新疆传统乳制品中优良乳酸菌的筛选及多菌株发酵剂的研究

从新疆地区采集的46份传统乳制品中分离获得的612株乳酸菌,根据菌株来源、培养条件,形态特征、凝乳状态和产酸特性,选择其中20株乳酸菌进行生理生化鉴定和酸奶发酵试验,结果表明,分离株中3株为链球菌,4株为乳球菌,13株为乳杆菌,平均发酵产酸速率在8.11~12.43oT/h,不同菌株在酸乳冷藏期间表现出不同的后酸化活性,冷藏15d滴定酸度提高了6.3%~55.7%。不同菌株凝乳时黏度在272~1085cp,多数菌株发酵乳在冷藏期间黏度呈上升趋势,球菌的产黏能力普遍低于杆菌。气相色谱分析结果显示不同菌株发酵乳中丁二酮在3.51~68.74mg/L,乙醛在3.51~68.74mg/L,丙酮在0.87~48.35mg/L,乙酸乙酯在0~103.68mg/L,异戊醇都未检出。经过混合菌株发酵生产酸乳比较,发现以S.thermophilusX1、S.thermophilusX5、L.plantarumY5和L.delbrueckii bulgaricussubsp.Y10按1∶1∶1∶1比例组合作为发酵剂,生产的酸乳组织状态较好、风味独特、后酸化弱。

Study on Preparation of Yoghurt Starter Using Lactic Acid Bacteria from the Traditional Dairy Products of Xinjiang

In this study,612 strains of lactic acid bacteria were isolated from 46 samples of traditional dairy products of Xinjiang,China.Twenty isolates were screened according to their sources,cultural conditions,cell shapes,coagulation conditions and acid producing.The results showed that there were 3 strains of Streptococcous,4 strains of Lactoccous and 13 strains of Lactobacillus in these isolates.The average acid producing rates ranged from 8.11 to 12.43 oT/h and postacidification were varied among different strains.The titration acidity of fermented skim milk increased 6.3～55.7% after cold storage for 15 d.The viscosity of fermented skim milk at coagulation time were 272～1085 cp and for most of strains,the viscosity increased during low temperature storage.Moreover,it was found that viscosity producing ability of Lactoccous was lower than that of Lactobacillus.The results of gas chromatography analysis showed that diacetyl,acetaldehyde,acetone and ethyl acetate in fermentation products ranged between 3.51 and 68.74 mg/L,3.51 and 68.74 mg/L,0.87 and 48.35 mg/L,0 and 103.68 mg/L,respectively.One adjunct culture of S.thermophilus X1,S.thermophilus X5,L.plantarum Y5 and L.delbrueckii.subsp.bulgaricus Y10 with ratio of 1∶1∶1∶1 was found to be suitable as yogurt starter and product presented good acidity,taste and flavor.