Factors Affecting Texture Profile Evaluation of Agar Gels

Abstract

Effects of instrumental conditions and gel-preparative procedures on texture characteristics of agar gels were studied using force-deformation curves from an Instron Universal Testing Machine. Resolution of the variables -penetration speed, probe size, probe to gel area, Container size, concentration and dissolution time of agars, pouring, gelation and analysis temperatures, and age of gels prior to measurement, -allowed for adoption of a standardized method for texture evaluation. Inclusion of Chlorides of sodium or potassium depressed whereas calcium and magnesium enhanced the gelation capacities of agar. Regression analyses indicated no decisive correlation existed between viscosity, reflecting molecular weight, and the texture characteristics from 25 specimens of agar.

On the properties of agar gel containing ionic and non-ionic surfactants

“…The pronounced differences between the plots of Fig. 3A and B arise largely from the differences in geometries and shear stress/shear strain values employed and are in accord with the earlier observations of Whyte et al [22]. …”

Use of a prototype gel hardness tester to demonstrate the effect of variable calcium concentration of gel rigidity

“…Fig. 4a shows that, as expected, Ca concentration has little effect on agar hardness, except perhaps at the combination of the highest gel and Ca concentrations, in agreement with Whyte et al (1984). Conversely, gelrite rigidity -being dependent on divalent cation concentration for gelation (Anonymous, 1987) -shows increasing then decreasing rigidity as the Ca concentration increases (Fig.…”

“…Equivalent Ca concentrations were used for the measurements in Fig. 4, since our interest was primarily in the effects of Ca on rigidity, and Ca and Mg have similar effects on gel hardness in both gelrite (Huang et al, 1995) and agar (Whyte et al, 1984).…”

Seasonal changes in the chemical and gelling characteristics of agar from Gracilaria verrucosa collected in Turkey

“…Texture characteristics of agar gels have been studied using force deformation curves from an Instron Universal Testing Machine and the variables, such as penetration speed, probe to gel area, container size, concentration, the temperature of pouring, gelation and analysis, and age of gels have been examined (Whyte et al, 1984).…”