應用序列二次規劃法開發富含左旋肉生僉機能性發酵乳

Abstract

本試驗的目的在探討脫脂還原乳添加益菌質（果寡醣和異麥芽寡醣）、乳清濃縮蛋白粉及益生菌（Lactococcus lactis subsp. cremoris, Lc. lactis subsp. lactis, Lactobacillus rhamnosus），於37 ℃發酵7小時後，對產品中左旋肉生僉含量與乳酸菌數的影響。藉著反應曲面法建立數學模式，配合序列二次規劃法的最佳化搜尋，找出機能性發酵乳的最佳配方。擬開發出一種含有益生菌與益菌質，且富含左旋肉生僉的新健康食品，使產品能商品化，增加乳製品多樣性，提供國人新選擇。 試驗中以果寡醣、異麥芽寡醣及乳清濃縮蛋白粉的添加濃度為變因，而以機能性發酵乳發酵7小時完成時的左旋肉生僉含量與乳酸菌數為反應性狀，以反應曲面法中Box and Behnken的三因子三階次試驗設計，共得17個實驗組，實驗結果以Design-Expert軟體建立最適方程式，再經由序列二次規劃法尋求果寡醣、異麥芽寡醣及乳清濃縮蛋白粉的最佳添加比例。 結果顯示添加益菌質可提高發酵乳中左旋肉生僉含量，其中又以果寡醣添加1.0 %、異麥芽寡醣3.0 %及不添加乳清濃縮蛋白粉，進行發酵7小時製成的機能性發酵乳有最佳左旋肉生僉含量與乳酸菌數。以此最佳配方製成的機能性發酵乳進行成分分析、官能品評試驗及儲存試驗。 機能性發酵乳的基本組成為水分87.36 %、蛋白質3.59 %、脂肪0.08 %、碳水化合物8.24 %、灰分0.73 %、pH值6.34及滴定酸度0.23 %。官能品評試驗是比較機能性發酵乳、市售發酵優酪乳及未發酵脫脂還原乳的質地、外觀、氣味及口感，結果顯示市售發酵優酪乳整體評分最佳，但機能性發酵乳是以脫脂還原乳為基質，僅添加對人體有益的乳酸菌與益菌質（果寡醣與異麥芽寡醣），無添加糖與安定劑等任何添加物，具有淡淡乳粉味與乳白帶微黃色的外觀，飲用口感有些微甘甜味，倘要上市成為架上產品，須在各項官能品評項目上作改進，使其更具市場競爭力。儲存試驗於機能性發酵乳剛製成時有最佳左旋肉生僉含量22.08 ± 1.36 mg/100 g sample；乳酸菌數於剛製成時有7.6 ± 0.0 log CFU/mL，會隨儲存時間先增加再減少，且經過4℃儲存1個月後，乳酸菌數仍保有107 CFU/mL以上。而在儲存期間測得的總生菌數與乳酸菌數相近，且大腸桿菌群檢驗呈現陰性，顯示機能性發酵乳於儲存期間無其他微生物污染繁殖。另外，在儲存期間pH值逐漸下降，而滴定酸度則漸次增加。當儲存2~3週可直接觀察外觀變化，開始有乳清分離與些許酸臭味，故2週內為最佳保存期限。

The objective of this research was to create a new synbiotic fermented milk with high L-carnitine and healthy benefits. The final aim was to increase the variety and choice of dairy products. In this study, skim milk was mixed with prebiotics (fructooligosaccharides, FOS and isomaltooligosaccharides, IMO) and whey protein concentrate. The mixture was then inoculated with probiotics (Lc. lactis subsp. cremoris, Lc. lactis subsp. lactis, and Lb. rhamnosus) and fermented at 37 ℃ for 7 hr. Moreover, the proportion of the prebiotics and whey protein concentrate was optimized using response surface methodology (RSM) to construct a surface model, with sequential quadratic programming (SQP) subsequently adopted to optimize the model and the processing conditions. Optimization results demonstrated that addition of prebiotics increased the level of L-carnitine and lactic acid bacteria (LAB) counts in fermented milk with 1.0 % FOS and 3 % IMO. The verification experiment yielded a result close to the predicted values, with no significant difference（P＞0.05）. The components of the functional fermented milk were 87.36 % moisture, 3.59 % CP, 0.08 % fat, 8.24 % carbohydrate and 0.73% ash. And the pH value and titratable acidity was 6.34 and 0.23%, respectively. Although the sensory evaluation results indicated that the consumers, giving a score above 6.0, could accept this product, additional sweeteners and flavors might be needed for possible commercialization of this product. The storage results showed that LAB counts remained above 107 CFU/mL for samples stored for one month. On contrast, L-carnitine contents dropped during storage. And the standard plate counts were very close to LAB counts with no coliform bacteria, it indicated that there were no other microorganisms grew in the functional fermented milk during storage. Because the post acidification happened during storage, pH value dropped and titratable acidity increased.