Quantitative analysis of nutrient metabolite compositions of retail cow's milk and milk alternatives in Thailand using GC-MS

Abstract

To provide comprehensive metabolite profiles and their concentrations, this study characterized retail cow's milk and plant-based milk (soymilk and almond milk) for amino acids (AA), fatty acids (FA), and sugars. The cow's milk samples included conventional milk with different heating processes and lactose-free cow's milk. Multivariate analysis was applied to identify pattern associated with different types of milk. Principal component analysis (PCA) indicated that the plant-based milk alternatives were markedly different from cow's milk samples. This was attributed mainly to FA, particularly C18:2n-6 and C18:1 (cis-9) which were highest in soymilk and almond milk, respectively. Unlike the cow's milk samples, the plant-based milk samples exhibited greater brand-to-brand variation in metabolite concentrations. The mean concentration of total AA in soymilk samples was comparable to that in cow's milk samples, but the cow's milk samples were 1.4–6.3 times more enriched in branched-chain AA. There was no significant difference in AA and FA concentrations between conventional and lactose-free cow's milk. Heating processes of cow's milk did not result in distinct metabolite patterns. This study further showed that FA profiling could be applied to evaluating soymilk adulteration with 1 %–2 % cow's milk.