Development of guar gum-based coating with castor oil for improved postharvest quality of fresh mangoes using response surface methodology

New guar gam-based coating formulation was prepared with castor oil (CO) for enhanced postharvest quality of mangoes by Response surface methodology (RSM). In this regard, the response surface methodology was used to optimize the concentrations of guar gum (GG) containing vegetable oil i.e. CO as a natural antimicrobial cross-linked with other additives, tween 80, glycerol, and calcium chloride (CaCl2) for coating mango (Mangifera indica) fruits. The effects of main coating components, GG (1–2%, w/w), CO (1–3% v/v), tween 80 (0.2–0.5% v/v), glycerol (0.3–0.9% v/v) and CaCl2 (1–2% v/v) on weight loss, pH, Titratable acidity (TA) and Total Soluble Solids (TSS) of coated mangoes were studied during 7 days of storage at 35 °C ±± 2 °C. Result showed that guar gum (1.5%), CO (2%), Tween 80 (0.35%) glycerol (0.6%) and CaCl2 (1.5%) were experimentally proven to be the best formulation. In addition, Fourier transforms infrared spectroscopy (FTIR) results showed the release products for fruit coating formulation mainly include, guar gum, galactose, mannose, ester, alkanes, glycerol, and ricinoleic acid. Moreover, the results revealed that the experimental data could be adequately fitted into a second-order polynomial model with a coefficient of determination (R2) ranging from 0.975 to 0.985 for all the variables studied. In general, GG and CO concentration appeared to be the most significant factor influencing titratable acidity and total soluble solids while CO alone has a more pronounced effect on weight loss and pH. The statistical assessment showed an insignificant difference between experimental and predicted values. Hence, the optimization study was carried out to evaluate the potential of the GG-CO coating formulation for the extension of shelf- life and maintaining the quality of mango fruits.