Analysis of Bovine Lactoferrin in Infant Formula and Adult Nutritional Products by Optical Biosensor Immunoassay: Collaborative Study, Final Action 2021.07

Background: Bovine lactoferrin is increasingly being used as an ingredient in infant formula manufacture to enhance nutritional efficacy through the provision of growth, immunoprotective, and antimicrobial factors to the neonate. Objective: To evaluate method reproducibility of AOAC First Action Official Method 2021.07 for compliance with the performance requirements described in Standard Method Performance Requirement (SMPR (R)) 2020.005. Methods: Eight laboratories participated in the analysis of blind-duplicate samples of seven nutritional products. Samples were diluted in buffer, and an optical biosensor immunoassay was used in a direct-assay format to quantitate bovine lactoferrin by its interaction with an immobilized anti-lactoferrin antibody. Quantitation was accomplished by the external standard technique with interpolation from a four-parameter calibration regression. Results: After outliers were removed, precision as reproducibility was found to be within limits set in SMPR 2020.005 (<= 9%) for six out of seven samples and all had acceptable Horwitz Ratio (HorRat(R)) values ranging from 1.0 to 2.1. Additionally, comparison with an alternative independent Stakeholder Panel on Infant Formula and Adult Nutritionals (SPIFAN) First Action method (heparin cleanup LC-UV), showed negligible difference between results. Conclusion: The method described is suitable for the quantification of intact, undenatured bovine lactoferrin in powdered infant formulas. The SPIFAN Expert Review Panel evaluated the method and accompanying validation data from this multi-laboratory testing (MLT) study in July 2023 and recommended Official Method 2021.07 for adoption as a Final Action Official Method(SM).