Composition and Molecular Weight Distribution of Carob Germ Protein Fractions

• Published in: Journal of agricultural and food chemistry Vol. 58; no. 13; pp. 7794 - 7800
• Main Authors: Smith, Brennan M, Bean, Scott R, Schober, Tilman J, Tilley, Michael, Herald, Thomas J, Aramouni, Fadi
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.07.2010
• Subjects: Biological and medical sciences; Cereal and baking product industries; Chemical Composition of Foods/Feeds; Fabaceae - chemistry; Food industries; Fundamental and applied biological sciences. Psychology; Galactans - chemistry; Mannans - chemistry; Molecular Weight; Plant Gums - chemistry; Plant Proteins - chemistry; Plant Proteins - isolation & purification; gluten; caroubin; protein; Carob germ flour; celiac disease; light scattering; gluten-free; Immunopathology; Molecular weight distribution; Light scattering; Flour; Coeliac disease; Intestinal malabsorption; Plant protein; Digestive diseases; Intestinal disease; Carob; Chemical composition; Gluten
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf101523p

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 (SEC) coupled with multiangle 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 M w ranging up to 5 × 106 Da. The glutelin fraction, however, was found to contain large amounts of high molecular weight disulfide-bonded polymers with M w up to 8 × 107 Da. When extracted under nonreducing 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 M w than the soluble proteins and ranged up to 8 × 107 Da. The lower M w distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour.