Osmotic dehydration of lemon (Citrus limon L.) slices: Modeling mass transfer kinetics correlated with dry matter holding capacity and juice sac losses

Abstract

ABSTRACTOsmotic dehydration of lemon slices was performed using hypertonic NaCl solution. Due to low dry matter holding capacity (DHC) of lemon, the moisture loss, salt gain, and solid loss kinetics during osmotic dehydration were studied by considering the loss of juice sacs from lemon. The slices were immersed in the osmotic solutions maintained with four concentrations of NaCl (5–20%, w/v) and three temperatures (30, 40, and 50°C) for predetermined time intervals (10–180 min). The sample to solution ratio was maintained at 1:10. Azuara model based on Peleg model was used to determine the equilibrium moisture loss and salt gain. Apart from the moisture loss and salt gain, it was found that the loss of solid constituents and juice sacs from the fruit into the osmotic solution was significant. Therefore, the DHC was determined to correlate the rate of solid loss. The DHC was found to be greatly affected by temperature as lemon was less capable to withhold its cell integrity at higher temperature. A combined correlation model was used to determine the effect of osmosis time, solution concentration, and temperature on moisture loss, salt gain, and solid loss. High temperature is not preferable for osmotic dehydration of lemon as it increases losses. The optimal condition was found to be 20% salt concentration and 30°C osmotic solution for 180 min to attain high moisture loss, less solid loss, and required salt uptake within allowable limits.