Photo courtesy of Hiroshima University.
The research was published in the June issue of LWT- Food Science and Technology.
Typically, bread made with rice flour lacks the bubble structure and volume found in wheat flour bread, or the bubble structure was induced through additives.
Gluten’s ability to form a flexible matrix is what gives wheat flour bread its familiar texture. Rice flour doesn’t have gluten so these bread characteristics have to be achieved in a different way.
Japan’s National Agriculture and Food Research Organization (NARO) discovered that rice flour produced by a specific type of wet milling produced a loaf that contained bubbles coated in uniform undamaged starch particles in a stone wall arrangement.
Researchers at Hiroshima University investigated this ingredient and found it had novel properties not seen in rice flour before — and these were down to the undamaged starch particles that resulted from its specific milling technique.
These stable “stone walls” apparently form due to the surface activity demonstrated by undamaged starch granules. These granules are able to lower the surface tension of water and so reduce the tendency of the formed bubble walls to collapse. Other rice flours tested, consisting of damaged starch, did not have the same water-tension lowering effect. They were thus devoid of these stable bubbles, and attempts to make bread with them fell flat.
They also found uniform hydrophobicity of the similar sized granules — leading to their confinement to the interface between damp gaseous air pockets and the liquid batter.
This tightknit “stone wall” arrangement thus allows bubbles to grow and expand as CO2 levels increase within leading to successful voluminous bread.