Determination of Lactose Concentration in Low-Lactose and Lactose-Free Milk, Milk Products, and Products Containing Dairy Ingredients, Enzymatic Method: Single-Laboratory Validation First Action Method 2020.08

BACKGROUND: The AOAC Stakeholder Panel on Strategic Food Analytical Methods issued a call for methods for the measurement of lactose in low-lactose and lactose-free products under Standard Method Performance Requirement (SMPR(®)) 2018.009. Megazyme’s Lactose Assay Kit (K-LOLAC) was developed specifically to address the need for accurate enzymatic testing in lactose-free samples. OBJECTIVE: K-LOLAC was validated for measurement of lactose in low-lactose and lactose-free milk, milk products, and products containing dairy ingredients. A single-laboratory validation (SLV) of the method is reported. METHOD: K-LOLAC is an accurate and sensitive enzymatic method for the rapid measurement of lactose in low-lactose or lactose-free products. Validation analysis was performed on a sample set of 36 commercial food and beverage products and a set of 10 certified reference materials. Parameters examined during the validation included working range and linear range, selectivity, LOD, LOQ, trueness (bias), precision (repeatability and intermediate precision), robustness, and stability. RESULTS: For all samples tested within the lower range (10–100 mg/100 g or mL), recoveries varied from 93.21–114.10%. Recoveries obtained for samples in the higher range (>100 mg/100 g or mL) varied from 94.44–108.28%. All materials had repeatability relative standard deviations (RSD(r) and RSD(ir)) of <9%. CONCLUSIONS: The commercial K-LOLAC assay kit, as developed by Megazyme, meets the requirements set out under SMPR 2018.009. HIGHLIGHTS: K-LOLAC is a robust, quick, and easy method for analysis of lactose in foodstuffs and beverages.