Application of guar gum-based edible coatings supplemented with spice extracts to extend post-harvest shelf life of lemon (Citrus limon)

Guar gum based edible coatings supplemented with condiments’ extracts (methanolic and ethanolic extract of fennel, bay leaf, coriander and nigella seeds) were assayed for lemon for the maintenance of parameters that determine the quality during postharvest life. Rate of change in pH, titratable acidity and total soluble solids were studied during the shelf life of lemons. Results obtained from all the assays were communicated as mean ± standard deviation. One-way analysis of variance and t-test was employed on the studied factors at P≤0.05 to study the effect of guar gum containing extracts. The shelf life of ethanolic and methanolic extract of fennel coated lemons was significantly increased up to 24 weeks at 10 °C (85% relative humidity) while all other treatments had 15 weeks of storage stability. Treated lemons showed less changes in physicochemical attributes than both controls (untreated control; UN and treated control; GG). In addition to biochemical parameters, the storage parameters of lemon, such as antioxidant content, ascorbic acid, total phenolic content, carotenoid and chlorophyll pigments and total flavonoid content were significantly delayed in treated lemons as compared to controls. Bacterial load was also reduced in treated lemons. Coatings based on guar gum fortified with extracts could be an effective tool to delay ripening process and maintain quality of lemons during cold storage. As the constituents of these coatings are derived from food grade products, these coatings are therefore safe for human consumption and eco-friendly. These coatings not only protect the lemon from the contaminating microbes but also have bactericidal effects on the bacteria that were already present inside the lemon. Moreover, the active component of these coatings, i.e. extracts are derived from culinary spices that are easily available throughout the year.