Resistant starch modification: effects on starch properties and functionality as co-encapsulant in sodium caseinate-based fish oil microcapsules

The properties of resistant starch (RS) modified by heating starch suspensions (Heat RS) or heating followed by microfluidization (Heat-MF RS) and their functionality as co-encapsulants in sodium caseinate (NaCas) based fish oil microcapsules (50%oil:25%NaCas:25%starch) were examined. RS modification reduced molecular weight and crystallinity of the starch, with the effects being more evident for Heat-MF RS. The properties of fish oil microcapsules were influenced by the starch type used (RS, Heat RS, or Heat-MF RS) in combination with NaCas. With both physical blends and heated mixtures of NaCas and starch as encapsulants, highest encapsulation efficiency but lowest oxidative stability was obtained for the microcapsules containing Heat-MF RS. Oxidative stability was independent of heat treatment applied to the mixtures of NaCas and starch and also not related to encapsulation efficiency of the freeze-dried microcapsules. The properties of the starch used in combination with NaCas were the major determinant of the oxidative stability, with lower molecular weight and decreased crystallinity providing less protection against oxidation.