辐照食品的热释光分析鉴定方法研究

本文研究了用热释光分析仪鉴定食品辐照与否的具体方法和鉴定标准。在分离样品中的矿物质后,测量其热释光发光曲线的发光峰面积积分值G1,矿物质经1kGy的剂量照射后,再测量其热释光发光曲线的发光峰面积积分值G2;以G1/G2之值作为样品是否经过辐照的判断依据。通过对国家允许辐照的6大类食品中85个样品的检测分析得出:当G1/G2≥0.10时,可判定样品是辐照过的;当G1/G2<0.10时,判定样品是未辐照过的。     

热释光法在辐照食品检测中出现假阳性问题的探讨

目的探讨热释光法在辐照食品检测中出现假阳性的问题。方法按照标准EN1788-2001《食品与硅酸盐矿物隔绝的食品的辐射检验热致发光法》,采用热释光法对深海鱼加工产品进行辐照食品检测。结果与花椒粉等典型辐照样品不同,深海鱼加工产品虽然检测结果为阳性,但其谱图与典型辐照样品谱图存在一定差异。主要表现为一次发光曲线中,典型辐照样品谱图的发光峰下降舒缓,峰型符合正态分布;而深海鱼加工产品的发光峰下降陡峭,并不符合正态分布。据此,怀疑热释光法对深海鱼加工产品的检测分析结果实为假阳性。结论建议在对深海鱼产品进行辐照检测时,谨慎选用热释光法或采用其他检测方法如气相色谱分析碳氢化合物法进行复验。     

热释光检测辐照香辛料影响因素的研究

影响热释光检测香辛料是否辐照的判定因素很多,包括香辛料的种类、提取矿物的方法、矿物成分、辐照剂量、检测条件、辐照抑制剂量、判定阈值等。研究了香辛料中矿物砂土的粒径、矿物砂土的质量、辐照剂量以及检测条件中的升温速率、积分取值区间对检测准确率的影响。筛选出热释光检测香辛料辐照与否的最佳条件为:矿物砂土粒径3￣8μm、质量0.5￣5.0mg;热释光仪升温速率5￣15℃/s,积分区间为150℃(升温)～260℃(降温)。     

提高辐照食品热释光检测方法效率的技术分析

提出一种提高辐照食品热释光检测效率的改进技术方法,先采用第1发光曲线筛分样品,再利用发光强度比值对筛分后的6 种待定样品进行鉴定。结果表明：改进热释光方法具有100%检测准确率,而需进行参比剂量辐照及后续热释光测量的样品仅为BS EN 1788-2001方法的33.3%,优选筛分阈值后,这一比例还能进一步降低。改进后的辐射食品热释光检测方法明显提高了检测效率,降低了检测费用,是一种可行方法。     

辐照食品分析检测技术的研究进展

本文介绍了国内外辐照食品检测技术的研究进展，着重对化学分析法、电子自旋共振(ESR)法及热释光分析(TL)法进行了阐述，并对今后辐照食品检测技术的研究提出了建议。     

电子束辐照对烧卖中微生物生长模型及货架期的影响

为解决传统食品烧卖产业化生产中因微生物滋生而导致的保质期短的问题，作者以预制生烧卖为试材，研究了不同贮藏温度下烧卖微生物生长规律及过氧化值的变化。结果表明，电子束辐照能够有效降低烧卖微生物数量，延长烧卖保质期，但较高剂量处理会促进脂质氧化。6~8 kGy剂量电子束辐照对脂质氧化影响较小，30 ℃贮藏3 d时，辐照烧卖的过氧化值与未辐照产品无显著性差异（P＞0.05）。4 ℃下冷藏时，6~8 kGy剂量电子束辐照烧卖的保质期可达30 d，较未辐照产品延长20 d。依据不同贮藏温度下的菌落总数、霉菌和酵母菌的变化，分别建立了相应的Gompertz微生物生长模型，模型的相关系数均大于0.95，能够有效描述辐照烧卖贮藏期间微生物动态变化，可预测不同贮藏时间内的微生物生长水平。     

电子束辐照的熟制鲢鱼块贮藏品质分析

该研究以熟制鲢鱼块为原料,使用0、4、8 kGy电子束辐照处理后,分别置于常温和4 ℃中贮藏,通过测定贮藏期间样品菌落总数（TVC）、pH值、硫代巴比妥酸值（TBA）、过氧化值（POV）、挥发性盐基氮值（TVB-N）与质构的变化,研究不同辐照剂量及贮藏温度对熟制鲢鱼块贮藏品质的影响。结果表明,辐照剂量越高对熟制鲢鱼块杀菌效果越好,4 ℃贮藏杀菌效果优于常温贮藏。贮藏温度对鲢鱼块pH值无明显影响,但8 kGy辐照处理会降低鱼块pH值（P<0.05）。鲢鱼块TBA值随着辐照剂量的增加而增加,但不同辐照剂量、不同贮藏温度之间无显著差异（P>0.05）。与未辐照组相比,电子束辐照能有效抑制鱼块POV值和TVB-N值的升高（P<0.05）。质构测定结果显示,当贮藏温度为4 ℃、辐照剂量为4 kGy时,可保持杀菌效果的同时改善熟制鲢鱼块的硬度、弹性和咀嚼性等指标。综合考虑,以4 kGy辐照剂量处理熟制鲢鱼块,并选择贮藏温度4 ℃,其保鲜效果最佳。以上研究可为鲢鱼电子束辐照贮藏保鲜技术的推广应用提供理论依据。     

电子辐照产生蓝色钻石的工艺条件探索

钻石辐照处理后的颜色受辐照源类型、辐照剂量、辐照温度、钻石类型等因素影响。采用束流能量、束流强度不同的电子加速器对43粒钻石进行辐照处理,分析辐照前后钻石的光谱学特征与实验结果的关系,发现:在束流能量为2 MeV、束流强度为10mA的电子直线加速器下,10~12 MGy辐照即可使钻石着色;随着辐照剂量增加,颜色饱和度增加,明度下降;辐照结束后,部分G色级及以上色级的Ⅰa型天然钻石和2颗近无色Ⅱa型CVD合成钻石辐照为蓝色;辐照剂量率对钻石辐照处理结果影响不大;水循环冷却系统保证辐照中热量耗散适宜,40℃以内的辐照温度可保证辐照中钻石裂隙不发生延展;辐照后辐照蓝色钻石在415~478nm间蓝光透过率明显高于其他颜色辐照钻石。     

60Co-γ辐射对马铃薯淀粉特性的影响

采用60Co-γ射线对马铃薯淀粉进行辐照处理,辐照剂量分别为4、8、10、12、16kGy和20kGy,测定淀粉的颗粒特性及淀粉糊的透明度、热稳定性及冷稳定性。结果表明：辐照后的马铃薯淀粉颗粒形貌未发生明显变化、平均粒径变小;淀粉糊的透明度升高,峰值黏度减小,热稳定性及冷稳定性均显著提高。辐照剂量高于10kGy时,淀粉糊的峰值黏度与冷、热稳定性变化趋于平缓。     

辐照对腐乳理化指标的影响

试验采用<'60>Co-γ射线对腐乳进行辐照处理,定期对其蛋白酶活力及理化指标进行测定.研究表明:在辐照剂量小于3kGy的时候,蛋白酶活力由26.86U/g增大到33.60U/g,辐照剂量大于3kGy时,蛋白酶活力由33.60U/g减小到31.78U/g;随着辐照剂量的增大,水溶性蛋白质和氨基酸态氮含量增加,总酸含量不断减小,水分含量降低,食盐含量升高.     

Changes in thermoluminescence properties of minerals separated from irradiated potatoes and garlic during long-term storage under different light conditions

The effect of different light conditions on the specificity and reliability of thermoluminescence (TL) analysis to detect irradiated samples (potatoes and garlic) during 2?years of storage was investigated. The silicate minerals separated from the nonirradiated samples provided a low-intensity TL glow curve with a maximum peak after 300?°C demonstrating the absence of an irradiation history. The TL glow curve from the irradiated samples provided easy discrimination with TL glow curves of high intensity and maximum peak in temperatures range of 160?C185?°C. The results were also confirmed by calculating the TL ratio (TL₁/TL₂) through normalization (re-irradiation) step. The key parameters of the TL analysis including the TL intensity, TL glow curve shape, and the TL ratio exhibited a time-dependent change. The bleaching effect of different light conditions was also significant, which was most prominent in the case of natural light with a prominent decrease in the TL intensity and ratio. The maximum TL glow peak also showed a shift towards the higher temperature. However, all irradiated samples, irrespective of the storage conditions and time, were easily discernable from the nonirradiated ones considering the shape and intensity of the TL glow curve.     

Identification of a gamma-irradiated ingredient (garlic powder) in Korean barbeque sauce by thermoluminescence analysis

Thermoluminescence (TL) analysis was applied to identify gamma-irradiated garlic powder in Korean barbeque sauce before and after pasteurization (85 °C, 30 min), when blended in different ratios (1%, 3%, and 5%). The sauce sample with nonirradiated garlic powder gave a background glow curve. However, the sample blended with irradiated ingredient (1 and 10 kGy) showed typical TL glow curves at temperatures of 150 to 200 °C. The identification properties of sauce samples were more influenced by blending ratios than by irradiation doses, showing that 3% and 5% added samples produced glow curves at 150 to 250 °C. After pasteurization of the samples containing the irradiated ingredient, TL glow intensity decreased but did not change its shape or temperature range. As a result, the pasteurization of Barbeque sauces containing irradiated ingredients had reduced TL glow intensity, but the shape and temperature range of glow curve were still able to provide information required for confirming irradiation treatment. PRACTICAL APPLICATION: To monitor the irradiated food in international market, thermoluminescence (TL) analysis is considered most promising identification technique because of its sensitivity and long-term stability. In this study the applicability of TL analysis to detect an irradiated ingredient (garlic powder) added in low quantity to a food matrix (sauce) was investigated. The effect of processing (pasteurization) on TL results was also evaluated.     

Effect of Drying Treatment on Physical Identification Characteristics of Irradiated Seasonings

The effect of different drying treatments such as spray drying and vacuum drying on the sensitivity of physical detection methods (photostimulated luminescence (PSL), electron spin resonance (ESR), and thermoluminescence (TL)) was investigated for four types of irradiated seasonings. The slurry feed of each seasoning was exposed to γ-ray irradiation at doses of 0, 5, 10 kGy before being subjected to drying process. Spray drying was applied to beef and soybean seasoning while garlic and broth seasoning were exposed to vacuum drying according to routine protocols adopted in the industry. The samples were analyzed by PSL as a rapid screening method followed by validated methods including ESR spectroscopy and TL analysis. The PSL photon counts drastically dropped in all irradiated samples after both drying processes. No ESR signal was obtained from any of the irradiated seasonings before or after the drying applications. All the irradiated seasoning samples produced typical TL glow curves between the specific temperature range of 150–250 °C. However, the shape, peak, and intensity of TL glow curves were greatly affected particularly after the spray drying treatment. In conclusion, the dry treatment can significantly affect the irradiation detection characteristics in seasoning samples.     

Dose dependence and fading effect of the thermoluminescence signals in γ-irradiated paprika

The thermoluminescence (TL) method can be used to discriminate irradiated and non-irradiated paprika. This study reports the polymineral composition of the dust adhered to paprika; radiation-specific luminescence is emitted by the inorganic material (mainly quartz, feldspars and calcite). On the basis of the shape of the TL curves (or glow curves) some physical parameters are evaluated. Natural TL curves, from non-irradiated samples, show three very low intensity peaks while induced TL curves, from irradiated paprika, seem to consist of five overlapping peaks. TL spectra reveal a very important difference in intensity and in the position of the peaks between irradiated and non-irradiated paprika. Fading observations of TL after irradiation at 5, 10 and 21 kGy, show the same behaviour in all the cases: an initial rapid decay to maintain a certain stability from 300–400 h onwards. © 1998 SCI.     

Effect of gamma irradiation on thermoluminescence emissions from dust of Asian plant nuts

Experiments were conducted to see the effect of irradiation on the thermoluminescence emission from dust of plant nuts such as almond, peanut, pinenut and walnut. Inorganic dust particulate minerals adhering to the nut's surface were collected from unirradiated and irradiated (0.5, 1.0 and 1.5 kGy) samples, and analysed for their thermoluminescence (TL) intensities in the temperature range of 80–320°C at a temperature rate of 10°C/s. It was observed that peaks of the TL signals appeared at 200°C in each case and generally the magnitude of the peak signals of irradiated samples was manifold that of unirradiated controls. Regression and correlation analysis of the data indicated strong relationship between radiation adsorbed dose and TL values at each temperature (r ⪈ 0.96). It was concluded that TL measurements could serve as a fast and reliable method for identifying as well as determining absorbed dose in irradiated plant nuts.     

Thermoluminescence Spectra of Inorganic Dust from Irradiated Herbs and Spices

Thermoluminescence (TL) is used to determine whether certain foodstuffs have been irradiated. A high sensitivity TL spectrometer was used to analyze irradiated and unirradiated inorganic dusts from herbs and spices. Unlike earlier TL work using emissions in the UV-green spectral range, the spectrometer monitored transient TL emissions across the spectral range from UV to infra-red as samples were heated to 400°C. A strong high temperature red emission peak was detected in all irradiated samples. This signal was much higher than the background level, insensitive to post-irradiation light exposure, and has potential for irradiation exposure determination.     

Applicability of thermoluminescence techniques to identify irradiated seafoods using different methods of mineral separation: An interlaboratory blind trial

Thermoluminescence (TL) technique for identifying γ-irradiated (0–10 kGy) anchovies (dried), kelp (dried), and mackerel (fresh) was validated in an interlaboratory blind trial. Different irradiation detection laboratories were involved by using 2 methods of mineral separation (density separation and acid hydrolysis) for the analysis. Key TL parameters, including the TL glow-curve shape, intensity, and the TL ratio (TL₁/TL₂) were used to characterize the irradiation status. All irradiated samples exhibited an intense TL peak at approximately 200°C, which was absent in non-irradiated samples. TL glow curve interpretations were also confirmed by determining the TL ratio. Different participating laboratories reported 89–100% correct results. Both methods of mineral separation were equally effective; however, some variation was observed in the results from different laboratories for irradiated mackerel, which might be due to a lack of isolated minerals, differences in personnel expertise, and different TL instruments.     

Pulsed photostimulated- and thermo-luminescence investigations of γ ray-irradiated herbs

In this study, physical detection methods like pulsed photo-stimulated luminescence (PPSL) and thermoluminescence (TL) were investigated to indentify γ-ray irradiation treatment of some medicinal herbs. Dried herbal samples consisting of root, rhizome, cortex, fruit, seed, flower, spike, ramulus, folium and whole plant of nineteen different herbs were irradiated using a 60Co irradiator at 0–50 kGy. Fifteen non-irradiated control samples had photon counts (PCs) less than the lower threshold value (700 counts/60 s). The photon counts of four non-irradiated samples (roots of osterici, angelica gigas, liriope, and whole plant of taraxaci herba) were between the lower and upper threshold values (700–5000 counts/60 s). However, PCs of all the irradiated samples were found to be higher than the upper threshold value (5000 counts/60 s), clearly screening them out from the non-irradiated ones. Even after 12 weeks of storage PPSL signals of all irradiated samples were observed to be higher than the upper threshold value, making it possible to distinguish them from the non-irradiated control samples. The first TL glow curves (TL₁) for the non-irradiated samples were of very low intensity at about 250–300 °C. Irradiated samples (5–50 kGy) showed a higher peak at around 150–250 °C. TL ratios [ratio of the integrated areas of the first (TL₁) and second (TL₂) glow], measured after re-irradiation for the TL₁-tested samples at 1 kGy, were found to be less than 0.1 for the non-irradiated samples and higher than 0.1 for the irradiated ones. TL ratios for all irradiated samples measured after 12 weeks of storage under dark condition at (23 ± 2 °C) were apparent for distinguishing them from the non-irradiated controls.     

Inter-Laboratory study to define the temperature interval for a thermoluminescence heating unit used to identify irradiated food

EN 1788:2001 suggests defining the temperature range for the thermoluminescence (TL) heating unit to calculate the TL ratio (TL₁/TL₂). In the present study, practical temperature ranges were established by using well-characterized lithium fluoride (LiF, TLD-100®) at 4 different research institutes in Korea. Temperature ranges differed according to models of TLD heating unit, which were wide in the case of RISØ (160–249°C) as compared with Harshaw (155–232°C) TLD readers. The silicate minerals separated from irradiated turmeric samples were measured to check these intervals on a practical basis. The X-ray diffraction (XRD) analysis of separated minerals showed that quartz and feldspar minerals were the main source of well-characterized TL glow curve following irradiation. The TL glow peaks from the separated minerals were narrower in Harshaw than RISØ TLD readers. The TL ratios determined after re-irradiation (1 kGy) for the tested minerals, using the pre-defined temperature intervals, provided the satisfactory results.