Vertical forced air pre-cooling of orange fruits on bin: Effect of fruit size, air direction, and air velocity

Abstract

Abstract Orange is an important commercial crop, which is being exported from Egypt. Citrus packhouses in Egypt receive, ship excessive quantity to overseas during glut. Since most of the facilities have limited refrigeration capacity to deal with this situation, one approach is to apply pre-cooling on the citrus plastic bin. These bins have more vented area and therefore represent less air resistance to refrigerated air requiring shorter time cycles. Hence, the objective of the current study was to investigate the effect of the cooling rate of the Navel orange as a function of fruit size, air direction (vertical forced and vertical induced) and air velocity, on weight loss and electrolyte leakage. A cold store with an air temperature of 4 °C was used to host the supplementary experimental set-up and provide the supply air temperature. The fruit temperature for different treatments was monitored and recorded at equal time intervals (1 min). The seven-eighths cooling times ranged from 217 to 76 min. The forced-air pre-cooling with the highest air velocity of 1 m s−1 resulted in the shortest significant cooling time in all fruit sizes. The forced air cooling at the three rates did not significantly affect either the fruit weight loss percentage or the electrolyte leakage of the three fruit sizes of navel orange after 2 weeks at 5 ± 1 °C + 1 week at room temperature. The indices presented in the present work could be used to estimate cooling time for another pre-cooling process for batch types of citrus under similar circumstances.