Hard pretzel characterization and process optimization.

摘要

Since obtaining flours with prescribed quality is not a practical consideration for small-sized, low profit-margin pretzel companies, research was launched to see if the variability in flour properties could be accommodated by manipulating process conditions. Therefore, a screening experimental design was used to identify critical processing parameters influencing pretzel quality.; Eleven process variables were selected and a two-level-eleven-factor (211) fractional factorial experimental design was used to screen a variety of process variables. Several responses were measured for dough before and after extrusion, for half-baked and fully baked pretzels. The responses selected are important indicators of consistency and quality during pretzel production. Results indicated that flour protein content, the amount of water added to make dough, and dough mixing time were important variables influencing dough behavior.; Based on the above results, four process parameters; baking time, temperature in baking oven zone 1, drying time and drying temperature, were further selected for optimization. The overall effect analysis of the four parameters on the responses also suggested that baking time had the most significant impact on all responses investigated among the four factors.; Surface starch granules were gelatinized following treatment with alkali or water at 80°C, but the interior of the product was not gelatinized when treated with hot alkali or water at the pilot plant. Furthermore, the amylose-lipid complex dissociated even at low temperature of alkali treatment, but the dough hydration property did not show a significant increase until the temperature increased to 80°C. Dough surface color after dipping was different but was not significantly different following baking when pigments were extracted from the flour. The results suggest that significant changes occur following treatment with alkali. The development of pretzel color could not be attributed to any pigments present in the flour but possibly is due to reactions within or between the starch or protein hydrolysis derivatives during baking. (Abstract shortened by UMI.)