The effect of fermentation time on the product quality of purple sweet potato (Ipomea batatas) probiotic ice cream with starter culture of Lactobacillus plantarum B1765

This research aims to determine the effect of fermentation time of purple sweet potato probiotic ice cream (Ipomea batatas) with a starter culture of Lactobacillus plantarum B1765 on microbiological quality (total lactic acid bacteria/LAB), chemical qualities (pH and total titrated acid/TTA), and organoleptic qualities (color, flavor, taste, and texture). The research method used an experimental method with a complete random design (CRD) with variations of fermentation time 0, 6, 18, and 24 hours. The total LAB was enumerated by the method of Total Plate Count (TPC), the pH value was determined using a pH meter, TTA was calculated using the acid-base titration, and hedonic test for organoleptic qualities with 30 panelists. The results showed that fermentation time affects the total LAB, pH value, TTA, flavor, taste, and texture, but do not affect the color. The total LAB increased by 2 log cycle from 7.16 x 107 CFU/mL up to 1.82 x 109 CFU/mL. The pH value decreased from 5.65 to 3.54. Then, the TTA value increased from 0,89% to 2,01%. The average value of panelist’s level preference on color, flavor, taste, and texture was 3.37; 2.99; 3.1; 3.33, respectively, which showed a tendency to like. The best treatment was purple sweet potato probiotic ice cream with a fermentation time of 18 hours. Total LAB and TTA were fulfilled the Indonesian National Standard (INS) for dairy based probiotic products, so this product could be developed as probiotics agent.