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Effects of molar mass on the coil to helix transition of sodium-type gellan gums in aqueous solutions

The effects of molar mass on the coil to helix transition of sodium-type gellan gums in aqueous solution with 25 mmol NaCl were studied. Six samples of well purified sodium-type gellan gums, ranging in weight average molar mass M w from 120×10 3 to 17×10 3 at 40 °C, were used for light scattering an...

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Bibliographic Details
Published in:Food hydrocolloids 2006-03, Vol.20 (2), p.378-385
Main Authors: Ogawa, Etsuyo, Takahashi, Rheo, Yajima, Hirofumi, Nishinari, Katsuyoshi
Format: Article
Language:English
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Summary:The effects of molar mass on the coil to helix transition of sodium-type gellan gums in aqueous solution with 25 mmol NaCl were studied. Six samples of well purified sodium-type gellan gums, ranging in weight average molar mass M w from 120×10 3 to 17×10 3 at 40 °C, were used for light scattering and circular dichroism measurements, viscometry, and differential scanning calorimetry. These measurements were carried out in the temperature range from 5 to 90 °C. It was found that on lowering temperature, the coil to double-helix transition for G1–G5 samples ( M w = 120 × 10 3 − 32 × 10 3 ) took place at the same temperatures, and the coil to double-helix transition is accelerated with increase of M w. The G6 sample ( M w=17×10 3) did not form a double-helix at 25 °C. It is concluded that the lowest molar mass below which no helix is formed at 25 °C in aqueous solutions with 25 mmol NaCl lies between M w=32×10 3 and M w=17×10 3.
ISSN:0268-005X
1873-7137
DOI:10.1016/j.foodhyd.2005.03.016