Fruit quality and antioxidant properties of ‘KluaiKhai’ banana (Musa AA group) at different stages of harvest maturity

This study was designed to determine the effects of harvest maturity and harvesting season on fruit quality and shelf life and evaluate the relationship between maturity and antioxidant properties in ‘KluaiKhai’ banana (Musa AA group) for export in Thailand. Three harvest season trials (cool, summer and rainy seasons) were conducted using fruit bunches of different ages (30-50 days from removal of the blossom when the last fruit hand emerged). Fruit samples were stored at 13oC for 2 weeks to simulate export shipment and holding. Fruits were ripened with ethylene for measuring total soluble solids (TSS) and shelf life of ripe fruits. Results showed that the degree of maturity of fruits from the same bunch age differed with harvest season; fruits matured the slowest in the cool season and fastest in the rainy season. Hand weight and finger diameter generally increased with increasing harvest maturity and were highest in the most mature fruits regardless of harvest season. Fruit length did not widely vary with maturity.Similarly, TSS and shelf life of ripe fruits were not significantly affected by harvest maturity and season. Fruits were 70-80% mature, the recommended maturity for export, at 45-50, 37-40, and 33-37 days from blossom removal during the cool, summer and rainy season, respectively. A fourth trial was conducted to determine fruit quality and antioxidant properties at table ripe and overripe stages. Firmness and TSS showed no significant variations due to maturity but starch content was comparably higher in fruits harvested at 35-40 days (75-90% mature) than those at 30-33 days (60-70% mature) from blossom removal. Ascorbic acid, phenolics, flavonoids and β-carotene contents at table ripe stage increased with increasing harvest maturity while lycopene content was low and was not clearly affected by maturity. Similar trend and amount of ascorbic acid were obtained in overripe fruits but phenolics, flavonoids and β-carotene contents decreased. Ferrous ion chelating ability and DPPH scavenging activity at the table ripe stage generally increased with harvest maturity while reducing power decreased with increasing maturity. These antioxidant activities decreased slightly in overripe fruits. Ferrous ion chelating ability was higher than DPPH scavenging activity in fruits at 35-45 days from blossom removal. The results indicate the nutritional advantage of harvesting fruit at the more mature stage. Considering both export requirement and nutritional potential, fruits could be harvested when 75-85% mature.