0000000000273914
AUTHOR
Marc Hendrickx
Nonenzymatic glycation reaction of folate with reducing sugars: A case study on [6S]-5-methyltetrahydrofolate and fructose
In the Maillard reaction, free amino groups react with reducing sugars to form nonenzymatic glycation products. It has recently been shown that in the presence of reducing sugars (i.e. fructose) folic acid is subjected to a non-enzymatic glycation reaction, which may represent an important pathway of folate degradation besides the established oxidative degradation pathways. In the current study, the thermal stability of [6S]-5-methyltetrahydrofolic acid ([6S]-5-CH3H4PteGlu, 0.4µM), the predominant naturally occuring folate derivate, was investigated on a qualitative and kinetic basis in the presence of different fructose concentrations (0-3M) in milliQ water (8.11ppm O2). Samples were isoth…
Inactivation kinetics of pectin methyl esterase under combined thermal–high pressure treatment in an orange juice–milk beverage
Abstract The inactivation kinetics of PME in an orange juice–milk beverage system treated by thermal (65–80 °C) and combined thermal (25–65 °C)–high pressure (0.1–700 MPa) processes were fitted using a biphasic model. About 6–8% of the initial activity corresponding to the heat and pressure stable fraction was observed. For complete inactivation a treatment at 90 °C, 1 min or 700 MPa at 55 °C for 2 min was necessary showing the protective effect of the orange–milk media. The extent of inactivation was different in the orange matrices showing that PME was more thermostable in the orange juice–milk based beverage system as compared to the purified enzyme in a buffer system. On the other hand,…
Thermal and high-pressure stability of purified polygalacturonase and pectinmethylesterase from four different tomato processing varieties
Abstract Polygalacturonase (PG) and pectinmethylesterase (PME) were extracted and purified from four tomato varieties (Galeon, Malpica, Perfectpeel and Soto) used in the processing industry. The processing stability (thermal and high pressure) of PG and PME from the four varieties was analyzed, and they all showed the same behavior. PG was present in two isoforms, PG1 (inactivated at 90 °C, 5 min) and PG2 (inactivated at 65 °C, 5 min). In contrast, PG1s and PG2s showed the same pressure stability, both can be inactivated at room temperature in the pressure range of 300–500 MPa. On the other hand, purified PMEs could be thermally inactivated (5 min, 70 °C) but 50% of its activity remained af…