The FAST index – A highly sensitive indicator of the heat impact on infant formula model

Abstract Infant formulas are highly sensitive to the Maillard reaction during manufacturing, while this reaction induces significant loss in protein nutritional value and safety. The indicators mostly used to monitor the reaction during heat treatment are furosine, carboxymethyllysine and hydroxymethylfurfural, but analysis of these molecules is time-consuming and expensive. The FAST method, based on simple fluorescence measurements on clear milk supernatant, is a good alternative for Maillard reaction monitoring in milk products. The aim of this study was to determine the respective sensitivity of the various indicators of heat damage to infant formula, including the FAST index. A realistic infant formula model was developed, to compare the reaction kinetics at different temperatures (80–110 °C) for lactulosyllysine, measured as furosine, hydroxymethylfurfural and carboxymethyllysine. By comparing the Arrhenius plots of the three Maillard products to that of the FAST index, the latter was identified as the most sensitive indicator for infant formula quality monitoring during heat treatment.