Effect of the microwave treatment on anti-nutrients of soybeans

BACKGROUND: Soybeans contain anti-nutrients that have to be inactivated before being used as feed for livestock and poultry. AIM: Obtaining the new data on the effect of the heat treatment on soybeans. MATERIALS AND METHODS: Soybeans of the Dongsheng 22 and SK Alta varieties were processed with micronization, autoclaving and microwaves in the developed microwave unit. RESULTS: After micronization, the decrease in total starch was 10–16%, after autoclaving and microwave treatment — 15–17%. The three kinds of treatment did not have a significant effect on total phenolic content. The content of flavonoids increased by 7–9% after autoclaving and micronization and by 16% after microwave treatment. When micronizing and autoclaving soybeans, no changes in antioxidant activity were observed, but with microwave treatment, it increased by 3–5%. The decrease in trypsin inhibitor activity was 80% after microwave treatment and 73–79% after micronization and autoclaving. The tannin content was reduced by 10% with microwave treatment and by 7–9% after micronization and autoclaving. The decrease in phytic acid content was 43–45% and repeated for all kinds of treatment. CONCLUSION: The reduction of antinutrients after micronization, autoclaving and microwave processing ensures the use of soybeans for feed. Milder temperature conditions and cyclic processes of heating and cooling during microwave processing increase the safety of soybeans. The higher heating rate and low energy costs of microwave processing ensure economic feasibility.