臺灣高直鏈澱粉玉米與硬質玉米全穀粉之安定化

Abstract

本研究共分為三大部分，第一、二部分擬以農試所新育種並安全生產(good agriculture practice, GAP)之高直鏈澱粉玉米(GEM0067)及國產硬質玉米(TN1)為試驗原料，建立玉米之全穀粉批次安定化技術。並透過分析安定化玉米全穀粉組成及酸價，藉此訂定其規格與完成保存期限之評估。結果顯示，經乾熱(150°C烘箱/30min)或濕熱(95°C滅菌釜/30min)處理之籽粒，皆顯著延緩其研磨製品氧化酸敗。然而，乾熱處理會產生烤焙香味及深褐色色澤，且喪失其糊液黏度；濕熱處理則無色澤、風味與糊液黏度上的顯著變化。與未經熱處理的樣品相比，經濕熱處理者於一般成分、機能性成分(總黃色色素、葉黃素、玉米黃質及總酚類化合物)及澱粉消化性質(澱粉體外消化性質及預估升糖指數)上皆無明顯差異。而比較樣品變異，可發現高直鏈澱粉玉米之機能性成分及消化性質分別顯著高於及低於硬質玉米。此外，安定化高直鏈澱粉玉米全穀粉仍舊保留高抗性澱粉 (RS content=34.98%, starch)及低eGI (51.34)，具有作為低升糖指數食材的潛力。第三部分則以農試所新育種並安全生產(good agriculture practice, GAP)之高直鏈澱粉玉米(HAM)及國產硬質玉米(MF3)為試驗原料，建立安定化玉米全穀粉之連續化生產技術，並分析高直鏈澱粉玉米及安定化硬質玉米全穀粉之貯藏安定性及糊液黏度性質。結果顯示，連續式擠壓處理後之樣品乾燥至水分含量7%以下，可避免初始酸價提高。經擠壓條件:進料水分25%、末段加熱套筒60°C、螺軸轉速120 rpm熱處理後，亦可顯著延緩其研磨製品氧化酸敗。此外，擠壓處理沒有色澤、風味與糊液黏度上的顯著變化。相較於批次乾熱或濕熱處理，連續式擠壓處理抑制酸價上升的效果有限，需嚴格控制其全穀粉產品之水分含量，以避免貯藏過程中氧化反應的加劇。本研究成功利用批次乾熱與濕熱處理及連續式擠壓處理針對玉米籽粒或玉米全穀粉進行處理，於不顯著改變其澱粉性質的情況下延緩酸敗並增加貯藏安定性，延長產品保存期限，有利於國產玉米全穀粉之產業應用與推廣。

This study is divided into three parts. In the first and second part, GAP domestic cultivated flint corn (TN1) and high amylose corn (GEMS0067) which are innovatively bred and safely produced would be used for experimental materials in order to establish batch stabilization technology of whole corn flour. Meanwhile, whole corn flour composition will be determined, then the specification and predicted shelf life are established. The result shows that both dry-heating (150°C oven/30 min) and wet-heating (95°C autoclave/30 min) pretreatments applied to the kernels before dry milling retard the development of rancidity. Besides, wet-heating pretreatment won’t significantly change the color, flavor and pasting property rather than dry-heating pretreatment. In contrast to control, batch wet-heat treated group have no obvious difference on proximate composition, functional ingredients (higher total yellow pigments, total phenolics, lutein and zeaxanthin) and digestive properties (in vitro digestibility and estimated GI). Besides, comparing to whole flint corn flour, high amylose corn flour shows higher functional ingredients and lower digestive properties. Since wet-heating pretreatment won’t make effect on the digestive properties, the storage stable whole high amylose corn flour still remain high content of RS (34.98%, starch) and low eGI (51.34), making it be potential for the low GI ingredients. In the third part, GAP domestic cultivated flint corn (MF3) and high amylose corn (HAM) which are innovatively bred and safely produced would be used for experimental materials in order to establish continuous production technology of storage stable whole corn flour. The result of storage test shows that samples produced by continuous extrusion treatments dry to lower than 7% moisture content can avoid the increase of initial acid value. In addition, extrusion treatment on the condition of feed moisture 25%, last barrel section temperature 60°C and screw speed 120 rpm retards the development of rancidity and makes slight changes on color, flavor and pasting property. In contrast to batch dry-heating and wet-heating, whole corn flour products after the continuous extrusion treatment is not effective on restraining the increase of acid value, so it is necessary to strictly control the moisture content of the whole grain powder product to avoid the increase of oxidation reaction during storage. This study successfully used batch dry-heating or continuous extrusion treatment on corn kernels or whole corn flours in order to retard the development of rancidity without significant changes on starch property. Both treatments have ability to fortify storage stability, extending shelf life of whole corn flour. Thus, this results are beneficial to the industrial application and promotion of domestic cultivated whole corn flours.