| Fermented sausage refers to a kind of meat which has stable microorganism characteristics and fermented flavor. Mince meat and animal fat with salt, sugar, starter and spices are mixed and poured into casings. Fermented sausage is formed through microbial fermentation. It has a long history and is the representative of traditional fermented meat products. For its high nutritional value, unique taste, room temperature preservation, convenient to eat and health functions, it is deeply liked by consumers.Nitrite is commonly used in meat processing as color agent and preservative. It not only helps the formation of characteristic bacon red, but also the promotion of flavor, inhibiting rancidity and harmful microorganism especially clostridium botulinum's growth and toxin production, thereby prolonging the shelf life of meat products. At present, in order to retent color, antibacteria and promote the flavor, the traditional method that is adding nitrate or nitrite into cured sausage is still used in the processing of sausage production at home and abroad. Although nitrite residues have a certain limit, it is still harmful to human if eating too much.In this thesis, we screened nitric oxide producing and excellent fermentation characteristics having lactic acid bacteria from traditional fermented food sour meat. Then, we inoculated the bacteria into sausage in order to retent color as an alternative to nitrite and reduce the amount of nitrite in fermented sausages. This thesis provided a theoretical and experimental basis for the purpose of lactic acid bacteria used in meat products as an alternative to nitrite in the future. The main results were as follows:1. Isolation and screening of lactic acid bacteria from sour meat43 strains of lactic acid bacteria were isolated from 4 different sour meat sampled from villages of miao and Dong in Jianhe, Guizhou province. NO producing capability of the strains was detected by the method of myoglobin plate. As a result,23 strains could produce NO. KatA gene of the 23 strains was detected by the method of colony morphology and PCR. The result showed that 11 strains of them possessed katA gene. Then, the main fermentation characteristics of the 11 strains were studied. Finally.2 strains having excellent fermentation characteristics which could produce NO, possess katA gene, produce acid quickly, tolerate salt and nitrite were screened.2. Identification of NO producing strains and the main characteristics measurementBased on the characteristics of morphology,16S rDNA sequence analysis and the phylogenetic tree constructed with MEGA3.1, the 2 strains were identified as Weissella hellenica.24h growth curve and pH curves of the 2 strains were determined. The results indicated that the 2 strains growed fast, produced acid quickly and had excellent characteristics. Protein and fat degradation activity tests showed that strain 1501 and 1509 did not have protein and fat degradation activity consisting with the screening criteria of meat starter.3. Influences of NO producing strains on fermented sausage for color retentionThe influences of strain 1501 as well as strain 1501 together with monascus pigment on fermented sausage for color retention were studied by setting different batches andâ–³E as response value. The results indicated that fermented sausages adding 40mg/kg NaNO2, 107CFU/g of lactic acid bacteria and adding 120mg/kg monascus pigment,107CFU/g of lactic acid bacteria were closely similar to those adding 80mg/kg NaNO2 in color.Physiochemical and microbiological indexes of fermented sausages such as pH, moisture, lactic acid bacteria, total bacteria, acid value, peroxide value were studied and sensory indexes were also evaluated. The results showed that lactic acid bacteria were the predominant bacteria in fermented sausage and dominated the entire fermentation and maturation process. Adding lactic acid bacteria to a certain extent helped to reduce the nitrite residual and improve the sensory quality of the final product. |
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