以微波─醋酸處理生產顆粒狀冷水可膨潤玉米澱粉

Abstract

預糊化澱粉或顆粒冷水可膨潤澱粉是廣泛應用於即時食用產品。本研究之目的是利用短時間微波加熱濕潤粉體為製程，期望得到生產冷水可膨潤澱粉。利用三種不同直鏈澱粉含量之玉米澱粉 (糯性、一般玉米及 Hylon V)原料，浸潤不同濃度之醋酸溶液，並以微波快速加熱。結果中顯示微波加熱可使濕潤的澱粉快速地糊化，不同直鏈澱粉含量的玉米澱粉對於微波加熱的敏感度: 糯性玉米澱粉＞一般玉米澱粉＞Hylon V 玉米澱粉。由於醋酸浸潤溶液的濃度會顯著影響糊化，為了得到最適的顆粒完整性及膨潤程度，以反應曲面試驗設計法探討醋酸濃度及微波加熱秒數的影響。最適化條件探討結果顯示糯性玉米澱粉以 5.9M 醋酸溶液浸潤，微波處理 22 秒，在 35°C 中澱粉膨潤力為 4. 95±0.38 (RSM 之估計值為 3.83)；一般玉米澱粉以 4.9M 醋酸溶液浸潤，微波處理 37 秒，樣品膨潤力(35°C)為6.19±0.2 (RSM之估計值為 5.98)；Hylon V 玉米澱粉以 4.7M 醋酸溶液浸潤，微波處理 37 秒，澱粉(35°C)膨潤力為 4.66±0.08 (RSM 之估計值為 4.65)。在顆粒外觀觀察，可明顯觀察到偏光十字現象減弱，在一般玉米澱粉甚至幾乎消失(偏光消失率為 92%)；在 X光繞射圖譜結果，結晶度較天然澱粉降低了 72%。在澱粉成糊特徵方面，發現經過醋酸溶液浸潤及微波處理會造成尖峰黏度下降。在澱粉分子的分子量分佈結果中沒有顯著改變，顯示醋酸-微波處理可能為一種物理性修飾。

Pre-gelatinized or granular cold-water swelling starch (GCWSS) is widely applied in instant food products. The goal of this thesis was to establish a process to prepare cold-water swelling starch from damped native starch granules by microwave heating. Three corn starches with different amylose contents (waxy, normal and Hylon V) were impregnated with different concentration of acetic acid solution (AcOH) and heated in a domestic microwave oven. As the results showed, the damped starches were rapidly gelatinized by microwave heating. The susceptibility of starches to microwave heating was in the order of waxy ＞ normal ＞ Hylon V. The concentration of AcOH had a significant effect on the gelatinization. In order to obtain the optimal granular integrity and degree of swollen, the response surface methodology was designed to study the influences of the AcOH concentration and microwave time. The waxy corn starch impregnated with 5.9 M AcOH and heated for 22 seconds had the highest swelling power value (at 35°C ) of 4.95 ± 0.38 g/g (predicted from RSM was 3.83 ). The normal corn starch had a maximum swelling power value (at 35°C ) of 6.19 ± 0.2 g/g (predicted from RSM was 5.93 ) by treated 4.9 M AcOH and heated for 37 seconds. A maximum swelling power value (at 35°C ) of Hylon V corn starch was 4.66 ± 0.08 g/g (predicted from RSM was 4.65 ) by treated 4.7 M AcOH and heated for 37 seconds. The birefringence almost disappeared in GCWSS prepared from the normal corn starch shown by microscopic observations and the loss ratio of polarized light reached 92%. Crystalline index of GCWSS prepared from normal corn starch was reduced by 72% than the native starch in the results of X-ray diffraction pattern. The starch pasting profile showed a significant decrease of peak viscosity after treated by AcOH and microwave heating. The molecular weight distribution of starch molecules were not dramatically altered indicated that this acetic acid-microwave treatment is a physical modification.