Bioactive coating containing harzianic acid: Control of Fusarium oxysporum and preservation of tomato quality

Abstract

In this study, harzianic acid (HA) was produced by Trichoderma harzianum using cocoa pod husk extract as a substrate. HA was incorporated into ten hydrocolloid-based coating formulations, including guar gum, pectin, and carboxymethylcellulose (CMC). The formulations were evaluated for their efficacy against the phytopathogen Fusarium oxysporum previously inoculated on tomato fruits. Additionally, the release of HA in ethanol and water from the bioactive coating was quantified. The results revealed that the formulations exhibited HA release with significant inhibitory activity against fungal growth on tomato fruits. Furthermore, it was observed that the average release of HA was 6.61 % higher in ethanol compared to water within the first 24 h. A promising formulation containing equal proportions of guar gum, pectin, and CMC 1 % (w/v), glycerol (5 g/L), and an HA nanoemulsion (0.25 g/L) was applied to 80 ripe green tomatoes for 28 days at 25 °C (70 % RH) to analyze the influence on quality attributes and shelf life of tomatoes. The GPC-HA formulation significantly reduced both weight loss (23.26 %) and progressive degradation (33.33 %) of tomatoes when compared to uncoated fruits, while maintaining the levels of total acidity, lycopene, β-carotene, antioxidant capacity, soluble solids, and pH. Moreover, the formulation demonstrated effective microbiological control, as well as improvement in fruit color and firmness. These findings emphasize the potential of HA as a phytopathogen control agent in tomatoes. However, further studies are crucial to address the safety of HA use in food products.