Effects of thermal processing and fruit matrix on β-carotene stability and enzyme inactivation during transformation of mangoes into purée and nectar

Abstract

Effects of thermal mango processing on β-carotene stability and inactivation of peroxidase (POD) and polyphenol oxidase (PPO) were systematically evaluated on a laboratory scale, mimicking typical operations in continuous and small-size batch production of mango purée. Treatments comprised pasteurisation between 85 and 93 °C up to 16 min of holding time, with pasteurisation values ( P T ref = 93.3 ° C z = 8.9 ° C ) of 0.34–14.91 min, and thermal routines usually applied in enzymatic maceration for pectin degradation to standardise mango pulp viscosity. Although significant trans– cis-isomerisation of β-carotene ( P < 0.05) was shown by the formation of 13- cis-β-carotene, maximum vitamin A loss during pasteurisation of mango purée did not exceed 15.4%, owing to a total β-carotene retention of 93%. PPO was readily inactivated after 1 min, whereas residual POD activities of 4.0–6.3% were detected, even after 16 min, at all pasteurisation temperatures. To study the influence of the fruit matrix during pasteurisation, β-carotene stability was additionally evaluated at modified physical states in aqueous and in oil-in-water (o/w) emulsified model preparations. After disintegration of the mango matrix, trans– cis-isomerisation was higher than in model preparations, indicating a non-crystalline state of β-carotene in the mango mesocarp. In semi-continuous production of mango nectar on a pilot-plant scale, evaluated by stepwise process control, four heating treatments used for steam peeling, thermal inactivation of endogenous enzymes prior to enzymatic pulp liquefaction, and pasteurisation of purée and nectar, respectively, consistently resulted in a final retention of 83% of the vitamin A value of the fruit dry matter.