Effect of transglutaminase on rheological properties and microstructure of chemically acidified sodium caseinate gels

Päivi Myllärinen, Johanna Buchert, Karin Autio (Corresponding Author)

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Abstract

The mechanical properties and microstructure of 2.7% and 4.5% sodium caseinate gels chemically acidified by glucono-δ-lactone (GDL) and cross-linked by microbial transglutaminase (TG) were studied. The acidification was performed at different temperatures. According to SDS–PAGE TG clearly caused polymerisation of caseinate irrespective of the treatment temperature (4–50 °C), The cross-linking of the proteins was more extensive at temperatures 22–50 °C.
Low amplitude viscoelastic measurements showed that 4.5% caseinate gels acidified at 50 °C were formed much faster than gels acidified at 22 °C.
TG only slightly increased the time of gelling. Control gels prepared without TG at temperatures of 4, 22, 37 and 50 °C were mechanically weak. Examination of the control gels with a confocal laser scanning microscope showed that gels formed at 37 and 50 °C were coarse and porous with large cavities between particle aggregates, whereas those formed at 22 °C were much more homogeneous.
The TG-treated and acidified sodium caseinate dispersions formed firm gels, indicating cross-linking of casein proteins. Interestingly, the strongest gels were formed at 22 and 37 °C. TG treatment improved the homogeneity of the gel structure at temperatures of 37 and 50 °C.
The hardness of TG-treated gels acidified at 4 °C increased during 1 week of storage.
Original languageEnglish
Pages (from-to)800-807
JournalInternational Dairy Journal
Volume17
Issue number7
DOIs
Publication statusPublished - 2007
MoE publication typeA1 Journal article-refereed

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Keywords

  • Sodium caseinate
  • Gels
  • Acidification
  • Transglutaminase
  • Cross-linking
  • Rheology
  • Microstructure
  • CLSM

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