为筛选风味优良的发酵剂菌株。该实验在前期研究的基础上,以具有良好风味的德氏乳杆菌保加利亚亚种和嗜热链球菌为实验菌株,进行复配发酵,采用固相微萃取-气相色谱-质谱(solid phase microextraction and gas chromatography-mass spectrometry,SPME-GC-MS)等方法对复配发酵乳香气成分进行检测分析。SPME-GC-MS分析结果表明,对照菌株JD和6组复配发酵乳中共检测出116种挥发性风味物质,其中有酸类化合物(17种)、醛类化合物(11种)、酮类化合物(17种)、醇类化合物(15种)、酯类化合物(11种)、烷烃类(30种)、含氮化合物(15种)。气味活度值(odor activity values,OAV)结果表明发酵乳中关键性风味物质(OAV≥1)有6种,包括3-甲基丁醛、苯甲醛、正壬醛、双乙酰、乙偶姻和2-壬酮。而其他化合物,如辛酸、乙醛、3-羟基丁醛、庚醛、癸醛和2-庚酮等对发酵乳的整体风味起修饰作用(0.1≤OAV＜1)。其中,这些关键性风味物质在样品中浓度较高,赋予发酵乳优良风味。主成分分析及线性判别分析结果表明,A6复配组有良好产香特性,在发酵过程中产生的风味和酸类化合物、酮类化合物、醇类化合物、含氮类化合物、烷烃类化合物等呈正相关。
To evaluate the potential of superior flavor production by starter strains in fermented milk, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were used in combination as experimental strains for fermentation. Solid phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS) were used to analyze the aroma profile in the commercial starter JD and the consortium fermented milk. The SPME-GC-MS results showed that a total of 116 volatile flavor compounds were identified in the fermented milk. The identified compounds were constituted of 17 acids, 11 aldehyde, 17 ketones, 15 alcohols, 11 esters, 30 alkanes, and 15 nitrogen compounds. The results of odor activity values (OAV) indicated that 6 kinds of key flavor compounds (OAV≥1) were found in the fermented milk, including 3-methylbutyraldehyde, benzaldehyde, n-nonanal, diacetyl, acetoin, and 2-nonanone. Moreover, other compounds such as caprylic acid, acetaldehyde, 3-hydroxybutyraldehyde, heptaldehyde, decanal, and 2-heptanone played a modificatory role in the overall flavor of the fermented milk (0.1≤OAV＜1). These compounds had significant higher concentration, which conferred a superior flavor to the fermented milk. Principal component analysis and linear discriminant analysis revealed that A6 compound group had good aroma-producing characteristics. During fermentation, flavor was positively related to acid compounds, ketone compounds, alcohol compounds, nitrogen compounds and alkanes.
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