Factors affecting Maillard induced gelation of protein-sugar systems

Azhar, Mat Easa (1996) Factors affecting Maillard induced gelation of protein-sugar systems. PhD thesis, University of Nottingham.

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Abstract

Gelation due to the Maillard reaction took place when solutions containing a low level of bovine serum albumin were heated in the presence of carbonyl compounds. The Maillard reaction caused a change in colour, a decrease in the pH and induced gelation. These changes were dependent on the type and concentration of sugars or protein and on the heating conditions used. Reducing sugar and Maillard reaction products (e.g. glyoxal) affected these changes, yet their order of reactivity for browning and gelation were not necessarily the same. Loss of available lysine and arginine plus changes in the thio amino acids showed that these were implicated in the reaction.

The gelation kinetics (gelation time and development of storage modulus) were followed in real time using a Bohlin CS Rheometer at a temperature of 90 °C. These studies showed that the gels did not form at a specific pH, the pH being lower for samples where the more reactive carbonyl compounds were used. Measurement of the charge on the protein after the Maillard reaction showed an increased negative charge, hence causing a lowering in the protein's isoelectric point. This had the effect of changing the critical protein concentration necessary for gelation at any pH above the isoelectric point. This reasoning would also explain the low syneresis seen in the Maillard gels. Hydrodynamic studies on dilute solution showed that the protein molecules heated in the presence of xylose associated in an orderly manner despite having a low pH. The aggregates could be described as "stiff and rod like". The linkages holding *the aggregates together were mostly attributed to additional non-disulfide linkages resulting from the Maillard reaction. Similar types of crosslinks were formed in the Maillard gels heated at 90°C and were thought to have enhanced the gel strength. Extrusion of soya grits with reducing sugars did not form a retort-stable product. However, microwave heating of the extruded product was successful in producing a product that survived a typical canning process. This suggests that formation of crosslinks may be controlled to produce novel food products.

Item Type:Thesis (PhD)
Supervisors:Hill, S.E.
Uncontrolled Keywords:gelation, Maillard reaction, carbonyl compounds, colloids
Faculties/Schools:UK Campuses > Faculty of Science > School of Biosciences
ID Code:1601
Deposited By:Ms. K EVANS
Deposited On:26 Oct 2010 11:36
Last Modified:26 Oct 2010 11:36

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