新疆伊犁地区乳制品中乳酸菌发酵和益生特性及其复合发酵方案优化

Fermentation and Probiotic Properties of Lactic Acid Bacteria Isolated from Dairy Products in Yili,Xinjiang and Optimization of Their Mixtures for Mixed-culture Fermentation

对7株实验室保存的优良乳酸菌在酸乳发酵过程中的酸化能力、产香能力以及酸乳质构进行测定,并通过抑菌、胃肠液耐受性以及抗生素敏感性等实验探究菌株的益生特性,筛选其中性能较优良的菌株进行组合复配,以获得最优的复合发酵菌株组合方案。单菌株发酵实验结果表明乳明串珠菌Leuconostoc lactis XKN1-5、乳杆菌属Lactobacillus delbrueckii subsp.bulgaricus BSTS6-4凝乳时间短(7 h左右),酸乳酸度可达96°T,酸化能力较其他菌株好;L.delbrueckii subsp.bulgaricus BSTS6-3、Streptococcus thermophilus XSXN1-2发酵制得的酸奶质构特性较好;L.delbrueckii subsp.bulgaricus BSTS6-1、S.thermophilus XSXN1-1产香性能最优,其中菌株XSXN1-1双乙酰质量浓度达到2.02 mg/L,乙醛质量浓度可达16 mg/L,能够明显改善酸奶的风味。益生实验结果表明,乳杆菌菌株Lactobacillus fermentum BST2-3、L.delbrueckii subsp.bulgaricus(BSTS6-1、BSTS6-3、BSTS6-4)能够抑制肠道致病菌的生长;L.fermentum BST2-3、L.delbrueckii subsp.bulgaricus(BSTS6-1、BSTS6-4)的黏附性较好;L.fermentum BST2-3在模拟胃肠液处理9 h后活菌数仍可达10~6 CFU/mL;且7株乳酸菌对大部分所试抗生素表现出敏感,安全性较高。最后按照产酸、产香、质构以及益生特性将菌株分类并进行酸乳复合发酵,获得复合发酵的最优菌株组合为菌株L.delbrueckii subsp.bulgaricus(BSTS6-4、BSTS6-3)、S.thermophilus XSXN1-1、L.fermentum BST2-3。

The acidification ability and aroma-producing ability of seven strains of lactic acid bacteria preserved in our laboratory for yogurt fermentation and the texture properties of yogurt made with each of the strains were measured.The probiotic characteristics of these strains were evaluated by their antibacterial properties,gastrointestinal juice tolerance and antibiotic susceptibility.Strains with better performance were selected and combined to obtain the optimal mixed starter culture.The results of single-strain fermentation showed that the coagulation time of yogurts made separately with Leuconostoc lactis XKN1-5 and Lactobacillus delbrueckii subsp.bulgaricus BSTS6-4 was shorter(about 7 h),and the acidity reached around 96°T;their acidification abilities were better than those of other strains.The yogurts fermented separately by L.delbrueckii subsp.bulgaricus BSTS6-3 and Streptococcus thermophilus XSXN1-2 had excellent texture characteristics.L.delbrueckii subsp.bulgaricus BSTS6-1 and S.thermophilus XSXN1-1 had the best aroma-producing ability and the yogurt fermented by strain XSXN1-1 contained 2.02 mg/L of diacetyl and 16 mg/L of acetaldehyde,indicating significantly improved flavor.The results of probiotic properties showed that L.fermentum BST2-3 and L.delbrueckii subsp.bulgaricus(BSTS6-1,BSTS6-3,and BSTS6-4)could inhibit the growth of pathogenic bacteria,and Lactobacillus fermentum BST2-3,L.delbrueckii subsp.bulgaricus (BSTS6-1,BSTS6-4)had greater adhesion ability;the number of viable L.fermentum BST2-3 was 106 CFU/mL after 9 h of simulated gastrointestinal juice treatment.All the seven strains showed sensitivity to most tested antibiotics and were of high safety.Based on the ability to produce acids and aroma compounds,yogurt texture and probiotic properties,the optimal strain combination for mixed-culture fermentation was obtained as L.delbrueckii subsp.bulgaricus(BSTS6-4 and BSTS6-3)+S.thermophilus XSXN1-1+L.fermentum BST2-3.