COLOR, POLYPHENOLOXIDASE, AND SENSORY CHANGES IN BANANA JUICE AS AFFECTED BY HEAT AND ULTRAFILTRATION

A study was conducted to determine the effects of banana maturity (less mature; maturity stage 3, more mature; maturity stage 7), heat treatment of banana puree, heat pasteurization of juice, and ultrafiltration (UF) of juice on color, polyphenoloxidase (PPO) activity, and flavor of puree and juice. Heating puree to 90C inactivated PPO and reduced browning in puree and juice, especially in puree from more mature bananas which had greater PPO activity. PPO activity decreased considerably during cold-setting and filtration of juice, and was not detectable in unheated, pad-filtered juice from less mature bananas. UF of juice through a 10,000 mwco membrance, but not a 30,000, removed all PPO activity and reduced juice browning. Pasteurization of juice (hot fill at 90C) increased browning, but not as much as PPO activity in the puree. Pasteurization had no effect on juice flavor if the puree had been heated to 90C previously as puree, but altered the flavor (i. e., more cooked banana flavor) of juice that had not been previously heated to 90C. Pasteurized juice that had not been heated to 90C as puree had similar flavor (no significant difference) as pasteurized juice that had been heated to 90C as puree.