2种蛋白肽对电离辐射损伤小鼠的保护作用

目的:探究众多生物活性肽中口感愉悦的菠萝蜜蛋白肽和胶原蛋白肽对60钴γ射线辐射损伤小鼠的辅助保护作用.方法:采用无特定病原体(SPF级)雌性BALB/c小鼠288只,随机分为四批,每批6组,每组12只.每组设计空白对照组、模型对照组、菠萝蜜蛋白肽低、高剂量组(0.20、0.80 g/kg BW)以及胶原蛋白肽低、高剂量...     

短波紫外发光二极管处理对脂环酸芽孢杆菌的灭活效果及作用机制

短波紫外发光二极管（ultraviolet-C light-emitting diode，UVC-LED）处理是一种新型的非热杀菌技术。本实验以果汁中常见的致腐菌脂环酸芽孢杆菌（Alicyclobacillus acidoterrestris）为目标菌，研究UVC-LED对脂环酸芽孢杆菌的杀灭作用，通过测定处理后细菌胞内核酸和蛋白质泄漏量、细胞膜通透性、胞内活性氧（reactive oxygen species，ROS）的累积水平以及胞内蛋白质和DNA的损伤情况，进一步探究UVC-LED对脂环酸芽孢杆菌的杀菌机理。结果表明：增加UVC-LED的照射剂量可增强其对脂环酸芽孢杆菌的杀灭效果，当照射剂量增加至50 mJ/cm2时，生理盐水中存活的细菌数量降低4.6（lg（CFU/mL））。通过对存活曲线的模拟，发现UVC-LED对生理盐水中脂环酸芽孢杆菌的杀灭作用既符合log-linear模型，又符合Weibull模型。处于不同生长时期的细菌对UVC-LED的敏感度不同，其中处于对数期的细菌对UVC-LED更敏感。照射处理导致膜通透性的改变以及内容物的泄漏，说明细胞膜结构遭到一定程度的破坏，但是胞内ROS的累积水平没有显著提高（P＞0.05），拉曼光谱分析表明胞内蛋白结构有所改变，经吖啶橙（acridine orange，AO）染色荧光显微镜观察发现照射处理后菌体DNA的结构变化明显。综上，UVC-LED可通过造成DNA损伤、蛋白结构变化和细胞膜透性改变从而杀灭脂环酸芽孢杆菌，根据破坏程度的不同，推测DNA损伤是细胞死亡的主要原因。     

Detection Methods for Irradiated Foods

ABSTRACT: Proper control of irradiation processing of food is very critical to facilitate international trade of irradiated foods and to enhance consumer confidence, consumer choice, and safety. Analytical detection of radiation‐processing of food is very important to implement quality control at all levels. An ideal detection method should measure a specific radiation effect, which is proportional to the dose and should not be affected by processing parameters and storage conditions or the length of time between irradiation processing and analysis. The detection of irradiated foods is mainly based on radiolysis of lipids, modification of amino acids, modification of DNA, modification of carbohydrates, formation of free radicals, release of hydrogen gas, alterations in microbial load, measurement of biological difference, and other physical methods.     

Effects of fat levels on changes in flavor pattern of irradiated pork patties

The effects of fat levels on changes in flavor pattern of irradiated pork patties were evaluated by using electronic nose. Total peak amount decreased with increasing fat level and irradiation dose, and the increased fat level and irradiation dose influenced the formation of new peaks at latter retention time. For the principal component analysis, the irradiated pork patties with containing higher fat level were clearly separated from the other treatments. The irradiation dose also affected the position of spot in identical fat level. It is possible to distinguish the changes in flavor patterns due to fat content and irradiation dose by using electronic nose.     

UV disinfection of Giardia lamblia cysts in water

The human and animal pathogen Giardia lamblia is a waterborne risk to public health because the cysts are ubiquitous and persistent in water and wastewater, not completely removed by physical-chemical treatment processes, and relatively resistant to chemical disinfection. Given the recently recognized efficacy of UV irradiation against Cryptosporidium parvum oocysts, the inactivation of G. lamblia cysts in buffered saline water at pH 7.3 and room temperature by near monochromatic (254 nm) UV irradiation from low-pressure mercury vapor lamps was determined using a "collimated beam" exposure system. Reduction of G. lamblia infectivity for gerbils was very rapid and extensive, reaching a detection limit of >4 log within a dose of 10 JM-2. The ability of UV-irradiated G. lamblia cysts to repair UV-induced damage following typical drinking water and wastewater doses of 160 and 400 JM(-2) was also investigated using experimental protocols typical for bacterial and eucaryotic DNA repair under both light and dark conditions. The infectivity reduction of G. lamblia cysts at these UV doses remained unchanged after exposure to repair conditions. Therefore, no phenotypic evidence of either light or dark repair of DNA damage caused by LP UV irradiation of cysts was observed at the UV doses tested. We conclude that UV disinfection at practical doses achieves appreciable (much greater than 4 log) inactivation of G. lamblia cysts in water with no evidence of DNA repair leading to infectivity reactivation.     

The effect of γ-ray irradiation on the drying characteristics and final quality of dried potato slices

γ irradiation is known to be effective when used to reduce post‐harvest losses and control micro‐organisms and insects in stored products. It has been commonly used for processing dehydrated vegetables and fruits. However, few studies have been reported on the use of a γ irradiation treatment combined with a drying process. This study focuses on improving current technology as well as introducing a new technology by which bioproducts, dried by hot‐air, are pretreated with γ irradiation. Experiments were done to study the influence of irradiation dose air temperature and slice thickness on the dehydration rate and internal temperature of irradiated potato. These three factors were found to affect the dehydration rate and internal temperature of the potato, with an increase in irradiation dose, increasing the rate of dehydration and the internal temperature. The greater the dose, the lower the vitamin C content and the lower the rehydration ratio. The L‐colour values of the dried‐product under low dose irradiation were greater than for non‐irradiation, and at >6 kGy, the higher the dose, the lower the L‐value.     

Use of the DNA Comet Assay to detect beef meat treated by ionizing radiation

The DNA Comet Assay has been described as a rapid and inexpensive screening test to identify radiation treatment of food. In this work, this method was applied to detect the treatment of beef meat pieces either by gamma rays or electron beam. The dose levels were 2.5, 4.5, and 7.0kGy for chilled samples, and 2.5, 4.5, 7.0 and 8.5kGy for frozen samples. The analyses were made over periods of 15 and 30 days after irradiation for the chilled and frozen samples, respectively. The effects of gamma rays and electron beam on DNA migration in the test were similar. The DNA Comet Assay, under neutral conditions, made it easy to discriminate between irradiated and non-irradiated beef.     

Absorbed‐dose estimation and quality attributes of gamma‐irradiated fresh shiitake mushrooms

BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose‐dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low‐dose re‐irradiation (200‐600 Gy), medium‐dose re‐irradiation (1‐3 kGy) and high‐dose re‐irradiation (2‐6 kGy) were performed and compared using an additive dose method. An electronic‐nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One‐kGy‐irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose‐dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1‐3 kGy re‐irradiation technique gave most promising results. An E‐nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy‐irradiated mushrooms. © 2012 Society of Chemical Industry     

食品辐照对食品品质的影响及其安全性

简要综述食品辐照对食品营养品质的影响。低剂量辐照食品对食品糖粉、蛋白质、脂肪和维生素没有影响,适当的剂量辐照食品可以降解食品中农药残留,减轻食品过敏,杀死有害微生物,提高食品品质。因此辐照食品也是安全的。     

电子束辐照对赭曲霉毒素A的降解效果及玉米品质的影响

以赭曲霉毒素A纯品和玉米为研究对象,研究了电子束辐照对赭曲霉毒素A的降解效果及对玉米品质的影响。结果表明,赭曲霉毒素A的降解率随着辐照剂量的增加而提高,在3kGy的辐照剂量下,初始浓度为310.0 μg/L的赭曲霉毒素A降解率为49.55%,当辐照剂量增大到5 kGy时,降解率达到93.19%,此后降解率随辐照剂量增加的趋势变缓。电子束辐照对玉米的常规营养成分、氨基酸含量及其组成几乎没有影响,但5 kGy剂量的电子束辐照对玉米脂肪酸组成及脂肪酸值有显著影响。因此,3～5kGy可以作为电子束辐照降解玉米中赭曲霉毒素A的参考剂量。     

PCR-DGGE技术分析不同包装条件下鱼肉表面优势菌的菌群变化

采用聚合酶链式反应-变性梯度凝胶电泳（polymerase chain reaction-deformation gradient gel electrophoresis analysis,PCR-DGGE）技术研究3 种包装（空气、真空、气调）结合钴60辐照技术对鱼肉表面优势菌菌群的影响,分别选择6 种辐照剂量（0、2、4、6、8、10 kGy）照射4 ℃贮藏18 d后的鱼肉表面优势腐败菌群进行研究。方法：采集第18天不同包装不同剂量的草鱼肉样品,洗脱鱼肉表面菌;提取DNA,扩增16S rDNA的V3可变区,用PCRDGGE技术鉴定优势菌,割胶回收测序。结果表明：不同包装鱼肉表面优势菌群数量和种类不同,在样品中共同的优势腐败菌为假单胞菌,在空气包装中优势腐败菌是假单胞菌、乳酸菌和沙雷菌,沙雷菌在辐照剂量高于8 kGy时被抑制。在真空包装中优势腐败菌是假单胞菌、沙雷菌、热死环丝菌和耶尔森菌,沙雷菌辐照剂量高于6 kGy时被抑制,而耶尔森菌在2 kGy以上即被抑制,热死环丝菌在6、8 kGy辐照条件下才出现,其具有很高的辐照抗性。在气调包装中优势腐败菌是假单胞菌和乳酸菌,但乳酸菌仅在气调包装2 kGy辐照和气调包装8 kGy两种辐照包装条件下是优势腐败菌。结果表明,PCR-DGGE技术可以很好地鉴别鱼肉表面优势腐败菌。     

高能电子束对大米食用品质的影响

分别采用剂量为0、1、2、3、4、5、6 kGy的电子束辐照大米样品,考察其对大米品质的影响。结果表明：不同剂量的电子束辐照对大米的水分含量和浸泡吸水率无显著影响（P＞0.05）;随着辐照剂量的增加,大米的加热吸水率、体积膨胀率显著下降（P＜0.05）;辐照剂量显著影响米饭的蒸煮品质（P＜0.05）,剂量为5 kGy时蒸煮米饭出现明显的褐变。电子束辐照大米的剂量不宜超过2 kGy,以1 kGy的辐照剂量较佳。     

Inactivation of Escherichia coli JM109, DH5alpha, and O157:H7 suspended in Butterfield's Phosphate Buffer by gamma irradiation

ABSTRACT:  Food irradiation is a safe and effective method for inactivation of pathogenic bacteria, including Escherichia coli O157:H7, in meat, leafy greens, and complex ready-to-eat foods without affecting food product quality. Determining the radiation dose needed to inactivate E. coli O157:H7 in foods and the validation of new irradiation technologies are often performed through inoculation of model systems or food products with cocktails of the target bacterium, or use of single well-characterized isolates. In this study, the radiation resistance of 4 E. coli strains, 2 DNA repair deficient strains used for cloning and recombinant DNA technology (JM109 and DH5α) and 2 strains of serotype O157:H7 (C9490 and ATCC 35150), were determined. The D -10 values for C9490, ATCC 35150, JM109, and DH5α stationary phase cells suspended in Butterfield's Phosphate Buffer and irradiated at 4 °C were 229 (± 9.00), 257 (± 7.00), 61.2 (± 10.4), and 51.2 (± 8.82) Gy, respectively. The results of this study indicate that the extreme radiation sensitivity of JM109 and DH5α makes them unsuitable for use as surrogate microorganisms for pathogenic E. coli in the field of food irradiation research. Use of E. coli JM109 and DH5α, which carry mutations of the recA and gyrA genes required for efficient DNA repair and replication, is not appropriate for determination of radiation inactivation kinetics and validation of radiation processing equipment.     

辐照处理对柄曲霉素的降解效果研究

采用不同剂量(0、3、6、9、12、15 kGy)60Co-γ射线对柄曲霉素(sterigmatocystin,STC)溶液进行辐照处理,研究辐照剂量、不同溶剂以及不同初始浓度对柄曲霉素辐照降解效果的影响。结果表明:60Co-γ射线可有效降解溶液中的柄曲霉素,且降解率随着辐照剂量的增大而增加。当辐照剂量为3 kGy时,STC的降解速率依次为水>氯仿>乙腈>甲醇。当辐射剂量大于6 kGy时,水、乙腈和氯仿中STC的降解率相近,且甲醇中STC降解率也相对增加。在同一辐照剂量下,柄曲霉素的初始浓度越低,其降解率越高。     

SIGNIFICANCE OF RESIDUAL ORGANISMS IN FOODS AFTER SUBSTERILIZING DOSES OF GAMMA RADIATION: A REVIEW1

The nature of the flora surviving substerilizing irradiation of foods is dependent on the dose applied and the conditions of applications as well as the microenvironment of the food. At a dose level low enough to preserve acceptable sensory properties of fresh food, few if any of the common contaminants of public health significance survive irradiation. Survivors are weakened and present no unique problem of acquired resistance through recycling. Those bacteria surviving a low dose treatment of a relatively contaminated product like ground beef can grow under normal storage conditions and cause obvious sensory spoilage. Thus, low dose irradiation extends the shelf-life of fresh foods and reduces public health hazards, but foods so treated require normal care in production and distribution.     

辐照对猪肉火腿肠风味与品质的影响

分别以1、3、5、7、9 kGy剂量辐照处理火腿肠,然后对其辐照异味强度、脂质氧化、挥发性风味化合物、色差等指标进行检测,分析辐照对火腿肠风味及颜色品质的影响。结果发现,辐照处理可以显著促进火腿肠中脂质的氧化(P0.05),使得红度值(a~*)相比对照组显著降低(P0.05),但是对亮度值(L~*)和黄度值(b~*)影响不显著(P0.05)。随着辐照剂量加大,火腿肠的辐照异味明显增强,1~5 kGy范围内辐照异味不明显,当辐照剂量增加到7 k Gy时,火腿肠产生明显的令消费者不能接受的辐照异味。挥发性含硫化合物、2-丁烯、戊烷、1-戊烯、辛烷、己烷以及醛类化合物含量与对照组相比显著增多(P0.05),且与辐照剂量呈正相关。二硫化碳、二甲基二硫醚、2-甲基丙醛、3-甲基丁醛、己醛、丁烯和二甲苯是火腿肠辐照后产生的最主要挥发性化合物。结果表明,火腿肠经辐照处理后风味和色泽会发生劣变,特别是5 kGy以上的辐照剂量,并且这些品质变化与火腿肠中脂质的氧化密切相关。     

Optimizing irradiation treatment of shell eggs using simulation

Accurate dose calculation is needed to ensure proper irradiation process control to maintain the freshness of the product. Our objective was to establish the best irradiation treatment for shell eggs taking into account their different components (shell, albumen, yolk). Computer tomography (CT) data were used to generate a 3-D geometry to simulate dose distributions within 1 egg using a radiation transport code (MCNP5). Radiation energies used for simulation were 10 MeV (high-energy) and 1.35 MeV (low-energy) for electron beam, 5 MeV for X-rays, and 1.25 MeV for a gamma-rays source such as Co-60. Low-energy (surface) e-beam simulation indicated that electrons only penetrate up to the thin albumen (0.6 cm). Because of their irregular shape, shell eggs should be irradiated from the side (rather than from top or bottom) for better dose distribution. For high-energy e-beam simulation, the entire egg was irradiated and the best results were obtained when the egg was irradiated from both sides, showing a dose uniformity ratio (D(max)/D(min)) of 1.42. X- or gamma-ray source simulation from one side only, the dose uniformity ratio was 3.38 and 3.12, respectively. For surface-only irradiation, a low-energy e-beam provides a uniform dose distribution. To irradiate the entire egg, 2-sided high-energy e-beam sources are required for an efficient treatment. Unless the product rotates in front of the source, the dose uniformity ratio for X-ray or gamma ray is not adequate for shell egg treatment for pathogen decontamination purposes. Practical Application: Proper control of irradiation treatment of foods such as shell eggs is critical to ensure pathogen inactivation while maintaining product freshness. Simulation allows for accurate calculation of dose distribution within the egg to further establish the best irradiation scheme.     

不同辐照剂量对红豆分离蛋白结构及特性的影响

采用Lowery法、ANS荧光探针法、圆二色光谱、荧光光谱等方法分别对不同辐照处理的红豆分离蛋白溶解度、表面疏水性、蛋白质二级、三级结构、流体动力学半径进行分析。结果表明:随着辐照剂量的增加,红豆分离蛋白的二级结构中α-螺旋结构向无规则卷曲结构的转变,Trp残基所处微环境极性先增强后减弱,这与其表面疏水性呈现正相关,蛋白颗粒大小随着辐照剂量的增加先减小后增大,在5 k Gy辐照剂量处理时达到最小,这与其溶解性呈现负相关。     

Radiation preservation of meat and meat products: A review

The World Health Organisation (WHO) in 1980 clarified the position regarding the medical acceptability of irradiated foods when it said‘…no health hazard results from consuming any food irradiated up to a dose of one megarad (1 Mrad)’. This resulted in renewed interest in irradiation as a cost-effective alternative to traditional preservation methods such as canning and freezing. Thus, radurisation (the application of ionising radiation at a dose level which substantially reduces the microbial population) increases the shelf life of poultry, comminuted meat and meat dishes significantly. Low dose irradiation, or radicidation, eliminates parasites such as Trichinae and cysticerci in pork and, very importantly, salmonella organisms in poultry and red meat. Therefore, irradiation has an important rôle to play in public health protection. High dose irradiation, or radappertisation (‘cold sterilisation’), uses doses in excess of 1 Mrad and is analogous to retorting as understood in the canning industry. However, it can adversely affect quality in producing ‘free radicals’ in high protein foods such as meat. To prevent this, special precautions are necessary, e.g. irradiation is conducted at very low temperatures and the product is usually vacuum packed.A further potential use of irradiation is its ability to reduce the quantity of nitrite necessary in cured meats. This may become of practical significance if legislation further reduces the amount of nitrite permitted in these products.     

高能电子束辐照对大米中微生物的杀灭效果

采用单因素试验和正交试验方法,以辐照剂量、辐照时间、物料厚度为变量,研究高能电子束辐照对大米中微生物的影响,探明高能电子束辐照对大米中主要微生物产生明显作用效果的最佳作用条件。结果表明,不同辐照条件对大米中菌落总数、霉菌和酵母菌以及大肠杆菌杀菌效果不同。随着辐照剂量的增大,对大米中微生物杀菌效果越好。正交试验优化得出高能电子束辐照最佳条件为：辐照剂量4 kGy、辐照时间6 s、辐照物料厚度10.5 cm。此条件下,测得大米中菌落总数为82 CFU/g,霉菌和酵母菌总数为2 CFU/g,大肠菌群未检出,高能电子束辐射对大米中微生物杀灭率均超过99%。