Malted Soybeans as a Substrate for Plant-Based Beverages—Analysis of Nutritional Properties, Antioxidant Activity, and Volatiles

Soybeans are often used as a raw material for the production of plant-based beverages. Malting significantly changes the properties of malted seeds; therefore, the aim of this study was the assessment of beverages obtained from soy malts (two types: 'Pilsener' and 'Caramel') produced from three soy varieties (Abaca, Abelina, and Aurelina). Beverages produced from malts were characterized by a higher protein content compared with beverages from unmalted seeds. The control samples showed a lower content of the sum of all amino acids (363.89-371.04 mg/g) compared with beverages from both types of malts, and the highest content was determined in the beverage from caramel-type malt of the Abaca variety (434.60 mg/g). Beverages from caramel-type malt of the Abaca and Aurelina varieties contained the largest concentration of phenolic compounds (8.35-10.33 mg GAE/100 mL) and the highest antioxidant activity (ABTS^•+ 0.36-0.45 μmol Trolox/mL, FRAP 0.24-0.30 μmol Trolox/mL, and DPPH 0.08-0.09 μmol Trolox/mL). Analysis of the concentration of volatile compounds has shown that using malted soybeans had a significant effect on the composition and share of various groups of volatile compounds (aldehydes, alcohols, terpenes, and ketones) in the analyzed beverages. The obtained results indicate the possibility of using soy malt in the production of plant-based beverages. However, further work is necessary to improve the quality and organoleptic properties of these products.