The Effect of Maillard Conjugation of Deamidated Wheat Proteins with Low Molecular Weight Carbohydrates on the Secondary Structure of the Protein

Abstract

A soluble isolated wheat protein fraction (sIWP) prepared from isolated wheat protein (30-35% deamidation) was incubated alone or in the presence of glucose or maltodextrins of various molecular weights (MW 1, 1.9 and 4.3 kDa) at 60°C and 75% relative humidity to promote the formation of Maillard conjugates. The formation of Maillard conjugates was confirmed by the loss of available -NH 2 groups on incubation. Approximately 3-4 carbohydrate moieties (glucose or low molecular weight carbohydrates in the commercial maltodextrin) were attached per mole of sIWP after 24 h incubation. Principal component analysis of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra measured in the dry state showed that there were no major structural changes among non-incubated sIWP, sIWP incubated alone, sIWP-glucose conjugate and sIWP-maltodextrin (MW 1 kDa) conjugate. Structural changes were observed when the protein was incubated with larger molecular weight maltodextrin (MW 1.9 kDa or 4.3 kDa). However, there were no detectable differences in their circular dichroism (CD) spectra suggesting the absence of conformational changes in proteins with or without attached carbohydrates in solution state. The differences between the FTIR and CD results are possibly due to differences in water content of the samples although pressure-induced changes to protein structure induced in the ATR cell and the influence of unreacted maltodextrins cannot be discounted. Attachment of low molecular weight carbohydrate moieties on a relatively large molecular weight protein (i.e. sIWP with average MW of 40.4 kDa) with low lysine content (average three per mole of protein) is not sufficient to have an impact on the secondary structure of the protein.

Preparation of microcapsule antioxidative wall materials of pine nut oil by the Maillard reaction

“…This transformation was further confirmed by the covalent coupling of protein and polysaccharide under dry‐heating treatment. Parallel SDS‐PAGE patterns have been reported for dry‐heated deamidated wheat proteins with glucose or MD. In the Schiff staining pattern for carbohydrates, there was a high molecular weight product containing a carbohydrate chain and Fig.…”

Covalently cross-linked proteins & polysaccharides: Formation, characterisation and potential applications

“…In the case of polysaccharides, dextran and maltodextrin have been most commonly used for preparing these conjugates [18,24,25] while other saccharides have also been investigated such as glucose, lactose and chitosan [21,26,27].…”

“…According to the literature, there are many techniques that have been used to confirm the formation of conjugates including: spectrophotometry [19,22,38], gel electrophoresis [8 , 18,39], and chromatography [20,25,27].…”