Molecular weight distribution of carrageenans studied by a combined gel permeation/inductively coupled plasma (GPC/ICP) method

Abstract

Degraded carrageenan (known as poligeenan molecular weight: 20 kDa to 30 kDa) causes ulcerative colitis in experimental animals. In this paper, the molecular weight distributions of 29 samples of food-grade refined carrageenans were studied by high performance liquid gel permeation chromatography (GPC) directly connected to vacuum-ultraviolet inductively coupled plasma-atomic emission spectrometry (ICP) (GPC/ICP) as well as GPC/refractive index (RI) detection. All samples of food-grade carrageenan had a major broad peak of high molecular weight which eluted at around 6.5 min in both RI and ICP mode (sulphur and carbon), and each sample of them had no obvious peak of poligeenan (the detection limit was about 5%). The number average molecular weights of these carrageenans ranged from 193 kDa to 324 kDa, and the weight average molecular weights ranged from 453 kDa to 652 kDa based on RI data. Some samples had a few minor peaks which eluted around 10-12 min. These peaks came from ionic sulphate, sucrose or glucose. It was considered that if the data-sampling programme was improved, the GPC/ICP system would become a more powerful technique for evaluation of carrageenan samples containing ionic substances and sugar.

Growth and carrageenan quality of Kappaphycus striatum var. sacol grown at different stocking densities, duration of culture and depth

“…Commercially, the average molecular weight of carrageenan ranges from 193 to 324 kDa and is presumed completely degraded if the average molecular weight is below 0.7 kDa (Uno et al 2001). The present study obtained a range of carrageenan with a molecular weight from 707 to 1,200 kDa.…”

Carrageenans: Biological properties, chemical modifications and structural analysis – A review

“…They comprise refractive index (RI) (Ekeberg, Knutsen, & Sletmoen, 2001;Ekström & Kuivinen, 1983;Karlsson & Singhb, 1999;Knutsen, Moe, Larsen, & Grasdalen, 1993;Knutsen et al, 2001;Montolalu, Tashiro, Matsukawa, & Ogawa, 2007;Spichtig & Austin, 2008;Sworn et al, 1987), low-angle laser light scattering (LALLS) (Hjerde et al, 1999), multi-angle light scattering (MALS) (Girod, Baldet-Dupy, Maillols, & Devoisselle, 2001) and vacuumultraviolet inductively coupled plasma-atomic emission spectrometry (ICP) (Uno et al 2001). Triple detector system (RI-viscometerlight scattering) (Myslabodski, Stancioffh, & Heckertta, 1996) and dual detector systems: RI and LALLS (Slootmaekers et al, 1991), RI and light scattering (Singh & Jacobsson, 1994;Viebke, Borgström, & Piculell, 1995), RI and MALS (Marcelo, Saiz, & Tarazona, 2005) have also been described.…”

“…One of the main focuses of SEC method for carrageenans analysis are related to the study of products degradation, either highlighting the potential health risks associated with the consumption of low molecular weight (LMW) carrageenans (Uno et al, 2001) or to the impact on their functionality as gel-forming or viscosity-enhancing polymers in foods (Karlsson & Singhb, 1999). Spichtig and Austin (2008) used high performance SEC for the measurement of LMW carrageenans in food ingredients and Table 2 Chemical shifts (ppm) assignment in the 1 H NMR spectra of kappa-, iota-and lambdacarrageenans obtained at 80°C.…”

Determination of the low molecular weight fraction of food-grade carrageenans

“…In fact the debate revolves around degraded carrageenan (or poligeenan, as it has been named) which has a weight average molecular weight (Mw) of 10,000-30,000 [3,9,11] and has been shown to cause ulcerative colitis at high doses in experimental animals [12]. One camp argues that the presence of carrageenan in food may lead to health problems due to the presence of poligeenan [3].…”

“…This is most frequently performed by size exclusion chromatography (SEC) [14][15][16][17][18][19][20][21], but other techniques such as field flow fractionation (FFF) have also been applied [22]. Molecular weight can be determined by use of suitable detectors such as light scattering at low angle (LALS), right angle (RALS) or multiple angle (MALS) [15,16,[18][19][20] and/or viscometry [21], or by calibration of the separation system with well-characterised standards [11,14]. Sedimentation analysis, osmometry and even gel breaking strength have also been applied to determine average molecular weights [15,23].…”