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Published in Applied Research
Using rice flour to produce gluten free bread without additives

The prevalence of celiac disease has led to the growing demand for gluten-free bread. A study published in LWT-Food Science and Technology has sought to develop a gluten-free rice bread without the addition of additives. The researchers investigate the use of Pickering Stabilisation to produce gluten-free bread with a similar consistency and volume to traditional wheat-flour loaves. Pickering emulsions are those that are stabilised by solid particles which adsorbed onto the interface between the two phases. Previously, rice-flour bread has lacked the familiar bubble structure and volume found in traditional bread and have used additives to artificially induce this structure as the rice flour lacks gluten.

The researchers used 11 types of rice flour products, six of which were produced using wet jet milling, 3 by dry roll milling, 1 by dry jet milling and 1 by wet stamp milling. The flour was added to water and mixed at 160 rpm for 20 minutes. After this period of time, sugar, yeast, butter and salt were added and the batter was mixed again for another 20 minutes. Once mixed, the batter was left to ferment at 40°C for 30 minutes and baked for 24 minutes at 180°C.

The researchers measured the volume, determined the damaged starch in flour samples, and analysed the microstructure of the batter before and after fermentation. Yano et al. observed that the batter had “an appearance and texture of slurry” so ensured during mixing that the batter was free of lumps. During the fermentation process the batter resembled whipped cream.

Yano et al. discuss the mechanism involved in bread rising, noting that thickening agents are often added to gluten free batter to confine carbon dioxide produced the yeast during fermentation. However as no additives were used they wanted to investigate how the bread had risen. The scientists found that the flour produced by wet-milling produced a batter and bread that “both contained bubbles coated in uniform undamaged starch particles in a stone wall arrangement” which they indicate is reminiscent of Pickering emulsions/foam. This structure had formed due to the surface activity shown by the undamaged starch granules. The low starch damage also produced bread that had a similar volume to that of wheat bread. They discovered that this specific milling technique of wet-milling, produced the undamaged starch particles. Flours which had damaged starch particle, did not have the same effect due to their inability to lower the surface tension of the water. Using these other flours therefore, the formed bubble walls tended to collapse.

In conclusion Yano et al. suggest that using wet milling would allow a new type of bread that would be of beneficial to celiac but indicate that further investigations are required into the exact nature of the swelling mechanism.