利用紅麴菌供開發新口味及機能性乾酪之研究

Abstract

紅麴菌是中國傳統釀造菌株，常被當作釀酒原料、食品著色劑及肉品防腐劑等，於飲食上一直受到相當重視與利用，近年來對於紅麴菌的二次代謝物 (secondary metabolites) 更是加以研究，例如抑制膽固醇合成物質- monacolin K與降血壓物質- γ -胺基丁酸等保健功效皆陸續被發現。本試驗，期望能以國人熟悉的紅麴菌來開發一東方口味並含有機能性成分的新式乾酪。 本試驗使用，產量高monacolin K與產量低 citrinin 之Monascus purpureus NTU 301 為菌元。一般傳統以凝乳酵素作為乾酪凝固之用，本試驗使用葡萄糖酸內酯 (Glucono delta-lactone, GDL) 以酸凝固方式製成凝乳塊混合紅麴菌液，置於 30 ℃，相對濕度 85% 之恆溫恆濕機 10 天可得紅麴乾酪。 首先比較凝乳塊混合 10 與 20% (v/w) 紅麴菌液之紅麴乾酪。添加 20% 紅麴菌液之乾酪的熟成率達 42.4%，比添加 10% 紅麴菌液之乾酪熟成率高出一倍以上。水分皆隨著熟成期間而逐漸減少，混合 10% 紅麴菌液之乾酪，在熟成 10 天後含水量為 20.46%，為超硬質乾酪，在第 8 日後，破斷強度超過 1000 g/cm2，無法直接食用。綜觀之，添加 20% 紅麴菌液之乾酪較符合本試驗之目的，故以此添加比率製作紅麴乾酪，並進一步測定其熟成期間之變化。在紅色度上，a 值由 0.01 增加至熟成末期 13.32。而由電泳圖可觀察出紅麴乾酪的蛋白質被充分水解。黴菌與酵母菌數熟成 0 天時的 4.8 × 105 上升至 5.4× 107 CFU/g，尤其於熟成 3~6 日快速生長達顯著差異 (p<0.05)；由酸性蛋白酶酶分解活性的測定，可知熟成 4~6 天活性顯著上升，而在第 8 天達最高活性 224 unit/mL，與菌數測定結果相符合。最終產品之 monacolin K 與 citrinin 濃度分別為 2.875 ppm 與 0.0535 ppm。若想進一步提高紅麴乾酪中的 monacolin K濃度，可在備製凝乳塊後，與紅麴菌液及紅麴米粉末一起混合均勻製成。但由於直接混入紅麴米粉末，會把空氣中雜菌一起混入乾酪中，進而在熟成期間造成污染，在此建議把紅麴米粉末先經過乾熱處理 (105 ℃，6 hr) 預先混合而製成，其紅麴米粉末 monacolin K 與 citrinin 濃度分別為 80.77 ppm 與 1.14 ppm。 本試驗所得之紅麴乾酪，外表呈紅色，富有濃郁紅麴甘醇風味，且無苦味，並含有少量monacolin K。而建議若欲增加產品中monacolin K含量，可以在凝乳塊混合菌液時，添加經乾熱處理紅麴米粉末。

The Monascus species is a Chinese traditional fermentation fungus used on foods for thousands of years. Monascus species has been proven to produce many functional secondary metabolites. For example, monacolin K and γ-aminobutyric acid (GABA) were individually approved to be a cholesterol-lowering drug and a hypotensive agent. This study is to conduct to produce Monascus-fermented cheese, in order to increase variety of milk products. The Monascus purpureus NTU 301 was used as starter (from National Taiwan University, Institute of Microbiology and Biochemical) in this study which produced the highest amount of monacolin K and GABA,but the lowest amount of citrinin. The cheese-making procedure used glucono delta-lactone to coagulate the milk by acid coagulation, and inoculated with M. purpureus NTU 301 spore suspension. The mixture was ripened for 10 days at 30 ℃, RH 85%. The main results were as follows: Two unripened cheese mixture concentrations (10% and 20% spore suspension of M. purpureus NTU 301) were compared. After ripening for 10 days, the ripening ratio of 20% spore suspension cheese increased from 2.98% to 42.4%, which is twice the ripening ratio of 10% spore suspension cheese. Moisture content decreased with ripening days; 10% spore suspension cheese decreased from 64.67% to 20.46%, and the breaking intension is over 1000 g/cm2, which is too hard for direct consumption.The results show that 20% spore suspension cheese is more suitable. Further analysis was conducted on the 20% spore suspension cheese. During ripening period, a-value increased from 0.01 to 13.32; the mold and yeast counts increased from 4.8 × 105 to 5.4× 107 CFU/g, the counts increased rapidly especially between days 3 to 6 . Scanning electron microscopy of cheese showed that microstructure of Monascus-fermented cheese packed more densely than control. Acid protease activity increased with ripening period, peaking at 224 units/mL on day 8. This is similar to previous studies. The final product content 2.875 ppm of monacolin K and 0.0535 ppm of citrinin. This study was conducted to make a Monascus-fermented cheese that can supply unique flavor and color in order to develop a special cheese with Asian taste but also with functional properties. To produce higher amount of monacolin K in Monascus-fermented cheese, we can add dry heating treatment M. purpureus NTU 301-fermented rice powder directly in the process of hooping.