夸克干酪用嗜温乳酸菌的生长特性及贮藏稳定性

Growth Characteristics and Store Stability of Mesophilic Lactic Acid Bacteria Used for Quark Cheese Manufacture

本实验采用比浊法研究了夸克干酪常用的乳酸链球菌、乳脂链球菌和丁二酮乳酸链球菌在MRS液体培养基和RSM(ReconstitutedSkimmedMilk)培养基中的生长特性。结果表明,在MRS培养基中,三株乳酸菌的迟滞期为0～2h,2～8h为对数生长期,8h后进入生长平稳期,此时比浊度约为1.5(OD600nm)。三株菌的增殖世代时间约为1h左右。在RSM培养基中,接种量为105CFU/ml时三株菌的生长迟滞期不明显。乳酸链球菌和乳脂链球菌培养6h后进入生长平稳期,活菌数也达到最大,分别为1.33×109CFU/ml;1.61×109CFU/ml;丁二酮乳酸链球菌培养8h后进入平稳期,活菌数达到7.75×108CFU/ml。本实验从活菌存活情况和产酸能力考察了各菌株RSM发酵剂在4℃下的贮藏稳定性。发现乳酸链球菌、乳脂链球菌在贮藏8d内基本保持稳定的活菌数及产酸能力;丁二酮乳酸链球菌在贮藏14d内活菌数保持稳定,但产酸能力5d后明显下降。

The preliminary growth characteristics of three mesophilic lactic acid bacteria (Streptococcus. lactis. subsp. Lactis,Streptococcus. lactis. subsp. Cremoris, Streptococcus. lactis. subsp. Diacetylactis) in MRS medium and defatted milk culture mediumwere studied. These lactic acid bacteria are often used in manufacture of Quark cheese. The results indicated that in the MRSmedium, the adaptation phase of the three lactic acid bacteria was 0～2h, and 2～8h was the logarithmic growth phase, and duringthe stationary phase, the turbidity of the three starter cultures was about 1.5 (OD600nm). The growth density doubling time duringthe logarithmic growth phase was around 1h. In the RSM medium, when the inoculation is 105 CFU/ml, the adaptation phase of thethree starter cultures was much shorter. The stationary phase was achieved by S. lactis and S. cremoris after incubation for 6h andthe maximum viable cell counts reach 1.33 × 109CFU/ml and 1.61 × 109CFU/ml respectively. After 8h's incubation, the S.diacetylactis reaches stationary phase and the maximum viable cell counts became 7.75×108CFU/ml. In this experiment, the storestability of the three starter cultures in the RSM medium was also studied confirming the viable cell counts and the acid producingability. The results indicated that within 8d, the viable cell counts and the acid producing ability of S. lactis and S. cremoris keptstable. For S.diacetylactis, the viable cell counts kept stable within 14d, but the acid producing ability decreased after 5d's storage.