Impedance measurements to assess microbial contamination of ready-to-use vegetables

 An impedometric method for estimating the microbial load of ready-to-use vegetables, either inoculated or not inoculated with antimicrobial-producing lactic acid bacteria, was investigated. The correlation (R ²) between total mesophilic bacteria (log cfu/g) and time to detection was 0.889. A discrepancy was observed for the impedometric measurement of low coliforms counts, particularly in samples inoculated with lactic acid bacteria and stored at 8°C for 6 days. Time to detection for the two groups of microorganisms was less than 11 h. Received: 25 November 1996 / Revised version: 23 January 1997     

Effect of gamma irradiation on microbial analysis, antioxidant activity, sugar content and color of ready-to-use tamarind juice during storage

Gamma irradiation is highly effective in inactivating microorganisms in various foods and it offers a safe alternative method of food decontamination. In the present study, the effect of gamma irradiation on microbial analysis, antioxidant activity, sugar content, color and sensory evaluation of ready-to-use tamarind juice was investigated during storage. A fresh tamarind juice was prepared by dissolving 5 g of pulp/100 ml of deionized distilled water and irradiated at 0, 1, 3 and 5 kGy at room temperature. Microbiological assay of the fresh and stored ready-to-use tamarind juice showed better quality after gamma irradiation. Antioxidant ability was studied by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), FRAP (ferric reducing/antioxidant power) and total phenolic contents, and gamma irradiation had a significant increase or maintenance on the antioxidant potential of the ready-to-use tamarind juice. Contents of glucose and fructose also showed minimal alterations both in the fresh and stored samples. There was a significant improvement in the Hunter color value in both the fresh and stored tamarind juice. To conclude, gamma irradiation improves the microbial decontamination and the antioxidants as well as the color of the ready-to-use tamarind juice without any adverse change in sensory qualities.     

Determination of food contamination by mineral oil material from printed cardboard using on-line coupled LC-GC-FID

 Inks used for printing paper and cardboard are dispersions of synthetic organic pigments in a bonding agent system built up essentially of resins, vegetable oils and high-boiling-point mineral oil products (b.p. >250°C). The proportion of mineral oil material in the ink ranges between 20 and 30%. The more volatile mineral oil components slowly evaporate from the printed cardboard box and may migrate into the food product. They contaminated cereals and dry baby-food products at concentrations between 10 and 150 mg/kg. Received: 27 January 1997     

The perfluoroalkyl substances (PFASs) contamination of fruits and vegetables

Fruit and vegetables play a major role in human nutrition due to richness of nutrients, dietary fibre, and phytochemicals. As dietary intake is identified as one of the dominant exposure pathways to perfluoroalkyl substances (PFASs), a cross-sectional study involving determination of their levels in food of plant origin has been conducted. Locally-grown and imported fruit and vegetable samples, collected in 2016 were inspected for 10 perfluoroalkyl acids (PFAAs) using QuEChERS as sample pre-treatment procedure followed by micro-HPLC-MS/MS. Three of 10 target analytes, perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS) were quantitatively determined. The detection frequency for PFASs across the 55 samples analysed was less than 10%. The major contributor of the total PFASs concentration in the investigated group was PFBA for which the concentration, reported only for banana, apple and orange samples, was 50.740 ng g^?1 ww. The most often detected compound was PFOA. The origin and growing region are possible factors with the potential to influence PFASs distribution profile and their levels in food.     

The impact of home freezing on the sensory characteristics of ready-to-use leafy vegetables

BACKGROUND: Owing to the increasing trend of consumption of ready‐to‐use leafy vegetables, the necessity of determining the best conditions for their frozen storage and the considerable impact of freezing on their sensory attributes, research was carried out to determine the best freezing temperature and storage time for a mixture of Allium ampeloprasum, Lepidium sativum and Stureia hortensis. RESULTS: The results for freezing temperature at three different storage times showed that colour and overall acceptability at ? 18 °C were always ranked first (P < 0.05), while taste at ? 18 °C was ranked first on days 120 and 150. The results for frozen storage time at three different temperatures indicated that colour, taste and acceptability were not significantly different. CONCLUSION: Overall, the results of this research indicated that the sensory attributes of leafy vegetables during 180 days of frozen storage were affected mainly by freezing temperature rather than frozen storage time. Copyright © 2010 Society of Chemical Industry     

北京五城区零售鲜切果蔬中重要食源性致病菌污染与耐药性研究

目的 为探究鲜切果蔬中食源性致病菌污染及耐药现状,采集北京五城区零售鲜切果蔬样品进行重要食源性致病菌检测及耐药性研究.方法 本研究采用食品微生物检验国家标准方法,分别检测金黄色葡萄球菌、沙门氏菌、单核细胞增生李斯特氏菌和大肠埃希氏菌,对目标菌分离株进行耐药性测定,并通过荧光定量聚合酶链式反应(PCR)方法筛查致泻大肠埃...     

2012~2016年云南省新鲜蔬菜中铅污染状况分析

目的 了解云南省市售新鲜蔬菜重金属铅污染的总体状况。方法 采用分层随机抽样的方法, 2012～2016年在云南省15个州市超市和农贸市场随机采集云南当地居民消费量较大的时令蔬菜, 全省共采集产地为云南本省产的样品1907份, 按国家统一的方法检测, 并分析新鲜蔬菜铅污染状况。结果 共监测新鲜蔬菜8大类, 1907件样品, 铅检出率为56.42%, 超标率为6.97%。铅平均检测值、P50值均低于国家食品污染物限量标准。结果显示本调查中新鲜蔬菜铅超标率高于平均水平的产地为红河、楚雄、文山、曲靖4个地区, 超标率分别为15.22%、11.29%、11.02%、9.32%; 新鲜蔬菜铅超标率高于平均水平的类别为茎类、瓜菜类、块根块茎类、鳞茎类蔬菜, 超标率分别为15.14%、8.64%、7.72%、7.59%。结论 云南省新鲜蔬菜铅总体污染水平较低, 但存在一定的地域和类别污染水平较高的情况, 建议改善蔬菜种植地周边环境, 根据污染状况和蔬菜的富集情况的不同, 可以进行选择性种植, 建议不宜大量、长期食用个别蔬菜, 食品要多样化。     

Methylene blue test to assess the microbial contamination of frozen peas

A methylene blue dye reduction test has been assessed as a simple rapid means of monitoring microbial contamination of frozen peas. Experiments using cultures of pea microflora showed a linear relationship between decolourization time and aerobic plate count (APC). In subsequent experiments during the 1983/4 harvesting season dye reduction tests and APC were carried out on 389 frozen pea samples obtained from three commercial factories. A significant correlation was obtained, although longer decolourization times were recorded for equivalent APC. Average decolourization times for frozen pea samples were 8 h and 11 h for counts of 10⁵ and 10⁴ cfug⁻¹ respectively. A standard calibration curve for peas is included and the method is recommended for monitoring plant hygiene in vegetable freezing factories.     

2016年广东省6类食品不同微生物污染情况分析

目的 为了解广东省流通食品的微生物污染状况。方法 采用GB 4789-2010《食品安全国家标准 食品微生物学检验》对2016年检验的6类食品进行微生物（菌落总数、大肠菌群、霉菌和酵母菌、致病菌）检验,对检验结果进行统计分析。结果 3216份样品中共检出不合格样品39份,总体合格率为98.79%。不同微生物项目的检验结果中,菌落总数的合格率相对最低,为99.19%。检验的6类食品中速冻食品、方便食品和水产制品检出不合格样品,方便食品的合格率（97.2%）相对最低。结论 广东省食品微生物污染整体状况较好,建议对微生物污染风险较高的方便食品、水产制品进行重点关注,采取有效措施降低食品微生物污染的风险。     

Material properties of processed fruit and vegetables I. Effect of extraction and thermal treatment on apple parenchyma

 Using apple mash prepared from apple parenchyma, the effect of the processing steps of cold and warm water treatment, respectively, on structure and material properties of treated mashes, as well as dried and rehydrated materials with cellular structure (MCS), compared to alcohol-insoluble substance (AIS), were investigated. Cold water treatment gives rise to pectin-enriched, relatively large and mechanically stable cell clusters which show good elastic and solid-state properties in aqueous dispersions. However, warm water treatment effects a thermal hydrolytic degradation of pectin in the MCS whereby the mechanical cell separation is simplified and reduced structural stability of the dispersions can be observed. AIS contains the biggest particles and best material properties in comparison to MCS. The connection between structural parameters which are affected by processing and material properties, in addition to the importance of AIS and MCS, respectively, as model substrates, are discussed. Received: 27 June 1997 / Revised version: 17 October 1997     

Flavonoids in Meliponinae honeys from Venezuela related to their botanical, geographical and entomological origin to assess their putative anticataract activity

 Honey was collected from 24 stinglessbee nests in Venezuela. The flavonoid compounds in the phenolic extracts were analysed and related to the botanical, geographical and entomological origin of the honey. Honeys produced in savannas were richer in flavonoids compared with honeys from the forests. It was found that phenolic extracts of honey of the same geographical origin had similar flavonoid profiles, whereas the same could not be said of honeys of the same entomological origin, although the botanical origin of the samples was variable. It is proposed that analysis of stinglessbee honey eyedrops in terms of their flavonoid content can be used as a basis of authenticating and controlling for their geographical origin. Received: 28 July 1997     

果蔬中常见真菌毒素的检测研究进展

果蔬在田间的生长过程以及采摘后的贮存、运输和加工过程中,容易受到病原真菌的污染,病原菌通过寄主果蔬表面伤口或自然孔口侵入,导致果蔬腐烂并积累大量真菌毒素。腐烂果蔬会造成巨大的经济损失,同时经由食物链的传递威胁人和动物的健康。鉴于果蔬中真菌毒素的危害性,本文总结了近年来主要污染果蔬的毒素的种类、污染现状、危害及其检测方法,其中目前检测仍以色谱法、质谱法等仪器检测为主,虽然可以精确定量检测,但是耗材和时间成本较大;随着大规模样本的筛选检测需求的提高,免疫法和表面增强拉曼光谱法等高通量的快速检测逐渐受到关注。本文旨在为真菌毒素的检测防控提供参考。     

Detection of wheat contamination in oats by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA)

 It is well established that the consumption of wheat prolamins causes the characteristic symptoms of coeliac disease (CD) in subjects who are predisposed to it. There is currently much discussion about the role of oats in the pathogenesis of CD. Evidently, it is important that oats used for clinical studies are not contaminated with wheat. In this study, 38 oat samples were investigated by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA): 30 samples consisted of flakes or grains and 8 probes were industrially processed oat diets. Wheat prolamin (gliadin) detection by ELISA showed that 16 of these samples contained less than the detection limit of 0.2 mg gliadin/100 g dry weight; 21 samples contained less than 2.8 mg gliadin/100 g dry weight and 1 sample reached 38 mg gliadin/100 g dry weight, clearly exceeding the allowed Swiss limit of 10 mg gliadin/100 g dry weight for gluten-free products. Spiking experiments showed that the wheat PCR system is about ten times more sensitive than the ELISA system, provided that the isolated DNA is fully amplifiable. Thus, wheat DNA could be detected by the wheat PCR system in ten samples with gliadin contents below the detection limit of the ELISA system used. Applying a eukaryote-specific 18S-PCR system the presence of amplifiable DNA was verified. Only two of eight samples of industrially processed oat products contained amplifiable DNA, the other six samples had no detectable DNA left. One sample was wheat-PCR positive. However, all eight samples contained detectable amounts of gliadin in the ELISA. Received: 7 November 1997     

Relationships between biochemical and quality-related characteristics of breads, resulting from the interaction of flour, microbial starter and the type of process

 The possible relationships between biochemical characteristics [total starch, sugars, low-molecular-weight dextrins (LMWD), acetic and lactic acids, soluble solids and crumb-swelling power] and characteristics related to the quality of wheat bread (volume, texture and sensory quality scores) have been investigated. Variables influencing the possible interactions occurring were the type of flour (white and whole-wheat flours), the starter microorganism (Lactobacillus brevis, L. plantarum) and the type of process used to introduce the lactobacilli inoculum (sourdough, straight). The main factor explaining variability of data was related to sensory quality attributes and physical characteristics of the breads. The second factor was related to LMWD and the third to the acidity and lactic acid content of breads. The first factor permitted separation of the bread samples into two groups on the basis of flour extraction rate, whereas LMWD allowed differentiation between white breads made with sourdough or straight processes. Cluster analysis included the level of acidity and the lactic acid content as additional factors grouping control breads (without starter) together with breads made using a straight process. The best canonical correlation was established between the physical characteristics of breads and carbohydrates, soluble solids and crumb-swelling power. The first pair of canonical variables between two sets of experimental variables showed a squared correlation coefficient of 0.986. Received: 15 July 1996     

成品酱油微生物污染变质的风险预警

为对微生物污染引起的成品酱油变质进行风险预警,对比研究了成品变质酱油和未变质酱油中还原糖、总酸、氨态氮以及双乙酰4种理化指标。结果表明:耐盐芽胞杆菌污染引起的成品酱油变质,其理化指标产生较大变化,其中还原糖含量大幅下降,总酸、氨态氮以及双乙酰含量明显升高,经测定还原糖含量降幅60%,总酸含量升幅32%,氨态氮含量升幅6.0%、双乙酰含量升幅20.4%时,成品酱油已出现变质现象,可以判断为变质。     

Development of an HPLC method for measurements of the stability of Irganox-type polymer antioxidants in fatty food simulants

 A reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed to measure the stability of four Irganox-type polymer antioxidants (Irganox 245, Irganox 1035, Irganox 1098 and Irganox 3114) in an olive oil food simulant and isooctane, which has been proposed as an alternative fatty food simulant. The tests of stability in olive oil were carried out under three different conditions, i.e. 40°C for 10 days, 100°C for 1 h and 175°C for 1 h. The exposure conditions for isooctane were 60°C for 3 h. Results showed that for all additives tested no instability phenomena in olive oil or isooctane simulants were observed under the exposure conditions applied. The analytical methodology developed could eventually be used for stability testing and migration studies of other similarly structured antioxidants in fatty food simulants. Received: 11 September 1997     

Development of an HPLC method for measurements of the stability of Irganox-type polymer antioxidants in fatty food simulants

 A reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed to measure the stability of four Irganox-type polymer antioxidants (Irganox 245, Irganox 1035, Irganox 1098 and Irganox 3114) in an olive oil food simulant and isooctane, which has been proposed as an alternative fatty food simulant. The tests of stability in olive oil were carried out under three different conditions, i.e. 40°C for 10 days, 100°C for 1 h and 175°C for 1 h. The exposure conditions for isooctane were 60°C for 3 h. Results showed that for all additives tested no instability phenomena in olive oil or isooctane simulants were observed under the exposure conditions applied. The analytical methodology developed could eventually be used for stability testing and migration studies of other similarly structured antioxidants in fatty food simulants. Received: 11 September 1997     

葡萄酒微生物污染形成的不良风味物质研究进展

葡萄酒中不良风味物质的存在严重影响葡萄酒的品质,给生产带来较大的经济损失。对葡萄酒生产过程中由于微生物污染而形成的不良风味物质及主要预防措施进行主要介绍,包括葡萄原料被霉菌污染产生的蘑菇味和泥土味等物质;葡萄酒被酒香酵母污染产生的马厩味、酚味和鼠味等物质,被乳酸菌污染产生的黄油味、饭馊味和老鹳草味等物质,被醋酸菌污染产生的胶水味、煮苹果味和醋酸味等物质;橡木桶和软木塞被真菌污染产生的霉味、木塞味等物质。通过对微生物污染产生的不良风味物质特征及其主要防治措施进行系统梳理,为葡萄酒酿造生产提供借鉴。     

对塑料瓶受微生物污染状况的初步探讨

塑料瓶的仓储时间、温度和湿度是影响微生物污染程度的主要因素。本文对此作了初步探讨，并试用多种常用消毒剂，以寻求较理想的消毒方法处理受污染的塑料瓶。