THE EFFECT OF MAILLARD REACTION AND PROTEIN CROSSLINKING ON PROTEIN DIGESTIBILITY IN JUVENILE NILE TILAPIA Oreochromis niloticus
High temperatures during the production of fish feed can induce Maillard reaction and protein crosslinking. In mammals these reactions are known to reduce protein digestibility and bioavailability of amino acids. In pigs apparent digestibility of Maillard reaction products (MRPs) ranged between 0 and 30%. In fish such information is lacking. Therefore, the aim was to study the effect of Maillard reaction and protein crosslinking on protein digestibility by determining the apparent digestibility of MRPs and crosslinked amino acids (CLAA) in Juvenile Nile tilapia. Two diets were formulated, containing either animal-based or plant-based proteins. Fish were fed restrictively and grown for an experimental period of 31 days at 24°C or 32°C. Feed and faeces samples were collected, in which Amino acids, MRPs and CLAAs were quantified using UHPLC-MS/MS. MRPs were present in both diets but the CLAAs were not present in detectable concentrations in the diet containing plant proteins. In the diet containing animal proteins, apparent digestibility coefficients for MRP FL and CLAAs LAN and LAL were approximately 80% to 90%, and thereby in striking contrast to their digestibility in pigs. Moreover, apparent digestibility of MRPs and CLAAs was similar to that of crude protein, suggesting no effect of the Maillard reaction and protein crosslinking on protein digestibility in Nile tilapia. In addition, water temperature did not affect the effect of Maillard reaction and protein crosslinking on protein digestibility. To study the role of gut microbiota in the digestibility of MRPs and CLAAs, samples for compositional analysis of gut microbiota are currently being analysed.