Effect of 1-MCP and storage temperature on 'Gala' apple grown in southern Brazil and stored under commercial conditions

Flesh browning and fungal decay are the two major causes of 'Gala' apple fruit loss after storage. Previous studies suggest increased storage temperatures for 'Gala' apple fruit diminish flesh browning and refrigeration energy consumption. However, the effects of increased storage temperature on fungal decay are unclear particularly for apple fruit produced in warmer regions. In this study we assessed effects of storage temperature on quality of 'Gala' apple fruit grown in a humid, subtropical region between the latitudes 26 and 27 degrees S. Experiments were conducted in commercial apple storage facilities in 2011, 2012, 2014 and 2016 using two controlled atmosphere (CA) rooms side by side in the middle of a corridor. One commercial storage room was used for each temperature treatment. Each storage room was loaded with fruit samples for this study plus similar to 640 t of apples for marketing. The experiments followed a factorial design with two factors: storage temperature (0.7 or 2.0 degrees C) and 1-MCP treatment (untreated control or 1-MCP). In each year, fruit samples from two (2011) or four (2012, 2014 and 2016) orchard plots were collected from bins of commercially harvested fruit within 18 h after harvest. Orchard plots were selected based on fruit firmness at harvest. In each year, fruit from half of orchard plots had higher (83.1 +/- 4.4 N) and half had lower (70.2 +/- 4.0 N) harvest firmness and were labeled as early and advanced harvest maturity, respectively. 1-MCP treatment was for 24 h, within 96 h after harvest, in a commercial storage room following commercial practice. The energy consumption associated to the refrigeration (by the evaporators fans and vapor refrigerant compression) was assessed for each storage room and year throughout the storage period. After storage, fruit harvested at early maturity had the highest firmness and least flesh browning, fungal decay, and fruit cracking. Storage temperature did not affect maintenance of fruit firmness, acidity, soluble solids content and fungal decay regardless of harvest maturity and 1-MCP treatment. Increasing storage temperature from 0.7 to 2 degrees C reduced flesh browning for fruit harvest at advanced maturity and not treated with 1-MCP. Increasing storage temperature from 0.7 to 2 degrees C reduced the energy consumption (kWh) by evaporator fans by 20.9 +/- 1% and the time the liquid solenoid valve (expansion valve) remained open by 20.3 +/- 3.9%. The result highlights the influence of harvest maturity on incidence of flesh browning and fungal decay and the potential benefit of increased storage temperature for 'Gala' apple fruit.