Application Of Combined ?-irradiation And Preservatives Treatment On Fresh-keeping Of Tofu

Tofu is a traditional food in China,and it' s loved by people.But the tofu' s shelf-life is short,which greatly hinder the rapid development of the tofu industry.Now tofu' s shelf-life is only one day at room temperature,and 2?3 days at refrigeration temperature.People can only buy it and eat soon,which greatly limits the development of tofu industry.Therefore,the urgent need for effective ways to kill and inhibit microorganisms in the presence of tofu in particular the pathogenic,to improve the quality of its health and prolong shelf-life.Many researchers use the processing methods of microwave,pressure,heat,brine electrolysis and preservatives to extend the shelf life of tofu.But it can' t be applied to the actual production process.Irradiation is a special 'cold technology',sterilization but don' t affect the nutrition and eating quality of food.Meanwhile the cost of irradiation significantly lower than other technologies.Application of combined irradiation and preservatives treatment to extend the shelf life of food while reducing the amount of preservative is a viable approach.Irradiation is an effective cold sterilization technology while adding preservatives is the primary means to extend the shelf life of food.In order to extend the shelf life of food at the same reducing the amount of preservatives,we can combine these two methods together.The effect of irradiation on preservatives' antimicrobial activity and nutrition,physical and sensory quality of tofu,the effects of irradiation and preservatives on microorganism,the comprehensive preservation process that irradiation integrated with preservatives were study.Experiment material is tofu,target strains were Gram-negative(G-)bacteria including Salmonella enteritidis,Shigella flexneri,Escherichia coli and Gram-positive(G+)bacteria including Listeria monocytogenes,Staphylococcus aureus,Bacillus subtil is and Leuconostoc mesenteroides.The main contents in detail as follows:Irradiation under 5 kGy have little effect on preservatives' antimicrobial activity,but 10?15 kGy irradiation can effect most preservatives' antimicrobial activity,and the higher the irradiation dose the greater the impact.Irradiations in solution state of preservatives were more sensitive than that in the solid state.It was observed that G+ bacteria were more sensitive than to G-bacteria on antimicrobial resistance changes.Irradiation can effectively decrease the microorganism while kill Pathogenic bacteria in tofu,it can effectively delay the arrival of the microbial logarithmic phase also.Potassium sorbate,sodium diacetate,sodium propionate and sodium acetate dehydrogenation can effectiveiy inhibition of salmonella in tofu but nisin can't.Irradiation integrated with preservatives can enhance antibacterial effect compared with a single method,while sequence has little effect on it.The effects of irradiation on the physical and chemical quality of tofu smaller than heat treatment,especially in dehydration and hardens,and they all have little harmful effect on sensory quality of tofu.Low dose irradiation under 4.3 kGy had little effect on nutrition.0.1 g/100mL potassium sorbate 3.4 kGy irradiation or 0.3 g/100mL potassium sorbate+1.1 kGy irradiation can extend the shelf-life of tofu at least 10 days and 0.3 g/100mL potassium sorbate +3.4 kGy irradiation can extend the shelf-life of tofu at least 12 days.