Evaluation of carboxymethyl lysine in the reaction between egg white protein and glucose in the presence of phenolic acids and evaluation of its antioxidant and antimicrobial properties and cytotoxicity

Abstract

bstract Backgrounds Maillard reaction is the most complicated reaction that occurs between reducing agent and amine groups of protein in food during heating and storage. Carboxymethyl-lysine (CML) is formed as consequent to glycation and oxidation of Maillard reaction products (MRP) known as advanced glycation end products (AGE. AGE can be divided into four categories based on fluorescent and cross-linking properties. CML, carboxyethyl-lysine, and pyrraline are important members of nonfluorescent and non-cross-linked AGE. Based on strong evidence provided in previous studies, CML is considered as a biomarker of glycoxidative, lipoxidative, oxidative, and carbonyl stress which could form in food and human body. The adverse effect of CML on human health and its involvement in incidence of diseases such as diabetes, degenerative disorders, cardiovascular or neurodegenerative pathologies, as well as bone and cartilage diseases have sparked a great deal of attention to controlling CML formation in food. Regarding food safety, the high intake value of CML is also a main concern due to increasing trend fast food consumption. There are numerous studies on the phenolic acid interaction with protein and its structural, functional and nutritional properties, but limited reports are available about its interaction with the Maillard reaction in food model systems. Material and methods: At this study the interaction of tannic acid (TA) and Gallic acid (GA) as multipurpose safe additives on CML formation level in EW and glucose Gl under heating 120°C at different time was investigated as a food model system using RP-HPLC- florescence detector. Further, the antioxidant activity, grafting degree, and fluorescence intensity of intermediate products were determined using DPPH, spectrophotometry and as well as fluorescence spectrophotometry methods. . The electrophoretic pattern, FTIR spectra were also analyzed for determining the extent of glycation in the presence of TA and GA. CML induced oxidative damage and its prevention due to the presence of TA and GA within the model system was studied in Human umbilical vein endothelial cells (HUVEC). Antibacterial effect of MRP in the absence and presence of TA and GA on Escherichia coli and Staphylococcus aureus were also studied. Results: The effect of incorporation of different concentrations of TA and Gallic acid (GA) (0.12, 0.5 and 1%w/v) in heat-treated egg white (EW) protein and glucose (Gl) (120 ◦C within 20 min) at 3:3% w/w on Carboxyl methyl lysine (CML) formation showed TA and GA at concentrations of 0.12 %w/v led to 6-folds decrease in CML content in comparison with EW-Gl where the CML level from 360 μg/ml reached nearly 50 and 42 μg/ml, respectively, after 20 min heating. The evaluation of Maillard reaction products (MRP) formation during the heating process using antioxidant activity and fluorescence intensity tests indicated that there were significant inverse relationships between fluorescence intensity and antioxidant activity in all samples especially at the first minute of the heating process. The result of FTIR and SDS-PAGE confirmed that in the presence of TA and GA, the rate of glycation of protein significantly diminished in comparison with EW-Gl. The level of intercellular reactive oxygen species in Human umbilical vein endothelial cells (HUVEC) using TA and GA-containing samples were lower than when using heat treated EW-Gl samples. Moreover, heat-treated TA and GA containing samples showed high antibacterial activities.

Conclusions: The results indicated that TA and GA have a good potential in the enhancement of safety heat-treated food products through its antioxidant and antimicrobial activities, and also preventing CML production.