摘要
This study was targeted towards evaluating the outcome of partially substituting sugar with soursop puree at differentproportions, varying pasteurization temperatures, storage durations and with the application of sodium benzoateand potassium sorbate as chemical preservatives on physiochemical, antioxidant and microbial qualities of yoghurt.There was a strong correlation (R^(2) = 0.7, Adjusted R^(2) = 0.65) between the syneresis and the water-holding capacityof the yoghurt as the substitution increased. At 50% soursop puree substitution in the yoghurt production, DPPHradical scavenging activity, total phenolic content, vitamin C, carbohydrate, protein, and ash contents increased to34.40%, 1.25 mg GAE/L, 58.50 mg/100 g, 29.26, 4.02 and 0.69%, respectively. Storage duration does not have a significantinfluence on the proximate composition of the yoghurt samples. However, the vitamin C content of the yoghurtdecreased when the pasteurization temperature was more than 80 ℃. The growth of lactic acid bacteria rangedbetween 2.9 × 10^(5)and 2.16 × 10^(6)CFU/ml. The use of sodium benzoate inhibited yeast growth more than potassiumsorbate while soursop substitution inhibited the growth of mould from 1.0 × 10^(6)CFU/ml to 3.05 × 10^(5)CFU/ml thanthe preservatives. Coliform was absent in all the yoghurt samples with or without preservatives. This informationwould be valuable in yoghurt development and quality control.
