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Textured Soy Protein and Its Uses Mian N. Riaz, PhD. Head - Extrusion Technology Program and Graduate Faculty, Food Sci. & Tech. Program, Food Protein R&D Center, Texas A&M University, College Station, TX 77843-2476 Tel: 979-845-2774; Fax: 979-458-0019 E-mail: [email protected] Web: www.tamu.edu/extrusion

Background: Soybeans and soy products have been used for centuries in Eastern Asia as a staple and highly nutritious food source. World wide, 155 million metric tonnes of soybeans are presently grown. The United States produced 46.34% of the total soybean production in the world. After the US, Brazil (19.97%), China (9.2%), Argentina (13.5%), Paraguay (1.6%), European Union (0.7%) and all other countries grow about 8.59% (1). On an average, there is 40% protein, which means 63.6 million tonnes of soy protein is available for consumption. Soy protein supplies all nine essential amino acids and provides many functional benefits to the food processors and for a healthy diet. Soy ingredients promote moisture and flavor retention, aid emulsification, and also enhances the texture of many foods from a variety of meats to peanut butter, frozen desserts and even cheese. For food manufacturers, soy protein contributes valuable functional characteristics in processing systems as well as offering full digestability. Both isolated and concentrated soy proteins are easily digested by humans and equal the protein quality of milk, meat and eggs. Moreover, soy proteins are acceptable in almost all diets containing virtually no cholesterol and being lactose-free. The nutritional value of soy protein provides the consumer with a cholesterol free, lower fat alternative to animal protein.

Soy Health Claim The US Food and Drug Administration (FDA) has approved the use of a soy protein health claim on food labels in the US. Based on scientific evidence from 43

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human intervention studies, including 14 clinical trails, one epidemiological study and one meta-analysis, the FDA has concluded that the consumption of 25 g of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. Food made with the whole soybean may also qualify for the health claim if they contain no fat in addition to that present in the whole soybean. These would include soy foods such as: tofu, soymilk, soy-based burgers, tempeh, and soynuts (2). The FDA has agreed that food products which contain a minimum of 6.25 g of soy protein per serving and which are low in fat, saturated fat, and cholesterol, may carry one of two label claims. The first option is: “25 g of soy protein per day , as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of (name of food) supplies ---- g of soy protein”. The other permitted claim that manufacturers may use is: “Diets low in saturated fat and cholesterol that include 25 g of soy protein a day may reduce the risk of heart disease. One serving of (name of food) provides —g of soy protein. Foods where no additional fat has been added during processing will qualify. Foods produced from low fat or defatted soy protein ingredients will need to meet the low-fat requirement of 3 mgs or less of fat per serving. Recently, US Federal officials who say they are worried about the fat in school lunches want to let schools and day care centers serve tofu, veggie-burgers and other soy products as a meat substitute in federally subsidized meals. The US Department of Agriculture (USDA) is proposing to drop its restrictions on how much soy can be used in meals. Under the current rules,

soy can only be used in school lunch meats like

hamburgers and chicken patties and only in the amount of less than 30%.

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What is Texturized Vegetable (Soy) Protein Soy protein, once associated with1970's “mystery meat,” today is on the hot list of ingredients for its ability to contribute to two top food trends - the continued quest for high quality, low fat foods and the thriving field of functional and nutraceutical foods. The higher functionality of soy protein concentrates and soy protein isolates and their neutral flavor profile, account for their wide application in the food industry. There are several different definitions of texturized vegetable protein in the literature depending upon the sources. Texturized vegetable can be defined as “fabricated palatable food ingredients processed from edible protein source, including among others soy grits, soy protein isolates, and soy protein concentrates with or without suitable option ingredients added for nutritional or technological purposes. They are made up as fibers, shreds, chunks, bits, granules, slices or other forms. When prepared for consumption by hydration, cooking, retorting or other procedures, they retain their structural integrity and characteristic ‘chewy’ texture” (3). The USDA has defined textured vegetable protein products for use in the school lunch program as: “food products made from edible protein sources and characterized by having structural integrity and an identifiable structure such that each unit will withstand hydration and cooking, and other procedures used in preparing the food for consumption” (4). The Food Protein Council of the National Soybean Processors Association has defined textured vegetable protein as being: “derived from edible vegetable protein source, and mixtures thereof, by physical and/or chemical processes. These materials are converted into a structural form having definable textural properties similar to those of the food system for which its use is intended. Food ingredients and/or additives may be incorporated to enhance its nutritive value and organoleptic properties. Textured vegetable protein shall contain not less than 35% protein (N x 6.25) on a moisture free

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bases. The protein efficiency ratio (PER) shall be not less than 1.8 on the bases of PER of 2.5 for casein”.

Meat Extender Meat extenders produced from the extrusion processing of defatted soy flour or flakes and soy concentrates, and they represent the largest portion of textured protein. Meat extenders are rehydrated to 60-65% moisture, blended with the meats or meat emulsions, to food product to a level of 20-30% protein.

Meat Analog An extrusion process utilizing one or two extruders in a series can be employed to convert vegetable protein source directly into simplified varieties of meat analogs. These meat analogs have remarkable similarity in appearance, texture and mouth feel to meat.

Extrusion technology can form a fibrous matrix (analog) almost

indistinguishable from meat, and consumed as it is.

Ingredient Selection Traditionally, the most popular raw material for production of texturized vegetable proteins in an extrusion system has been defatted soy flour. This material was preferred due to its ability to be controlled through the extrusion system in order to produce a quality meat extender. As extruder designs improved and operation techniques increased the ability of extruders to produce a wider range of products emerged. Soybean protein are the single largest source for the manufacturing of textured protein products world wide. This is because of the simple economic law of supply and demand. Worldwide soybean supply is plentiful, and overall it is cheap and a relatively easily managed source of protein. The use of soy isolates in combination with other ingredients, as well as the use of soy concentrates, wholly or partially increased.

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The addition of minor ingredients or chemicals can be used to increase the range of raw ingredients suitable for production of a specific textured vegetable protein product. It is important to understand the effect of these minor additives on the texturization of vegetable protein, since these ingredients can improve the final texture and aid in texturization. Some of these additives are food flavors, colors, pH modifiers, surface active substrates, emulsifiers labeling agents, wheat gluten, surfactants, etc (5). These additives assisted the food scientists in controlling the functional properties, structures, mouthfeel and/or density of the processed material. Addition of minor ingredients or chemical adjustment of the texturized vegetable protein, the raw material can enhance various aspects of the finished product and lessen the specification constraints of some of the raw material. Other soy protein materials have recently shown that they can also be texturized into usable end products. Blends of high Protein Dispersibility Index (PDI) defatted soy flours and low PDI materials such as soy grits, have been used, extruded, and texturized into products. Texturization of animal grade soybean meal has also been performed. Ingredient selection is an important part of the texturization of vegetable protein. Defatted soy flour has 50% protein (minimum), 3.5% fiber (maximum), 1.5% fat (maximum) and PDI of 60 to 70. Soy flour with these specifications allow controllable production of textured proteins in chunk and extended form on single screw extruders. Other vegetable protein sources also have been used as raw materials for texturization, which include: glandless cottonseed flour, wheat gluten, defatted sesame flour, canola or rape seed concentrates, defatted peanut flour, as well as soybean grits, flakes, meal, concentrates and isolates. A properly selected extruder configuration may be very insensitive to fluctuations in the PDI of vegetable proteins. Decreasing PDI levels in the raw materials will require additional specific mechanical energy input to maintain the same quality of texture in the

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extrudate.

Uses of Texturized Soy Protein Texturized soy protein has been a commercial success for many years because of the development of machinery that is capable of continuously producing textured vegetable product. The texturization of plant proteins has been a major development in the food industry. Processes, like extrusion, have been developed to impart a fibrous structure to amorphous plant proteins. Once texturized, these plant proteins can be dehydrated for use as an extender of fresh or processed meat. Consumers are becoming increasingly interested in healthy foods and open to soy protein ingredients. Texturization of soy flours into usable meat extenders and replacers is economically feasible for some time. Texturized soy products serve a variety of purposes, including alternative protein sources for the manufacture of convenience foods and for centralized feeding of large numbers of people within defined budgets.

Today, due to increasing consumer demand for healthy diets and concerns about rising meat prices, some industry leaders are betting that consumers will increase their appetites for soy-based burgers. As a result, various types of soy based meat products are now seen in the market. There are basically three major market groups for meat analogs. Each may restrict the ingredient choices during product formulation. They range from those who limit certain animal products because of religious

dietary

restrictions. The second group consists of those looking for a healthier alternative to meat. The final group consists of people who are looking for cheaper protein sources (6). Texturized vegetable protein is being used increasingly in North America as an extender of red meat products. Among the low cost vegetable protein products developed for use in foods as meat extenders or replacement, the most rapid growth

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has been in the area of textured products manufactured by thermoplastics extrusion. Technology is becoming quite accomplished at creating realistic analogs that equal their meat counterparts in term of flavor, texture and most importantly, satiety. There are analogs of hamburger, both in patties and ground form; sliced lunch meat; sausages; hot dogs; Canadian bacon; pepperoni; bacon bits; and stuffed turkey. Texture and flavor are the two biggest challenges in developing a meat analog. Vitamins and mineral fortification can be done for the school and military luncheon programs. Some popular prepared vegetable protein foods are pareve (without meat, milk, eggs and their derivatives) and are of interest to people following Jewish (Kosher) dietary laws. Islam is one of the world’s fastest growing religions, and Muslim are today demanding Halal foods. Texturized vegetable foods provide an alternative to animal meat and falls under the Halal foods (7). Texturized vegetable protein from soy concentrate have the advantages of blander flavor and major reduction of non-digestable natural sugars (stachyose and raffinose) which can cause considerable flatulence, abdominal discomfort, and venting in some individuals. Modern texturized soy flours have milder flavors than in earlier years, which are easily masked in highly seasoned foods, like tomato sauces, pizza toppings, and canned chilli. Users of texturized vegetable protein includes the growing numbers of vegetarians, and people concerned with lowering cholesterol and total fat intake. Textured protein made from soy is not just a filler, it can be used as a distinct product, e.g., along with ground beef, as well as simulated products, e.g., a meat analog as a major source of protein in the human diet. When textured soy protein is used as a substitute for other products, their textural as well as nutritional properties should be similar to those of the product being replaced. Textured soy protein can be added to meat as extenders or it can be consumed directly as simulated meat analogs. Breaded chicken patties with as much as 30% of

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the meat replaced were actually preferred to all meat patties. Meat analogs can be flavored and formed into sheets, disks, patties, strips and other shapes. There are meat free hot dogs, hamburgers, chicken patties, nuggets, hams, sausages, meat snacks, and loose meat products for chilies, tacos, and spaghetti. It is very difficult to tell the difference between real and textured soy protein. In India, China, Japan and South Korea textured soy protein is eaten directly as a flavored or seasoned piece usually as a side or main portion of the meal. A good example of a completely meat-free meat analog is flavored bacon bits. Some of the textured protein consumption in different parts of the world is based on religious, cultural, or economic reasons. A good example is vegetarian diets for most Indians (Hindo). Textured soy protein widely used in child nutrition programs as well as for worldwide relief agencies to help feed famine plagued people in impoverished countries. Because of their low moisture and water activity, storage, shelf life and handling under poor conditions, do not become a problem. Vitamins and minerals can be fortified in textured soy protein to make it an ideal protein source. It is cholesterol free and can be processed as a low fat food. Textured soy products can assist in weight control by providing high quality protein in a concentrated form, specially designed low calorie/high nutrient ready meals can be produced. These can make a significant contribution to weight control products. Vegetarians have modified many recipes to replace meat with soy proteins. Recipes are available to use textured soy protein in breakfast foods, appetizers, soups, sandwiches, gravies, desserts, ethnic food and main dishes. Several food items are available with textured soy protein, which are designed to grill or cook in microwave ovens. Some times these food items are co-extruded with soy concentrates and wheat gluten. Ingredients, including flavors, and colors and edible adhesives (like soy protein isolates, hydrocolloids,

or starch, calcium caseinate and egg whites) are added to

hydrates textured soy protein before forming into patties, freezing and packaging. The demand for meat extenders and meat analogs will continue to rise. Meat

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extenders are still the largest segment of the textured vegetable protein market, however, the use of meat analogs are increasing. We are becoming more aware nutritionally of the foods we eat. Along with the beneficial high protein content of actual meats, there are some negative health benefits, namely cholesterol. However, most people still like their meat. Meat analogs have become a viable alternative in offering a nutritionally acceptable meat substitute that in some cases come close to matching actual meat products. Food scientists have made major headway in improving flavor, texture, mouthfeel, appearance and color of meat analog products. In the market place, you can see more and more meat analog and meat extender products such as, bacon bits, soy burgers, meat free hot dogs, chicken nuggets, breakfast sausage patties/links and bacon to name a few. Many of these products are even packaged in the same fashion as their meat counterparts. American consumer’s acceptance of textured vegetable protein has prompted other countries’ interest in this low-cost answer to the desire for more protein foods. U.K, South Africa, Japan, Korea, Mexico and India are among the nations that have joined the United States in commercial production.

Conclusion Texturization of soy flour and other proteins into usable meat extenders and replacers has been economically feasible for quite some time. Initially the use of extrusion equipment for this purpose was limited to a narrow range of raw materials. Developments in machinery, new techniques, and the art of texturizing protein products has changed, and as a result the spectrum of ingredients that can be texturized into useable end products, has increased greatly.

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References 1. P. Golbitz. 2001. Soya and Oilseed Bluebook. p330. 2. American Soybean Association. 2000. Soyafoods. Vol.11:1. 3. Anon. 1972. Notebook on soy: “Textured Vegetable Protein”. School Food Service J. 26:51 4. USDA, ARS. 1971. Textured Vegetable Protein Products (B-1), FNS Notice 219. 5. B. Strahm. 2000. Raw material selection and additive effect on texturized vegetable protein. In “Practical Short Course Manul Textured Vegetable Protein” Eds. M. N. Riaz and M.E. Barron. Food Protein Research & Development Center, Texas A&M University System, College Station, Texas. 6. K. Liu. 1997. “The second generation of soyfoods” in Soybeans: Chemistry, Technology and Utilization, Aspen Publication, Gaithersburg, MD – USA. 7. E. W. Lusas. 1996. Modern texturized soy proteins: Preparation and uses. Food Tech. Europe. Sep/Oct. 132.