摘要：For lactate determination in milk and milk powder, application of enzymic method using lactic dehydrogenase (LDH) was studied. After clarification of milk (or reconstituted milk) with zinc sulfate and potassium ferrocyanide, the test solution thus obtained was mixed with pH 9.5 buffer composed of 1.0 M glycine and 0.4 M hydrazine. NAD, and L- and D-LDH were added, mixed, and incubated for 30 min at 37°. The lactic acid/lactate content was estimated from NADH formed which was determined by spectrophotometry at 340 nm. Although the results from contemporary international standard method (colorimetry) and the present method were not significantly different, the enzymic method was found to be better than the former in reproducibility. Comparative results on 16 kinds of commercial milk and milk powder are shown for reference.
