Evaluation of Quinoa ( Chenopodium Quinoa Willd ) Protein Isolate and Hydrolysate As Alternative Nitrogen Source for Growth of Lactiplantibacillus Plantarum WCFS1

ABSTRACT The demand for plant‐based dairy alternatives needs functional ingredients that support robust fermentation. This study compares native quinoa protein isolate (QpI) and its enzymatic hydrolysate (QpH) as nitrogen sources for Lactiplantibacillus plantarum WCFS1. Comprehensive characterization revealed that enzymatic hydrolysis converted the high‐molecular‐weight, β‐sheet‐rich proteins of QpI into peptides (QpH) with molecular weights below 5000 Da. While both substrates supported high final cell densities comparable to the control medium (MRS) (~10.5 Log CFU/mL), they induced longer lag phases, indicating a metabolic adaptation cost. Bacteria grown in QpH exhibited significantly enhanced cell membrane integrity, with propidium iodide incorporation reduced to 17.1% compared to ~23.6% for QpI and control cultures. This protective effect, independent of final pH, is attributed to the intrinsic bioactivity of the quinoa‐derived peptides. These findings demonstrate that QpH is not merely a nutrient source but a superior functional ingredient that actively enhances the physiological robustness of probiotic bacteria. This has significant implications for developing high‐viability, plant‐based fermented foods and probiotics, positioning quinoa protein hydrolysate as a key component for next‐generation functional products.