Food texture instrumental measurement

Peleg, M. 1987. The basics of solid food rheology. In Food Texture Instrumental and Sensory Measurement (H.R. Moskowitz, ed.) pp. 3-33. Marcel Dekker, New York. 

Food Texture Instrumental and Sensory Measurement, edited by Howard R. Moskowitz... 

Food texture is measured by sensory analysis or by an instrumental method. Using a human inspector for a textural evaluation is subject to some errors because of variations in perception, even when trained panelists are used and a well-defined standard is referenced. However, Katz and Labuza (1981) compared sensory results and cohesiveness values from force-deformation curves for potato chips, popcorn, puffed corn curls as well as saltines, and obtained a good agreement between the two sets of data. A similar comparison was made by van Loon et al. (2007) for the crispness of French fries comparable results were also noted. 

Feeding and texture of food (meeting), Vincent J.F.V, Cambridge UP, 1991, 60 Food texture measurement and perception, Rosenthal A.J, Aspen PubL, 1999, 142 Food texture Instrumental and sensory measurement (meeting), Moskowitz H.R,... 

Voisey, P. W. Instrumental Measurement of Food Texture, in "Rheology and Texture in Food Quality," J. M. de Man,... 

Voisey, P.W. and deMan, J.M. 1976. Applications of instruments for measuring food texture. In Rheology and Texture In Food Quality (J.M. deMan, RW. Voisey, V.F. Rasper, and D.W. Stanley, eds.) pp. 142-243. AVI Publishing Company, Westport, Conn. 

Clearly, it may be possible to define and accurately measure many aspects of the mechanical and rheological properties of foods, but to try and relate these measures to consumer perceptions of the texture of the foods, is fraught with difficulties. Conversely, it is possible to train human subjects to assess textural characteristics of foods in defined and consistent ways (training them to mimic an instrumental response), however this may be missing the diversity of perceptions of food texture experienced by normal consumers. 

There would be considerable advantage for both sensory scientists and the food industry in knowing what consumers are measuring in order to assess particular textural properties. Despite many real advances in the instrumental measurement of food texture, we are not significantly closer to understanding the sensory cues used in consumer assessment of texture. The mastication process is adjusted to the consistency of the food bolus in real time. From studies of this process is emerging a novel approach to characterisation of food texture. 

Since sensory and mechanical properties of a food depend on its microstructure, the knowledge of microstructure must precede any operation aimed to the attainment of a specific texture (Ding and Gunasekaran, 1998). The instrumental measurements of mechanical and rheological properties represent the food responses to the forces acting on the food structure and, for this reason, are affected by the way in which these analyses are performed. Furthermore, mechanical and rheological tests are always destructive and make impossible the execution of other analyses. 

In-line/on-line feedback control of color of food during processing can improve not only color quality but also color related quality such as texture and appearance. To do this, there are three major aspects development of an in-line/on-line color sensor understanding of color change kinetics and establish correlations between instrumental measured and sensory panel perceived colors of foods. In this research, we have chosen color machine vision technology for the measurement of colors of food due to its superior spatial resolution over conventional instruments such as colorimeter or spectrophotometer. Relationships between measured colors and corresponding principal chemical markers were established for the model food systems. We have also found excellent correlations between the color machine vision system (CMVS) measured and a sensory panel determined colors of food samples (Ling and Tepper, 1995). We believed that a CMVS can be used for food process control to ensure color quality as perceived by consumers. 

There is no universally good adhesive for food constituents. Proteins that are highly cohesive may not blend well with certain other ingredients. It is necessary to examine the available proteins for optimum properties and to select the most satisfactory ingredient combinations. A number of instruments are available for measurements of textural properties of food ingredients or products, but the final criteria for acceptable performance must be taste-panel evaluations. 

An important aspect of food processing, common with other processing industries, is yield of finished product from starting raw materials for any shift and for specific unit operations. Computer-integrated manufacturing can start with the measurement of material flows and build upon this information. Instrumentation for the on-line measurement of specific food qualities of importance lo the consumer such as Food flavor, aroma, texture, and microbial content arc under development. These quality factors... 

Some basic food analytical methods such as determination of °brix, pH, titratable acidity, total proteins and total lipids are basic to food analysis and grounded in procedures which have had wide-spread acceptance for a long time. Others such as analysis of cell-wall polysaccharides, analysis of aroma volatiles, and compressive measurement of solids and semi-solids, require use of advanced chemical and physical methods and sophisticated instrumentation. In organizing the Handbook of Food Analytical Chemistry we chose to categorize on a disciplinary rather than a commodity basis. Included are chapters on water, proteins, enzymes, lipids, carbohydrates, colors, flavors texture/ rheology and bioactive food components. We have made an effort to select methods that are applicable to all commodities. However, it is impossible to address the unique and special criteria required for analysis of all commodities and all processed forms. There are several professional and trade organizations which focus on their specific commodities, e.g., cereals, wines, lipids, fisheries, and meats. Their methods manuals and professional journals should be consulted, particularly for specialized, commodity-specific analyses. 

Kilcast, D. and Eves, A. (1993). Modem methods of texture measurement. In Instrumentation and sensors for the food industry, (ed.) Kress-Rogers, E. Butterworth and Heinemann. pp 349-372. 

Because most foods are complex disperse systems, there are great difficulties in establishing objective criteria for texture measurement. It is also difficult in many cases to relate results obtained by instrumental techniques of measurement to the type of response obtained by sensory panel tests. 

Figure 8-26 Effect of Sample Weight on Maximum Force Registered with the Shear Press and Using the 10-Blade Standard Cell. (1) White bread and sponge cake, (2) raw apples and cooked white beans, (3) canned beets and peas and frozen peas. Source From A.S. Szczesniak, Instrumental Methods of Texture Measurements, in Texture Measurement of Foods, A. Kramer and A.S. Szczesniak, eds., 1973, D. Reidel Publishing Co.

Notwithstanding all the limitations involved, the continuous improvement in precision and reproducibility of physical measurement equipment that relate to parameters perceived by human subjects make their use straightforward and they can provide consistent results. It is important to keep in mind that although instruments allow precise and objective measurements if applied to whole foods, they only can account for the initial structural properties contributing to texture perception. A correlative approach using sensory and instrumental techniques is often necessary. Indeed, there is no reason to determine accurately a mechanical property if it is not relevant to human sensory perception. Sensory methods become essential when calibrating instrumental equipment and are fundamental in product development, especially at early stages. 

Following Scott Blair s (11) classification of instruments for the study of texture, the instruments for measuring the flow properties of fluid foods can be classified into the categories (1) fundamental, (2) empirical, and (3) imitative. Fundamental tests measure well defined properties utilizing geometries that are amenable to analysis of fluid flow. Empirical tests measure parameters that are not clearly defined, but the parameters have been shown to be useful from past experience. Imitative tests measure properties under test conditions similar to those in practice (11) ... 

In recent years various test instruments have been developed to measure texture of a number of food products. Some of these instruments also have been used to test jellies. One of these is the Voland Stevens Texture Analyzer (Fig. 4). 

Moore JN, Janick J (1983) Methods in fruit breeding. Purdue University Press, West Lafayette, IN Rettke M (1993) Prediction the storage life of dried apricots. ADFA News, Australia Roberston GL, Koopmanschap EA, Scrivens CA (1984) Comparison of instruments and sensory panel methods for measuring kiwifruit firmness. J Texture Stud 15 275-283 Sould J (1985) Glossary for horticultural crops. John Wiley, New York, pp 570-582 Southgate DAT (1991) Determination of food carbohydrates. Elsevier Applied Science, London, pp 144-148... 

---