Structure-Property Relationships in Foods

Even where structure-property relationships are still poorly rmderstood from a fundamental point of view, a vast body of experience exists on how to change the structure to improve the properties. This empiricism is very common in food fabrication. Generations of cooks have produced the recipes used in kitchens throughout the world. However, modem food manufacture cannot rely on or translate much of this knowledge into high volume, efficient food manufacture. 

In foods, stmcture matters because it is responsible for many of the desirable properties, such as appearance, texture, and even flavour release. However, unlike other composites that are designed to provide final physical and mechanical properties from the structure (e.g., load-bearing bridges, impact-resistant fibre composites, etc.), food stmctures must break and fail under chewing action otherwise they are not consumable food. In a sense, physical properties of foods are opposite to those valuable to engineers. The search for relations between the stmcture and physical properties of foods started only in the 1980s. [See e.g., several chapters in Peleg and 

Bagley (1983) and Blanshard and Lillford (1987) dealing with qualitative structure-property relationships in meats, plant foods and baked products]. Evidence is now accumulating that structure does play a key role in controlling many other attributes important in foods beyond their basic physical or engineering properties. For example, structure is critical in texture perception (Hutchings and Lillford 1988), flavor release (Taylor 2002) and the bioavailability of some nutrients (Aguilera 2005). 

In the developed world, the last 10 years have seen the direction of the producer-to-consumer axis reversed. Now consumers expectations largely dictate how foods are produced, processed and delivered as products compete in a well-supplied market. Nowadays additional demands are present either implicitly (e.g., care of animals or fish before slaughter, environmental impact during production, traceability) or explicitly (e.g., convenience, safety, health benefits). This constitutes the new consumer-to-producer axis also described by the term from fork-to-farm. The emerging concerns of consumers for health and well-being ( I am what I eat ) has identified 

Because texture is such an important property in foods, a brief diseussion of its meaning, quantification and implications is presented. The term texture refers to an elusive but important quality attribute of foods that is difficult to measure or analyze. Nevertheless, it is clear that whether testing is performed in our mouth or by an engineering device, what is being measured is the manifestation of the structural 

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Tolstoguzov, V. (1996). Structure-property relationships in foods. In Parris, N., Kato, A., Creamer, L.K., Pearce, J. (Eds). Macromolecular Interactions in Food Technology, ACS Symposium Series No. 650, Washington, D.C. American Chemical Society, pp. 2-14. 

Slade, L., and H. Levine. 1991. A food polymer science approach to structure-property relationships in aqueous food systems. In Water relationships in foods, ed. H. Levine and L. Slade. New York Plenum Press. 

Food polymers and the behaviour of their mixtures are mainly responsible for the structure-properties relationship in both food and chyme. The two basic features of food are that its biopolymers, proteins and polysaccharides are its main construction materials and water is the main medium, solvent and plasticizer. In other words, three components— protein, polysaccharide and water—are the main elements of food structure that are principally responsible for quality of foods (see also Chapter 13). 

Most food biopolymers have limited miscibility on a molecular level and form multicomponent, heterophase and nonequilibrium dispersed systems. A thermodynamic approach is applicable for studying structure-property relationships in formulated foods since their structures are based on nonspecific interactions between components and such thermodynamically based operations as mixing of components, changing temperature and/or pH, underlies processing conditions. 

Aguilera, J.M. (2006). Structure-property relationships in low-moisture products. In M.P. Buera, J. Welti-Chanes, P. Lillford, and H. Corti (eds.). Water Properties of Food Pharmaceutical and Biological Materials. CRC/Taylor and Francis, Boca Raton, FL, pp. 126-127. 

Clark AH (2000) Biopolymer gelation— the structure-property relationship. In Williams PA, Phillips GO (eds) Gums and stabilisers for the food industry—10. The Royal Society of Chemistry, Cambridge, p 91... 

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. 

Gel structures are ubiquitous in foods and responsible for many of their physical properties. The space-filling network of polymers or aggregates provides solidlike properties in the presence of an enormous amormt of water. They are a form of solid water at ambient temperature and in fact they are used to immobilize free water in dietetic products. Gels have been extensively used as model systems to study strue-ture-property relationships due to their simple biphasic nature and the faet that the kinetics of structural changes can be continuously followed by oseiUatory rheometry. 

Among the computational methods available, QSARs, or more general, quantitative structure-property relationships (QSPR) have been widely used not only in drug design and environmental chemistry but also in food-related studies. QSPR studies are grounded in the concept that a property (e.g., biological activity, reactivity, toxicity, volatility, etc.) depends on the molecular structure and that is possible to find a mathematical or quantitative relationship between that property and a suitable molecular representation (e.g., some combination of descriptors). 

Since the 1980s, the polymer science approach to the study of the glassy state, glass transitions, and their importance for structures, properties and water relationships in food materials, products, and processes was recognized by a growing number of food scientists and technologists [6.4.3], As a result, the following questions arose (Chapter 3 in [B.53]) ... 

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