LI Ting, TIAN Jiale, LIU Yang, LI Jiawen, QIAO Shaoting, DAN Tong, SUN Tiansong
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.