Viscoelastic Behavior of Whey Protein Isolates at the Sol‐Gel Transition Point

Abstract

The flow behavior of whey protein isolates (WPI) was studied in systems processed under different conditions. Experiments were undertaken to study effects of heating conditions (temperature/time), pH, solid content, calcium chloride, and guanidinium hydrochloride addition on the gelation of whey protein isolate solutions. The rheological data demonstrated a power-law frequency dependence of the viscoelastic functions G'() and G"() and a frequency-independent tan ␦ determined from a multifrequency scan of tan ␦ vs gelling time at the gel point. The power-law exponents (n) obtained from these dynamic measurements for determining the sol-gel transition point were between 0.62 and 0.69. Those values suggest a percolation mechanism for the gelation process.

Effect of acid hydrolysis on rheological and thermal characteristics of lentil starch slurry

“…The gelatinization process can be quantified rheologically only if small deformations are used in the lower frequency range (0.1e1 Hz) (Lapacin & Pricl, 1995, 373e393) and further it is recommended to study gelation kinetics at milder condition or slower rate of heating (Labropoulos & Hsu, 1996). The technique has earlier been experimented with rice starch gelatinization (Ahmed et al, 2008).…”

Rheological Studies on Gelling Behavior of Soy Protein Isolates

“…We were able to define the gel point and the fractal dimension of WPI solutions (Labropoulos and Hsu, 1996). Unlike WPI which is soluble in water, soy protein isolates (SPI) cannot be completely dissolved.…”

Mechanical characterization of network formation during heat-induced gelation of whey protein dispersions

“…Labropoulos and Hsu 46 have examined changes in viscoelastic properties of WPI during gelation in relation to the Winter-Chambon gelation criterion and have concluded that the gelation processes of WPI were explained in the framework of the percolation theory. For some reasons, however, their exploration was limited to cold-set gelation, gelation caused by an addition of a denaturant, and gelation at an extremely high protein concentration (35% w/v) at a relatively low temperature (40°C).…”

“…10 -12 Similar exponent values (n ϭ 0.62-0.69) have been obtained for WPI gelation under various conditions examined by Labropoulos and Hsu. 46 The question is why only WPI dispersed in distilled water exhibited a percolation-type sol-to-gel transition during heat-induced gelation in this study. Obviously, the formation of particulate gels in the presence of a sufficient amount of ions is far from chemically crosslinking polymer systems.…”