Extruded snack products

There are many extruded snack products that are fried, seasoned, and packaged for distribution. One of the popular products is extruded com chips, made either from the cooked com or from masica, and is extmded through extmders. The product is... 

Rios, A.O. and Mercadante, A.Z., Novel method for the determination of added annatto colour in extruded corn snack products. FoodAddit. Contamin., 21,125, 2004. 

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... 

Plunkett, A. and Ainsworth, P. (2007). The influence of barrel temperature and screw speed on the retention of L-ascorbic acid in an extruded rice based snack product. /. Food Eng. 78,1127-1133. 

Currently, many types of extruded food products are produced (9) and include ready to eat (RTE) cereals, snack foods, beverage bases, as well as soft-moist and dry pet foods. 

The machinery has been borrowed from the plastics industry. An early single screw extruder was used in the 1940s to produce a snack product from maize grits but the operational advantage of twin screw machines was demonstrated later. It appears that they are more efficient in mass transport, less heat is dissipated, and therefore heat transfer can be better regulated by barrel heating (Lo et al. 1998). 

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). 

Onwulata, C. I., Smith, P. W., Konstance, R. P., and Holsinger, V. H. (2001b). Incorporation of whey products in extruded corn, potato or rice snacks. Food Res. Int. 34, 679-687. 

Products where this is the sole expansion system are extruded products. This sort of cooking is used for the production of breakfast cereals, savoury snacks and some crisp breads. Of these, only the crisp breads are really within the scope of this book. 

Wheat starch has been formulated in a variety of snack foods, whether they are extruded, expanded, microwaved or in the form of a stick or half products.570-574 In the case of yogurt or custard-type milk desserts, modified wheat starches were used for their thickening or gelling properties.575,576... 

Starch modifications can be classified as physical modifications, chemical modifications and genetic modifications.45 Physical modification of cassava starch involves application of shear force, blending and thermal treatment. A combination of thermal treatment and shear force has been widely used to produce many extruded products and snacks. Well-known physically modified cassava starch products are alpha starch or pregelatinized starch and heat-moisture treated starch. 

In the extrusion of snack foods, cereals and pet foods, cooking prior to extrusion is required. This can be accomplished in a steam pressure cooker integral with the extruder such as shown in Fig. 5.17. Screw diameters up to 10 in. (25 cm) are used in this application yielding typical capacities of 4,000 lb/h (1.8 Mg/h) with a 50 hp (37 kW) extruder drive to 12,000 lb/h (5.4 Mg/h) with a 150 hp (112 kW) extruder drive, depending on formulation and product requirements. 

Soy, and Other Legume Proteins Two quite different product types have been constructed by extrusion, high-density flaked structures for meat analogues, and lower density and crispy products for high-protein snacks. The latter uses conditions similar to that of starch-based cereal extrusion to obtain low bulk density in the expanded product the former uses a higher water content in the extruder barrel and lower exit temperatures to obtain a dense material with open pores or even flaked structmes. For these two types of processes, molecular changes in the extruder barrel are not dissimilar. Post-die structuring of the extrudates determines final product properties. 

Stojceska et ah (2008) studied the incorporation of cauliflower trimmings into ready-to-eat expanded products (snacks) and their effect on the textural and functional properties of extrudates. It was found that addition of cauliflower significantly increased the dietary fiber and levels of proteins. Extrusion cooking significantly (P < 0.0001) increased the level of phenolic compounds and antioxidants but significantly (P < 0.001) decreased protein in vitro digestibility and fiber content in... 

High-pressure extrusion involves comparable changes. The product becomes hot and vapor bubbles are formed in it. The bubbles expand when the material leaves the extruder, and water vapor can readily escape. Upon cooling, a solid foam is formed, i.e., a glass containing many air cells. This is applied in manufacturing dry snacks. 

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