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 (les s mature; maturity stage 3, more mature; maturity stage 7), heat treat ment of banana puree, heat pasteurization of juice, and ultrafiltratio n (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 bana nas which had greater PPO activity. PPO activity decreased considerabl y during cold-settling 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 membrane, but not a 30,000, removed all PPO act ivity 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 h eated to 90C previously as puree, but altered the flavor (i.e., more c ooked banana flavor) of juice that had not been previously heated to 9 0C. Pasteurized juice that had not been heated to 90C as puree had sim ilar flavor (no significant difference) as pasteurized juice that had been heated to 90C as puree.