Master curves obtained by time–temperature–concentration double superposition of the κ-carrageenan gelling biopolymer

Abstract

The viscoelastic behavior of food-grade biopolymers during gelation has a complex frequency spectrum that is difficult to measure by commercial rheometers. Master curves built by time–temperature superposition (TTS) of data arising from small-amplitude oscillatory flow (SAOS) or stress relaxation at a given reference temperature can provide the frequency span required to describe the frequency spectrum of highly complex systems such as hydrocolloids (e.g., κappa-carrageenan). In this work, master curves using TTS were obtained for various concentrations (1%–4% w/w). For a given concentration, mechanical spectra were generated for various temperatures (5, 10, 25, 37, and 45°C) to obtain the master curves and shifting factors (a_T, b_T) using the WLF (Williams–Landel–Ferry) equation. In this context, a methodology is suggested to obtain a wide observation window to describe complex spectra from gelling systems employed in the chemical industry.

Practical applications

The rheological methods used in this work combined the enhancement of the frequency range from experimental stress relaxation and SAOS data with double superposition. These methods are already known, but the combination to achieve an ample frequency range of more than 8 decades represents a useful tool for industrial applications of gelling systems like food hydrocolloids (i.e., κappa-carrageenan). It also helps to predict the viscoelastic behavior at temperatures and concentrations outside the usual range of rheometric measurements. It is further useful in the areas of equipment design and quality control for food products.