Ameliorating effects of anthocyanin addition on protein oxidation and its induced intestinal microbiota disturbance in spray-dried milk powder

Spray-drying induces milk protein oxidation, and plant-derived anthocyanins show protective antioxidant effects. This research explored the effects of anthocyanin addition on protein oxidation and its induced intestinal microbiota disturbance in spray-dried milk powder. The results showed that spray-drying induced protein oxidation and the generated oxidized proteins caused gut microbiota disorders in an in vitro anaerobic fermentation model. Anthocyanin addition inhibited aggregation and cross-linking of protein macromolecules, reduced the levels of representative protein oxidation products (carbonyls, advanced glycation end products, and Schiff bases), and increased the free sulfhydryl content. Anthocyanin addition also increased the specific amino acid levels (tyrosine, methionine, cysteine, and aspartic acid) and decreased the representative amino acid oxidation product levels (dityrosine, kynurenine, and N'-formylkynurenine) in milk powder. The addition of anthocyanin mitigated the occurrence of protein oxidation, and when these proteins with low-oxidation were fermented with human gut microbiota, the abundance of beneficial bacteria, particularly Bifidobacterium , Phascolarctobacterium , Alistipes , and Candidatus soleaferrea , was increased. Moreover, anthocyanin addition enhanced the radical scavenging ability of spray-dried milk powder and its protein fermentation broth, which may be a key factor in the aforementioned beneficial effects. This study provides new insights for ameliorating the protein oxidation and its induced intestinal microbiota disturbance by adding anthocyanin in spray-dried milk powders and lays a theoretical foundation for using natural plant compounds to inhibit protein oxidation during the spray-drying process. • Anthocyanin inhibits the aggregation and cross-linking of protein macromolecules. • Anthocyanin reduces the levels of representative protein oxidation products. • Anthocyanin decreases the representative amino acid oxidation product levels. • Anthocyanin counteracts the oxidized protein-induced gut microbiota dysbiosis. • Anthocyanin increases the abundance of Bifidobacterium and Phascolarctobacterium .