葡萄柚精油协同紫外线灭活果蔬表面诺如病毒和大肠杆菌的研究

Study on Elimination of Norovirus and E.coli on Fruits and Vegetables by Grapefruit Essential Oil Combined with UV Radiation

【目的】果蔬中大肠杆菌O157:H7(Escherichia coli O157:H7)和诺如病毒(norovirus)常导致食源性疾病暴发。紫外照射(UV-C)是灭活病原微生物的常用手段,但由于果蔬表面的特殊构造,UV-C对微生物的灭活效果受到一定的限制,同时也影响食品的颜色、质地和组织稳定性。葡萄柚精油(GEO)具有较强的抗菌和抗病毒活性且使用安全,但单独使用成本太高。试验旨在探究GEO协同UV-C作用对果蔬表面病原微生物的灭活效果,为提升食源性疾病暴发的防控技术提供科学依据。【方法】使用特定浓度的大肠杆菌O157:H7(Escherichia coli O157:H7)(6.07×108 CFU/mL),鼠诺如病毒(MNV-1)(5.29×105 PFU/mL)和杜兰病毒(TV)(5.67×105 PFU/mL)在无菌环境下人工污染樱桃番茄、生菜和蓝莓表面,利用不同质量浓度GEO(1.0,4.0,8.0,16.0,32.0,64.0 mg/mL)和不同照射剂量UV-C(20,40,60,80,100,200 mJ/cm^(2))协同处理樱桃番茄、生菜和蓝莓表面的病原体,分析GEO与UV-C对病原体的协同灭活功效及其机理,并评估该灭活方法对果蔬组织损伤的影响。【结果】观察到UV-C的照射剂量80,100,200 mJ/cm^(2)对3种病原体均具有显著的灭活作用,GEO的抗病原作用具有剂量和时间相关性。在8 mg/mL GEO处理12 min后再与UV-C(100 mJ/cm^(2))协同作用下3种病原体的含量显著减少(2.42 log10~3.22 log10,P=0.017~0.029)。采用同样的协同方式处理樱桃番茄、生菜和蓝莓表面的病原体,发现同样具有显著的灭活效果(1.9 log10~3.68 log10,P=0.012~0.035)。透射电子显微镜结果表明,GEO引起病毒衣壳蛋白变性,这解释了GEO的抗病原作用及其在紫外线照射下的增强作用。最后,果蔬质构分析和感官评价表明,GEO的添加对测试食品的味道和品质影响较小。【结论】GEO协同UV-C处理是一种高效灭活果蔬表面病原体的方法,同时对测试产品的品质影响较小,将为食源性疾病防控提供新的技术支持。

[Objective]Escherichia coli O157:H7 and norovirus in fruits and vegetables often cause outbreaks of foodborne illness.Ultraviolet irradiation(UV-C)is a commonly used method to inactivate pathogenic microorganisms.Due to the unique structure of fruit and vegetable surfaces,the effectiveness of UVC in microbial inactivation is limited,and it also affects the color,texture,and tissue stability of foods.Grapefruit essential oil(GEO)has strong antibacterial and antiviral activities and is safe to use,but the cost of using it alone ishigh.In order to improve the disinfection efficiency of UV-C while reducing tissue damage to fruits and vegetables,this study aims to analyze the combined effect of GEO and UV-C on the inactivation of surface pathogens on fruits and vegetables.[Method]Escherichia coli O157:H7,mouse norovirus(MNV-1),and tulane virus(TV)were artificially contaminated at a certain concentration on the surface of cherry tomatoes,lettuce,and blueberries in a sterile environment.Different concentrations of GEO(1.0 mg/mL,4.0 mg/mL,8.0 mg/mL,16.0 mg/mL,32.0 mg/mL and 64.0 mg/mL)and different doses of UV-C(20 mJ/cm^(2),40 mJ/cm^(2),60 mJ/cm^(2),80 mJ/cm^(2),100 mJ/cm^(2),and 200 mJ/cm^(2))were used to co-treat the pathogens on the surface of cherry tomatoes,lettuce,and blueberries.The synergistic inactivation efficacy and mechanism of GEO and UVC on pathogens were analyzed,and the impact of this inactivation method on fruit and vegetable tissue damage was evaluated.[Result]It was observed that UV-C doses of 80,100,and 200 mJ/cm^(2) had significant inactivation effects on the three pathogens,and the antipathogenic effect of GEO was dose-and timedependent.After treatment with 8.0 mg/mL GEO for 10 minutes followed by UV-C(100 mJ/cm^(2))co-treatment,the levels of the three pathogens were significantly decreased(2.42 log10-3.22 log10[CFU or PFU]/mL,P=0.017-0.029).Adopting the same co-treatment method on cherry tomatoes,lettuce and blueberries,significant inactivation effects were also observed(1.9 log10-3.68 log10[CFU or PFU]/mL,P=0.012-0.035).The results of transmission electron microscopy showed that GEO caused denaturation of the viral capsid protein,which explained the anti-pathogenic effect of GEO and its enhancement under UV irradiation.Finally,textural analysis and sensory evaluation of fruits and vegetables indicated that the addition of GEO had minimal effect on the taste and quality of the tested foods.[Conclusion]This study provides a rapid and effective method to inactivate foodborne pathogens on fruits and vegetables while minimizing the impact on the taste and quality of the tested products.It will provide new technical support for the prevention and control of foodborne diseases.