Dynamic changes in wax and cutin compounds and the relationship with water loss in 'Red Fuji' and 'Golden Delicious' apples during shelf life

Knowledge of the dynamic composition changes of combined cuticular wax and cutin in apples during their shelf life is scarce. Therefore, this issue was addressed using GC-MS analyses of the respective epidermal components in 'Red Fuji' and 'Golden Delicious' apples at 5 days intervals during the shelf life of 25 days. Water loss from the apples was also assessed. The proportion of total n-alkanes decreased in cuticular wax, whereas total acids increased gradually, and cutin monomer content significantly changed during the first 5 days. The predominant wax compound, nonacosane (C-29), decreased by 40.13% and 26.22% in 'Red Fuji' and 'Golden Delicious' apples, respectively. The cutin monomers 10,16-dihydroxy hexadecanoic acid (10,16-diOH C-16:0) and 9,10,18-trihydroxyoctadecanoic acid (9,10,18-triOH C-18:0) were detected only at the beginning of shelf life in apples of both cultivars. Regression analysis indicated that the rate of water loss significantly correlated with eight components. Our results expand the understanding of the dynamics of both wax and cutin compounds in postharvest apples and help to target specific compounds to maintain the quality of apples throughout their shelf life.