Development and application of gelatin based edible coating containing cellulose nanocrystal in the storage of fresh cucumber

Abstract

Cellulose nanocrystal (CNC) has attracted attention in recent times because of its unique properties. In this study, the ability of gelatin based edible coating containing CNC supplemented with glycerol was investigated to extend the shelf life of fresh cucumber (Cucumis sativum) for a storage period of 14 days. CNC was produced using chemical method and characterised using X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FTIR). Filmogenic solution of gelatin was also produced by dissolving 10 g of gelatin powder in 100 ml of distilled water with 0, 1 and 4 g of CNC/10 g gel. The effect of two treatments alongside the control experiment was studied on some physicochemical and microbial assay were conducted. The result obtained indicate that the Derby Schrerer’s formula employed to calculate crystallite size of CNC yielded 5.9 nm. CNC- coated cucumber retained the green colour of cucumber in the first 7 days of storage. For each treatment, there were differences between the physicochemical parameters and the storage time. Weight loss, total soluble solids and titratable acidity effects were in direct correlation with the level of concentrations of the gelatin-based CNC. However, the level of retentions in ascorbic acid, flavonoids and alkaloids were higher in low treatment concentration (10000 ppm) than in the high concentration (40000 ppm) of the filmogenic coating material used. Results emanated from microbiological assays revealed that E. coli was found to be the predominant bacterial species identified in cucumber samples. No Salmonella sp. or Shigella sp. was isolated from the samples. Aspergillus sp. was found to be the most occurring fungal specie in the coated cucumber sample. Associated edible coating such as the gelatin-based CNC produced in this present research has provided reliable data for the shelf-life extension of fresh cucumber fruits at low concentration for a storage period of 2 weeks which could be used to extend the conservation period of fresh cucumber to support long period of time between harvest and transportation to distant markets.