Optimisation of Edible Coating to Improve the Postharvest Shelf-life of Guava Using Response Surface Methodology

The effects of composite edible coating consisting of gum Arabic, beeswax and coconut oil on Cambodia cultivar guava (Psidium guajava) were evaluated using response surface methodology (RSM). The optimum coating formulation was determined using the weight loss percentage and total soluble solid (TSS) content as the responses. From the central composite rotatable design in RSM, a total of 15 sets of coating compositions were designed. The optimised coating emulsion was made up of gum Arabic (6.6% w/v), beeswax (5.5% w/v) and coconut oil (3.6% w/v) with Tween 80 (3% w/v) as surfactant. Under this optimised coating emulsion, the predicted mean values of weight loss and TSS were 2.91% and 7.84oBrix respectively, whereas the actual mean values of guava samples were 3.38% and 8.00oBrix respectively, after 6 days of ambient storage. The actual mean values of both responses were within the 95% prediction interval, which was 2.35 – 3.47% for weight loss and 7.22 – 8.45oBrix for TSS. The optimised coating emulsion successfully reduced weight loss with maximised TSS content for guava.