Process optimization and drying kinetics of rohu fish (Labeo rohita) using ohmic heating followed by solar drying
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Date
2018-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
India is known to be a protein deficient country. Freshwater fish is an excellent source of protein and carries a good amount of minerals and vitamins with very little fat. The fish is easily digestible but are highly perishable therefore; fish can not be stored longer under ambient condition which results in huge harvest and economic loss. Fish processing can prevent fish from deteriorating before reaching the end users. Uttarakhand has plenty of freshwater fish and requires tremendous efforts in the area of fish processing keeping the growing demands and market for future. Drying is the most common and fundamental method for post-harvest preservation. Fish drying should be encouraged at farmers’ level as well as at small industry level as the facility of cold storage, canning is beyond the reach of resource-poor marginal farmers and small-scale industries. Fish drying can be a good processing approach for enhancing the storage life of fish. Rohu is one of the most preferred fish in India, Bangladesh, Pakistan and Sri Lanka. Dried Rohu fish may have several uses such as ready to eat products and enriching snacks etc. A research work was, therefore, undertaken to standardize and optimize the ohmic heating followed by solar drying of Rohu fish muscles and to study the effect of independent variables on the quality and nutritional characteristics. The experiments were conducted for drying of Rohu fish muscles. In these process parameters, four variables at five levels were taken. Variables set for the experiments in drying was ohmic voltage (160, 170, 180, 190 and 200 V), salt (NaCl) concentration (0, 0.5, 1, 1.5 and 2%), PID controlled solar drying temperature (40, 48, 56, 64 and 72 C) and loading density of fish muscle (0.472, 0.572, 0.672, 0.772 and 0.872 g/cm2). The data from all experiments were analyzed using Design Expert 10.0.0.1 and the response functions were developed using multiple regression analysis and second-order model were fitted for each response. Drying characteristics and kinetics were also studied. All the independent parameters were observed on the all responses. Results of drying studies show that the moisture, protein and fat and content ranged from 12.66 to 15.57 % (dry basis), 44.08 to 60.88 % (dry basis) and 9.33 to 20.67 % (dry basis), respectively. Further, the FFA ranged from 0.5 to 1.8%, change in color 28.83 to 50.74 and sensory attributes (overall acceptability) ranged from 6.5 to 9.4. No microbial growth was found after the ohmic followed by solar drying of Rohu fish with optimum conditions 194 V and 0.56 % salt concentration, 59C Solar dryer temperature and 0.472 g/cm2 loading density The dried fish powder had a shelf life of 3 months as it retained the quality in terms of nutritive value.
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