Determination of critical gel-sol transition point of Highly Concentrated Micellar Casein Concentrate using multiple waveform rheological technique

Abstract

The purpose of this study was to determine critical gel-sol transition point of Highly Concentrated Micellar Casein Concentrate (HC-MCC) during heating of cold gel. We applied Winter–Chambon criterion (tan δ becomes independent of frequency) on multiwave oscillatory rheological data as a robust alternative to a conventional rheological method which typically treats crossover of storage modulus (G’) and loss modulus (G”) as a gel-sol transition point. We found that the conventional method indicates a pseudo-gel sol transition point which is frequency dependent and does not represent true physical state of the material. Gel-sol transition temperature obtained with multiple waveform rheological method (11.1 °C) was significantly (P < 0.05) different as compared to the conventional method (21–27 °C). While using the convergent point of tan δ (indicating its frequency dependence) from different frequencies obtained from standard temperature sweep and extracted from multiwave test showed about the same gel-sol transition point (11.1 °C). The low frequency dependence of the sample at 5 (n = 0.06) and 11.1 °C (n = 0.07) also confirmed the sample is a strong gel at these temperatures, while the high frequency dependence at 25 °C (n = 0.7) demonstrated a viscoelastic liquid behavior. These findings demonstrated that employing Winter–Chambon criterion can be an effective way for determining of true gel-sol transition point of HC-MCC, and multiwave oscillation was a quick measurement for analyzing the sample. This study would also draw the attention of researchers to avoid the wrong practice of determining temperature-induced phase transition without considering the frequency dependence.