Effect of using riceberry flour and xanthan gum on physical properties and estimated glycemic index of steamed rice cakes: optimization by D-optimal mixture design approach.

Riceberry, a Thai black rice variety () has been developed with the aim to provide high iron and low glucose to consumers. Therefore, riceberry could potentially be used to produce healthier processed foods. In this regard, a D-optimal mixture design was employed for the optimization of the steamed rice cakes which included ten combinations of riceberry flour (RF), xanthan gum (XG) and glutinous rice flour (GRF). The influence of RF substitution for GRF with XG addition on the texture, physicochemical and sensory properties, as well as the estimated glycemic index (GI) of the steamed rice cakes, were studied. The results demonstrated that RF, XG, and GRF had a noticeable effect on GI, textural, and sensory properties of the steamed rice cakes. XG was the variable that most affected hardness, adhesiveness, cohesiveness, and gumminess of the steamed rice cakes by the positive effect. XG had a negative effect on hydrolysis index and GI. The optimum mixture obtained on a basis of overall liking, hardness, adhesiveness, gumminess, and GI value contained 39% RF, 1% XG, and 60% GRF with desirability equal to 0.673. For filling, the red bean paste with 100% isomaltulose substitution for sucrose indicated the lowest value of GI and the highest score of the overall liking. The optimum steamed rice cakes stuffed with the red bean paste used isomaltulose as a sucrose replacer were classified as the medium GI food.