The levels of trace elements are an important component of safety and quality of milk. While certain elements such as chromium are essential at low levels, an excess can result in deleterious effects on human health. International quality control standards for milk are published by the Codex Alimentarious Commission and levels of heavy metals in milk intended for human consumption are routinely monitored. This paper describes a new method for demonstrating the levels of V, Cr, Mn, Sr, Cd and Pb in raw cow's milk, using an ICP-MS. Samples (n = 24) of raw cow's milk were collected from dairy farms close to mines in Gauteng and North West Provinces of South Africa. In order to destroy organic matrix, each freeze dried milk sample was mineralised by using a microwave assisted digestion procedure. Concentrations of trace elements in digested milk samples were measured by ICP-MS. A whole milk powder reference material (NIST SRM 8435) was used to evaluate the accuracy of the proposed method. It was found that the levels of V, Cr, Mn, Sr, Cd and Pb obtained using the new method showed concordance with certified values.

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The study attempts to elucidate the metabolite profiles of seed-coats from cowpea (Vigna unguiculata L) accessions of varying phenotypes. The chemical profiles were assessed using a non-targeted approach based on reversed-phase UPLC-QTOF-MS coupled to chemometrics. A total of 34 secondary metabolites were characterized, which comprised phenolic acids, flavonoids, anthocyanins, sphingolipids and fatty acids. Selected phenolic compounds were then quantified. The chemical profiles of the test accessions were distinguished by multivariate analysis, and the results showed that seed-coat pigmentation accounted for the observed differences in metabolite profiles. Delphinidin (traces to 2257.6 µg/ g), catechin glucoside (traces to 2840.6 µg/ g), catechin (traces to 2089.2 µg/ g) and epicatechin (26.3 to 3222.7 µg/ g) contributed to the segregation amongst the studied samples. The discriminant metabolites were accumulated in larger amounts in the dark seeded cowpeas compared to the light seeded ones. The findings suggest that cowpea hulls are a natural source of bioactive compounds which could be utilized in the development of food and pharmaceutical products due to their associated health benefits.

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