辐照对大麦发芽的影响

该文介绍了3个品种的大麦干种子经Co60辐照后的发芽情况。结果表明,在0kGy~3kGy低剂量辐照下,对相同品种大麦辐照的发芽率几乎没有影响,影响大麦发芽率的因素主要为大麦的质量,而不是辐照。     

Effect of gamma irradiation on flavonoids in strawberries

In unirradiated strawberries, in addition to ellagic acid, five flavonoids were identified by comparison to standards by reversed-phase chromatography with diode-array detection: (+)-catechin, (-)-epicatechin, kaempferol-3-glucoside, quercetin-3-glucoside and quercetin-3-galactoside. Four others were classified on the basis of UV spectra: two as kaempferol-, one as quercetin- and one as ellagic acid derivatives. Whereas the concentrations of the quercetin- and ellagic acid derivatives were not affected by irradiation, those of the catechin and kaempferol components diminished noticeable. The most significant reduction as a function of dose was found for (+)-catechin, followed by kaempferol-3-glucoside and (-)-epicatechin. Their decreases are, however, in the same order of magnitude as the variation of their concentrations in different harvests and varieties. For two as yet unclassified compounds, characteristic changes upon radiation were observed. The level of one of them is almost quintupled at a dose of 6 kGy.     

Effect of surface sterilization, fumigation and gamma irradiation on the microflora and germination of barley seeds.

Sodium hypochlorite (NaOCl) and mercuric chloride (HgCl2) surface sterilization, methyl bromide and propylene oxide fumigation and gamma irradiation treatments were compared for their effectiveness in killing microorganisms on or within barley seeds. Surface sterilization with 12.5, 25 or 50% (v/v) NaOCl for 5, 15 or 30 min, decreased Fusarium spp., Epicoccum purpurascens, and Bacillus spp. but did not kill Alternaria alternata. However, surface sterilization with 0.1 or 0.2% (w/v) HgCl2 for 3 min significantly decreased A. alternata, Fusarium spp. and E. purpurascens but Bacillus spp. were only killed by 0.3% (w/v) HgCl2 used for 10 min, which also decreased seed germination. Aspergillus flavus inoculated onto barley seeds as spores, was completely killed by surface sterilization with NaOCl but not with HgCl2, while Fusarium culmorum was killed by both NaOCl and HgCl2 treatments. Fumigation with methyl bromide yielding a concentration-time product of 3000 mg h l-1 or with propylene oxide giving a concentration-time product of 2400 mg h l-1 eliminated all filamentous fungi but Bacillus spp. and yeasts survived, and both treatments adversely affected seed germination. Gamma irradiation at a dose of 4 kGy eliminated most Alternaria, Fusarium and Epicoccum spp. but a dose of 12 kGy was required to kill Bacillus spp., yeasts and Aureobasidium pullulans. Germination was improved slightly up to a dose of 8 kGy but gradually decreased with increase in dosage to 15 kGy of gamma irradiation.     

Effect of gamma irradiation and water activity on mycotoxin production of Alternaria in tomato paste and juice

Gamma-irradiation, water activity (aw) and incubation temperature were found to affect the production of tenuazonic acid (TZA) by Alternaria alternata in tomato paste and juice. By increasing the irradiation doses, the dry weight as well as TZA decreased greatly until complete inhibition at 4 kGy. Greatest production of TZA occurred at 0.98 aw (57.5 micrograms/g and 26.3 micrograms/g) for both tomato paste and juice, respectively, at 25 degrees C. Changing temperature and aw altered the relative amounts of TZA produced in tomato paste und juice by unirradiated and irradiated conidia of A. alternata. Only trace amount of TZA was detected at 0.98 aw (1.50 micrograms/g) by 3 kGy-irradiated conidia in tomato paste, while it was inhibited completely in juice. Increasing gamma-irradiation doses and decreasing water activities decreased greatly or inhibited TZA production in both tomato paste and juice.     

Effect of some food preservatives on aflatoxin production.

The effect of some food preservatives, such as sorbic (SA) and propionic (PA) acids, on aflatoxin production in synthetic media or in moistened (20%) wheat seeds, was investigated. The preservatives tested, added to synthetic media at sublethal concentrations both at the inoculum and after 5 days of incubation, stimulated aflatoxin production by Aspergillus parasiticus. Sorbic and propionic acids are metabolized by the fungus in vivo and in vitro. Lower concentrations of PA and SA (0.05 to 0.1% w/w) in wheat seeds are ineffective against both fungal growth and aflatoxin production, whilst the combined use of butylated hydroxy toluene (BHT), and PA or SA was more effective in controlling aflatoxin production than their use as single components.     

紫外照射去除黄曲霉毒素工艺对花生油品质的影响

以花生油为原料,选取酸值、碘值、过氧化值、氧化稳定性、维生素E及反式脂肪酸含量等参数作为检测指标,研究不同紫外照射剂量下,紫外线去除花生油中黄曲霉毒素B1(AFB1)工艺对花生油品质的影响.结果表明:在去除花生油中黄曲霉毒素B1的有效照射剂量范围内,花生油的质量指标除过氧化值显著增加(在国标范围内)外,其他并无变化.紫外照射技术用于去除花生油中黄曲霉毒素不仅有效,而且对花生油品质无影响.     

Preliminary studies of the effects of heat and gamma irradiation on the production of aflatoxin B1 in static liquid culture,by Aspergillus flavus link NRRL 5906

Aflatoxin B₁ production by a strain of Aspergillus flavus NRRL 5906 was examined in static liquid culture in maize meal broth (MMB) and maize meal broth supplemented with 2% glucose and 2% peptone (AMMB). Erlenmeyer flasks were inoculated with 1.0 ml aliquots of fungal spores which had been heat-treated (60°C for 30 min) under low humidity (< 45% R.H. dry heat) or high humidity conditions (>85% R.H., moist heat) followed by gamma irradiation with either 0.0, 3.5 or 4.0 kGy. AMMB supported 6–17 times more vegetative growth (depending on the heat and dose combination) than spores incubated in MMB alone. High inoculum size of control unheated spores (log CFU/g, 6.9) yielded the least aflatoxin B₁ in flasks containing AMMB (8.2–19.3 μg/ml). A dose of 3.5 kGy reduced by 3.2–3.8 log cycles the viable inoculum of control unheated spores, resulting in 2–5 fold increase in aflatoxin B₁ formed in flasks containing AMMB. Increasing the applied load to 4.0 kGy, however, reduced aflatoxin B₁ levels formed in AMMB to similar or lower levels than found in flasks inoculated with control unirradiated spores. Combination treatment of A. flavus with dry heat and 3.5 kGy reduced the spore inoculum size by about 4 log cycles and yielded the highest amount (41.1 μg/ml) of aflatoxin B₁ in AMMB. However, moist heat treatment of spores receiving the same dose (3.5 kGy) reduced toxin level formed by 25%. Aflatoxin B₁ formation by A. flavus spores incubated in AMMB was completely prevented by a combination treatment of moist heat and 4.0 kGy of gamma irradiation. This same treatment attenuated aflatoxins B₂, G₁ and G₂ production which are formed with B₁ by A. flavus NRRL 5906. Spores raised in all flasks containing MMB did not form aflatoxin except when the medium MMB was autoclaved twice at 121°C for 15 min.     

Effects of gamma irradiation on aflatoxins

The effects of gamma irradiation on a mixture of aflatoxins B1, B2, G1, G2 were studied. Standard solutions of A and B were irradiated at 5, 10, and 20 kGy in a solution of water/DMSO (9 + 1, v/v) by using a 137Cs source. The control (0 kGy) and irradiated samples were subjected to RP-HPLC analyses with methanol/water (4 + 5, v/v) as the mobile phase. Aflatoxin B1 (AFB1) was the most radio-sensitive of the four compounds. The radiosensitivity of the other aflatoxins, was in increasing order: G2, B2, G1. Only about 5% of AFB1 remained after irradiation of solution A at 5 kGy. When the concentration of solution B was increased two-fold, trace amounts of AFB1 remained after irradiation doses of 10 and 20 kGy. Irradiation was found to be suitable for the destruction of aflatoxins in solution.     

Effects of gamma irradiation on aflatoxins

Summary The effects of gamma irradiation on a mixture of aflatoxins B₁, B₂, G₁, G₂ were studied. Standard solutions of A and B were irradiated at 5, 10, and 20 kGy in a solution of water/DMSO (9+1, v/ v) by using a¹³⁷Cs source. The control (0 kGy) and irradiated samples were subjected to RP-HPLC analyses with methanol/water (4+5, v/v) as the mobile phase. Aflatoxin B₁ (AFB₁) was the most radio-sensitive of the four compounds. The radiosensitivity of the other aflatoxins, was in increasing order: G₂, B₂, G₁. Only about 5% of AFB₁ remained after irradiation of solution A at 5 kGy. When the concentration of solution B was increased two-fold, trace amounts of AFB₁ remained after irradiation doses of 10 and 20 kGy. Irradiation was found to be suitable for the destruction of aflatoxins in solution.

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Einfluß von Gammastrahlung auf die Aflatoxine

Zusammenfassung Der EinfluB von -Strahlen auf die Aflatoxinmischung B₁, B₂, G₁ und G₂ wurde untersucht. Standardlösungen A und B wurden mit -Strahlung von 5; 10; bzw. 20 kGy in der Lösung von Wasser/DMSO (9+1, v/v) unter Verwendung einer¹³⁷Cs-Quelle bestrahlt. Kontroll(0 kGy)-und bestrahlte Proben wurden der RP-HPLC Analyse unter Verwendung von Methanol/Wasser (4+5, v/v) als mobile Phase unterworfen. Aflatoxin B₁ (AFB₁) war die strahlenempfindlichste von den vier, die Strahlenempfindlichkeit der anderen Aflatoxine nahm bei 5 kGy in der Reihenfolge: G₂, B₂, G₁ zu. Nur ca. 5% von AFB₁ ist nach der Bestrahlung üibriggeblie-ben. Wenn sich die Konzentration zweifach erhöht (Lösung B), ist von AFB₁ nur eine Spur nach der 10 kGy- und 20 kGy-Bestrahlung übriggeblieben. Es wurde gefunden, daß die Bestrahlung zur Zerstörung der Aflatoxine in der Lösung geeignet ist.

     

Effect of gamma irradiation on Listeria monocytogenes in frozen,artificially contaminated sandwiches

Gamma irradiation has been shown to effectively control L monocytogenes in uncooked meats but has not been extensively studied in ready-to-eat foods. The presence of Listeria in ready-to-eat foods is often due to postprocess contamination by organisms in the food-manufacturing environment. Because gamma irradiation is applied after products are packaged, the treated foods are protected from environmental recontamination. Currently, a petition to allow gamma irradiation of ready-to-eat foods is under review by the Food and Drug Administration. This study was conducted to determine if gamma irradiation could be used to control L. monocytogenes in ready-to-eat sandwiches. Ham and cheese sandwiches were contaminated with L. monocytogenes, frozen at -40 degrees C, and exposed to gamma irradiation. Following irradiation, sandwiches were assayed for L. monocytogenes. A triangle test was performed to determine if irradiated and nonirradiated sandwiches differed in sensory quality. We found that the D10-values ranged from 0.71 to 0.81 kGy and that a 5-log reduction would require irradiation with 3.5 to 4.0 kGy. The results of a 39-day storage study of sandwiches inoculated with 10(7) CFU of L monocytogenes per g indicated that counts for nonirradiated sandwiches remained fairly constant. Counts for sandwiches treated with 3.9 kGy decreased by 5 log units initially and then decreased further during storage at 4 degrees C. Sensory panelists could distinguish between irradiated and nonirradiated sandwiches but were divided on whether irradiation adversely affected sandwich quality. Our results suggest that manufacturers of ready-to-eat foods could use gamma irradiation to control L. monocytogenes and improve the safety of their products.     

Effect of electron-beam irradiation on the safety and quality of Fusarium-infected malting barley

Utilization of Fusarium-infected barley for malting may lead to mycotoxin production during malting and decreased malt quality. Electron-beam irradiation may prevent safety and quality defects and allow use of otherwise good quality barley. We evaluated electron-beam irradiation for preventing Fusarium growth and mycotoxin production while maintaining barley-malt quality characteristics. Four barley lots with varying deoxynivalenol (DON) concentrations were irradiated at 0, 2, 4, 6, 8, and 10 kGy. Treated barley was malted in a pilot-scale malting unit. Barley and malt were analyzed for Fusarium infection (FI), germinative energy (GE), aerobic plate counts (APC), mold and yeast counts (MYC), and DON. Malt quality parameters included malt extract, soluble protein, wort color, wort viscosity, free amino nitrogen, alpha-amylase, and diastatic power. FI, APC, and MYC decreased in barley with an increase in dosage. The APC and MYC for malts from barley exposed to 8–10 kGy were slightly higher than in other malted samples indicating that irradiation-resistant microflora could flourish during malting. Barley GE significantly decreased (3–15%) at 8–10 kGy. Although irradiation had no effect on DON in raw barley, DON decreased significantly (60–100%) in finished malts prepared from treated barley (6–10 kGy). Malt quality parameters were slightly affected by electron-beam radiation. The results suggest 6–8 kGy may be effective for reducing FI in barley and DON in malt with minimal effects on malt quality.     

Effect of anilinopyrimidine resistance on aflatoxin production and fitness parameters in Aspergillus parasiticus Speare

Mutants of Aspergillus parasiticus resistant to the anilinopyrimidine fungicides were isolated at a high mutation frequency after UV-mutagenesis and selection on media containing cyprodinil. In vitro fungitoxicity tests resulted in the identification of two predominant resistant phenotypes that were highly (R₁-phenotype) and moderately (R₂-phenotype) resistant to the anilinopyrimidines cyprodinil, pyrimethanil and mepanipyrim. Cross-resistance studies with fungicides from other chemical groups showed that the highly resistance mutation(s) did not affect the sensitivity of R₁-mutant strains to fungicides affecting other cellular pathways. Contrary to that, a reduction in the sensitivity to the triazoles epoxiconazole and flusilazole, the benzimidazole carbendazim, the phenylpyrrole fludioxonil, the dicarboximide iprodione and to the strobilurin-type fungicide pyraclostrobin was observed in R₂-mutant strains. Study of fitness parameters of anilinopyrimidine-resistant strains of both phenotypic classes showed that all R₁ mutant strains had mycelial growth rate, sporulation and conidial germination similar to or even higher than the wild-type parent strain, while these fitness parameters were negatively affected in R₂ mutant strains. Analysis of the aflatoxin production showed that most R₁ mutant strains produced aflatoxins at concentrations markedly higher than the wild-type parent strain. A considerable reduction in the aflatoxin production was observed on cultured medium and on wheat grains by all R₂ mutant strains, indicating a possible correlation between fitness penalties and aflatoxigenic ability of A. parasiticus. The potential risk of increased aflatoxin contamination of agricultural products and their byproducts by the appearance and predominance of highly aflatoxigenic mutant strains of A. parasiticus resistant to the anilinopyrimidines is discussed.     

Effect of gamma irradiation on the texture and microstructure of chicken breast meat

This study investigated the textural and microstructural properties of chicken breast meat exposed to gamma irradiation ((60)Cobalt) and stored at 4?°C. Textural properties of the irradiated (n=27) and unirradiated chicken breasts (control) were determined by measuring shear force and cooking loss at day 0 and at 2-day intervals for a 14-day refrigerated storage period. In addition, microstructural changes of the irradiated and unirradiated chicken breasts were compared. Irradiated chicken breasts had more cooking loss and higher (P<0.0001) shear force than unirradiated chicken breasts. Transmission electron microscopy showed significant differences (P<0.0001) in size of myofibril units (sarcomeres) between irradiated and unirradiated breast. Shrinkage in sarcomere width (myofibril diameter) and disruption of myofibrils in irradiated breast meat were also noticed when compared with unirradiated breast meat.     

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.     

Effect of gamma irradiation on microbial growth and sensory quality of fresh-cut lettuce

Fresh-cut lettuce was irradiated and microbiological and sensory quality was examined during storage at 4 degrees C. Experimental results showed that the number of aerobic mesophilic bacteria on fresh-cut lettuce irradiated with 1.0 kGy was reduced by 2.35 logs and sensory quality was maintained best during storage for 8 days at 4 degrees C. It was indicated that Gompertz model could predict the bacterial number on fresh-cut lettuce if the initial level was known.     

Correlation of growth and aflatoxin production by Aspergillus flavus with some essential metals in gamma irradiated crushed corn

The effects of gamma irradiation and some essential metals on growth and aflatoxin B1 production by Aspergillus flavus in crushed corn were investigated. The production of aflatoxin by A. flavus was influenced by the addition of zinc, copper or iron and the effect gradually decreased with increasing metal concentration from 0 to 300 ppm. A. flavus grew and depleted zinc, copper and iron at initial concentration of 100, 200 or 300 ppm. Presence of 100 ppm zinc, copper or iron plus gamma irradiation (0.5, 1.0, 2.0 kGy) enhanced the growth of A. flavus and the production of aflatoxin in contrast with irradiated samples alone. A. flavus was able to metabolize and deplete elements in all gamma-irradiated samples. These results suggest that stricter control of element levels in gamma irradiated grains could control aflatoxin contamination.     

Effect of controlled atmosphere storage on aflatoxin production in high moisture peanuts (groundnuts)

Shelled peanuts (groundnuts) remoistened to 16.7% were stored for 4 weeks at about 27°C in air (0.03% CO₂, 21% O₂, 78% N₂) and in three modified atmospheres: (1) 13.6% CO₂, 0.3% CO, 0·6% O₂, 84.7% N₂; (2) 12.2% CO₂, 3.1% CO, 0.3% O₂, 83.5% N₂; and (3) 13.6% CO₂, 0.1% CO, 1.5% O₂, 83.9% N₂. Aflatoxins, per cent free fatty acids, and per cent kernel infection by the Aspergillus flavus group were determined weekly. Peanuts in air and in the atmosphere containing 1.5% O₂ accumulated high levels of aflatoxin in 1 and 2 weeks, respectively. In the other two controlled atmospheres aflatoxin B₁ did not exceed 21 μg/kg and the per cent of free fatty acids increased only slightly. None of the treatments eliminated infection by the A. flavus group. After 4 weeks peanuts in all treatments had visible fungal growth on surfaces.