首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 937 毫秒
1.
《Food chemistry》2005,91(2):235-240
Decomposition of the pesticide methamidophos was studied in an experiment in field-sprayed grapes of the Soultanina variety. Residues were studied by a simple gas-chromatographic method, using a glass capillary column and NP detector. The decomposition of methamidophos was studied in grapes remaining on the vines after spraying in open and covered vineyards, in grapes harvested and stored in a refrigerated room and in grapes dried into raisins. The recovery of methamidophos was 96.2–112%. The relative standard deviation (RSD) was between 1.4 and 6.2%. The detection limit was 0.02 mg/kg. The results show that, there exists a delayed residue decline during post-harvest storage compared to that for grapes remaining on the vines. From the experimental results, best fit curves were determined and kinetic equations, rate constants and half-lives were calculated. Half-lives found were 16 days for grapes on uncovered vines, 22 days for covered vines and 267 days for grapes stored in a refrigerator. Concentration of methamidophos in raisins was three times higher than that in grapes.  相似文献   

2.
The dissipation of three insecticide flufenoxuron, lufenuron and tebufenozide residues in grapes after field treatments and during the wine-making process was assessed. Residues were determined in grape, must, centrifuged must and wine samples by HPLC-UV after cyclohexane extraction and clean-up on silica-phase cartridges. Vines in vineyards with white and red grapes located in Central Greece were sprayed once with commercial formulations of each insecticide at the recommended doses in experiments carried out in 2004 and repeated in 2006. The insecticide residues in grapes showed slow reduction for a period of 42 days after application following first-order kinetics with dissipation rates ranged from 0.011 to 0.018 mg kg?1 day?1. However, at the recommended pre-harvest interval (PHI) residues did not exceed 0.27 ± 0.03 mg kg?1 for flufenoxuron and lufenuron and 0.68 ± 0.07 mg kg?1 for tebufenozide, and they were clearly lower than the maximum residue limits (MRLs) set by the European Union for grape (2 mg kg?1 for flufenoxuron, 1 mg kg?1 for lufenuron and 3 mg kg?1 for tebufenozide). Grape processing into wine caused an almost complete reduction for flufenoxuron and lufenuron as their residues in wine were below the method LOQs (<0.01 mg l?1), but only a moderate reduction for tebufenozide with concentrations from 0.13 to 0.26 mg l?1 measured in the produced wines. Mean transfer factors for tebufenozide of 0.45 for white 'Roditis' and 0.34 for red 'Cabernet Sauvignon' were found from grapes into wine for the wines processed without maceration. The wine-making technique (with or without maceration) had the same influence on tebufenozide residues in wine. Of the various clarifying agents studied, charcoal was found to be the only one effective in removing tebufenozide residues from wine.  相似文献   

3.
杨韶松  陈静  唐旭兵  罗琳  姚敏 《烟草科技》2012,(4):48-50,66
为了评价“溴氰菊酯”在香料烟中的残留降解行为,进行了连续2年“溴氰菊酯”在香料烟中的残留田间试验.检测结果表明:①2.5%“溴氰菊酯”乳油在香料烟叶中的降解符合一级动力学降解模式,其半衰期为5.80 ~ 6.19 d;②施药后15 d残留量在0.0128 mg· kg-1以下,降解率达95%以上;③按600 mL· hm-2喷施2次和3次2.5%“溴氰菊酯”乳油,15 d后采收,香料烟鲜烟叶中的残留量为<0.01~ 0.4703 mg· kg -1;④2年的气候条件虽然有差异,但“溴氰菊酯”在香料烟中的残留降解行为基本一致.在香料烟的生长过程中,按照推荐用量,在15 d安全间隔期以上,连续3次施用2.5%“溴氰菊酯”乳油,“溴氰菊酯”的残留量不超过0.05 mg· kg-1.  相似文献   

4.
ABSTRACT:  Microwave (MW) vacuum dehydration using temperature to control the level of MW power demonstrated potential in improving the performance of the process. Product surface temperature measured by an infrared temperature sensor was used to control MW power at any level between 0 and 3 kW. Multiple linear regression analysis indicated an r 2= 0.942 for prediction of final moisture content and r 2= 0.985 for prediction of puffed character of grapes based on product temperature, time, specific energy, fresh fruit sugar, and fresh fruit moisture content. Temperature was found to be the most significant predictor. The elemental and compound contents of grapes dried using MW vacuum was compared to sun-dried raisins. The grapes dried using MW vacuum exhibited better preservation. Vitamin A was found in the MW-vacuum-dried grapes but none was detected in the raisins, and Vitamin C, thiamine, and riboflavin were also higher in the MW-vacuum-dried grapes than in the raisins.  相似文献   

5.
Between 1986 and 1988, 306 composite samples of fruit representing eight commodities were collected from farm deliveries to the marketplace in Ontario, Canada. All samples were analysed for insecticides and fungicides. The analysis procedure included tests for organochlorine, organophosphorus, synthetic pyrethroid and methylcarbamate insecticides and dithiocarbamate, dicarboximide and organochlorine fungicides. The commodities tested included apples, blueberries, cherries, grapes, peaches, pears, raspberries and strawberries. In 14% of all fruit samples, pesticide residues were below the detection limits, which ranged between 0.005 and 0.02 mg/kg. A further 14% had total combined pesticide residues below 0.1 mg/kg. Total combined fungicide and insecticide residues ranged from 0.1 to 11 mg/kg in 72% of samples. Six different pesticides were in violation of maximum residue limits (MRL) on 11 (3.6%) of fruit samples. Captan exceeded the 5 mg/kg MRL in five samples and EBDC exceeded the 7 mg/kg MRL in two. Other violations included single fruit samples with dicofol, endosulphan, phosalone and iprodione above the MRL. Raw grapes harvested for wine contained residues of 10 pesticides and the number changed little following the crushing of the grapes; however, fermentation into wine significantly reduced residues. Six insecticides and four fungicides were present on the raw grapes and 4/105 were above the MRL. Following crushing, four insecticides and five fungicides were identified and 4/40 were above the MRL. In wine only three insecticides were identified and all were well below the MRL. Carbaryl appeared to be the most persistent, declining very little between raw grapes and wine.  相似文献   

6.
The main objective of the present work was to dry grapes of Crimson variety through different methodologies in order to find an alternative for the production of raisins. Different methodologies were used for drying: solar direct exposition in a greenhouse and in convective drying chambers with constant air flow at two temperatures: 50 and 60 °C. Some chemical analyses were made, namely for total sugars, acidity, total phenols, total anthocyanins and total tannins. Also some physical properties were evaluated, specifically color and texture. A sensorial analysis of the dried products was undertaken to evaluate the acceptability by consumers. The raisins produced by the different methodologies didn’t show significant differences at the chemical and physical levels. However, it was observed that the dried samples contained higher amounts of total phenolic compounds, anthocyanins and tannins in comparison to the fresh grapes. Sensory evaluation result showed that dried grapes produced using different methodologies was similar to commercial raisins.  相似文献   

7.
Graphite-furnace atomic absorption spectrometric analysis of raisins imported in 1993-95 from different countries into Canada showed that raisins from Turkey had unusually high lead levels. The Turkish raisins ( n =18) contained a mean (range) of 0.93 (0.056- 3.1)mg kg -1 lead, whereas five samples from Australia, South Africa, Iran, Mexico and Chile contained a mean of 0.0085 (0.005-0.010)mg kg -1 . Acid-washing studies showed that most of the lead in the Turkish raisins was on the surface of the fruit. The impact of eating the raisins on the dietary intake of lead was estimated for Canadians of different ages and sexes. For example, eating raisins from Turkey would increase the dietary intake of lead by 1-4-year-old children from 0.97 to ~2.2 μg kg -1 body weightday -1 . The source of the lead was traced to use of a copper fungicide contaminated with high lead levels. Currently, lead levels in raisins imported from Turkey are low and approach levels in raisins from other countries. Uncontaminated raisins contain ~0.01mg lead kg -1 , and a maximum tolerance for lead in raisins of 0.1mg kg -1 is achievable irrespective of the type of raisin or country of origin. Therefore, consideration should be given to proposing this level as a maximum tolerance for lead in raisins.  相似文献   

8.
Ochratoxin A (OTA), hydroxymethylfurfural (HMF) and l ‐ascorbic acid (vitamin C) levels were detected in sun‐dried sultanas and raisins (Vitis vinifera L. cv. Sultanina). Ochratoxins produced by Aspergillus ochraceus, Aspergillus spp., Penicillium viridicatum, Penicillium cyclopium and Rhizophus spp. The main toxin of this group is OTA. It is nephrotoxic and immunotoxic. HMF can occur during nonenzymatic browning reactions that take the form of condensation reactions between amino acids and reducing sugars. It is known as a mutagenic and carcinogenic compound. The sultanas and raisin research samples were sun dried in the field and stored over a long period in the plant. Toxicological quality patterns evaluated for OTA and HMF levels were also evaluated. These are very important compounds for food safety. They are important critical control quality criteria of sun‐dried grapes. Vitamin C was examined because of sensitivity against physical and chemical factors such as oxygen, light, thermal treatments, alkali treatment and heavy metals, as well as being important for food labeling. The mean values of OTA in sultanas and raisins were 4.64 and 2.98 µg/kg, respectively. It is determined that the studied samples could be evaluated for safety limit of OTA, which is suggested by the European Community as 10 µg/kg. The HMF values of the samples were 5.50 and 33.57 mg/kg, respectively. The raisins were sun dried. The two types of samples without any pretreatment had a long sun drying period, and they showed higher mean of HMF level with content is had showed higher mean HMF level sultanas. The HMF content is with a critical control point for human health. The mean vitamin C levels of sultanas and raisins were 3.67 and 5.15 mg/100 g, respectively. The mean vitamin C values of sultanas were lower than those of raisins. It was estimated that alkali treatment could cause the destruction of l ‐ascorbic acid. The vitamin C content of sun‐dried grapes does not contribute much to nutrition.  相似文献   

9.
Aleatico grapes (Vitis vinifera L. cv. Aleatico) picked at 20.4–20.6oBrix were treated with air containing 500 mg/L ethylene for 15 h, or 1 mg/L 1‐MCP (1‐methylcyclopropene) for 15 h, or 1 mg/L 1‐MCP for 15 h + 500 mg/L ethylene for further 15 h, or air (control). All treatments were imposed at 20oC and 95–100% relative humidity. Samples undergoing treatment were then held in air at 20oC and 85% relative humidity for 13 days. Ethylene production from ethylene‐treated grapes was very high (25 μL/kg.h) immediately after treatment, and declined progressively until day 6; 1‐MCP‐ethylene‐treated grapes showed lower ethylene production (10 μL/kg.h). This high ethylene production was mainly due to in‐out diffusion of ethylene absorbed during the treatment, but a potential effect of 1‐MCP is postulated, since 1‐MCP‐treated grapes did not show ethylene production for 2 days after treatment, whereas control grapes produced constant amounts (3–4 μL/kg.h) of ethylene. After day 6, no significant difference was observed among samples. No difference in respiration was revealed. Total phenols were increased significantly by ethylene treatment from 520 mg/L up to 710, while total anthocyanins were lost in air‐treated samples (from 175 mg/L to 120) and remained constant in ethylene and 1‐MCP‐treated grapes. HPLC analyses of anthocyanins confirmed this result: air‐treated samples lost anthocyanins rapidly while this loss was delayed in gas‐treated samples. Terpenols, esters, alcohols, and C6 compounds were increased by ethylene treatment. Conversely, 1‐MCP‐treated grapes showed a significant loss of terpenols and esters, although maintaining alcohols, especially hexan‐1‐ol. Berry pathology was also affected, with 1‐MCP and 1‐MCP‐ethylene treated grapes hosting a diffuse attack of grey mould. Wine analyses revealed higher concentrations of phenols and anthocyanins in wine from ethylene‐treated grapes, although aromatic compounds were lost, and thus the aroma profile of those wines was diminished.  相似文献   

10.
Tempranillo grapes were immersed in solutions of pyrimethanil, metalaxyl, dichlofluanid and penconazol fungicides at different concentrations for several different times. Determinations of the fungicide residues was carried out by GC-NPD, with an additional confirmation by GC-MS. The percentage absorption was determined as well as the distribution between surface, skin and pulp of the grapes. The percentage absorption ranged from 7.2 to 85.5%. These values depended on the time the grapes were in contact with the fungicide solutions. Residues were mainly found in skins, with percentages in skins ranging from 66.3 to 90.3% of total residues. In pulp, these values ranged from 3.5 to 31.0%. The overall methodology was applied to the determination of pyrimethanil in Tempranillo grapes treated with the recommended doses, respecting the safety period. Pyrimethanil residues found in treated grapes were higher in the skin. In grapes collected within the safety period (21 days), the levels found for fungicide residues were below maximum residues levels.  相似文献   

11.
Microwave Pre-treatment for Sun-Dried Raisins   总被引:1,自引:0,他引:1  
Commercial sun-drying of raisins requires a long time, and chemical pretreatments are used to increase the drying rate. The feasibility of improving the sun-drying process of grapes by microwaves was investigated. Sultana seedless grapes, dipped in alkali solution, were pre-treated in a domestic microwave oven and dried by direct solar radiation. Microwave pre treatment reduced the moisture content by 10–20%. The microwave-treated grapes dried nearly two times faster than the controls. Blanching in boiling water had the same effect on the drying rate as microwaves. Color and appearance of treated grapes were comparable to commercial products.  相似文献   

12.
Raisins represent an economically important grapevine by-product. However, their quality is largely dependent on drying techniques and processing conditions. In this context, two drying processes were monitored: hot air drying in a convective oven and greenhouse drying. Grape berries were previously subjected to two chemical pre-treatments (olive oil and K2CO3 emulsion dipping (I) and NaOH solution bleaching (II)). Pre-treated grapes processed using both methods were compared with sun-dried samples. The results show that oven drying was more efficient and rapid (5 days) as compared with greenhouse drying (13 days). The end moisture content of grapes varied from 16.12% to 22.25% on a wet basis in dried samples, respectively. Significant differences in the pH value (3.85–4), acidity (1172.5–2730 mg TA/100 g DW) and total sugars (31.5–49.7%) were also observed, between raisin samples subjected to both treatments and drying methods, whereas protein levels (1–1.25%) were not affected. The analysis of minerals indicates that greenhouse-dried raisins had high amounts of calcium (Ca), magnesium (Mg) and sodium (Na). The highest polyphenol (417.70 mg GAE/100 g DW), flavonoid (115.87 mg CE/100 g DW) and tannin (368.13 mg CE/100 g DW) contents were recorded in sun-dried samples, respectively. The distribution of fungal flora shows a noteworthy variability among raisin samples, with a marked abundance of ochratoxinogenic species such as Aspergillus ochraceus and Aspergillus carbonarius (15.56% and 10.41%, respectively). Italia Muscat raisins processed using oven drying could be an economically interesting alternative to manage the excessive grapes production and consequently solve related marketing issues.  相似文献   

13.
The pyrethroid insecticide permethrin was applied at 2 or 8 mg a.i./kg to wheat, or at 2 mg a.i. permethrin plus 10 mg a.i. piperonyl butoxide/kg to wheat, and the wheat seeds were stored for 20 months under ambient conditions (17–32°C and 40–60% r.h.). Bioassays conducted with adults of Sitophilus oryzae (L) placed on treated wheat samples indicated that all treatments were effective in controlling S. oryzae during storage for at least 20 months. The residues of permethrin and its cis/trans isomers were determined in ground whole wheat and its milling fractions, and the time periods for the initial residue levels to be reduced by half, were evaluated. These ranged from 178 to 200, 217 to 231, and 255 days, in the ground whole grain, bran and flour, respectively. The residues of permethrin in whole ground grain ranged from 1.378 ± 0.190 (day 1) to 0.247 ± 0.026 mg/kg (day 427) in the wheat treated at 2 mg a.i. permethrin/kg, and from 7.400 ± 0.234 (day 1) to 1.294 ± 0.017 mg/kg (day 427) in the wheat treated at 8 mg a.i. permethrin/kg. There was no indication of any effect of piperonyl butoxide on permethrin residue levels. After 35 days of storage 75–80% of permethrin residues were found in the bran portions of seeds subjected to each of the three treatments, while after 427 days of wheat storage at ambient conditions no detectable levels of permethrin residues were found in flour from wheat treated at the rate of 2 mg a.i./kg of wheat.  相似文献   

14.
Snacks are an important part of children's dietary intake, but the role of dried fruit on energy intake in children is unknown. Therefore, the effect of ad libitum consumption of an after‐school snack of raisins, grapes, potato chips, and chocolate chip cookies on appetite and energy intake in twenty‐six 8‐ to 11‐y‐old normal‐weight (15th to 85th percentile) children was examined. On 4 separate weekdays, 1 wk apart, children (11 M, 15 F) were given a standardized breakfast, morning snack (apple), and a standardized lunch. After school, children randomly received 1 of 4 ad libitum snacks and were instructed to eat until “comfortably full.” Appetite was measured before and 15, 30, and 45 min after snack consumption. Children consumed the least calories from raisins and grapes and the most from cookies (P < 0.001). However, weight of raisins consumed was similar to potato chips (about 75 g) and lower compared to grapes and cookies (P < 0.009). Raisins and grapes led to lower cumulative food intake (breakfast + morning snack + lunch + after‐school snack) (P < 0.001), while the cookies increased cumulative food intake (P < 0.001) compared to the other snacks. Grapes lowered appetite compared to all other snacks (P < 0.001) when expressed as a change in appetite per kilocalorie of the snack. Ad libitum consumption of raisins has potential as an after‐school snack to achieve low snack intake prior to dinner, similar to grapes, compared to potato chips, and cookies in children 8 to 11 y old.  相似文献   

15.
Broiler chickens were fed on a commercial diet containing 0.0125% clopidol for 34 days. They were killed 0-10 days after withdrawal of the premedicated feed and clopidol was determined in liver and muscle samples by a sensitive gas-liquid chromatography (g.l.c.) method. During the first two post-withdrawal days the clopidol concentration in the liver decreased rapidly from 7 to 0.5 mg/kg and the level in muscle declined from 3 to 0.1 mg/kg. There was little decline in the clopidol concentrations from days 2 to 10, the levels during this period being 0.2-0.8 mg/kg in liver and 0.05-0.2 mg/kg in muscle. In addition to the above experimental study, liver and muscle samples collected at a Swedish slaughterhouse from broiler chickens raised on clopidol-containing feed were analysed for residues of this drug. Large variations were found in the clopidol levels in broilers from different producers. The levels in the liver ranged from 0.05 to 8.0 mg/kg and those in muscle from 0.03 to 3.5 mg/kg. The present results emphasize the need to carry out field studies to check the levels of feed additive residues in edible tissues from chickens.  相似文献   

16.
目的建立用于葡萄中苯醚甲环唑、己唑醇和咪鲜胺残留检测的分析方法。方法葡萄样品先经乙腈和水提取,盐析后取上清液进行水解并测定。通过优化前处理及色谱条件,建立色谱分析方法,结合目标物标准曲线进行定量分析。结果经过3个水平的加标回收实验,所建立方法的平均回收率在79%~102%,相对标准偏差0.5%~6.9%(n=5)。苯醚甲环唑和己唑醇的最低检出浓度为0.01 mg/kg,2,4,6-三氯苯酚的最低检出浓度为0.2 mg/kg。结论所建立的分析方法操作简便,分离净化效果良好,显著提高前处理效率,灵敏度、准确度和精密度均达到农药残留检测要求。  相似文献   

17.
Euparene (N1,N1-dimethyl-N-phenyl-fluorine-dichlormethylthiosulfamide) is a highly effective fungicide used in controlling a number of fungus infections affecting grapes and strawberries. Following chemical treatment it is found on these agricultural crops both as a starting product and in the form of its metabolite (N1,N-dimethyl-N-phenyl diamide sulfide), whose residual quantities exceed, at times, those of the original compound itself. The organoleptic properties of grapes change with the content of the above substances of not less than 10 mg/kg. Euparene belongs to the category of compounds with little and medium-toxic and moderately pronounced cumulative properties (LD50 for rats -- 4630 mg/kg, for mice -- 1905 mg/kg, for guinea pigs -- 805 mg/kg. Cummulation coefficient with introduction of 1/20 LD50: for mice -- 3.7, for guinea pigs -- 3.3). In a chronic 10-month long experiment the threshold dose of the preparation was set at a level of 5.4 mg/kg, and subliminal -- at 1.6 mg/kg. The metabolite proved to be somewhat more toxic, but less cumulative than euparene (LD50 for mice -- 820 mg/kg, cumulation coefficient -- over 5). The permissible residual concentration (PRC) of euparene and its metabolite in grapes is recommended at a level of 1.3 mg/kg (total), while in strawberries it is not permitted at all. In the case of grapes the "expectation time" should be 30 days with the consumption of the preparation of up to 3 kg per hectar and in that of strawberries -- 15 days and its consumption of up to 1.2 kg/he.  相似文献   

18.
A high-performance liquid chromatography (HPLC) method was developed to determine dehydroacetic acid (DHA) residues in chicken muscle, liver and kidney. DHA was extracted using acetonitrile, and clean-up performed using a strong anion exchange (PAX) SPE column. The cleaned-up samples were separated by HPLC with a C18 column and determined at 290 nm. Extraction recoveries of DHA from samples fortified at 0.5-5 mg/kg levels ranged from 88.2% to 93.9% in muscle, 83.8% to 86.6% in liver and 83.8% to 89.8% in kidney, with coefficients of variation <6.44%. The limit of detection was 0.05 mg/kg and limit of quantification was 0.2 mg/kg. DHA was not detectable in muscle at 13-15 days after final administration of DHA, at 11 days in kidney and 17 days in liver. The method described herein is suitable for routine quantitative analyses of DHA in animal tissues and can be easily applied to the analysis of other matrices such as milk, serum and tissue samples from other animals.  相似文献   

19.
[目的] 明确党参初加工过程中多菌灵、三唑酮、戊唑醇、咪鲜胺和苯醚甲环唑5种农药残留变化情况。[方法] 通过实验室浸泡法模拟农药污染试验,采用超高效液相色谱-串联质谱法(UHPLC-MS/MS)检测经过清洗、水煮和干燥3种初加工过程后,多菌灵、三唑酮、戊唑醇、咪鲜胺和苯醚甲环唑在党参中的残留量。[结果] 结果表明,清洗后党参中农药残留量降低至0.04~0.76 mg/kg,去除率达18.0%~87.9%,加工因子(PF)在0.12~0.79之间,以2%的小苏打水清洗效果最佳。水煮后残留浓度降低至0.069~0.64 mg/kg,去除率达18.6%~67.1%,PF在0.35~0.84之间,以水煮3 min处理对5种农药残留去除效果较好。党参中5种农药残留量在经干燥后残留量在0.27~1.22 mg/kg之间,PF值范围为1.86~4.10,比干燥前增加了44.3%~74.7%,不同温度下的农药残留量大小顺序为50 ℃>40 ℃>60 ℃。不同加工过程对5种农药的去除效果强弱顺序依次为:清洗>水煮>干燥。[结论]党参以2%小苏打水清洗,水煮时间为3 min,烘干温度为60 ℃进行加工,农药残留去除效果最佳;实验结果为有效预防农药残留对生产的影响提供技术支撑,对保障食品安全具有重要意义。  相似文献   

20.
The introduction of live insects into human food is rare in developed countries. However, we report, for the first time, an emerging risk that exists from dried fruit in Central Europe. Recently, massive and frequent infestation of dried fruit imported from the Mediterranean region by the mite, Carpoglpyhus lactis L. (Acarina: Carpoglyphidae), has been found. In 180 samples taken from supermarkets, 13% were contaminated; the contamination levels ranged from 0 to 660 mites per g of dried fruit. The contamination was found in dried apricots, figs, plums and raisins. To estimate the risks and food preferences of C. lactis, its growth rate was examined under laboratory conditions. Starting with a hypothetical population of 10 mites per g of dried fruit, the risk level of 1000 mites per g of dried fruit is reached at 42 days for dried figs, 49 days for dried pineapple and 63 days for dried apricots, dates and plums at 25 °C and 85% relative humidity. We found that mites are able to enter every dried fruit packing material tested, including polypropylene and aluminum foils. This indicates that mites can move from package to package in supermarkets. Mites are known as allergen producers and vectors of mycotoxin-producing fungi. These findings indicate that an increased risk of C. lactis contamination exists in dried fruit.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号