In Vitro Digestion Influences Bioactive Compound Profiles, Antioxidant Activity, and Free Amino Acid Release in Plant-Based Milk Alternatives

This study evaluated the bioactive compounds, antioxidant activities, phenolic and flavonoid profiles, and amino acid composition of six plant-based milk alternatives (coconut, almond, cashew nut, soybean, peanut, and mung bean) and assessed their changes following in vitro digestion. Mung bean milk exhibited the highest total phenolic and flavonoid contents and antioxidant activity among all samples. Generally, enzymatic digestion significantly increased total phenolic content and antioxidant activity across all plant-based milks, with DPPH activity increasing approximately 2–4-fold, while total flavonoid responses were mostly unchanged. Individual phenolic compounds, including gallic, syringic, and gentisic acids, were newly detected after digestion in several plant-based milks. Protocatechuic acid, which was present only in trace amounts in a few controls, increased more than 200-fold after enzymatic digestion, indicating enhanced release of matrix-bound compounds. Free amino acid levels also increased following digestion, particularly in almond, cashew nut, and mung bean milks, whereas coconut, soybean, and peanut milks showed minor changes. These findings highlight varied nutritional and functional responses to digestion among plant-based milks, providing a basis for the development of functional beverages.