超微細化研磨對國產大豆原料之機能性成分的影響

Abstract

本試驗使用國產黃豆(高雄一號)及黑豆(台南六號)為原料，經發芽、濕熱及乾熱三種預處理後，以行星式球磨機製備超微細化全大豆樣品，並評估超微細化研磨對於大豆機能性成分、抗營養因子及起泡性質等之影響。大豆(含5%固形物) 經1 hr研磨後，其d90和平均粒徑顯著下降，繼續研磨時，全大豆樣品之粒徑雖持續降低但其趨勢漸緩。ㄧ般成分分析結果顯示，超微細化全大豆樣品以Soxhlet和Soxtec抽提器萃取出之粗脂肪含量顯著偏低，但其以酵素-重量法測定之水不可溶性膳食纖維含量則顯著偏高。超微細化研磨全大豆樣品經由酸水解後，再以以彌及石油醚萃取出之粗脂肪含量則與原大豆樣品之測定值接近。推測超微細化研磨會改變樣品中油脂存在的形式，大豆中之油脂可能與蛋白質及纖維等形成結合態油脂，致使其油脂萃取不完全。當提高研磨時之大豆含量為15%，研磨10 hr後，達研磨極限，全大豆樣品之d90為22.86 μm，平均粒徑為10.76 μm。經超微細研磨10 hr之黃豆、黑豆及其分別經發芽、濕熱及乾熱三種預處理之全大豆樣品，以乾熱處理者具有較高的研磨效率，其平均粒徑約為3 μm。超微細化研磨之黑豆與經發芽預處理者，其DPPH自由基清除能力較未經研磨者為高，而經相同處理之超微細化研磨黃豆樣品則較未經研磨者為低；顯示超微細化研磨有助於生黑豆及發芽黑豆表皮中機能性成分之釋放。發芽、濕熱及乾熱處理均可顯著提升黃豆及黑豆中去醣基異黃酮及總異黃酮之含量。除乾熱處理之黃豆及黑豆外，超微細化研磨可顯著提高超微細化全大豆樣品中去醣基異黃酮之含量，但超微細化研磨亦會造成部分全大豆樣品之總異黃酮含量的下降。乾熱處理會顯著降低黃豆及黑豆中植酸之含量，而超微細化處理則會使經乾熱處理之黃豆與黑豆之植酸含量提高。加熱處理亦會使黑豆及黃豆中大豆凝集素完全變性，而超微細化研磨對於大豆中凝集素活性之影響則不顯著。發芽、濕熱及乾熱三種預處理均會造成黃豆及黑豆樣品之起泡性質下降，其中下降的程度以乾熱處理者為最大，發芽處理者最輕微。超微細化研磨對生豆及發芽處理大豆之起泡性有降低的趨勢，但卻可提高濕熱及乾熱處理之超微細化全大豆樣品之起泡性。整體而言，大豆經發芽、濕熱、乾熱之預處理及超微細化研磨處理有助於提升其機能性及生物利用率，具有作為高機能性全大豆產品的開發潛力。

The effects of ultrafine-milling on the contents and conversions of bioactive compounds in selected domestic soybean varieties (soybean KS1 and black soybean TN6) without and with pretreatments (germination and thermal treatments) were studied. The matured seeds, germinated, moist-heated and dry-heated soybeans were further milled to produce ultrafine-milled whole soybean pastes by using a planetary ball mill. The particle size was distinct reduced during the first hour of milling, and then the size reduction was slow down. The crude fat contents of ultrafine-milled whole soybeans decreased while the contents of insoluble dietary fiber increased significantly. The fat contents were increased in ultrafine-milled whole soybeans and insoluble dietary fiber were increased when test samples were acid-hydrolyzed before solvent extraction. These results indicated that the oil in soybeans was complexed with other ingredients (such as proteins and carbohydrates) during milling that resulted in the difficulty in the solvent extraction of crude fat determinations. After 10 hours of milling, the mean particle sizes of 10.76 µm and d90 of 22.86 µm could be obtained from 15% (w/w) soybeans. In comparison of milling efficiency, the dry-heated soybeans had the best milling efficiency with the mean particle sizes of 3 µm. DPPH scavenging capacity of ultrafine-milled soybeans (KS1) decreased but increased in ultrafine-milled black soybean (TN6). Germinating and thermal treatments slightly increased the total isoflavone contents but significantly increased the aglycones of isoflavone. The alycones of isoflavone were significantly increased in the ultrafine-milled soybeans, while the total isoflavone contents were decreased after ultrafine milling. The phytate contents were significantly decreased in dry-heated samples. Ultrafine-milling process did not affect the phytate contents in raw, germinated and moist-heated soybeans, but did increase the phytate contents in ultrfine-milled soybeans with dry-thermal pretreatment. The lectin activity was undetactable in thermal treated soybeans. Foam capacity was significantly affected by the germination and thermal treatments. The ultrafine-milling process decreased the foam capacity of raw and germinated soybeans while increased the foam capacity of thermal treated soybeans. The germination, thermal treatment and ultrafine-milling process may improve the bioavailability of bioactive compounds in soybeans so that the ultrafine-milled whole soybean pastes have great potentials for developing on the functional foods made with whole soybeans.