Kinetic study on the osmotic dehydration of anchovy salted fish in binary and ternary solutions

Abstract

Most of the salted fish processing in Indonesia is still done traditionally by relying on sunlight. Although this method is cheap, it can decrease the quality of the product because the rate of dehydration cannot compete with the decay of the fish. The use of salt improves the speed of water extraction but to some extent it creates a problem with the texture and the taste. The goal of this study is to improve the anchovy preservation process, to maintain and standardize its quality during processing and to reduce the energy use, by studying the kinetics of osmotic dehydration of that fish. The variables used in this research are the variation of osmotic solutions (NaCl in water - binary solution and NaCl + sucrose - ternary solution), the concentration of the binary solution (15 %, 24 % - saturated, and 50 %), and process temperature (atmospheric temperature and 40 °C). The ternary solution was only applied at the concentration of 24 % NaCl. As a comparison the fish was also treated by salting directly with 10 and 35 %-wt. of food grade salt to the total weight of fish, the more usual preservation method. The results of this study indicate that the loss of water from and the diffusion of salt into the fish substrate increase in parallel with the increase of the osmotic solution concentration and temperature. The effect of temperature on very high NaCl concentration (50%) of the osmotic solution is not significant however. In addition, the use of ternary solution increases the loss of water and also reduces penetration of salt. Abstrak : Most of the salted fish processing in Indonesia is still done traditionally by relying on sunlight. Although this method is cheap, it can decrease the quality of the product because the rate of dehydration cannot compete with the decay of the fish. The use of salt improves the speed of water extraction but to some extent it creates a problem with the texture and the taste. The goal of this study is to improve the anchovy preservation process, to maintain and standardize its quality during processing and to reduce the energy use, by studying the kinetics of osmotic dehydration of that fish. The variables used in this research are the variation of osmotic solutions (NaCl in water - binary solution and NaCl + sucrose - ternary solution), the concentration of the binary solution (15 %, 24 % - saturated, and 50 %), and process temperature (atmospheric temperature and 40 °C). The ternary solution was only applied at the concentration of 24 % NaCl. As a comparison the fish was also treated by salting directly with 10 and 35 %-wt. of food grade salt to the total weight of fish, the more usual preservation method. The results of this study indicate that the loss of water from and the diffusion of salt into the fish substrate increase in parallel with the increase of the osmotic solution concentration and temperature. The effect of temperature on very high NaCl concentration (50%) of the osmotic solution is not significant however. In addition, the use of ternary solution increases the loss of water and also reduces penetration of salt.