Physicochemical evaluation of sodium hydroxide solutions for lactic acid determinations in milk

The determination of lactic acid in milk requires an aqueous solution of sodium hydroxide with a specific concentration. The most commonly used solutions are Dornic and 0.1 M NaOH. This study aimed to evaluate the physicochemical properties of two solutions with nominally different concentrations of sodium hydroxide to determine the concentration of lactic acid in bovine milk. The samples used were whole ultrahigh temperature (UHT) milk (n = 21) and semi-skimmed UHT milk (n = 12). Lactic acid determinations were carried out with Dornic and 0.1 M NaOH solutions. The results showed significant differences (p < 0.05) in the use of Dornic versus 0.1 M NaOH solutions. Accurate determination of lactic acid is important for assessing milk quality and detecting possible alterations or adulterations. An inappropriate choice of solution can lead to erroneous results, affecting the interpretation of milk quality.