Strain and strain rate dependence of gellan, agar and agar–gellan gels as model systems.

Shipra, Sharma and Suvendu, Bhattacharya (2014) Strain and strain rate dependence of gellan, agar and agar–gellan gels as model systems. Journal of Food Engineering, 141. pp. 93-98.

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Abstract

Gellan, agar and their combination gels (1:1, 2 g/100 g) as model systems were subjected to strains up to 0.8 while varying the crosshead speed between 0.01 and 10 mm s�1 to determine different textural characteristics (Young’s modulus, rigidity constant, degree of concavity and apparent biaxial elongational viscosity, gbe) and fracture characteristics. The compression curves usually consisted of 6 zones, and the gels were sensitive to strain rate and the extent of applied strain. Agar gel showed higher fracture force and energy compared to gellan and agar–gellan samples. However, the fracture strain for gellan was highest (44.6–70.7%) followed by agar (22.8–40.3%) and agar–gellan (24.3–37.3%) gels indicating more brittleness in agar/agar–gellan gels but toughness in gellan samples. The degree of concavity of gellan gel was less than 1 indicating strain-softening characteristics; the agar gel exhibited strain-hardening phenomenon as it was more than 1. However, marginal strain-softening behaviour was observed for gellan–agar combination gel (0.856 6 n 6 0.999). A power law type model linked gbe and the biaxial extensional rate at fracture. Gellan gels are suitable to prepare chewable fabricated juicy gels, while brittle products resulted from agar/agar–gellan. It is proposed that gbe at fracture is a good index for characterising gels in relation to product development and compression-spreading.

Item Type:	Article
Uncontrolled Keywords:	Rheology, Gel, Compression, Stress Strain, Strain rate
Subjects:	600 Technology > 08 Food technology > 07 Food Engineering
Divisions:	Food Engineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	08 Jul 2014 06:39
Last Modified:	08 Jul 2014 06:39
URI:	http://ir.cftri.res.in/id/eprint/11615

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