Influence of osmodehydrofreezing with different sugars on the quality of frozen rambutan

The objective of this research was to study the effect of osmotic pretreatment with different sugars on the quality of frozen rambutan. Rambutan pieces were osmotically dehydrated in 50% sucrose, trehalose and maltitol solutions. The amount of water loss and solid gain during osmotic dehydration were determined. The increase of water loss and solid gain were not significantly different among the syrups ( P  > 0.05). For osmodehydrofreezing, the fruit pieces were immersed for 1 h before freezing at −40 °C with an untreated sample used for comparison. The physical and chemical properties of samples stored at −18 °C for 3, 60 and 120 days were studied. Pretreatment with sucrose received the highest scores in terms of taste, texture and acceptability. The glass transition temperature values of treated samples, especially those treated with trehalose, increased significantly compared to the untreated sample, but they were all much lower than the storage temperature of −18 °C. All of the experimental samples were in a rubbery state, and therefore the glass transition concept could not be used to predict quality.