Food materials structuring process

During the process, the solute diffuses into the intercellular space and, depending on the characteristics of the solute, it may pass through the membrane and enter the intracellular space. Differences in chemical potentials of water and solutes in the system result in fluxes of several components of the material and solution water drain and solute uptake are the two main simultaneous flows. Together with the changes in chemical composition of the food material, structural changes such as shrinkage, porosity reduction, and cell collapse take place and influence mass transfer behavior in the tissue. 

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. 

Table II gives the results of residual trypsin inhibitor levels for the various soymilk preparations. The 90 and 120 sec microwave treatments were the most effective in inactivating the trypsin inhibitor complex while hot water treated and unheated samples showed the highest levels. It is not surprising to find that microwave processing is more efficient than hot water in suppressing trypsin inhibitor considering the rapid penetration of food material by microwaves and the susceptibility of protein action to small heat induced changes in tertiary structure. Hence, Collins and McCarty (12) found microwaves produced a more rapid destruction of endogenous potato enzymes (polyphenol oxidase and peroxidase) than hot water heating.

We note from all this prior work that structure at the macro, micro, nano and molecular levels of organisation will all be important. Secondly, the properties of the composite food product will not be related simply to a list of its components (the recipe), since different structural forms can be assembled from the same components by different processes. Emphasis on structure and its origin discriminates food materials science from the former descriptive approach of formulation/process empiricism embodied in most recipes. 

Food materials science is a search for basic knowledge about properties and their relation to structure. In many cases causal connections have been found between key structural features and product behavior or processing parameters (Table 12.1). Understanding the mechanisms and the science behind structure-property relationships would accelerate the prototyping stages, shorten times of product and process development, and reduce costs. 

Flavor Release Flavor release is the process whereby flavor molecules move out of a food and into the surrounding saliva or vapor phase during mastication (126, 127). The release of flavors from a food material occurs under extremely complex and dynamic conditions (136). A food usually spends a relatively short period (typically 1 to 30 seconds) in the mouth before being swallowed. During this period, it is diluted with saliva, experiences temperature changes, and is subjected to a variety of mechanical forces. Mastication may therefore cause dramatic changes in the structural characteristics of a food emulsion. 

Various processes may be used to alter the size and structure of food materials at various length scales and this has the potential to modulate the self-assembly behavior of food components and alter functionality. 

Polysaccharides, proteins, and lipids are involved in different structures of the plant and animal tissues used for food. The structures built from these materials are responsible for the form and tensile strength of the tissues and create the necessary conditions for the metabolic processes to occur. Compartmentation resulting from these structures plays a crucial biological role in the organisms. Some other saccharides, proteins, and lipids are stored for reserve purposes. Other constituents are either bound to different cell structures or distributed in soluble form in the tissue fluids. 

The glass transition processes in foods may result from a rapid removal of water from solids. Based on that, e.g., the Tg values of anhydrous polysaccharides are high, and the food materials may decompose at temperatures below Tg (Kokini et al 1994 Roos and Karel, 1991b). The glass temperature transition affects viscosity, stickiness, crispness, collapse, crystallization, and ice formation, and can strongly influence deteriorative reaction rates. This provides a new theoretical and experimental framework for the study of food systems to unify structural and functional aspects of foods, described in terms of water dynamics and glass dynamics. 

Water, saccharides, lipids, proteins, and minerals — the main components — form the structure of and are responsible for the sensory and nutritional properties of foods. Other constituents, present in lower quantities, especially colorants, flavor compounds, vitamins, probiotics, and additives, also contribute to different aspects of food quality. The catabolysis that takes place in raw materials postharvest, as well as chemical and biochemical changes and interactions of components during storage and processing, affect all aspects of food quality. These processes can be effectively controlled by the food processor who knows food chemistry. 

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