An optical biosensor assay for the determination of folate in milk and nutritional dairy products

An optical biosensor assay utilising folate-binding protein was developed for quantitation of the folate content in milk and milk-based paediatric and adult nutritional products. Samples extracted in reducing buffer were enzymatically deconjugated prior to biosensor analysis. The protein-binding assay was configured under inhibition conditions, utilising a sensor surface functionalised with folic acid, and was subjected to single laboratory validation. Cross-reactivity of folate-binding protein towards the dominant folate vitamers was demonstrated. The method was compared with both established microbiological and high performance liquid chromatographic methods for a range of products. As a rapid, simple and automated technique, the method proved to be a precise and accurate alternative to conventional techniques for application in routine compliance monitoring of milk-based nutritional products.