Glass transitions and state diagrams for fresh and processed apple

Differential scanning calorimetry (DSC) was used to measure phase transitio ns in samples of Golden Delicious apples after freeze-drying and osmotic dr ying in a sucrose solution. From DSC traces, glass transition (T-g) and mel ting (T-m) temperatures were obtained and used to plot the state diagrams f or the two types of samples. The Gordon-Taylor equation was able to predict the dependence of the glass transition temperature on moisture content. Be fore calorimetric analysis, dehydrated samples were equilibrated under a wi de range of different relative humidities (a(w) 0.12-0.93) and sorption iso therms determined. Experimental sorption isotherms agreed with previous res ults reported in the literature. (C) 1999 Elsevier Science B.V. All rights reserved.