Rotational Thromboelastometry for Characterising Acid-Induced Gelation of Cross-Linked Casein

Abstract

Rotational thromboelastometry (ROTEM), a method for the clinical characterisation of blood clot formation and fibrinolysis, has been applied to study the acid-induced gelation of cross-linked casein. The results were compared to those from small amplitude oscillatory shear (SAOS) experiments that were carried out on the same samples: acid casein in phosphate buffer and reconstituted skim milk were treated with microbial transglutaminase to achieve cross-linking of casein and to obtain gels with a broad range of stiffness upon acidification with glucono-δ-lactone. Gelation onset was detected consistently 2 min later by ROTEM compared to SAOS, which my be attributed to the differences in the onset criteria of both methods. Comparison of maximum clot firmness (ROTEM) and maximum storage modulus (rheometry) as indicators for gel stiffness revealed a strong non-linear relationship, that was successfully fitted to the common model of ROTEM clot elasticity through adding a proportionality coefficient. From the results of this study it can be concluded that ROTEM might serve as a useful tool for characterising the acid-induced gelation of proteins that are available in only small quantities.