Rice ripened at lower temperature slows firming of bread

Firming of bread after baking leads to waste due to loss of palatability. Firming is affected mainly by amylopectin, a starch component. Here, we found that the firming rate of rice bread can be slowed by using flour made from rice grains which filled at lower temperatures, because temperature during grain filling (TGF) affects amylopectin chain synthesis. We found significant positive correlations between TGF and firming rate of gluten-containing rice bread (rice flour 80% + wheat gluten 20%) and rice-flour-containing wheat bread (wheat flour 80% + rice flour 20%) made from samples of rice grains filled at 21.0-28.3 °C. Regressions indicate that if TGF is decreased from 27 to 22 °C, the shelf life of gluten-containing rice bread will be extended by about 150%, and that of rice-flour-containing wheat bread by about 50%. The slow-firming effect was confirmed by sensory tests. This result is potentially applicable to other cereals such as wheat, whose amylopectin structure is also affected by TGF.