Role of glycated caseinate in stabilisation of microencapsulated lipophilic functional ingredients

The aim of the present study was to investigate the possible impact of the antioxidative activity and the altered technological properties of glycated caseinate on the oxidative stability of microencapsulated fish oil. Glucose, glucose syrup or dextrans were used for glycation of caseinate and the resulting blends were intensively characterised prior to their use for microencapsulation. After microencapsulation, hydroperoxide and propanal content of the encapsulated fish oil was monitored over a period of up to eight weeks. Heating in aqueous solution, but not dry heating, led to an increase in redox-active compounds in the caseinate–glucose syrup-based carrier matrix and in an increase in oxidative stability of the encapsulated oil. In contrast, microencapsulation in a dry-heated caseinate–glucose blend did not increase oxidative stability compared to the unheated carrier system although the content of redox-active Maillard reaction compounds was increased. Oil droplet size did not significantly change when using glycated caseinate and thus, neither an antioxidative effect of Maillard reaction products nor an improved emulsifying activity is responsible for the increase in oxidative stability. Results of the present study rather indicate that the molecular weight profile of the carrier matrix is one of the key determinants for the oxidative stability of the encapsulated oils.