Transglutaminase treatment of brown rice flour: A chromatographic, electrophoretic and spectroscopic study of protein modifications

Stefano Renzetti, Juergen Behr, Rudi F. Vogel, Alberto Barbiroli, Stefania Iametti, Francesco Bonomi, Elke K. Arendt

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Recently, it was shown that transglutaminase (TGase) treatment of brown rice (BR) flour results in textural improvements of gluten-free bread. In this study, changes in the protein profiles of BR flour and protein fractions induced by TGase treatment were investigated to better understand the activity and specificity of the enzyme. Size-exclusion HPLC (SE-HPLC) profiles of flour extracts, under reducing conditions, revealed the presence of macromolecular protein complexes, as well as low molecular weight proteins. After TGase treatments (10 U/g of proteins) a general reduction in peak intensities indicated the polymerisation of BR proteins into larger, insoluble complexes. Microchip capillary electrophoresis and two-dimensional (2D) gel electrophoresis revealed that the α and β glutelin subunits were primary substrates for the polymerisation reaction, whereas albumins and globulins were only slightly affected. SE-HPLC of the protein fractions revealed glutelins' polymerisation into high molecular weight structures after TGase treatment. Dynamic light scattering measurements showed that new supramolecular aggregates of glutelins co-existed with the macromolecular complexes already present in the untreated fraction. Front-face fluorescence approaches indicated that TGase treatment caused a decrease in protein surface hydrophobicity of BR flour, but not of the glutelin suspensions. It is concluded that the large protein complexes resulting from glutelin polymerisation and the stronger hydrophobic interactions among proteins result in the improved textural properties of TGase-treated BR bread.

Original languageEnglish
Pages (from-to)1076-1085
Number of pages10
JournalFood Chemistry
Volume131
Issue number4
DOIs
StatePublished - 15 Apr 2012
Externally publishedYes

Keywords

  • Brown rice
  • Dynamic light scattering
  • Front face fluorescence
  • Protein
  • SE-HPLC
  • Transglutaminase
  • Two dimensional gel electrophoresis

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