Distribution of hybrid beta/kappa carrageenan from the red alga Betaphycus gelatinus in Vietnam

Abstract The red alga Betaphycus gelatinus showed a monthly little variation in carrageenan yields, 3,6 anhydro galactose and sulfate contents for the native carrageenans (68.2 – 73.1%, 23.1-24.8% and 19.5 – 20.3%, respectively) and for alkali modified carrageenans (23.7 – 31.5%, 41.6 – 43.9% and 8.6 – 8.7%, respectively). The gelling, melting temperatures and gel strength of alkali modified carrageenans from April to June showed no change, with the recorded values of 40.8 o C, 74.5 o C and 310 g cm-2 , respectively. The molecular weight of the native carrageenan was primarily distributed at 876 kDa, with a small fraction at 1.2 kDa. 1 H and 13 C NMR spectra proved that the carrageenan is composed of a hybrid of beta carrageenan and kappa carrageenan. Calculated from the peak areas of the α-anomeric proton signals in 1 H NMR and the signal intensities of the anomeric carbons in 13 C NMR spectra indicated that the native carrageenan showed no much difference in components of beta carrageenan (51.8%) and kappa carrageenan (48.2%), but after alkali modified carrageenan, the beta carrageenan component increased significantly (68.6%) compared to the kappa carrageenan component (31.4%). These results will contribute more information of hybrid carrageenan from the red alga B. gelatinus in Vietnam.