Microencapsulation of Lactobacillus reuteri and its optimization

Abstract

Lactobacillus reuteri is a species of probiotics which could colonize in the human intestine, change the microflora within the gut, and produce bacteriostatic agents - reuterin. L. reuteri could supply a lot of positive benefits for human health, but they are quite sensitive and would decrease the activity and viability when exposed to harsh conditions. In order to increase the viability of L. reuteri, we took some treatments such as adding trehalose as a cryoprotectant or microencapsulation. In this study, extrusion method was applied to L. reuteri for cell microencapsulation and then to study the effects of freezing storage test, accelerated storage test, and its application to real foods. Furthermore, a three-variable and three-level design analyzed by RSM was used to study the effects of air flow rate, sodium alginate concentration, trehalose concentration on the survival of L. reuteri when coagulated with calcium chloride by two-fluid spray-coagulation, and determine the optimum conditions. Results showed that trehalose and microencapsulation techniques could improve the viability of L. reuteri. It could maintain viability in adequate range when apply to yogurt. Besides, in predicting the shelf-life of the real food, the accelerated storage test data were fitted to the Arrhenius equation. There was no significant difference between the predicted k values and the experimental k values. In organoleptic test, the microencapsulated cells whether storage or not showed no significant difference, but yogurt with or without sugar affected the acceptability. In addition, the particle size of microencapsulated L. reuteri prepared by two-fluid spray-coagulation method would be most significantly affected by the air flow rate, and the second significant factor was the concentration of sodium alginate. With the increase of air flow rate and the decrease of the sodium alginate concentration, the particle size decreased. Furthermore, it had the highest viability on the treatment of air flow rate 2 L/min, sodium alginate concentration 3% and trehalose concentration 3% In summary, adding trehalose combining with microencapsulation could improve the viability of L. reuteri effectively. Moreover, microencapsulated L. reuteri could apply to yogurt successfully.

Lactobacillus reuteri是益生菌之一種，能定殖於人體之腸道中、改變腸道內之菌相，並能夠產生抗菌物質─reuterin等，對於人體健康有多種正面之效益，但是L. reuteri相當敏感易受外界環境影響，而降低其活性甚至死滅，為了增加L. reuteri之存活率本研究利用添加海藻糖或進行微膠囊化等步驟進行處理，以擠壓法製備L. reuteri之褐藻酸鈣微膠囊並進行冷凍儲藏試驗、加速儲藏試驗、真實食品運用性等相關結果之探討，此外亦利用三因子三層階的反應曲面試驗設計，探討經二流體式噴霧凝結法製備L. reuteri微膠囊，針對以不同空氣流速、褐藻酸鈉濃度、海藻糖濃度等三種控制因子對L. reuteri之存活率與受傷程度之影響，並以此找尋最適條件且進行相關之研究與探討。結果顯示，添加海藻糖與進行微膠囊化處理皆可減緩L. reuteri菌株之死滅，將L. reuteri微膠囊運用至酸酪乳中其存活率佳，且經加速儲藏試驗，阿瑞尼斯圖成線性關係，此外真實值與預測值無顯著性差異，因此可依據此進行保存期限之推估。在品評方面，微膠囊是否經儲藏對於消費者之接受度並無顯著影響，但是否具有甜味會影響其接受程度。在以二流體式噴霧凝結法製備L. reuteri微膠囊方面，以空氣流速對微膠囊粒徑有最顯著之影響，其次為褐藻酸鈉濃度，隨著空氣流速之增加與褐藻酸鈉濃度的下降，粒徑大小也隨之減少；存活率則以空氣流速2 L/min、褐藻酸鈉濃度3％、海藻糖濃度3％所製備之微膠囊為最高。綜合上述結果，海藻糖之添加搭配微膠囊化處理可有效提升L. reuteri菌株之存活率，且L. reuteri微膠囊可成功運用於酸酪乳等真實食品上。