Eco-Friendly Extraction, Structure, and Gel Properties of ι-Carrageenan Extracted Using Ca(OH)2

An eco-friendly method for iota-carrageenan extraction from seaweed Eucheuma denticulatum through boiling and using a low concentration of Ca(OH)(2) is reported. Compared to the traditional method of iota-carrageenan extraction using NaOH, the reported method using Ca(OH)(2) had the advantages of using 93.3% less alkali and 86.8% less water, having a 25.0% shorter total extraction time, a 17.6% higher yield, and a 43.3% higher gel strength of the product. In addition, we evaluated the gel properties and structures of iota-carrageenan products extracted by Ca(OH)(2) (Ca-IC) and NaOH (Na-IC). The Fourier transform infrared spectroscopy results showed that the structures of Ca-IC and Na-IC did not change remarkably. The results of the thermogravimetric analysis and differential scanning calorimetry showed that Ca-IC had the same thermal stability as Na-IC. The results of the textural analysis showed that Ca-IC had a higher hardness and better chewiness compared to Na-IC. Rheological results indicated that Ca-IC and Na-IC exhibited shear-thinning and non-Newtonian fluid properties, whereas the viscosity of Ca-IC was less than that of Na-IC. In conclusion, this new method of iota-carrageenan extraction using Ca-IC is markedly better and yields higher quality carrageenan than the conventional method of using Na-IC.

Automated summary

An eco-friendly method for extracting iota-carrageenan from seaweed was developed using boiling and a low concentration of Ca(OH)(2). Compared to the traditional method using NaOH, this method resulted in a higher yield and gel strength, shorter extraction time, and reduced alkali and water usage. The extracted iota-carrageenan showed similar structures and thermal stability, but different textural and rheological properties compared to NaOH-extracted carrageenan.