應用最適化方法開發具隔熱性益生菌微膠囊

Abstract

本研究目的擬藉由最適化技術開發具隔熱效果之益生菌微膠囊，以改善益生菌在高溫環境、模擬腸胃液及儲存期間的存活率。研究中選用結蘭膠及褐藻酸鈉兩種食用膠，以不同比例混合成膠作為囊壁材質包覆益生菌Lactobacillus casei及Bifidobacterium bifidum作為菌元，並在囊壁中多添加短鏈肽類與果寡醣等益菌質，探討添加不同益菌質濃度及膠體比例之微膠囊化益生菌，經高溫短時間加熱(75℃，一分鐘)處理後其存活菌數。試驗中以反應曲面法(response surface methodology, RSM)之四因子三階次實驗設計得到30組之實驗組，實驗結果以Design-Expert軟體分析，建立反應曲面模式及最適方程式後，再利用序列二次規劃法(sequential quadratic programming, SQP)尋找出隔熱性最佳之微膠囊囊壁組合。 結果顯示，若欲同時考慮兩種益生菌在最適的條件下，因設定目標較多而複雜，複合函數在序列二次規劃法之運算下，經過68次隨機找尋起始點開始運算，發現搜尋到三個不同的區域性最佳解，在反覆採用隨機選取起始點搜尋的過程中，則會因為其中一個最佳解出現機率達99.99 %的條件限定下才停止搜尋；尋得最適結果之各成分添加濃度，分別為1.0 %結蘭膠、2.0 %褐藻酸鈉、0.82 %肽類且不需要添加果寡醣；在此條件下，包覆後所釋放的乳酸桿菌及雙叉乳桿菌菌數分別可達到7.8 log CFU/g及7.3 log CFU/g，而包覆再經加熱處理後的殘存菌數則分別為7.4 log CFU/g及7.4 log CFU/g，其預估的存活率分別高達95.87 %以及100 %。將上述藉由序列二次規劃法所推薦的最佳解經由實際實驗驗證，發現實驗目標之理論值與實際值之間均不具顯著性的差異(p>0.05)，這樣的結果亦即代表所建立的目標函數模式是可以信賴的，有達到最佳化的效果。 將最適化推薦組經儲存後，測試其儲存期間的菌數變化，以及儲存後再經由加熱與模擬腸胃液處理，測試其存活菌數。經儲存試驗後發現，若添加結蘭膠與褐藻膠混合作為囊壁材質，可提高加熱及模擬腸胃液處理後的殘活菌數；而在囊壁材質中多添加益菌質亦能在儲存後期保提供菌體足夠的營養來源，故經過一個月的儲存後，菌數仍能維持在106-107 CFU/g。

Many studies have shown low viability of probiotics in dairy products due to acidity, the presence of hydrogen peroxide, and the oxygen content. In addition, heat treatments during food processing also hamper the application of probiotics. Encapsulation, which has been investigated for improving the viability of microorganisms in both dairy products and the intestinal tract, might provide the solution. Thus, the purpose of this research was to encapsulate probiotics using insulating material and modern optimization techniques to determine optimal processing conditions, performance and survival rates under heat treatments, simulated gastrointestinal conditions and storage. Prebiotics (fructooligosaccharides), growth promoter (peptide) and gums (sodium alginate and gellan gum) were incorporated as coating materials to microencapsulate two probiotics (Lactobacillus casei and Bifidobacterium bifidum). The proportion of the prebiotics, peptide and gums was optimized using response surface methodology (RSM) to first construct a surface model, with sequential quadratic programming (SQP) subsequently adopted to optimize the model and evaluate the survival of microencapsulated probiotics under heat treatment (HT). Optimization results indicated that after 68 sets of randomly generated initial points leading to optimal composite function (CF) values (local optima) ranging from 7.35 to 7.48, the global optimal CF was found to be 7.48 (99.99% certainty). The global optimal CF values corresponded to: 7.8 log CFU/g for survival of L. casei before HT; 7.3 log CFU/g for survival of B. bifidum before HT; 7.4 log CFU/g for survival of L. casei after HT and 7.4 log CFU/g for survival of B. bifidum after HT. The optimal combination of coating materials for probiotic microcapsules was 2.0% sodium alginate mixed with 1.0% gellan gum and 0.82% peptide as coating materials would produce the highest survival in terms of probiotic count. The verification experiment yielded a result close to the predicted values, with no significant difference (P>0.05). The storage results also demonstrated that incorporation of gallen gum with alginate significantly improved the viabilities of probiotics during HT and SGFT. Furthermore, addition of prebiotics in the wall materials of probiotic microcapsules provided superior shield for the active organisms. These probiotic counts remained at 106-107 CFU/g for microcapsules stored for one month and then treated in HT and SGFT.