Oilseed protein concentrates and isolates

Much attention has been focused on the oilseed crops as an alternate and largely untapped source of food protein in an endeavor to provide needed nourishment for large segments of the world’s expanding population. A significant part of this attention has been devoted to the practical concentration and isolation of the proteins of several oilseeds. As a result of intensive effort during the last decade, soy protein concentrates and isolates are now commercial commodities which are gaining increasing acceptance as useful functional and nutritional ingredients for food. This report is concerned with a brief review of the commercial processing, product characteristics and food utilization of soy protein concentrates and isolates. In addition, pertinent comments on the concentrates and isolates of other oilseed are included. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Soy flour and grits for use in food products

Processing alternatives enable the soybean processor to manufacture soy flour products which vary in fat content, granulation and degree of heat treatment. By controlling these variables, the processor is able to regulate the nutritional value and functional properties of these products. The application of soy flour products is dependent upon their functional properties, nutritional value and low cost. Currently, the major markets for soy flour and grits are in pet foods and animal feeds, cereal based foods and ingredients, meat based foods, and as a substrate for refined protein products such as the textured vegetable proteins, soy protein concentrates, isolates and hydrolysates. These soy protein products are generally marketed as functional and nutritional substitutes for meat, milk and egg protein. For example, soy flour is a functional replacement for milk in many cereal-based foods, e.g., bread, and also enhances the nutritional value of the cereal protein by supplying lysine to the formulation. The United States government has pioneered the development and marketing of protein-enriched, cereal-based foods designed to combat worldwide starvation. The government has directly supported the research and development of corn and wheat-based food substrates supplemented with soy flour, and has purchased over one billion pounds of these products since 1966 for worldwide distribution. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Textured and shaped oilseed protein food products

The major emphasis in developing textured and shaped protein foods has been with the use of soy proteins. The availability at a low stable price, the high protein content and quality, and the inherent chemical properties of the protein allowing for unique structure development are major reasons for its strong world-wide use. The changing economic trends of many basic protein foods are creating a need for the use of unique textured proteins either as ingredients in existing foods or allowing improved functionality in new products. The two main procedures for texturing and shaping oilseed protein are spinning of protein isolates, and direct extrusion of flour. The spinning technique is more expensive and has greater product functionality in contrast to the direct extrusion method. Consumer acceptance is in large part correlated with the technological success of imparting desirable colors, flavors and textural properties in the finished food product. Examples of these variations are given. The use level of these textured proteins, particularly in meat products, are restricted by labeling standards. The present regulations are not clearly defined. Current proposals for labeling textured vegetable proteins when used with meat products involve standards on a ratio to meat basis. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Associative structures of polyglycerol esters in food emulsions

Liquid crystalline types and the crystalline gel state of the commercially available tri- and octaglycerol esters are identified. The behavior of crystalline and liquid crystalline forms of these polyglycerol esters were studied in water dispersions, soybean oil and water emulsions, and in food emulsions. Triglycerol monoesters, primarily a mixed ester composition of palmitate and oleate, show hexagonal liquid crystalline activity as well as limited regions of stable α crystalline gels. Octaglycerol monostearate and monooleate primarily exhibit hexagonal liquid crystalline behavior which (below their Krafft point) form stable α-gels. A relationship between the associative structures and functional performance of these polyglycerol esters in food emulsions is presented. Presented at the ISF-AOCS World Congress, April 1980, New York.     

Food uses for cottonseed protein

Cottonseed, available in many countries located in both temperate and tropical climates, is rarely used as a source of edible protein even though its use as food was suggested as carly as 1876. Development of edible protein products from cottonseed has been impeded by the presence of gossypol-containing pigment glands in the kernels, and the economic value of the oil. Cottonseed flour produced by mechanical pressing has been marketed in limited quantities as two edible protein products. One, known as “Proflo,” is used primarily to impart functional characteristics to baked and confectionery products. The other is used as an ingredient in “Incaparina” to combat malnutrition in Latin America. Because of the manner in which these cottonseed protein products are processed, their full nutritional and functional potentials and versatiliity have not been realized. Recent advances in breeding glandless cottonseed, processing glanded cottonseed (e.g., the liquid cyclone process), and related technology have increased the potential of cottonseed protein for food uses. Flours, concentrates, and isolates differ qualitatively and quantitatively in protein and amino acid composition. Consequently, they have different functional and nutritional characteristics and end uses. Flours and concentrates as well as their texturized counterparts are acceptable as functional and nutritional additives to meat products, baked goods, and cereals. Three isolates including storage protein, nonstorage protein, and a mixture of both have been prepared from flours and concentrates. The storage protein isolate imparts functional characteristics, such as texture, acid solubility and foam stability. The non-storage protein isolate has good nutritional characteristics primarily because of its high lysine content.     

Fish protein concentrate: A new source of dietary protein

The concept of fish protein concentrate (FPC) is based on the more efficient use of our fishery resource by converting under-utilized fish to acceptable products for human consumption. FPC is not a single product. It is rather a family of products produced by different processes. Each member in the family of products has different characteristics and can be used for different purposes. Although a variety of processes has been developed, most have been based on solvent extraction of whole fish to remove lipids and water. FPC produced by solvent extraction of fish of several different species contains between 75% and 95% protein, which is particularly high in quality. This type of product can be used in foods to improve markedly their nutritional quality without significantly changing their other characteristics. FPC produced by some solvent extraction methods, however, has limited functional properties. New processes are being developed which use enzymes, various solvents, or a combination of enzymes and solvents. Products from some of these processes have improved functional properties and these FPCs appear to be particularly promising for use in foods for their functional attributes. Several problems still remain to be solved and research is needed to determine how FPCs can be produced and utilized most efficiently and effectively. There is, however, a commercial industry emerging and indications are that FPCs will find a significant place in the market. One of 16 papers being published from the Symposium, “Oilseed Processors Challenged by World Protein Needs,” presented at the ISF-AOCS World Congress, Chicago, September 1970. National Marine Fisheries Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce.     

The winged bean as an oil and protein source: A review

Despite high protein contents in its ripe seeds, tubers and fresh leaves (ranging from 29.3–39.0%, 3.0–15.0% and 5.0–7.6% respectively) and the high quality of that protein, the winged bean (Psophocarpus tetragonolobus) remained an obscure food source until about 10 years ago. Recently, this legume has received increasing attention from scientists because of its potential multiple uses as a food protein source in the humid tropics. This article reviews the utilization and nutrition literature of winged bean published during the last 10 years. The following aspects are covered: classification of winged bean proteins, nutritional properties and antinutritional components of the protein, protein quality, functional properties, and protein-based food products. The oil content of winged bean seeds ranges from 15.0–20.4%, and use of the winged bean as a potential oilseed crop is discussed. Areas of needed research are identified and described. Presented at the 74th Annual Meeting of American Oil Chemists’ Society, Chicago, May 8–12, 1983.     

Changes in structure and functional properties of whey proteins induced by high hydrostatic pressure: A review

High hydrostatic pressure (HHP) is an alternative technology to heat processing for food product modifications. It does not cause environmental pollution and eliminates the use of chemical additives in food products. This review covers the research conducted to understand the effect of HHP on structure and functional properties of whey proteins. In this paper, the mechanism underlying pressure-induced changes in β-lactoglobulin and α-lactabumin is also discussed and how they related to functional properties such as hydrophobicity, foam stability, and flavor-binding capacity.     

Protein-water interactions and functional properties

Hydration or rehydration is the first and perhaps most critical step in imparting desired functional properties to proteins in a food system. Water that interacts with the protein molecule exhibits different properties from those of “free” water. The types of water in protein-food systems are described in terms of structural, monolayers, unfreezable, hydrophobic hydration, imbibition or capillary condensation, and hydrodynamic hydration water. Protein functional properties such as swelling, solubility, gelation, water holding capcity, etc., are directly related to the manner in which the protein interacts with water. Methods for studying the protein-water interaction are discussed. The primary protein-water interaction is believed to take place at various water binding sites on the protein molecule. Theories that explain the mechanism of action of these different water binding sites are reviewed. Factors which affect the protein-water interactions include the number and nature of the binding sites on the protein molecule, protein conformation, plus environmental factors such as pH, salt, temperature and others. Finally, the protein-water interaction phenomenon and the physico-chemical and functional properties of proteins in protein isolate systems (dehydrated, solution, and gels) and in protein food systems are briefly examined.     

Fish meal and oil: Current uses

World landings of fish and shellfish are approaching 100 million metric tons (MMT) annually. Of this total, around 28% is processed into fish meal and oil. Economic pressures due to poor landings, low prices in traditional markets and high fuel costs have forced the industry to seek new markets and products that can take advantage of the unique properties of fish proteins and oils. Fish meal processing continues to evolve. Fresh raw materials and new, low-temperature processing techniques lead to products with excellent nutritional value. These new, special meals are finding uses in feeding farmed fish, early-weaned pigs, ruminants and pets. Fish oils, whether present as fat in the fish meal or as separated oil, are rich in ω3 fatty acids. When fed to food animals, these ω3 fatty acids deposit in the meat and depot fat. Concepts for poultry with an equivalent amount of ω3 fatty acids to lean fish are being developed. Eggs with a high ω3 fatty acid content and good functionality and flavor are under evaluation. Catfish with shelf-stable flavors and high ω3 fatty acids are also under study. ω3 Fatty acids may affect the immune function of livestock. Future research will evaluate the overall immune function of animals, including resistance to disease, survival under stress and hatchability.     

The role of processing in changing protein characteristics

In our efforts to design and produce proteins which deliver optimal benefits in products both reproducibly and cost effectively, we must keep in mind the following points. Protein “functionality” is only meaningful in a specific product and process context. Techniques are becoming available to investigate “molecular protein characteristics;” how we can best use them to understand how proteins contribute to “product attributes” remains to be elucidated. Different proteins respond differently to typical process regimes. Use of these proteins as functional ingredients may require formulation or process modifications.     

The influence of genotypic variation in protein composition on emulsifying properties of soy proteins

This study describes the relationship between the emulsifying properties of soybean proteins and their composition, i.e., glycinin (11S) and β-conglycinin (7S). Twelve investigated soybean genotypes showed significant differences in storage protein composition. The β-conglycinin concentration positively correlated with extractable soluble protein content, which was positively correlated with protein extractability. These data suggest that the level of β-conglycinin has a positive influence on protein extractability. The emulsion activity index (EAI) was strongly and positively correlated with the 11S∶7S ratio and strongly and negatively correlated with the concentration of β-conglycinin. The emulsion stability index (ESI) showed a moderate positive correlation with the monomeric form of glycinin and a strong positive correlation with the ratio of the monomeric to dimeric form of glycinin. No association was evident between ESI and EAI. Also, no relationship was found between ESI or EAI and extractability. Based on these data, it appears that the 11S∶7S ratio strongly reflects the ability of soybean proteins to form emulsions, whereas the ratio of the two different forms of glycinin may be crucial factors for the stability of soybean protein emulsions. Thus, understanding the relationship between protein composition and functionality could be useful for further improvement of functional behavior of soy proteins in food systems.     

Standards for protein based foods in developing countries

Legal specifications in India are issued by the Central Committee for Food Standards and are limited in number. Specifications issued by the Indian Standards Institution (ISI), which are discussed in this paper, are optional but prestigious and much more numerous. Foods based on milk proteins emphasize minimal protein damage, estimated by solubility measurement, and high sanitary quality. The latter is common to all other ISI food specifications as well. Edible oilseed proteins for use as food ingredients are formulated in various types or grades and carry such criteria as protein level, fiber content, and appropriate antinutrient level. Proteins from various sources may enter products such as protein mixes, weaning and toddler foods, biscuits, “vegetable” milks, and offspring of the latter like yogurt, ice cream, and reconstitutable powders. In certain products, protein level may be varied inversely with protein quality. To define the latter, the protein efficiency ratio has been adopted and a working methodology for India evolved through collaborative experimentation. The level of any added vitamins and minerals in these protein foods is such that an expected daily consumption of the food would carry 1/3 the Indian recommended daily allowance. Concentrate protein foods stand in a class apart in their very high levels of the nutrients present. Enriched staples like wheat flours could carry proteins, vitamins, and minerals or omit proteins if found functionally disadvantageous. Codes of practice are being developed by ISI in related fields, such as food advertising, in which one clause enjoins that sound established foods or food practices should not be denigrated; food labeling, in which the problem is to ensure a label meaningful to consumers; and date marking, which could hinge on certain and expected shelf life of the food.     

Production of food-grade cottonseed protein by the liquid cyclone process

A brief background is presented on the development of the Liquid Cyclone Process as modified to process glanded cottonseed kernels from the Texas high plains into a gland-free 65+% protein flour. Southern Regional Research Center's pilot plant process is described and related to the commercial process that will become operational in early 1974 at Plains Cooperative Oil Mill, Lubbock, Texas. Some of the functional properties of the flours and results of their evaluation in food application are discussed. One of seven papers presented at the symposium, “Processing Methods for Oilseeds,” AOCS Spring Meeting, New Orleans, April 1973. ARS, USDA.     

Peptidoglutaminase deamidation of proteins and protein hydrolysates for improved food use1

The limited deamidating ability of peptidoglutaminase (PGase) toward intact food proteins (0- 6% deamidation) can be significantly enhanced by prior protein hydrolysis and altering protein conformation by such means as moist heat. PGase deamidation increases protein solubility and improves emulsifying and other physical properties under mildly acidic conditions. A batch reactor method was developed for the large- scale PGase deamidation of food proteins. Michaelis- Menten kinetics for industrial reactions (mixed zero- and first- order) were used for predicting the behavior of the reactor and for calculating enzyme dosage required to completely deamidate a given quantity of protein. Using such a reactor in the deamidation of food proteins or protein hydrolysates can lead to new food proteins with superior functional properties from less functional starting materials. ¹Part of a symposium entitled “Preparation and Processing of Chemically-Physically Modified Proteins” held April 25, 1990, Session II at the 81st Annual Meeting of AOCS in Baltimore, MD. *To whom correspondence should be addressed at USDA-ARS-SRRC, P.O. Box 19687, New Orleans, LA 70179. 2Commercial firms are mentioned in this publication solely for the purpose of providing specific information. Mention of a company does not constitute a guarantee or warranty of its products by the U.S. Department of Agriculture nor an endorsement by the Department over products of other companies not mentioned.     

Protein conformations and their stability

Our understanding of the conformations of proteins and their stability has increased substantially in recent years. A reaction of considerable interest is native (N) ⇌ denatured (D) where N is the globular, native state of the protein which is now well defined as a result of numer-ous structural determinations by X-ray diffraction studies, and D represents unfolded, denatured states of the protein whose structure depends on the denaturant used to promote unfolding. Through experimental studies much is known about the kinetics, thermody-namics, and mechanism of this reaction. For example, it is known that the free energy change for this reaction under physiological conditions, ΔG_D, is between 3 and 15 kcal/mol for a fairly wide range of globular proteins. Thus, the globular conformation which is absolutely essential for the biological function is only marginally stable. In addition, these ΔG_D values are remarkably sensitive to small changes in the structure of the protein. It has been shown that single amino acid substitutions can dramatically increase or decrease ΔG_D values and some substitutions surely lead to unfolding of the polypeptide chain. Most chemical alterations in the structure of a protein, e.g., cleavage of a peptide bond, or modification of an amino acid side chain, lead to decreases, often sizable, in the confor-mational stability. The remarkably low conformational stability of globular proteins is important, in part, because many properties of the protein, e.g., solubility and proteolytic digestibility, change sub-stantially when the protein unfolds. Recent developments in these areas of interest to protein chemists and food scientists are illus-trated and discussed.     

The implications of future EC food contact legislation for lacquer coated food and beverage cans

Conclusions  The European Commission’s programme of work to harmonize the laws and regulations on food contact materials and articles is expected to produce a specific Directive on ‘polymeric coatings’ within the next few years. The ‘regulations’ in this ‘coatings’ Directive will cover food and beverage cans with internal lacquer coatings. The ‘coatings’ Directive will probably follow the same format as that of the ‘plastics’ Directive 90/128/EEC, with permitted lists of substances, some with restrictions mainly in the form of specific migration limits, and an overall migration limit. Experience in performing migration tests on plastics for compliance with the limits and restrictions in Directive 90/128/EEC has identified various problems and difficulties. Similar problems and difficulties have been found to occur when migration testing lacquer coated food and beverage cans, and their are some additional problems. Project work investigating these problems and difficulties have resulted in changes to the migration test procedures and protocols, which should ensure that in future migration testing on food and beverage cans reliable and valid test results are obtained.     

Competition of urea with oilseed proteins

Competition of urea with oilseed proteins in ruminant feeding depends primarily on economic relationships between these ingredients, cost of energy sources and proper feed formulation. A general summary of the more important factors to consider in replacing protein with nonprotein nitrogen in ruminant feeds is presented. Estimated urea utilization in the U.S. grew at a 15.5% compound annual rate from 1962 to 1966. From 1966–1969, usage increased at a 5% compound annual rate. Approximately 650,000 tons of urea were used by the U.S. Feed industry in 1969. Urea usage is expected to continue to grow in the United States. The high cost of energy sources in Western Europe will tend to slow its use by the feed industry of that area. In general, competition of urea with oilseed proteins will be greatest with heavy grain feeding of cattle, low cost grains and high priced oilseed meals. One of 16 papers being published from the Symposium, “Oilseed Processors Challenged by World Protein Needs,” presented at the ISF-AOCS World Congress, Chicago, September 1970.     

Conditions and trends in the world protein economy

Eating habits and food systems are difficult to change. Isolated and refined vegetable proteins are being used increasingly in a wide variety of food systems to improve nutritive values and functional qualities without displacing the system itself. They provide a way for people with rising affluence to move up the “food ladder” without disturbing familiar and traditional habits of eating. Worldwide commercial demand for food and feed crops from surplus-producing nations will continue to expand during the next decade. U.S. producers and those of other exporting nations will be able to expand production sufficiently to meet this rising commercial demand at reasonable prices during most of the years of the 1980 decade. But if tonnages necessary to satisfy real nutritional need (mostly in developing countries which are critically short of foreign exchange) were added to the commercial demand, the totals would be so great, there would be no way the export countries could produce enough. If malnutrition is to be stemmed or prevented, developing countries will have to learn to produce more on their own soil and provide the means of getting it to the people who need it. Contrary to some views, the U.S. livestock feeding industry should be regarded as an effective part of a world grain reserve and an aid to maximizing exports. In the short crop year of 1974, U.S. feed grain consumption was reduced to a much greater extent than exports. Livestock have the ability to act as a “surge tank” in the food line. There is urgent need in the world today for improved varieties of high protein legumes that are adapted to the tropics. An important component of sucess in improving food supplies in developing countries will be the emergence of enlightened and courageous political leadership. When country leaders “short term” it by giving in to urban pressures for cheap food, the result is usually counterproductive.     

Food emulsifiers—Science and art

General classifications of food emulsifiers are presented, and their functions are discussed. Examples of many food products are given, and recommended emulsifier usage levels are presented. Some of the food applications cited include: cakes, icings, toppings, bread, sweet goods, frozen desserts, coffee whiteners, peanut butter, margarine and confectionery coatings. One of seven papers presented in the Symposium “Fats and Oils in the Food Industry,” Atlantic City, October 1971.