Influence of Gelation Temperature on the Viscoelastic Properties of Glucono -δ-lactone-induced Milk Gel

Abstract

The objective of this study was to investigate the acid-induced gelation of milk by glucono-δ-lactone (GDL). Especially, the influence of gelation temperature (3-35°C) on gelation was examined. The storage modulus (G^') and loss modulus (G^") of samples were measured using a rheological apparatus. When GDL was added to the sample solution, it was hydrolyzed to gluconic acid and the pH of the sample decreased with time. The time course of changes in G^' and that of G^" for reconstituted skim milk after addition of GDL were examined at different gelation temperatures. The G^' increased with time, after a certain latent time, and approached a maximum value (G^' max). The G^' max and the rate of gelation increased with increasing gelation temperature up to 32°C and then decreased. On the other hand, the gelation time decreased with increasing gelation temperature. A gel was formed upon acidification at temperatures below 10°C, even at 3°C. An Arrhenius plot gave a straight line at temperatures between 5°C and 23°C. The apparent activation energy was estimated to be approximately 17kcal/mol.