Food properties

NMR is an incredibly versatile tool that can be used for a wide array of applications, including determination of molecular structure, monitoring of molecular dynamics, chemical analysis, and imaging. NMR has found broad application in the food science and food processing areas (Belton et al., 1993, 1995, 1999 Colquhoun and Goodfellow, 1994 Eads, 1999 Gil et al., 1996 Hills, 1998 O Brien, 1992 Schmidt et al., 1996 Webb et al., 1995, 2001). The ability of NMR to quantify food properties and their spatiotemporal variation in a nondestructive, noninvasive manner is especially useful. In turn, these properties can then be related to the safety, stability, and quality of a food (Eads, 1999). Because food materials are transparent to the radio frequency electromagnetic radiation required in an NMR experiment, NMR can be used to probe virtually any type of food sample, from liquids, such as beverages, oils, and broth, to semisolids, such as cheese, mayonnaise, and bread, to solids, such as flour, powdered drink mixes, and potato chips. 

Rahman, S. 1995. Food Properties Handbook . CRC Press, Boca Raton, FL. 

In this level, the fundamental tasks required to convert the raw materials into the final product are identified. All tasks are related to property differences. Siirola (1996) has presented the following hierarchy of property differences molecular identity, amount, composition, phase, temperature/pressure, form. This list of tasks is not very well suited for food properties. Common tasks for food processes are decontamination (e.g. pasteurization and sterilization) and structure formation (e.g. emulsification, size reduction of dispersed phase in an emulsion, crystallization, interfacial adsorption/desorption). 

Secondly, the study of the chemical composition of foods and of its changes on processing are not the only aim (except in control analyses) the space of chemical quantities is intermediate between the cause space, which includes every parameter affecting food composition, and the effect space, where we find variables related to food properties, its quality, sensorial evaluations, nutritional value, and storage possibilities. Generally, the chemical space is described accurately and concisely. 

Rahman, M.S. 1995. Handbook of Food Properties. CRC Press, Boca, Raton, Fla. 

Proteins are important from the nutritional and technological points of view. Proteins affect every property that characterizes a living organism, and they play different roles in the human body. Proteins are also very important in food technology and are responsible for many food properties. The physical properties of proteins and their interactions with other components contribute significantly to the functional behavior and quality of several food products, such as cheese, bread, and meat products (9). An overview of the functional roles of proteins in different food systems is presented in Table 2. Food preferences by human beings are based not on nutritional quality but on sensory attributes to the food, such as appearance, color, flavor, texture, and... 

The temperature dependence of the dielectric properties of foods has been extensively measured and reviewed by Bengtsson and Risman (1971) and Buffler (1993). Mudgett et al. (1977) has pioneered the prediction of dielectric properties of foods as a function of constituency and temperature. Prediction of the temperature behavior of dielectric properties is crucial for accurate mathematical modeling of foods. Many workers today still use constant room temperature values or a look-up table at best. In the author s opinion, dielectric prediction of food properties is still a very fertile and useful research field. 

The author is grateful to Keith Langley for information and assistance on instrumental methods for measuring food properties, and for preparation of force deformation diagrams in Fig 4., and also to Alan Martin for preparation of samples and examination by SEM. 

Unlike light-scattering studies, for which dilution is often a prerequisite, ultrasound can measure food properties at concentrations that are technologically relevant. This aspect has obvious benefits for the analysis of inhomogeneous foods such as solidifying fats, dynamically changing dairy food systems, dough, and emulsions. 

The nature of the colloidal dispersion can have important influences on other food properties. For example, a 50/50 % emulsion of oil (fat) and water has a very different thermal properties in O/W versus W/O form. The O/W emulsion would be expected to have the greater thermal conductivity, water being the external phase and, other factors being equal, should freeze at a faster rate [811]. O/W food emulsions tend to be quite fluid, whereas W/O food emulsions tend to be more viscous, sometimes solid-like. 

The concept food quality includes multiple aspects of food. Because this term is not a completely objective parameter, the consideration of appropriate quality will strongly depend on the food, in particular, on the product itself, or even on the consumer. Among the aspects related to food quality, food composition, aroma, flavor, taste, or food properties can be pointed out. For this reason, assessing food quality is a complex task that may imply different types of analysis depending on the particular food or product. As in other fields of food science, as the complexity increases, Foodomics approaches are gaining attention (39). 

Szczesniak, A. S. (1983). Physical properties of foods what they are and their relation to other food properties. In Physical Properties of Foods, Peleg, M., and Bagley, E. B. (Eds.), pp. 1-41. AVI Press, New York. 

These nonenzymatic reactions are responsible for numerous changes on food properties and may impair food safety. Although these reactions are of great importance in the production of aroma, taste and color, they are often accompanied by a reduction of the nutritive value of different foods and by the formation of toxic compounds harmful for human health (Ledl and Schleicher, 1990). Results of nonenzymatic browning can be either desirable or undesirable. The brown crust formation on bread is desirable the brown discoloration of evaporated and sterilized milk is undesirable. For products in which the browning reaction is favorable, the resulting color and flavor characteristics are generally experienced as pleasant. In other products, color and flavor may become quite unpleasant. 

In the area of water as a food component, the issue of the glass transition has received much attention. This demonstrates the important role of water in food properties. Lipids have received much attention lately mainly because of publicity related to nutritional problems. Sutructured... 

Figure 8-46 Relationship Between Water Activity and Crispness of Popcorn. Source. Reprinted with permission from E.E. Katz and T.P. Labuza, Effect of Water Activity on the Sensory Crispness and Mechanical Deformation of Snack Food Properties, J. Food Sci., Vol. 46, p. 403, 1981, Institute of Food Technologists.

Katz, E.E., and T.P. Labuza. 1981. Effect of water activity on the sensory crispness and mechanical deformation of snack food properties. J. Food Sci. 46 403-409. 

The interface between crystals and the rest of the food matrix is another important concern in governing food properties. As noted in the previous section, the hydrophilic nature of sugar crystals in melted chocolate dramatically impacts fluid viscosity, as does the effect of modifying that interface through addition of an emulsifier. 

The next area of future development is microstructure analysis. Although numerous attempts have been made to connect crystal stmcture to food texture, a long road still remains ahead before it can be said that a certain type of stmcture leads definitively to certain mechanical properties. Development of methodologies for structure analysis and further developments in analytical modeling of crystalline microstructure are needed. Further, the connection between these microstructural models and food properties related to the crystalline microstructure are important. 

Chapter 11 deals with methods and techniques used to examine the microstructure of foods. In trying to relate micro structure and food properties the main problem is selecting the relevant scale at which elements interact to produce a given behavior or... 

Chamberlain, E. K., Rao, M. A., and Cohen, C. 1998. Shear thinning and antithixotropic behavior of a heated cross-linked waxy maize starch dispersion. Int. J. Food Properties 2 63-77 errata, 2 195-196. 

Operating areas of multifunctional food ingredients due to food properties and quality ... 

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