Characterization of structure of gluten-free breads by using X-ray microtomography

Abstract

The effects of different gums and gum blends addition on crumb structure of gluten-free breads were studied by X-ray microtomography. The gums used were xanthan, guar, locust bean (LBG), agar, methylcellulose (MC), carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC) and the gum blends were xanthan–guar and xanthan–LBG. Porosity, number, average size, aspect ratio and roundness of pores were used as parameters to describe the internal structure of the crumbs. Characteristics of the crumb structure were related to the hardness, cohesiveness and springiness of breads. Gluten-free breads prepared with the addition of MC, agar and no additives had the highest porosity values with the lowest number of pores, which would be indicating a non-uniform crumb structure with large pores. There was a negative correlation between porosity and number of pores (r = −0.90) and a positive correlation between porosity and average size of pores (r = 0.80). Lowest porosity, lowest average pores area and the highest number of pores were observed on gluten-free breads prepared with the addition of xanthan, CMC, xanthan–guar, xanthan–LBG and HPMC. The higher number of smaller pores is associated with a finer crumb structure. Data showed that the hardness values of breads were positively correlated with porosity (r = 0.87) and average area of pores (r = 0.87) and negatively correlated with the number of pores (r = −0.92). On the other hand, cohesiveness and springiness values of breads were negatively correlated with porosity (r = −0.86 and −0.88), average area of pores (r = −0.81 and −0.90) and positively correlated with number of pores (r = 0.89 and 0.88).