Content of major phenolic compounds in apples: Benefits of ultra-low oxygen conditions in long-term storage

The effect of ultra-low oxygen (ULO) conditions applied during long-term storage of apples to preserve content of phenolic compounds has been studied. Contents of phenolics including gallic acid, chlorogenic acid, epicatechin, quercitrin, rutin, phloridzin, and phloretin in ten apple cultivars were determined immediately after the harvest and their changes monitored after three, five, and seven months storage in a cooled warehouse and under ULO conditions. Fast HPLC separation with UV detection using core-shell C18 column and gradient elution was applied. Different apple cultivars were tested and statistical analysis performed based on multiple hypothesis t-test with p-value cut-off adjusted by Holm-Bonferroni method. Principal component analysis was applied to further support the observations. Our results proved the benefits of ULO storage conditions for cultivars intended for longer storage. However, ULO storage conditions did not have a significant effect during short-term storage. Most of the cultivars bred for short-term storage stored in cooled or ULO conditions did not exhibit any statistical difference in the phenolics content.