Extruder-texturized products

Recently, Crowe and Johnson (2001) and Riaz (2001) showed that partially defatted screw-press cakes could be texturized. Previously it was believed that the fat content, which provides lubrication, was too high to allow proteins to texturize correctly. One manufacturer (Iowa Soy Specialties, Vinton, lA, a division of Kerry Food Ingredients) produces extruder-texturized products from EE press cake. 

Surfactants have been, reprotedly, used to prevent extensive puffing of extruded cereal products. It was found in these studies that surfactants could effectively inhibit gelatinization of cereal starch. However, effect of surfactants on protein texturization has not been reported. Two types of surfactants, sodium stearoyl-2-lactylate and calcium stearoyl-2-lactylate (at levels of 0.2 and 0.4% based on the weight of the flour), were mixed with soy flour prior to extrusion. A yeast protein (Torutein, manufactured by Amoco Inc.), claimed to be an extrusion helper although its function is not known, was added. 

Water holding capacity (WHC) of texturized products was determined by a relatively fast, easy and repeatable method. Extrudates were first dried to 5 to 7% moisture content, and reduced to 4-6 mesh size particles. To 5 grams of extrudate,... 

To determine built density (BD), extrudates or Hand Press Texturized products were dried to 5-7% moisture, and ground. Product passing through a U.S. No. 4 Sieve but retained on the U.S. No. 6 Sieve, was filled in 100 ml volumetric flasks, and tapped lightly for 20 times. Weight of the 100 ml sample was determined, and the built density was then expressed as grams per liter. 

Other soy protein products include dried soy milk and tofu (see the Chapter Food Use of Whole Soybeans), as well as mixtures of SF, SPC, or SPI with milk or egg protein, gelatin, or other components for specific functional applications. Extruder-texturized fburs and concentrates and spun fiber isolates, which resemble meat in appearance, may be made at the point of use but usually are supplied in bulk from strategically located production facilities. Edible co-products of soy protein ingredient manufacture include the hulls and the cotyledon fiber (cell walls) from SPI or soymilk production. The extract by-product from SPC may be used as the feedstock for isolating isoflavones. 

Whey proteins are known to increase immune response and maintain muscle mass (Phillips et ah, 2009). In one instance, when an immunosti-mulatory vitamin and mineral mixture developed at Tufts University Human Nutrition Research Center on Aging was blended with texturized WPI (TWPI) in an extruded snack bar, immunostimulatory effects were enhanced in young (< 5 months) and old (> 22 months) mice fed ad libitum for 5 weeks. The mineral mixture and TWPI improved T cell proliferation and reduced upregulated production of proinflammatory mediators in... 

The constraint of extruding whey protein above the useful texturization range is keeping the temperature below the point where pyrolysis will occur as evidenced by relatively constant nitrogen content. However, texturized whey products are sometimes extruded at 150 °C to form... 

Three different whey protein products extruded at the cook temperature of 75 °C resulted in varying degrees of melt texturization (Table 5.3). Among the whey proteins, WPC (WPC80) was the least texturized. Whey lactalbumin (WLAC) and WPI were both significantly (p < 0.05) more texturized, but a wider spread of texturization was observed for WPI, the initial and final values were from 28% to 94.8%, and therefore more emphasis was placed on studying WPI (Onwulata et ah, 2006). 

FIGURE 5.6 Solubility of texturized dairy protein products extruded at different temperatures, 25 (control), 50, 75, and 100 C Nonfat dried milk (NDM) whey protein concentrate (WPC80), containing 80% protein and whey protein isolate (WPl), containing 95% protein (Onwulata et at, 2003a). 

Coextrusion is the process of extruding two or more materials simultaneously or in tandem. It allows a combination of an ingredient such as wheat flour, which is inexpensive and easily enriched with vitamins and minerals, with dairy protein, which provides functionality and texture. For example, an early coextrusion of wheat flour and rennet casein was performed by van de Voort et al. (1984), who obtained products with varying characteristics depending on process parameters. 

Whey may be substituted for starch by as much as 25% in extruded corn snacks, but the product does not puff as much as com alone, as the water-holding whey protein does not react with the starch matrix (Onwulata et al., 1998). WPCs or isolates can be added along with starch to create expanded snack foods with boosted nutritional content however, without texturization, whey proteins in amounts larger than 15% may interfere with expansion, making the products less crunchy. To counter this effect, whey proteins can be texturized with starch to improve their interaction with other food components in a formulation, principally to increase extmdate expansion. In one successful application, between 25% and 35% of the flour was replaced with whey protein (Onwulata et al., 2001a,b). 

Calcium caseinate and butter oil have been extruded directly at 50-60% moisture levels to obtain a cheese analog with no surface water or fat (Cheftel et ah, 1992). The fat emulsification and melting ability increased with screw speed or barrel temperature. The texture of the extmded analogs was similar to those obtained by batch cooking and was affected by pH (Cheftel et ah, 1992) and emulsifying salts (Cavalier-Salou and Cheftel, 1991). The product can be used as adjimcts for hamburger, pizza, and sauces. 

The profound reason for having this many unknowns is attributed to the fact that the "technology" of extrusion texturization is well in advance of the "science". In-depth knowledge in the "science" portion of extrusion texturization will provide principles which can be used to accurately define the texturized protein product. This basic scientific knowledge should also provide data which could be used to improve operating efficiency of extruders, and serve as a basis for producing texturized protein foods, with desired characteristics for specific product applications, from a wide variety of raw ingredients. 

Figure 8. Exterior morphologies of extrusion texturized surfactant-added soy flours. Control, no surfactant added product Tolutein, yeast protein CSL SSL. Note the effect of surfactant on the diameter and surface smoothness of extrudates. (Mag. J.5X.)...

EXTENDER. A low-graxily material used in paint, ink. plastic, and rubber formulations chiefly to reduce cost per unit volume by increasing bulk, Extenders include dialomaccou.s earth, wood flock, mineral rubber, liquid asphalt, etc. Microscopic droplets of water fixed permanently in a plastic matrix are an efficient extender tor polyester resins. In the food industry, the term refers to certain extruded proteins, especially those derived from soybeans, which are used in meat products to provide equivalent nutrient values at lower cost. Made from defatted soy flour, they are often called textured proteins. 

Cross-linked polyethylene foams are produced by eilher radiation or chemical cross-linking of an extruded expandable sheet containing a chemical blowing agent. These products have finer texture and a softer, more resilient feel than extruded low density polyethylene foams and are used in comfort cushioning and cushion packaging applicutinns. 

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