Effects of vapor heat treatment (VHT) on peel color, respiration, organic acid, sugar and starch contents of 'Carabao' mangoes [Mangifera indica]

The maturity of 'Carabao' mango fruits at the time of harvest was determined by specific gravity. Fruits that sank in 1% salt solution (S) were considered fully mature. Fruits that sank in water but floated in the 1% salt solution (Sw) and those that floated in water (Fw) were categorized as relatively immature. All fruits were subjected to a hot water treatment (52-55°C, 10min.) within a day of harvest. Half of the lot was subjected to the vapor heat treatment (VHT) to a pulp temperature of 46°C for 10min. ; the other half served as the untreated control. The fruits were then stored at 25°C. 1. Sw fruits attained peel color index (PCI) 5 on day 3, whereas S and Fw fruits reached PCI 4 on day 4 in control. VHT had no effect on the rate of peel color progression ; internal breakdown, anthracnose, and stem end rot did not occur in any treatments during the experimental period. 2. Starch content decreased in all fruits during storage ; VHT fruits had lower starch content than the control immediately after treatment. 3. Among the sugars in the fruit, sucrose had the highest concentration. Total sugar and sucrose contents in VHT-fruits were higher than were those of the control. 4. Citric acid concentration was highest among three organic acids ; it decreased during ripening. VHT effectively reduced citric acid in S or Sw fruits on day 1. 5. Respiration rate of fruits was unaffected by VHT.