Enzymatic modification to boost wheat gluten gelling
improves the gelling, rheological and textural properties, claim
Chinese researchers - a result that may offer value-added solutions
for a wide range of food products.
"Modification of the gluten protein provides an alternative which may be useful for maximizing the texturisation of the proteins by TGase reaction," wrote lead author Jin-Shui Wang in the journal Food Hydrocolloids.
This is not the first report on using TGase to modify the functional properties of proteins. Indeed, previous studies have looked at the effect of this enzyme on casein, soy proteins, whey proteins, myosin, and globulin. However, the new study adds significantly to these earlier ones by probing the gelling behaviour of the insoluble wheat gluten proteins, as well as the rheological and texture properties of the resulting gels.
Moreover, the research could open up for an extended use of wheat gluten proteins, a readily available and cheap inexpensive ingredient, previously lacking because of limitations with the ingredient, suggest the researchers.
"The expanded utilisation of wheat gluten proteins in food and non-food industrials has been limited by lack of some desirable functional properties, such as solubility and emulsifying properties," explained Wang.
Wang and co-workers from the South China University of Technology, the Henan University of Technology, and the Chinese Academy of Sciences, used microbial TGase (provided by Ajinomoto) to modify wheat gluten (71.5 per cent protein). TGase was used to catalyse a protein cross-linking reaction, and gels in dispersed water were prepared.
The researchers report that the minimal concentration of the modified wheat gluten needed to form a gel was 16 per cent, significantly less than the 22 per cent of the unmodified wheat gluten required. Previous studied have reported that soy protein isolates and lupin seed proteins have minimum gelation concentrations of 10 and 14 per cent.
"The gelation behavior and gel properties of the wheat gluten can be improved by TGase," they said.
Heating of the gluten prior to enzyme modification improved further the gelling properties, said Wang, reported to be due to increased surface concentrations of lysine and glutamine residues, which subsequently cross-link during TGase treatment.
Several different techniques, including texture profile analysis, centrifugation, and rheometry showed that "significant improvements of the rheological properties, water-holding capacity and texture properties of TGase-induced gels were noticed, particularly, the gels of TGase-induced glutens treated by pre-heat treatment," concluded the researchers.
Some modified wheat gluten is already available to food formulators, like, for example, Tate & Lyle's Meripro 410 and 420 launched earlier this year. The former is designed to bring functional benefits as an emulsifier and dough plasticiser, while the latter is said to have emulsifying and foaming properties well suited for desserts and confectionery.
The study was funded by the National Science Foundation of China (20276022) and the Doctorate Foundation of South China University of Technology.
Source: Food Hydrocolloids Volume 21, Issue 2 , March 2007, Pages 174-179 Gelation behavior of wheat gluten by heat treatment followed by transglutaminase cross-linking reaction Authors: J-S. Wang, M-M. Zhao, X-Q. Yang, Y-M. Jiang and C. Chun
