乳酸發酵豆漿之試製與品質特性探討

Abstract

乳酸菌屬於益生菌群，為腸道菌相之一環，具有平衡菌相、預防高血壓、降低膽固醇、調節免疫系統、抗氧化衰老等保健功效，在改善生理機能、促進人體健康方面扮演重要角色。研究證實，傳統的乳酸菌發酵方法為有效的保健食品製造方式，可保留乳酸菌及其產物之活性，經人體攝食後發揮益生功效。 傳統乳酸菌發酵食品以動物性乳源為常用發酵基質，此方式所製成之發酵乳品雖具備高應用價值，卻有引發乳醣不耐症等若干限制；相關研究積極尋找適宜乳酸菌生長之乳品替代物，已獲致相當成果，其中由黃豆加工製成之豆漿因營養價值高且不含乳醣及膽固醇，格外受到矚目。 本研究選擇市售不同製程之豆漿以及不同來源分離之乳酸菌種，測試菌種及基質差異對發酵效率的影響，並針對發酵產物之生化特性進行分析。實驗顯示現磨豆漿與罐裝豆漿相較，前者為較好的乳酸菌發酵基質，額外添加醣類可增加乳酸菌增殖速率。適宜乳源發酵之菌種，如本研究所測試之Lactobacillus rhamnosus GG，於豆漿中之發酵效率較佳；於基質中添加醣類時，發酵產物可達到接近市售乳酸飲品之pH值標準及乳酸含量，且發酵液經自由基清除能力測定後，具備相當之抗氧化潛力。此研究結果可供後續試製乳酸菌發酵豆漿飲品時發酵條件設定之參考。

As a group of probiotics, lactic acid bacteria (LAB) are prominent members of the microbial community in the gastrointestinal tract. Research shows that LAB beneficially affect the physiological functions of their host through various mechanisms, such as maintaining microbial balance, lowering blood pressure, lowering blood cholesterol level, immunostimulation and antioxidative effect. Lactic acid fermentation has been utilized as a traditional method for food production for thousands of years, and it is scientifically proven to be able to preserve the viability and functionality of LAB and their products; therefore, it can be used with modifications as a feasible method of functional food manufacture. Dairy products such as bovine milk are traditionally used as the matrix for fermentative food production. Although the process has been thoroughly studied and a spectrum of products is available to consumers, there are still limitations of applicability, such as the onset of lactose intolerance. A wide variety of traditional foods again provide a number of possible candidates for milk replacement; among them is soymilk, the water extract of soybeans, whose high nutritional value and zero lactose/cholesterol content have been met with great expectations. In this study, commercially available soymilk products of alternative manufacturing processes were used as fermentative matrices, and lactic acid bacteria species of various origins were inoculated as starters; the efficiency of fermentation was measured, and biochemical properties of fermentative products were analyzed. Freshly-prepared soymilk serves as a better fermentative environment for LAB compared to off-the-shelf products, and extra carbohydrate supplements increased the growth rate of probiotics. LAB species traditionally used in milk fermentation, such as Lactobacillus rhamnosus GG in this study, performed much better than species isolated from other sources, and the pH value and lactic acid content of the end product can reach the level of commercial products with added sugar supplement. The fermented soymilk possessed considerable free radical scavenging capability, which indicated an improvement of antioxidative ability. Results of this study can serve as a reference for upcoming research concerning the development of functional fermentative soymilk products.