Peel Injury on ‘Gala’ and ‘Golden Delicious’ Apples from Aqueous Hypochlorite Solutions

Experiments were conducted over several years to distinguish symptoms of sodium hypochlorite- or calcium hypochlorite-induced peel injury from other superficial maladies on ‘Gala’ and ‘Golden Delicious’ apples ( Malus domestica ), and to evaluate factors implicated in injury incidence and severity. ‘Royal Gala’ apples treated by dipping in freshly prepared aqueous sodium hypochlorite for 10 min showed moderate peel injury at the lowest treatment concentration of 150 mg·L −1 when treated immediately after harvest, whereas no injury was observed on fruit treated at even the highest concentration of 2400 mg·L −1 when fruit were kept at −1 °C for 3 months before treatment. At lower rates, rinsing fruit after treatment reduced injury on fruit dipped for 2 min, whereas after a 10-minute treatment, rinsing had no effect. Warm fruit (field heat) generally had a higher incidence of peel injury compared with fruit placed at −1 °C for 24 h before treatment. When ‘Golden Delicious’ apples were treated by dipping for 2 min in freshly prepared aqueous solutions of sodium hypochlorite or calcium hypochlorite at an equimolar hypochlorite ion concentration of 0.008 M (600 mg·L −1 sodium hypochlorite), treatment temperature had a greater influence on incidence of peel injury with sodium hypochlorite than with calcium hypochlorite. Analysis of nonpolar solvent-extractable epicuticular waxes indicated differences due to treatment among several extracted compounds. Microscopic examination of injured peel tissue indicated altered appearance of wax platelets.