Effects of gel depth and gel surface area on agar gel strength

Abstract

Agar is a high priced phycocolloid extracted from red seaweeds (Rhodophyta) called agarophytes. It is a mixture of polysaccharides whose basic monomer is galactose (Armisen and Galatas 1987). Agar has many uses in the food and pharmaceutical industry, and the measure of its commercial value is based on its physical properties. One of the most important physical properties of commercial agar products is its gel strength (Chandrkrachang and Chinadit 1988). Gel strength is the force required to rupture the gel and it is measured through the use of gel testers available in the market, such as the Nikkan-sui, Rowerbal, and the Marine Colloids gel testers. Each instrument has built-in specifications for optimum use and results. Standard procedures used in the preparation of 1.5% agar gels for gel strength determination usually require 1.5 g of sample. Replication of samples in laboratory testing is however standard requirement and replication is constrained when sample extracts are scarce.

This paper discusses the effects on gel strength of different gel depths and gel surface areas. It aims to identify the minimum size of vessel and depth of gel that will give optimum results using a Marine Colloids Model GT-2 gel tester.