A state diagram of blueberries was developed using freezing and glass transition curves, and maximal-freeze-concentration condition in order to predict the behavior and physical changes of fresh andlyophilized blueberries. Freezing points (Clausius-Clapeyron equation) and glass transition temperature (Gordon-Taylor equation) were measured by differential scanning calorimetry (DSC). Color samples weremeasured by computer vision system. Isotherms data was fitted using GAB, Peleg and Iglesias-Chirife equations. Glass transition decreased as decreasing solids content due to water plasticizing effect. Lyophilized andfresh samples varied their color; however thermal properties were similar, principally affected by theirconstituents although the blueberry's matrix state changed. Maximum-freeze-concentration conditionswas found as X′s = 0.69 kg solid (kg blueberry)-1, T′g = -54.86°C and T′m = -45.45°C. In conclusion, a statediagram was developed using lyophilized fruit but it can be extrapolated to whole blueberry fruit.
Bibliographical noteFunding Information:
The authors acknowledge the financial supports from FONDECYT Projects Nos. 11100209 and 1110607 and Innova-Corfo 08-CT11-PUT-20.
- Computer vision system
- Sorption isotherms
- State diagram