普洱茶中有机磷类农药残留的测定

为建立气相色谱技术同时测定茶叶中多种有机磷农药残留的方法,并用该方法检测来自云南省5 个普洱茶主产区的30 个普洱茶样品中的有机磷农药残留量,为其安全性评价提供科学数据。样品以乙酸乙酯为提取剂经超声波萃取,提取液用活性炭小柱净化,采用气相色谱火焰光度检测器检测,外标法定量。该方法在3 个添加水平下,9 种组分的平均回收率为71.1%～113.8%,相对标准偏差为0.9%～13.3%。方法的检测限为1.0～2.5μg/kg。普洱茶样品检出的农药有敌敌畏、乙酰甲胺磷、乐果、杀螟硫磷、马拉硫磷、喹硫磷、三唑磷,其中杀螟硫磷和乐果的检出率较高,但含量均低于欧盟限量标准。从茶叶中有机磷农药残留量来看,普洱茶具有较高的食用安全性。     

英德横石水镇贫困村蔬菜中农药残留及重金属污染分析

本文研究分析了英德横石水镇溪北村蔬菜中的农药残留和重金属污染。选取24个蔬菜样品,采用气相色谱-双火焰光度检测器(GC-FPD)测定蔬菜中的甲胺磷、甲拌磷、特丁硫磷、甲基对硫磷、杀螟硫磷、甲基异柳磷、丙溴磷、伏杀硫磷、敌敌畏、乙酰甲胺磷、治螟磷、氧乐果、乐果、毒死蜱、马拉硫磷、对硫磷、水胺硫磷、杀扑磷、三唑磷和亚胺硫磷等20种有机磷农药残留;采用气相色谱-电子捕获检测器(GC-ECD)测定蔬菜中的α-六六六、β-六六六、γ-六六六、δ-六六六、百菌清、三唑酮、甲氰菊酯、哒螨啉、氯氰菊酯、氰戊菊酯、溴氰菊酯和氟虫腈等12种农药残留;采用原子吸收-石墨炉法测定铅含量;原子荧光分光光度法测定砷和汞含量,结果表明蔬菜样品中均未检出上述32种农药及3种重金属。研究结果可为英德横石水镇溪北村蔬菜质量定位提供理论依据。     

同时测定蔬菜中15种有机磷农药的残留方法

了解当前本市农产品市场中关于蔬菜中有机磷农药残留的相关状况,制定相关对策,建立一种适用于多种有机磷农药快速检测的气相色谱方法。根据农药的相关性质,该气相色谱法可同时检测15种有机磷农药,其中包括:敌百虫、敌敌畏、甲胺磷、乙酰甲胺磷、灭线磷、甲拌磷、氧乐果、特丁硫磷、乐果、甲基对硫磷、马拉硫磷、杀螟硫磷、对硫磷、倍硫磷、水胺硫磷。通过对不同型号色谱柱的选择、柱温箱升温程序的控制,实现对15种常见有机磷农药的快速、便捷、准确度好的定性和定量的分析。     

活性白土在青菜有机磷农药检测中的研究

目的筛选对青菜基质成分净化效果最好的吸附剂,并探究其对气相色谱检测青菜中有机磷农药的影响。方法青菜经乙腈提取后,用6种吸附材料分别进行基质成分净化,利用紫外-可见光光谱图分析筛选对青菜基质成分净化效果最好的吸附剂,并考察其加入量对净化效果的影响;通过比较加标回收率,考察该吸附材料对青菜中有机磷农药检测准确度的影响。结果活性白土和石墨化碳黑能显著降低青菜提取液在436 nm和668 nm附近的吸光度。在气相色谱检测中,随着活性白土加入量的增大,敌敌畏、灭线磷、毒死蜱、杀螟硫磷、三唑磷的回收率逐渐减小,甲胺磷、乙酰甲胺磷、久效磷、氧乐果、乐果的回收率先降低后升高。结论活性白土对青菜的基质成分净化效果好,但也对农药具有较强的吸附作用,其在农药残留检测中的应用还有待进一步研究。     

气相色谱-质谱法同时检测饮用水中6种常见农药残留

建立了测定饮用水中的微量敌敌畏、治螟磷、乐果、二嗪磷、甲基对硫磷、杀螟硫磷残留的气相色谱-质谱法检测方法。饮用水样经固相萃取柱富集,以乙酸乙酯洗脱,经气相色谱质谱联用仪定性定量检测。敌敌畏、治螟磷、乐果、二嗪磷、甲基对硫磷和杀螟硫磷的质量浓度在0.01~5.0μg/mL范围内与其色谱峰面积均呈良好线性关系,线性相关系数不低于0.995,敌敌畏、治螟磷、乐果、二嗪磷、甲基对硫磷和杀螟硫磷的检出限分别为0.01,0.01,0.01,0.005,0.005和0.01 mg/kg。敌敌畏、治螟磷、乐果、二嗪磷、甲基对硫磷和杀螟硫磷测定结果的相对标准偏差均小于5%(n=6),重现性均小于10%(n=6),加标回收率在80%~100%之间。试验证明该方法具有操作简单、准确度高、灵敏度高等优点。     

固相萃取-气相色谱法测定果汁中多种农药残留

目的 建立QuEChERS提取盐包及固相萃取净化技术结合气相色谱法测定果汁中17种农药(敌敌畏、甲胺磷、乙酰甲胺磷、甲拌磷、氧乐果、乐果、毒死蜱、杀螟硫磷、水胺硫磷、三唑磷、联苯菊酯、甲氰菊酯、氯氟氰菊酯、氯氰菊酯、氟氰戊菊酯、氰戊菊酯、溴氰菊酯)残留的分析方法。方法 果汁样品经乙酸乙酯及QuEChERS提取包提取, 提取液通过石墨化碳黑净化, 以气相色谱火焰光度检测器(flame photometric detector, FPD)、电子捕获检测器(electron capture detector, ECD)检测, 外标法定量。结果 10种有机磷农药在0.020~0.15 mg/L及7种拟除虫菊酯类农药在0.01~0.1 mg/L浓度范围内线性关系良好(r2≥0.9991), 方法的检出限(limits of detection, LOD)均在0.023 mg/kg以下, 平均加标回收率为72.7%~115.0%之间, 相对标准偏差(relative standard deviation, RSD)均小于5.84%。结论 本方法具有灵敏、简便、稳定, 可以满足果汁样品中多种农药残留的检测要求。     

气质法测定大棚土壤中的9种有机磷农药

建立气相色谱质谱法检测大棚蔬菜种植土壤中的9种有机磷类(毒死蜱、氧乐果、乙酰甲胺磷、马拉硫磷、乐果、甲基对硫磷、二嗪磷、三唑磷、治螟磷)农药的检测方法。样品经冰乙酸-乙腈溶液匀浆提取后,提取液经N-丙基乙二胺(PSA)、无水硫酸镁和C_(18)进行分散萃取净化,浓缩后用丙酮定容至1 mL。经气相色谱-质谱仪定性定量检测,基质标准定量。结果表明, 9种有机磷类农药在0.05～5μg/m L范围内线性关系良好, R~2均小于0.995;当加标浓度为0.5, 1.0和3.0 mg/kg时,得到的回收率范围为83.2%～98.2%;检出限为0.006～0.020 mg/kg;精密度RSD(n=6)为1.54%～4.23%。     

食品安全抽检环节芹菜中10种有机磷农药的残留降解规律研究

目的研究食品安全抽检环节芹菜中10种有机磷农药的残留降解规律。方法以芹菜为基质,选择10种有机磷农药(乐果、毒死蜱、甲基对硫磷、杀螟硫磷、甲基异柳磷、喹硫磷、水胺硫磷、杀扑磷、三唑磷、伏杀硫磷)作为研究对象,采用加标后均质的制样方法制备样品,将农药残留检测结果通过拟合一级动力学模型预测农药的降解半衰期,研究抽检样品在不同储存条件(常温、冷藏和冷冻)下10种农药降解规律。结果在常温条件下半衰期平均为2.9 d;冷藏条件下平均为4.4 d;除甲基异柳磷和喹硫磷外,冷冻条件下半衰期平均为26.9 d;在10种有机磷中,喹硫磷在各种储存条件下半衰期较长,说明相对稳定;伏杀硫磷半衰期较短,容易降解。结论通过对不同储藏条件下芹菜中10种常用有机磷农药降解规律的研究,为因农药自身降解造成的初检结论被推翻的情况提供理论研究。     

茶叶中有机磷农药残留测定方法的改进

茶叶是我国一种重要的出口经济作物,我国的茶叶产量居首位,茶叶的质量对于保障人类健康、促进我国经济增长具有重要作用,但近些年来,茶叶中残留农药问题造成的茶叶质量不合格问题时有发生。基于此,文章建立了一种简便快速测定方法,能够对茶叶中残留的七种有机磷农药敌敌畏、乐果、毒死蜱、甲基对硫磷、马拉硫磷、杀螟硫磷、三唑磷进行测定,以期为茶叶中有机磷农药残留测定方法的改良提供理论支持。     

气相色谱法同时测定果酱中多种有机磷农药残留

提出同时测定果酱中甲胺磷、敌敌畏、氧乐果、马拉硫磷、毒死蜱、水胺硫磷、喹硫磷七种有机磷农药残留的检测方法。在选定的色谱条件下,添加浓度在0.01～1.00mg/kg之间时七种有机磷农药的平均回收率(n=6)在82.0%～97.0%之间,相对标准偏差分别为1%～5%,方法的最低检出限(七种有机磷农药)均设为0.01mg/kg,结果显示该方法具有快速、简单、准确、灵敏度高的特点,能满足日本肯定列表的检测要求。     

小青菜在不同相对湿度条件下的失水性研究

为探讨相对湿度对果蔬失水的影响,利用恒温恒湿箱,在不同相对湿度下对小青菜进行了定量的失水性实验研究。通过对小青菜比表面积的测量,表明质量在18～28g之间的小青菜的比表面积可以看作一个定值,约为2.07m2/kg。同时,在40%、80%与99.9%相对湿度下比较了小青菜的相对失水率、失水率,结果表明:小青菜的失水率在某一时段内均有一个增大的过程,但出现时间有所差异;40%与80%之间的相对失水率差异不如80%与99.9%之间的差异明显,表明提高相对湿度能明显改善小青菜的耐藏性。此外,还对小青菜外层叶片的失水性进行了研究,结果表明:在贮藏前期,增大小青菜暴露率会加剧其水分损失。     

The effect of LED irradiation on the quality of cabbage stored at a low temperature

The effects of light emitting diode (LED) irradiation on maintaining freshness and nutrition in cabbage during low temperature storage were investigated. Cabbage, ‘Dongdori’ was stored at 4–5°C for 18 days under white, green, blue, and red LED light. On day 15 of storage, the total chlorophyll content of cabbage was highest for green, followed by white, red, blue, and a nonirradiated control group. The vitamin C content was highest for blue, followed by white, green, red, and the control. On day 18 of storage, the total polyphenolic content in cabbage was highest for blue followed by white, red, green, and the control. LED irradiation is effective for enriching the chlorophyll, vitamin C, and polyphenol contents of cabbage stored at a low temperature and results suggest that LED colors have different effects.     

Molecular weight distribution and viscosity of water-soluble dietary fibre isolated from green beans,brussels sprouts and green peas following different types of processing

The molecular weight distribution and the viscosity of water-soluble dietary fibre polysaccharides isolated from green beans, Brussels sprouts and green peas were investigated following boiling, microwave treatment and canning. Blanching was used as a reference process. In green beans and Brussels sprouts microwave treatment had minor effects, while there generally was a small decrease of neutral sugars with boiling. The influence of canning was more pronounced and a decrease of uronic acid-containing polymers in the high-molecular-weight fraction was obtained, simultaneously as the amount in the middle toed fraction increased. Further, in green beans there also seemed to be a loss of polymers containing galactose and uronic acids into the process water with boiling and canning, respectively. In peas, there was an increase of the fraction containing middle-sized polymers (uronic acids and arabinose) with all processes. With microwave treatment there was a simultaneous loss in the high-molecular-weight fraction, whereas no such decrease could be obtained with boiling or canning. The lowest viscosity was obtained in extracts from canned materials and the highest with blanching, while boiling and microwave treatment had various effects in different vegetables. The soluble fibre fraction of blanched green beans had a higher viscosity than that of Brussels sprouts and green peas. Thus, both amount and properties—molecular weight distribution and viscosity—of soluble fibre in vegetables were affected by processing, but differently in various vegetables.     

干海参中外源性糖溶出条件的优化

目的针对劣质干海参加工过程中掺杂使假的现象,对非法添加的外源性糖的溶出条件进行优化,为干海参的品质鉴别提供参考。方法以外源性糖残留率为指标,通过三因素三水平L9(34)正交试验分析浸泡过程中的换水次数、煮制时间以及泡发时间对外源性糖溶出的影响。同时检测海参中的蛋白质经不同煮制时间的损失情况。结果煮制时间对外源性糖的溶出影响极显著(P0.01),泡发时间影响显著(P0.05),浸泡过程中的换水次数在选定的水平范围内影响不显著(P0.05)。煮制时间对蛋白损失有显著影响,煮制20、40、60 min组对应的蛋白损失率分别为1.73%、2.94%和3.70%。结论综合考虑外源性糖残留与蛋白损失情况,干海参中外源性糖溶出的较优工艺参数为:浸泡24 h,期间换水1次,煮制20 min,煮后泡发24 h。     

剑麻纤维脱胶工艺研究

剑麻纤维作为绿色无污染产品日益受到消费者的青睐,但其复杂的结构特性直接影响了它的深加工和应用。文章通过碱煮、酸煮、碱氧一浴法和生物酶法的探讨,研究其脱胶方法,实现剑麻纤维中各组分的有效分离。对比精干麻的纤维素含量及残胶率和生物显微镜扫描后的纤维结构图,结果表明,碱氧一浴法处理效果较佳。     

Deodorization of a Colorant Prepared from Red Cabbage

A process for preparing odor-free colorant from red cabbage was developed. Anthocyanins in an acidified aqueous cabbage extract were adsorbed on Amberlite XAD-7, water-washed to remove residual cabbage odor, eluted with ethanol containing 0.1% HCl, and concentrated by evaporation. Optimal conditions for single stage batch contact and column deodorization were determined. Pigment recovery generally exceeded 90%. The stability, spectral, and colorant properties of the recovered pigments were not altered significantly by the process. Spent adsorbent could be regenerated by water washing without adversely affecting process efficiency or colorant performance.     

The effect of cooking on Brassica vegetables

Assessing antioxidant intake requires a food antioxidant database. However, cooking may affect antioxidant content due to antioxidant release, destruction or creation of redox-active metabolites. Here, effects of boiling, steaming and microwaving of broccoli, cauliflower, cabbage and choy-sum (Chinese cabbage) were explored by measuring antioxidant contents of raw and cooked vegetables. Cooking water was also tested. For all cooked vegetables, antioxidant content was highest in steamed > boiled > microwaved, and decreased with longer cooking time, regardless of method. All steamed vegetables had higher antioxidant contents than had matching raw vegetables. Effects were variable for boiling and microwaving. Microwaving caused greater antioxidant loss into cooking water than did boiling. Marked losses of anitoxidants occurred in microwaved cabbage and spinach. To assess food antioxidant content/intake accurately, cooking effects need detailed study. Steaming may be the cooking method of choice to release/conserve antioxidants. The cooking water is a potentially rich source of dietary antioxidants.     

二氧化氯和臭氧杀菌处理对菜心贮藏品质的影响

为提高菜心贮藏品质,研究二氧化氯(ClO2)、臭氧(O3)两种杀菌剂对菜心贮藏期间的呼吸强度、丙二醛含量、过氧化物酶活等品质指标变化规律的影响。研究发现,与对照组相比,在贮藏期内ClO2和O3对菜心呼吸的影响是先促进后抑制,二者均使菜心呼吸高峰提前到达,但贮藏中后期(6 d^9 d)杀菌组的呼吸强度低于对照组,ClO2对呼吸的抑制优于O3;ClO2和O3提高了菜心贮藏前期的硬度,贮藏后期ClO2组菜心硬度适中;ClO2降低了菜心a*值,有利于保持菜心的绿色;O3对菜心a*值略有提高,对菜心绿色影响不显著;ClO2和O3促使菜心中丙二醛的累积,但量小难以促衰老;ClO2能稳定维持偏低的过氧化物酶活性,抑制苯丙氨酸解氨酶活性,延缓其木质化和衰老,保持品质。综合分析得出,ClO2更适合杀菌处理菜心,货架期可达12 d,具有潜在的应用前景。     

The effect of cooking and processing on the glucosinolate content: Studies on four varieties of portuguese cabbage and hybrid white cabbage

The concentrations of individual and total glucosinolates were measured in four types of Portuguese cabbage and in one hybrid white cabbage before and after cooking. Typical Portuguese culinary procedures include boiling the cabbage for 10 min but for particular kale types the leaves are first shredded then boiled for 5 min (Caldo verde). Analysis of the fresh cabbage, cooked leaves and cooking water showed that the glucosinolate content of the cabbages is reduced by more than 50%. Almost all of this loss is accounted for as intact glucosinolates in the cooking water, normally used for soups in Portugal.     

Effect of ascorbic acid and citric acid on the quality of salted Chinese cabbage during storage

Changes in color, browning indices, enzyme activity, and physical and chemical quality during the storage period were investigated to assess the effectiveness of storage period extension along with the addition of ascorbic acid (AA) and citric acid (CA) to salted Chinese cabbage. After 16 days of storage, the change in chromaticity value showed treatment with 0.5% CA showed the lowest change in the brown index during the storage period. The control showed the highest residual activity of polyphenol oxidase among control, AA, and CA-treated salted cabbage. AA and CA treatment effectively inhibited the initial populations of microorganisms including total aerobic bacteria, lactic acid bacteria, and yeast and molds in salted Chinese cabbage during storage. Further, the texture, i.e., hardness, chewability, and elasticity, tended to decrease with increasing storage. These results suggest that treatment with AA could help maintain the quality of salted Chinese cabbage during the storage period.