Dynamic rheological behavior of meat proteins during acid-induced gelation

Glucono-delta -lactone (gdl) is used to promoting gelification of muscle pr oteins in restructured foods. Protein gelification can be achieved by lower ing enough the pH to promote interactions between protein molecules. The gd l was added to a muscle extract (1.2 % w/w) at 4, 12, 20 and 28 degreesC an d pH and rheological behavior were observed using a controlled stress rheom eter. Changes in pH induced by gdl hydrolysis were more noticeable at 28 de greesC (final pH 4.40) than at 4 degreesC (final pH 5.02). The gdl hydrolys is rate depends on temperature, being lower at low temperature and increasi ng with temperature. This temperature influence on pH decrease was reflecte d on muscle protein gels viscoelastic behavior, where the proteins cross-li nking were caused by the acidification, enough to form a gel structure. Max imum storage (G') and loss (G") modules were achieved at pH values between 4.5-5.5, near to myofrbrillar proteins isoelectric point. Samples presented a liquid-like behavior (G'>G") during the acid-induced gelation. Stronger gels were formed at high temperatures. At this point, loss of solubility an d structure were caused by an excess of acid in the medium.