Comparative Studies on the Trypsin Inhibitor Activity in Soybean Seeds and Soybean Products


Institute of Grain and Feed Industry, BG-2232, Kostinbrod, Bulgaria


TZVETKOVA, V. and M. SIMOVSKA, 1999. Comparative studies on the trypsin inhibitor activity in soybean seeds and soybean products. Bulg. J. Agric. Sci., 5: 635-639

Studies on the antitryptic activity in raw soybean seeds (the varieties Zarya, Beeson, Hodson and commercial soybean seeds), soybean meals (import from Argentina and produced in Bulgaria) and soybean flakes have been conducted. The trypsin inhibitor activity (TIU/mg) have been determined according to the AACC method (1983) with slight modification.
The purpose of the present investigation is to carry out the comparative measurements of the trypsin inhibitor activity in raw soybean seeds and soybean products at two wavelengths which is related to the possibility of increasing the sensitivity and decreasing the spectophotometer error of the method. Trypsin inhibitor activity of the soybean meals and flakes, used for the production of feedstuffs have been also evaluated.
The absorbtional spectrum of the enzyme reaction product (p-nitroaniline) against the reference solution posesses maximum of absorption at 388 nm, while the DL-BAPNA shows continium in the range from 380 nm to 420 nm, under the same conditions. The absorbance of p-nitroaniline, measured at 388 nm is by 38.6% higher than the absorbance measured at 410 nm. The results show that a spectrophotometer error of 1nm at the lower wavelegnth introduces a relative error of 0.1%, whereas the similar instrumental error at 410 nm gives 3.1%.
The comparative measurements on the trypsin inhibitor activity (TIU/mg) in soybean seeds and soybean products at 410 nm and 388 nm show higher values by 31-33% at the lower wavelength. The detail measurements on the trypsin inhibitor activity, which are the main antinutritional factors in soybean, are of great importance for their processing. This related to the supply of high quality protein components for feedstuff production.

Key words: trypsin inhibitor, soybean, soybaean meal, soybean flakes