Food protein ingredients functionality

Lanier, T.C., Functional food protein ingredients from fish, in Seafood Proteins, Sikorski, Z.E., Pan, B.S., and Shahidi, F., Eds., Chapman Hall, New York, 1994, chap. 10. 

Table 2 Functional Requirements of Food Protein Ingredients...

As stated previously, the functional performance of food proteins as ingredients is dictated by surface characteristics, including hydropho-bicity, electrostatic, and steric parameters [100]. All of these properties can be modified by the processing utilized to provide a concentrated food protein ingredient. Although the process modification that influences the functionality of a food protein will be specific to the type of protein processed, there are some general characteristics that apply equally to all common food proteins. These include... 

Whole oilseeds and legumes and their derivatives (defatted flours, and protein concentrates and isolates) are used in traditional foods as sources of protein and for their texture-modifying functions. This article reviews, on a comparative basis, processes for preparation of vegetable food proteins, compositions and characteristics of the resulting food ingredients, and their functionalities and uses in traditional foods. 

Protein is utilized in many foods for the particular characteristics that it contributes to the final product (1 ). In order for protein products to maintain or enhance the quality and acceptability of a food, the protein ingredients should possess certain functional properties that are compatible with the other ingredients and environmental conditions of the food system. Consequently, an important aspect of the development of new protein additives and their incorporation into food systems is the establishment of their functional properties. Functional properties of proteins are physicochemical properties through which they contribute to the characteristics of food. Study of functionality should provide information as to how a protein additive will perform in a food system (, A). These properties are... 

Relationships with other properties. In any food system and possibly in simple systems, the protein ingredient is likely to perform several functions, most of which are being discussed in... 

Milk protein products. As indicated in Table 1, the food industry is placing major emphasis on the production and utilization of milk protein products in a wide variety of formulated food products (20,21,22). Although nonfat dry milk (NFDM) and whey powder are major milk protein ingredients in formulated foods, casein and whey protein concentrates, which contain their proteins in a more highly concentrated and functional form, are essential for certain food product applications, such as those products that require the proteins as an emulsifier agent. Additional details on the processing methods and conditions used to produce the various milk protein products are available (23). 

Genovese MI, Barbosa AC, Pinto Mda S, Lajolo FM. 2007. Commercial soy protein ingredients as isoflavone sources for functional foods. Plant Foods Hum Nutr 62 53-58. 

Meisel, H. and Schlimme, E. 1996. Bioactive peptides derived from milk proteins ingredient for functional foods Kieler Milchwirtsch. Forschungsber. 48, 343-357. 

Hphe importance of studying protein functionality is stressed as world-wide demand for functional proteins usable as food ingredients has increased in recent years. Hammonds and Call (1) estimated the maximum market potential for protein ingredients at approximately 3.1 billion pounds annually. Kinsella (2) stated that about 80% of this quantity has to possess a high degree of functionality. 

There are large resources of potential food proteins (oilseed, yeast, leaf) which are presently unexploited. With the application of innovative scientific and technological methods these can become significant sources of food protein. In developing ingredient protein from plant sources, research emphasis must include studies to determine the physicochemical or functional properties of these proteins. 

Many processes used for extracting and preparing novel proteins cause denaturation, insolubilization and loss of functional properties. Because of this the development of practical procedures for the modification of these non-functional proteins to impart some functional properties is needed. Such, modification can amplify the uses of these protein, facilitate the simulation of traditional foods, improve compatibility between protein ingredients and aid food manufacturing and processing. 

Ideally microbial cells should be consumable directly as food or food ingredients. However, because of their nucleic acid content the presence of undesirable physiologically active components the deleterious effects of cell wall material on protein bioavailability and the lack of requisite and discrete functional properties, rupture of cells and extraction of the protein is a necessary step. Importantly, for many food uses (particularly as a functional protein ingredient) an undenatured protein is required. For these reasons and for many potential applications of yeast protein(s) it is very desirable to separate cell wall material and RNA from the protein(s) for food applications. Much research is needed to develop a practical method for isolation of intact, undenatured yeast proteins from the yeast cell wall material to ensure the requisite nutritional and functional properties. 

To achieve success as protein ingredients for food formulation and fabrication, novel proteins should possess a range of functional properties. Frequently during extraction, refining and drying, plant and yeast proteins, intended for food uses, become denatured or altered and subsequently display poor functional properties which render them of limited use. Chemical modification provides a feasible method for improving the functional properties of plant and yeast proteins and potentially may make it possible to tailor proteins with very specific functional properties. In this review the information on modified plant proteins is reviewed and the use of succinylation for the recovery of yeast proteins with low nucleic acid is described. 

Application of membrane processes during production of purified food proteins is a mild treatment which ensures that the functional properties of the native proteins are retained. (1 ) These properties are mostly found to be superior to those of denatured proteins. However, not all possible needs of the modern food industry are fulfilled by using native proteins instead of denatured ones. Therefore, enzymatic modification of proteins has been demonstrated as a possible means of meeting the needs of the food industry for high-quality protein ingredients ( ), (13), (14). 

The first soybean protein ingredients made commercially available for food use included full-fat and defatted soy flours and grits (3, 7, 8). These products contain ca. 46-59% protein (NX 6.25) on a moisture-free basis and are available with various heat treatments for specific end-use. Soy protein concentrates and soy protein isolates were introduced into the market about 15 years ago (3, 9, 10, II). By definition soy protein concentrates must contain no less than 70% protein (N X 6.25) and isolates no less than 90% protein (N X 6.25), all on a moisure-free basis. In the past several years there has been much activity in the commercialization of textured soy protein products intended for the extension and replacement of meat. These textured products may be obtained through fiber spinning, shred formation, extrusion, or compaction (12, 13, 14, 15). In addition, soybean milk solids and the heterogeneous proteins in soybean whey might serve as useful substrates in chemical modifications for food use. This short recitation of commercial products illustrates the type of crude protein fractions available for practical modification. Many useful functional properties have been ascribed to these new food proteins. 

Food proteins, especially those of plant origin, often require modification to achieve desirable functional properties for use as food ingredients. For instance, soy protein has limited water solubility at acid pH, which restricts its use in acidic foods such as coffee whitener and acidic beverages. Improved solubility at acid pH for commercial soy protein isolate can generally be achieved by hydrolysis. However, the hydrolysis has to be carefully controlled, because excessive peptide bond hydrolysis may release bitter peptides, resulting in undesirable off-flavors. Scientists are constantly looking for better and safer methods to improve the functional properties of protein to meet the needs of the food industry. 

Protein-based ingredients contribute to the enhancement of food texture, flavor, and eye appeal [130], Functionality of protein ingredients can be enhanced also by enzymatic modifications. The factors influencing the choice of an appropriate enzyme for improvement of functional properties of proteins are as follows specificity of the enzyme, conformation of the protein, pH optimum, presence of activators and/or inhibitors, availability, thermostability, and financial causes. 

Food proteins are important in determining the characteristics of many food products. Frequently the protein used influences more than one characteristic of the food. The protein selected will vary as a function of the protein, the formulation of the food, and the processing of the product. The most common proteins used as food ingredients include egg proteins [83,84], soy proteins [85,86], milk proteins [87,88,89], wheat gluten [90], and fish proteins [91]. Other proteins have been used to a lesser degree and include rapeseed protein, sunflower protein, pea protein, cottonseed protein, peanut protein, and blood plasma. 

Morr [97] has listed a number of requirements related to different properties of proteins as food ingredients, as indicated in Table 2. The major functional properties of food proteins that influence their choice in specific applications are emulsification, aeration/foam formation, gelation, solubility/water binding, dispersibiliy, film formation (cohesion/adhesion), heat stability, and acid stability. 

Differences in the major food proteins that influence their application as food ingredients reflect the intrinsic characteristics of those proteins. Tabulation of some of these differences that impact on the type of food in which they may be used is shown in Table 4. In addition to general functional properties, proteins to be used as food ingredients must also be easy to use, neither impart flavor nor change the... 

In addition to containing a combination of individual proteins, protein ingredients generally include lipid, carbohydrate, and minerals to varying degrees, which can modify the performance of the product in food applications. Composition may vary as a function of the breed/variety, the season of the year, and the process used to obtain the protein ingredient. Commercial suppliers of proteins provide a range of protein products that have been prepared for different applications. The proprietary product Simplesse represents a process-modified protein where microparticulation is claimed to provide textural attributes useful in fat simulation. However, frequently, the differences are related to variations in chemical composition. 

For any specific food product that uses a protein as a functional ingredient, the general formulation and the processing environment dictate how the protein will function. Most formulated protein-based foods include, in varying concentrations, protein, lipid, simple carbohydrates as sweeteners, complex carbohydrates as stabilizers, small molecular weight emulsifiers, and minerals (salts). 

These few examples demonstrate the difficulty faced by food processors in the selection of functional ingredients. There are no simple rules that can be applied to the selection of a given protein ingredient... 

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