Preventing physical destabilization and bioactive isoflavone loss in germinated soy milk using nisin

BACKGROUND Germinated soy milk (GSM) is a promising functional beverage rich in bioavailable aglycone isoflavones. However, its nutrient‐dense matrix renders it highly susceptible to microbial spoilage and rapid physical destabilization. This study evaluated the efficacy of nisin as a non‐thermal biopreservation intervention to retard quality deterioration in GSM at ambient temperature (25 °C). RESULTS The untreated control spoiled rapidly within 3 days, characterized by a microbial surge (total colony count reaching 6.43 log CFU mL −1 by day 7), a precipitous pH drop (from 6.48 to 5.33), macroscopic gelation, and severe particle enlargement (volume‐weighted mean diameter D [4, 3] increased from ~1.0 μm to >64.0 μm). Conversely, nisin intervention (0.4 g kg −1 ) effectively suppressed microbial growth, maintaining total colony count at a safe level of 2.67 log CFU mL −1 on day 7. This microbial inhibition sustained the system pH at ~5.99, successfully preventing acid‐induced protein aggregation and preserving emulsion homogeneity ( D [4, 3] at 6.0 μm). Furthermore, nisin significantly mitigated the microbial‐driven degradation of phytochemicals, reducing the loss rate of aglycone isoflavones from 56.63% (control) to 29.29% after 7 days. CONCLUSION By effectively blocking the ‘microbial proliferation–acidification–aggregation’ deterioration cascade, nisin extended the ambient shelf life of GSM to 5 days. This targeted biopreservation strategy provides a robust framework for developing physically stable, clean‐label, and nutritionally enhanced plant‐based functional beverages.