Abstract:
Quality issues in cucumber during postharvest handling in tropics and subtropical regions including Nigeria are fruit discoloration, shrivelling and physiological deterioration due to undesirable temperature. The effect of chitosan (C) and lemongrass extract (E) on the physicochemical properties, microbial assessment and overall acceptability of cucumber fruit stored at ambient temperature (28 ± 2 oC) and 85- 90% Relative Humidity (RH) for fourteen (14) days were investigated. Fresh cucumber fruits were treated with mixtures of 0.5% C + 0.5 % E, 0.5% C + 1% E, 1% C + 0.5 % E, 1% C + 1% E, while the untreated cucumber was used as the control. The result revealed that percentage weight loss ranged between 1% and 6%, the least percentage weight loss was observed in cucumbers treated with 1.0% C and 1.0% E. Firmness were significantly retained in all chitosan and lemongrass treated cucumbers while there was a significant reduction in the untreated sample from 52.52 (day 0) to 50.32 (day 14). There was no significant change inL* values of the cucumber treated with 0.5%C + 0.5%E, 0.5%C + 1%E, 1%C + 0.5% E and untreated, during the period of storage. Statistical analysis shows no significant difference in a* values within the treated and untreated samples. Also, there was no significant change in b* values of 0.5%C+ 0.5% E as well as 1%C + 1%E treatment. The diameter of the cucumber samples decreased during storage, as storage days proceed except for 1% C + 1% E, where the decrease was observed on day 7, and it was maintained through the storage period. There was no change in the length of treated and untreated cucumbers during storage. At the end of the storage, the titratable acidity of cucumber fruits decreased in both treated and untreated samples. Percentage decrease ranged from 14% (0.5%C+1%E) to 42% in 1%C+0.5%E. Total soluble solids (TSS) increased and later decreased in all the samples during storage, percentage decrease ranged from 7% in control untreated cucumber to 23% in 1%C+0.5%E and 1% C+ 1%E. TSS was higher in chitosan and lemongrass treated cucumbers than in the control. No significant difference was observed in the taste, pulp colour, peel colour, texture, flavour and the overall acceptability of stored cucumber fruits. The microbial flora responsible for spoilage of cucumber fruits after storage are: bacteria (Stapylococcus aureus, Bacillus subtilis and Micrococcus luteus) and fungi (Fusarium verticillioides, Mucor hiemalis, Rhizopus stolonifer, and Aspergillus fumigatus). The results revealed that, the application of 1.0% C and 1.0% E as an edible coating in cucumber fruits stored at ambient temperature (28 ± 2 oC) was significantly better in maintaining the cucumber fruit quality, for fourteen days.
