以高直鏈澱粉玉米與硬質玉米開發具機能性之擠壓膨發與沖泡粉產品

Abstract

本研究利用台中霧峰農試所育種之高直鏈澱粉玉米(high amylose maize, HAM)、優質蛋白玉米(quality protein maize, QPM)、與國外引進之高直鏈澱粉玉米(germplasm enhancement of maize, code GEMS0067, GEMS)進行產品加工特性研究，高直鏈澱粉玉米之直鏈澱粉含量皆高於70%。為防止全籽粒研磨之榖粉因油脂氧化產生不良風味，分別利用擠壓與濕式處理的方式進行安定化，由40°C儲藏試驗之酸價結果顯示，經處理之樣品，當水分含量乾燥至7%以下時，酸價不會再上升，具有良好貯藏性，但擠壓及濕式處理則會對穀粉中之澱粉性質及機能性成分含量產生影響。經處理樣品，其一般成分(粗蛋白、粗脂肪及灰分)含量無顯著差異。擠壓處理之三種參數(水分含量、溫度及轉速)對擠出物性質有不同程度的影響；水分含量提高時，會降低剪切作用；溫度升高及轉速提高時，會提高冷水糊液黏度及最終糊液黏度。所有擠壓樣品之玉米黃素及葉黃素含量，則降低至原料的50%以下。優質蛋白玉米(QPM)全榖粉在水分含量小於25%、溫度高於60°C以及轉速大於90 rpm條件操作下，發生澱粉糊化或破損現象。高直鏈澱粉玉米(HAM)全榖粉之澱粉則需要在80-120-140-150-140°C溫度設定，水分含量低至18%才可能被破壞。濕熱安定化處理後，高直鏈澱粉玉米全榖粉的尖峰糊液黏度及最終糊液黏度皆下降，抗性澱粉含量提高，但消化速率加快，水溶解度及膨潤力上升，推測在濕式處理過程中有部分直鏈澱粉溶出，同時產生RS III型抗性澱粉；優質蛋白玉米則相反，其糊化溫度被推遲，推測此處理造成直鏈澱粉重排成緊密結構，又因其可被消化澱粉量及預估升糖指數上升，推測非結晶區受濕式處理破壞，易受酵素作用。兩種玉米全穀粉因直鏈澱粉含量不同而有相反的結果，值得進一步探討濕式處理對澱粉分子結構變化的影響。本研究以質地分析結果篩選兩種即食擠壓產品。另，依據消化性質與風味考量，提出兩種即食性玉米沖泡粉配方產品，與原料消化性質相比，混合後消化速率降低，具有良好市場開發潛力。

This study focused on three varieties of corn, quality protein maize (QPM) and high amylose maize (HAM) bred by Taiwan Agricultural Research Institute and high amylose maize variety GEMS-0067 derived from Agricultural Research Service of United States Department of Agriculture. The amylose contents of two high amylose maize varieties exceeded 70%. The purpose of this research was to stabilize the whole corn flour using either extrusion technology or wet-treatment and to develop both extruded snacks and instant drink products. According to the results of storage test conducted at 40°C, as long as the final moisture content stayed less than 7%, both extrusion and HMT could inhibit the increasing acid value compared to the native control group. But at the same time, the stabilization treatment might change the physicochemical properties of starch and the amount of functional compositions. And the crude protein, crude fat and ash content didn’t change before and after treatment. Moisture content (MC), temperature profile and screw speed as three main parameters of extrusion process, they modified the materials in different ways. Higher input MC would reduce the shearing effect during extrusion, while higher temp. profile and screw speed led to higher cold water viscosity and final viscosity (FV). The lutein and zeaxanthin contents in all samples had declined to less than 50%. As for QPM, the conditions with MC less than 25%, temp. higher than 60°C and screw speed over 90 rpm made starch granules gelatinized or damaged thus having cold water viscosity. However, starch granules of high amylose maize wouldn’t be damaged unless stricter conditions with temp. profile 80-120-140-150-140°C with MC lower than 18% were performed. On the other hand, HMT lowered the peak viscosity (PV) and FV of GEMS-0067 starch in rapid viscosity analysis. At the same time, the resistant starch contents and digestive rate, as well as solubility and swelling power at 90°C, became higher after HMT, indicating the formation of RS and amylose leaching during treatment. In contrast, the pasting temp. of QPM was delayed after HMT accompanied by higher digestible starch contents and eGI value, which implied that HMT might rearranged the amylose chains into more ordered structure but the amorphous region became more accessible for digestive enzymes. The reverse effect of HMT on QPM and GEMS-0067 needed other explanation from starch molecular aspect. Furthermore, this study also developed two extruded snack products and two instant drink formulae based on digestive properties and flavors of samples under mentioned treatment. Compared with the ingredients, the mixed instant drink formulae had much lower digestive rate, indicating competitive potentials as low glycemic index food.