Effect of pH on viscosity of oat beta-glucan

Marjatta Salmenkallio-Marttila, Tapani Suortti, Karin Autio, Kaisa Poutanen

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

Abstract

The aim of our study was to analyze aggregation behaviour of oat beta-glucan molecules by measuring pH effects on viscosity of beta-glucan solutions. Commercial oat bran concentrate (Natureal OBC native, Suomen Viljava Oy, Helsinki, Finland) was used as raw material to isolate high molecular weight beta-glucan by acid extraction (Suortti et al. 2003). HPLC-SEC was used for analysis of the molecular weight of the isolated beta-glucan (Suortti 1993). The viscosities of beta-glucan solutions at different pH were measured at shear rates 16.4 - 157 1/s (Autio et al. 1992). The extraction of oat bran at low pH gave beta-glucan solutions where no other polymeric compounds could be detected. The molecular weight of beta-glucan was similar to highest molecular weights reported thus indicating that no molecular weight reduction had occurred during the isolation procedure. The molecular weight of the peak representing beta-glucan was 1.8-1.4*106 with polydispersity ranging from 1.3-1.5 in all the samples. Lichenase hydrolysis of the acid extracted beta-glucan showed that the preparation was pure from other polysaccharides. Viscosity of beta-glucan at pH 2 was high. When the pH was adjusted to pH 6 viscosity was decreased by about 20%. When the pH was adjusted to pH 12 the viscosity of the solution was highly decreased, but adjustment of pH back to pH 6 partly restored the viscosity. However, the level was much lower than in the sample where pH was adjusted directly to pH 6 without going by pH 12. The results show that only the change of pH to highly alkaline region reduces viscosity of beta-glucan. As this phenomenon is partly reversible the conclusion is that beta-glucan is extracted as a network where beta-glucan molecules have a strong interaction with each other. Under alkaline conditions this network is dispersed because of the ionization of the hydroxyl groups. The molecular weight of beta-glucan is not affected during this change. Autio et al. 1992. Food Hydrocolloids 5: 513-522; Suortti, T. 1993. Journal of Chromatography 632: 105-110. Suortti et al. 2003. AACC Annual Meeting. Portland, OR, 28 Sept. - 1 Oct. 2003, 109.
Original languageEnglish
Title of host publicationProceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.
PublisherNatural Resources Institute Finland
Pages138
Number of pages1
ISBN (Electronic)951-729-880-3
ISBN (Print)951-729-879-X
Publication statusPublished - 2004
MoE publication typeNot Eligible

Publication series

SeriesAgrifood Research Reports
Number51
ISSN1458-5073

Fingerprint

beta-glucans
oats
viscosity
molecular weight
oat bran
licheninase
aggregation behavior
hydrocolloids
acid hydrolysis
ionization
Finland
shears
raw materials
chromatography
weight loss
polysaccharides
concentrates

Keywords

  • oat
  • beta-glucan
  • viscosity
  • molecular weight

Cite this

Salmenkallio-Marttila, M., Suortti, T., Autio, K., & Poutanen, K. (2004). Effect of pH on viscosity of oat beta-glucan. In Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004. (pp. 138). Natural Resources Institute Finland. Agrifood Research Reports, No. 51
Salmenkallio-Marttila, Marjatta ; Suortti, Tapani ; Autio, Karin ; Poutanen, Kaisa. / Effect of pH on viscosity of oat beta-glucan. Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.. Natural Resources Institute Finland, 2004. pp. 138 (Agrifood Research Reports; No. 51).
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Salmenkallio-Marttila, M, Suortti, T, Autio, K & Poutanen, K 2004, Effect of pH on viscosity of oat beta-glucan. in Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.. Natural Resources Institute Finland, Agrifood Research Reports, no. 51, pp. 138.

Effect of pH on viscosity of oat beta-glucan. / Salmenkallio-Marttila, Marjatta; Suortti, Tapani; Autio, Karin; Poutanen, Kaisa.

Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.. Natural Resources Institute Finland, 2004. p. 138 (Agrifood Research Reports; No. 51).

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

TY - CHAP

T1 - Effect of pH on viscosity of oat beta-glucan

AU - Salmenkallio-Marttila, Marjatta

AU - Suortti, Tapani

AU - Autio, Karin

AU - Poutanen, Kaisa

PY - 2004

Y1 - 2004

N2 - The aim of our study was to analyze aggregation behaviour of oat beta-glucan molecules by measuring pH effects on viscosity of beta-glucan solutions. Commercial oat bran concentrate (Natureal OBC native, Suomen Viljava Oy, Helsinki, Finland) was used as raw material to isolate high molecular weight beta-glucan by acid extraction (Suortti et al. 2003). HPLC-SEC was used for analysis of the molecular weight of the isolated beta-glucan (Suortti 1993). The viscosities of beta-glucan solutions at different pH were measured at shear rates 16.4 - 157 1/s (Autio et al. 1992). The extraction of oat bran at low pH gave beta-glucan solutions where no other polymeric compounds could be detected. The molecular weight of beta-glucan was similar to highest molecular weights reported thus indicating that no molecular weight reduction had occurred during the isolation procedure. The molecular weight of the peak representing beta-glucan was 1.8-1.4*106 with polydispersity ranging from 1.3-1.5 in all the samples. Lichenase hydrolysis of the acid extracted beta-glucan showed that the preparation was pure from other polysaccharides. Viscosity of beta-glucan at pH 2 was high. When the pH was adjusted to pH 6 viscosity was decreased by about 20%. When the pH was adjusted to pH 12 the viscosity of the solution was highly decreased, but adjustment of pH back to pH 6 partly restored the viscosity. However, the level was much lower than in the sample where pH was adjusted directly to pH 6 without going by pH 12. The results show that only the change of pH to highly alkaline region reduces viscosity of beta-glucan. As this phenomenon is partly reversible the conclusion is that beta-glucan is extracted as a network where beta-glucan molecules have a strong interaction with each other. Under alkaline conditions this network is dispersed because of the ionization of the hydroxyl groups. The molecular weight of beta-glucan is not affected during this change. Autio et al. 1992. Food Hydrocolloids 5: 513-522; Suortti, T. 1993. Journal of Chromatography 632: 105-110. Suortti et al. 2003. AACC Annual Meeting. Portland, OR, 28 Sept. - 1 Oct. 2003, 109.

AB - The aim of our study was to analyze aggregation behaviour of oat beta-glucan molecules by measuring pH effects on viscosity of beta-glucan solutions. Commercial oat bran concentrate (Natureal OBC native, Suomen Viljava Oy, Helsinki, Finland) was used as raw material to isolate high molecular weight beta-glucan by acid extraction (Suortti et al. 2003). HPLC-SEC was used for analysis of the molecular weight of the isolated beta-glucan (Suortti 1993). The viscosities of beta-glucan solutions at different pH were measured at shear rates 16.4 - 157 1/s (Autio et al. 1992). The extraction of oat bran at low pH gave beta-glucan solutions where no other polymeric compounds could be detected. The molecular weight of beta-glucan was similar to highest molecular weights reported thus indicating that no molecular weight reduction had occurred during the isolation procedure. The molecular weight of the peak representing beta-glucan was 1.8-1.4*106 with polydispersity ranging from 1.3-1.5 in all the samples. Lichenase hydrolysis of the acid extracted beta-glucan showed that the preparation was pure from other polysaccharides. Viscosity of beta-glucan at pH 2 was high. When the pH was adjusted to pH 6 viscosity was decreased by about 20%. When the pH was adjusted to pH 12 the viscosity of the solution was highly decreased, but adjustment of pH back to pH 6 partly restored the viscosity. However, the level was much lower than in the sample where pH was adjusted directly to pH 6 without going by pH 12. The results show that only the change of pH to highly alkaline region reduces viscosity of beta-glucan. As this phenomenon is partly reversible the conclusion is that beta-glucan is extracted as a network where beta-glucan molecules have a strong interaction with each other. Under alkaline conditions this network is dispersed because of the ionization of the hydroxyl groups. The molecular weight of beta-glucan is not affected during this change. Autio et al. 1992. Food Hydrocolloids 5: 513-522; Suortti, T. 1993. Journal of Chromatography 632: 105-110. Suortti et al. 2003. AACC Annual Meeting. Portland, OR, 28 Sept. - 1 Oct. 2003, 109.

KW - oat

KW - beta-glucan

KW - viscosity

KW - molecular weight

M3 - Conference abstract in proceedings

SN - 951-729-879-X

T3 - Agrifood Research Reports

SP - 138

BT - Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.

PB - Natural Resources Institute Finland

ER -

Salmenkallio-Marttila M, Suortti T, Autio K, Poutanen K. Effect of pH on viscosity of oat beta-glucan. In Proceedings of the 7th International Oat Conference. Helsinki, Finland, 2004.. Natural Resources Institute Finland. 2004. p. 138. (Agrifood Research Reports; No. 51).