Noncovalent Cross-Linking of Casein by Epigallocatechin Gallate Characterized by Single Molecule Force Microscopy

• Published in: Journal of agricultural and food chemistry 2006-06, Vol.54 (12), p.4077-4081
• Main Authors: Jöbstl, Elisabeth, Howse, Jonathan R, Fairclough, J. Patrick A, Williamson, Mike P
• Format: Article
• Language: English
• Subjects: analytical methods; beta-casein; Biological and medical sciences; Caseins - chemistry; Catechin - analogs & derivatives; Catechin - chemistry; Chemical Phenomena; Chemistry, Physical; Cross-Linking Reagents; crosslinking; epigallocatechin; epigallocatechin gallate; Food industries; Fundamental and applied biological sciences. Psychology; green tea; Hydrophobic and Hydrophilic Interactions; Microscopy - methods; Milk and cheese industries. Ice creams; Models, Molecular; Phosphorylation; polyphenols; single molecule force microscopy; Thermodynamics
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf053259f

Interaction of the tea polyphenol epigallocatechin gallate (EGCG) with β-casein in milk affects the taste of tea and also affects the stability of the tea and the antioxidant ability of the EGCG. In addition, interaction of polyphenols with the chemically similar salivary proline-rich proteins is largely responsible for the astringency of tea and red wine. With the use of single molecule force microscopy, we demonstrate that the interaction of EGCG with a single casein molecule is multivalent and leads to reduction in the persistence length of casein as calculated using the wormlike chain model and a reduction in its radius of gyration. The extra force required to stretch casein in the presence of EGCG is largely entropic, suggesting that multivalent hydrophobic interactions cause a compaction of the casein micelle. Keywords: Epigallocatechin gallate; polyphenol; casein; single molecule force microscopy; astringency; compaction