Identification of open lenticels in apples after harvest in relation to lenticel breakdown development during storage

• SO2 treatment on apples bleached few of the lenticels, detecting open ones.
• Postharvest calcium chloride treatment resulted in more open lenticels.
• Open lenticels at harvest correlated with LB after storage.
• The proposed SO2 method may help in deciding apple storage duration.

Lenticel breakdown (LB), appearing as dark brown pits on apple skin, occurs following storage, and the factors associated with LB have not yet been identified. It was assumed that open lenticels at harvest and following postharvest treatments contribute to this phenomenon and therefore a method was developed using SO2 treatment, to detect air-exposed tissue in Red Delicious apples. The efficiency of detection was assessed on artificial openings, created by pricking the apple surface, which caused bleaching around these openings with enlargement of their dimensions. Similarly, SO2 treatment of intact apples caused a bleaching around few of the lenticels, indicating that the underlying parenchyma cells were exposed to air. The percentage of open lenticels decreases after harvest during cold storage. A calcium chloride, but not potassium chloride, immersion at harvest resulted in significantly more SO2 damaged lenticels, indicating that calcium enhances lenticel opening. There was a high correlation between the percentage of open lenticels at harvest and the severity of LB after storage (Pearson’s correlation coefficient of r2 = 0.80). This suggests that LB might occur due to exposure of parenchyma cells to air at harvest. In conclusion, these results indicate that the SO2 treatment at harvest might be used as an efficient method for the prediction of lenticel damage after storage.