Comparative study of enzyme-assisted extraction and two-stage fermentation for vinegar production from Nymphaea pubescens and Nelumbo nucifera rhizome

Abstract Nelumbo nucifera (lotus) and Nymphaea pubescens (water lily) rhizome is attracting growing attention, primarily due to its high phenolic content, which is known for its natural antioxidant properties. The rhizomes are extensively consumed as a vegetable, offering substantial quantities of carbohydrate and dietary fiber. This study explored (1) the comparative assessment of antioxidant activity and proximate analysis of N. nucifera and N. pubescens ; (2) the investigation of the enzyme extraction method of rhizome crude extracts; and (3) the rhizome extracts for vinegar production, focusing on physicochemical properties. Significant data revealed that N. pubescens exhibited more antioxidant activity than N. nucifera . The carbohydrate content in the rhizomes of N. pubescens and N. nucifera was found to be 76.04% and 74.32%, respectively. The enzyme-extracted rhizome demonstrated that the application of pectinase and cellulase for 30 min yielded the highest output at 50.44%. The extracts were standardized to 20°Brix by adding sucrose before vinegar fermentation. Trials on alcohol fermentation evaluated instant dry yeast concentrations (0.5% w/v), effectively converting rhizome extracts to 10% alcohol within 5 days. Subsequent acetic acid production necessitated 7 weeks for both lotus species to attain an acidity ≥ 4 g/100 mL, accompanied by notable alterations in pH, total soluble solids, and residual alcohol throughout the fermentation process. These findings establish a foundation for enhancing lotus rhizome vinegar manufacturing, perhaps resulting in an innovative, value-added product with health-enhancing attributes.