Charcoal bread: Physicochemical and textural properties, in vitro digestibility, and dough rheology

Abstract

A hedonistic black color was imparted to bread by adding activated vegetable charcoal (AC; 0, 0.5, 1, 2 and 4 g/100 g wheat flour). The addition of AC had a significant effect on dough rheology and on bread specific volume, color, texture, and in vitro starch digestibility. The apparent viscosity and the viscoelastic moduli of dough were enhanced. Color parameters a* and b* tended to a value of zero, and that of L* was sharply lowered, indicative AC tended to suppress color and luminescence, and imparting a black color to bread. Bread specific volume decreased as AC increased, probably due to the ability of AC mesoporous structure to adsorb the gas formed during dough leavening, depleting the gas available for gluten network retention. Concomitantly, bread hardness increased as AC increased. Bread made with 4 g of AC per 100 g of wheat flour displayed a hydrolysis rate decrease of about 50%, reduced by 35.09% the readily digestible starch (RDS), and increased by 15.87% slowly digestible starch and by 74.85% the resistant starch fractions, compared to the respective contents of these fractions in the control bread without added AC. Overall, the results showed that the addition of a relatively small level (1 g/100 g flour) of AC led to improved starch digestibility (~21% reduction in RDS, ~19% increase in SDS and ~42% in RS), a moderate increase in bread hardness, and imparted a suitable hedonistic black color. These results pinpoint AC as an attractive suitable ingredient with innovative potential applications in bread.