Acta Scientiarum Polonorum Technologia Alimentaria

Background. Sufu (fermented tofu) is a traditional food in several Asian countries, produced through the fer­mentation of tofu with molds such as Actinomucor elegans. Enzymes from microorganisms metabolize tofu substrates, generating volatile compounds that contribute to the product’s distinctive flavor when combined with alcohol and salt during ripening. This fermentation process also improves digestibility. Incorporating pur­ple sweet potato (PSP) into tofu creates a novel product with enhanced nutritional value and antioxidant activity.
Materials and methods. Local raw materials and an Actinomucor elegans strain from the Institute of Food and Biotechnology, Can Tho University, were used. The effects of varying salt concentrations (8,10, and 12% w/v) and alcohol concentrations (8, 10, 12, and 14% v/v) in the brine were examined during PSP sufu ripening (10, 20, and 30 days). Nutritional components, including soluble protein, free amino acids, ammonia content, and bioactive compounds, including total phenolic content (TPC), total flavonoid content (TFC), and anthocyanins, were analyzed. Antioxidant activity was assessed using DPPH radical scavenging, expressed as IC50 values.
Results. Optimal brine parameters for PSP sufu production were identified. The nutrient composition in­cluded 18.5% free amino acids, 6.94% soluble protein, 1.55% NH3, pH 5.66, and 0.36% total acid. TPC, TFC, and anthocyanin content were 82.7 mg GAE/g d.w., 22.6 mg QE/g d.w., and 117.86 μg/g d.w., respectively. DPPH radical scavenging activity was 97.5 μmol TE/g d.w., with an IC50 value of 4.66 mg/ml.
Conclusions. PSP sufu demonstrates high nutritional and antioxidant quality when ripened for 30 days in brine containing 10% salt and 12% alcohol. These aging conditions promote favorable biochemical changes, enhancing both its functional properties and nutritional value.