Stability of ascorbic acid in adapted milk-based infant formulae during storage

A study was made of the effects of storage (for up to 17 months at 22 or 37 °C) on the ascorbic acid contents of four adapted milkbased infant formulae with the same composition except for the iron salt added (lactate or sulphate) and/or the vitamin E source involved ((alpha)-tocopherol ((alpha)-T) or (alpha)-tocopherol acetate ((alpha)-TAc)). Ascorbic acid was measured by a voltammetric method. The ascorbic acid contents of the formulae ranged from 0.77-0.84 g kg^-1 immediately after manufacture to 0.41-0.48 g kg^-1 after 17 months of storage. Samples stored at 22 °C had higher ascorbic acid contents than those stored at 37 °C. A multiple regression analysis performed to evaluate ascorbic acid evolution throughout storage/shelf-life and the effects of storage temperature and the different components of the samples yielded a model explaining 79.71% of the variability in ascorbic acid content. Iron lactate and (alpha)-tocopherol acetate addition afforded the best preservation of ascorbic acid content. The evolution of ascorbic acid was not linear, exhibiting an important decrease in the first month of storage, followed by stabilisation.