| 摘要: | 共軛亞麻油酸(CLA)具多種健康功能，而乳酸菌能促進亞麻油酸轉變成CLA，不過以乳酸菌生產CLA之產量低，因此如何提升CLA產量為當前研究趨勢。本研究以褐藻酸鈉、聚丙烯醯胺、幾丁聚醣與鹿角菜膠固定化Lactobacillus helveticus (BCRC 14030)，在pH 5、6、7與8下進行CLA生成反應，以探討不同凝膠與反應pH值對促進此一菌酛生成CLA之影響，及其應用於生產富含CLA發酵乳之可行性。
經活化之L. helveticus分別以褐藻酸鈉、聚丙烯醯胺、幾丁聚醣與鹿角菜膠固定後，取20 g與0.065 g BSA及0.1ml亞麻油酸(LA)於37 ℃下反應120小時，以生產CLA；再以不同比例褐藻酸鈉與鹿角菜膠固定化發酵乳菌酛（YC380）與不同比例褐藻酸鈉與鹿角菜膠固定化發酵乳菌酛添加2 %L. helveticus（BCRC 14030）各置入43 ℃培養至pH值4.3後生成發酵乳，其後以HPLC定量CLA，並取經10 %鹿角菜膠、10 %褐藻酸鈉固定化、5 %未固定化發酵乳菌酛生產之發酵乳與市售發酵乳做Hunter L，a，b值測定，就外觀、氣味、口味、濃稠度與總接受度，進行官能品評試驗。
結果發現：褐藻酸鈉固定化L. helveticus在pH 7下之總CLA生成量為584.80 μg，顯著地（p<0.05）比其它pH處理組及未固定化菌酛組為高；聚丙烯醯胺固定化L. helveticus在pH 6下之總CLA生成量為382.66 μg，顯著地（p<0.05）比pH 5與8處理組為高；幾丁聚醣固定化L. helveticus在pH 8下之總CLA生成量為23.70 μg，顯著地（p<0.05）比其它pH處理組為高；鹿角菜膠固定化L. helveticus在pH 6下之總CLA生成量為71.56 μg，顯著地（p<0.05）比pH5與8處理組及未固定化菌酛組為高。褐藻酸鈉與鹿角菜膠固定化發酵乳菌酛，與褐藻酸鈉與鹿角菜膠固定化發酵乳菌酛添加2 %L. helveticus（BCRC 14030）下之總CLA生成量皆顯著（p<0.05）比未固定化菌酛為高；Hunter測定中L值與a值皆以市售發酵乳顯著（p<0.05）比其他處理組為高、b值顯著（p<0.05）比其他處理組為低；而官能品評試驗中所有處理組之整體接受度大致相似。
本研究顯示經固定化之菌酛確能促進CLA生成，而四種不同凝膠固定化後，褐藻酸鈉固定化L. helveticus在pH 7下之總CLA生成量最高為584.80 μg，Hunter L，a，b值測定結果以市售發酵乳之L值與a值最高，b值最低（p<0.05），而官能品評試驗中所有處理組之整體接受度大致相似。
Conjugated linoleic acid (CLA) has many bioactivities related to the health, and linoleic acid can be promoted to convert into CLA by lactic acid bacteria. Lactic acid bacteria were observed to be capable of converting linoleic acid (LA) into CLA. However the yield was low. It is important to study how to improve the yield of CLA. Therefore, the research was performed using alginate, polyacrylamide, chitosan and carrageenan immobilized L. helveticus (BCRC14030) to convert LA into CLA at pH 5, 6, 7 and 8 in order to evaluate the effect of different gels and pH on CLA yield and the feasibility to produce CLA-rich fermented milk.
We used alginate, polyacrylamide and chitosan to immobilize L. helveticus after activation, and mixed 20 g of immobilized cell, 0.065 g of BSA and 0.01 ml of linoleic acid (LA) together for 120 hours at 37 ℃ to produce CLA; then use different ratios of alginate and carrageenan immobilized yogurt bacteria (YC380) with 2 % of L. helveticus (BCRC 14030) to make fermented milk. Then we measured CLA content by HPLC and Hunter L, a, b value then sensory evaluation with appearance, smell, taste, thickness and total acceptability ratings were also determined.
The results showed that when pH of alginate L. helveticus is 7, total CLA yield (584.80 μg) was significantly (p>0.05) higher than other pH and free cell groups. When pH of polyacrylamide immobilized is 6, total CLA yield (382.66 μg) was significantly (p>0.05) higher than other groups that pH are 5 and 8; when pH of chitosan immobilized L. helveticus is 8, total CLA yield (23.70 μg) was significantly (p>0.05) higher than other pH groups; when pH of carrageenan immobilized L. helveticus is 6, total CLA yield (71.56 μg) was significantly (p>0.05) higher than other pH groups that pH5, 8 and groups of free cell. When alginate and carrageenan immobilized yogurt bacteria and 2 % L. helveticus (BCRC 14030), total CLA yield was significantly (p>0.05) higher than other free cell; in Hunter L, a value, commercial yogurt products were significantly (p>0.05) higher than other groups, b value were significantly (p>0.05) lower than other groups, the acceptability ratings in sensory evaluation are almost the same.
The results showed that immobilization can improve the yield of CLA, and cells immobilized by 4 kinds of gel, and when pH of alginate immobilized L. helveticus is 7, total CLA yield is 584.80 μg. In HUNTER L, a and b values of commercial yogurt products, a value was the highest, b value was the lowest (p>0.05), and in sensory evaluation, the acceptability ratings of all groups are almost the same. |
