Effect of ultraviolet processing on selected properties of egg white

The effect of ultraviolet processing (10.6 and 63.7 kJ m(-2)) on selected properties of egg white (absorbance, particle size, protein fractions, free sulfhydryl content, immunoreactivity, viscosity, gelling and foaming properties) was investigated. Ultraviolet exposure induced the development of browning, the formation of large protein aggregates by disulfide exchange, and protein backbone cleavage. However, egg white proteins were differently sensitive to UV radiation. No changes in immunoreactivity, gelling temperature and gel firmness were observed. Independently on the UV dose, light treated egg white produced foams with higher stability. This effect was attributed to protein aggregates jamming in the fluid interstices between bubbles and/or to the higher viscosity of the aqueous phase. The latter was also associated to higher foam volume.     

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。     

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.     

Use of UV-C treatment to inhibit the microbial growth and maintain the quality of Yali pear

Abstract: The effects of UV-C radiation on microbial growth in vitro (Monilinia fruticola) and in inoculated Yali pears (Pyrus bretschneideri Rehd.) were investigated. Moreover, postharvest quality and the activities of defense and antioxidant enzymes were analyzed after the pears were exposed to UV-C irradiation at an energy level of 5 kJ m⁻².The results showed that spore germination of M. fructicola was significantly inhibited by each of the 3 doses (1, 5, and 10 kJ m⁻²) in vitro. In the in vivo assays, lesion diameter on the fruit being inoculated before or after the UV-C treatment was both significantly lower than that on the fruit of control. Meanwhile, the activities of phenylalanine ammonia lyase, β-1,3-glucanase, superoxide dismutase, catalase, and glutathione reductase were induced to high levels by UV-C treatment. We conclude that UV-C treatment could reduce postharvest disease by the germicidal and induced effects and maintain the quality by enhancing the antioxidant enzyme activities. Practical Application: UV-C radiation has recently been proposed as a new technology to avoid chemical fungicides. However, there are few studies regarding the effect of UV-C treatment on Yali pear. In this study, we found that 5 kJ m⁻² UV-C irradiation can control postharvest disease and maintain the quality of Yali pear. This method may be applied to reduce the decay of Yali pears during exporting and storage.     

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。     

UV-C照射与壳聚糖涂膜保鲜处理对鲜切淮山营养品质的影响

对不同贮藏时间的鲜切淮山,采用3.0 kJ/m2剂量的短波紫外线(short-wave ultraviolet,UV-C)照射与质量浓度1.0%壳聚糖涂膜协同处理,研究两种保鲜方法对鲜切淮山营养品质的影响。研究发现,与对照组相比,在短波紫外线照射与壳聚糖涂膜保鲜处理过程中,鲜切淮山中的可溶性固形物、多糖、VC、淀粉、可溶性蛋白质均保持较高含量。研究表明,短波紫外照射与壳聚糖涂膜保鲜处理,有助于提升鲜切淮山的营养品质。     

Effect of UV-C irradiation on the inactivation of inoculated pathogens and quality of chicken breasts during storage

In this study, we evaluated the inactivation of foodborne pathogens inoculated on chicken breasts by UV-C treatment. Chicken breasts were inoculated with Campylobacter jejuni, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium at 6–7 log CFU/g. The inoculated chicken breasts were then irradiated with UV-C light of dose 0, 0.5, 1, 3, and 5 kJ/m². Microbiological data indicated that the populations of the foodborne pathogens decreased significantly (p < 0.05) with increasing UV-C irradiation. In particular, UV-C irradiation at 5 kJ/m² reduced the initial populations of C. jejuni, L. monocytogenes, and S. typhimurium by 1.26, 1.29, and 1.19 log CFU/g, respectively. After UV-C irradiation, the samples were individually packed using polyethylene terephthalate containers and stored at 4 ± 1 °C for 6 d. The pH of the control increased more than the samples irradiated at 0.5, 1, 3, and 5 kJ/m², while TBARS values increased during storage regardless of UV-C irradiation. UV-C irradiation caused negligible changes in Hunter L, a, and b values. These results suggest that UV-C irradiation can be useful in improving the microbial safety of chicken breasts during storage, without impairing quality.     

Synthesis of polycrystalline gallium oxide solar-blind ultraviolet photodetector by Aerosol Deposition

An aerosol deposition method was used to fabricate a solar-blind photodetector (for UV-C) using thin films of β-Ga₂O₃, which is a wide-bandgap oxide material. The Ga₂O₃ films deposited at room temperature presented a polycrystalline structure and a thickness of approximately 4 µm and showed a high transmittance of approximately 70–80 % in the visible region; the transmittance was approximately 60–80 % even after heat treatment up to a 800 °C. The Ga₂O₃ films that were post-annealed at a temperature of 800 °C showed an I_photo/I_dark ratio of approximately 40,000 in the solar-blind region with a light source of 254 nm, together with very good light detection characteristics (initial rising and decay times of 0.45 s and 0.13 s, respectively). Because of the good performances observed for the Ga₂O₃ thin films even at extreme conditions, they exhibit a high potential for use as photodetectors in several applications.     

Immediate and long-term impacts of UV-C irradiation on photosynthetic capacity, survival and microcystin-LR release risk of Microcystis aeruginosa

In this study, the immediate and long-term impacts of shortwave ultraviolet (UV-C) irradiation on photosynthetic capacity, survival, and recovery of Microcystis aeruginosa were investigated. The risk of microcystin-LR (MC-LR) release during irradiation was also estimated. The cell density was determined by a flow cytometry, and typical chlorophyll fluorescence parameters, including the effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse amplitude modulated (PAM) fluorometer. Under various UV-C dosages (140-4200 mJ cm⁻²), photosynthetic capacities were reduced, to different degrees, accompanied by slight cytoclasis and complete degradation of extracellular MC-LR immediately after irradiation. In a 6-d cultivation following UV-C irradiation, cell density and extracellular MC-LR in the samples treated by 140 mJ cm⁻² UV-C irradiation increased from 4.0 × 10⁶ cells mL⁻¹ and 8 μg L⁻¹ to 5.1 × 10⁶ cells mL⁻¹ and 20 μg L⁻¹, respectively. Significant M. aeruginosa cytoclasis (cell density from 4.0 × 10⁶ to 1.0 × 10⁶ cells mL⁻¹) and MC-LR release (2-25 μg L⁻¹) occurred when the UV-C dosage reached 350 mJ cm⁻². Cell cytoclasis and MC-LR release were enhanced in the cultivated samples under higher UV-C dosages. Results revealed that photosynthetic parameters were useful tools to predict the recovery profiles of M. aeruginosa cells, and the MC-LR release risk should be considered after UV-C inactivation.     

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.