Aeration of model gels: Rheological characteristics of gellan and agar gels

Model food sols containing gellan and agar at different solid concentrations were aerated. The rheological characteristics of the setted gels were determined. These were the compression characteristics (fracture strain/stress/energy, firmness and the total energy for compression) and the stress relaxation characteristics (extent of relaxation and relaxation time). Fracture strain of gels increased due to aeration indicating that the aerated samples exhibited a delayed fracture due to the presence of incorporated air. The extent of increase in fracture strain for aerated agar gels over the corresponding non-aerated samples is 1.7–23.1% while it is 4.3–15.1% for gellan gels. The extent of relaxation increased due to aeration while relaxation time (λ) decreased. Relaxation time for aerated agar and gellan gels is 9.6–40.7% and 19.6–37.6% lower than the non-aerated samples. At a low concentration of hydrocolloid, the effect of aeration was usually non-significant (at p ⩽ 0.05) while prominent changes in rheological behaviour occurred at a high concentration. Aeration of food gels offered the possibility of rheological modifications to suit the consumer requirements in developing specialty fabricated gels.