Modelling of moisture sorption isotherms and glass transition temperature of spray-dried honey powder

This work intended to evaluate sorption isotherms and glass transition temperature (T-g) of spray dried honey powders produced by using three carrier agents viz. maltodextrin (MD), gum Arabic (GA) and whey protein concentrate (WPC) at different water activities. Experimental data were fitted to five mathematical models [Guggenheim, Anderson, and de Boe (GAB), Brunauer-Emmett-Teller (BET), Halsey, Oswin and Smith] among which the GAB model was found to be the best fit. The monolayer moisture content of honey powders developed with MD, GA and WPC were determined 0.066 (g water/g solids), 0.071 (g water/g solids) and 0.079 (g water/g solids), respectively. The best retention of total phenolic content, vitamin C content and antioxidant activity was observed for honey powder developed with WPC in the water activity range of 0.113-0.529. Water displayed a strong plasticizing effect on T-g with a large reduction in T-g for all honey powders, as the water activity increased.