Human nutrition, protein functions

In general, nonconventional protein foods must be competitive with conventional plant and animal protein sources on the bases of cost delivered to the consumer, nutritional value to humans or animals, functional value in foods, sensory quality, and social and cultural acceptability. Also, requirements of regulatory agencies in different countries for freedom from toxins or toxic residues in single-cell protein products, toxic glycosides in leaf protein products, pathogenic microorganisms, heavy metals and toxins in fish protein concentrates, or inhibitory or toxic peptide components in synthetic peptides must be met before new nonconventional food or feed protein products can be marketed. 

The increasing interest in nutritional and functional properties of soybean protein has promoted their use in the manufacturing of foods for human consumption. Soybean products (particularly infant formulas and soybean dairy-like) may also represent an interesting substitute for infants and people allergic to milk proteins. On the other hand, due to their technological properties and low cost, soybean proteins are increasingly employed as ingredients in milk, bakery, and meat products, in which their addition is forbidden or allowed up to a certain limit. 

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... 

Fats and oils have major roles in human nutrition. They are concentrated dietary sources of energy, providing approximately 9 kcal/g when metabolized compared with 4 kcal/g for carbohydrates and proteins, and account for about 36 percent of domestic caloric intake per capita.19 Dietary lipids also can provide essential molecular structures that are synthesized by the body into compounds required for selective functioning of cell membranes and regulation of life processes. 

Amino acids joined together by peptide bonds form the primary structure of proteins. The amino acid composition establishes the nature of secondary and tertiary structures. These, in turn, significantly influence the functional properties of food proteins and their behavior during processing. Of the 20 amino acids, only about half are essential for human nutrition. The amounts of these essential amino acids present in a protein and their availability determine the nutritional quality of the protein. In general, animal proteins are of higher quality than plant proteins. Plant... 

Vitamins are minor components of foods that play an essential role in human nutrition. Many vitamins are unstable under certain conditions of processing and storage (Table 9-1), and their levels in processed foods, therefore, may be considerably reduced. Synthetic vitamins are used extensively to compensate for these losses and to restore vitamin levels in foods. The vitamins are usually divided into two main groups, the water-soluble and the fat-soluble vitamins. The occurrence of the vitamins in the various food groups is related to their water-or fat-solubility. The relative importance of certain types of foods in supplying some of the important vitamins is shown in Table 9-2. Some vitamins function as part of a coenzyme, without which the enzyme would be ineffective as a biocatalyst. Frequently, such coenzymes are phosphorylated forms of vitamins and play a role in the metabolism of fats, proteins, and carbohydrates. Some vitamins occur in foods as provitamins—compounds that are not vitamins but can be changed by the body into vitamins. Vitamers are members of the same vitamin family. 

Each amino acid has its own distinct function that works with other amino acids to build proteins. The particular combined molecular structures of the amino acids in a protein determine how it works. Of the following twenty amino acids, nine are essential (indicated by an E) in human nutrition, and the remaining eleven (indicated by an N) can be manufactured in the body. 

Nantes was chosen as the location because of its INRA Research Centre, which is renowned for its basic and applied research on plant biopolymers, starch, proteins and cell wall polysaccharides. The main objectives of the Nantes Centre in Plant Science first of all concerns the biosynthesis of macromolecules and assemblies in planta, secondly their structural characteristics and related physico-chemical and functional properties, and thirdly with their behaviour in multiphasic systems in relation to end-uses in food and non-food applications. In addition, human nutrition is also considered. 

The functional properties of food proteins is a subject of considerable interest and importance. For example, in the last two decades much effort has gone into the development of various nonconventional sources of protein. The vast majority of this effort, however, has been concentrated on various aspects of production of economical protein resources and not on the actual utilization of these resources. The result is that many nonconventional protein resources, while they can now be produced fairly easily, can in many cases be produced only in a form lacking desirable functional properties. The point is simply that a protein, even though it may have excellent amino acid balance and all other prerequisites for a nutritionally superior protein, will have no impact on human nutrition unless it has the functional properties necessary for its incorporation into food systems. A specific example of this problem is the case of fish protein concentrate, the utilization of which is severely restricted by its very limited solubility in water. There are, of course, many other examples, but for present purposes it is sufficient to emphasize that there is a real need for the development of chemical, physical, or enzymatic methods that increase the usefulness of proteins in food systems. 

Plant storage proteins are found in high concentrations in seeds, especially in leguminous plants, in which the storage proteins constitute up to 25 percent of the dry weight of the seed. These proteins have no known enzymatic function and often exist within separate vesicles (packets) in the seeds. In addition to their importance to the germinating seed, these plant storage proteins are a valuable source of human nutrition, see also Iron Lipids Nucleic Acids Proteins Toxicity Transport Protein. 

Grundy, 1988). Linoleic acid is an (0-6 FA, which is beneficial in the right amounts, but pro-inflammatory if too much is consumed, as described later. Linolenic acid, an CO-3 FA, is beneficial for heart and cardiovascular function (de-Lorgeril et al., 1994). It has recently received much attention in the United States by nutritionists who are worried about a decreasing ratio of dietary (0-3 to (0-6 FA. The recommended ratio of these FA types is 1 2.3 (Kris-Etherton et al., 2000). The relationship of FA ingestion to nutrition and health is covered in great detail in the Chapter Human Nutrition Value of Soybean Oil and Protein. 

The overall objective of this chapter is to review the past, present, and future role of the sweet potato (Ipomoea batatas [L.] Lam) in human nutrition. Specifically, the chapter describes the role of the sweet potato in human diets outlines the biochemical and nutritional composition of the sweet potato with emphasis on its (3-carotene and anthocyanin contents highlights sweet potato utilization, and its potential as value-added products in human food systems and demonstrates the potential of the sweet potato in the African context. Early records have indicated that the sweet potato is a staple food source for many indigenous populations in Central and South Americas, Ryukyu Island, Africa, the Caribbean, the Maori people, Hawaiians, and Papua New Guineans. Protein contents of sweet potato leaves and roots range from 4.0% to 27.0% and 1.0% to 9.0%, respectively. The sweet potato could be considered as an excellent novel source of natural health-promoting compounds, such as p-carotene and anthocyanins, for the functional food market. 

The importance of amino acids, peptides, and proteins is widely know and it arises from different aspects ranging from an important role in human nutrition and health to different technological functions that can widely influence the quality of food products (mainly for peptides and proteins). Therefore, their analysis is crucial not only from the nutritional point of view (for example, to warranty and verify the content of an specific amino acids) but also for product quality assessment and product development (where information about the composition of the protein fraction is mandatory). Also important is assessment of the authenticity of foods through enantiomer separation and identification. 

Rapeseed proteins possess besides their high nutritional value a distinct functional potential enabling stabilization of emulsions and foams as well as formation of gel-like and other structured systems with high water-binding capacity. Therefore, a lot of new value-added applications in human nutrition, animal feeding (like the use of rapeseed protein concentrates in aquaculture) and for different technical purposes may be expected. 

Van Loon, L. J.C., Y. Boirie, A.R Gijsen, J. Fauquant, A.L. de Ross, A.K. Kies, S. Lemosquet, W.H.M. Sairs and R. Koopman, 2009. The introduction of intrinsically labelled milk protein provides a functional tool for human nutrition research. J. Dairy Sci. 92, 4812-4822. 

Nutrition. Zinc is essential to the proper functioning of plants and animals and, as zinc sulfate and oxide, it is used as a feed supplement (49—51) (see Mineral nutrients Feedsand feed additives). Most crops use less than a kilogram of zinc per 1000 m per year, so that zinc salts added at 1.3—4.5 kg/ha gradually build up the zinc reserve (52). Animals, including humans, store relatively Htde available zinc and, thus, require a constant supply in the diet. For instance, beef cattle require 10—30 mg/kg dry feed, dairy cattle 40 mg/kg, and breeding hens 65 mg/kg. Zinc from plants is considered less available to monogastric aminals than zinc from animal protein. 

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