Expansion of rice flour treated with lactic acid and sodium bisulphite

This study aimed to develop the expansion property of rice flour using a 22 complete factorial experimental design, investigating the effects of sodium bisulphite concentration and pH on the expansion capacity, carbonyl and carboxyl contents and viscoamylographic behaviour. The sodium bisulphite concentration and pH influenced the development of the expansion property of the lactic acid treated rice flour, presenting the best volumes at pH 4 with 2.18 and 7.82 g/100 g sodium bisulphite. In order to express the highest specific volume, the proportion between the carbonyl and carboxyl groups was more important than the sum of the two, the best proportion being between 0.3 and 0.4 carbonyl and between 0.6 and 0.7 carboxyl. The chemical modification using lactic acid and sodium bisulphite affected the maximum viscosity of the rice flour, but did not influence the minimum or final viscosities.