A Simple Method for Measuring Agar Gel Strength

Seaweeds are the only source for phycocolloids. Commercial applications of phycocolloids depend on their chemical/physical properties, including their gel forming ability. Thus, gel strength values are important for seaweed growers and scientists. Gel strength measurements include the use of texture analyzers or rheometers, which are not always available for seaweed growers and scientists. Here, we describe a home-made apparatus for assessing gel strength through the weight of a water column required for breaking a gel surface. The system worked well at gel concentrations between 0.5 and 1.5%, giving values of 82–535 g cm⁻² and 163–754 g cm⁻² for agar and agarose gels, respectively. The lowest variations were obtained for gel sample volumes between 25 and 30 mL. The system was manually operated but no significant variations were observed between measurements conducted by the five different users. The readings were independent of the water column fill rate. The variations in gel strength values were similar to reports using other gel strength measuring devices. We propose the use of our apparatus as a flexible, affordable tool for the assessment of gel quality, which is suitable for research groups or seaweed farmers without access to expensive equipment, and with a need to quickly assess their seaweed of interest at a relevant time scale for cultivation or harvest.