Characterization and utilization of extruded-expelled soybean flours
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Extruded-expelled (EE) soy flours with a wide range of protein dispersibility indexes (PDI), and residual oil (RO) levels as well as EE soy flours originating from various value-enhanced soybean varieties were investigated for their functional properties and utilization potential in food systems. Functional properties investigated included protein solubility, emulsification capacity, activity and stability, foaming capacity and stability and water-holding and fat-binding capacities. Food systems investigated included a batter system and meat system. Results from the investigation focused on functional properties of low-fat soy flour (LFSF) with a wide range of PDI and RO levels showed, in general, LFSF with PDI/RO levels between 42/8 and 67/11 were more functional proteins when compared with LFSF with lower PDI/RO levels. Additionally, LFSF with this range of PDI/RO levels shared similar functional properties when compared with a 73 PDI, 0.6 RO defatted soy flour (DFSF). The second investigation involved the production of a standard cake doughnut formulation with one of three LFSF of different PDI/RO levels or a DFSF. These soy flour treatments were added at levels of 3, 5 or 8% (flour weight basis). The main reason soy flour is added to doughnuts is to decrease the fat absorption of the doughnut during frying. This investigation showed that doughnuts made with LFSF generally did not follow the same trend as DFSF for decreasing fat absorption. Other chemical, quality and sensory attributes showed unpredictable results for doughnuts produced with LFSF. The third study involved characterizing the functional properties of LFSF produced using EE technology, however the starting material was six different value-enhanced soybean varieties and two commodity (non-value-enhanced) soybean varieties. The alteration of certain soybean traits (i.e. fatty acid profile, elimination of lipoxygenase enzymes) did not deleteriously affect functional properties of the LFSF products. Finally, LFSF from the third study was texturized to produce texturized soy protein (TSP). This TSP was then introduced into ground beef patties at a rehydrated level of 30%. The results from this work indicated that the addition of TSP from value-enhanced LFSF, at a 30% level, did not have a negative impact on certain chemical, quality and sensory attributes.