應用最適化方法開發機能性發酵乳油

Abstract

本試驗之目的在探討乳油經β-環狀糊精(β-cyclodextrin, β-CD)處理及益生菌發酵對膽固醇及共軛亞麻仁油酸(conjugated linoleic acid, CLA）含量之影響，擬開發出具有幫助消化、預防癌症、心血管疾病和體重控制等保健功能之新機能性乳油製品。試驗中將乳油(18％乳脂），先以不同濃度(0、5及10％) β-CD於40℃以1200rpm攪拌混合移除膽固醇，添加益菌質再藉由經篩選可產生CLA之益生菌Lactococcus lactis IO-1 (Lc. lactis IO-1)於37℃發酵24小時，分別於0、12及24小時取樣分析益生菌數及CLA增加量，試驗以Box and Behnken(1960)之三因子三階次之實驗設計建立最適方程式後，再經序列二次規劃法(sequential quadratic programming, SQP)，尋求低膽固醇、益生菌數及CLA增加量之機能性發酵乳油。結果顯示，菌元在乳油中培養24小時菌數可達8.6 log CFU/mL進入定常期（stationary phase），pH值及酸度分別為5.1和0.45%，隨菌數增加CLA增加量提高，於發酵24小時產量達高峰(增加59%)。β-CD雖可移除膽固醇(移除率80%)，但會顯著影響菌元生長，進而影響CLA增加量。經SQP運算後所得之最適生產條件，β-CD、果寡糖和異麥芽寡糖分別為10%、3%和0%發酵24小時，但由於β-CD對於菌元生長和CLA產量有抑制之影響，故再單獨以益生菌生長速率和CLA增加量兩反應方程式經由SQP以作運算所得之最適生產條件為β-CD、果寡糖和異麥芽寡糖分別為0%、3%和2.57%，可製成機能性發酵乳油。貯存試驗顯示機能性發酵乳油貯存一個月後，Lc. lactis IO-1菌數仍保有107 CFU/mL以上，若是以外觀來說兩周為最佳保存期限。

Conjugated linoleic acids (CLA) are a mixture of octadecadienoic acids that have been recently recognized as anticarcinogens. A high level of cholesterol in the blood, hypercholesterolemia, is a major risk factor for coronary heart disease. The purpose of this research was to develop a new functional fermented cream with high level of CLA and low level of cholesterol using optimization techniques. Different concentrations of β-cyclodextrin (β-CD; 0, 5, 10%) were blended with cream (18% fat) at 40℃ under 1200 rpm to reduce the cholesterol level, and then the samples were fermented with Lactococcus lactis IO-1 (Lc. lactis IO-1) at 37℃ for 24hr. The concentrations of CLA were determined every 12hr. Moreover, the proportion of the prebiotics and β-CD was optimized using response surface methodology (RSM) to first construct a surface model, with sequential quadratic programming (SQP) subsequently adopted to optimize the model. Results indicated that the CLA levels were increased as the number of Lc. lactis IO-1 increased, and that addition of 10% β-CD in cream with 80% cholesterol reduction showed the best outcome. Furthermore, the Lc. lactis IO-1 fermentation also reduced the cholesterol concentration. This decholesterol phenomena might be explained by the enzyme activity of Lc. lactis IO-1. Optimization results demonstrated that cream blended with 10% β-CD and mixed with 3% fructooligosaccharides (FOS) would produce a new functional fermented cream with the highest CLA and the lowest cholesterol. The verification experiment yielded a result close to the predicted values, with no significant difference (P>0.05). The storage results showed that addition of prebiotics in the sample provided protection for the active organisms. These Lc. lactis IO-1 counts remained at 107 CFU/g for samples stored for one month.