The differences in water absorption properties were investigated among three types of flat pastas (LT: pasta dried at low temperature 50°C for 20 hours ; HT: pasta dried at high temperature 70°C for 11 hours; VHT: pasta dried at very high temperature 85°C for 4 hours). Pastas were soaked at different temperatures and for different times in a thermostatic bath to investigate moisture distributions. Water content was examined a dryer at 105°C for 72 hours. The pasta was then frozen in liquid N2 and cross-sectional images were taken to reveal the moisture profile. Pasta surfaces were observed by scanning electron microscope (SEM). Ultrasound phase difference was applied to analyse water absorption pattern of the three pasta types. The three main results are as follows: 1.) At both low soaking temperature (40-55°C) and high soaking temperature (75 -90°C), there were no significant differences in water absorption rate among LT-, HT- and VHT-dried pasta, but near the starch gelatinization temperature (60-65°C), LT-dried pasta had the largest water absorption rate. 2.) Analysis of ultrasound phase differences showed that when pasta samples processed under the same condition were soaked, phases of pasta soaked above the gelatinization temperature were larger than phases of pasta soaked below the gelatinization temperature. However, when pastas dried at different temperatures were soaked below the gelatinization temperature, phase differences of LT and HT-dried pasta were larger than phase differences of VHT-dried pasta. 3.) Phase not only reflects the absorption rate, but also the distribution of water content inside the pasta. We suggest that phase difference of pasta did not only depend on the drying temperature, but also water content and the gelatinization distribution.
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