Postharvest Treatment of Whole Apples Influences Browning of ‘Empire’ Slices

One of the major cultivars used for apple slices is ‘Empire’, but there are several practices that can affect whole fruit quality during long-term storage. Consequently, such factors will also influence the fresh-cut slice quality. As part of a larger project (Evaluation of New Apple Varieties and SmartFresh (1-MCP) for Fresh-cut Apple Slices) in collaboration with Dr. Peter Toivonen (AAFC, BC) and supported by Pride Pak Canada, Ontario Apple Growers, AgroFresh Inc., and the Agricultural Adaptation Council, the following study was conducted during the 2006 storage season. 

‘Empire’ apples sprayed with and without ReTain (200 ppm, 2 weeks prior) were harvested locally on September 25^th and October 2^nd. Half of the apples from each treatment were then drenched with DPA (ShieldBrite, ~900 ppm) and Mertect (0.5 g·L^-1). All fruit were cooled overnight to 3^oC and then half of the apples from each treatment combination were treated with SmartFresh (1 ppm, 24 hours). Apples were stored in standard CA (2.5% O₂ + 2% CO₂) at 0.5 or 3^oC for 6, 9, and 10 months. 

After 6 months of standard CA storage, slices made from ‘Empire’ from the second harvest (but still within the optimum maturity window) had substantially more decay development than those from the first harvest. ‘Empire’ treated with SmartFresh (1-MCP) also resulted in higher incidence of decayed slices. ReTain and DPA had no significant effects on slice browning. Slices from apples stored in CA at 0.5^oC and from fruit held for 7 days in ambient air (0.5 or 3^oC) prior to slicing had less browning than those held in CA at 3^oC and those held for 2 days, respectively. Hence, a few days of holding apples in refrigerated ambient air after CA storage appears to improve slice quality. There were no significant interactions of 1-MCP and/or DPA and/or ReTain on slice quality. Storage disorders were very prevalent in all treatment combinations after 10 months of CA storage, so no slices could be made. 

Unusual high amounts of low temperature breakdown (LTB) and core browning developed in ‘Empire’ apples in this study after 6+ months of CA storage. Confirming previous studies, there was no significant effect of SmartFresh (1-MCP) on LTB. However, apples treated with 1-MCP had more typical core browning, but less spotted core browning than those not treated. Typical core browning largely developed in CA storage at 0.5^oC, whereas spotted core browning was only found in fruit held at 3^oC. The highest incidence of spotted core browning was found in control (non-treated) apples from the second harvest. This is the first year that differences in core browning development have been observed in ‘Empire’ from CA storage, so further examination and study is required. ReTain-treated apples had less LTB and core browning, whereas DPA also reduced the incidence of these disorders, as well as decay development.

This entire study using ‘Empire’ is currently being repeated for the 2007 harvest season.