Vol. 74 No: 5

Title:
Effects of hot-water treatment and storage temperature on electrolyte leakage of mangoes (Mangifera indica Linn.)

Authors:
M.O. NYANJAGE, H. WAINWRIGHT and C.F.H. BISHOP

pp: 566-572

Abstract:
Changes in electrolyte leakage were assessed on the skin, outer and inner mesocarp of hot-water treated mangoes at the end of 2, 5, 10 d during storage at 4, 9, and 13°C respectively. Batches of fruit were subjected to hot-water treatments at the following time-temperature combinations: (1) untreated; (2) 36.58 for 75 min; (3) 36.5°C for 60 min stepped up to 46.5°C for 43 min, or 46.5°C for 90 min (same heat units), and (4) 36.5°C for 75 min plus 46.5°C for 61 min or 46.5°C for 120 min (same heat units). The time-temperature combinations were designed to ensure that the fruits received heat units equivalent to about 0, ¹/₂, 1 or 1¹/₃ of (46°C for 90 min). Electrolyte leakage in fruit tissue was significantly highest in inner tissue and lowest in the fruit skin. The leakage increased in all fruit parts over time and with rise in storage temperature. Significant changes in electrolyte leakage were observed only in fruits stored at 13°C. The skin of mangoes immersed in hot water at 46.5°C for 120 min showed significantly higher electrolyte leakage compared with control and phased hot-water treatment (36°C for 60 min + 46.5°C for 43 min). Phased hot-water treatments showed lower electrolyte leakage compared with constant (one-stage) hot-water treatments and control. Fruits that received heat equivalent to 1 or 1¹/₃ of 46.5°C for 90 min through phased hot water showed lower leakage compared with constant hot water immersion at the same heat units. Linear regression of natural logarithms of electrolyte leakage against calcium contents showed a strong negative correlation. Hot-water treatment at 46.5°C for more than 60 min exacerbated the problem of fruit skin damage especially during storage at 13°C.

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