Developing a blood glucose meter-based method for the rapid measurement of lactose in dairy ingredients

Document Type


Publication Date



2019 American Dairy Science Association Annual Meeting:Cincinnati, Ohio


American Dairy Science Association


Journal of Dairy Science










lactose analysis, biosensor, protein ingredients


Commonly used lactose assays (enzymatic absorbance [EZ] and HPLC) for dairy ingredients are relatively expensive and time-consuming. A blood glucose meter (BGM)-based method has been used successfully as a rapid lactose assay in milk. The BGM method involves diluting the sample to an appropriate level with water or buffer, adding lactase enzyme, incubating at 40°C for ~15 min, and measuring the resulting glucose content with the BGM. A standard curve developed between the known lactose concentration and BGM reading is used to quantify lactose in unknown samples. The objective of this study was to evaluate the BGM-based lactose analysis method in whey- and skim milk-derived (WD and SMD, respectively) ingredients and was done in 4 phases. In phase 1, the effect of pH and lactose concentration on the BGM reading was investigated using a factorial design with 2 factors (pH: 6.03–6.89 and lactose: 0.2% or 0.4%) and found that BGM readings are significantly (P < 0.05) affected by pH at both lactose levels. In phase 2, the effect of total solids and ingredient type on the BGM reading was investigated using a factorial design with 2 factors (ingredient type: WD or SMD and total solids: 0–8%). It was observed that the BGM reading was significantly (P < 0.05) affected by both ingredient type and total solids. Phase 3 involved developing a linear relationship between the BGM reading and an EZ reference method to ascertain the accuracy of the proposed BGM method. Different ingredient type (WD or SMD) and total solids (0.5–27%) model solutions were measured using the BGM and EZ methods. The percent bias (BGM method – EZ method) was found to be between 2.2 and 6.8%. In phase 4, 15 samples procured from commercial sources were evaluated using the BGM method and EZ method as the reference method. High lactose (>47%) and low lactose (<13%) samples yielded absolute biases between −5.3 and 1.4% and 0.3 and 0.8%, respectively. Overall, the BGM method is a promising tool for rapid, low-cost analysis of lactose in both high-lactose and low-lactose dairy ingredients.