| Summary: | 碩士 === 實踐大學 === 食品營養與保健生技學系碩士班 === 102 === The objective of this study was to evaluate the effects of native tapioca starch (T), pregelatinized tapioca starch (PG), pregelatinized tapioca distarch phosphate (PG-DSP) and pregelatinized tapioca hydroxypropyl distarch phosphate (PG-HPDSP) on the physical and textural properties of dough, wrapper, boiled or steamed dumpling wrappers prepared by flour (control group, C), or blends in which 1 or 2% substitution of different starches, 60% water and 1% salt.
The native starch decreased the water binding capacity in flour blends, but increased dough stickiness, but 2% pregelatinized starches had the opposite influence. All starches made dough with the lower hardness, adhesiveness, gumminess, and chewiness. All starches increased surface stickiness, but reduced the toughness and extensibility of raw dumpling wrapper, 2% PG-HPDSP had similar toughness as the control. By confocal laser scanning microscopy, dough with pregelatinized starches had larger starch granules and weaker gluten network structure; raw wrapper has stronger network than dough. Pregelatinized starches reduced the gelatinization enthalpy of dough; especially for PG-DSP and PG-HPDSP. All heated and stored samples had no retrogradation enthalpy.
Compared with raw wrapper, the boiled dumpling wrapper had the higher surface stickiness, but steamed wrapper had the lower surface stickiness. Stored at room temperature for 2 h made boiled wrapper with higher value of surface stickiness, but steamed wrapper with lower one. Increased substitution of starch can be increase extensibility and cutting toughness of boiled wrapper.
All pregelatinized starch could shorten the optimum boiling and steaming time by 14~43% and 25~35%, respectively; especially for PG-HPDSP. The cooking weight gain of boiled wrapper was in the order of T > C > pregelatinized starches, but that of steamed ones was pregelatinized starches > T = C; PG-HPDSP made the heated wrapper with better quality. At optimum cooking time, 2% PG-DSP could reduce 23% cooking loss. Overall, pregelatinized starches could improve the dough handling and texture of heated wrapper. PG-HPDSP had the lowest heating time, the best cooking weight gain, and the more stable properties during storage.
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