利用韃靼蕎麥開發膨發米點心之研究

韃靼蕎麥（Fagopyrum tataricum），又名苦蕎麥，屬於蓼科蕎麥屬，原產於中國西部山區。台灣栽種品種以台中2號為主，含有平衡的胺基酸、脂質、膳食纖維、礦物質、多酚及豐富類黃酮物質，特別是芸香苷（Rutin）。研究指出食用韃靼蕎麥對人體有多種益處如抗氧化和抗發炎等功效，獨特的營養和功能性成分具良好的市場潛力，然而未經處理韃靼蕎麥本身的強烈苦味，造成相關產品較少和消費者的接受度不高，苦味的主因已被研究證實，源自韃靼蕎麥本身的芸香苷降解酶（Rutin-Degrading Enzymes, RDEs）於加工過程中使芸香苷降解成槲皮素所致。擠壓加工為高溫短時（High-temperature Short-time, HTST）的加工程序，對於酵素滅活具顯著的作用，並包含許多優點如新產品開發、營養保留、大量生產、廢棄物和廢水量少等優點。因此本研究將糙米和韃靼蕎麥粉混合，經國產單軸擠壓機膨發製成米點心以開發具特殊風味和有益健康之膨發米點心。本實驗採4x3複因子膨發擠壓試驗，探討不同韃靼蕎麥粉比例（0%、15%、30%、45%）、螺軸轉速（320 rpm、350 rpm、380 rpm）及固定的套筒溫度110 ℃對於擠出物之理化性質變化，和芸香苷降解酶是否有抑制作用。研究結果顯示，在色澤部分，隨著韃靼蕎麥粉添加比例增加，擠出物L*值下降、b*值上升，韃靼蕎麥的添加使擠出物顏色較深；在物理性質部分，以45%韃靼蕎麥粉在螺軸轉速350 rpm下生產之擠出物具最高徑向膨發率（3.69）和硬度（3.03 kgf），韃靼蕎麥粉的增加使擠出物的吸水性指標上升、水溶性指標下降，表明添加韃靼蕎麥粉能改善糙米擠出物之物理特性；在芸香苷降解酶活性部分，所有添加韃靼蕎麥擠出物，經加水處理後，具低含量的槲皮素（0.10-0.39 mg QC/g d.m.），說明擠壓處理能抑制芸香苷轉化為槲皮素；而在抗氧化能力方面，隨著韃靼蕎麥粉比例增加，能改善擠出物之抗氧化能力，具顯著差異（p<0.05）。當添加45%韃靼蕎麥粉，以螺軸轉速320 rpm時，擠出物具最高的總酚類化合物含量（150.86 mg GAE/100 g d.m.）、總類黃酮化合物含量（284.08 mg RE/100 g d.m.）、DPPH自由基清除能力（88.46%）和亞鐵還原能力（Ferric Reducing Antioxidant Power, FRAP）（260.42μmol FeSO4/L）。感官品評試驗樣品，經最佳操作條件之選定與評估後，在0%、15%、30%和45%韃靼蕎麥添加，各挑選一組擠出物進行試驗。於感官品評上，0%添加的整體接受度最好，而添加韃靼蕎麥粉之組別中，以15%和30%韃靼蕎麥粉添加接受度相近。綜上所述，韃靼蕎麥粉的添加能改善糙米擠出物之物理性質和抗氧化能力，且證實擠壓處理為一種可行滅活韃靼蕎麥中內源性酵素芸香苷降解酶的方法，本研究中以30%韃靼蕎麥粉添加、螺軸轉速380 rpm為本實驗韃靼蕎麥擠出物之最佳操作條件。

關鍵字

膨發點心；韃靼蕎麥；芸香苷降解酶；槲皮素；擠壓

並列摘要

Tatary buckwheat (TB, Fagopyrum tataricum) is a member of the Polygonaceous family native to the western mountains of China. The commercial cultivar in Taiwan is Taichung no.2. Tatary buckwheat is high in amino acids, lipids, dietary fiber, minerals, and polyphenols, particularly the flavonoid rutin. Past research has reported the physiological effects of TB in particular its effect against oxidative stress and inflammation. Its unique functional components have great market potential, but consumer acceptance is mostly held back by its strong bitter taste. The bitter taste has been attributed to quercetin, the degradation product of Rutin-degrading enzymes (RDEs). Extrusion is a high-temperature short-time (HTST) process with significant effects on enzyme inactive. Using extrusion brings the opportunity for new product development, better nutrient retention, and lower waste from polluted water and biomass. This study aims to measure the effect of extrusion on the degradation of RDEs, levels of bioactive compounds, and the physical properties of TB-supplemented brown rice extrudates to come up with a puffed rice snack product with acceptable nutrition levels and flavor. The study has a 3x4 two-factors design with different proportion of Tatary buckwheat (0%, 15%, 30%, 45%) and screw speeds (320, 350, 380 rpm). Higher proportions of Tatary buckwheat were found to decrease the color lightness (L*) and increase the yellowness (b*) in brown rice extrudates. Extrudates produced with 45% Tatary buckwheat flour at 350 rpm had the highest radial expansion rate at 3.69 and a hardness of 3.03 kgf. Higher proportions of Tatary buckwheat flour increase the water absorption index and decreases the water solubility index of the extrudate, which are desirable in extrusion products. All the extrudates containing Tatary buckwheat had a low level of quercetin content of 0.10-0.39 mg per g d.m. after water treatment, indicating that extrusion treatment inhibited the enzymatic conversion of rutin into quercetin. Increased ratio of Tatary buckwheat flour improved the antioxidant capacity of extrudates significantly (P < 0.05). Extrudates made with 45% Tatary buckwheat flour and 320 rpm screw speed had the highest total phenolic content (150.86 mg GAE/ 100 g d.m.), total flavonoid content (284.08 mg RE / 100 g d.m.), DPPH free radical scavenging activity (88.46%) and ferric reducing antioxidant power (FRAP) (260.42 μmol FeSO4/L). Optimal operating conditions were implemented for the different Tatary buckwheat ratios and the sensory qualities of the resulting extrudate were evaluated. Extrudates with no addition of Tatary buckwheat flour had the highest overall acceptance, while extrudates with 15% and 30% Tatary buckwheat powder had similar acceptance. The addition of Tatary buckwheat flour was found to improve the physical and antioxidative properties of brown rice extrudate, and extrusion was able to inactivate the endogenous rutin degrading enzyme of Tatary buckwheat. The optimal condition was found to be producing extrudates with 30% Tatary buckwheat addition at a die temperature of 110 ℃ and screw speed of 380 rpm.