Effects of docosahexaenoic acid on milk fatty acid profile, fat globule size, and flavor characteristics

The n-3 PUFA, particularly docosahexaenoic acid (DHA), are crucial compounds for human health. This study investigated the effect of feeding dairy cows rumen-protected DHA (RP-DHA) on the milk fatty acid profile, active ingredients, milk fat globule size (MFG), and flavor characteristics. The results showed that RP-DHA supplementation significantly increased the ratio of eicosapentaenoic acid, docosapentaenoic acid, and DHA and decreased the content of malondialdehyde in milk. The RP-DHA significantly decreased the MFG surface area-dependent diameter D[3,2], volume-dependent diameter D[4,3], particle size parameters Dv(10), Dv(50), Dv(90), and the absolute value of zeta potential. The electronic tongue radar chart showed that the milk taste in the control group was mainly umami and sour and in the RP-DHA group was mainly salty and sweet. A total of 614 volatile substances were identified, and 68 volatile flavor compounds were selected according to the relative odor activity value. These compounds were divided into 13 alcohols, 12 aldehydes, 7 ketones, 9 esters, 10 terpenes, 3 heterocyclic compounds, 4 aromatics, 2 phenols, 6 acids, and 2 nitrogen-containing compounds. Volatile flavor analysis indicated that (-)-β-elemene and 3-methylphenol levels increased, while 5-amino-2-methyl-2H-tetrazole and pentadecanal decreased in the RP-DHA group. The results showed that RP-DHA could reduce the size of MFG and alter the milk fatty acid composition. These findings enhance our understanding of milk production using direct dietary supplementation of DHA to produce sustainable dairy products.