[Jaffe color test-based microtechnique for determination of milk lactose].

The picric acid reaction (Jaffe test) that is widely used in clinical biochemical practice to determine creatinine has proven to be suitable for the assay of lactose in milk samples. The reaction conditions (picric acid concentration, sample heating time, etc.) were examined to optimize this method. The specificity of this color test was also studied. Other reducing sugars, as well as glucose-6-phosphate and glycerol yielded a picric acid reaction. The level of lactose in the test milk samples (n = 14) ranged from 0.120 to 0.148 mmol/l.