Gel properties of agar from two Gracilaria species in Sri Lanka and development of food jellies

Gracilaria species are found to be a rich source of natural hydrocolloid agar-agar but are currently under-exploited in Sri Lanka. The gel characteristics of agar extracted from Gracilaria corticata and Gracilaria edulis from Sri Lankan waters were investigated in this study. The agar yields (%, dry weight basis) obtained from G. corticata and G. edulis by hot-water extraction at 90℃ for 1 h, were 39.91 ± 0.17 and 67.52 ± 1.43, respectively. The gel properties of both agar gels (1.5%, w/v) such as pH, viscosity, gelling and melting temperatures, and syneresis were examined. The viscosity of agar gels (cP) at 80°C was lower than that at 70°C for both species, while G. edulis has shown higher viscosities at both temperatures (1.96 ± 0.06 and 2.76 ± 0.39, respectively). Moreover, the textural analysis revealed that G. corticata has a higher gel hardness (316.7 ± 20.8 g) than G. edulis (113.33 ± 12.58 g). Strawberry-flavored food jellies were developed from agar gels of two Gracilaria species with either artificial (Carmoisine, E122) or natural food color (Annato). Collectively, this study revealed that agar from both red seaweed species has the potential to be developed as plant-based food jellies, and G. edulis can be suggested as the best source to extract agar with higher yield compared to G. corticata.