Preparation of essential oil nanoemulsions and its incorporation in chitosan-based edible coating on guava

Nanoemulsions possess powerful nano-scale properties that make them attractive for diverse applications. In this work, two types of essential oil, namely clove essential oil (CEO) and lemon essential oil (LEO), were formulated into nanoemulsions using a highpressure homogeniser (HPH). The essential oils were mixed with virgin coconut oil (VCO) at different formulations to stabilise the oil from the coalition effect. The characterisation of nanoemulsions produced was done by observing the appearance of the nanoemulsions and analysing the droplet size and the stability of the nanoemulsions during 1-month storage at 25℃. The formulations with the smallest droplet size and that were stable during the storage period were then incorporated with chitosan to produce an edible coating on guava. Five samples of guava were coated with chitosan only (CH), chitosan containing clove nanoemulsion (CH-CEONe), chitosan containing clove oil coarse emulsion (CH-CEO), chitosan containing lemon nanoemulsion (CH-LEONe) and chitosan containing lemon oil coarse emulsion (CH-LEO). The microbiological analysis of all samples was determined by total plate count and yeast and mould counts. The weight loss, firmness, colour and pH of coated guavas during storage at 25°C for 10 days were also determined. The results obtained showed that CH-CEONe and CH-LEONe were significantly (p<0.05) effective in reducing the total plate counts and yeast and mould counts of guava compared to the other coatings, which help to prolong its shelf life. The nanoemulsion coatings (CH-CEONe and CH-LEONe) also slowed down the weight loss, the increase in yellowness, and the decline of lightness and greenness of guava during the storage period, hence preserving the guava better compared to those coated with chitosan only and chitosan with coarse essential oil emulsions.