Evaluation of storage stability of dried powdered coriander, parsley and celery leaves based on the moisture sorption isotherms and glass transition temperature

Abstract

The aim of study was to evaluate the storage stability of microwave-vacuum dried (MWVD) and hot air convective dried (HACD) powdered coriander, parsley and celery leaves based on their moisture sorption isotherms and glass transition temperatures (Tg). Dried coriander, parsley and celery leaves were powdered and kept at a storage temperature (TS) of 20 °C for 10 weeks with a water activity ranging from 0 to 0.813 until equilibrium was reached. The values of coefficient of determination (R2 > 0.99) and percentage global relative square error of the approximation (4.9<GRSE<11.3%) indicate that Guggenheim-Anderson-de Boer (GAB), Peleg, Lewicki, Curie and Oswin models well described the relationship between water activity (aw) and the equilibrium moisture content (EMC) of dried materials. The variations in Tg vs. aw or EMC were adequately predicted by linear, square, polynomial, Khalloufi, Gordon-Tylor and Jenckel-Heusch models (R2 > 0.81; 2.95<GRSE<43.5%). For the optimum range of aw (0.2<aw < critical aw), dried powdered coriander, parsley and celery leaves showed the highest stability at EMC from 0.028 to 0.061, 0.022 to 0.074 and 0.027–0.064 g H2O/g DM, respectively. The optimum TS of dried powdered coriander, parsley and celery leaves was from 57.8 to 20.0, 61.3 to 20.0, and 69.8 to 20.0 °C, respectively.