For bubble measurements, the muffins were cut on a horizontal plane at a distance of 2.5 cm from the base and images of the freshly cut surface of the crumb were captured using a flatbed scanner (HP4300c, Hewlett Packard, USA). Image processing was performed using Image Pro-Plus 4.5 software (Media Cybernetics, USA).
The images were converted to an 8-bit grey scale and segmented separately using a histogram-based segmentation that was defined individually for each image. The bubbles within an area of 0.04 m2 were counted. Two muffins from each batch (four determinations)were measured.