Effect of temperature and time during steam treatment on the protein quality of full-fat soybeans from different origins
1998
Qin, G.X. | Verstegen, M.W.A. | Poel, A.F.B. van der
Soybeans (Glycine max) of Argentinian and Chinese origin were steam-processed at 102 degrees C, 118 degrees C and 136 degrees C for various durations with the use of a laboratory-scale steam toaster. Samples of raw and processed soybeans were analysed for dry matter (DM), crude protein (CP), trypsin inhibitor activity (TIA), protein dispersibility index (PDI) and reactive lysine content. Chinese raw soybeans showed higher levels of CP, TIA and PDI, and a lower level of reactive lysine than Argentinian raw soybeans (366 vs 357 g kg-1, 20.6 vs 15.2 mg g-1, 87.6 vs 85.6% and 17.4 vs 19.4 g kg-1, respectively). Both the TIA and PDI of the two soybean samples were decreased following a logarithmic pattern with the lengthening of the heating time when beans were steam heated at various temperatures. The reduction rates for TIA and PDI, however, were different between the two origins of soybeans. Chinese soybeans required a longer time or a higher temperature to reduce their TIA to a safe level in comparison with Argentinian soybeans. In the case that the beans were heated at 136 degrees C, the difference in PDI between Chinese and Argentinian soybeans was smaller. It is concluded that the two soybeans origins need different processing conditions to improve their protein properties.
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