Analysis Of Volatile Compounds In Dry Intestines And Screening And Identification

Harbin air-dried sausage is a Chinese traditional spontaneous fermented sausage, and is well received by consumers. In order to understand the compositions and sources of volatile compounds from air-dried sausage, this experiment using solid-phase microextraction and gas chromatography-mass spectrometry (SPME-GC/MS) technology to detect volatile compounds of the sausages at different times during processing and as well as the mixed spices, ginger powder and wine used in the sausage processing. And the change regulations, formation mechanisms were investigated. Then the selective medium was used to separate and purify Staphylococcus from spontaneous fermented air-dried sausage and excellent Staphylococcus were selected according to the screening criteria for meat starter culture, and the production of 3-methyl butanal strains were identified. Finally, the capability and mechanism of aroma producing by identified Staphylococcus were studied. And the effects of different parameters of fermented meat production on the growth of the identified bacterium were also researched. Results showed that:(1) In this experiment,19,20 and 30 kinds of volatile flavor compounds were identified from samples periodically taken after finished curing, sun-drying and fermenting.34 volatile compounds were identified in total during the entire process. The main volatile compounds during the processing of air-dried sausages were limonene, styrene, hexanal, ethanol, ethyl ester hexanoic acid and 2-pentanone. 3-methylbutanal were also detected and identified. The formation of these volatile compounds may be attributed to the added alcohol, spices, fat oxidation, amino acid metabolism, microbial activity and the interaction between these factors. The identified volatile compounds from mixed spices, ginger powder and wine were 49,48,12 respectively.(2) There were 44 strains of gram-positive Staphylococcus isolated from naturally fermented air-dried sausage samples, then further selection were done according to the screening criteria and the ability of 3-methylbutanal producing.2 strains of Staphylococcu named S18 and S44 were finally found. After the morphology, API Sap biochemical identification and 16S rDNA molecular biological identification, it turned out that S18 was Staphylococcus xylosus and S44 was Staphylococcus lentus.(3) In view of the Staphylococcus xylosus was commonly used as starter culture in fermented meat production, the investigation on the capability and mechanism of aroma producing by identified Staphylococcus xylosus S18 were conducted. It was found that in model systems, the speed and yield of 3-methylbutanal producing from the metabolism of leucine by Staphylococcus xylosus S18 were both higher than those from the Maillard reaction, which indicated that the 3-methylbutanal in the dried cured sausage was about mainly from contribution of microorganism. No matter whether the pyridoxal 5’-phosphate was added, the Staphylococcus xylosus S18 could produce 3-methylbutanal, thus we could conclude that Staphylococcus xylosus S18 might produce 3-methylbutanal through oxidation and aminotransferase pathway.(4) Different parameters of fermented meat production had some effects on the growth of the Staphylococcus xylosus S18. It could grow in the pH5-8 environments, the optimum pH was 7; the bacteria could also grow under 17-37℃, it grew better as temperature increasing; with the addition of 0-5% salt to medium, S18 grew well; S18 also grew in the medium containing 0-150ppm nitrite, while the nitrite concentration above 100ppm had certain inhibitory effect on the growth of Staphylococcus xylosus S18.