Determination of Acidity in Donor Milk: Comparison of Results Obtained by 2 Different Analytical Methods

Background: There is no uniformity among milk banks on milk acceptance criteria. The acidity obtained by the Dornic titration technique is a widely used quality control in donor milk. However, there are no comparative data with other acidity-measuring techniques, such as the pH meter. Objective: The objective of this study was to assess the correlation between the Dornic technique and the pH measure to determine the pH cutoff corresponding to the Dornic degree limit value used as a reference for donor milk quality control. Methods: Fifty-two human milk samples were obtained from 48 donors. Acidity was measured using the Dornic method and pH meter in triplicate. Statistical data analysis to estimate significant correlations between variables was carried out. The Dornic acidity value that led to rejecting donor milk was >= 8 Dornic degrees (degrees D). Results: In the evaluated sample size, Dornic acidity measure and pH values showed a statistically significant negative correlation (tau = -0.780; P = .000). A pH value of 6.57 corresponds to 8 degrees D and of 7.12 to 4 degrees D. Conclusion: Donor milk with a pH over 6.57 may be accepted for subsequent processing in the milk bank. Moreover, the pH measurement seems to be more useful due to certain advantages over the Dornic method, such as objectivity, accuracy, standardization, the lack of chemical reagents required, and the fact that it does not destroy the milk sample.