Oxidative stability of DHA in β-lactoglobulin/oleic acid-modified chitosan oligosaccharide nanoparticles during storage in skim milk

The objectives of this research were to investigate the effects of sub-ambient temperature treatment and degree of substitution (DS) of oleic acid-modified chitosan oligosaccharide (CSO-OA) on the entrapment efficiency of docosahexaenoic acid (DHA) and oxidative stability in β-lactoglobulin (β-LG)/CSO-OA nanoparticles during storage in skim milk. Nanoparticles were prepared at various sub-ambient temperature from 5 to 25 °C with various DS from 0 to 7.4%. More than 0.2 g/L of DHA were successfully entrapped in β-LG/CSO-OA nanoparticles. An increase in the entrapment efficiency of DHA from 77.6 to 82.0% was observed as temperature was decreased and DS of CSO-OA was increased. Compared with free DHA, entrapped DHA led to a decrease in overall peroxide value from 0.690 to 0.559 and p-anisidine value from 1.159 to 0.914, and development of off-flavor compounds during 16 days of storage indicating entrapment in β-LG/CSO-OA nanoparticles can enhance the oxidative stability of DHA. A decrease in temperature and an increase in DS of CSO-OA resulted in a reduction in the formation of off-flavor compounds. In conclusions, sub-ambient temperature treatment and DS of CSO-OA were crucial factors affecting DHA entrapment efficiency and oxidative stability in nanoparticles during storage in skim milk.