Seasonal variation in the composition of Irish manufacturing and retail milks - 4. Minerals and trace elements

Seasonal variation in the macro and trace element concentrations of three m anufacturing and five retail milk supplies was determined, at 3-week interv als, over a 12-month period. The concentrations of Mg, Cl, Mn, Cu, Co, I, M o, Ni, Fe and Zn did not differ between manufacturing and retail milks. Mea n (s.d.) concentrations of the elements in the order listed, for manufactur ing milk, were 110 (8) mg/I, 1040 (47) mg/l, 30 (7) mu g/l, 70 (16) mu g/l, 1 (0.5) mu g/l, 280 (7) mu g/l, 38 (1) mu g/l, 13 (3) mu g/l, 990 (279) mu g/l and 3.95 (0.38) mg/l, respectively. The Ca concentration was higher (P < 0.05) in retail than in manufacturing milk (1207 v. 1151 mg/l) and Cr co ncentration was higher (P < 0.05) in manufacturing than in retail milk (45. 6 v. 43.2 mu g/l) during the indoor feeding period (December to March). Con centrations of Cu and I in both milks were higher during the indoor period (81.5 and 398 mu g/l, respectively) than during the outdoor grazing period (June to October) (55.1 and 230 mu g/l, respectively). Concentrations of Ni were higher during the outdoor period (18.6 mu g/l) than during the indoor period (9.4 mu g/l. Concentrations of Mn, Mo and Zn showed little variatio n over the year whereas, Ca, Co, Cr and Fe concentrations' fluctuated consi derably and showed no definite trend over the year. The mineral concentrati ons were generally in agreement with previously published figures, except f or Fe, which was present at considerably higher concentrations than reporte d in other studies.