乳酸菌培养物的生长特性及其对豆奶质构和风味的影响

Survivability and Growth Effects of Three Lactobacillus Cultures on Texture and Flavor Aspects of Soymilk

摘要:

研究了Lactobacillus casei (LC), Lactobacillus helveticus (LH) and Lactobacillus rahmnosus (Lactobacillus casei subsp. rahmnosus 6013) (LR)生长特性及其对大豆奶酪风味的影响。研究表明，经过6 h的发酵，LC、LH和LR的菌落数分别增长至8.74、7.69和8.69 log (CFU/mL)；37 ℃时，分别接种LC、LH、LR和添加有Glucono-δ-内酯（GDL）的大豆牛奶都明显出现可滴定酸度增加、pH减少的现象。这三种乳酸菌都能够利用大豆糖源。经质构分析发现，菌种可引起大豆牛奶质构发生变化，其凝乳的能力可与GDL媲美。菌种通过产酶、产酸而水解大豆蛋白，从而导致质构变化形成凝乳。这些菌种可释放18种游离氨基酸（FAA），其中包括可作为奶酪风味物质前体化合物的天门冬氨酸、异亮氨酸、亮氨酸、蛋氨酸、苯丙氨酸和缬氨酸。这些菌种均能利用大豆脂肪酸（FA），而在大豆凝乳中出现某些FA消失的现象表明所选的菌种还能分别完全消耗特定的FA。可见，这三种乳酸菌在大豆牛奶中可引起质感及风味前体物的变化，正是生产大豆奶酪所必需的效果，故选择它们作为制备大豆奶酪的适用菌种。

Abstract:

Survivability and growth effects of three lactic acid bacteria, Lactobacillus casei (LC), Lactobacillus helveticus (LH) and Lactobacillus rahmnosus (Lactobacillus casei subsp. rahmnosus 6013) (LR) were studied in soymilk to determine their suitability for soy cheese production. After six hours of fermentation, viable count of LC, LH and LR increased to 8.74, 7.69 and 8.69 log (CFU/mL), respectively. LC, LH, LR and Glucono-δ-lactone (GDL, a commercial coagulant) showed significant increase in Titratable acidity and pH decrease in soymilk at 37 ℃. All the three Lactobacillus cultures were able to utilize soy sugars. The ability of the cultures to cause textural changes in soymilk, analyzed by Texture Analyser, was found competitive to GDL. Enzymes and acid produced by the cultures hydrolyzed soy protein to cause textural changes resulting into curd formation. HPLC analysis showed that all three cultures have the ability to produce and metabolize 18 free amino acids (FAA) including Asp, Ile, Leu, Met, Phe, Tyr and Val which are known as precursors of cheese flavoring compounds. GC-FID analysis for fatty acids (FA) indicated that all the cultures were capable of utilizing soy fatty acids and disappearance of some FA indicated their complete consumption by respective cultures in the resultant soy curd. All the three cultures were found to be suitable to cause textural and flavor precursor changes in soymilk required for soy cheese production.