Effect of CoolBotTM cold storage and modified atmosphere packaging on the shelf life and postharvest quality of collards

Abstract

Collard (Brassica oleracea var.acephala L.) is a nutritious leafy vegetable that is widely cultivated and consumed in Kenya. However, collard is highly perishable with a shelf life of one to two days at ambient conditions, which limits its consumption. Exploring storage options and packaging methods that can extend the shelf life of collards, can avert quantity and quality losses of the vegetable. This will ensure sustained income to producers and continued vegetable supply to consumers. The study aimed to evaluate the effectiveness of CoolBot^TM Technology and Modified Atmosphere Packaging (MAP) as options to preserve quality and extend the shelf life of collards. Two experiments were conducted at Kabete and Juja sub-counties using freshly harvested collards from the University of Nairobi Kabete farm. In each experiment, homogenous batch of freshly harvested collards were first divided into four batches. The vegetable batches were then subjected to two storage options (CoolBot^TM cold room; 5±2 °C, 75±20% RH, and ambient conditions; 25±10 °C, 50±15% RH), which were further split into two packaging treatments (packaged using XtendR MAP, and unpackaged). The experimental layout was a 2 by 2 factorial arranged in a completely randomized design with three replications. Measurements were performed daily to determine cumulative weight loss, yellowing, wilting and color changes. Biochemical assay was also performed to determine the changes in vitamin C and betacarotene content. Results show that CoolBot^TM cold storage extended the shelf life of collards by 6 days without MAP and 13 days with MAP, in comparison to collards stored at ambient conditions. The slow rate of deterioration under CoolBot^TM storage (with or without MAP) was evidenced by delayed yellowing, wilting, and reduced weight loss compared to ambient conditions, in the two experimental sites. The loss in vitamin C content was significantly higher (p ≤ 0.05) in collards under ambient conditions than those under CoolBot^TM storage. In ambient conditions, unpackaged collards lost 77.7% of their vitamin C content while the packaged collards lost 57.7% by end of shelf life (day four). In CoolBot^TM storage, packaged collards lost 18.4% whereas the unpackaged lost 26.3% of their initial vitamin C content. In CoolBot^TM storage, packaged collards lost 26.2% while the unpackaged lost 44.1% of their initial Vitamin C by day seven. These results demonstrate a synergistic effect of CoolBot^TM cold storage and MAP in preserving quality and extending the shelf life of collards.