Leaf injury and its effect towards shelf-life and quality of ready-to-eat (RTE) spinach

Abstract

Ready-to-eat (RTE) leafy vegetables are the fastest increasing sector of the UK and Europe markets. Spinach (Spinacia oleracea) is one of the main leafy vegetables contributing to the RTE industry. Due to its tender and soft texture, spinach leaves tend to undergo different degrees of injuries during processing steps which affect their quality and shelf life. In this study, the effect of compression on quality degradation of spinach leaves during storage was investigated. Spinach leaves were subjected to compression using Universal Testing Machine where Young’s modulus for spinach in bulk amount; imitating packaged spinach in the industry was evaluated. Visual appearance was assessed by Population test where leaves were classified into categories according to degree of damage and percentage of deterioration was evaluated by analyzing RGB images using ImageJ. To understand the behavior better, microstructural property of the spinach was observed under light microscope. Organic spinach was found to be the best in resisting stress and damage compared to Teen, Salad and Baby spinach. Reducing weight of spinach inside the packaging bag, while putting appropriate weight reduced the possibility of the leaves inside the bag to be compressed due to the crowdedness inside the bag thus lowered the risk for accidental mechanical leaf damage. Including already broken leaves inside the packaging bag together with good leaves accelerates the deterioration of the whole leaves inside the bag. Halfway and complete teared leaves were found to be not acceptable to eat after 8 days of storage whereas control, undamaged and minor teared leaves were still acceptable to eat after 14 days of storage. The mechanical stress gave significant effect on the physical quality and mechanical property of spinach. Increasing the compression force did not change the cell sizes but changed the structure of the cells. This work provide basis to understand the physical quality and mechanical property of bulk spinach which can be used to improve the quality and shelf life of the packaged RTE spinach throughout the distribution chain.