Efficiency and safety evaluation of photodegradation of Aflatoxin B1 on peanut surface

A photodegradation study of Aflatoxin B₁ (AFB₁) on peanut surface was performed under UV irradiation at different UV irradiation intensities. With an initial quantity of 10 ng of AFB_1, it can be degraded thoroughly within 80 min under the intensity of 800 μw cm^?2. The photodegradation pathway of AFB₁ on the peanut surface was proposed. Mutagenesis and cytotoxicity were assessed after exposure to different concentrations of AFB₁ and the mixtures of photodegradation products on the peanut surface. The results of the Ames and in vitro cytotoxicity assay, providing clues to the assessment of safety issues of UV method applied in AFB₁ decontamination, indicate that photodegradation products on the peanut surface has no toxicity, which can be explained by the differences in the chemical nature of the test compounds before and after UV irradiation.     

Safety evaluation of aflatoxin B1 in peanut oil after ultraviolet irradiation detoxification in a photodegradation reactor

The high incidence of aflatoxin B₁ (AFB₁) in peanut oil has caused wide public concern in the world. Many studies have verified that ultraviolet (UV) irradiation can degrade AFB₁ in foods. A new photodegradation reactor has been developed to study the photodegradation efficiency of AFB₁ in peanut oil, and the safety of peanut oil was evaluated after UV irradiation detoxification based on the mutagenicity of Salmonella typhimurium tester strains and cytotoxicity of HepG2 cells. The results showed that AFB₁ in peanut oil could be decomposed efficiently using the photodegradation reactor. AFB₁ was decreased from 51.96 ± 4.24 to 7.23 ± 0.59 μg kg^?1 in 10 min and reduced by 86.08% compared with that of the negative control. The residual AFB₁ in peanut oil was far less than the limit level set by Chinese government (20 μg kg^?1). The Ames test and cell viability assay revealed that 10 min of UV irradiation reduced significantly the toxicity of AFB₁ in peanut oil. All the results suggest that the deleterious effects of AFB₁ can be highly reduced by UV irradiation in the photodegradation reactor, and the reactor can be applied in a large scale in detoxification of AFB₁ in peanut oil in the oil industry.     

Degradation of aflatoxin B<Subscript>1</Subscript> in aqueous medium through UV irradiation

Mutagenesis and cytotoxicity were assessed after exposure to different concentrations of AFB₁ and the mixtures of photodegradation products in water (Pw). The Ames test, employing Salmonella typhimurium tester strains TA98 and TA100, was employed to evaluate the residual toxicity of Pw, and the results indicated that the mutagenic activity of UV-treated samples was lower compared with that of untreated samples, but not eliminate absolutely. After exposure of the HepG2 cells to these compounds for different times and concentrations, the cytotoxicity of Pw decreased approximately 40% compared to AFB₁, and a small amount of cells were observed dead by the inverted phase-contrast microscope. The results of the Ames and in vitro cytotoxicity assay, providing clues to the assessment of safety issues of UV method applied in AFB₁ decontamination, indicate that Pw are less toxic than AFB₁, which can be explained by the differences in the chemical nature of the test compounds.     

Quantitative evaluation of resveratrol enrichment induced by UV stimulus in harvested grapes

A mathematical model was proposed to quantitatively describe resveratrol induction in harvested grapes. In the model, k₁ and k₂ were defined, which were the reaction rate constants for induction during direct UV irradiation and for the time-delayed induction after removing UV irradiation, respectively. During storage after UV irradiation, k₂ decreased with time, whereas k₁ remained constant. The portion induced by the direct irradiation effect was much more than that induced by the time-delayed effect. When UV energy of 610.2 mJ/cm² was applied to ‘Gerbong’ grapes with an initial resveratrol content of 1.15 μg/g, their contents were 8.99 and 9.20 μg/g at day 1 and 6 during storage at 0°C, respectively. In the same situation, resveratrol content of 8.99 μg/g improved to 10.56 μg/g during storage at 20°C. This approach which enriched a health-functional compound through the modulation of metabolism after harvest might be a valueadding method for fresh food industry.     

Electrochemical sensor based on Prussian blue nanorods and gold nanochains for the determination of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

In this paper, a novel electrochemical sensor for the detection of H₂O₂ was proposed based on gold nanochains and prussian blue nanorods (PB@MWCNTs), which were synthesized with multiwall carbon nanotubes (MWCNTs) as a template. With the introduction of MWCNTs and the gold nanochains, the proposed system shows synergy among the Prussian blue (PB), MWCNTs, and the gold nanochains, which amplifies the H₂O₂ sensitivity greatly. A linear range from 1.75 × 10⁻⁶ to 1.14 × 10⁻³ M with a detection limit of 0.5 × 10⁻⁶ M (S/N = 3) and a high sensitivity 300 μA mM⁻¹ cm⁻² for H₂O₂ detection is obtained. Moreover, the sensor exhibits good repeatability and stability.     

Degradation of aflatoxin B1 in peanut meal by electron beam irradiation

The effects and safety of electron beam irradiation (EBI) treatment on the detoxification of aflatoxin B₁ (AFB₁) in the peanut meal were evaluated in this article. The AFB₁ degradation was predominantly affected by both initial AFB₁ and water concentrations. The degradation of AFB₁ in the selected concentrations (0.5–5 ppm) was proven to follow pseudo first-order reaction kinetics (R² > 0.95). The AFB₁ degradation was faster when the initial concentration was 5 ppm and the moisture content was 21.47%, in comparison with the initial concentration of 1 ppm and 0.5 ppm and the moisture content of 14.32% and 8.74%, respectively. The Ames and cytotoxicity tests were employed to evaluate the residual toxicity of EBI-treated peanut meal. The mutagenic activity of EB-treated samples was completely lost compared with that of untreated samples and the degradation products in peanut meal has almost no cell toxicity.     

Occurrence of Aflatoxins and Ochratoxin A in Baby Foods in Portugal

Infants have a more restricted diet and they generally consume more food on a body weight basis than adults. Therefore, the significance and potential health risk of any contaminant in foods consumed by infants is increased and diligent attention must be paid to this particular area. The present study aims to determine the occurrence of aflatoxin M₁ (AFM₁), aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) in processed cereal-based foods (flours) and infant formulae (milk powder) available in the Portuguese market, both sold as conventional and organic origin. Mycotoxin determination was carried out using a method previously applied to duplicate diet samples. This method employed chloroform extraction, liquid–liquid extraction, immunoaffinity column (IAC) cleanup and HPLC analysis with fluorescence detection after post-column derivatisation. Quantification limits were 0.014, 0.004 and 0.028 μg kg⁻¹ for AFM₁, AFB₁ and OTA, respectively. These toxins could only be quantified in 12 of 27 analysed samples (15 positive results): two samples with AFM₁, two samples with AFM₁ and OTA, one sample with AFB₁ and OTA and seven samples with OTA. Positive results concerned four for AFM₁ (26%), one for AFB₁ (7%) and ten for OTA (67%). For these samples, contents ranged between 0.017–0.041 μg AFM₁ kg⁻¹, 0.034–0.212 μg OTA kg⁻¹, and one sample had a value of 0.009 μg AFB₁ kg⁻¹. Considering the presented results, we could provisionally conclude that the presence of these mycotoxins in baby foods does not constitute a public health problem. These are the first results concerning the occurrence of mycotoxins in marketed baby foods in Portugal and this is the first study using the HPLC method, proposed for duplicate diets, in baby food sample analysis.     

检测角度对激光诱导荧光光谱技术检测花生油AFB1污染的影响研究

近年来,近红外光谱、高光谱等快速无损检测技术,被广泛应用于农产品中黄曲霉毒素B₁(Aflatoxin B₁, AFB₁)的检测。但这些方法主要是根据黄曲霉改变样品本身的结构结合化学计量学方法间接检测样品中AFB₁,无特异性。因此,本研究拟利用研发的激光诱导荧光(laser induce fluorescence, LIF)技术获取污染AFB₁花生油的荧光光谱,建立精确无损检测花生油中AFB₁的定性、定量方法。首先,人工制备7种不同AFB₁污染水平的花生油样品,同时设置对照组。其次利用研发的LIF系统从不同角度检测样品的荧光光谱信号。最后,对获取的光谱进行分析。结果显示,三个检测角度的荧光强度在400-800 nm内均随着AFB₁污染水平的增加而增加,定性和定量的结果均是当检测荧光角度为90度时表现最优。表明当检测角度为90度时,LIF技术可以作为一种快速、精确的方法来判定花生油中AFB₁污染水平。     

Relationship between growth of food‐spoilage yeast in high‐sugar environments and sensitivity to high‐intensity pulsed UV light irradiation

The relationship between prior growth of food‐spoilage yeast in high‐sugar environments and their subsequent survival postpulsed UV (PUV) irradiation was investigated. Test yeast were separately grown to early stationary phase in YPD broth containing increasing concentrations of glucose (1–50% w/v) and were flashed with ≤40 pulses of broad‐spectrum light at lamp discharge energy settings of 3.2, 7.2 and 12.8 J (equivalent to UV doses of 0.53, 1.09 and 3.36 μJ cm^?2, respectively) and their inactivation measured. Findings showed that prior growth in high‐sugar conditions (≥30% glucose w/v) enhanced the sensitivity of all nine representative strains of Zygosaccharomyces bailii, Z. rouxii and Saccharomyces cerevisiae yeast to PUV irradiation. Significant differences in inactivation amongst different yeast types also occurred depending on amount of UV dose applied, where the order of increasing sensitivity of osmotically stressed yeast to PUV irradiation was shown to be Z. rouxii, Z. bailii and >S. cerevisiae. For example, a 1.2‐log order difference in CFU mL^?1 reduction occurred between Z. bailii 11 486 and S. cerevisiae 834 when grown in 50% w/v sugar samples and treated with the uppermost test UV dosage of 3.36 μJ cm^?2, where these two yeast strains were reduced by 3.8 and 5.0 log orders, respectively, after this PUV treatment regime compared to untreated controls. The higher the UV dose applied the greater the reduction in yeast numbers. For example, a 1.0‐, 1.4‐ and 4.0‐log order differences in CFU mL^?1 numbers occurred for S. cerevisiae 834 grown in 15% w/v sugar samples and then treated with PUV dose of 0.53, 1.09 and 3.36 μJ cm^?2, respectively. These findings support the development of PUV for the treatment of high‐sugar foods that are prone to spoilage by osmotolerant yeast.     

Determination of aflatoxins in edible oil from markets in Hebei Province of China by liquid chromatography–tandem mass spectrometry

Analysis of aflatoxin B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁) and G₂ (AFG₂) in 76 edible oil samples (peanut oil, soybean oil, corn embryo oil and blended oil) was performed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The oils were sampled from three areas (Shijiazhuang, Baoding and Tangshan) of Hebei Province of China. AFB₁ was detected in 22 samples representing 28.9%, followed by AFB₂ (7.89%) and AFG₁ (3.95%), while no AFG₂ contamination was detected in any samples. AFB₁ levels in oil samples ranged 0.14–2.72?µg?kg^?1 and AFB₂ ranged 0.15–0.36?µg?kg^?1, while lower levels of 0.01–0.02?µg?kg^?1 for AFG₁ were recorded. The paper is part of an on-going investigation of aflatoxin contamination in Chinese edible oils.     

Aflatoxin B1 in peanut oil from Western Guangdong,China, during 2016–2017

Aflatoxin B₁ (AFB₁) occurrence in peanut oil samples randomly collected from family workshops in western Guangdong during 2016–2017 (n = 427) was surveyed. AFB₁ content was screened by enzyme-linked immunosorbent assay (ELISA) protocol and analytically confirmed with an UPLC-MS/MS method. The limit of detection of the ELISA method was 1.08 μg kg^?1. The recovery values ranged from 84.4 to 92.6% with relative standard deviations of 2.2 to 4.8%. AFB₁ was quantified in 47 samples (22.5%) with a range of 15.4–49.9 μg kg^?1 in 2016 and in 33 samples (15.1%) with 8.8–22.2 μg kg^?1 in 2017, respectively. The AFB₁ contamination in peanut oil was season-depended in western Guangdong with the worst case in spring (24.2–37.9%). Overall, a significant reduction of AFB₁ occurrence was observed in western Guangdong after 2016. It is advisable to control AFB₁ in bulk and self-pressed oil from family workshops and regulate it mandatorily if necessary.     

食用植物油中黄曲霉毒素B1调查分析

调查了浙江省食用植物油中黄曲霉毒素B_1(AFB_1)的污染情况。根据浙江省食用植物油生产消费的实际情况,2016年9—12月,采用统计学方法采集151家食用植物油经销企业的花生油、玉米油、大豆油、菜籽油、油茶籽油、葵花籽油、芝麻油、调和油8大类散装油和定型包装油,共1 208个样品,高效液相色谱法测定AFB_1含量。结果表明:22个样品检出AFB_1,检出率为1.8%,超标率为0.0%;其中花生油、葵花籽油、玉米油和调和油检出AFB_1,浙江省特产的油茶籽油和菜籽油未检出AFB_1,散装油中AFB_1检出率(3.8%)是定型包装油(0.9%)的4.22倍,食用植物油样品中AFB_1含量均低于国家限量标准。     

Properties of <Emphasis Type="Italic">Aspergillus subolivaceus</Emphasis> free and immobilized dextranase

Aspergillus subolivaceus dextranase is immobilized on several carriers by entrapment and covalent binding with cross-linking. Dextranase immobilized on BSA with a cross-linking agent shows the highest activity and considerable immobilization yield (66.7%). The optimum pH of the immobilized enzyme is shifted to pH 6.0 as compared with the free enzyme (pH 5.5). The optimum temperature of the reaction is resulted at 60 °C for both free and immobilized enzyme. Thermal and pH stability are significantly improved by the immobilization process. The calculated K _m of the immobilized dextranase (14.24 mg mL⁻¹) is higher than that of the free dextranase (11.47 mg mL⁻¹), while V _max of the immobilized enzyme (2.80 U μg protein⁻¹) is lower than that of the free dextranase (11.75 U μg protein⁻¹). The immobilized enzyme was able to retain 76% of the initial catalytic activity after 5.0 cycles.     

Ultraviolet Treatment of Orange Juice to Inactivate <Emphasis Type="Italic">E. coli</Emphasis> O157:H7 as Affected by Native Microflora

The effect of yeast concentration on ultraviolet (UV) inactivation of five strains of Escherichia coli O157:H7 from different sources, inoculated both individually and simultaneously in orange juice, was analyzed and mathematically modeled. The presence of yeast cells in orange juice decreases the performance of UV radiation on E. coli inactivation. UV absorption coefficients in the juice increased with increasing yeast concentration, and higher UV doses were necessary to inactivate bacterial strains. UV intensities of I = 3.00 ± 0.3 mW/cm² and exposure times (t) between 0 and 10 min were applied; radiation doses (energy, E = I × t) ranging between 0 and 2 J/cm² were measured using a UV digital radiometer. All the tested individual strains showed higher resistance to the treatment when UV radiation was applied at 4 °C in comparison to 20 °C. UV inactivation of E. coli O157:H7 individual strain was satisfactory fitted with a first order kinetic model. A linear relationship was found between UV absorptivities and D values (radiation doses required to decrease microbial population by 90%) for each strain. The dose required to reach 5-log reduction for the most unfavorable conditions that is the most UV resistant strain, and maximum background yeast concentration was 2.19 J/cm² at 4 °C (corresponding to 11 min of UV treatment) and 2.09 J/cm² at 20 °C (corresponding to 10.55 min of UV treatment). When a cocktail of strains was inoculated in orange juice, the logistic equation was the best model that fits the experimental results due to the deviation from the log-linear kinetics. The UV resistance between strain cocktail and single strain were mathematically compared. Slopes of the decline curves for strain cocktail at high UV doses were lower than the slopes of the log-linear equation calculated for the individual strains, even for the most resistant one. Therefore, microbial inactivation tests using a cocktail of strains are particularly important to determine the performance of the UV inactivation treatment.     

An Improved Chemiluminescence Immunoassay for the Ultrasensitive Detection of Aflatoxin B<Subscript>1</Subscript>

An indirect competitive chemiluminescence (CL) immunoassay based on Fe₃O₄@SiO₂@Au magnetic nanoparticles (Au-SCMPs) has been optimized and developed for the detection of aflatoxin B₁ (AFB₁). To improve the detection sensitivity and efficiency, this method combines 2′,6′-dimethylcarbonylphenyl-10-sulfopropyl acridinium-9-carboxylate 4′-NHS ester (NSP-DMAE-NHS) as a new kind of high efficient luminescence reagent with a simplified separation procedure based on the optimized Au-SCMPs. Superparamagnetic nanoparticles were coated with different sizes of Au colloids (18, 30, and 50 nm), and their capacities in immobilization of bovine serum albumin (BSA) were investigated. The BSA-AFB₁ conjugate (BSA-AFB₁) was immobilized on the optimized Au-SCMPs and competed with the free AFB₁ for specially binding the NSP-DAME-NHS-labeled anti-AFB₁ antibody (mAb-AFB₁). After the indirect competitive immunoreactions and magnetic separation, the CL of the nanoparticles was measured by a homemade luminescent measurement system. Under the optimum conditions, the IC₅₀ value was 0.07 ng mL^?1 and the limit of detection (LOD) of AFB₁ was 0.01 ng mL^?1, respectively. The result shows a much lower IC₅₀ and LOD than that typically achieved by ELISA. This proposed immunoassay method was rapid, low-cost, and suitable for the detection of AFB₁.     

Development of an innovative apparatus using UV‐C for controlling the number of microorganisms in raw milk after milking

This study was conducted to investigate the effect of UV‐C irradiation on the reduction of microorganisms in raw milk. The experiments were carried out by varying the flow rates of 2, 4 and 7 L/min with 39W and 48W UV‐C. The number of microorganisms was reduced by 4.70 (39W) and 4.60 log₁₀ CFU/mL (48W) at 120 min. With the residence time of 4.95 s and the UV‐C doses of 98 and 109.9 mJ/cm² at 253.74 nm, the reduction of microorganism was clearly observed with no significant influence of different UV‐C power settings on the oxidation of milk fat.     

Antioxidant capacity and antioxidative compounds in barley (<Emphasis Type="Italic">Hordeum</Emphasis><Emphasis Type="Italic">vulgare</Emphasis> L.) grain optimized using response surface methodology in hot air roasting

Response surface methodology was used to predict optimum conditions for hot air roasting of barley grains (temperature, time, and amount). Antioxidant capacity in the grains was highest under optimum conditions of 250 °C, 63.5 min and 42 g (one and a half layers). A correlation of R ² = 0.74 (p < 0.05) was found between 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and total phenolic contents. Ethanol and aqueous extracts were prepared from grains roasted under optimum conditions and assessed for antioxidant capacity. Antioxidative compounds in the extracts were then identified using GC–MS. The IC₅₀ value of ethanol extract was significantly lower (11.45 μg mL^–1) than that of aqueous extract (33.54 μg mL^–1) and α-tocopherol (12.6 μg mL^–1) but higher than BHT (9.59 μg mL^–1). The same trend was observed in linoleic acid assay. In reducing power, the ethanol extract and α-tocopherol were not significantly different. Phenolic acids p-hydroxybenzaldehyde, vallinic and gallic acids were identified as the major compounds in the extracts. The results obtained from this study show that it is possible to optimize antioxidant capacity in barley grains during roasting.     

Evaluation of Nano Zinc (ZnO) for Surface Enhancement of ATR–FTIR Spectra of Butter and Spread

The effect of nano zinc (ZnO) particles in surface enhancement of attenuated total reflection–Fourier transform mid-infrared spectroscopy (ATR–FTIR) has been studied in butter and spread. Due to the health implications associated with consumption of trans fats, the studies also included the determination of band corresponding to trans fats of butter/spread in the nano-zinc-treated samples. The FTIR spectra of nano-zinc-treated butter showed enhancement of bands related to (―C―O, ―CH₂―) at wave number 1,238 cm⁻¹ and (O―C―C) band of esters at wave number 1,100 cm⁻¹. Shifting in wave number to 1,150 cm⁻¹ and reduction in its peak intensity was observed with the band corresponding to 1,162 cm⁻¹ (―C―O stretch). Reduction in peak intensity of the bands at about 2,915 and 2,850 cm⁻¹ (C―H groups) was also observed. In the case of spread, nano zinc reduced the peak intensities of FTIR bands at 2,915 cm⁻¹, 2,850 cm⁻¹ (―C―H― (CH₂) stretches), 1,746 cm⁻¹ (―C═O ester), 1,465 cm⁻¹ (―C―H (CH₂, CH₃)), 1,375 cm⁻¹ (―C―H (CH₃)) and 1,156 cm⁻¹ (C―O, ―CH₂). Trans fats band corresponding to ═C―H stretch (trans bonds, 966 cm⁻¹), was observed in pure butter and spread. Trans fatty acids in butter and spread were quantified with the aid of calibration/validation standards using trielaidin and triolein and by using partial least squares regression analysis. However, the band at 966 cm⁻¹ was hindered in Zn-treated butter and reduced in Zn-treated spread.     

Lipase-catalyzed acylation of <Emphasis Type="SmallCaps">l</Emphasis>-carnitine with conjugated linoleic acid in [Bmim]PF<Subscript>6</Subscript> ionic liquid

Improving significantly the acylation reaction of l-carnitine with conjugated linoleic acid catalyzed by lipase needs to select an efficient and suitable reaction medium that is not only polar but also hydrophobic. [Bmim]PF₆ which is satisfied with the above two requirements was applied as the reaction medium. The optimal reaction conditions were: Novozyme 435 as the catalyst, 5:1 of molar ratio of fatty acid to l-carnitine, 40 g L⁻¹ lipase, 0.22 a_W of initial water activity, 125 g L⁻¹ molecular sieves (they were added within 0–3 h of reaction time), 60 °C of reaction temperature, 200 rpm of rotation speed, 32 h of reaction time. The overall conversion could reach 98.27%. The conversion in [Bmim]PF₆ was 2.13 and 1.56 times higher than that in acetonitrile and in solvent-free system, respectively. The lipase in the present work could be used eight times. [Bmim]PF₆ as the reaction medium was better than acetonitrile and solvent-free system.     

Decontamination of aflatoxin B1‐contaminated corn by ammonium persulphate during fermentation

The decontamination of aflatoxin B₁(AFB₁)‐contaminated corn, which is required if the corn is to be suitable for alternative use, by an ammoniation–fermentation integrated process was studied. This process could be used for the production of fuel ethanol from aflatoxin‐containing corn. Different concentrations (0.25, 0.50, 1.00, 1.5 and 2.0% w/w) of ammonium persulphate were tested in the detoxification of AFB₁‐contaminated corn during fermentation. In order to increase the decontamination of corn, 0.5 and 1.0% (w/w) azodicarbonamide, benzoyl peroxide and hydrogen peroxide were tested. Peroxides were added at three different stages of the fermentation process: liquefaction, saccharification and fermentation. Levels of AFB₁ and ethanol were determined after each fermentation process. Treated corn was tested for mutagenic potential using the Ames test with TA100 tester strain and pure AFB₁ as positive control. Addition of 2.0% (w/w) ammonium persulphate caused the highest level of decontamination without affecting ethanol production. Addition of peroxides did not significantly (P < 0.05) increase ethanol production or significantly (P < 0.05) improve the decontamination process. The best processes for decontamination of corn and for ethanol production included the addition of 2.0% (w/w) ammonium persulphate for both and of 1.0 and 0.5% (w/w) benzoyl peroxide respectively. All treated corn samples showed no mutagenic potential. Possible industrial use of these processes is discussed. © 2002 Society of Chemical Industry