ASSESSING FRUIT MATURITY OF TEN APPLE CULTIVARS BY INTERNAL ETHYLENE CONCENTRATIONS

The internal ethylene concentrations (IEC) in the cores of picked apple fruits were measured weekly in ten commercial apple cultivars growing in the Lleida (Spain) area during the 1986 harvest season. The IEC was compared with other maturity parameters : soluble solids and acidity. All apples maintained no or low internal ethylene concentrations during the early harvest dates. The pattern of ethylene increase depended on the cultivar. Some cultivars showed a rapid increase in ethylene production (Royal Gala, Early Red One, Law Spur, Red Winesap, Miller Sturdy Spur, Starking Delicious, Golden Smoothee). The commercial harvest date was 10–15 days after the initiation of ethylene increase, this suggests a possible use of the IEC as a maturity index for making a decision on the best harvest date. Other cultivars did not show a clear climateric ethylene increase (Idared, Granny Smith). In these cultivars it is difficult to use IEC for maturity evaluation because they produced very little ethylene. In all cultivars the pattern of decrease in acidity and increase in soluble solids seemed to occur fairly regularly independent of ethylene increase.