Millet bran dietary fibres treated by heating, dual enzymolysis united with acrylic-grafting or hydroxypropylation: effects on the properties of heat-induced egg white protein gel

Introduction: Millet bran is an abundant dietary fibre resource, but it is rarely used in Foods. Methods: To enhance the functional properties and applications of foxtail millet bran dietary fibre (MBDF), MBDF modified by heating, cellulase and xylanase hydrolysis combined with acrylic-grafting (MBDF-HDEAG) or hydroxypropylation (MBDF-HDEH) were prepared, and the effects of these modified MBDFs on heat-induced egg white protein gel (H-EWPG) were studies. Results and discussion: The results showed that heating and enzymolysis united with acrylic-grafting or hydroxypropylation both enhanced the surface area, soluble fibre content, water-retention and expansion abilities of MBDF. The addition of unmodified MBDF, MBDF-HDEAG and MBDF-HDEH increased the beta-sheet content of H-EWPG and made its microstructure denser and granular. Compared with MBDF, MBDF-HDEAG and MBDF-HDEH more effectively improved the gel and texture properties of H-EWPG including water-holding ability (from 20.45 to 34.63 g/100 g), pH (from 4.53 to 7.66), hardness (from 63.92 to 104.53 g), chewiness (from 57.97 to 122.84 g), and gumminess (from 63.92 to 118.18), and a reduction in transparency and springiness (p < 0.05). MBDF showed the highest reducing effect on the freeze-thaw dehydration of H-EWPG (from 39.02 to 21.62%). Therefore, addition of MBDFs modified by heating, enzymolysis united with acrylic-grafting or hydroxypropylation can improve gel properties of H-EWPG.