Influence of wall matrix systems on the properties of spray-dried microparticles containing fish oil

Abstract

This study was conducted to evaluate the effects of the partial substitution of whey protein isolate (WPI) by inulin (IN) or maltodextrin (MD) as wall materials on the characteristics of microparticles containing fish produced by spray drying. Three treatments, WPI, WPI/MD (1:1) and WPI/IN (1:1), were evaluated in a completely randomised design with three replicates. The solubility and hygroscopicity of the particles were not affected by the wall material, attaining average values of 79% and 5.5g·100g−1, respectively. The partial substitution of WPI by inulin improved the wettability properties of the powders and reduced the occurrence of surface oil on the particles. The surface oil content was 5.6%, 6.5% and 7.7% for the particles produced using WPI/IN, WPI/MD and WPI, respectively. The particles presented smoother surfaces, with a smaller number of folds, when inulin was present. The GAB model was chosen as the model best adjusted to the isotherms, with values of moisture content on the monolayer (Xm) equal to 0.036g·g−1, 0.026g·g−1 and 0.074g·g−1 for the WPI, WPI/MD and WPI/IN microparticles, respectively. All of the powders obtained from these treatments exhibited a no crystalline structure, and the glass transition temperatures of these anhydrous powders were 168°C, 149°C and 131°C for the WPI, WPI/MD and WPI/IN microparticles, respectively. The use of inulin and maltodextrin proved to be good alternative secondary wall materials for fish oil together with WPI.