UV-C辐照降解水中磺胺类药物

采用C类紫外线或称为短波紫外线（即UV-C）辐照降解水中磺胺类药物,考察了磺胺类药物种类、UV光强、磺胺类药物初始浓度、反应液pH对降解效果的影响。结果表明UV-C辐照对磺胺嘧啶、磺胺甲基嘧啶和磺胺甲恶唑的降解过程均符合拟一级反应动力学。UV-C辐照技术对磺胺甲恶唑的去除率最高,在反应液pH为7,光强为142μW/cm^2,初始浓度为0.02mmol/L条件下,辐照30 min后磺胺甲恶唑去除率达到67.80%,而磺胺嘧啶和磺胺甲基嘧啶去除率仅15%左右。通过增大紫外光强和减小初始浓度,可提高反应速率和磺胺甲恶唑去除率。反应液pH对反应效果的影响显著,酸性条件更利于UV-C辐照降解磺胺甲恶唑。     

Combined treatment with chlorine dioxide gas,fumaric acid,and ultraviolet-C light for inactivating Escherichia coli O157:H7 and Listeria monocytogenes inoculated on plums

Combined non-thermal treatment with chlorine dioxide (ClO₂) gas, ultraviolet-C (UV-C) light, and fumaric acid was performed to inactivate Listeria monocytogenes and Escherichia coli O157:H7 inoculated on plums. Plums were treated with ClO₂ gas (15 and 30 ppmv), fumaric acid (0.1, 0.3, and 0.5%), and by UV-C irradiation (3, 5, and 10 kJ/m²). The single treatments with 15 or 30 ppmv ClO₂ gas, 0.5% fumaric acid, and 10 kJ/m² UV-C decreased the population of L. monocytogenes by 1.78, 2.00, 1.65, and 1.62 log CFU/g, respectively, and the population of E. coli O157:H7 by 1.73, 1.81, 1.34, and 2.07 log CFU/g, respectively. In addition, combined treatments reduced the populations of the pathogenic bacteria more than each treatment alone. In particular, the combined treatment with ClO₂ gas (30 ppmv) for 20 min, fumaric acid (0.5%), and UV-C (10 kJ/m²) decreased the populations of L. monocytogenes and E. coli O157:H7 by 6.26 and 5.48 log CFU/g, respectively. These results suggest that combined treatment with ClO₂ gas, UV-C light, and fumaric acid may be a useful hurdle technology to enhance the microbiological safety of plums.     

Effectiveness of UV light as a means to reduce Salmonella contamination on tomatoes and food contact surfaces

The effectiveness of ultraviolet light at a wavelength of 254 nm to reduce Salmonella contamination on tomatoes and food contact surfaces was evaluated. Inoculated tomatoes were exposed to UV-C light at doses ranging from 0 to 223.1 mJ/cm². All UV treatments significantly reduced Salmonella populations (p < 0.05). The effectiveness of UV-C light in reducing Salmonella contamination on different locations on tomato surfaces under various UV doses (0–117.2 mJ/cm²) was also explored. Results indicated that regardless of the locations, UV treatment was shown to be effective in decreasing Salmonella populations. Subsequent studies evaluated possible photoreactivation or dark repair of injured Salmonella post-UV treatment. Following UV light exposure at doses of 0, 22.3, 44.6, and 89.2 mJ/cm², tomatoes were either exposed to visible light for 0, 3, and 5 h or stored in the dark for the same amount of time. Photoreactivation was not detected, nor was dark repair. UV light was also evaluated for its effectiveness to reduce Salmonella contamination on food contact surfaces (stainless steel, HDPE, waxed cardboard and PVC). Contaminated coupons were exposed to UV-C light at 0, 3.3, and 19.7 mJ/cm². Significant differences were observed between coupons treated with UV light and the controls (p < 0.05). Coupons exposed for longer time had greater Salmonella population reductions, except for waxed cardboard coupons. Application of UV-C light to reduce Salmonella contamination in tomato handling facilities is feasible.     

Effect of UV-C irradiation on inactivation of Aspergillus flavus and Aspergillus parasiticus and quality parameters of roasted coffee bean (Coffea arabica L.)

ABSTRACT

This study investigated the antifungal effect of ultraviolet-C (UV-C) against Aspergillus flavus and Aspergillus parasiticus on roasted coffee beans. Also, any changes in the quality of the roasted coffee beans were measured after UV-C irradiation. As UV-C irradiation time increased (0–2 h), the number of surviving A. flavus and A. parasiticus spores significantly (P < .05) decreased. The reduction values of A. flavus in round part, crack part, and whole roasted coffee beans were 2.16, 0.71, and 1.58 log₁₀ CFU g^?1, respectively, and the reduction values of A. parasiticus in round part, crack part, and whole roasted coffee beans were 1.03, 0.37, and 0.72 log₁₀ CFU g^?1, respectively, after 2 h of UV-C irradiation. Field emission scanning electron microscopy showed that the morphology of A. flavus and A. parasiticus spores included expanded wrinkles that were deformed by UV-C irradiation. The Hunter colours were significantly reduced (P < .05). There was no significant change (P > .05) in moisture content, but the pH was significantly decreased (P < .05). Most of the sensory parameters did not change, but there was a significant difference (P < .05) in flavour. Based on this study, 2 h of UV-C irradiation was effective in reducing 90% of A. flavus, but it was not effective against A. parasiticus present on roasted coffee beans. Also, Hunter colour, pH, and sensory parameters (flavour) were changed by UV-C irradiation.     

Viscoelasticity, texture and ultrastructure of cut apple as affected by sequential anti-browning and ultraviolet-C light treatments

The aim of this work was to analyze the effect of UV-C radiation (fluence: 11.2 kJ/m²), with or without an anti-browning pretreatment containing 1% (w/v) ascorbic acid plus 0.1% (w/v) calcium chloride, on the linear viscoelastic properties (oscillatory shear and creep/recovery), instrumental texture (TPA), sensory texture and ultrastructure (ESEM, TEM) of cut apple. Changes in structural features and viscoelastic parameters were mainly evidenced after refrigerated storage. All samples showed a viscoelastic solid behavior with the storage modulus (G′) dominating the viscoelastic response. Overall, both dynamic moduli decreased, and instantaneous compliance (J₀), decay compliances (J₁ and J₂) and fluidity significantly increased after treatments and storage at 5 °C, while retardation times were in general constant. Fracture properties proved to be the most highly correlated with sensory texture. The test panel only significantly differentiated stored untreated apple from the other samples regarding fracturability and juiciness. Mechanical spectra and creep parameters showed ability to evidence ultrastructural differences (rupture of membranes, swelling of cells, alteration of cell walls) in the surface of cut apples subjected to the different treatments.     

UV-C处理对鲜切红心萝卜抗氧化活性的影响

以红心萝卜为实验材料,研究了不同剂量的短波紫外线（ultraviolet-C,UV-C）处理对鲜切红心萝卜的抗氧化系统和抗氧化活性的影响。鲜切红心萝卜用0、0.25、0.5、1.0、2.0 kJ/m2剂量的UV-C处理后于5 ℃贮藏48 h。结果表明,1.0 kJ/m2 UV-C处理能最有效地诱导鲜切红心萝卜中酚类物质的合成,进而导致其含量增加,并提高了红心萝卜中的1,1-二苯基-2-三硝基苯肼自由基清除能力。UV-C处理能促进鲜切红心萝卜中花青素和黄酮类物质含量的增加、延缓抗坏血酸含量的下降、并提高抗氧化酶活性。这些结果表明,UV-C处理可以诱导酚类物质合成,提高抗氧化酶活性,从而显著提升鲜切红心萝卜的抗氧化活性。     

壳聚糖及UV-C处理对冬枣贮藏品质的影响

采用采前壳聚糖喷施、采后短波紫外线照射处理冬枣并低温贮藏,以提高冬枣抗病性,延长保鲜期。对冬枣果实着色、发病情况和品质特性进行分析研究。结果表明：0.5～1kJ/m2 UV-C 照射、壳聚糖处理明显促进了果实的着色,降低了发病率和发病指数,推迟发病3～6d;0.5～1kJ/m2 UV-C 处理可保持枣果较高的糖、酸和VC含量,品质提高,壳聚糖处理对枣果贮藏品质的影响不明显。     

短波紫外照射对玫瑰香葡萄品质和白藜芦醇及其衍生物含量的影响

采用超高效液相色谱-串联质谱法对玫瑰香葡萄中白藜芦醇及其衍生物的含量进行测定。结果表明,当玫瑰香葡萄经过剂量为4.5 k J/m~2的短波紫外照射后,20℃贮藏至48 h时,白藜芦醇和白藜芦醇苷含量达到最高,分别为90.29 μg/g和163.28 μg/g;贮藏至72 h时,紫檀芪含量达到最高38.67 μg/g。短波紫外照射也可以降低可溶性固形物、VC、可滴定酸等品质评价指标的下降速率。     

短波紫外线照射和60Co-γ辐照处理对大樱桃贮藏品质的影响

为探究不同射线辐照处理对大樱桃果实保鲜效果的影响,采用不同剂量短波紫外线（short-wave ultraviolet light,UV-C）照射（1.37、2.05、2.74 kJ/m2）和60Co-γ辐照（0.75、1.5、2.25 kGy）分别处理大樱桃果实,定期检测其冷藏期间生理品质指标和果皮超微结构变化。结果表明：贮藏15 d内,1.37 kJ/m2照射和0.75 kGy辐照较对照组可显著延缓大樱桃果实好果率下降、抑制果实质量损失,较好保持果实质地特性,促进花青素合成,有效抑制过氧化物酶与超氧化物歧化酶活性下降,但对可溶性固形物含量影响不大,且会引起丙二醛含量增加。由于两种处理对好果率、硬度、质量损失率、花青素等感官品质核心指标具有良好的积极作用,因此对丙二醛的不利变化并不足以影响到果实的商品品质评价。电子显微镜结果显示,大樱桃经1.37 kJ/m2照射和0.75 kGy辐照处理后,与对照组相比,能在一定程度上减轻果皮细胞膜、线粒体、叶绿体等细胞结构的损伤程度,显著延缓果皮细胞衰老。此外,在贮藏前期与末期,1.37 kJ/m2照射和0.75 kGy辐照所发挥的作用并不相同。针对于5 d以内的短期贮藏,可采用1.37 kJ/m2 UV-C照射,而长期贮藏则以0.75 kGy 60Co-γ辐照效果更好。     

UV-C处理抑制马铃薯贮藏期发芽及相关机理研究

为提高马铃薯的食用安全性和贮藏品质,本实验研究了短波紫外线(ultraviolet C,UV-C)处理对马铃薯贮藏过程中发芽品质的影响。采用10 kJ/m2 UV-C对马铃薯进行一次处理(贮藏前),二次处理(贮藏前及中期),并测定发芽率、还原糖、苯丙氨酸解氨酶、多酚、赤霉素、α-茄碱等指标。结果表明,UV-C处理能够有效抑制马铃薯贮藏过程中的发芽,同时延缓赤霉素和α-茄碱的上升。二次处理组贮藏至90 d时,薯皮和肉质部分的α-茄碱含量仅为对照组的71.09%、65.75%;105 d时发芽率为68.78%,还原糖含量为0.40%,失重率为4.71%,贮藏品质均优于对照组和一次处理组。综上所述,当处理剂量和方式适宜时,UV-C可在马铃薯发芽控制及品质保持方面获得良好效果,其中二次处理更具优势。