The gelling and gel melting temperature of κCar were measured at shear deformation by using the TA instrument TRIOS rheometer and the modified method of Derkach et al. [ 54]. Temperature scanning was performed from 20 °C to 80 °C, followed by 80 °C to 20 °C at a scan rate of 2 °C/min, an amplitude of deformation γ = 1%, and a frequency ω = 6.28 c −1. The diameter of the cone was 40 mm, the angle between the cone and plate was 1 grad, and the gap between the cone top and the plate was 0.1 mm. Aeni O. N., Aslan L. O. M., Iba W., Patadjai A. B., Rahim M., Balubi M. (2019). Effect of different seedling sources on growth and carrageenan yield of seaweed Kappaphycus alvarezii cultivated in Marobo waters, Muna regency, southeast (se) Sulawesi, Indonesia. IOP Conf. Earth Environ. Sci. 382:012015. doi: 10.1088/1755-1315/382/1/012015 [ CrossRef] [ Google Scholar] Mendoza WC, Montano NE, Ganzon-Fortes ET, Villanueva RD (2002) Chemical and gelling profile of ice-ice infected carrageenan from Kappaphycus striatum (Schmitz) Doty “sacol” strain (Solieriaceae, Gigartinales, Rhodophyta). J Appl Phycol 14:409–418 The alkali solution used in both the RC and SRC extraction procedures is intended to improve polysaccharide extraction and accelerate 6-sulfate removal from the monomer form 3,6-anhydro-D-galactose, thereby increasing gel strength and product reactivity on the protein (Corp, 1977). Apart from dissolving the carrageenans, the alkaline solution also transforms the biological precursors υ-carrageenan and μ-carrageenan into usable κ-carrageenan and ι-carrageenan, respectively. A cost comparison of SRC and RC technology reveals that the SRC extraction method is less expensive than the RC extraction process because carrageenan precipitation and solvent recovery costs are avoided in the SRC extraction process. However, when compared to the RC, the extracted primary product of the SRC process is of lower quality and is referred to as seaweed flour or alkali modified flour, with the SRC being unsuitable for human food application but designed for pet food production because of the flour is colored and often has a high bacterial population ( Rhein-Knudsen et al., 2015). On the other hand, the RC is of higher quality and is referred to as raw carrageenan ( Ortiz-Tena et al., 2017). Despite the benefits of alkali treatment, the procedure invariably results in some polysaccharide degradation due to the stresses of the processing environment (heat, alkalinity; Stanley, 1990). It is also possible that a higher concentration of sodium hydroxide will promote carrageenan depolymerization ( Varadarajan et al., 2009). Enzyme-Based Extraction Method

Terho TT, Hartiala K (1972) Method for determination of sujphate content of glycosaminoglycans. Anal Biochem 41:471–476 Gel strength was determined using the method described by Lee et al. [ 50]. In brief, 100 mL of hot κCar solution dissolved in 1.5% ( w/ v) water containing 0.2 g of KCl was poured into a Petri dish with 30 mm diameter and 21–22 mm depth and then allowed to gel at room temperature for 15 h. Gel strength was measured by the load (g/cm 2) causing a cylindrical plunger (1 cm 2 cross-section) to suddenly break the gel. The three essential steps of carrageenan extraction using the UAE method are algae pretreatment, carrageenan extraction, and carrageenan purification ( Youssouf et al., 2017). The pretreatment process was started by incubating dried seaweed ( K. alvarezii) in an 80% ethanol solution at room temperature overnight. The pre-treated seaweed was then filtered before being subjected to an ultrasound at 150W for 15min to extract the carrageenan. The movement of ultrasonic waves mediates the extraction process, which results in the transformation of ultrasonic waves into mechanical energy. This mechanical energy then ruptures the cell wall, reducing particle size as a result of the rupture and releasing the carrageenan from the cell wall ( Nigam et al., 2022). Following the extraction process, the carrageenan was available in the form of a solution, and any remaining algal residues were removed using a hot filtering process. It was necessary to place the filter at 4°C for several hours to obtain carrageenan extract in the form of a gel, and gel carrageenan was frozen and lyophilized to obtain the final carrageenan powder ( Youssouf et al., 2017). Ultrasounds allowed for the extraction of 50–55% of carrageenans from red seaweeds such as K. alvarezii and E. denticulatum in 15min, and a longer ultrasonic treatment (30min) may not result in a higher extraction yield ( Youssouf et al., 2017; Azis, 2019). Factors Affecting Carrageenan Yield and Production J. Hopkins, Carcinogenicity of carrageenan, Food Cosmet. Toxicol., 1981, 19, 779–788 CrossRef CAS PubMed. As a biodegradable polysaccharide, κCar has excellent film-forming features [ 17, 18]. However, similar to most polysaccharide-based films, plain κCar films have some limitations due to their inherent hydrophilic nature that negatively affects their mechanical and water barrier properties as compared with normal synthetic polymers [ 19]. Numerous physical and chemical techniques have been developed to obtain desirable film properties. Blending with polymers [ 20], reinforcing with nanomaterials [ 21], or layering with other polymer films [ 22] can remarkably enhance the film properties of carrageenans.One review also suggests that there may be no substantial difference between “food-grade” (undegraded) and degraded carrageenan. Degraded carrageenan is a carcinogenic (cancer-causing) version that isn’t approved. It’s even used to induce inflammation in animal studies. According to Cornucopia, test results of food-grade carrageenan carried at least 5 percent degraded carrageenan. One sample had about 25 percent. Many red algal species produce different types of carrageenans during their developmental history. For instance, the genus Gigartina produces mainly kappa carrageenans during its gametophytic stage, and lambda carrageenans during its sporophytic stage. All are soluble in hot water, but in cold water, only the lambda form (and the sodium salts of the other two) are soluble.

Several extraction methods have been implemented, with enzyme-based processing techniques being more promising and environmentally friendly than traditional extraction methods ( Tarman et al., 2020). Despite the potential for this technology to be used on an industrial scale, there has been relatively little progress in using enzymes to produce carrageenan from seaweed. Regardless, the cellulase enzyme is one of the most widely used enzymes for carrageenan extraction, as demonstrated in K. alvarezii ( Varadarajan et al., 2009). In general, the enzyme cellulase must be added to the mixture (which includes ground seaweed and distilled water) before boiling it for 1h in a water bath with a shaker at 50°C. The suspensions were then centrifuged, and the supernatants were separated and used to generate the supernatant fraction. Approximately one volume of supernatant is poured into two volumes of 2-propanol, causing the polysaccharides to precipitate as long fibers. The clear solution was removed from the samples by centrifugation (12,000rpm, 4°C, 30min), and the samples were referred to as the precipitated fraction. The samples were dried using a rotary evaporator before being freeze-dried in a freeze dryer. Because carrageenan is found in the hydrosoluble portion of the cell wall component ( Lechat et al., 1997), the seaweed’s cell wall must be shattered for the carrageenan to be released. Carrageenans can be effectively extracted using cellulases because cellulose is the primary component of seaweed cell walls ( Masarin et al., 2016). Endo-cellulases, exo-cellulases, and β-glucosidase are the three major types of cellulose enzymes, and a complete hydrolysis of cellulose microfibrils in the cell wall can be performed by combining these three types of enzymes ( Jayasekara and Ratnayake, 2019). Enzymatic hydrolysis can be performed on cellulose in most cases since it is soluble and sensitive to hydrolysis. Furthermore, the absence of lignin in seaweed allows for a faster hydrolysis process ( Tarman et al., 2020). M. L. Weiner, Parameters and pitfalls to consider in the conduct of food additive research, Carrageenan as a case study, Food Chem. Toxicol., 2016, 87, 31–44 CrossRef CAS PubMed. Research Unit, Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Kota Kinabalu, Malaysia Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy. Azis A. (2019). Optimization of temperature and time in carrageenan extraction of seaweed ( Kappaphycus alvarezii) using ultrasonic wave extraction methods. IOP Conf. Series Earth Environ. Sci. 370:012076. doi: 10.1088/1755-1315/370/1/012076 [ CrossRef] [ Google Scholar]As shown in Figure 2c, the viscosity of MC (DS = 0.032) was 39.9% lower than that of NC, and this value was conducive to the preparation of MC film-forming solution. A similar pattern regarding viscosity was observed in starch esterified by octenyl succinic anhydride [ 33]. The decreased viscosity of MC could be due to the breakage of hydrogen bonds and the weakening of intermolecular forces of carrageenan after the introduction of MAH groups. In addition, the introduced branched chains may hinder the intertwining of the molecular chains of carrageenan, resulting in the reduced viscosity of MC. Furthermore, the partial hydrolysis of carrageenan chains under alkaline esterification may also decrease the viscosity [ 34]. Asni A. (2021). Analysis on carrageenan content of seaweed Kappaphycus alvarezii at different water condition in Bantaeng District. IOP Conf. Series Earth Environ. Sci. 860:012069. doi: 10.1088/1755-1315/860/1/012069 [ CrossRef] [ Google Scholar]