Rheological properties of a polysaccharide with highly sulfated groups extracted from Gracialaria greville

In the present study, rheological characteristics of a polysaccharide with highly sulfated groups extracted from Gracilaria greville (Gracilaria greville sulfated polysaccharide, GSPS) were investigated by steady shear and dynamic viscoelastic assays. To well understand the associations of rheological characteristics with GSPS structure, the rheological characteristics of agar were also assessed as a reference. Compared with agar, GSPS had lower viscosity, thixotropy, melting point temperature (GSPS 37 °C, agar 91 °C) and gelling point temperature (GSPS 10 °C, agar 37 °C) than agar. This might be related to the lower 3,6‐anhydro‐galactose content, but much more sulfated groups in GSPS. These results showed that GSPS could be used as a thickener in refrigerated food processing. Furthermore, the fluid type of GSPS was not altered with changes of GSPS concentration, pH value, and metal ion and sucrose concentrations; however, the viscosity of the solution system significantly decreased while thixotropy increased with pH of the GSPS solution adjusted to 3.0 from 6.0. The same results were obtained with increasing of NaCl, CaCl2, and sucrose concentrations. These findings provide a guidance for GSPS application in food processing. Practical applications Gracilaria greville is commonly known as one of the most economical marine red alga in China, and the polysaccharides extracted from G. greville are compounds simply of agar and SPS. In this manuscript, for the first time the rheological property of polysaccharide, with high sulfated groups extracted from Gracilaria greville, was reported by steady shear and dynamic viscoelastic test. To better understand the connection between rheological characteristics and construction of GSPS, the agar sold in market was also investigated. The finding will be help to fully understand the comprehensively investigated, including the difference with agar (sold in market) under different temperature and the flow behavior of GSPS under different condition.