TY - JOUR
T1 - Transglutaminase treatment of brown rice flour
T2 - A chromatographic, electrophoretic and spectroscopic study of protein modifications
AU - Renzetti, Stefano
AU - Behr, Juergen
AU - Vogel, Rudi F.
AU - Barbiroli, Alberto
AU - Iametti, Stefania
AU - Bonomi, Francesco
AU - Arendt, Elke K.
PY - 2012/4/15
Y1 - 2012/4/15
N2 - 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.
AB - 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.
KW - Brown rice
KW - Dynamic light scattering
KW - Front face fluorescence
KW - Protein
KW - SE-HPLC
KW - Transglutaminase
KW - Two dimensional gel electrophoresis
UR - https://www.scopus.com/pages/publications/81855164780
U2 - 10.1016/j.foodchem.2011.08.029
DO - 10.1016/j.foodchem.2011.08.029
M3 - Article
AN - SCOPUS:81855164780
SN - 0308-8146
VL - 131
SP - 1076
EP - 1085
JO - Food Chemistry
JF - Food Chemistry
IS - 4
ER -