Changes in Ascorbic Acid Content of 'Elstar' and 'Jonagold' Apples Treated Pre- and Post-harvest with Ripening Inhibitors
2010
Neuwald, D.A. | Streif, J.
Ascorbic acid (AA or vitamin C) is essential in human nutrition because of its well known health and disease prevention benefits. Apples can be a significant source of dietary vitamin C. The AA content of two important commercial apple cultivars, 'Elstar' and 'Jonagold', was followed for a few weeks directly before harvest and during a short postharvest period in regular air at two different temperatures: for up to three weeks at 20°C and for 12 weeks at 1°C. Changes in AA were also studied after the ethylene synthesis inhibitor AVG was applied pre-harvest and ethylene perception inhibitor 1-MCP was applied postharvest. AA content in untreated fruit before harvest was approximately constant, especially for 'Elstar'. However, AVG treatments applied some three or four weeks pre-harvest to apples on the tree resulted in around 10% higher AA content at harvest. Postharvest AA degradation in both cultivars was higher at 20°C than at 1°C, with 'Elstar' decreasing by some 60 to 80% and 'Jonagold' decreasing by some 30 to 60% in the three weeks following harvest. However, fruit held at 20°C plus an ethylene inhibitor treatment maintained a higher AA content: after three weeks apples treated with 1-MCP alone or with AVG plus 1-MCP showed nearly double the amount of AA compared to the untreated control or fruit treated only with pre-harvest AVG. After 12 weeks storage at 1°C, the postharvest degradation in AA was around 40% for both 'Elstar' and 'Jonagold'. The ripening inhibitors 1-MCP and AVG alone or in combination reduced AA losses under these conditions by around 10%. In general, apples treated with AVG plus 1-MCP or, to a similar extent, treated with 1-MCP alone showed the highest postharvest AA content. Higher AA concentrations in apples seem to be more a ripening retardation effect than a specific effect of either AVG or 1-MCP.
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