Market survey for wholesome lactic acid level in evaporated and condensed milk by first derivative potentiometric titration

Abstract

Different milk products in markets in Benin City were analyzed for concentration of lactic acid as an index of compliance with permissible values. Nine (09) milk samples coded M1, M2, M3, M4, M5, M6, M7, M8 and M9 were screened and their lactic acid concentration calculated from the equivalent volumes obtained from first derivative potentiometric plots which ranges from 0.36 – 0.51% with a mean value of 0.45%. These values were compared to the approved lactic acid concentration in milk products which
is 0.14 - 0.17%. The optimum activities (pKa) of the samples assayed were M1: 6.06, M2: 6.22, M3: 5.98, M4: 5.93, M5: 5.94, M6: 6.07, M7: 6.35, M8: 6.23 and M9: 6.31. This study revealed that all the milk samples in markets in Benin City have values of lactic acid higher than the permissible range. This could be due to exposure to high temperature conditions, deterioration due to activities of Lactobacillus
bulgaricus, Lactobacillus casei and Streptococcus thermophilus and poor storage conditions. The results of this study suggest that the regulatory agencies should be proactive in sampling of milk products in the market to avoid epidemics resulting from unwholesome food products. This method can be adopted as a final check procedure for lactic acid content in milk products.