澱粉糊精的物理性質與微波輔助之生產方法

Abstract

爲探討amylodextrin的性質並進一步修飾其特性。利用2.2N鹽酸於35℃下浸漬將玉米澱粉製備成amylodextrin，並觀察水解過程玉米澱粉顆粒的變化，發現當水解率為3.1%時直鏈澱粉及支鏈澱粉皆已經開始降解，並有一些小分子出現，隨水解時間增加，大分子逐漸被降解，至水解率為60.6%時，層析圖為單一狹窄波峰，數量平均聚合度為21、重量平均聚合度為25，其分子量多分散度為1.17；將amylodextrin用酵素去分支後以鏈長差異計算之平均鏈數為1.19，顯示amylodextrin主要為一短鏈，只有分子大小略有差異的直鏈分子。Amylodextrin的相轉移溫度範圍較原澱粉顆粒之糊化溫度廣，經annealing處理後，可使相轉移溫度提高，最初相轉移溫度由63.06℃增加至84.76℃；相轉移溫度範圍縮小，由42.42℃縮小至22.74℃，顯示經annealing處理可增強 amylodextrin的結晶結構，增加其熱穩定性； amylodextrin由於分散於水溶液中後為一牛頓流體，但添加於0.5%與1%之關華豆膠溶液中發現 amylodextrin會改變關華豆膠之流動性，顯示 amylodextrin與關華豆膠產生交互作用，可用來修飾膠體溶液之性質。由於製備 amylodextrin時，於35℃中之時間至少需八天以上，所以利用微波加熱原理製備 amylodextrin以縮短不均勻酸水解所需時間，並利用反應曲面法，以鹽酸濃度及加熱秒數兩種因子對多分散度、分子量及水解率的影響進行分析，顯示以鹽酸濃度在2~2.2N 範圍下，加熱時間在70~75秒範圍下，能得到聚合度為117~123，多分散度為1.30~1.36，水解率為59.5~66.15%的amylodextrin。

Amylodextrin was obtained by soaking corn starch in 2.2N HCl solution at 35℃for 8 days. Molecular-weight distribution of starch was significantly changed, as ratio of hydrolyzed starch reached at 3.1%. Both amylopectin and amylose degraded, and some low molecular- weight amylodextrin presented, as acid hydrolysis proceeded. Amylodextrin used for this study was harvested from batches of acid hydrolysis with average of hydrolyzed starch ratio at 60.6%. Size-exclusion chromatogram of this amylodextrin showed a narrow peak, and the number-average degree of polymerization (DPn) and weight-average DP (DPw) were 21 and 25, respectively, with polydispersity value being equaled to 1.17. The average chain-number was 1.19 calculated from difference of chain-length of amylodextrin before and after debranched reaction by isoamylase. The results indicated that amylodextrin was an essential linear molecule with narrow size distribution. Transition temperature of amylodextrin was higher than gelatinization temperature of native corn starch. After annealing, the transition temperature was increased from 63.1°C to 84.8°C; the transition temperature range was narrowed from 42.42°C to 22.74°C. It indicated that annealing promoted reorganization and perfection of crystalline lamellae of amylodextrin. Amylodextrin suspension was a Newtonian fluid. Addition of amylodextrin to 0.5% or 1% guar gum hydorcolloid caused a synergistic increase in viscosity. To shorten the preparing time of amylodextrin, microwave heating was employed to accelerate the heterogeneous acid hydrolysis. Amylodextrin with 117~123 DP and 1.3~1.36 polydispersity could be obtained from heating corn starch in 2.2N HCl for 70 ~ 75 seconds to hydrolyze 59.5 ~ 66.2% of mass.