The effects of guava leaves and avocado seed extracts on the postharvest shelf life, fruit quality parameters and degradation pattern of fresh tomato fruits as well as the relative preservation efficiencies of the extracts were investigated to ascertain their efficacy in reducing postharvest loss of tomato. Fresh tomato fruits were separately treated with the unenhanced extracts, L-ascorbic acid enhanced extracts, and the synergistic blends of the plant extracts following initial preparation by acidified-ethanolic extraction. The tomato shelf life conferred by each extract was then determined by monitoring the tomato fruits for degradation by soft rot, fungal rot and shrivelling. The study showed that L-Ascorbic acid-enhanced Guava leave extract (LAA-G) conferred both the highest mean shelf life of 63-days with a preservation efficiency of 83% while preserving tomato fruits treated with up to a maximum of 86-days, thus making it the most potent among the extracts in tomato shelf-life elongation. The potency of the extracts is in the order; LAA-G >A > LAA-AG > G > LAA-A > AG. Also, all the extracts possessed some degree of antimicrobial inhibition against Aspergillus, Rhizopus, E. coli and S. aureus but this was dependent on concentration and enhanced by treatment with L-ascorbic acid. The study found that, all extracts of P. guajava leaves and P. americana seeds possess remarkable shelf-life elongation activity, and hence, could mitigate postharvest loss of tomatoes except the heat-treated variant, which showed no shelf-life elongation activity. The marginal differences in the bioactive phytochemical compositions of the extracts suggest that the extracts may be achieving their preservative effect via a heat-labile bioactive compound that is present in all the extracts and further studies are needed to unravel this.
Ikese et al. (Wed,) studied this question.