References

Andersen c m and rinnan A (2002) Distribution of water in fresh cod, Lebensm - Wiss u -Technol, 35, 687-96. BARREIRO P, ORTIZ C, RUIZ-ALTISENT M, RUIZ-CABELLO J, FERNANDEZ-VALLE M E, RECASENS I and asensio m (2000) Mealiness assessment in apples and peaches using MRI techniques, Magn Reson Imag, 18, 1175-81. bechmann I e, pedersen h t, N0RGAARD l and engelsen s b (1998) Comparative chemometric analysis of transverse low-field 1H NMR relaxation data In Advances in Magnetic Resonance in Food...

Firmness or hardness

These descriptors are generally used to describe a loss of softness in the breadcrumb. This loss of softness may arise from two main sources a loss of moisture from the crumb or the underlying retrogradation of starch (Pateras, 1998). Hardness may also be considered as a negative attribute for the crust of most bakery products and should not be confused with crispness. While crisp crusts are expected to be hard they are also expected to break or shatter readily. Hard crusts on the other hand...

Introduction

Bread is the product of complex interactions between the main raw materials (wheat flour, water, yeast, salt and other functional ingredients) and different processing methods to convert the dough mass into loaf sized units. An overview of the most common breadmaking processes (Cauvain, 2000) and details of the technology involved in modern bread production (Cauvain and Young, 1998) can be obtained elsewhere. There is no such thing as a 'standard' bread product with many shapes and sizes of...

Yam

Yam (Dioscorea spp.) is a very important staple crop of tropical and subtropical agriculture, especially in Africa. When first harvested, the dormant tubers are stored at 15-16 C and 70 RH. Under favourable conditions, some species can be stored for around three months. As storage at 10 C or less to reduce sprouting can cause chilling injury to occur, sprout-suppressing chemicals are employed and, infrequently, gamma irradiation is used. About 25 of yam fresh weight is starch, mainly in the...

Potatoes

Several recent studies have shown that NMR relaxation data obtained from raw potatoes can predict sensory-determined texture attributes in cooked potato samples. Transverse NMR relaxation measurements on raw potatoes have shown very high correlations with the sensory attributes of firmness, springiness, adhesiveness, mealiness (see Fig. 8.3), graininess and moistness in cooked potatoes (Bro et al, 2002 Thybo et al, 2000 Povlsen et al, 2003). Previous studies showed that NMR relaxation...

Data acquisition equipment for recording and analysis of sound waves

Various amplifiers have been interfaced with the microphones. Most often this amplifier is a Bruel and Kjaer. These amplifiers must be interfaced either with signal conditioners or to a computer with appropriate software. For recording and analysis of acoustic sound waves, one software package which has been mentioned is Soundedit (Macromedia, San Francisco, California). This software can be used to set up the testing situation as well as for analysis of the data by FFT. Another means for...

Effects of processing

Many fruits and vegetables are stored or processed before eating, these processes have major effects on the final texture of the food material, and they are studied and modelled by many scientists and technologists. The most important reason is the urge to optimise the texture, and with it the quality, of the food. It was shown above that the origin of texture is very complex. To understand it, both chemical and physical properties on different structural levels, as well as the structure...

Japanese pear texture

The effect of harvesting dates, storage time and handling on susceptibility to mechanical injury or pear texture has been studied on several cultivars of Japanese pears. Tsukamoto (1981) reported that the Kikusui was more sensitive to bruising than the Choujuurou and that the flesh tissues under the skin of the Japanese pear were very sensitive to bruising by both impact and compression. Chen et al. (1987) studied impact and compression damage to Asian pears. The flesh firmness, measured with a...

Introduction texture and food quality

In prosperous societies, we have available an enormous and ever-increasing range of foods, and manufacturers find themselves in an intensely competitive situation. In less well-developed societies, hunger will be the constant driving force, and our diet will be determined by availability of any food that satisfies our basic nutritional needs. It is increasingly clear that if we are to understand what drives consumers' choice of food, no single factor can be considered in isolation from others....

Measurement of texture 1021 Measurement of sensory texture

Sensory assessment involves the codification of sensory experiences, and is commonly carried out by trained panels. These can provide an objective assessment of sensory attributes or characteristics (Civille and Szczesniak, 1973). Szczesniak (1963) developed a well-organised approach for the classification of textural characteristics according to three groups 1. mechanical (hardness, cohesiveness, viscosity, elasticity and adhesiveness brittleness, chewiness and gumminess) 2. geometrical (those...

Microwave blanching

Microwave processing can offer several advantages when compared to conventional heating methods. These include speed of operation, energy savings, precise control, and faster start-up and shut-down times. Microwave blanching can fulfil one or more of several purposes 1. inactivation of enzymes prevents discoloration or development of unpleasent taste during storage 2. improved texture due to liberation of water 3. expulsion of air, which is confined to plant tissues, and reduction of oxidation...

Future developments

Although it is increasingly being recognised that only sensory methods can give a complete picture of food texture, many needs can be identified for the Fig. 1.5 Comparison of the emitted sound level with the differential of the force changes from cutting celery using an incisor probe. Fig. 1.5 Comparison of the emitted sound level with the differential of the force changes from cutting celery using an incisor probe. instrumental measurement of key textural characteristics, and considerable...

Puncture test

The hardness or crispness of bread crusts may be assessed using some form of puncture test. The shape of the probe used for such tests is in the form of either a needle or a small diameter cylinder. Cauvain (1991) used a needle probe to examine the changes in hardness of all of apple pie components with storage time. Measurements of lid pastry crispness, filling firmness and base pastry softness were made in a single pass though the sample. The loss of crispness in the pastry arose from...

Future trends

High pressure offers new opportunities for food processing and preservation, not only at temperatures above zero but also at those below zero (Denys et al., 2002). The advantage obtained by using high pressure is the prevention or retardation of the damages caused by ice crystals. By using high pressure, the freezing point can be lowered to -22 C allowing sub-zero storage of foods in the liquid state without freezing. Studies with strawberries have shown that their fresh taste, texture and...

Consistent theory

Consistency is the crucial issue in developing theoretical views and fundamental models, especially when interactions play their confusing role as they do in texture behaviour. The more interactions there are, and the more compounds or processes which could be the major source of change, the more a consistent theory is needed to understand all these interactions. But at the same time, the more difficult it is to develop a consistent viewpoint. But that is exactly what is needed to bring the...

Useful references

For further understanding of fractal dimensions, the book Fractal Surfaces by Russ (1994) provides an overview of fractal analysis. This book also contains a computer program which can be used for calculating fractal dimensions. Additionally, the fractal dimension of a sound wave can be calculated by using MATLAB (The MathWorks Inc, Natick, Massachusetts). There are also many books which can be of use for gaining an understanding of hearing, and the physics of sound. Two books which this author...

Improving texture

The opportunities for improving bread texture can be considered under three main headings ameliorating storage changes using alternative production technologies. The profound influence of changes in bread volume, density and cell structure on the textural properties of bread have already been discussed above and a number of potential ingredient effects introduced. In most cases improvements are aimed at produced a softer bread crumb at the start of shelf life so that, even if the staling rate...

Measuring texture

Texture determines the rheological property (the relationship between applied physical stress, forces applied per unit area, and deformation of materials), or the mechanical property of solid foods which, in turn, determines how people feel during mastication. Although mouthfeel is a complex function of many variables, for analytical purposes, it is possible to simplify the complex physical interactions which take place during mastication to three basic types of physical forces compressive,...

Modification of PODs activity via processing

Thermal inactivation of PODs during heat treatment of fruit and vegetables has been thoroughly investigated, since the action of these enzymes may cause adverse changes of colour and flavours during food preservation. Moreover, PODs are generally used as indicator enzyme to assess the effectiveness of heat treatment. Thermal inactivation and regeneration of POD activity depends on several factors, such as temperature and time of treatment, pH value and ionic strength (Kermasha et al., 1988...

Compressiondeformation tests

Objective compression or deformation testing may be carried out in one of two ways either the food is subjected to a standard compression force and the distance through which it is compressed is measured, or the food is compressed through a standard distance and the force required to achieve this is measured. Both methods have been used in the assessment of cereal-based foods. Owing to its cellular structure bread crumb does not obey Hooke's Law, but it does have a stress strain relationship...

Cassava

Approximately two-thirds of cassava (Manihot esculenta) production is used for human consumption in either fresh or processed form. The major value of cassava is its high-caloric contribution with more than 300 million people in tropical regions depending on it as an energy source. Fresh roots contain 35-40 dry matter, of which about 90 is carbohydrate. Cassava requires immediate utilisation because of its rapid physiological and microbial deterioration after harvest. A large proportion of the...

Data analysis

Most NMR relaxation data and MR-images are characterized by a complex multivariate structure with both compositional and spatial information. Optimal extraction of information from such data structures requires the use of advanced multivariate statistical data analysis techniques. Novel chemometric techniques extract the relevant information in the NMR data and develop a predictive model between the NMR data and the quality attributes (Bro et al., 2002). As an alternative to the previously...

Scoring method

D'Egidio and Nardi (1996) described a scoring method used in Italy for assessing cooked pasta quality. Experts (at least three persons) evaluate stickiness, bulkiness and firmness using scales ranging from 1 to 100. Evaluations of stickiness and bulkiness are done both visually and manually, while firmness is evaluated orally. An overall quality score is determined by calculating the mean of each of the three scores and summing. An overall score greater than 80 indicates excellent quality while...

Understanding consumer preferences

Moskowitz and Jacobs (1987) described several methods for developing an understanding of the importance of texture in determining the relative importance of food texture to the product acceptance. The simplest method they described is the direct rating of importance. With this method, consumers are asked to rate the importance of various product attributes, including texture, on a scale from 0 to 100. By comparison of mean values for the various attributes, one can evaluate if texture plays an...

Factors influencing texture

More than five factors which determine the texture of the fried product can be easily identified. Before frying, characteristics of the food, such as water content, size, types and amount of protein and starch, composition of coating materials (batter, breadcrumbs, etc.) and additives, are important factors which establish the necessary chemical and physical environment which leads to the desired texture after frying. Processing variables, such as frying time and temperature, cooling condition,...

PPOs and PODs implications for food texture

The exact role of PPOs and PODs in determining texture of fruits and vegetables via their possible involvement in the formation of cell walls in food crops is sometimes hard to assess. An exact evaluation requires the study of the function of single parameters (the enzymes under study) in complex systems with interdependent parameters that affect the eventual outcome, i.e. texture. Yet, the work of Brett et al. (1999) suggests a direct relation between cell growth, cell wall expansion, and...

Dynamic forcedeformation methods

The most common material parameters linked to firmness are the elastic properties of the product hard materials have high values of the elastic modulus, while soft materials have lower values (Pitts et al., 1994). Abbott and Massie (1995) believed that approximate values of the elastic properties of produce were adequate for sorting, and that a dynamic force deformation (F D) test might be relatively simple to implement on a kiwifruit packing line. They compared various parameters from a...

Casestudy breaded chicken nuggets

This study was undertaken with following objectives to determine ultrasonic parameters and mechanical properties and to investigate the relationships between the instrumental parameters and sensory crispness obtained using a trained panel for chicken nuggets (Antanova et al., 2003). Breaded par-fried chicken nuggets were used in this study. Frozen breaded chicken nuggets were finish cooked using the following procedures (1) finish-fried in a deep-fat fryer at 375 F for 4-5 min (2) baked in a...

Vegetable texture determined by starch

Starch contributes to the texture of heat-processed vegetable products due to its presence in various crystalline and amorphous forms within the granule, and the extent to which the crystalline regions are disrupted and the starch gelatinised during heat treatments. The degree of starch gelatinisation has a major impact on the flow of the product in the mouth during mastication (mouthfeel), and therefore on the perception of texture. Whilst environmental conditions are known to have an effect...

Structural and geometrical properties

Many researchers agree that crispness should result from the structural properties of a food (Barrett and Peleg, 1992 Barrett et al., 1994 Bouvier et al., 1997 Gao and Tan, 1996a Mohamed et al., 1982 Stanley and Tung, 1976 Vickers and Bourne, 1976 a,b). Matz (1962) and Coppock and Carnford (1960) proposed that crisp, dry foods, such as biscuit, break into many pieces when masticated and their eating quality is affected by the size of air cells and thickness of the cell walls. Crispness is...

Processing variables

Processing variables like frying time and temperature are factors that can be easily adjusted without too much trouble in order to improve texture. As mentioned above, high oil temperature means high temperature gradient and consequently high heat penetration rate and faster increase of temperature near the center. However, before the operator boosts up the oil temperature, it should be noted that, at high temperature, the effect of increased water evaporation rate is more profound near the...

Challenges to understanding consumer preferences

Although this simple example seems to provide the necessary elements for a product developer to optimize this type of product, it is rarely the case in practice. This is due to the fact that, to gain valuable information and a complete picture of the drivers of liking, one has to get several things right in the design of the experiment. First, the right questions need to be asked of consumers, and that is where the greatest challenge lies. The major limitation is that consumers have a very...

Journal of Texture Studies

Food and Nutrition Press, 6527 Main Street, PO Box 374, Trumbull, Connecticut, 06611, USA. Publishes original research, reviews, and discussion papers on rheology, psychorheology, physical testing and sensory testing of foods. Journal of Food Composition and Analysis By Academic Press an international journal, it is the official publication of INFOODS, and is co-sponsored by The United Nations University and the Food and Agriculture Organization of the United Nations. This journal is devoted to...

Sensory method

Sensory evaluation is considered to be the most reliable method for measuring the textural properties of cooked pasta since panellists have the ability to measure the overall textural characteristics of cooked pasta. In contrast, instrumental methods can measure only a limited number of characteristics, which may not necessarily relate to sensory judgements. To be meaningful, instrumental measurements must be validated by calibrating against sound sensory measurements. Despite the advantages...

Electromyography EMG

Electromyography is a technique to characterise the chewing patterns of foods which differ in texture (Agrawal et al., 1997 Brown et al., 1994 Kilcast and Eves, 1991). It forms something of a bridge between instrumental tests and sensory assessments since it is an objective measurement carried out on human subjects. Brown (1994) has shown the use of EMG to characterise consistent differences in chewing patterns between individuals, and reviewed its use in the literature. EMG characteristics...

Mechanisms of texture perception

Either of the two mechanisms described in Section 1.1.1 (proprioception and somesthesis) can operate during the mastication process, depending on the nature and texture of the food. The texture of solid foods is perceived primarily through proprioception, as the food is chopped by the incisors and ground by the molars. As the physical state of the food changes dramatically during mastication, both mechanisms can be operative. In particular, during the mastication of solid foods somesthesis...

Protein and starch

Protein and starch are the major constituents in foods that are responsible for forming the various characteristic types of texture. At the elevated temperature reached during frying, reactions of both a physical (phase change, volume expansion, solute concentration, etc.) and a chemical (destruction and formation of chemical bonds) nature are taking place. Protein denaturation and starch gelatinization are typical examples of the combined effect, physical as well as multiple-order chemical,...

Sources of further information and advice

Readers are recommended to consult an excellent monograph on Rice Chemistry and Technology, published by the American Association of Cereal Chemists (Juliano, 1985a). The third edition of the monograph is expected to be available in 2004. The major rice research bodies include the Philippine Rice Research Institute (Laguna, Philippines), the National Food Research Institute (Tsukuba Science City, Japan), and the US Department of Agriculture. Names and organizations of Asian scientists...

Statistical analysis

A generalized randomized complete block design can be used to analyze the data from each training test and to determine if panelists could perceive significant differences in crispness among the products. A randomized block design is effective when the panelists are consistent in rating the samples but might use different parts of the scale to express their perceptions. Data in the form of ratings from a randomized block design can be analyzed by analysis of variance (ANOVA). Tukey's Test can...

BRAM Blanching Response Amplification Model

The complexity of firmness changes as a consequence of technological actions is clear from the increase in firmness that is often encountered when cooking or sterilising fruits and vegetables that are rich in pectins (Stolle-Smits, 1996). This increase is observed both in objective measurements (Stolle-Smits, 1996 p. 96) and in sensorial evaluation (Stolle-Smits, 1996 p. 113). Whether or not the increase in firmness is an agreeable one remains to be seen. The phenomenon cannot only be observed...

Establishing the importance of texture to consumers

The effects of appearance and flavor on consumer acceptance of foods have been extensively studied. However, there are fewer studies dealing with the effect of texture attributes on food acceptability. In 1971, Szczesniak assessed the apparent relative and a priori importance of texture and flavour on the acceptability of foods via a survey of150 consumers. Surprisingly, the texture flavour index, a measure of the relative importance of texture in comparison to flavour was 0.89 for the group....

Diffusion of water during cooking

Suzuki et al. (1976) measured the gravimetric change of rice grains during cooking at evaluated temperatures, which was analyzed using a shell and core model, assuming that the gelatinization was much more rapid than the rate of water diffusion in a grain so that the starch gelatinization occurred only at the interface of the uncooked core. They reported that D (cm2 min) of rice was 1.86 x 10-3 at 110 C, 3.32 x 10-3 at 130 C, and 5.05 x 10-3 at 150 C. The gravimetric change of a rice grain...

Optimisation and reversed engineering

Modern society requires a different approach to consumers' wishes. Nowadays, it is no longer technology push, i.e. putting new products on the market based entirely upon technological possibilities, that determines what consumers buy and eat the technology has to adapt far more to the demands of the market in order to produce new and acceptable products (market pull). So, for food engineers, this changes the entire framework of their actions. The question is no longer What can we produce It is...

Single attribute analysis

A common model described by Moskowitz (1980) is of the quadratic form liking A + B(intensity) + C(intensity)2 2.1 The main advantage of the equation is that it allows liking to follow a parabolic response, but does not force it if the relationship is not of that form. The relative importance of the attribute can be calculated as the absolute value of the partial derivative of Eq. 2.1 and is defined as importance B + C(intensity) 2.2 This equation implies that the importance of a single...

Destructive measurements

There are a wide variety of methods and or techniques for destructive measurements of solid foods. Destructive methods can be empirical or fundamental. Empirical destructive methods are often somewhat imitative of methods used in sensory analyses or in the preparation of the food, such as spreading butter on bread, slicing meat, or cutting asparagus. They involve a complex form of loading with the stress and strain levels well beyond the initial failure, and the quantity measured often cannot...

Effects of enzymes on texture

Enzymes play a prominent role in our food. They are essential in the development and decay of fresh fruits and vegetables and hence crucial in all quality attributes, including texture. However, in man-made products too the action of enzymes, or its prevention, is of prime importance. Conservation of fresh food to prolong product lifespan, by sterilisation, pasteurisation and freezing, relies to a large extent on the complete inactivation of those enzymes which enhance quality deterioration...

Sweet potato

Sweet potato (Ipomoea batatas) is a storage root that is consumed for its high energy value by many millions of people, mainly in Asia. There are three major sweet potato types which are characterised after cooking as (1) flesh that is firm, dry and mealy (2) flesh that is soft, moist and gelatinous (3) flesh that is coarse and fibrous. Only the first two types are used for human consumption, of which the first is generally preferred. In the USA, cultivars having a deep orange flesh and a soft...

Experiment design

As mentioned before, people tend intuitively to turn to the one-variable-at-a-time technique for its conceptual simplicity and ignore the possible interaction between independent variables. A good example of the interaction between factors is that between water content (W) and frying temperature (T). Assuming W and T are the chosen factors for optimization, one possible interaction will be that T tends to influence the way W affects the texture and vice versa. Since water molecules are removed...

Volume 2 Solid foods

Boca Raton Boston New York Washington, DC Published by Woodhead Publishing Limited, Abington Hall, Abington Published in North America by CRC Press LLC, 2000 Corporate Blvd, NW Boca Raton FL 33431, USA First published 2004, Woodhead Publishing Ltd and CRC Press LLC The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been...

Comparing instrumental and sensory measurement of texture

Instrumental methods for measuring texture are valid only if they can predict sensory textural attributes. This aspect has been studied in depth (e.g. Szczesniak, 1987 Peleg, 1983 Brennan and Jowitt, 1977). However, a number of recent studies have indicated that in fruits and vegetables sensory measurement cannot yet be replaced by instrumental approaches (e.g. Harker et al. (2002). Nevertheless, recent advances in data handling and interpretation may provide further opportunities to explore...

Sensory and instrumental texture

Instrumental measurements are only as relevant as their predictive power with regard to sensory attributes. Szczesniak (1963) linked texture to sensory, structural and physical parameters.The subtlety is that instrumental measurements are not always focussed on texture but on maturity, in the case of fresh fruits and vegetables, or susceptibility to damage in transport or processing. Sherman (1979) expressed texture as the composite of those properties arising from the structural elements and...

Evaluation of breaded fried products under experimental conditions

For actual experiments, a trained panel should evaluate crispness intensity in breaded fried samples under different processing and storage conditions to get a range of crispness values. Samples could be finish cooked using the following procedures (1) finish-fried in a deep-fat fryer (2) baked in a convection oven (3) heated in a microwave oven. The samples cooked in a microwave oven will have the least crispness, followed by the baked samples and the fried samples will have the highest...

Displacement and kinesiology

Several studies have investigated oral motility from studies of tongue and jaw movements. Movement of the lower jaw can be studied by tracking 3 j p ' 1- ) m I -' '-I- -V 3 j p ' 1- ) m I -' '-I- -V 1 1II 0 10 20 30 40 50 60 70 80 90 100 110 120 Fig. 3.4 Recording of EMG signals from left (L) and right (R) masseter (Mass) and temporalis (Temp) muscles, Time-Intensity (T-I) curve for flavour, and swallows indicated by a swallow button shown as voltage spikes (channel '5'). Fig. 3.5 EMG...

Introduction distribution of polyphenoloxidases PPOs and peroxidases PODs in plants and plant cells

Polyphenol oxidases (PPOs) comprise an enzyme family that is composed of the copper-containing tyrosinases (EC 1.14.18.1) and laccases (EC 1.10.3.2). The denomination polyphenol oxidase resp. tyrosinase is sometimes used to indicate the same type of enzymes polyphenol oxidase is seldom used to indicate a laccase. In the context of this chapter, when we discuss PPOs, we are referring to the tyrosinases, a group of enzymes that bears structural similarities to the oxygen-transporting hemocyanins...

Mechanical property measurements

Normalization of the peak force and total energy was done by dividing the values by the mass of the sample. The normalized peak force and normalized total energy significantly varied among the samples cooked by different Effect of moisture content on ultrasonic velocity (Adopted from Antonova et al., 2003). methods and stored under different conditions. Samples cooked in a deep-fat fryer had higher values for the peak force and total energy than samples cooked in an oven and microwave oven....

Pe

At constant conditions of treatment time and temperature, the set of differential equations can be solved analytically. The resulting equation, however, is very cumbersome to use in normal statistical analysis. It contains several occurrences of the mathematical exponential integral that can be handled by mathematical packages like MapleV (www.maplesoft.com) and Mathematica (www. wolfram.com), but not by standard statistical packages. It was therefore assumed that at blanching conditions the...

Resistance to thermal softening

Some edible, non-lignified parenchyma tissues fail to soften during thermal processing. Chinese water chestnut (CWC), Chufa and mature sugarbeet and beetroot contain examples of these tissues (Parker and Waldron, 1995 Parr et al., 1997 Waldron et al, 1997a Ng et al., 1998 Parker et al., 2000). In CWC, the edible tissues consist of thin-walled, starch-rich storage parenchyma with a few thin vascular bundles. After thermal treatments such as cooking or canning, CWC retains its firm and crisp...

Black oxidised olives

In black oxidised processing in the Californian style, the olives, mostly green and cherry, are normally stored in brine with 5-10 NaCl for between two and six months, depending on the needs of production. The brine may be acidified to pH 4 with lactic acid and acetic acid and kept in anaerobic or aerobic conditions. To improve texture, calcium chloride could be added during this period. Once the fresh or stored fruits are sorted and occasionally graded, they are treated with a series of dilute...

Manmade products

Although products with a natural origin, like meat, fruits and vegetables, are eaten fresh, the actual structure of many food products is obtained by processing. Examples of such man-made products are bread, cheese, mayonnaise, etc. The texture of this type of product depends on both composition and structure. Shear, pressure and temperature are the processing parameters that have most effect on the structure. Spontaneous compartmentalisation has to be taken into account (for instance phase...

Cellular stability during processing

High temperature heating of fruit and vegetable tissues causes an initial loss of instrumental firmness due to the disruption of the plasmalemma and an associated loss of turgor (Greve et al, 1994). This may result in the development of a rubbery character. However, the most notable change involves tissue softening which results from an increase in the ease of cell separation in many non-lignified tissues (Van Buren, 1979). Thermally induced cell separation is believed to be due to the...

Texture related to flavour and nutrient release

The organoleptic quality of fruits and vegetables is influenced not only by texture, but also by the taste and aroma (Boyar and Kilcast, 1986 Piggott, 2000). The taste of an ingested plant tissue will be dependent on the extent to which flavours and volatiles within the food are released into the mouth, enabling them to come into contact with saliva and then sensory cells. The most relevant cell-wall influence relates to the fracture or separation of plant cells, and therefore to texture. Cell...

Maintaining texture conventional prefreezing treatments

The two most common problems in frozen fruits and vegetables are chemical reactions that cause changes in flavor, color, texture, and nutrition and physical damage that causes loss of turgor and texture changes (Haard, 1997). Loss of tissue firmness, disruption of the cell membrane, and excessive softness are the major consequences which need to be avoided (Rahman, 1999). Loss of membrane semipermeability and disruption of cellular compartments can be minimized by rapid freezing rate, low...

Mechanical properties

Perhaps the most prevalent objective measurement for crispness is determination via mechanical properties. Mechanical properties are believed to reveal the structural properties of materials by means of resistance to compression by a blade probe and to a tensile fixture that pulls the structure of food material apart by using a universal testing machine or a texture analyzer. The measurement of mechanical properties is easier to conduct than that of structural properties, determined via the...

Determination of water and waterholding capacity in solid food by lowfield NMR relaxation

As pointed out previously, many of the investigations using NMR to predict the contents of water and fat have been carried out without any attempt to predict texture. However, these studies are also relevant in the present context, as water and fat are of importance for texture, and they should be able to give O Mealiness r 0.90 0 Moistness r 0.84 O Mealiness r 0.90 0 Moistness r 0.84 Fig. 8.3 Low-field NMR relaxation curves of four different potato varieties (up) prediction of mealiness and...

The development of firmness testers for pear

The technique of using a small spherical impactor for testing the response of fruits to impact was described for the first time by Chen et al. 1985 (cited in Chen et al., 1996). Chen et al. (1996) determined the effect of impacting mass on firmness sensing of fruits both theoretically and experimentally. They pointed out that the desirable features associated with low impacting mass were increases strength of the measured acceleration signal, thereby facilitating easier detection and maximizing...

Partial air drying

Partial dehydration is generally achieved by air drying. The resulting process is termed dehydrofreezing. The advantages over conventional freezing include (1) energy savings, since the water load to the freezer is reduced, as well as reduced transport, storage and wrapping costs (2) improved quality and stability (color, flavor), as well as better thawing behavior (lower drip loss). When using partial air drying, food ingredients of high water activity (aw > 0.96) are generally obtained,...

Acoustical properties

Perhaps the first impression of a crisp food is the sound burst during biting. Due to the fact that the crushing of crisp or crunchy foods results in fracture and fragmentation, it appears that fracture and sound emission are associated. Attenburrow et al. (1992) reported that the sounds emitted during the crushing of a dry product are due to a sudden release of stored elastic energy. The association between mechanical fracture and sound emission has been further elaborated by Chakra et al....

Hedonic scales

The most commonly used hedonic scale, at least in English speaking countries, is the nine-point hedonic scale (Jones et al. 1955). The main characteristics of the scale are that each category is associated with a verbal descriptor from dislike extremely to like extremely and that the scale has a neutral category neither like nor dislike. Although it has been widely used for almost 50 years, the scale has been equally criticised. The nine-point hedonic scale has been popular because of its...

Mechanism of reactions catalysed by PPOs and peroxidases

PPOs (tyrosinases) are able to catalyse the ortho-hydroxylation of phenolic moieties into the corresponding catechols, and the subsequent oxidation of these catechols into the corresponding quinones (Fig. 12.1). After the formation of quinones, subsequent reaction is possible if a nucleophilic moiety, potentially intramolecularly, is present (Fig. 12.2). This nucleophilic moiety does not necessarily have to be present intramolecularly, which offers the mechanistic basis for the involvement of...

Timeintensity and multitasking

Time-intensity (T-I) techniques involve the recording of specific sensory attributes as a function of time (Lee and Pangborn 1986). Cliff and Heymann (1993) have reviewed the use of T-I techniques and their use for sensory flavour and texture. Wilson and Brown (1997) used combined EMG and TI in a study of mastication and flavour release from gels of differing mechanical properties, where they observed that the act of swallowing was often associated with a marked increase in flavour perception....

The use of acoustics to differentiate between crispness crunchiness and crackliness

In addition to developing an understanding of the sensation of crispness, acoustic techniques have been used to differentiate between the sensation of crispness and those of crunchiness and crackliness. Crunchiness has been shown to be strongly related to crispness (Vickers and Wasserman, 1979 Vickers, 1981), and various definitions indicate their close association. Recently, Fillion and Kilcast (2002) proposed that the crispness of fruit and vegetables can be defined as 'a light and thin...

Defining pasta

The general category of 'paste products' includes Asian noodles and pasta. Some forms of Asian noodles and pasta have similar appearance, but they are distinguished by differences in manufacturing process and raw material preference. Asian noodles are prepared by passing dough through sheeting rolls (Hatcher, 2001). The main raw material is common wheat flour. Asian noodles are diverse, differentiated based on ingredients and processing following sheeting. Asian noodles may or may not contain...

Application of NIR to fruit and vegetables

While the texture of cereals tends to be an indicator of processing requirements, the texture of fruit and vegetables may often be used as an indicator of ripeness or the presence of damage. In some cases, it also may be used for the prediction of end-use properties such as when differentiating between waxy and floury potatoes. Fundamental to producer and processor, however, is an understanding of the integrity of the material produced or delivered. This has historically been a difficult area...

Quasistatic versus dynamic measurement

Since viscoelastic material is time or loading-rate dependent, its mechanical behavior will be different for different loading rates. For example, the elastic modulus of apple tissue generally increases with loading rate (Petrell et al., 1980). To completely describe this rate-dependent behavior, the test specimen may have to undergo an extended time period (e.g. from many minutes to days) under the creep and or stress relaxation tests. This is not only time-consuming but also impractical, as...

PPOs and PODs structure and mechanisms of action

12.3.1 Molecular structure of PPOs and PODs Homology between various PPOs was shown in a phylogenetic tree that was constructed for 35 PPO sequences from the EMBL and NCBI databases (Wichers et al, 2003). This phylogenetic tree was based on partial sequences, which included the central catalytic domains, flanked by the copper binding domains as defined by Van Gelder et al, (1997). Phylogenetic analysis showed that PPOs clustered in groups for higher plants, vertebrate animals, fungi and...

Mechanical characterization of solid foods 521 Basic concepts

Texture is a quality attribute that is closely related to the structural and mechanical properties of a food. It is, therefore, essential to understand the mechanical properties of foods, in studying their textural properties and measurement techniques. The study of mechanical behavior, i.e. deformation and flow, of foods under applied forces falls within the scope of food rheology, which is a broad, currently active research area covering both solid and liquid foods. A number of textbooks and...

Water loss

Since, with modern technology, water loss is not the major source of firmness decay, and can be kept to a very low level, it will not be considered in this example. Cellulose decay can be completely neglected due to its very slow rate. So, in this example the main emphasis is on firmness loss caused by the decay of pectin. The conditions in which the apples are stored and those at harvest may affect the quality decay and firmness deterioration. Lowering the temperature slows down ripening and...

Elastic materials

Different foods can exhibit very different mechanical behaviors under uniaxial compressive or tensile loading (Fig. 5.3). The force deformation response for a cylindrical apple tissue specimen under compressive loading (Fig. 5.3a) may be divided into three phases. During the first phase of deformation, the relationship between force (or stress) and deformation (or strain) is linear and elastic. (Non-linearity at the beginning of the force deformation curve is mainly caused by the imperfect...

Use of near infrared spectroscopy NIR to evaluate textural properties

Near infrared (NIR) spectroscopy which can avoid the complexity of sensor contact and associated handling problems (Delwiche et al, 1996) has recently been studied as a means of evaluating the texture of intact apples by Cho et al., 1996, Onda et al., 1996, Sohn and Cho, 2000, Lu et al, 2000 and Park et al, 2002 plums by Onda et al., 1996 pear by Sirisomboon, 2001 sweet cherries by Lu, 2001. As described by Robert and Cadet (1998), the spectral information obtained in the NIR spectral region...

Application frozen berries and jams 1641 Potential techniques for berries

Berries can be frozen in syrup or as individual berries. As individual berries, they may be frozen on a tray or individual quick frozen (IQF) on a belt in an air-blast or cryogenic freezer. Depending on the final product, different freezing procedures might be appropriate (Reid, 1996). Freezing berries by fluidization yields products of the same quality as does liquid nitrogen freezing, but requires less time (Miller and Butcher, 2000). Strawberries for commercial preserves, jam, and jelly...

Preserving fruit firmness by calcium or polyamines infusion

The process of dipping whole fruits in aqueous preservative solutions, which is improved by vacuum application, has been used to prolong the post-harvest shelf life of many products apples (Scott and Wills, 1977, 1979 Lidster et al., 1986), lemons (Valero et al., 1998a, b), avocados (Wills and Sirivatanapa, 1988), mangoes (Tirmazi and Wills, 1981), tomatoes (Wills and Tirmazi, 1979), strawberries (Ponappa et al., 1993). The compounds used in the impregnation solution are usually calcium salts...

Crispness vs crunchiness

The definition of crispness is not yet completely understood with only the generalized concept having been established. In general, crispness is a highly valued and universally linked textural characteristic that has many positive connotations (Szczesniak and Kahn, 1971). Crispness in one commodity may not mean the same in terms of textural quality as crispness in another, e.g. crispness in nuts as compared with crispness in potato chips. Historically, crispness was defined as the quality of...

Recording of acoustics produced during mechanical testing

One of the stated advantages of recording an acoustic signature by mechanical testing is the reproducibility and consistency of mechanical tests (Mohamed et al., 1982 van Hecke et al., 1998). However, it is important that the instrumental test selected simulates the conditions to which a food is subjected during chewing (Mohamed et al., 1982). Factors such as the type of probe used and the speed of the crosshead during testing must be carefully considered to ensure that the instrument...

Determination of texture by lowfield NMR relaxation

As mentioned above, NMR relaxation can be used to display different water compartmentalizations in food materials by measuring the relaxation rates of the water protons. Several researchers have stated that NMR relaxation is a rapid, non-invasive and non-destructive method of determining the distribution of water pools with different relaxation rates in foods (Cornillon, 1998 Ruan and Chen, 1998). Water distribution in foods is an important characteristic in relation to food texture quality....

Lignin forming vegetables

Yam tubers begin to harden a few days after harvesting. Hardening becomes so pronounced that two or three weeks later the tubers are inedible, even after extended cooking. This is probably due to lignification reactions. The parenchyma cell walls rapidly lignify, starting from the corners of the cells near intercellular spaces and proceeding along the walls (Sealy et al, 1985). Increased levels of acid and neutral detergent fibres have been shown to characterise the post-harvest hardening of...

Modifying texture by enzyme addition

The vacuum infusion of enzymes in the structure of fruits and vegetables has been mentioned in connection with designing enzymatically modified food (McArdle and Culver, 1994 Baker and Wicker, 1996 Culver et al., 2000). Enzymatic modification of the internal characteristics of intact fruit or vegetables by vacuum infusion leads to an interesting transfer reaction process in food matrix engineering. The applications of enzyme vacuum infusion appear to be numerous, depending on the specific...

Protein content

Protein content and protein quality are fundamentally associated with cooked pasta textural quality and are considered the most important of all the grain components that influence cooking quality (Autran et al, 1986 D'Egidio et al., 1990 Matsuo et al., 1982). Consequently, a minimum hard vitreous kernel (HVK) content is an important physical characteristic because of its relationship to protein content. Generally, as HVK content increases and non-vitreous (commonly referred to as starchy or...

Physical properties of cooked rice

Texture Analysis Cooked Rice Grains

Among various physical properties, hardness and stickiness are the most frequently tested parameters (Table 19.1). Hardness and stickiness of cooked rice measured with an Instron food tester correlate significantly with amylose content, but because stickiness is easily predictable based on amylose content (r -0.92, p < 0.01), texture measurement concentrates on hardness (r 0.77,p < 0.01) (Perez and Juliano, 1979). The instruments used to determine the hardness and texture profile of cooked...

Potential techniques for jams

The four essential ingredients in manufacturing jams are fruit, pectin, sugar, and acid. Optional ingredients include spice, buffering agents, preservatives, and anti-foaming agents. The exact process selected will depend upon the type of product to be manufactured, the raw materials available, and the scale of production. Traditionally, all of the ingredients are blended together as the first stage of processing however, with modern demands for a high degree of consistency in quality, it has...

Quasistatic loading

Quasi-static methods measure the force at a specific level of deformation, or the deformation at a specific level of force, or both. Force measurement methods require controlling the displacement of the probe during testing so that reliable force measurements can be obtained. Verner (1931) developed a firmness tester for stone fruits, which squeezed the fruit between two flat plates for a specified distance. Ross (1949) reported on a fruit firmness tester that used a pneumatic system to press a...

Application of NIR to cereals and their products

In many cases, cereals undergo a milling or comminution step to reduce their particle size for further processing. The way in which cereals are transformed during this stage is a function of a wide range of physical characteristics including size and shape. However, for a number of cereal species, the texture of the grain determines how the grain will function at subsequent stages of the production chain (Evers and Millar, 2003). Depending on the manifestation of the textural attributes in...

Destructive testing

Sound is produced due to the application of a force on the food product. The cell walls of the product snap and energy is released. It is this energy moving through the air (or other sound medium) which is detected and recorded. Destructive testing has been conducted in two ways via recording the sounds produced by the application of a force on the product either by the teeth (during biting and chewing) or by instrumental shear or compression probes (the instrumental element). To record the...

Vacuum infusion technology 1521 Mass transfer phenomena

Comprehension and control of the mass transfer resulting from the application of VI technology are particularly important with respect to the structural effect required for the food product. Indeed, the nature of the mass transfer determines the quantity of the reactive substance which penetrates into the product, its distribution in the plant structure and the possible structural modifications generated by the vacuum step. Compared to a classical diffusion process (candying, salting, soaking,...

Dipping

Softening caused by freezing-thawing can sometimes be minimized by dipping the tissue in different solutions before freezing. Much of the softening results from degradation of the middle lamella of the walls of cortical cells with increased release of pectins from the cell walls. In many fruit, such as tomato, endo-polygalacturonase begins water solubilization of pectins while exo-polygalacturonase completes hydrolysis (Perkins-Veazie, 1995). Firmness changes in strawberries during senescence...

Trends in consumer preference

When considering consumer preference for pasta textural characteristics the Italian tradition of 'al dente' eating properties, characterized by high degrees of firmness and elasticity, generally first comes to mind. However, it should be realized that this consumer preference is not universal and this must be taken into account when evaluating trends. For example, in countries such as Brazil and Colombia, most but not all consumers prefer pasta with softer textural attributes. This preference...

Quantitative descriptive tests

The Texture Profile Method was developed by the General Foods Company specifically to define and measure the textural parameters of foods. Panellists are selected on the basis of ability to discriminate known textural differences in the specific product application for which the panel is to be trained (solid foods, beverages, semi-solid foods, skin care products, fabrics and paper goods). Panellists selected for training are exposed to a wide range of products from the category under...

Correlation spectrum

Simple correlation coefficients between constituents (textural properties and pectin constituents) and absorbance at each measured wavelength for original intact spectra were improved by second derivative transformation. However, the correlation spectrum of juice spectra did not show any improvement in correlation values. The common three broad bands of the high correlation coefficients between both textural properties and pectin constituents with absorbance at each measured wavelength were...

Controlling PPO and POD activity

A number of technological approaches can be considered to control the activity of PPOs and PODs during the food manufacturing process. 12.5.1 Genetic modification of raw material First of all, manipulating the raw materials may control enzyme activity. Examples for this can be found in for instance the development of a potato variety in which PPO was knocked out via antisense technology (Zabeau et al., 1994), and in button mushroom that was transformed with antisense PPO-constructs (Stoop and...

Crispness and turgor pressure

Whilst crispness is not fully understood as a perception, and cannot yet be measured directly by instrumental means, there is little doubt that the crispness Fig. 10.1 (a) Electron micrograph of a cell wall of Chinese waterchestnut. Abbreviations m middle lamella p primary wall. The cell wall is approximately Fig. 10.1 (a) Electron micrograph of a cell wall of Chinese waterchestnut. Abbreviations m middle lamella p primary wall. The cell wall is approximately Fig. 10.1 (b) Electron micrograph...

Processed fruit firming by infusion of gelling agents

The infusion of gelling agents in the fruit or vegetable structure allows texture improvement either by generating intercellular bridges in the pores complementing the plant cell wall network or by forming bonds between the added hydrocolloids and the cell wall components. However, the intercellular gel can modify the texture response only where the porous structure is high and the solute gain is significant, especially as mass transfer phenomena are generally limited by the high viscosity of...