The Preservation Effect Of ?-polylysine And Pullulan On Northern Tofu

The shelf life of tofu depends on the number and propagation speed of spoilage bacteria in tofu.In the process of storage,the spoilage is easy to dominate,so the inhibition of spoilage is the key to prolong the shelf life of tofu.At present,enterprises have combined the high-temperature sterilization method with boxed water injection,increased the heating time,increased the amount of added salt and other methods to inhibit the spoilage bacteria,to extend the shelf life of tofu,but the texture of the product is not ideal,consumers do not approbate the product,affecting business efficiency.Using microbial source preservatives on tofu antibacterial study,can not affect the quality and taste of tofu in the case of alternative chemical preservatives to inhibit spoilage,is conducive to extend the shelf life of products.The application of microbial source preservative pullulan polysaccharide and ?-polylysine to inhibit the main spoilage of northern tofu is rarely reported.In this experiment,with spoiled no packaging and boxed packaging spoilage north-tofu as research object,the specific spoilage organisms was separated,isolated and purified.Studying the correlation between tofu quality and spoilage bacteria.To study the in vitro antibacterial effect of ?-polylysine,pullulan,sodium diacetate and its complexes on the main spoilage of tofu.To study the antibacterial effect of ?-polylysine,pullulan and its complex in tofu under different storage conditions,and to determine the shelf life of tofu with different concentration of preservative.In order to further study the microbial source preservative in the tofu preservation on the development and utilization of scientific basis.The main conclusions of this test are as follows:(1)In the separation and identification of the main spoilage of north tofu,spoiled no packagin-g and boxed packaging spoilage north-tofu were used as research object.After separation and purification,the results showed that:there were four corruption strains,which were identified as Staphylococus haemolytcus,Candida krusei,Brevibacillus parabrevis and Streptococcus thoralten-sis.(2)The effects of different spoilage on the corruption of tofu were studied in the study of the correlation between the quality of tofu and the spoilage bacteria:Candida krusei,Staphylococcus haemolyticus and Streptococcus thoraltensis are the main microbes that cause tofu sticky,ladle and softened texture,while Brevibacillus parabrevis has no significant effect on tofu corruption.Streptococcus thoraltensis is the main species that cause two tofu to acid.(3)In vitro antibacterial effect of three preservatives on the main spoilage of tofu,the minimu-m inhibitory concentration(MIC)and antibacterial effect of different preservatives were determin-ed by micro-turbidimetric method and double dilution method:On the condition of pH 6.5,inhibitory effect of Streptococcus thoraltensis:Pullulan>?-poly lysine>sodium diacetate,MIC were 8?g/mL,16?g/mL and 250?g/mL.Inhibitory effect of Br evibacillus parabrevis:sodium diacetate>Pullulan>?-polylysine,MIC were 16?g/mL,125?g/mL and 2000?g/mL.Inhibitory effect of Candida krusei:?-polylysine>Pullulan,MIC were 1000?g/mL and 2000?g/mL,sodium diacetate(4000?g/mL)has no inhibitory effect on Candida kru-sei.Inhibitory effect of Staphylococus haemolytcus:Pullulan>?-polylysine>sodium diacetate,MIC were 16?g/mL,64?g/mL and 2000?g/mL.After the combination of the three kinds of preservatives,the synergistic effect of Streptococc-us thoraltensis,Brevibacillus parabrevis,Staphylococus haemolytcusand were synergistic.?-poly-lysine and pullulan had synergistic effect on the resistance of Candida krusei,while the other combinations had no synergistic effect on Candida krusei,therefore,s-polylysine and pullulan combined with the best antibacterial effect.(4)The effects of pullulan and ?-polylysine and their complexes on the shelf life of tofu were studied in different storage conditions:At the temperature of 4?,the shelf life of the blank group of tofu is 6 days,0.015%s-polyly-sine,the results showed that the shelf life of 0.015%s-polylysine,0.020%?-polylysine was 7 days,the shelf life was prolonged by 1 day,and 0.025%?-polylysine was added for 2 days.At the temperature of 20?,the shelf life of tofu<1d,1d<adding 0.01%pullulan,0.015%?-polylysine,0.020%?-polylysine<2d,extended shelf life of Id,2d<adding 0.02%pullulan,0.03%pullulan,0.025%s-polylysine<3d,prolong 2d shelf life.At the time of 30?,the shelf life of the blank group was 12h,the addition of 0.01%pullulan,0.015%?-polylysine prolonged the shelf life of 4h,the addition of 0.02%pullulan,0.03%pullulan prolonged the shelf life of 8h,0.020%?-polylysine prolonged shelf life of 4?8h,adding 0.025%s-polylysine to extend the shelf life of 4?12h.After the compound agent,the shelf life is prolonged by 1?2d at 4?,the shelf life is prolonged by 1?2d at 20?,and the shelf life is prolonged at 30?.Therefore,under different storage conditions,adding 0.025%?-polylysine in tofu was the best,and the shelf life was prolonged for 2 days.