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.

Renewable feedstock from perennial industrial crops, including those cultivated on marginal land in a short-rotation coppice system, could be an important contribution to the bioeconomy. The majority of data available on the topic are limited to the production of bioenergy from this type of biomass. According to the concept of bioeconomy, biomass-based bioproducts have priority over energy production. This paper characterizes the chemical composition and antioxidant activity of extracts from bark (b), wood (w) or a mixture of bark and wood (b + w) from Salix purpurea, Salix viminalis and Populus nigra obtained using supercritical carbon dioxide (scCO₂), scCO₂ and water (1%, w/w) or only water. Generally, a high concentration of polyphenols was obtained after extraction with scCO₂ and water, while the lowest concentration was found in extracts obtained with scCO₂. The highest concentration of polyphenols (p < 0.05) was obtained in an extract from P. nigra (b) (502.62 ± 9.86 mg GAE/g dry matter (d.m.)) after extraction with scCO₂ and water, whereas the lowest polyphenol concentration was observed in an scCO₂ extract from S. purpurea (b) (6.02 ± 0.13 mg GAE/g d.m.). The flavonoids were effectively separated by extraction with scCO₂ (0.88–18.37 mg QE/g d.m.). A positive linear relationship between the antioxidant activity determined by DPPH and ABTS assays and the concentration of polyphenols was demonstrated, R² = 0.8377 and R² = 0.9568, respectively. It is most probable that the concentration of flavonoids, rather than the concentration of polyphenols, determines the chelating activity of Fe²⁺. The Fe²⁺-chelating activity of scCO₂ extracts ranged from 75.11% (EC₅₀ = 5.41 mg/cm³, S. purpurea, b + w) to 99.43% (EC₅₀ = 0.85 mg/cm³, P. nigra, b + w). The lowest chelating activity was demonstrated by the extracts obtained with scCO₂ and water (maximum 26.36%, S. purpurea, b + w). In extracts obtained with scCO₂ and water, p-hydroxybenzoic acid (210–428 µg/g), p-coumaric acid (56–281 µg/g), saligenin (142–300 µg/g) and salicortin (16–164 µg/g) were the dominant polyphenols. All of these chemical compounds occurred mainly in the free form. The S. purpurea, S. viminalis and P. nigra biomass proved to be an attractive source of biologically active compounds for various possible applications in food, drugs or cosmetics. These compounds could be extracted using an environmentally friendly method with scCO₂ and water as a co-solvent.

Wheat storage proteins and products of their hydrolysis may cause coeliac sprue in genetically predisposed individuals with high expression of main histocompatibility complex HLA-DQ2 or DQ8, since by consuming wheat, they become exposed to proline- (P) and glutamine (Q)-rich gluten. In bread-making, the hydrolysis of gliadins and coeliac-toxic peptides occurs with varied efficiency depending on the fermentation pH and temperature. Degradation of gliadins catalysed by Lactobacillus acidophilus 5e2 peptidases and a commercial prolyl endopeptidase synthesised by A. niger, carried out at pH 4.0 and 37 °C, reduces the gliadin concentration over 110-fold and decreases the relative immunoreactivity of the hydrolysate to 0.9% of its initial value. Hydrolysis of coeliac-toxic peptides: LGQQQPFPPQQPY (P1) and PQPQLPYPQPQLP (P2) under the same conditions occurs with the highest efficiency, reaching 99.8 ± 0.0% and 97.5 ± 0.1%, respectively. The relative immunoreactivity of peptides P1 and P2 was 0.8 ± 0.0% and 3.2 ± 0.0%, respectively. A mixture of peptidases from L. acidophilus 5e2 and A. niger may be used in wheat sourdough fermentation to reduce the time needed for degradation of proteins and products of their hydrolysis.