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Changes in Ascorbic Acid Content of 'Elstar' and 'Jonagold' Apples Treated Pre- and Post-harvest with Ripening Inhibitors

Neuwald, D.A., Streif, J.
Acta horticulturae 2010 no.877 pp. 1275-1279
1-methylcyclopropene, air, apples, ascorbic acid, chemical inhibitors, cultivars, disease prevention, ethylene, human nutrition, ripening, temperature, trees, vitamin content
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.