Abstract: L.acidophilus,L.plantarun and their mixture were inoculated into the sour soup made from chopped tomato,pepper,ginger and garlic for fermentation at 25 ℃ respectively.The volatile compounds in the three sour soups and natural fermented sour soup were extracted by means of distillation extraction method,and they were analyzed with gas chromatography and mass spectrometry technique(GC-MS).Results showed that the volatile compounds are found to be 92 kinds in the above four sour soups in number,which are 65,58,55 and 52 kinds in them respectively.These compounds consist of 9 kinds,namely alcohols(20),acids(6),esters(17),aldehydes(5),ketones(2),alkenes(29),sulfurcompounds(1),alkanes(4) and other compounds(6).The total volatiles content in the fermented sour soup by the mixture of L.acidophilus and L.plantarun is the highest,reaching 96.273%,followed by the fermented sour soup by L.acidophilus,the natural fermented sour soup and the fermented sour soup by L.plantarun in turn.However the acid contents in the four sour soups are high,which indicated that the main flavor compounds in the sour soup products are acids.

Key words: sour soup, lactic acid bacteria, volatile compounds, gas chromatography-mass spectrometry(GC-MS)