Effect of transglutaminase on Maillard browning of lactose-free milk powder
Résumé
Lactose intolerance is a clinical condition of the alimentary tract characterized by an individual's inability to digest and absorb lactose. This condition affects a non negligeable proportion of worldwide population. Thus, many dairy products have been developed by hydrolysing lactose. Hydrolysed milk in powder is not only challenging to produce due to problems related to caking, adherence to the chamber during spray drying and but also shows browning during storage. The application of enzymes such as transglutaminase (TGase) may have the potential to delay browning by rendering lysine unavailable, as it would be involved in the cross-linking process (Salunke & Metzger, 2023; Chen et al., 2021; Francisquini et al., 2024). Thus, this study aims to evaluate the impact of TGase addition on the browning of lactose-hydrolysed powders. Different skimmed milk powders (control, with lactase, with TGase, with lactase and TGase) were produced at pilot scale and stored in controlled conditions (40 °C). They were sampled at different times during storage (0, 0.5, 1, 2 months) and analysed. The degree of polymerization (DP) of milk proteins was evaluated by size-exclusion chromatography. Targeted Maillard reaction markers (lactose, glucose, glucose as precursors and furfural, 5-methylfurfural, 2-furylmethylketone, furfuryl alcohol, 5-hydroxymethylfurfural as intermediate compounds) were quantified by chromatography. The degree of browning was determined by colorimetry. This approach makes it possible to explain the individual and synergistic role of precursors and enzymes together on reaction pathways. The extent of cross-linking of proteins by Tgase was confirmed and the hydrolysis of lactose into glucose and galactose was observed as expected. The results also show the apparent difference in the rates of precursors consumption and furanic compounds generation in different powders. These kinetic data enable not only a clearer understanding of the Maillard reaction in lactose-hydrolysed milk powders but could also be used for further kinetic modelling.
