Morales Pilar, Feliu Isabel, Fernández-García Estrella, Nuñez Manuel
Departamento de Tecnología de Alimentos, INIA, Carretera de La Coruña Km 7, Madrid, 28040 Spain.
J Food Prot. 2004 Mar;67(3):567-73. doi: 10.4315/0362-028x-67.3.567.
The formation of volatile compounds in fresh cheese by 10 Enterobacteriaceae strains of dairy origin (4 Hafnia alvei, 2 Serratia liquefaciens, 1 Enterobacter cloacae, 1 Enterobacter sakazakii, and 2 Escherichia coli strains) was investigated. Small cheeses were made from pasteurized cow's milk separately inoculated with 1-3 x 10(3) CFU/ml of each of the Enterobacteriaceae strains, with glucono-8-lactone added to achieve a pH value of 5.2 in the curds. All strains reached counts close to 10(8) CFU/g in 1-day-old cheeses and survived well from day 1 to day 8. Cheeses were analyzed for volatile compounds by gas chromatography-mass spectroscopy, after extraction by dynamic headspace using a purge and trap apparatus. Sixty-one volatile compounds were determined in cheeses, 31 of which were further investigated. Significant increases of aldehydes, sulfur compounds, and aromatic compounds were recorded from 2-h curd to 1-day-old cheese, and of ketones, alcohols, and acids from 2-h curd to 8-day-old cheese. Acetaldehyde, 2-methyl propanal, and 3-methyl butanal predominated among aldehydes; 2,3-butanedione, 2,3-pentanedione, and 3-hydroxy 2-butanone among ketones; ethanol, 2-methyl propanol, and 3-methyl butanol among alcohols; and ethyl acetate among esters. Hierarchical cluster analysis of strains using the data of 31 volatile compounds separated clearly the strain of E. sakazakii, which produced high amounts of volatile compounds, from the other Enterobacteriaceae strains.
研究了10株源自乳制品的肠杆菌科菌株（4株蜂房哈夫尼亚菌、2株液化沙雷氏菌、1株阴沟肠杆菌、1株阪崎肠杆菌和2株大肠杆菌）在新鲜奶酪中挥发性化合物的形成情况。用巴氏杀菌牛奶制作小奶酪，分别接种1- 1 - 3×10³CFU/ml的每种肠杆菌科菌株，并添加葡萄糖酸 - δ - 内酯以使凝乳的pH值达到5.2。所有菌株在1日龄奶酪中的数量均接近10⁸CFU/g，并且从第1天到第8天存活良好。使用吹扫捕集装置通过动态顶空萃取后，用气相色谱 - 质谱联用仪分析奶酪中的挥发性化合物。在奶酪中测定了61种挥发性化合物，其中31种进行了进一步研究。从2小时凝乳到1日龄奶酪，醛类、含硫化合物和芳香族化合物显著增加；从2小时凝乳到8日龄奶酪，酮类、醇类和酸类显著增加。醛类中乙醛、2 - 甲基丙醛和3 - 甲基丁醛占主导；酮类中2,3 - 丁二酮、2,3 - 戊二酮和3 - 羟基 - 2 - 丁酮占主导；醇类中乙醇、2 - 甲基丙醇和3 - 甲基丁醇占主导；酯类中乙酸乙酯占主导。利用31种挥发性化合物的数据对菌株进行层次聚类分析，清楚地将产生大量挥发性化合物的阪崎肠杆菌菌株与其他肠杆菌科菌株区分开来。
