88E-25 |
Effect of two additives to sucrose syrup on polyphenol oxidase activity change during osmotic dehydration |
K. N. WALISZEWSKI, Unidad de Investigación y Desarrollo en Alimentos, Instituto Tecnológico de Veracruz, M.A. de Quevedo 2779, Veracruz, 91870, Mexico and S. L. Ovando, UNIDA, ITV, Veracruz, Mexico. During osmotic drying, fruit slices can undergo enzymatic and no enzymatic darkening process and visual color change is considered as a major sensory parameter and acceptability attribute of a food product. The formation of darkening pigments by enzymatic browning is conducted by enzyme polyphenol oxidase (PPO) which catalyzed oxidation of mono- and diphenols to o-quinones which can polymerized spontaneously to form brown pigments. In fresh and undamaged fruit, natural phenolic substrates are separated from PPO by compartmentalization and browning occur very slowly but when fruit is sliced, enzyme activity is faster. The purpose of this study was to determine effect of sodium metabisulphite and 4-hexylresorcinol in sucrose syrup during osmotic dehydration of banana slices. Three osmotic dehydration conditions were selected as the most adequate due to color change but also where PPO residual activity was still present after osmotic drying : T1 (60 0Bx, 50 0C, pH 6), T2 (60 0Bx, 60 0C, pH 8) and T3 (70 0Bx, 50 0C, pH 8). Sodium metabisulphite was added from 100 to 1000 ppm and 4-hexylresorcinol from 10 to 200 ppm. PPO was determined in the inter and outer part of the banana slice spectrophotometically at 302 nm with 4 methylcathecol. During dehydration of banana slice PPO activity tends to decrease but residual enzymatic activity was still found. Sodium metabisulphite concentration up to 200 ppm and 4-hexylresorcinol up to 50 ppm have not affect on PPO residual activity after four hours of osmotic dehydration. Depending to process conditions, higher concentration of additives were necessary to PPO activity control during dehydration.
Session 88E, Fruit & Vegetable Products: Processing
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