Physico-chemical changes of gluten matrix as a result of maillard reaction with glucose
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Date
2006
Authors
Md. Abu Hanif
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Abstract
The present study was undertaken with the objective of elucidating the effect of
sugar-protein interactions on the physicochemical properties of gluten matrix.
Studies were conducted using Differential Scanning Calorimetry, Texture
Analyzer, Colorimeter and Spectrophotometer to observe the effects of various
sugars (glucose, xylose and sucrose) on the wheat gluten proteins during the
Maillard reaction. The DSC studies revealed that the thermal denaturation
temperature of wheat gluten proteins increased in the presence of glucose and
sucrose, and this was probably due to their (the sugar) ability to stabilize the
native wheat gluten. However, wheat gluten proteins containing glucose and
sucrose did not show any cross-linking (exothermic) transition. Wheat gluten
protein (WG) gels with or without reducing sugars were prepared by heating the
dispersions in sealed cans in a laboratory size autoclave at 121oC for 30 min.,
followed by curing treatment at 4 oC for 18 h. The Maillard reaction caused a
significant (p< 0.05) change in colour, a decrease in pH and increase in
browning. In the process the loss of available lysine ( 48%) and loss of glucose
( 62%) showed that these were implicated in the reaction, on the other hand
there is no loss of sucrose suggesting that sucrose was not implicated in the
reaction. Gelling of wheat gluten with glucose (WG-G) showed much less
syneresis compared to that with sucrose (WG-S) and without any sugar (WG).
The WG-G gels also showed higher water holding capacity (WHC) in
comparison to that of WG-S and WG gels. The improved syneresis and WHC of
WG-G gel may be attributed to the higher net charge on the protein molecules
as a result of the Maillard reaction. Rheological gel properties of wheat gluten
protein gels were studied by Texture Analyzer. The stress relaxation
experiments of the gels in compression were measured and the response
analyzed using Peleg's equation. The parameters in this equation, the gel
elasticity (K1 & K2) showed strong dependency on the sugar systems. The WGG
gels were more elastic than the WG-S & WG gels. It follows that, the gel
break strength and asymptotic residual modulus of the WG-G gels were higher
than those of the WG-S & WG gels. It was suggested that WG-G heat-induced
gel (Maillard gel) had a significant (p< 0.05) improvement in the gel strength
and viscoelastic properties which may contain additional nondisulphide covalent
crosslinks ("Maillard cross-links") within the gel network. Studies on protein
solubility in disrupting solvent (2% sodium dodecyl sulphate + 2% -mercaptoethanol)
revealed that the solubility of WG-G gels decreased with increasing
glucose concentration, probably due to the formation of additional covalent
bonds in their network.
Description
PhD
Keywords
Industrial technology , Gluten matrix , Glucose