From Conjugates to Aglycones: How Food Processing Technologies Reshape Soy Isoflavone Profiles

Soybean is the primary dietary source of isoflavones, bioactive phenolic compounds whose physiological effects depend strongly on their chemical form. In raw grains, isoflavones occur predominantly as β-glucosides and malonyl- and acetyl-glucosides, which exhibit lower bioavailability than their aglycone counterparts. This mini-review examines how food processing technologies reshape soy isoflavone profiles, focusing on technological strategies that promote the conversion of conjugated forms into aglycones. The chemical and biochemical mechanisms underlying isoflavone interconversion are discussed, emphasizing the roles of β-glucosidase activity, temperature, pH, water availability, and matrix structure in modulating conversion efficiency. Solid-state and submerged fermentations consistently emerge as the most effective approaches for aglycone enrichment, although outcomes remain strain- and substrate-dependent. In contrast, thermal processing primarily drives interconversion among conjugated forms through decarboxylation and deesterification, with significant aglycone formation occurring only when mild pre-heating conditions transiently preserve endogenous enzymatic activity. Emerging non-thermal technologies, including ultrasound, pulsed electric fields, and high hydrostatic pressure, enhance matrix permeability and enzyme–substrate interactions, enabling controlled modulation of isoflavone profiles while minimizing nutritional and sensory losses. Overall, integrating fermentation, controlled hydration, and process-intensification strategies represents a rational pathway to design soy-based products with enhanced aglycone content and improved bioaccessibility, supporting the development of functional foods with greater health-promoting potential.