Postharvest physicochemical properties of cucumber fruits (<i>Cucumber sativus</i> L) treated with chitosan-lemon grass extracts under different storage durations

Abstract

The present study was carried out to evaluate the effects of chitosan-based edible coatings with lemon grass extract on the physical properties and overall acceptability of cucumber fruits stored at ambient temperature (28 ± 2°C) and 85 to 90% relative humidity for 14 days. Blends of chitosan (C) and lemon grass extract (E) were formulated as 0.5% C + 0.5% E, 0.5% C + 1% E, 1% C + 0.5% E and 1% C + 1% E. Fresh cucumber fruits were treated with the blends, while the untreated cucumber was used as the control. Physical quality parameters (weight loss, fruit firmness, colour using chromameter, and diameter) of the fruits were assessed on weekly basis during storage. The fruits were subjected to sensory evaluation after 14 days of storage using 20 member preference panel. After 14 days, weight loss was 1% for cucumber fruits treated with 1.0% C + 1.0% E, and 4% for control untreated fruits. No significant difference (P < 0.05) was observed in the firmness of all the treated cucumber fruits after 14 days, while the untreated significantly reduced by 4%. External colour analysis of L*a*b* parameters showed no significant change in L* (lightness) and a* (green to red) with the storage time (14 days) in treated fruits. However, values of b* (blue to yellow) changed significantly (p< 0.05) after 14 days in untreated control cucumber fruits. All fruits significantly decreased in diameter with days of storage; except for 1.0% C + 1.0% E treated cucumber fruits, which showed no further decrease after 7 days of storage. No significant difference was observed in the taste, pulp and peel colour, texture, flavour as well as the overall acceptability of stored cucumber fruits but the control sample was rated higher in overall acceptability. In this study, the combination of chitosan and lemon grass extract, especially 1.0% C +1.0% E as an edible coating, has proved to have great potential to preserve the physical characteristics of cucumber fruits at ambient temperature 28 ± 2°C peculiar to tropical countries. This combination gave better physical parameter results.

Keywords: Edible coatings, cucumber, lemon grass extract, chitosan, physical properties, overall acceptability