ultrasound assisted osmotic dehydration of kiwi fruit
In this study, the effect of ultrasonic pre-treatment on osmotic dehydration of kiwi slices was investigated. dehydration of kiwi fruit Kiwi fruit slices were subjected to ultrasonic pre-treatment in a sonication water bath at a frequency of 25 kHz for 20 min. Osmotic dehydration of ultrasonic pre-treated samples were conducted for a period of 300 min in 60 Brix sucrose solution. The kinetics of moisture loss and solute gain during osmotic dehydration were predicted by fitting the experimental data with Azuara's model and Weibull's model.

Kiwi fruit is one of the nutritious fruit having various phytonutrients such as phenolic, carotenoids, flavonoids, lutein and chlorophyl.Kiwi fruit is highly perishable fruit having very short shelf life. The shelf stable processed food product having sensory and nutritional characteristics similar to natural fresh fruit have high demand among the consumers. Osmotic dehydration (OD) is a process of partial removal of water from a food product through its immersion in a hypertonic solution thusproducing foods with intermediate moisture content.
The different osmotic agents implemented for dehydration of fruits and vegetables belong to different groups such as monosaccharides, disaccharides , polysaccharides, inorganic salts and large molecular weight osmotic agents,Experiments under atmospheric conditions were performed without any pre-treatment. Previously weighed kiwi slices using a digital balance were dipped into osmotic solution under varied set of temperatures for different time interval. The cases were numerically classified for the identification of each sample. After each pre-determined time interval, the samples were removed from the solution, rinsed in distilled water to eliminate the solution adhered to the surface, followed by blotting with tissue paper to remove the excess water from the surface.
Mathematical models
Empirical model were established to predict the kinetics of moisture loss and solute gain during osmotic dehydration. The empirical models used to fit the experimental data were Azuara's Model and Weibull's Model. Azuara's model was implemented for evaluation of the equilibrium values of moisture loss (WL∞) and solute gain (SG∞) during osmotic dehydration process.
The influence of ultrasonic pre-treatment prior to the osmotic dehydration of kiwi fruit induced significant changes in terms of weight loss and solid gain. The equilibrium water loss values predicted by Azuara model were 50.346 and 58.472 g/100 g of fresh fruit for the untreated and ultrasound treated samples respectively for the operating temperature of 60 °C. For solid gains the equilibrium values were 13.71 and 15.12 (60 °C temperature) under atmospheric conditions and with the aid of ultrasound pre-treatment respectively, indicating that the application of ultrasound pre-treatment caused enhanced water losses and solid gain.