The impact of alginate composites enriched with spent black tea, green tea, jasmine tea, and Oolong tea wastes on the shelf-life extension of fruits and vegetables

Abstract

Bananas and tomatoes are of the most valuable staple foods in the world. They are widely cultivated in tropical countries. Freshly harvested green bananas and tomatoes are brought from the plantation field, packed and shipped to many countries such as the USA and European countries. However, being climacteric fruits, a major challenge for bananas and tomatoes supply stakeholders is the short post-harvest shelf-life due to rapid onset of ripening and undesirable ripening-associated changes, which result in their major losses. This work aimed to determine the impact of biocomposites based on spent tea waste (STW) and alginate on Cavendish banana (Musa acuminata) and tomatoes shelf-life. STW from black tea, green tea, jasmine tea, and Oolong tea were obtained through hot water extraction. The highest and lowest recoveries were recorded for green tea powder (96.0%) and Oolong tea leaf (88.33%), respectively. Composites were fabricated in sodium alginate cross-linked calcium chloride with or without STW. The STW-alginate composites were investigated for their effects on water absorptivity, gas absorptivity, and ripening of mature green bananas and tomatoes via monitoring of peel color changes visually and comparing to the standard color charts. The results indicated that the STW-alginate composites had variable effects on water absorptivity compared to the control. The spent green tea powder-alginate composite displayed the highest water absorptivity (212%). Moreover, the STW-alginate composites were able to prolong the ripening of both bananas and tomatoes stored in both plastic containers and modified atmosphere storage (MAP) bags at room temperature compared to the control. Composite enriched with spent green tea retained banana greenness for up to seven weeks compared to less than three weeks for the control. The results were consistent for follow-up study using MAP bags with banana and tomato. Specifically, compared to controlled group, green tea powder followed by Jasmine tea powder were the only two composites could extend to six weeks. Accordingly, STW-alginate composites hold potential as simple and novel bio-sorbents that can be applied in extending post-harvest banana shelf-life in a safe and sustainable manner.