Assessment of bacterial biofilm on stainless steel by hyperspectral fluorescence imaging

Hyperspectral fluorescence imaging techniques were investigated for detection of two genera of microbial biofilms on stainless steel material which is commonly used to manufacture food processing equipment. Stainless steel coupons were deposited in nonpathogenic E. coli O157:H7 and Salmonella cultures, prepared using M9 minimal medium with casamino acids (M9C), for 6 days at 37 °C. Hyperspectral fluorescence emission images of the biofilm formations on the stainless coupons were acquired from 416 to 700 nm with the use of ultraviolet-A (320–400 nm) excitation. In general, emission peaks for both bacteria were observed in the blue region at approximately 480 nm and thus provided the highest contrast between the biofilms and background stainless steel coupons. A simple thresholding of the 480 nm image showed significantly larger biofilm regions for E. coli O157:H7 than for Salmonella. Viable cell counts suggested that Salmonella formed significantly higher density biofilm regions than E. coli O157:H7 in M9C medium. On the basis of principal component analysis (PCA) of the hyperspectral fluorescence images, the second principal component image exhibited the most distinguishable morphological differences for the concentrated biofilm formations between E. coli and Salmonella. E. coli formed granular aggregates of biofilms above the medium on stainless steel while Salmonella formed dense biofilm in the medium-air interface region (pellicle). This investigation demonstrated the feasibility of implementing fluorescence imaging techniques to rapidly screen large surface areas of food processing equipment for bacterial contamination. Company and product names are used for clarity and do not imply any endorsement by USDA to the exclusion of other comparable products.     

Development of a portable hyperspectral imaging system for monitoring the efficacy of sanitation procedures in food processing facilities

Cleaning and sanitation in food processing facilities is a critical step in reducing the risk of transfer of pathogenic organisms to food consumed by the public. Current methods to check the effectiveness of sanitation procedures rely on visual observation and sub-sampling tests such as ATP bioluminescence assays and culturing methods. To augment existing verification methods, a hand-held visible hyperspectral imaging device was developed. The device is capable of acquiring reflectance images using ambient lighting, and fluorescence responses to supplemental violet (405 nm) excitation. To enhance the ability of detecting relatively low intensity fluorescence responses in the presence of ambient lighting, the device includes the ability to identify wavebands where the intensity of ambient lighting is relatively low. Valleys in ambient illumination intensity when using fluorescent lighting were found at around 475, 520, 570, and 675 nm. A principal goal is to acquire data to support development of a commercially-viable, hand-held, imaging system.     

Formation of dairy fouling deposits on food contact surfaces

This study aimed to compare microbiological, biochemical and physical methods to quantify dairy fouling deposits. The influence of factors affecting dairy fouling formation is investigated by selected methods with respect to material type (polytetrafluoroethylene and stainless steel) and temperature (4 and 20 °C) for a defined time. The factors were investigated using nonmicrobiologically caused and microbiologically caused dairy deposits formed by UHT and pasteurised milk inoculated with Pseudomonas fragi. Both deposit types exhibited different adhesion behaviours. The highest positive correlation coefficient was found between biochemical and microbiological methods (0.932) obtained at both incubation temperatures after 24 and 48 h.     

Combining multispectral reflectance and fluorescence imaging for identifying bruises and stem-end/calyx regions on Golden Delicious apples

As a part of the project for detecting bruises on Golden Delicious apple using vision system, the present paper shows a method that could separate the stem-end/calyx regions from the true bruises by combining the information of hyperspectral reflectance and fluorescence images. The images were scanned between 400 nm and 1,000 nm with a hyperspectral imaging system. Different light sources were constructed for capturing the reflectance and fluorescent images. Compared to the reflectance signal, the fluorescence signatures are much less intense, so that only the fluorescence of chlorophyll waveband was further examined (i.e., 685 nm). The analysis showed that the Principal Components scores images, which were based on the reflectance images, can be used for separating the bruised areas as well as the stem-end/calyx regions from the sound apple tissues; whereas only the stem-end/calyx was able to be recognized from the fluorescence images. For the samples investigated in this study, no stem-end/calyx regions were misrecognized as bruises; however, about 12% of bruised surfaces were misclassified as stem-end or calyx regions. All of the healthy tissues were correctly recognized as non-stem-end/calyx regions. The classification results indicated that combining multispectral reflectance and fluorescence imaging may help to identify the stem-end/calyx regions from the true bruised tissue and therefore to improve the accuracy for bruise detection on Golden Delicious apples.     

Early detection of toxigenic fungi on maize by hyperspectral imaging analysis

Fungi can grow on many food commodities. Some fungal species, such as Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger and Fusarium spp., can produce, under suitable conditions, mycotoxins, secondary metabolites which are toxic for humans and animals. Toxigenic fungi are a real issue, especially for the cereal industry. The aim of this work is to carry out a non destructive, hyperspectral imaging-based method to detect toxigenic fungi on maize kernels, and to discriminate between healthy and diseased kernels. A desktop spectral scanner equipped with an imaging based spectrometer ImSpector- Specim V10, working in the visible-near infrared spectral range (400-1000 nm) was used. The results show that the hyperspectral imaging is able to rapidly discriminate commercial maize kernels infected with toxigenic fungi from uninfected controls when traditional methods are not yet effective: i.e. from 48 h after inoculation with A. niger or A. flavus.     

Near-infrared spectroscopy and imaging in food quality and safety

Over the last two decades, near-infrared spectroscopy (NIRS) has established itself as a non-destructive analytical technique in a variety of disciplines. However, recent technological advancements in hardware design and data mining techniques have unleashed the potential of NIRS to become a tool of choice for routine analyses of agricultural products. The current paper synthesizes the status of NIRS in the agri-food industry in terms of hardware and software development as well as the direction in which the NIRS research is headed. An extensive review of literature reveals that the emphasis on hardware development is focused on developing compact, robust, and portable spectrometers and hyperspectral imaging (HSI) systems. The software development on the other hand is geared towards developing better preprocessing, analyses, and modeling techniques using chemometrics, support vector machines, and artificial neural networks. The four main agri-food sectors identified to be the beneficiaries of this research revolution are grain quality monitoring; post-harvest handling of fruits and vegetables; identification of contaminants in animal produce and feed; and food safety and authenticity. Apart from discussing the aforementioned topics, the paper also provides food scientists some working knowledge on parameters crucial to the performance of spectral and imaging systems. It is expected that further development of NIRS will help agricultural and food scientists to enhance the quality and safety of our food.     

Inactivation strategy for Clostridium perfringens spores adhered to food contact surfaces

The contamination of enterotoxigenic Clostridium perfringens spores on food contact surfaces posses a serious concern to food industry due to their high resistance to various preservation methods typically applied to control foodborne pathogens. In this study, we aimed to develop an strategy to inactivate C. perfringens spores on stainless steel (SS) surfaces by inducing spore germination and killing of germinated spores with commonly used disinfectants. The mixture of l-Asparagine and KCl (AK) induced maximum spore germination for all tested C. perfringens food poisoning (FP) and non-foodborne (NFB) isolates. Incubation temperature had a major impact on C. perfringens spore germination, with 40 °C induced higher germination than room temperature (RT) (20 ± 2 °C). In spore suspension, the implementation of AK-induced germination step prior to treatment with disinfectants significantly (p < 0.05) enhanced the inactivation of spores of FP strain SM101. However, under similar conditions, no significant spore inactivation was observed with NFB strain NB16. Interestingly, while the spores of FP isolates were able to germinate with AK upon their adhesion to SS chips, no significant germination was observed with spores of NFB isolates. Consequently, the incorporation of AK-induced germination step prior to decontamination of SS chips with disinfectants significantly (p < 0.05) inactivated the spores of FP isolates. Collectively, our current results showed that triggering spore germination considerably increased sporicidal activity of the commonly used disinfectants against C. perfringens FP spores attached to SS chips. These findings should help in developing an effective strategy to inactivate C. perfringens spores adhered to food contact surfaces.     

食品中着色剂的检测方法研究进展

着色剂是食品添加剂中的一大类分支,在食品加工和生产中有着广泛的应用。由于食品的基质类型复杂多样,着色剂的种类也非常多、性质差异大,给分析检测工作带来挑战。本文对近年来的食品中着色剂的检测方法进行综述,包括样品前处理和分析检测技术,并根据应用方法和适用的食品基质及检测目标物进行分类总结,为进一步开展食品中着色剂的检测方法的研究工作提供参考。     

Prediction of optimal cooking time for boiled potatoes by hyperspectral imaging

Cooking of potatoes causes changes in the microstructure and composition of starch. These changes affect the interaction of light with the starch granules at different regions inside the potato. In this research, the potential of hyperspectral imaging in the wavelength range 400-1000 nm in combination with chemometric tools and image processing for contactless detection of the cooking front in potatoes has been investigated. Partial least squares discriminant analysis (PLSDA) was employed to discriminate between the pixel spectra for the cooked regions and those for the remaining raw regions. In a next step image processing techniques were applied to detect the cooking front in the images obtained by the PLSDA pixel classification. From each of the resulting images with detected cooking fronts, the ratio of the remaining raw part area over the total potato area was then calculated. Finally, the effect of the cooking time on this ratio was modeled to be able to predict the optimal cooking time. The results illustrate the potential of hyperspectral imaging as a process monitoring tool for the potato processing industry.     

离子色谱法在食品添加剂检测中的应用

随着食品工业的迅猛发展和人民生活水平的不断提高，人们对食品添加剂痕量成分的检测提出了更高的要求，离子色谱因具有快速、简便、灵敏、选择性好等诸多优点而逐渐受到人们的重视。通过对近年来离子色谱在食品添加荆检测中的应用进行介绍，为相关研究提供新的思路和方法。     

氢化物发生-原子荧光光谱法同时测定食品中的镉和锡

为提高食品中镉和锡的检测水平,建立了氢化物发生-原子荧光光谱法同时测定食品中的镉和锡的方法.在最佳实验条件下的检出限:镉0.002 9 ng/ml、锡0.19 ng/ml;线性范围:镉0～2ng/ml,相关系数0.999 8,锡0～100 ng/ml,相关系数0.999 9;在0.5 ng/ml时,镉测定的相对标准偏差为1.5%(RSD),2.5 ng/ml时锡的相对标准偏差为3.1%(RSD);试样加标回收率:镉93.0%～100.5%,锡91.3%～99.2%.该方法具有操作简便、快速、检出限低、灵敏度高、结果准确等优点,适合于各种食品镉、锡的联合测定.     

Citrus canker detection using hyperspectral reflectance imaging and PCA-based image classification method

Citrus canker is one of the most devastating diseases that threaten marketability of citrus crops. Technologies that can efficiently identify citrus canker would assure fruit quality and safety and enhance the competitiveness and profitability of the citrus industry. This research was aimed to investigate the potential of using hyperspectral imaging technique for detecting canker lesions on citrus fruit. A portable hyperspectral imaging system consisting of an automatic sample handling unit, a light source, and a hyperspectral imaging unit was developed for citrus canker detection. The imaging system was used to acquire reflectance images from citrus samples in the wavelength range between 400 and 900 nm. Ruby Red grapefruits with normal and various diseased skin conditions including canker, copper burn, greasy spot, wind scar, cake melanose, and specular melanose were tested. Hyperspectral reflectance images were analyzed using principal component analysis (PCA) to compress the 3-D hyperspectral image data and extract useful image features that could be used to discriminate cankerous samples from normal and other diseased samples. Image processing and classification algorithms were developed based upon the transformed images of PCA. The overall accuracy for canker detection was 92.7%. Four optimal wavelengths (553, 677, 718, and 858 nm) were identified in visible and short-wavelength near-infrared region that could be adopted by a future multispectral imaging solution for detecting citrus canker on a sorting machine. This research demonstrated that hyperspectral imaging technique could be used for discriminating citrus canker from other confounding diseases.     

Development of a sanitizing fabric wipe for use on food contact surfaces

ABSTRACT:  A sanitizer was incorporated into disposable sanitary wipes that were used to eliminate microorganisms on plastic and metal surfaces. These surfaces were inoculated with strains of Bacillus subtilis OSU 494, Enterococcus faecalis OSU 48, Escherichia coli ATCC 29181, Listeria innocua ATCC 33090, Pseudomonas aeruginosa OSU 167, Salmonella enteritidis OSU 799, Staphylococcus epidermidis OSU 838), Candida albicans ATCC 10231, and Aspergillus fumigatus ATCC 10894. These inoculated surfaces were cleaned with the wipes for 5, 10, and 30 s, then organisms surviving on the cleaned surfaces and in the wipes were enumerated. Applying the sanitizing wipe to the plastic and metal surfaces reduced the viability of bacteria (> log 4 for 5 s), yeast cells (> log 5 for 10 s), and fungal spores (< log 4 for all times). The use of large pore sized or thick wipes showed better sanitizing result when compared with the use of the small pore sized and slim wipe. There were no significant differences ( P > 0.05) between surviving numbers on the surface of the plastic compared with that of the metal.     

Hyperspectral reflectance and fluorescence line-scan imaging for online defect and fecal contamination inspection of apples

We have recently developed a rapid online line-scan imaging system capable of both hyperspectral Vis/NIR reflectance and fluorescence in the Vis with UV-A excitation. The hyperspectral online line-scan system was integrated with a commercial apple-sorting machine and evaluated to inspect apples for fecal contamination and defects at a processing line speed of over three apples per second. Results showed that fluorescence imaging (using a two-band ratio) could achieve detection of fecal spots on artificially contaminated apples with a 100% detection rate and no false positives regardless of the presence of defects. A NIR two-band reflectance ratio coupled with a simple classification method based on the mean intensity and homogeneity of the ratio achieved a 99.5% apple defect classification accuracy with a false positive rate of only 2%. The presented NIR processing regime overcame the presence of stem/calyx on apples that typically has been a problematic source for false positives in the detection of defects. The most significant and important outcome of this investigation is a line-scan inspection system that can potentially provide the capability for current sorting mechanisms, such as by size and color, as well as additional sorting for quality and safety attributes of food products. This line-scan based online imaging system offers great potential as a value-added dynamic inspection system due to its capability for multi-tasking to meet a variety of inspection objectives. A multi-tasking inspection system that can meet current industry sorting needs with the added benefit of safety inspection without requiring significant modification of existing infrastructure or incurring significant costs may lead the apple industry to consider adopting voluntary measures to further enhance safe production and processing of fruits. Company and product names are used for clarity and do not imply any endorsement by U.S. Department of Agriculture to the exclusion of other comparable products.     

四种不同接触表面蜡样芽孢杆菌菌膜形成的影响

为了解食源性致病菌蜡样芽孢杆菌在食品加工环境中菌膜形成能力,以玻璃、不锈钢、聚氯乙烯、聚丙烯为接触面,采用超声波平板菌落计数法测定不同环境因素(温度、pH、氯化钠、葡萄糖、苯甲酸钠及山梨酸钾)、不同材料表面蜡样芽孢杆菌(B.cereus)菌膜形成的变化趋势。结果表明:四种材质表面形成B.cereus菌膜能力的大小顺序为:玻璃 > 不锈钢 > 聚氯乙烯 > 聚丙烯。其中,30 ℃,pH7.0时菌膜形成量最大,添加低浓度葡萄糖(4.0%)或氯化钠(0.5%)对B.cereus菌膜形成有显著促进作用(p<0.05),添加0.15%苯甲酸钠、山梨酸钾的菌膜形成量显著高于添加0.10%的菌膜形成量(p<0.05)。本研究为蜡样芽孢杆菌风险评估提供基础数据,为食品工业蜡样芽孢杆菌菌膜的预防和控制奠定基础,为改进蜡样芽孢杆菌的清洗控制措施提供参考。     

Automatic nematode detection in cod fillets (Gadus morhua L.) by hyperspectral imaging

Detection of objects embedded in tissue, using visible light, is difficult due to light scattering. The optical properties of the surrounding tissue will influence the spectral characteristics of the light interacting with the object, and the spectral signature observed from the object will be directly affected. A method for calibrating the spectral signature of small objects, embedded in translucent material, by the estimated local background spectrum is presented. The method is evaluated under industrial conditions in a new hyperspectral imaging system for automatic detection of nematodes in cod fillets. The system operates at a conveyor belt speed of 400 mm/s which meets the industrial required speed of assessing one fillet per second. The local calibration method reduces the number of spectra needed to be classified by 89.6%. For one or more false alarms in 60% of the fillets sampled after the trimming station, the Gaussian maximum likelihood classifier detects 70.8% and 60.3% of the dark and pale nematodes, respectively. This is better than what is previously reported using a higher resolution instrument on a slow moving conveyor belt, and comparable or better to what is reported for manual inspection under industrial conditions.     

荧光方法在酶抑制农药残留快速检测中的研究进展

农药残留污染是农产品质量安全的首要关注因子,基于大型仪器的实验室检测模式难以匹配检测时效性需求。基于乙酰胆碱酯酶活性抑制的农药残留快速检测方法(酶抑制法)具有操作便携、检测速度快等优势,已成为农产品质量安全的常用筛查手段。囿于常规可见光比色法性能,传统的酶抑制法在检测灵敏度方面受到制约,这限制了其进一步的发展。荧光方法利用特征的激发/发射光谱,可以有效降低非特异性干扰,因此将荧光信号作为数据采集技术是改善酶抑制法灵敏度缺陷的有效手段。本文重点介绍了荧光方法在酶抑制农药残留快速检测中的信号响应模式,包括单酶-荧光材料响应、多酶级联响应和酶活性靶向小分子荧光探针响应,还分别总结了不同方法的目标物响应机制、检测效果及应用现状,最后对酶抑制农药残留快速检测的发展方向进行了展望。     

现代成像技术在食品/农产品无损检测中的研究进展

现代成像技术是应用物理技术、电子技术、计算机技术和材料科学等多种技术相互渗透的产物,近些年来也开始应用于食品、农产品的品质检测。本文介绍了现代成像系统的基本构成,阐述了可见光成像技术、光谱成像技术、X射线线性扫描成像技术、CT成像技术、超声成像技术、核磁共振成像技术的特点,及其在食品、农产品检测中的研究应用情况。最后对现代成像新技术在食品、农产品检测中的发展趋势进行了展望。     

气液微萃取技术联用气相色谱-质谱法快速检测包装食品中15种邻苯二甲酸酯

目的建立气液微萃取技术(gas liquid microextraction,GLME)联用气相色谱-质谱法(gas chromatography-mass spectrometry,GC-MS)快速检测包装食品中15种邻苯二甲酸酯(phthalic acid esters,PAEs)的方法。方法称取0.1 g样品放入GLME中进行萃取、净化、浓缩,加入20 ng仪器内标,定容至100μL,利用GC-MS对5种包装食品中15种PAEs的浓度进行检测。结果样品中检测出邻苯二甲酸二异丁酯(diisobutyl phthalate,DIBP)、邻苯二甲酸二丁酯(dibutyl phthalate,DBP)、邻苯二甲酸二甲氧基乙酯(dimethoxyethyl phthalate,DMEP)、邻苯二甲酸二(2-丁氧基)乙酯(bis(2-butoxyethyl)phthalate,DBEP)、邻苯二甲酸二环己酯(dicyclohexyl phthalate,DCHP)、邻苯二甲酸二(2-乙基)己酯(dioctyl phthalate,DEHP)等6种塑化剂,其中DIBP、DBP、DMEP、DCHP、DEHP等5种塑化剂的检测率达到100%。该方法可以在5 min内完成萃取、净化、浓缩等步骤,回收率为55.2%~121.9%和相对标准偏差(relative standard deviation,RSD)小于20.0%。结论本方法实现了对于包装食品中塑化剂的快速检测,为以后的现场检测塑化剂打下了坚实的基础。     

Analysis of fumonisins in corn-based food by liquid chromatography with fluorescence and mass spectrometry detectors

The presented procedure involves an extraction with methanol–water, centrifugation and cleanup with immunoaffinity columns. A comparison study between fluorescence detector, mass spectrometry, and tandem mass spectrometry with a triple quadrupole (QqQ) analyzer using an electrospray ionisation interface for the determination of fumonisin B₁ and B₂ in corn-based products has been performed.