糯米榖粉是製作中國米食點心常用之原料,了解糯米榖粉製品之物化性質將有助於產品製程的設計與品質的改善。本實驗以熱差式掃描儀 ( DSC )、電子顯微鏡 ( SEM ) 與動態流變儀探討加熱條件、攪拌與槌打等對糯米榖粉製品物化性質之影響。 提高加熱溫度或增加水份含量有助於澱粉糊化,進而影響產品的顯微結構。當糊化度低於 50% 時,不會產生網狀結構;糊化度高於 80% 所有產品皆會形成網狀結構。當水份含量介於50 ∼ 80%,只有高水份含量( 80%)產品才有較佳的網狀結構生成。機械力(攪拌與槌打)會減少G/與G//,但有助於網狀結構的生成。低水份含量下( 45%)的槌打對於降低容積密度與提升喜好性指數並沒有顯著效果,但攪拌及槌打皆仍有助於網狀結構形成,孔洞數目隨加工時間增長而增加。 55%水份含量製品經槌打超過 600 次時會破壞網狀結構,喜好性指數與網狀結構為正相關性。當產品水份含量達 65% 時,攪拌和槌打有助降低容積密度,但無法形成網狀結構,喜好性指數亦隨之降低。
Waxy rice flour is an important raw material for traditional Chinese foods. It is necessary to understand the physicochemical properties of cooked waxy rice products for process design and quality control. Effects of heating conditions (time, temperature and moisture content ), agitation and pounding on physicochemical properties of cooked waxy rice products have been investigated by using different scanning calorimerty (DSC), oscillatory rheometer and scanning electronic microscope (SEM). Raising temperature or increasing moisture enhanced the starch gelatinization, which affected the microstructure of products. When the degree of gelatinization (D.G.) was lower than 50%, there was no network formed in the products. The network always exists at D.G. no less than 80%. High moisture content (80%) was helpful for forming network when the D.G. ranged from 50 to 80%. The mechanical action (agitation and pounding) resulted in the decrease in G’ and G”, helpful for forming network structure. The higher moisture content would increase the number of porous. At 45% moisture content, pounding wouldn’t lower the bulk density obviously. Both pounding and agitation would enhance the network structure and more pounding or agitation would resulted in more porous. The product with 55% moisture content, the network structure would be destroyed when pounding is more than 500 times. It also shows that the preference index and network structure are positive relation. At 65% moisture content, pounding and agitation would be helpful for lowering bulk density but not forming the network structure. Furthermore, it would also lower the value of preference index.
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