INRA, UMR1253 Science et Technologie du Lait et de l'Œuf, 65 rue de Saint Brieuc, 35000 Rennes, France; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'Œuf, 65 rue de Saint Brieuc, 35000 Rennes, France.
Laboratoires Standa, 14000 Caen, France.
Int J Food Microbiol. 2014 Nov 17;191:60-8. doi: 10.1016/j.ijfoodmicro.2014.09.001. Epub 2014 Sep 6.
Flavor is an important sensory property of fermented food products, including cheese, and largely results from the production of aroma compounds by microorganisms. Propionibacterium freudenreichii is the most widely used species of dairy propionibacteria; it has been implicated in the production of a wide variety of aroma compounds through multiple metabolic pathways and is associated with the flavor of Swiss cheese. However, the ability of other dairy propionibacteria to produce aroma compounds has not been characterized. This study sought to elucidate the effect of interspecies and intraspecies diversity of dairy propionibacteria on the production of aroma compounds in a cheese context. A total of 76 strains of Propionibacterium freudenreichii, Propionibacterium jensenii, Propionibacterium thoenii, and Propionibacterium acidipropionici were grown for 15 days in pure culture in a rich medium derived from cheese curd. In addition, one strain each of two phylogenetically related non-dairy propionibacteria, Propionibacterium cyclohexanicum and Propionibacterium microaerophilum were included. Aroma compounds were analyzed using headspace trap-gas chromatography-mass spectrometry (GC-MS). An analysis of variance performed on GC-MS data showed that the abundance of 36 out of the 45 aroma compounds detected showed significant differences between the cultures. A principal component analysis (PCA) was performed for these 36 compounds. The first two axes of the PCA, accounting for 60% of the variability between cultures, separated P. freudenreichii strains from P. acidipropionici strains and also differentiated P. freudenreichii strains from each other. P. freudenreichii strains were associated with greater concentrations of a variety of compounds, including free fatty acids from lipolysis, ethyl esters derived from these acids, and branched-chain acids and alcohols from amino acid catabolism. P. acidipropionici strains produced less of these compounds but more sulfur-containing compounds from methionine catabolism. Meanwhile, branched-chain aldehydes and benzaldehyde were positively associated with certain strains of P. jensenii and P. thoenii. Moreover, the production of compounds with a common origin was correlated. Compound abundance varied significantly by strain, with fold changes between strains of the same species as high as in the order of 500 for a single compound. This suggests that the diversity of dairy propionibacteria can be exploited to modulate the flavor of mild cheeses.
风味是发酵食品（包括奶酪）的重要感官特性，主要源于微生物产生的香气化合物。丙酸杆菌属是乳制品丙酸杆菌中应用最广泛的物种；它通过多种代谢途径参与了多种香气化合物的产生，并与瑞士奶酪的风味有关。然而，其他乳制品丙酸杆菌产生香气化合物的能力尚未得到描述。本研究旨在阐明乳制品丙酸杆菌种间和种内多样性对奶酪环境中香气化合物产生的影响。共培养了 76 株弗氏丙酸杆菌、詹氏丙酸杆菌、谢氏丙酸杆菌和丙酸丙酸杆菌，在富含奶酪凝乳的丰富培养基中培养 15 天。此外，还包括了两种系统发育相关的非乳制品丙酸杆菌——环已烷丙酸杆菌和微需氧丙酸杆菌各一株。使用顶空捕集气相色谱-质谱法（GC-MS）分析香气化合物。对 GC-MS 数据进行方差分析表明，在所检测的 45 种香气化合物中，有 36 种的丰度存在显著差异。对这 36 种化合物进行了主成分分析（PCA）。PCA 的前两个轴，占培养物之间变异性的 60%，将弗氏丙酸杆菌菌株与丙酸丙酸杆菌菌株分开，也将弗氏丙酸杆菌菌株彼此区分开来。弗氏丙酸杆菌菌株与多种化合物的浓度较高有关，包括脂解产生的游离脂肪酸、源自这些酸的乙基酯以及来自氨基酸分解代谢的支链酸和醇。丙酸丙酸杆菌菌株产生的这些化合物较少，但来自蛋氨酸分解代谢的含硫化合物较多。同时，支链醛和苯甲醛与某些詹氏丙酸杆菌和谢氏丙酸杆菌菌株呈正相关。此外，具有共同来源的化合物的产生呈相关性。化合物丰度因菌株而异，同一物种的菌株之间的变化倍数高达 50 倍左右，这表明可以利用乳制品丙酸杆菌的多样性来调节温和奶酪的风味。
