Process optimization of wheat flour crisp puffing by radio frequency and the accompanying property changes of starch

This research performed the process optimization of wheat flour crisp puffing by radio frequency (RF) and investigated the accompanying property changes of starch. Experiments were performed in a 6 kW, 27.12 MHz pilot-scale RF system. The results showed that the volume expansion was highest (220%) when the conditions were employed as follows: electrode gap (115 mm); height of the sample (55 mm); initial moisture content of the sample (30%). Under these conditions, the samples were puffed at 120 s by RF, and changes in the starch properties were further observed. The results showed that the structure of the starch was destroyed, changing from oval and spherical in shape to fragmented. The crystal type of the starch changed from A to A + V types. Its crystal order was reduced, and the Fourier-infrared spectrum showed that the ratio of (1048/1022) cm(-1) decreased from 1.142 to 1.047. The crystallinity decreased from 48.27% to 17.57%. These changes will help starch digestion and absorption in human body. These results indicated that RF puffing could become a potential development method for puffed snacks.