Postharvest Treatment of Whole Apples in Relation to Fresh-Cut Slice Quality

'Empire' is a major apple cultivar used for slices in the North East. This apple can be usually stored for 7-8 months in controlled atmosphere (CA) before physiological disorders related to flesh browning become problems.

The objective of this study was to evaluate the effects of common commercial postharvest treatments on the development of flesh browning in whole 'Empire' and the subsequent quality of apple slices. 'Empire' apples of optimum maturity for long-term storage were harvested twice from a commercial orchard for two consecutive years. Half of the apples from each harvest were drenched with diphenylamine (DPA, ~900 ppm) and all fruit were cooled overnight to 3oC. Half of the apples from each treatment combination were then treated with 1-methylcyclopropene (1-MCP, 1 ppm for 24 hours). Apples were held in CA storage (2.5% O2 + 2% CO2) at 0.5 or 3oC for up to 9 months, plus 2 or 7 days in ambient air at the same temperature. Apples were removed from cold storage, sliced within 1 hour, dipped in Nature Seal (label rate for 2 min), and rinsed in tap water. Bagged slices were held at 3oC for 21 to 30 days and then assessed for quality based on the UC Davis Visual Quality Scores for Apple Slices.

'Empire' from the first harvest developed less flesh browning and generally produced better quality slices than those from the second harvest. DPA had no significant main effect on slice quality, although it interacted occasionally with other factors.

1-MCP treatment tended to increase apple flesh browning in long-term storage and consequently reduced slice quality at these times. Apples stored at 0.5oC were more prone to flesh browning, but those not brown produced higher quality slices compared to fruit held at 3oC.

Slices from apples kept for 7 days in cold storage prior to slicing often had higher quality scores than those held for 2 days.

The results of this study indicate that apple slice quality is dependent on the inherent susceptibility of the whole fruit to develop flesh browning in storage.