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Effect of the type of carbohydrate on the DVS critical relative humidity in spray-dried fat-filled pea protein-based powders: Comparison with monolayer coverage and Tg values

Domian, Ewa, Brynda-Kopytowska, Anna, Cieśla, Jolanta, Ostrowska-Ligęza, Ewa
Food hydrocolloids 2017 v.73 pp. 335-343
experimental design, hydrocolloids, inulin, lipid content, models, oils, peas, powders, rapeseed, relative humidity, soluble fiber, spray drying, total solids, trehalose, water activity, water content, water vapor
The objectives of this study were to: (1) determine the critical relative humidity (RHc) using DVS ramping for spray-dried fat-filled pea protein-based powders formulated with different types of soluble fiber as a carbohydrate component and different oil types, and (2) compare the RHc values to the monolayer coverage values obtained via DVS water vapor isotherm, as well as the MDSC Tg values. The experimental design included three compositional variants of powders, where the oil fraction was made up of the blend of palm and rapeseed or rapeseed at different ratios (52.5% or 35% w/w total solids). Each group of model powders was formulated with four different carbohydrates (Nutriose, inulin, polydextrose, and trehalose), wherein a carbohydrate-to-protein-material ratio was at 5.3:1 in all cases. Results demonstrated that changes of the RHc of spray-dried fat powders were significantly affected by the type of carbohydrate. Neither fat type nor fat content had a significant effect upon the RHc of powders. Powders with Nutriose showed the highest RHc at 25 °C (70–80%), followed by powders with inulin (RHc 30–40%) and powders with trehalose and polydextrose (RHc 30–35%). A strong positive correlation was found between RHc and the monolayer coverage values obtained via DVS water vapor isotherm, as well as the MDSC Tg values. In addition, a strong negative correlation was demonstrated between RHc and specific water activity “as is” for powders after their spray drying. In turn, no correlations were found between moisture content in powders after their spray drying and RHc, the monolayer coverage values, as well as the MDSC Tg.