Effect of Alginate Edible Coatings Enriched with Black Cumin Extract for Improving Postharvest Quality Characteristics of Guava (Psidium guajava L.) Fruit

摘要

The influence of alginate edible coatings enriched with black cumin (BC) extract was investigated to preserve the quality of guava fruits for 16 days at 11 +/- 1 degrees C and 85 +/- 2% relative humidity. The analysis of polyphenolic compounds in BC extract confirmed the TPC (28.43 +/- 1.11 mg GAE/g DM) and TFC (4.83 +/- 0.17 mg QE/g DM) with strong antioxidant activity (161.69 +/- 2.31 mu M Trolox/g DM in DPPH and 889.19 +/- 36.45 mu M Fe (II)/g DM in FRAP assays). The antibacterial activity of BC extract was also proved against Staphylococcus hominis and Escherichia coli with the inhibition zone diameter. The application of alginate coatings enriched with BC extracts suppressed the respiration rate, weight loss, firmness loss, and changes in the skin color of guavas. Fruits treated with alginate coating in a combination of BC extract retarded the ripening index of guavas till the end of the storage period compared to control samples (fruits treated with distilled water). The content of vitamin C, total phenolics, and total flavonoid in fruits treated with BC extract-loaded alginate coating was significantly higher than control, alginate with CaCl2, and alginate itself treatments. The antioxidant and antidiabetic activities in guava fruits coated with BC extract-based alginate coating were also comparatively higher than control and other treatments. The application of alginate coating enriched with BC extract was significantly delayed in total carotenoid formation in guavas since it delayed the ripening of fruits. Moreover, the concentrations of BC extract were worked in a dose-dependent manner in the coating systems in retarding respiration rate, weight loss, firmness loss, and ripening processes. These results proved that BC extract as a novel functional ingredient in alginate coatings was efficient in improving the quality of guava fruit and prolonging its shelf life.