Addition of Instant Shear Heat Milled Pregelatinized Rice Flours on a Gluten-Free Pizza

A new shear heat milling machine (SHMM) was used to produce pregelatinized flours instantly without additional water and with lower energy consumption. There has been an interest in expanding the application of Japonica rice flour. Nevertheless, its properties for bakery products are less than ideal, as it lacks the gluten protein matrix. Therefore, pregelatinized (AF) and regular (BF) flours were prepared using 2 Japonica rice varieties: Hoshiyutaka (HF) and Mizuhochikara (MF). Their physicochemical properties were determined, including crystallinity, hydration capacity, and pasting properties. These flours were applied to 100% rice pizza doughs at 0%, 10%, and 20% substitution levels of the AF. The doughs were subjected to rheological tests, such as a stress sweep and frequency sweep, and both the dough and baked pizza bases were observed using a scanning electron microscope (SEM). We observed that hydration capacity is significantly increased in MAF and HAF. The AF increased the dough's viscosity in rheological tests, with 20% substitution having the most notable effect. SEM images show more isolated starch granules in 0% substitution samples, whereas 10% and 20% show them covered by other materials, which we hypothesize are free starch chains of the AF. That extra structure aids the dough's manageability during processing and even baking results. In the SEM images for the baked samples, regular 0% samples showed coalesced bubbles and cracks, while 20% showed flattened small cells that were unable to expand. Therefore, we conclude that a 10% substitution had the best inner structure, with small, round cells.