Image Analysis of Gluten-free Breads Prepared with Chestnut and Rice Flour and Baked in Different Ovens

In this study, the effects of chestnut flour and xanthan-guar gum blend-emulsifier DATEM mixture addition on macro- and microstructure of rice breads baked in conventional and infrared-microwave combination ovens were investigated by using the images obtained by a scanner and scanning electron microscopy (SEM). Pore area fraction, pore size distribution, and roundness values of pores were determined. The highest pore area fraction values were obtained in breads prepared by replacement of 46 % of rice flour with chestnut flour containing xanthan-guar gum blend-DATEM mixture and baked in an infrared-microwave combination oven. On the other hand, rice breads containing no additives or chestnut flour had the lowest pore area fraction values. Infrared-microwave combination baking increased both pore area fraction values and total number of pores. Infrared-microwave combination baking caused approximately 23-28 % increase in number of the small pores (0-5 mm(2)) in rice breads and 71 % increase in number of the large pores (> 10 mm(2)) in chestnut-rice breads. The fiber content and larger starch granules of chestnut flour contributed towards the stabilization of gas bubbles resulting in better crumb structure. More homogenous pore distributions were observed when additives and an infrared-microwave combination oven were used. When microstructure of gluten-free breads was investigated, it was seen that starch granules in chestnut-rice breads baked in an infrared-microwave combination oven did not disintegrate completely.