Discrimination of organic milk by stable isotope ratio, vitamin E, and fatty acid profiling combined with multivariate analysis: A case study of monthly and seasonal variation in Korea for 2016–2017

•δ13C, δ15N, fatty acids, and vitamin E in organic and conventional milk were tested.•Chemometric methods provided reliable chemical markers for accurate discrimination.•δ13C, δ15N, and FA contents vary significantly with the season in organic milk.•Compared to conventional milk, the mean δ13C and δ15N were lower in organic milk.•α-Tocopherol and nutritionally desirable FA contents were higher in organic milk.