| Beef jerky, as one of popular foods in China, has been consumed for a long time, but the main defect of this product was hard in the structure. Fermented beef jerky is one of meat products fermented mainly with lactic acid bacteria and other microorganisms. This leads to special flavour, better quality, more nutrition and longer shelf-life. The purposes of this study were to produce beef jerky by commercial meat starters, investigate the fermentation process and drying process of beef jerky. Muscle fiber microstructure, free amino acid and flavor components were also investigated before and after fermentation.Three commercial starter cultures were applied and compared in beef fermentation, and the starter culture T-SPX(Staphylococcus xylosus and Pediococcus pentosaceus) was adopted. The lactic acid bacteria and the staphylococcus can grow to 10~6cfu/g, 10~7cfu/g respectively, pH was between 5. 0-5. 3, the fermented product had a soft sour taste and a special thick fermented flavor. The optimum technology parameters were investigated by Box-Behnken design and response surface methodology analysis. The result showed that the optimum fermented conditions were as follows: fermented at 14℃for 70h with common salt addition 1. 7% and glucose addition 1. 25%.According to the sensory evaluation, the beef jerky with about 35% moisture was the best product. Based to the change of moisture content under 50℃, 60℃and 70℃condition and the change in color, texture, a phase drying process, 50℃for 1h, 55℃for 1h, 60℃for 1h, and then 250℃for 3-4min, can not only rapidly reduce the moisture content and water activity, but also sterilize and cook the beef, with roasting aroma.The microstructure of raw beef, cured beef and fermented beef was studied by scanning electron microscope. The microstructure of beef was deeply changed after fermentation, and the diameter of muscle fibre was reduced, surface was roughened, and the arrange was loosened, the muscle fibre was severely ruptured, turn into lots of fractionlets.The free amino acids in the beef jerky were analysed by Automatic Amino Acid Analyzer before and after fermentation. The results showed that all kinds of FAA and total FAA were increased. It is seemed that the staphylococcus in starter culture could enhance the proteolysis.The volatile flavor compounds of unfermented and fermented beef were analysed by GC-MS. After fermentation, the kinds of volatile flavor compounds were increased from 28 to 38, among them, alcohols increased 4 kinds, aldehydes increased 2 kinds, acids increased 2 kinds, ketones increased 1 kind and aromatic compounds increased 6 kinds, and the total quality of volatile flavor compounds was increased from 24. 59μg/g to 56. 59μg/g. Therefore the fermentation can enhance the flavor of beef jerky.The fermented beef jerky was stored at the room temperature for 90 days, the color, texture on the whole remained the same, pH maintained 5. 10-5. 15, total bacteria counts maintained <1000cfu/g, no mould and yeast grew, no harmful strain grew, therefore the product has good storage stability. |
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