大豆粉對麵糰色澤及品質之影響

Abstract

本研究擬以非基改國產大豆製備具脂肪加氧酶(lipoxygenase, LOX)活性全大豆粉以取代麵粉改良劑中的化學氧化劑，如過氧化苯甲醯(BPO)提供麵粉製品增白及麵糰質地性質改善之應用。為了增加大豆粉之安定性，將大豆粉脫去部分脂肪和色素，以延長大豆粉的保存期限及增強其在麵粉中的增白效用。試驗中，將全大豆粉以索氏萃取法進行不同程度之脫脂，並測定其LOX活性，以製備出具安定性及可改善麵粉製品色澤和質地的脫脂大豆粉。結果顯示， LOX 的比活性隨全大豆粉脫脂程度之提高而降低，以萃取1小時後的大豆粉含有較低的粗脂肪含量，並仍能保有相當之酵素比活性。為探討全大豆粉及脫脂全大豆粉對麵糰之色澤及質地之影響，試驗中，將於四種組成與理化性質不同之麵粉(W-C、W-S、W-G及W-H)中分別添加兩種國產全大豆粉及其自行製備之脫脂全大豆粉：黃豆(高雄10號，S-KS10)、脫脂黃豆粉(D-S-KS1.5-1h)、黑豆(台南3號，B-TN3)和脫脂黑豆粉(D-B-TN3-1h)，另亦添加市售大豆粉S-MG、市售脫脂大豆粉S-7B及化學氧化劑BPO等作為對照組製作麵帶。麵帶將測定色澤、質地與流變性質，並使用掃描式電子顯微鏡(Scanning Electron Microscope, SEM)觀察麵帶之斷面微細結構，以了解不同的大豆粉樣品對性質有差異之麵粉所製備之麵糰色澤與質地的影響。針對全大豆粉對於麵糰色澤及質地之影響試驗，結果顯示，全大豆粉的添加對四種麵粉所製備之麵帶質地與流變性質有顯著的影響，其中以添加1.5%的S-KS10之色澤改善效果最佳。全豆粉的添加對於高灰分之混合粉(W-H)之色澤改善效果較不明顯，推測原因之一為麵粉本身之色素含量、酚類化合物與酚過氧化酵素之活性較其他三種麵粉高，導致麵帶在鬆弛期間持續進行褐變反應，但添加全大豆粉後，確實可以增強麵帶之筋性與改善麵糰的性質。自行製備之D-S-KS10-1h以1.5% 添加入麵粉中亦能讓相對低PPO活性之麵粉(W-C和W-S)的麵帶增白，並且在四種麵粉中皆有着幫助增強筋性的用途。

The domestically produced non-genetically soybean flour S-KS10 and black soybean flour B-TN3 were used as the materials in this study for replacing the chemical oxidant such as benzoyl peroxide (BPO) in baking industries. Lipoxygenase (LOX) in soybean has been used in food for several flour products, and its abilities of bleaching and gluten strengthening are well-known. Since soybean is rich in fat, easily oxidizes during storage, preventing soybean from rancidity is crucial. With the aim of producing a soybean flour with long shelf-life and high specific activity of LOX, the crude fat of S-KS10 and B-TN3 have been extracted by using Soxhlet system within 2 hours and the specific activity of LOX in defatted soybean flours was accordingly monitored. The results indicated that the specific activity of LOX is proportional to the crude fat content of soybean flours. Those flours which were defatted for 1 hour retain LOX specific activity and low crude fat. For comparison, we added the soybean flours (S-KS10 or B-TN3) or defatted soybean flours (D-S-KS10-1h or D-B-TN3-1h) into 4 wheat flours (W-C, W-S, W-G, and W-H) whose diverse properties have been identified in this study. Therefore, the effect of introducing soybean flours with/without defatting on the color and textural properties of dough was investigated. Likewise, commercial soybean flour (S-MG), commercial defatted soybean flour (S-7B), and BPO were also introduced into wheat flours to make dough sheets. The dough sheets containing either commercial or self-prepared soybean flours were again compared in aspect of their color, textural and rheological properties. The results showed that the addition of soybean flours had significant positive effects on the textural and rheological properties of dough sheets. The addition of 1.5% of S-KS10 had the greatest improvement in the color of dough sheet. For W-H containing high ash content, the color improvement of dough sheets from the addition of soybean flour was hard to observe. This may due to the high pigment content, polyphenol oxidase activity and phenolic compound content of the W-H flour, causing a dark appearance in its dough sheet. For the dough sheets made of W-H flour, the improvement in texture after introducing the soybean flour was also observed in this study. Although the D-S-KS10-1h has a low LOX specific activity, it works on bleaching the dough sheets made of W-C and W-S and also improves the dough firmness.