Standardisation of wax coating in cassava (manihot esculenta crantz) tubers and quality evaluation

Abstract

The present study entitled “Standardisation of wax coating in cassava (Manihot esculenta Crantz) tubers and quality evaluation” was undertaken to standardise the percentage of wax coating to be applied on cassava tubers and to evaluate various physico-chemical and nutritional attributes of wax coated cassava tubers. Three varieties of cassava, M-4, Sreevijaya and Vellayani Hraswa were selected for the study. The standardisation of wax coating was done by using different concentrations of three waxes namely paraffin wax, bee wax and semperfresh on these varieties. The wax formulation at one per cent level which prolonged the days of storage under ambient conditions was selected for the study. The tubers coated with one per cent wax formulations were stored after packing in ventilated paper cartons under ambient conditions till it showed the signs of deterioration. The shelf life qualities such as respiration rate and physiological loss in weight and physical qualities like appearance, colour and extent of vascular streaking were determined at two days interval. The chemical, nutritional and organoleptic qualities were evaluated initially and after two weeks of storage. The respiration of the cassava tubers were determined by the rate of O2 consumption and CO2 liberation. Significant variation was noticed in the respiration rate of unwaxed and wax coated cassava tubers. The respiration rate lower than control was observed only in semperfresh coated tubers throughout the storage period. The physiological loss in weight was minimum in unwaxed tubers followed by semperfresh treated ones except in variety Sreevijaya. In paraffin and bee wax coated tubers the development of vascular streaking and discolouration was at a faster rate than in semperfresh coated and unwaxed tubers. Paraffin and bee wax coated tubers of Sreevijaya and bee wax coated tubers of M-4 showed symptoms of deterioration during second week of storage itself. Changes in chemical and nutritional constituents were observed during storage of waxed cassava tubers. In tubers treated with semperfresh, the rate of moisture loss was comparatively lower during storage. A reduction in protein content was noticed during storage of waxed as well as unwaxed tubers. The fat and fibre content of all the treatments increased during storage. Among wax coated tubers, semperfresh coated tubers showed minimum loss in total carbohydrate content during storage. A significant reduction in starch content during storage was noticed in waxed as well as unwaxed tubers resulting an increase in the total and reducing sugar content of all the treatments. The physico-chemical characters of the tubers were found to be better retained in semperfresh tubers than in control. β-carotene content was noticed only in variety Sreevijaya which decreased significantly during storage. A slight increase in calcium content of waxed and unwaxed tubers was observed during storage. Nearly 18 percent reduction in hydrogen cyanide content was noticed in waxed and unwaxed tubers of the three varieties. The mean scores for different quality attributes of waxed as well as unwaxed cassava tubers of M-4, Sreevijaya and Vellayani Hraswa decreased during two weeks of storage. Compared to control, the mean scores for overall acceptability were lower in wax coated cassava tubers. Among wax coated tubers, semperfresh tubers had better mean scores for different quality parameters. The cost of wax application was found to be maximum for semperfresh, followed by paraffin and bee wax. From this study, it is clear that all types of waxes are not ideal for application in cassava tubers. Among the three types of waxes tried, semperfresh was found to be the most ideal one for application on cassava tubers. But the extended shelf life by application of semperfresh was found to be almost similar to the shelf life of unwaxed tubers. So it can be concluded that harvesting cassava tubers without any mechanical damage and bruises itself is ideal to extend the shelf life.