Abstract

• Osmotic dehydration is an operation used for the partial removal of water from food tissues by immersing in an osmotic solution. It has potential advantages of less heat damage, better retention of flavour and energy saving method to produce the food products. Osmotic dehydration of fishes (Nga-yant, Snakehead Murrel) were conducted by varying the process parameters such as types of osmotic solution, size of the samples, immersion time, osmotic temperature, and sample to osmotic solution ratio. The osmo-treated dried fishes were analysed with respect to their weight reduction (WR), solute gain (SG), water loss (WL), and dehydration efficiency index (DEI).Then osmotic drying kinetics of fishes (Nga-yant) were carried out by varying the drying temperature with different drying time. The drying rate constant, k for Nga-yant was 0.0073 min-1 with drying temperature of 80ºC. Physico-chemical characteristics of osmo-treated dried fishes were also determined. The total plate counts (TPC) of osmo-treated dried, osmo-treated sun-dried and sun-dried samples were determined. These results prove that the process of osmotic dehydration has an important influence on the reduction of total number of micro-organisms in the samples. The organoleptic properties of products were also determined by the 9-Point Hedonic Scale Rating Test. The results of scores from sensory test, it was considered that the products of fishes were greater than 7, thus the osmotic dehydrated fishes were good quality products. The morphology of sun-dried samples and osmo-treated dried samples were compared by using SEM micrographs.