Refunctionalization of extruded‐expelled soybean meals

Abstract

AbstractSoybean meals produced by extruding‐expelling (FF) have poor functional properties due to heat denaturation of the proteins, which limits their utilization in foods. Hydrothermal cooking (HTC), a treatment in which steam (150°C) and high shear are applied to a slurry of soybean meal, was used to refunctionalize EE protein meals. Two EE samples with protein dispersibility indexes (PDI) of 35 and 60 were used, along with solvent‐extracted white flakes and full‐fat whole soy meal as controls. Two HTC methods were explored: One method used a treatment temperature of 154°C and seven different residence times, controlled by varying the holding tube length; the other involved flashing the treated slurry directly into the atmosphere without any back‐pressure regulation or holding. Effects of residence time on functional properties of the samples were investigated. The maximum effect of HTC conducted with the use of holding tubes (with‐holding‐tube HTC) was also compared with that of flash‐out HTC. Solid dispersibility, protein dispersibility, and emulsification capacity of both EE meals were significantly improved by both types of HTC treatments. The flash‐out HTC showed more benefits than the with‐holding‐tube HTC in refunctionalizing heat‐denatured EE protein. For example, the solid dispersibility, protein dispersibility, and emulsification capacity of EE meal with PDI of 35 were improved 2.0, 4.4, and 2.1 times, respectively, by flash‐out HTC treatment. Therefore, the HTC refunctionalization was proved effective in partially restoring the functional properties of the heat‐denatured soy proteins.