| In the study, effects of hot water temperature on clarification, total soluble solids, polyphenol oxidase (PPO) and color of juice during hot water extraction were discussed on the basis of the theory in which heat treatment might induce the pectin and protein in banana pulp to form insoluble products. Results showed that the hot water temperature, which showed the strongest ability to form insoluble products at 75益, had a significant effect on the ability of forming insoluble products for pectin and protein in banana pulp. The clarification of banana juice extracted by hot water of 75℃was highest, and its light transmittance at 660 nm was close to 90%. The contents of pectin and protein in banana juice extracted by hot water of 75℃were the least, which were lower than 7.3 and 12.9 mg/100mL respectively.
Hot water extraction of 75℃could not completely inactivated the PPO of banana pulp because of its resistance to heat, so 0.05% L-cysteine or ascorbic acid needed to be added to banana pulp to inhibit the browning of juice induced by residual PPO. |
