Different drying temperatures modulate chemical and antioxidant properties of mandai cempedak ( Artocarpus integer) [version 1; referees: 1 approved, 1 approved with reservations]

Background: Mandai, the fermented inner skin of cempedak (Artocarpus integer), may have further use as industrial ingredient while maintaining its antioxidative capacity. To promote fermentation, Lactobacillus casei was induced as the starter culture. This research was carried out (i) to investigate the effect of temperature on yield, chemical properties, and antioxidant activity of starter induced fermented mandai powder, (ii) to find the best drying temperature for the powder, and (iii) to find correlations between phenolic contents and antioxidant activity of the powder. Methods: The drying temperature was used as the variable, and was set at 45, 50, and 55°C at a fixed duration of 18 hours. The control was spontaneously fermented mandai dried at 50°C for 18 hours. Total phenolic content (TPC), hydrolyzed tannic content (HTC), and total flavonoid content (TFC) were spectrophotometrically measured, expressed gallic acid (GAE), tannic acid (TAE), and catechin (CAE) equivalents. Antioxidant capacity was measured by DPPH assay. Results: The best mandai powder had total phenolic content of 348.8±55.6 mg GAE kg -1, HTC of 143.8±9.3 mg TAE kg -1, TFC of 17.5±1.3 mg CAE kg -1, antioxidant activity (IC 50) of 56.96 ppm, ash content of 4.0±0.7%, pH value of 5.0±0.8, and yield of 9.3±0.8%. There was a strong correlation between TPC, HTC, TFC, and the antioxidant activity. Conclusions: Drying temperature affected all observed parameters but not ash and pH. Temperature of 45°C emerged as the best treatment to produce mandai powder from L. casei-inoculated mandai cempedak fermentation. The antioxidant activity of mandai cempedak was contributed by the phenolic components.