Comprehensive analysis of soybean (Glycine max L.) by-products: Nutritional value, phenolic composition, and bioactive properties
Rafael Mascoloti Spréa, Tiane C. Finimundy, Ricardo C. Calhelha, Tânia C. S. P. Pires, Miguel A. Prieto, Joana S. Amaral, Lillian Barros
Abstract
Soybeans are key components in vegetable beverage production, generating two by-products: soybean hulls and okara. For every ton of soybeans, 50-80 kg of hulls and 120 kg of okara are produced, being often discarded or used in low-value applications like fertilizers or feed. This study aims at characterizing their biochemical and nutritional profiles to assess their potential reintroduction into the food chain. Both by-products have high levels of protein and dietary fiber, mainly insoluble. Okara and hulls predominantly contain oleic acid and linoleic acid, respectively. Seventeen phenolic compounds, mainly isoflavones, were identified, with genistein as the main compound. Hulls exhibit superior antioxidant activity compared to okara. Neither extract showed cytotoxicity or anti-inflammatory effects and exhibited limited antimicrobial activity. However, both demonstrate prebiotic potential, promoting beneficial gut bacteria growth. The results suggest that these by-products have significant potential as new ingredients for their protein, isoflavone, and fiber content, alongside prebiotic properties.