Studies On Controlling Techniques Of Food Borne Pathogens On Fresh-cut Carrots And Cucumbers

Both Fresh-cut carrots and cucumbers are important fresh-cut vegetables, and they arepopular among consumers because of their nutrient-rich, delicious, and health safety. Asready-to-eat fresh foods, their microbial food safety attract more and more attention as thesame with other fresh-cut vegetables. The effects of electron beam irradiation and hot watertreatment in killing pathogens on the surface of fresh-cut carrots or cucumbers as well aseffects on the quality were studied in this paper, and the aim was to improve the microbialfood safety under the premise of keeping their fresh degree.1. The effects of e-beam irradiation in killing food-borne pathogens were obvious. TheD10values of S. Typhimurium, E. coli O157:H7and L. monocytogenes were0.46、0.28and0.33R respectively. E. coli O157:H7were more sensitive to irradiation than those of L.monocytogenes and S. Typhimurium, and S. Typhimurium was the least sensitive bacteriumamong the three pathogens. When the populations of initial inoculated S. Typhimurium, L.monocytogenes and E. coli O157:H7were6.89、7.28、7.67Log CFU/g respectively,1Rdose caused2.56,2.3and4.17Log CFU/g reductions respectively. The survival amounts of E.coli O157:H7after2R irradiation and L. monocytogenes after2.5R treatment were belowdetection limit (<0.6log CFU/g).1R irradiation caused about13.5%loss of vitamin C anddid not affect the firmness, antioxidant activity, WI and the contents of soluble solids, sugarand β-carotene in fresh-cut carrots, but e-beam treatment of2R significantly reduced thefirmness, the contents of vitamin C, β-carotene, and increased the cell membrane permeability.2. The effects of hot water treatment before eating in killing S. Typhimurium and L.monocytogenes on the surface of fresh-cut carrots and fresh-cut cucumbers were significant.The results showed that70℃2min,80℃1min,85℃45s, and90℃30s hot waterprocessing reduced S. Typhimurium and L. monocytogenes on the surface of fresh-cut carrotsto under the detection line when their initial population were5.10and4.59Log CFU/grespectively, while the80℃1min hot water treatment affect least on the qualities. After thehot water treatment of60℃5min, the populations of S. Typhimurium and L. monocytogeneson fresh-cut cucumbers reduced from5.42and5.16Log CFU/g to under detection line (0.6Log CFU/g). The antioxidant activity of fresh-cut cucumbers decreased, and the cellmembrane permeability increased, while the firmness did not change significantly, and thecucumbers were still fresh and have a good eating value. 3. The treatment of5g/L citric acid combined with hot water of70℃1min improvedthe effect of hot water treatment alone, and decreased the loss of qualities. Combinationaltreatment of5g/L citric acid with hot water of70℃1min was able to achieve thesterilization effect as the same with hot water of80℃1min, while the losses of Vc and β-carotene were only9.82%and4.86%, and the cell membrane permeability reduced. Thus themicrobial safety of fresh-cut carrots was improved.