Immunoreactivity of wheat proteins modified by hydrolysis and polymerisation

The impact of single- and two-step enzymatic modification of wheat flour proteins was investigated on their immunoreactivity. Modification of wheat proteins was conducted using preparations of prolyl endopeptidase, transglutaminase and peptidases synthesised by Lactobacillus acidophilus 5e2 and L. sanfranciscensis DSM20663. Hydrolysis of cross-linked proteins and cross-linking of proteins’ hydrolysates was used during two-step modification. Immunoreactivity of wheat flour proteins was decreased with the increase in environmental alkalinity after treatment with transglutaminase. These modifications resulted in changes in protein composition and average polypeptide chain length. Fractional composition of gliadins demonstrated that decreasing acidity of reaction medium is associated with more effective cross-linking of ω-gliadins. Protein hydrolysis by prolyl endopeptidase and peptidases from lactobacilli also resulted in effectively degrading of HMW-glutenins and ω-gliadins. The lowest content of the immunoreactive gliadins was observed for proteins degraded with peptidases. Immunological analysis of proteins subjected to two-step enzymatic modification also showed a reduction in the content of gliadins both in the samples of cross-linked protein hydrolysates, and in cross-linked proteins. Hydrolysis of cross-linked proteins favoured more the reduction in protein immunoreactivity than cross-linking of hydrolysed proteins. Wheat proteins undergo the most effective modifications favouring the reduction in immunoreactivity, when transglutaminase/peptidase LS and peptidase LS/transglutaminase combinations were used. Proposed methods of enzymatic reduction in gluten immunoreactivity could be used as additional step of flour modification in sourdough technology.