Thermal properties of fruit fillings as a function of different formulations

The present study explores the heat-stability and thermo-physical parameters of apple fillings prepared with different amounts of water-binding agents (inulin, pectin and gellan gum), apple puree over a wide range of the total soluble solids content (30-70°Brix) according to a 25 experimental design with added central points. Obtained results showed that the thermal properties of apple fillings, as well as their relative bakery index, primarily depended on hydrocolloids (pectin and gellan gum) and total soluble solids in formulations. As expected, the fillings' glass transition temperatures increased with the increase of soluble solids content in the product, indicating higher stability. Separate models were developed for each thermal property as a function of weight fractions of each ingredient from the formulations of analyzed apple fillings (R2 >0.95). In addition, a direct correlation between relative bakery index of the analyzed fillings and their temperature of thermal degradation (R2 =0.97), as well as thermal resistance (R2 =0.94) displayed in the DSC curves, was found. The study highlights the characterization of filling's thermal properties as a key feature in predicting its stability during processing and storage of real bakery products.