Screening Of Lactic Acid Bacteria For Fermented Loin Ham And Development Of Direct-vat-set Starter

Fermented meat products are one of the traditional fermented foods in China,decomposing proteins and fats under the action of microorganisms and endogenous enzymes to produce unique flavors.The products formed in different regions and climatic conditions have their own characteristics.In China,Jinhua ham,Xuanwei ham,Laohuo ham,Guizhou sour meat and Canton sausage are popular for their unique flavors,and abroad,such as Iberian ham in Spain,salami in Italy and Bayonne ham in France.The traditional fermentation process is in an open environment,and the temperature and humidity of the air and the cleanliness of the environment affect the phase of bacteria in the environment.Moreover,the traditional processing process has defects such as long time,easy contamination by microorganisms and no standardized production,which restrict the refined and deepened development of meat products and the variety of products in China.The fermented foods in Guizhou are quite abundant,and in this paper,a strain suitable as a meat fermentor was screened from traditional fermented meat products in Guizhou,and a self-developed direct-injection fermentor for meat was prepared using indigenous microbial resources and applied to loin ham to shorten the fermentation time of ham,improve the sensory quality of ham,enhance the flavor and safety of the product,and provide a theoretical basis for promoting the development of the meat industry.The research content and results of this paper are as follows.(1)Screening of a strain of lactic acid bacteria suitable as a fermentor for meat.A total of 10 samples of sour meat,sausage and wind meat from different regions of Guizhou were initially screened for protein degradation ability,and the physiological and biochemical properties,safety and production adaptability of the strain were comprehensively evaluated,and a strain of Lactobacillus plantarum was obtained after16 S r DNA identification and named Lactobacillus plantarum SJ-4,which can tolerate 6% Na Cl and 150mg/kg Na NO2,does not produce NH3,H2 S,H2O2 and other harmful products,has no amino acid decarboxylase activity,can decompose proteins but no lipolytic activity,has an optimal temperature of 37 ℃and an optimal p H of 6.0.It is cultured in MRS broth medium for 4 h into logarithmic phase,and continued to be cultured until 18 h when the p H dropped to 3.80,which can reach the condition of being used as meat fermentor for meat.(2)Optimization of enrichment medium and preparation of direct-injection fermenters.Using MRS broth medium as the base medium,the carbon source,nitrogen source,inorganic salt and growth factor of lactic acid bacteria medium were optimized.Orthogonal experiments showed that 2% glucose,1.5% yeast powder,1.5% tryptone,4% cucumber juice,0.2% 0.2 mol/L Na2HPO4-0.2 mol/L KH2PO4,0.5% sodium acetate,0.2% citrate triamine The density of Lactobacillus plantarum reached 3.8×109 CFU/m L after 16 h of incubation at 37°C.After high-density incubation,the Plackett-Burman test,the steepest climb test,and the Box-benhnken test were used to optimize the density of Lactobacillus plantarum SJ-4.The optimal cryoprotectant for Lactobacillus plantarum SJ-4 showed that when added with 11.00 g/100 m L of skim milk,6.00 g/100 m L of glycerol,and 6.00 g/100 m L of arginine,the vacuum freeze-drying was used to prepare the direct-injection ferment of Lactobacillus plantarum,and the results showed that the survival rate of the bacteria in the freeze-dried powder could reach(72.22% ± 1.97),and the number of viable bacteria was about 1010CFU/g.(3)Effect of direct-injection fermenters on the structure of bacterial flora of loin ham.The alpha-diversity results showed that the inoculation promoted the diversity of bacteria in ham,and the histogram results showed that the bacterial flora of the experimental group was more concentrated in the thick-walled phylum,the anthropoid phylum,and the deformed phylum,while the control group was dominated by the thick-walled phylum.The results of the horizontal histogram of the bacterial phylum showed that the experimental group was more concentrated in the phylum Thick Walled Bacteria,Bacteroides,and Bacteroides than the control group.The genus level histogram showed that the experimental group was dominated by beneficial bacteria,such as Staphylococcus spp.,Lactobacillus spp.and Eckermannia spp.and the control group had more Staphylococcus spp.The results of strain heat map and PCA clustering analysis showed that the addition of direct injection fermenters promoted the microbial phase in ham and could inhibit the production of harmful microorganisms,thus improving the product quality.(4)Effect of direct-injection fermenters on flavor quality of loin ham.The effect of adding Lactobacillus plantarum on the color,texture,electron tongue response value and flavor components of ham was investigated by applying direct-injection fermenters to the curing process of loin ham and compared with the control group.The results showed that the brightness(L*),yellowness(b*)and color(E*)of the ham were significantly different from those of the control group after the addition of lyophilized powder(P<0.05),but there was no difference in the redness(a*)(P>0.05),and the inoculation of bacteria could promote the formation and stability of ham color;the differences between the hardness,chewiness,cohesiveness and elasticity of the experimental and control groups were measured by a texture meter,and the results showed that The experimental group was significantly different from the control group in hardness and chewiness(P<0.05),and there was no significant difference in elasticity and cohesiveness(P>0.05),and the inoculation of Lactobacillus plantarum improved the quality of ham;the results of electronic tongue response value analysis showed that the experimental group had a richer taste,and was higher than the control group in freshness,richness,astringency,and sourness.Analysis of the ham by GC-MS for flavor components indicated that the addition of Lactobacillus plantarum increased the content of characteristic flavors such as nonanal,octanal,acetic acid,and 2-ketones in the ham,and that Lactobacillus plantarum promoted the formation of flavor components in loin ham.