Moisture Sorption Isotherm (MSI) of Greek Yogurt

Abstract

In this study, Moisture sorption isotherm of Greek yogurt were investigated at 15°C, 25°C and 35°C using the standard, static gravimetric method. The purpose of this study was to understand the moisture behaviour of Greek yogurt and to evaluation models for prediction this behaviour. Experimental data were fitted to four models (GAB, BET, Halsey and Caurie) were tested for predicting the sorption data, the best fit as indicated by % RMSE, %RE and R2 values. The Moisture sorption isotherm (MSI) of Greek yogurt exhibited a sigmoid shape and was classified as Type II. The equilibrium moisture content increased gradually at the lower water activities followed by a steep rise at higher water activities. The BET monolayer decreased from 6.8 g of water /100g of solid at 15°C to 6.5 g of water /100g of solids at 35°C. The GAB monolayer decreased from 10.5 g of water /100g of solid at 15°C to 9.6 g of water /100g of solids at 25°C and further reduced to 9.1 g of water/100g of solids at 35°C. The bound water in Greek yogurt decreased from 13.92 % at 15°C to11.03% at 35°C. According to the study the GAB model emerged as the most effective in predicting the moisture sorption behavior of Greek yogurt.