Polymer and Ion Concentration Effects on Gellan Gel Strength and Strain

Abstract

Failure stresses and strains were measured in compressive, tensile and torsional modes on gellan gels at four polymer (O&1.8% w/v) and seven Ca++ (1.5-60 mM) concentrations. Shear stresses at failure were equal in all three testing modes and proportional to gellan content. Low calcium gels increased linearly in strength with Ca+ + concentration until it reached a level of about 0.5 calcium ions per repeat tetrasaccharide unit of gellan gum polymer. Gel strength decreased linearly with Ca+ + at higher concentrations. Low calcium gels were extensible with failure strains decreasing as the logarithm of Ca+ +; whereas high calcium gels were brittle and failed at a constant strain, the value of which was twice as high in compression and torsion as in tension.

Comparative Studies on Fracture Characteristics of Food Gels Subjected to Uniaxial Compression and Torsion

“…This is probably because twisted specimens normally fractured in tension. It is known that uniaxial tension often results in a smaller fracture strain value than uniaxial compression and torsion, presumably due to rapid decrease in the cross-sectional radius of the specimen (Hamann, 1983;Tang et al , 1994). Since true shear stress development patterns in uniaxial compression and torsion were comparable in most cases in this study, a smaller fracture stress in torsion appears to be a consequence 5.…”

“…In previous studies on torsion fracture tests in the literature (Diehl et al, 1979;Hamann, 1983;Montejano et al, 1985;Lelievre et al, 1992;Tang et al, 1994Tang et al, , 1997 Daubert, 2000Daubert, , 2001Ikeda, 2001Ikeda, , 2003, a specimen was frequently carved or molded into a capstan shape. In this study, cylindrical gels were examined with the intention of facilitating mathematical treatments and minimizing uncertainties accompanying sample preparation.…”

Dairy Systems

“…This results in similar increase or decrease of fracture stress and fracture strain with varying variables such as concentration. It has been found that fracture strain from tension is lower than compression and torsion (Tang et al, 1994;Hamann et al, 2006). Stress increases more rapidly in tension, causing the material to fail at small strain.…”

Low acyl gellan gum fluid gel formation and their subsequent response with acid to impact on satiety

“…Polysaccharides are widely used as replacements for fats and sugars in low fat and reduced calorie foods or within enhanced satiety products (Brown, Cutler, & Norton, 1996;Garrec, FraschMelnik, Henry, Spyropoulos, & Norton, 2012;Norton, Frith, & Ablett, 2006;Tang, Lelievre, Tung, & Zeng, 1994). The use of hydrocolloids only as simple gelling and thickening agents does not offer any specific benefit to health, convenience or quality in a formulated product (Gabriele, Spyropoulos, & Norton, 2009).…”