Trypsin inhibitor content and activity of soaking water whey as waste in soy milk processing

Abstract

Soybean soaking water whey (SWW) is obtained as the waste of soy milk production and mostly represents an environmental problem. The aim of this study was to assess the content of proteins and content and activity of trypsin inhibitors of fresh SWW, obtained during soy milk production. Two zones of Bowman-Birk trypsin inhibitors (BBI) were detected. One was identified as a monomeric form of BBI (0.61-2.93%) and the other one was identified as a polymeric form of BBI (0.45-3.33%). The degree of BBI extraction (1.88-5.49%) was influenced by the soybean genotype and the grain size, i.e. it increased with increasing grain size. Kunitz trypsin inhibitor was not detected. Total proteins were found in traces in SWW (0.03-0.06%). Low residual trypsin inhibitor activity (0.32-0.55%) suggested that SWW can potentially be applied for preparing food or feed. In that case it will not be waste but a cheap functional supplement with BBI as a biologically active component.

Keywords:

• Soybean
• Bowman-Birk trypsin inhibitors
• proteins
• waste in food processing

Acknowledgments

The authors are grateful to the Maize Research Institute, Zemun Polje, and the Institute of Field and Vegetable Crops, Novi Sad of Serbia, for providing soybean genotypes.

Additional information

Funding

This work was financial supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grants no. 451-03-68/2020-14/200116).