Extruded Starches

SPC) and the control starch extrudates. Peaks 31, 33 and 35 appeared to be unique to G. On the other hand, some peaks (23, 38, 42-46) were found in all products including the starch control indicating that they were starch derived. It can also be seen that DSF had the most observed peaks while SPC had the least. Perhaps nonprotein components associated with DSF also thermally reacted to form detectable components. 

Fig. 56.—Water solubility of tapioca starch and chemically modified starch extruded without and with 2% addition of fatty acids. C2, acetic acid C 2, dodecanoic acid C 4, tetradecanoic acid C,A, hexadecanoic acid C18, octadecanoic acid C18 i, oleic acid C 8 2, linoleic acid CaSL, calcium octadecanoyl lactate GMS glyceryl monooctadecanoate GMP, glyceryl mono-hexadecanoate Am, Amidan and Dm, Dimodan (mixtures of GMS and GMP). (Reprinted with permission of C. Mercier, R. Charbonniere, J. Grebaut, and J. F. de la Gueriviere, Cereal Chem., 57 (1980) 4-9.)...

Figure 7.31. State diagram for the extruded meat-stareh matrix. (The arrow indicates the water activity above which the extrudates become rubbery at room temperature) (Reproduced with permission from Moraru, Lee, Karwe, and Kokini, 2002, Phase behavior of a meat-starch extrudate illustrated on a state diagram, J. Food Sci. 67, pp. 3026-3032, Institute of Food Technologists.)...

Zhu L, Shukri R, de Mesa-Stonestieet NJ, Alavi S, Dogan H, Shi Y (2010) Mechanical and microstructural properties of soy protein high amylose com starch extrudates in relation to physiochemical changes of starch during extrusion. J Food Eng 100 232-238... 

Ayoub A, Rizvi SSH. 2008. Properties of supercritical fluid extrusion-based crosslinked starch extrudates. J Appl Polym Sci 107 3663-3671. 

Blanche S, Sun X (2004). Physical characterization of starch extrudates as a function of melting transitions and extrusion conditions. Adv Polym Tech, 23,227-290. 

Harper, J.M., and Tribelhom, R.E. 1992. Expansion of native cereal starch extrudates. Pages... 

Starches are added to processed meats—lunch meats, hot dogs, sausages, etc.—as fillers, binders, moisture retainers, and fat substitutes. They are added to soups, sauces, and gravies as thickeners. They are used in extruded cereals and snacks to hold the shape of the material. 

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). 

Matthey, F. P. and Hanna, M. A. (1997). Physical and functional properties of twin-screw extruded whey protein concentrate-corn starch blends. LWT Food Sci. Technol. 30,359-366. 

Smietana, Z., Fornal, L., Szpendowski, J., and Soral-Smietana, M. (1988). Utilization of milk proteins and cereal starches to obtain co-extrudates. Food/Nahrung 32, 545-551. 

In the extruder the flour and water will be subjected to intense agitation and will be heated to above 100°C under pressure. Extruders are constructed to work at elevated pressures, indeed the barrel of the extruder is constructed in the same way as a gun barrel. Under these conditions the starch will gelatinise but the water cannot boil because the high pressure elevates the boiling point. 

A product resembling bread can be made using 75% of wheat flour and 25% of flour milled from extruded rice. The importance of extruding the rice is that some at least of the starch would have gelatinised. 

Plastics. The plastic films used in this study were prepared by the Otey semi-dry method (3), and were formulated to contain (dry weight basis) 40% starch, 45% poly(ethylcne-co-acrylie acid) (EAA), 15% urea (starch/EAA plastic) or 40% starch, 25% EAA, 25% low density polyethylene (PE), 10% urea (starch/PE/EAA plastic). Films were blown with a Brabender Plasticorder extruder as described in detail elsewhere (3). 

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. 

Pressure pellets sink when placed in water, whereas under the proper conditions, floating pellets can be produced through the extrusion process. That is accomplished when the feed mixture contains high levels of starch that expands and traps air as the cooked pellets leave the barrel of the extruder. This gives the pellets a density of less than 1.0. Floating pellets are desirable for species that come to the surface to feed since the aquaculturist can visually determine that the fish are actively feeding and can control daily feeding rates based on observed consumption. 

Cooking extruders have been studied for the liquefaction of starch, but the high temperature inactivation of the enzymes in the extruder demands doses 5—10 times higher than under conditions in a jet cooker (69). For example, continuous nonpressure cooking of wheat for the production of ethanol is carried out at 85°C in two continuous stirred tank reactors (CSTR) connected in series plug-flow tube reactors may be included if only one CSTR is used (70). 

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