Proteins for foods, in addition to providing nutrition, should also possess specific functional properties that facilitate processing and serve as the basis of product performance. Functional properties of proteins for foods connote the physicochemical properties which govern the behavior of protein in foods. This general article collates the published information concerning the major functional properties of food proteins, e.g., solubility, binding properties, surfactant properties, viscogenic texturizing characteristics, etc. The effects of extraction and processing on functional properties and possible correlations between structure and function are discussed, in relation to practical performance in food systems. Modification of proteins to improve functional characteristics is briefly mentioned.

Functional properties of proteins in foods: A survey

Summary Flavours can be among the most valuable ingredients in any food formula. Even small amounts of some aroma substance can be expensive, and because they are usually delicate and volatile, preserving them is often a top concern of food manufacturers. Encapsulation describes different processes to cover an active compound with a protective wall material and it can be employed to treat flavours so as to impart some degree of protection against evaporation, reaction, or migration in a food. Encapsulation of flavours has been attempted and commercialized using many different methods such as spray drying, spray chilling or spray cooling, extrusion, freeze drying, coacervation and molecular inclusion. The choice of appropriate microencapsulation technique depends upon the end use of the product and the processing conditions involved in the manufacturing product. This overview describes each method cited above in terms of the basic chemical and/or physical principles involved and covers mechanisms of flavour release from food matrices.

Flavour encapsulation and controlled release - a review.

There is an increased interest in the role that some nutrients may play in preventing or ameliorating the effect of major diseases (for example, some types of cancer, cardiovascular diseases, eye disorders, among others). In this respect, the bioavailability or the proportion of an ingested nutrient that is made available (that is, delivered to the bloodstream) for its intended mode of action is more relevant than the total amount present in the original food. Disruption of the natural matrix or the microstructure created during processing may influence the release, transformation, and subsequent absorption of some nutrients in the digestive tract. Alternatively, extracts of bioactive molecules (for example, nutraceuticals) and beneficial microorganisms may be protected during their transit in the digestive system to the absorption sites by encapsulation in designed matrices. This review summarizes relevant in vivo and in vitro methods used to assess the bioavailability of some nutrients (mostly phytochemicals), types of microstructural changes imparted by processing and during food ingestion that are relevant in matrix-nutrient interactions, and their effect on the bioavailability of selected nutrients.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1750-3841.2007.00274.x

Food microstructure affects the bioavailability of several nutrients.

Microencapsulation is a relatively new technology that is used for protection, stabilization, and slow release of food ingredients. The encapsulating or wall materials used generally consist of starch, starch derivatives, proteins, gums, lipids, or any combination of them. Methods of encapsulation of food ingredients include spray-drying, freeze-drying, fluidized bed-coating, extrusion, cocrystallization, molecular inclusion, and coacervation. This paper reviews techniques for preparation of microencapsulated food ingredients and choices of coating material. Characterization of microcapsules, mechanisms of controlled release, and efficiency of protection/stabilization of encapsulated food ingredients are also presented.

Encapsulation of food ingredients

Microbial exopolysaccharides are biothickeners that can be added to a wide variety of food products, where they serve as viscosifying, stabilizing, emulsifying or gelling agents. Numerous exopolysaccharides with different composition, size and structure are synthesized by lactic acid bacteria. The heteropolysaccharides from both mesophilic and thermophilic lactic acid bacteria have received renewed interest recently. Structural analysis combined with rheological studies revealed that there is considerable variation among the different exopolysaccharides; some of them exhibit remarkable thickening and shear-thinning properties and display high intrinsic viscosities. Hence, several slime-producing lactic acid bacterium strains and their biopolymers have interesting functional and technological properties, which may be exploited towards different products, in particular, natural fermented milks. However, information on the biosynthesis, molecular organization and fermentation conditions is rather scarce, and the kinetics of exopolysaccharide formation are poorly described. Moreover, the production of exopolysaccharides is low and often unstable, and their downstream processing is difficult. This review particularly deals with microbiological, biochemical and technological aspects of heteropolysaccharides from, and their production by, lactic acid bacteria. The chemical composition and structure, the biosynthesis, genetics and molecular organization, the nutritional and physiological aspects, the process technology, and both food additive and in situ applications (in particular in yogurt) of heterotype exopolysaccharides from lactic acid bacteria are described. Where appropriate, suggestions are made for strain improvement, enhanced productivities and advanced modification and production processes (involving enzyme and/or fermentation technology) that may contribute to the economic soundness of applications with this promising group of biomolecules.

Heteropolysaccharides from lactic acid bacteria.

Microscopy and imaging techniques are the most appropriate techniques for evaluating food structure because they are the only analytical methods that produce results in the form of images rather than numbers. However, images may now also be converted into numerical data to allow for statistical evaluation. Advances in microscopy and imaging techniques are made, for the most part, outside the field of food science, drawing from the fields of materials science, biology and medicine. Such techniques cannot, in most cases, be directly applied to study food structure. They must be adapted because the processing conditions that turn biological raw materials into food cause structural and textural changes which, in turn, change the innate properties and behaviour of the foods. This necessitates the development of appropriate methods and also the specialization of researchers. Future developments in this field can be divided into the use of new equipment developed for use in other fields, and the application of techniques modified to solve specific food science problems, such as the development of new foods with particular properties and texture or the detection of defects in foods.

Microscopy and other imaging techniques in food structure analysis

Reduced-fat cheese (17% fat, 44% moisture) was considerably firmer and more elastic than full-fat cheese (35% fat, 35% moisture), even though the moisture levels in the nonfat matter (MNFM) of the cheese were the same, at 54%. Electron microscopy and compositional analysis revealed about 30% more protein matrix in the reduced-fat cheese. Apparently more of this matrix must be cut or deformed in sensorial and texture assessments. A practical implication is that MNFM should be slightly higher in the reduced-fat cheese than in full-fat cheese to achieve more similar texture.



Homogenization of milk tended to increase the moisture content and decrease firmness and elasticity, but not markedly. The smaller fat globules, per se, did not apparently affect texture as measured in these experiments. Curd granule junctions were prominent in nonhomogenized-milk cheese, because large fat globules were lost at the granule surfaces leaving protein-dense junctions; those in homogenized-milk cheese were less apparent because the protein-dense areas, which resulted from the loss of small fat globules, were narrower.



Sensory and textural parameters for firmness and elasticity were inter-correlated. The Bite Test was more useful than Instron measurements of deformation (20%), apparently because the latter was markedly affected by a slight openness in the cheese.

Milk gel structure. x. texture and microstructure in cheddar cheese made from whole milk and from homogenized low-fat milk

Microstructure and Meltability of Model Process Cheese Made with Rennet and Acid Casein

Processed cheese is produced by blending shredded natural cheeses of different types and degrees of maturity with emulsifying agents, and by heating the blend under a partial vacuum with constant agitation until a homogeneous mass is obtained. In addition to natural cheeses, other dairy and non-dairy ingredients may be included in the blend.

Miloslav Kalab

Papers

Microscopy and other imaging techniques in food structure analysis

Milk gel structure. x. texture and microstructure in cheddar cheese made from whole milk and from homogenized low-fat milk

Microstructure and Meltability of Model Process Cheese Made with Rennet and Acid Casein

Processed cheese products.

Microstructure of Yogurt Stabilized with Milk Proteins