Determination of Lactose in Lactose-Free and Low-Lactose Milk, Milk Products, and Products Containing Dairy Ingredients by the LactoSens®R Amperometry Method: First Action 2020.01

Background: The AOAC Stakeholder Panel on Strategic Food Analytical Methods approved Standard Method Performance Requirements (SMPR (R)) 2018.009 for lactose in low-lactose or lactose-free milk, milk products, and products containing dairy ingredients. The LactoSens (R) R Method is a biosensor assay kit developed for the determination of lactose in a variety of lactose-free or low-lactose milk, dairy, and infant formula products produced with yeast-neutral lactases. Objective: In response to a call for methods, the LactoSensR method was validated in a single laboratory study with comparison to SMPR 2018.009. Method: The LactoSensR method was evaluated for calibration, interference, repeatability, recovery, and robustness. In a method comparison study samples naturally containing low levels of lactose were evaluated using LactoSensR and an accredited high-performance anion-exchange chromatography with pulsed amperometric detection. Results: Calibration with lactose standard solutions was shown to be linear and the method was shown to be free of interference from a variety of sugars, vitamins, alcohols, flavorings, and other compounds. Matrix studies, including 85 spiked materials, 55 products naturally containing lactose, and 13 reference materials, resulted in RSDr of 0-10.5% at 8-100 mg lactose/100 g and 0.2-5.4% at >100 mg lactose/100 g for milk and dairy products and 1.0-6.8% for infant formula, in 3 compliance with SMPR 2018.009 with few exceptions. Recovery was 85.0-110.3% at 8-100 mg lactose/100 g and 85.6-109.7% at >100 mg lactose/100 g for milk and dairy products and 91.1-97.0% for infant formula, also meeting the performance IV requirements with few exceptions. The method was shown to be robust to changes in ambient temperature, sample temperature, and sample volume. Conclusions: The LactoSensR method compares favorably with the requirements of SMPR 2018.009 and should be adopted as a First Action AOAC Official Method(SM). Highlights: The LactoSensR method is a fast, easy-to-use method that meets the requirements of SMPR 2018.009.