Performance evaluation of a low-cost evaporative cooling storage structure for citrus fruits in Sylhet Region of Bangladesh

Abstract

An experiment was conducted to evaluate the performance of low-cost evaporative cooling storage structures for extending the shelf life of citrus in comparison with ambient storage at the Sylhet Agricultural University, Bangladesh. A brick-walled cooler with wet river sand, clay, and zeolite mix pad material was used as a heat exchange material. The shelf life of citrus inside the structure was extended by 20–35 days relative to the ambient storage. During the summer season, the inside temperature was about 5–6°C lower than the outside temperature and relative humidity was about 10–15% higher than the normal condition. In contrast, the inside temperature was reduced to 10–11°C less than the ambient temperature in the winter season. Relative humidity was slightly increased to 20–23% at no-load condition but 16–17% in the presence of load condition. When the wind speed was high in the local area, the cooling capacity was varied from 1,176–3,461 W and the cooling efficiency was varied from 55–97% depending on these two climatic parameters. Daily data on physiological weight losses and citrus freshness were collected. Citruses such as lime (C. aurantifolia), lemon (C. limon), and citron (C. medica) were kept inside the structure for 44–45 days, with a 35-day increased shelf life. Average weight loss can be controlled inside the structure by 21–22%. However, pomelo (C. maxima) and mandarin orange can save 9–10% average weight loss, resulting in a 20–25-day shelf life when stored inside the cooler. This storage structure did not adversely affect the pH, total soluble sugar content, or titratable acidity of the juice. This structure, on the other hand, has the effectiveness of lowering the temperature and saving weight loss of citrus without the chilling injury in a cost-effective and environmentally friendly manner.