Characterization of soymilk produced by continuous flow high pressure throttling process
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Standard soymilk processing uses filtration or centrifugation step to remove coarse solids in the comminuted soy. The objectives were to produce soymilk from dehulled beans by Gaulin homogenizer or produce sterile soymilk using microfluidizer-throttling or continuous flow high pressure throttling (CFHPT) to retain retaining all essential soybean solids. The soymilk was characterized for particle size distribution, rheological and ultra-structural properties, to establish an empirical model to characterize the distribution of particle size of particles in the soymilk, and to evaluate the consumer acceptability. Whole dehulled soybeans were blanched, mixed with deionized water, and comminuted coarsely in a food-processor. An intermediate comminution step in Megatron (process M) or Fitzmill (process F) or Stonemill (process S) was followed by homogenization at selected pressures using Gaulin homogenizer or microfluidizer-throttling or CFHPT system. The combined process M and CFHPT treated samples at the highest pressure showed the smallest particle size and the highest apparent viscosity. All samples showed pseudoplastic flow behavior. Ultrastructural images elucidated particle microstructure in the soymilk and homogeneity of suspended particles. The very small fat globules at highest CFHPT pressure treatment of process M were seen entrapped in the network and was uniformly distributed. Thus combined process M and the highest CFHPT pressure was considered the best treatment. Therefore, the high pressure throttling process will allow utilization of the whole soybean to produce excellent quality soymilk with high emulsion stability. The increase in the CFHPT flow rate significantly affected size reduction of particles of soymilk. The empirical models were established which can be used to predict the size of particles in soymilk, at different volume fractions, processed using high pressure throttling processes at various pressures and flow rates. Consumer acceptability test showed that more research is needed to make a soymilk that appeal to the taste of the American consumer before the CFHPT process can be used commercially to produce soymilk. Thus, soymilk with all the essential solids can be made available to the public and processors benefit from the high processing yields since none of the essential solids of the beans are discarded.