Storage stability of lokum

The storage stability of lokum is related with textural and thermal properties as a function of storage conditions (temperature and percentage relative humidity (RH)). Lokum is a high sugar containing food and it is generally stored at ambient conditions changed from region to region. In this study, the effect of these conditions (32, 53, 75%RH and 15, 25, 35°C) on textural and thermal properties of lokum was determined. Since the major deterioration factor affecting the textural property of lokum is moisture gain or loss, moisture sorption isotherms (MSI) of lokum were determined at 25°C. Glass transition temperature (Tg) of lokum stored at different RH at 25°C were determined to estimate thermal property. Oswin and Kwei Equations were the best fitting mathematical models for MSI and the relationship between Tg and water activity (aw) of lokum, respectively. Textural Profile Analyzer was used to evaluate the effect of storage conditions on textural properties. Weight changes of samples were also monitored. It was found that lokum became softer when the temperature and RH were increased besides it became harder at low temperature and RH. It was possible to state that the highest quality problem was getting softer structure which was observed in lokum samples stored at 35°C and 75%RH. The activation energies of lokum samples stored at 32%RH and 53%RH were calculated as 22.55 kJ/mol and 39.5 kJ/mol and it was determined that there was not regular changing trend in textural parameters of samples stored at 75%RH with temperature change.