In the first attempt to describe the Maillard reaction, a reactive model with glycine amino-acid (H2 — Physical Chemistry — Kinetics Chemistry Question
A kinetic study of the Maillard reaction
In the first attempt to describe the Maillard reaction, a reactive model with glycine amino-acid (H2NCH2COOH) and fructose reducing sugar (C6H12O6) is considered. coffee, etc. (S. Martins et al., Trends in Food Science & Technology, 2001).
Fill in the proposed mechanism for the first step of addition of glycine on fructose that leads to an imine (acidic conditions).
Model Answer
The proposed mechanism involves addition of the glycine amino group to the carbonyl group of fructose under acidic conditions, followed by proton transfers and elimination of water to yield the imine intermediate. (Only the intermediate structures are required in the solution scheme).
Write down the rates of disappearance of Fru and I.
Model Answer
-d[Fru]/dt = k1 [Fru]^α and -d[I]/dt = -k1 [Fru]^α + k2 [I]
Controlling the pH and temperature of the chemical mixture is compelling in this study case. Choose the correct answer(s):
- Equilibrium constants can depend on pH.
- Equilibrium constants can depend on temperature.
- Rate constants can depend on equilibrium constants.
- Rate constants can depend on pH.
- Rate constants can depend on temperature.
Question text not available in source passages.
Question text not available in source passages.
Question text not available in source passages.
Model Answer
For the case α = 0: [Fru] = [Fru]0 – k1t
For the case α = 1: ln[Fru] = ln[Fru]0 – k1t
The following plot is a straight line: the assumption α = 0 is the correct one.
Question text not available in source passages.
Model Answer
By graphical calculation of the slope: k1 = 7.3×10–5 mol L‒1 h‒1
Determine graphically the value of d A470 /dt (t = 80 h) (derivative of A470 absorbance at t = 80 h) based on Fig. 2. [VISUAL]
Model Answer
By graphical measurement of the slope: dA470/dt (t = 80 h) = 0.019 h-1
Assuming that : [VISUAL] determine the rate constant k2.
Model Answer
k2 = 9.99×10-3 h-1