Corrigendum to “Rheological properties of agar and carrageenan from Ghanaian red seaweeds” [Food Hydrocolloids 63 (2017) 50–58]

The authors regret that the in the paper report slightly too high values for the 3,6-anhydrogalactose, which in some cases infer that the level of anhydro-galactose is higher than the level of galactose in the hydrocolloids. This is in fact not correct. The corrected data differ by only 1–3% from the ones published, but show that in no case is the anhydro-galactose level higher than the level of galactose in the hydrocolloids.

The 3,6-anhydro-galactopyranosyl moieties were initially determined by HPAEC-PAD using a CarboPac™ PA20 column following the reducing acid hydrolysis using TFA and MMB, as described by Jol et al. (1999). The procedure for the reducing acid hydrolysis includes three additions of the reducing agent MMB.

To improve the subsequent HPAEC-PAD quantification, the third addition of MMB was initially left out, as it resulted in better retention and resolution in the HPAEC-PAD quantification. The experiments have since been repeated following the exact procedure for the reducing acid hydrolysis (Jol et al., 1999).

Carbohydrate compositions have been determined using the CarboPac™ PA1 column with accompanying guard column. Elution was performed using 500 mM NaOH and an isocratic flow on 0.4 mL/min. Quantification was performed with glucose, galactose, and 3,6-anhydro-galactose as sugar standards that had been reduced by the reductive acid hydrolysis as well.

The new data are presented in the corrected Table 3 below. Reference: Jol, C. N., Neiss, T. G., Penninkhof, B., Rudolph, B., & De Ruiter, G. A. (1999). A novel high-performance anion-exchange chromatographic method for the analysis of carrageenans and agars containing 3,6-anhydrogalactose. Analytical Biochemistry, 268, 213-222.

Table 3 Overview of seaweed type (hydrocolloid source), hydrocolloid extraction method (direct water-extraction or after alkali treatment), hydrocolloid and monomer1 yields, and sulfate levels [data given as means ± SD]. Different roman superscript letters indicate significant differences (P < 0.05) column-wise for carrageenans and agar yields, monosaccharides, and sulfate content by one-way ANOVA.