Characterization and destabilization of the emulsion formed during aqueous extraction of oil from soy flour were investigated. This emulsion was collected as a cream layer and was subjected to various single and combined treatments, including thermal treatments and enzymatic treatments, aimed at recovery of free oil. Whereas heat treatment alone did not modify the free oil recovery, freeze-thaw treatment increased the oil yield from 3% to 22%. After enzymatic treatment of the emulsion, the oil recovery increased to 23% while the particle size of the enzyme-treated soy emulsion changed from 5 μm to 14 μm. The peptide profile of the proteins located at the emulsion interface was significantly modified after enzymatic treatment; the molecular weight of the enzyme-treated proteins was much smaller. This result suggested that smaller peptides were less able to stabilize the emulsion. When enzymatic treatment was followed by a freezing-thawing step, the oil recovery increased to 46%. The particle size of the emulsion that underwent this treatment increased to 25μm, indicating coalescence among oil droplets. This result can be attributed to the thinner interfacial membrane after enzymatic hydrolysis, partial coalescence during freeze-thaw, and coalescence after centrifugation.
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