Characteristics of Semi-Refined Carrageenan From Kappaphycus Seaweed Farmed in Coastal Waters of Northern Java, Indonesia

Kappaphycus seaweed is the primary source of carrageenan, a polysaccharide widely utilised as a thickening and gelling agent in many commercial products. Unlike pure refined carrageenans, semi-refined carrageenans (SRC) are considered more cost-efficient and easier to produce. This study evaluates the quality of SRC extracted from Kappaphycus alvarezii (Doty) Doty ex Silva 1996, and Kappaphycus striatus (F. Schmitz) Doty ex P.C. Silva 1996, seaweeds farmed in the northern part of Java Island, particularly in Serang, Seribu Islands, and Karimunjawa Islands. Using 8 % KOH as a solvent, SRC was extracted from clean dried seaweed. Physical and chemical characteristics of the SRC were measured by assessing the percentage SRC yield, ash content, moisture, sulphate content, viscosity (cp) and gel strength (g.cm-2). Pearson’s correlation analysis was performed to investigate the relationship between SRC quality and environmental factors. Fourier transform infrared spectroscopy (FTIR) analysis showed that all samples had kappa-carrageenan from peak absorbance of 1218–1224 cm-1 indicating ester sulphate bonds, 924–925 cm-1 indicating 3,6–anhydrogalactose, and 843–844 cm-1 suggesting galactose–4–sulphate groups. Furthermore, ash content, moisture, and viscosity of SRC passed the FAO standard, while the sulphate content was below the threshold limit. Several environmental factors had a significant correlation with SRC quality, such as water pH positively correlated with gel strength, salinity level positively correlated with gel strength, and depth positively correlated with ash content. This study concluded that SRC produced from the sampling sites had varying qualities and may be affected by environmental parameters in their cultivation site.