新型果蔬切丁机的设计

国内现有切丁机存在着结构复杂、生产效率低、切出10mm以上果蔬大丁形状不规整的问题,无法满足国内果蔬加工业的发展需求。提出采用离心切削法进行果蔬切片、圆盘刀切丝、横切刀切丁的三维切丁技术的新型果蔬切丁机方案。通过对果蔬的切丁成型分析,得到切10mm以上果蔬大丁形状不规整的原因。仿真分析得到切丁机推进器和横切刀之间的速比以及两者之间的中心位置布置的合理组合。对切丁机主要结构部件进行了设计,研制果蔬切丁机样机。性能试验表明:切出的(15×15×15)mm和(20×20×20)mm马铃薯立方块形状规整,其相对百分数均小于15%,达到了设计要求。     

气相色谱内标法测定蔬菜中的乐果

目前,测定蔬菜中乐果农残主要使用外标法,仪器的重现性差,相对偏差达到10％左右,造成定量分析误差较大.产生重现性差的原因是PFD检测器测定乐果时信号的响应值有不断地增大的趋势,本文采用三唑磷为内标物,对仪器条件和处理方法进行了优化,较好地改善了测定方法的重现性,并且简化了处理方法,使样品前处理具有较好的可操作性和稳定性,方法的加标回收率达到92.2～105.0％.     

高效液相色谱法同时测定蔬菜中多种磺酰脲类除草剂的残留量

建立高效液相色谱法同时测定蔬菜中8种磺酰脲类除草剂残留量的检测方法。样品经乙腈提取、凝胶渗透色谱净化、C18固相萃取柱净化后,采用高效液相色谱分离,二极管阵列检测器检测,外标法定量。本法简便、快速、定量准确、精密度高,适用于进出口蔬菜中多种磺酰脲类除草剂残留量的同时检测。     

Do healthy,child-friendly fruit and vegetable snacks appeal to consumers? A field study exploring adults’ perceptions and purchase intentions

The majority of children in the U.S. do not consume enough fruits and vegetables (FV). Children’s liking of and preferences for FV are consistent predictors of intake, as are factors such as availability and accessibility, which are largely under the control of parents and caregivers. This study was designed to examine parents’ and caregivers’ current purchasing habits regarding child-friendly (CF)-shaped foods and pre-cut produce; determine their sensory perceptions of CF-shaped vs. regular-shaped pre-cut FV; and, to ascertain their willingness to pay slightly more for CF-shaped FV compared to fresh, whole produce. Healthy, CF-shaped fruit and vegetable snacks were developed by cutting FV into CF shapes (butterfly, chick, flower, teddy bear). Participants (n = 298) were adults, the majority of whom (66.1%) reported having children at home. Participants who reported having children at home consistently recognized CF-shaped fruit and vegetable samples as CF-shaped foods, while 64.4% of participants with children at home perceived regular-shaped pre-cut fruit and vegetable samples as CF-shaped foods. Participants rated CF-shaped samples as more visually appealing than regular-shaped samples, (p < 0.0001) and were 34% more likely to select CF-shaped samples. Female gender, the presence of children in the home, and frequent self-reported purchase of pre-cut produce were also significant positive predictors of visual appeal. Taste and texture ratings were not consistently significantly higher for CF-shaped fruit and vegetable samples. CF shape predicted higher willingness to pay extra for the fruit and vegetable product (p = 0.0057), as did frequent purchase of pre-cut produce and CF-shaped foods. Adults, particularly females and individuals with children in the household, find CF-shaped FV highly visually appealing and are willing to pay slightly more for these foods. Healthy, ready-to-eat, CF-shaped fruit and vegetable snacks may be a promising marketing strategy to help increase fruit and vegetable intake among children.     

A rapid multi-residue method for the determination of pesticide residues in choi sum, yardlong beans and aubergines

A rapid multi-residue modified QuEChERS method has been developed to analyse 20 pesticide residues in choi sum, yardlong beans and aubergines by gas chromatography with flame photometric and electron capture detectors. Primary secondary amine in dispersive form was omitted in the extraction step but instead packed in a Pasteur glass pipette for column cleanup. The recoveries for all 20 pesticides except chlorothalonil at 10-500 μg kg⁻¹ fortification levels ranged from 74.0% to 117%. Similar recoveries of 81.7-117% were obtained for all organochlorine and pyrethroid pesticides including chlorothalonil using silica gel cleanup. The relative standard deviation obtained was below 14.9%. The limit of quantification was in the range 1-10 μg kg⁻¹. The method has high selectivity for pesticides in vegetables containing high amount of chlorophyll, pigment and coloured compounds such as in choi sum and aubergines. The method was used to analyse 132 vegetable samples from residue survey.     

Determination of atrazine and carbaryl pesticide residues in vegetable samples using a multianalyte dipstick immunoassay format

A dipstick assay for the simultaneous determination of atrazine and carbaryl in vegetable samples was developed. The analytical method involved a fast extraction procedure followed by a multi-strip membrane test. The assay took 10 min, with a detection limit (naked eye) of 10 and 200 µg l^-1 for atrazine and carbaryl, respectively. The cross-reactivities to related compounds tested were negligible except for propazine. Quantification of the pesticides was carried out by measuring the dot colour with a spectrophotometer. IC₅₀ values (inhibition constant at 50% of the maximum binding) of 2.04 μg l^-1 for atrazine and 92.8 μg l^-1 for carbaryl were achieved by this approach. Vegetable samples were extracted with MeOH. The proposed methodology was used to analyse atrazine and carbaryl and check for compliance with European Union maximum residue levels for vegetables. Recoveries (75-105%) were in agreement with those obtained by GC/MS or HPLC. Standard curves using 25% methanol/75% TBS were used for food sample assays using a multi-analyte dipstick. IC₅₀ values were 9.2 μg l^-1 for atrazine and 179.2 μg l^-1 for cabaryl.     

Prevalence and trends of bacterial contamination in fresh fruits and vegetables sold at retail in Canada

In recent years, fresh fruits and vegetables have been linked to numerous foodborne illness outbreaks in different regions of the world, including in Canada. In light of rising concerns over the microbial safety of these commodities, the Canadian Food Inspection Agency conducted retail surveys to obtain information on the occurrence of bacterial pathogens in a wide range of produce available in the Canadian marketplace (local vs. imported, organic vs. conventional). Samples (n = 31,329) were collected across Canada over four years (2009–2013) and consisted of leafy vegetables (n = 12,073), leafy herbs (n = 6032), green onions (n = 3381), cantaloupes (n = 3230), tomatoes (n = 4837) and berries (n = 1776). These samples were analysed in ISO 17025-accredited laboratories for various bacterial pathogens (Salmonella, Escherichia coli O157, Shigella, Campylobacter and Listeria monocytogenes), as well as for generic E. coli, an indicator of fecal contamination. The Wilson confidence interval was used to determine the prevalence of the different micro-organisms in the commodities investigated. Control charts and seasonal indices, statistical tools adapted here to explore the large amount of data collected for each commodity, were used to identify potential adverse events or trends in bacterial contamination. The prevalence of bacterial contamination observed during this study in the six commodities examined was generally very low, with prevalence intervals ranging from [0, 0.08%] in tomatoes to [0.79, 1.30%] in leafy herbs. Most of the samples that were reported as “positive for bacterial contamination” had elevated (>100 CFU or MPN/g) levels of generic E. coli, but did not have detectable levels of the bacterial pathogens investigated. Of the samples that did have detectable levels of bacterial pathogens, the only bacteria that were both detected and isolated were Salmonella and L. monocytogenes. Despite the overall low prevalence of contamination seen in most produce, a notable seasonal trend was observed in the leafy vegetable group, where higher bacterial contamination rates were confirmed in the summer in organic as opposed to conventional products. These findings provide valuable baseline information that can support food safety decisions, and confirm that the vast majority of fresh fruits and vegetables available on the Canadian market are safe in terms of bacteriological hazards.     

混合辐照饲料喂养大鼠的骨髓多色性红细胞微核细胞率观察

本文用两组辐照饲料对Wistar大鼠进行了110天和150天喂养,观察其骨髓多色性红细胞(PCE)的微核效应。一组为混合辐照饲料组,辐照饲料占80％;另一组为辐照蔬菜组,辐照蔬菜占总饲料的3％,辐照剂量为2KGy,是实际需要的辐照剂量2倍以上。同时设有普通饲料的阴性对照组,和用环磷酰胺处理或给以全身整体照射的阳性对照组。微核测定采用Giemsa染色法、Harris苏本精复染法和荧光染色法,两批实验均表明,在本实验条件下,不论是喂养混合辐照饲料还是辐照蔬菜,都未见到大鼠骨髓PCE微核细胞率有所增高。     

QuEChERS-液相串联质谱法快速测定蔬菜水果中氟吗啉和烯酰吗啉残留量

目的建立基于QuEChERS与液相串联质谱(liquidchromatographytandemmassspectrometry,LC-MS/MS)联用技术快速测定蔬菜水果中氟吗啉和烯酰吗啉残留量的分析方法。方法样品经乙腈提取后,用QuEChERS法净化, Symmetry C18色谱柱分离, LC-MS/MS外标法定量。结果方法学验证,该方法具有较高的灵敏度,氟吗啉和烯酰吗啉的检出限为0.05μg/kg,定量限为0.1μg/kg;在0.1～25μg/kg浓度范围,线性相关系数大于等于0.9963,回收率在82.4%～106.3%之间,相对标准偏差为1.5%～8.8%,该方法具有较好的回收率和良好的再现性,满足国家相关标准要求。结论该方法处理过程快速简便,灵敏度高、专属性强。