Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2010
Publication Date: 6/17/2010
Citation: Smith, B.M., Bean, S., Schober, T.J., Tilley, M., Herald, T.J., Aramouni, F. 2010. Composition and Molecular Weight Distribution of Carob Germ Proteins Fractions. Journal of Agricultural and Food Chemistry. 58:7794-7800. Interpretive Summary: Gluten free breads typically suffer from poor quality and are typically produced from cake batter like systems rather from dough. This causes problems both in food quality and in food processing. Intense research has been focused on finding and developing non-wheat proteins that are capable of forming a dough. This research measured the molecular weight of carob germ proteins which are known to have dough like properties. The molecular weight of carob germ proteins were found to be lower than of gluten, which is one reason why the carob germ proteins do not produce a dough as strong as gluten. Differences in other properties such as solubility were also found, which may contribute to the weakness of carob germ protein dough. This research provides insight into the properties of proteins needed to form dough and provides further insight into possible ways to modify proteins from other sources, including corn and sorghum, to form dough. Dough formation in non-wheat proteins will improve the quality of wheat-free foods and also will provide information to better understand the functionality of wheat gluten proteins.
Technical Abstract: Biochemical properties of carob germ proteins were analyzed using a combination of selective extraction, reversed-phase high performance liquid chromatography (RP-HPLC), size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALS) and electrophoretic analysis. Using a modified Osborne extraction procedure, carob germ flour proteins were found to contain ~32% albumin and globulin and ~68% glutelin with no prolamins detected. The albumin and globulin fraction was found to contain low amounts of disulfide bonded polymers with relatively low Mw ranging up to 5x106 Da. The glutelin fraction however, was found to contain large amounts of high molecular weight disulfide bonded polymers with Mw up to 8x107 Da. When extracted under non-reducing conditions and divided into soluble and insoluble proteins as typically done for wheat gluten, carob germ proteins were found to be almost entirely (~95%) in the soluble fraction with only (~5%) in the insoluble fraction. As in wheat, SEC-MALS analysis showed that the insoluble proteins had a greater Mw than the soluble proteins and ranged up to 8x107 Da. The lower Mw distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour.