Effects of evaporative cooling storage on microbiological and nutritional quality of <i>Telfairia occidentalis</i> Hook. f. and <i>Amaranthus hybridus</i> L.

Abstract

This study investigated the effect of two evaporative cooling systems (ECS) on the preservation of nutritional qualities and shelf-life of Amaranthus hybridus and Telfairia occidentalis. Samples were kept in block-in-block (BB) and metal-in-block (MB) ECS structures for up to 7 days and monitored for physicochemical, nutritional, and microbiological changes. The temperature in the ECS structures ranged from 25.8 to 28.5 °C for MB and 25.3 to 28.0 °C for BB with the highest relative humidity of more than 71.2% and 70.0%, respectively. The storage conditions for the control samples were 30.9 °C ± 1.0 °C and relative humidity (RH) of 49.3%. MB and BB extended the shelf-life of the Amaranthus hybridus for up to 4 days and Telfairia occidentalis for 7 days, while the control samples deteriorated completely by day 3. Weight loss and mineral contents were significantly higher in the control samples. The pH of all samples dropped during storage. MB-preserved samples had higher amounts of moisture, vitamin C, and carbohydrate although a general decline in these nutrients was observed throughout the storage period. The loss of minerals such as potassium, calcium, magnesium, iron, phosphorus, and sodium was observed in the samples stored under the ECS structures. Heterotrophic bacteria, coliforms, and fungal counts declined throughout the storage period, but the control samples had the highest counts, while MB had the least. MB and BB equally extended the shelf-life of the vegetables, but MB preserved the physicochemical and nutritional attributes of the samples better with lower susceptibility to microbial colonization and spoilage. The study concluded that ECS can be used as a low technology agricultural tool to provide short term preservation of vegetables, ultimately contributing to a reduction in postharvest losses.