Evaluation of storage stability of dried cranberry powders based on the moisture sorption isotherms and glass transition temperatures

Abstract

The aim of this study was to evaluate the storage stability of dried cranberry powders based on the moisture sorption isotherms and glass transition temperature (T_g). Microwave-vacuum dried (MWVD) and hot air convective dried (HACD) cranberry powders were kept at storage temperatures (T_S) of 10, 20, 30 °C. Based on the coefficient of determination (R² > 0.99) and percentage global relative square error (1.2 < GRSE < 3.7%) of the approximation it can be stated that Guggenheim–Anderson–de Boer (GAB), Lewicki and Peleg models well described the relationship between water activity (a_w) and the equilibrium moisture content (EMC) of dried material. Storage temperature and drying method did not significantly influence the sorption isotherms of cranberry powders. The variations in T_g vs. a_w and T_g vs. EMC were adequately predicted by Khalloufi, linear (R² > 0.98; 1.8 < GRSE < 13.7%), square and Gordon–Tylor (R² > 0.89; 18.0 < GRSE < 34.6%) models, respectively. The optimum a_w, EMC and T_S for storage of MWVD and HACD cranberry powders were 0.30, 0.056 g H₂O·g⁻¹ DM, ≤ -2.6 °C, and 0.30, 0.055 g H₂O·g⁻¹ DM and ≤ -0.7 °C, respectively.

KEYWORDS:

• Sorption isotherms
• glass transition temperature
• convective drying
• microwave-vacuum drying
• mathematical modeling

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This study was supported by the Polish National Science Center (grant No. 2015/17/B/NZ9/03601, title: The effect of unconventional pretreatment methods on the kinetic of hybrid dehydration and physical and chemical properties of cranberries Vaccinum macrocarpon) and partially by the University of Warmia and Mazury in Olsztyn (grant No. 16.610.001-300).