global problem and causes some product losses during storage, largely linked to the quality of the distribution chain Even though taste is not affected by this bloom as it is in the case of sugar bloom (bloom resulting from moisture defects during storage of products under high humidity conditions), the ‘mouth-feel' of the product changes, melting differently in the mouth due to the higher melting point Most manufacturers currently use traditional methods to combat fat bloom For example, one key technique legally acceptable worldwide is the addition of full cream fat powder to milk chocolate to delay the migration of fat bloom In dark chocolate – which only contains cocoa butter, 3-4% butter oil can lengthen the shelf-life and the mechanism involved has been explained.2,40,44 Fat bloom is a common problem in the confectionery industry However, the reported research findings confirm that when chocolate

is properly/optimally tempered as described, fat bloom could be completely avoided, when stored in controlled ambient temperature (18-25 °C) and humidity (50-55%) conditions These findings have significant commercial implications as they are essential to optimizing process development during chocolate tempering, and could lead to the control and/or improvements in product quality during their supply chain and thus cost savings for the global chocolate confectionery industry

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Chapter 2

N ON - LINEAR M ODELING OF Q UALITY OF C OOKED

G ROUND B EEF P ATTIES WITH

V ISIBLE -NIR S PECTROSCOPY

Sreekala G Bajwa1 *

and Jason K Apple2

1 Department of Biological & Agricultural Engineering, University of Arkansas, 203

Engineering Hall, Fayetteville, AR 72701, USA

2 Department of Animal Science, University of Arkansas, B103C Agricultural, Food &

Life Sciences Building, Fayetteville, AR 72701, USA

Chemometric models based on partial least square regression (PLSR) have been successfully used to estimate nutrient content of different raw meat products from spectroscopic measurements Preliminary studies to establish a chemometric model for estimating nutrient concentration of cooked ground beef patties from spectroscopic data indicated that the linear PLSR models are not adequate to represent fat and calories Therefore, this study was conducted to examine two non-linear modeling methods using PLSR and artificial neural networks (ANN) In this study, spectral absorbance in the visible and near infrared (VNIR) region along with data from proximate analysis was utilized to develop and validate the two non-linear models for predicting fat, calories, cholesterol and moisture content of cooked ground beef patties When compared to a linear chemometric model based on PLSR, both non-linear models performed significantly better The ANN model exhibited the best performance which was indicated

by a validation R2 value of 0.93 and residual predictive deviation (RPD) of 3.3 and 3.4 for fat and calories respectively Both non-linear models resulted in RPD ≥ 3 under validation, indicating that they are acceptable However, the model performance was only fair for cholesterol and moisture content

* E-mail address: sgbajwa@uark.edu

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Sreekala G Bajwa and Jason K Apple 36

In developed countries, the consumer's willingness to pay a premium price for meat products that maintain a consistent quality standard has resulted in a demand for fast and efficient methods for estimating meat quality In the US, the increasing consumer demand for food products in the ready-to-eat form has resulted in many processed food products that may

be even partially cooked There is a need for understanding the nutrient value of these various meat products to enable customers to make an informed purchase The persistent problem of obesity has created great awareness among people about the nutrient value of the food they consume Also, certain medical conditions may require people to choose food with a certain nutrient profile or caloric value The new health care bill passed by the US government this year will require all restaurants to include calorie counts of all food items on the menus, menu boards and drive-throughs Currently, the accuracy of such estimations may be questionable Therefore, there is a growing need to develop methods and/or devices that can measure or estimate the caloric value and other quality parameters of cooked food products in a fast and accurate manner Such methods can have applications in food processing lines for controlling the quality of food products, in making decisions regarding the end use of meat, and to understand the nutrient profile and energy content of cooked food products in various food outlets

Standard methods for assessing the nutritional profile of food materials are based on guidelines established by the Association of Official Analytical Chemists (AOAC)[1], and use laboratory-based chemical analyses Since chemical analyses are often time consuming and expensive, many scientists have focused on rapid assessment of nutrients such as fat and protein in raw food, particularly using near infrared reflectance spectroscopy (NIRS) and chemometric modeling methods [2-33] Optical spectral sensing, particularly NIRS, has proven to be a reliable tool for assessing quality of raw meat products The advantages of indirect methods such as spectral sensing include speed, non-destructive nature of the tests, reliability and ability to be incorporated into food processing lines for real-time process control Some of the studies on spectral sensing of food quality have also led to the establishment of online monitoring systems for quality control in food processing lines [23,34-35]

A review of the literature on the application of NIRS to estimate quality of meat and meat products is provided in Table 1 and also by [36] Past research on this topic focused on estimating protein, intra-muscular fat (IMF), moisture content (MC), dry matter (DM), gross energy (GE) or calories, specific fatty acids or fatty acid groups (FAG), myoglobin (Mb) and minerals in meat products using chemometric models based on partial least square regression (PLSR) or modified PLSR (mPLSR) (Table 1) The meat products addressed in these studies included beef, pork, chicken, lamb and fish in various forms including steak, minced and homogenized, sausages and surimi It is evident from these past studies that the NIRS works remarkably well for raw meat products in minced form, particularly for estimating proteins, IMF, MC and DM, but not that well for intact muscles and cooked meat products [2-33]

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Table 1 Summary of research reported in the last 10 years on chemometric modeling of nutrient value of food products from spectral measurements, in reverse chronological order The model performance indicated is for independent prediction or cross-validation or

calibration in that order of preference, based on availability

Study author Meat product Spectral sensor (wavelength) Model Nutrients studied Model performance

[2] Bajwa

et al.,

2009

ground patties (raw)

Beef-ASDLabSpec Pro radiometer (400-1075 nm)

spectro-PLSR IMF, calories,

cholesterol, MC

R2 = 0.94 (IMF), 0.94 (calories), 0.94 (MC), 0.80 (cholesterol)

Protein, IMF, MC,

Mb

R2 = 0.16(protein), 0.76 (IMF), 0.72 (MC) 0.91(Mb)

-Perten 7000 Diode Array NIR /VIS sensor (400-1700 nm)

mPLSR Protein, IMF, MC R2 = 0.95-0.96 (protein),

PLSR Protein, IMF, MC R2 = 0.99 (protein), 0.95 (total

IMF) 0.96 (free fat), 0.98 (MC)

Perten 7000 Diode Array NIR/VIS Sensor (400-1700 nm)

mPLSR Protein, IMF, MC R2 = 0.93 (protein), 0.98 (IMF) 0.98

(MC),

[8] Pla et

al., 2007

ground

Rabbit-FOSS NIR System 5000 (1100-2498 nm)

PLSR Fatty acids R2 = 0.5 – 0.9 (each ),

0.83-0.92 (grouped)

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PLSR Protein, IMF,

DM, ash

R2 = 1.00 (protein), 1.00 (IMF), 0.96 (DM), 0.97 (ash)

FOSS NIR System 6500

(1100-2500 nm)

PLSR Protein, IMF, DM,

FAG

R2 = 0.63 (protein), 0.81 (IMF), 0.72 (DM), 0.79-0.81 (FAG)

[12]

Prieto et

al., 2006

ground LT muscle

Beef-InfraAnalyzer 500 photometer (1100-2500 nm)

Spectro-PLSR Protein, IMF,

GE, DM, ash,

Mb

R2 = 0.87 (protein), 0.92 (IMF), 0.93 (GE), 0.87 (DM), 0.17 (ash), 0.44 Mb

FOSS NIR System 6500 (400-1100 nm)

PLSR Protein MC, R2 = 0.98 (MC & protein)

Foss NIR System 5000

(1100-2498 nm)

PLS-based discriminan

t analysis

Protein, IMF, DM, cholesterol, FAG

R2 = 0.91 (protein), 0.99 (IMF), 0.91 (DM), 0.34 (cholesterol), 0.94-0.98 (FAG)

Zeiss MCS 511/522 diode array VIS/NIR system (380-1700 nm)

Linear regression

IMF R2 = 0.35 (IMF)

Tiêu đề	New Topics in Food Engineering
Người hướng dẫn	Mariann A. Comeau
Trường học	Nova Science Publishers, Inc.
Chuyên ngành	Food Science and Technology
Thể loại	Book
Thành phố	New York

Định dạng
Số trang	326
Dung lượng	7,17 MB