Bellion, Ian Richard (1992) Kinetics of the Sulphite- Inhibited Maillard Reaction. PhD thesis, University of Leeds.
The kinetics of the inhibition of Maillard browning of glucose and glycine by suIphur(IV) oxospecies, S(IV), are reported in detail in water, and solutions containing either 40% w/w ethanol, 40% w/w polyethylene glycol 400 or up to 81.5% w/w glycerol. The progress of the reaction was followed by measuring free and reversibly bound S(IV), production of H+ and formation of sulphate ion. Equilibria between S(IV)-species were investigated by Fourier Transform Infrared (FTIR) Spectroscopy. Kinetic data show that despite earlier reports demonstrating a lack of an effect of pH on this reaction, maintaining of reaction mixtures at a constant pH causes considerable increases in rate. Overall the kinetics support the following 3-step mechanism, [diagram available in .pdf] S(IV) glycine hydroxysulphonate hydroxysulphonate hydroxysulphonate where DH, DDH and DSH represent 3-deoxyhexosulose, 3,4-dideoxyhexosulos-3-ene and 3,4-dideoxy-4-sulphohexosulose. Some autoxidation of S(IV) also takes in practice. The kinetically measured dissociation constant of the hydroxysulphonate of DH is found to be 0.28 M and this is the first report of kinetic evidence for such an interaction in the S(IV)-inhibited Maillard reaction. Hydrogen ion production during the reaction is the result of a condensation reaction between glucose and glycine, and autoxidation of S(IV). FTIR spectroscopy shows that addition of glycerol as a humectant does not cause the expected conversion of HSO3-t0 S2O52- in solution. Instead new species, e.g. ion pairs such as NaS205_, are formed and S2O52' is probably less important in concentrated foods, than once thought. The effect of humectant is to increase both k] and k2 (aw 1-0.43) and the effects are explained in terms of equilibria involving water as a reactant and interactions between transition states of the solvent.
|Item Type:||Thesis (PhD)|
|Academic Units:||The University of Leeds > Faculty of Maths and Physical Sciences (Leeds) > The Procter Department of Food Science (Leeds)|
|Depositing User:||Digitisation Studio Leeds|
|Date Deposited:||10 Jul 2012 12:10|
|Last Modified:||08 Aug 2013 08:49|