THE INFLUENCE OF APPLICATION OF PRETREATMENT ON THE OSMOTIC DEHYDRATION OF APRICOTS

ABSTRACT The synergistic effect of the application of pretreatment on osmotic dehydration was investigated. Various osmotic agents such as sucrose, glucose, fructose, maltodextrin and sorbitol, and different pretreatment solutions such as 5% Na2S2O5, 5% K2S2O5, 2% ethyl oleate (EO) + 5% Na2S2O5, 2% EO + 5% K2S2O5 and 5% K2CO3 were used. The application of EO + K2CO3 in maltodextrin and the use of EO + K2S2O5 and EO + K2CO3 in sorbitol showed the best positive effect. The application of EO + Na2S2O5, EO + K2S2O5 and EO + Na2S2O5 in fructose, glucose and sucrose, respectively, showed better result than the other chemicals. Mass transfer was quantitatively investigated by means of effective diffusion and mass transfer coefficients. The effective diffusion coefficients for water and solid ranged from 0.857 × 10−10to 2.51 × 10−10 m2/s, and from 0.75 × 10−10to 2.15 × 10−10 m2/s, respectively. The mass transfer coefficients for water and solid were obtained as 1.041 × 10−4to 6.224 × 10−4 (1/s), and 10.39 × 10−4to 1.043 × 10−4 (1/s), respectively. PRACTICAL APPLICATIONS Osmotic treatment has been used mainly as pretreatment to some conventional processes such as freezing, freeze drying, vacuum drying and air drying in order to improve final quality, reduce energy costs or even to develop new products. Generally, sugar solutions are used for fruits, and sodium chloride solution is used for vegetables. Pretreatment solutions are used to eliminate microbial activity to protect the natural color of apricots. Osmotic dehydration of apricots results in a product without browning and good retention of pretreatment solutions. This product may have an increased shelf life in comparison with the nonpretreatment apricots, and may also serve as ingredient for complex foods such as ice creams, cereals and dairy and bakery products.