An investigation into low‐temperature nitrogen plasma environment effect on the content of polyphenols during withering in made Kenyan tea

Low‐temperature nitrogen plasma (LTNP) was used to wither green tea leaf to study its effect on the polyphenol content. Using a dielectric barrier discharge chamber to provide the LTNP environment, green tea leaf was withered at various withering times. Made tea samples indicated that LTNP had an effect on polyphenol content. The highest polyphenol content of 78.56 mg g^?1 in made tea was attained in 1 h after which it showed a decreasing trend with increasing retention time. For comparison purposes, green tea leaf was also withered in nonplasma environments. Highest polyphenol content of 133.4 mg g^?1 in made tea was attained in a sample withered anaerobically in nitrogen gas at room temperature and atmospheric pressure for 18 h. In another sample, green tea leaf was directly macerated and dried without withering and fermenting and had polyphenol content of 101.91 mg g^?1 in made tea. These contents were compared with green tea 4, purple tea and oolong tea that are currently manufactured in Kenya.     

Development of a class-specific monoclonal antibody-based ELISA for aflatoxins in peanut

Three class-specific monoclonal antibodies against aflatoxins were screened by a designed strategy in which aflatoxin G₂ was used as competitor in the screening ELISA system. With a high cross-reactivity (65%) to aflatoxin G₂, antibody 10C9 had the most similar sensitivity for five aflatoxins (AFB₁, AFB₂, AFG₁, AFG₂ and AFM₁), whose I₅₀ values were in a range of 2.1–3.2 ng ml⁻¹. So, antibody 10C9 was selected to develop an ELISA for determination of aflatoxin B₁, B₂, G₁, G₂ and total of them in peanut samples. And spiked recoveries were from 87.5% to 102.0%. The results indicate that the ELISA developed can accurately determine total aflatoxins in samples of peanuts after the simple and rapid extraction procedure.     

Fluorescence polarization immunoassay based on a monoclonal antibody for the detection of ochratoxin A

A fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody for the determination of ochratoxin A (OTA) was developed. Fluorescein‐labelled OTA derivative (tracer) was synthesized and purified by thin‐layer chromatography. The optimized OTA FPIA had a dynamic range from 5 to 200 ng mL^?1 with IC₅₀ value of 30 ng mL^?1 and a detection limit of 3 ng mL^?1. The method developed was characterized by high specificity and reproducibility. Cross‐reactivity with other mycotoxins (zearalenone, aflatoxins, patulin and T‐2 toxin) was negligible (<0.1%). Methanol extracts of barley samples were used for the analysis. The results of OTA determination in barley were compared with those determined by indirect competitive enzyme‐linked immunosorbent assay (ELISA). Recoveries for the samples spiked at 50, 100 and 500 ng g^?1 levels were 91, 90 and 97%, respectively, for FPIA, and 98, 98 and 102%, for ELISA. Naturally contaminated barley samples were analysed by these methods but some disagreement was observed between the results. The FPIA method can be applied for screening of food samples for OTA residues without a complicated clean‐up.     

Polyphenolic composition and in vitro antioxidant activities of native‐ and tannase‐treated green tea extracts

The antioxidant activities of native‐ and tannase‐treated green tea extracts along with their major polyphenol components were investigated. The polyphenolic content and composition of the tea before and after tannase treatment were determined by liquid chromatography coupled with mass spectrometry (LC‐MS). Approximately 99% of the (?)‐epigallocatechin gallate (EGCG) and (?)‐epicatechin gallate (ECG) in green tea extract were converted by tannase to (?)‐epigallocatechin (EGC) and (?)‐epicatechin (EC), respectively, after 30 min. Biotransformed green tea exhibited a significantly higher DPPH˙ radical scavenging activities than native green tea (EC₅₀ value of 0.024 ± 0.001 and 0.044 ± 0.001 mg mL^?1, respectively). Kinetic parameters such as scavenging rate and stoichiometry were calculated. The rate of DPPH˙ radical scavenging activities for tannase‐treated green tea extract was shown to be higher than native green tea extract.     

Antimutagenic and antimicrobial activities of pu-erh tea

The biological action of water extract of pu-erh tea (WEPT) was evaluated by Salmonella mutagenesis assay and bacteria test. Like green tea, oolong tea and black tea, WEPT showed neither cytotoxicity and nor mutagenicity toward Salmonella typhimurium TA98 and TA100 with or without S9 mix (an external metabolic activation system). WEPT at 0.5-5 mg/plate expressed a dose-dependent inhibitory effect against both the mutagenicity of aflatoxin B₁ (AFB₁), an indirect mutagen which requires metabolic activation, and 4-nitroquinoline-N-oxide (NQNO), a direct mutagen, in Salmonella typhimurium TA98 and TA100. In general, the antimutagenic activity of WEPT against AFB₁ and NQNO was weaker than other tea extract because of the least amount of total catechin in WEPT. For antimicrobial action, WEPT, green tea, oolong tea and black tea at 2.0 mg/ml showed inhibitory effect on growth of Staphylococcus aureus and Bacillus subtilis, but no effect on Escherchia coli. Obviously, WEPT has potential antimicrobial effect on gram-positive Staphylcoccus aureus and B. subtilis than that of gram-negative E. coli. In addition, caffeine and epicatechin (EC), main polyphenolic compounds in WEPT, showed both antimutagenic and antimicrobial effect against strains mentioned above, which may partially account for the antimutagenic and antimicrobial action of pu-erh tea.     

A sensitivity-improved enzyme-linked immunosorbent assay for fenvalerate: a new approach for hapten synthesis and application to tea samples

BACKGROUND: Fenvalerate has been widely used for the control of many common pests, but residues of this pesticide have been found in some agricultural crops. China is a large exporter of tea products; thus monitoring of pesticide residues in tea products has become increasingly important. In this study, a method of competitive direct enzyme‐linked immunosorbent assay (CD‐ELISA) for the rapid detection of fenvalerate in tea sample was developed. RESULTS: A polyclonal antibody against fenvalerate (FEN) was produced by the hapten with the characteristic moiety of fenvalerate. After acidification, the hapten was synthesized from 2‐(4‐chloro‐phenyl)‐3‐methyl‐butyric acid and aminocaproic acid methyl ester. The CD‐ELISA method developed has a high sensitivity of detection: 9 µg L^?1 for IC₅₀ and 0.5 µg L^?1 for IC₁₅. Fenvalerate was treated with 0.5 mmol L^?1 NaOH–methanol solution to improve its solubility by isomerization. In the tea sample, the detection limit of fenvalerate was 0.16 mg L^?1. A recovery rate of 76.67–91.43% was obtained from spiked tea. The reliability of the CD‐ELISA method is better in comparison with the gas chromatographic method (R² = 0.9968). CONCLUSION: In this study, a simple and efficient immunoassay method was developed. It is preferable for the rapid determination of fenvalerate residues in tea samples. Copyright © 2011 Society of Chemical Industry     

Immunoaffinity removal and immunoassay for rhodamine B in chilli powder

A rapid and simple immunoassay and a sol–gel‐based immunoaffinity chromatography (IAC) purification method for Rhodamine B (RB) were developed using spiked chilli powder. A polyclonal antibody against RB was generated by immunisation of rabbits with an immunogen hapten. An enzyme‐linked immunosorbent assay (ELISA) was developed that achieved a 50% inhibition (IC₅₀) value of 0.94 ± 0.05 ng mL^?1. The limit of detection of the ELISA method was 1 ng g^?1 in chilli powder. For the IAC, recovery was 68.1–86.2% at 1 ng g^?1 and 72.6–89.3% at 5 ng g^?1 in spiked chilli powder. Fortified samples were analysed by high performance liquid chromatography–mass spectrometry (HPLC–MS) after IAC purification, and the results showed a good agreement between the two methods. The ELISA could be a convenient tool for screening RB residue in foods, and the IAC cleanup procedure coupled with HPLC–MS could be an effective alternative method for the determination of RB in various substances.     

Occurrence of Aflatoxin M1 in raw and processed milk and assessment of daily intake in Lahore,Multan cities of Pakistan

In this survey aflatoxin, M₁ was quantified in raw and processed milk from various areas of two big cities of Punjab province, i.e. Lahore and Multan. The results indicated that approximately 90% of the raw milk samples collected from Lahore city was contaminated with aflatoxin M₁. Similarly, around 92% of the raw milk samples collected from Multan city was contaminated with aflatoxin M₁. All samples of processed milk and tea whiteners were contaminated and 56% of the contaminated processed milk samples and 66% of the contaminated tea whitener samples were violating the maximum limits. The dietary exposure data of AFM₁ among six different groups was calculated, which indicated that the male children population was the most vulnerable group to AFM₁, up to 6.68 ng L^?1 per day and the least affected one was the female group above 20 years of age with 1.13 ng L^?1 per day.     

Mercury and methylmercury levels in the main traded fish species in Hong Kong

This survey was undertaken to determine the levels of aflatoxins in melon seeds. Among 65 samples analyzed by liquid chromatography (LC), the results showed that aflatoxin B₁ (AFB₁) was the major toxins in melon seeds, detected in 58 samples (89.2% of the total) at an average concentration of 8.5?ng?g^?1. The level of AFB₁ in 12 samples exceeded the maximum tolerated level for AFB₁ in Iranian (5?ng?g^?1) regulations; in other words, 18.5% of samples were unfit for human consumption.     

Development of a sensitive and group‐specific polyclonal antibody‐based enzyme‐linked immunosorbent assay (ELISA) for detection of malachite green and leucomalachite green in water and fish samples

BACKGROUND: Malachite green (MG) is widely used in fishery, since it is easily adsorbed by fish during waterborne exposure and is rapidly metabolised into leucomalachite green (LMG). However, both MG and LMG are potential carcinogens, teratogens and mutagens. In this study the LMG derivative bearing an amino group on the phenyl ring was synthesised and coupled to carrier proteins. An LMG polyclonal antibody‐based enzyme‐linked immunosorbent assay (ELISA) was developed and characterised. RESULTS: The ELISA standard curve was constructed with concentrations of 0.1–100 ng mL^?1. The IC₅₀ value for nine standard curves was in the range 0.9–2.6 ng mL^?1 and the limit of detection at a signal‐to‐noise ratio of 3 was 0.02–0.10 ng mL^?1. The cross‐reactivity values of the LMG antibody with MG, crystal violet and leucocrystal violet were 95.25, 29.07 and 212.38% respectively, while less than 0.2% cross‐reactivity was found with eight other compounds. For LMG‐spiked water and fish samples, recoveries were 76.2–95.0% and the correlation coefficient of ELISA with high‐performance liquid chromatography (HPLC) was 0.9752 (n = 7). For (LMG + MG)‐spiked fish samples the results of ELISA were similar to those of HPLC. CONCLUSION: The proposed ELISA can be utilised as an analytical tool for detecting the sum of MG and LMG in water and fish muscle samples. Copyright © 2009 Society of Chemical Industry     

Effect of fermentation by Bacillus subtilis on antioxidant and cytotoxic activities of black rice bran

Black rice bran was fermented with Bacillus subtilis KU3 isolated from Korean traditional food, Kimchi. Antioxidant and cytotoxic activities of the fermented black rice bran were investigated. Total phenolic and anthocyanin contents decreased from 171.54 mg GAE g^?1 and 2.31 mg g^?1 to 139.13 mg GAE g^?1 and 2.12 mg g^?1, respectively, after fermentation. Antioxidant activities determined by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, β‐carotene bleaching and ferric thiocyanate assay were correlated with total phenolic and anthocyanin contents. Non‐fermented black rice bran extract (NFBE) showed greater antioxidant activities than fermented black rice bran extract (FBE). Cytotoxic activities measured by MTT assay showed that both NFBE and FBE had over 50% activities. The cytotoxic activities of FBE against MCF‐7 and HeLa cells were 71.65% and 68.07%, respectively, at 8.0 mg mL^?1, but those of NFBE were lower than 50%. These results suggested that the cytotoxic activity of black rice bran improved through fermentation, while antioxidant activity reduced.     

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.     

Tracking residual organochlorine pesticides (OCPs) in green,herbal, and black tea leaves and infusions of commercially available tea products marketed in Poland

The content of residual organochlorine pesticides (OCPs) was examined in green, herbal, and black tea leaves as well as in their infusions prepared from tea products marketed in the main supermarkets in Poland. It was found that the detected mean levels of organochlorine residues in tea leaves ranged from ?1 dry weight. Among hexachlorocyclohexane isomers, γ-HCH in green tea occurred in the highest concentrations. Among dichlorodiphenyltrichloroethane (DDT) metabolites the highest level of p,p′DDT (1.96 ng g^?1 dw) was in green tea samples. The transfer of OCPs from tea leaves to brew was investigated. The present study revealed that during the infusion process, a significant percentage of the residues, particularly pesticides with high water solubility, were transferred to the infusions. The obtained results show that the percentage transfer of each pesticides from tea to the tea infusions ranged from 6.74% (heptachlor) to 86.6% (endrin). The detected residues were below current MRLs for these pesticides.     

Global occurrence of aflatoxin M1 in milk with particular reference to Iran

Aflatoxin M₁ (AFM₁) is an hydroxylated derivative of aflatoxin B₁ (AFB₁), which occurs in the milk of lactating animals. The aim of the present study was to determine the concentrations of AFM₁ in raw milk samples collected from 18 dairy farms in Qazvin, Iran, over a period of 1 year and compare them with those found in other countries. Samples (30 per farm) were collected in the four seasons, Spring, Summer, Autumn and Winter occurring between April 2009 and March 2010, giving a total of 2160 samples. They were centrifuged and 100 μl of the resulting skimmed milk were tested for AFM₁ contamination by competitive enzyme immunoassay (EIA). All samples (100 %) were contaminated with AFM₁ with concentrations ranging from 0.04 to 148.01 ng.l^?1 and a mean of 38.82 ng.l^?1. Summer samples with a mean of 64.69 ng.l^?1 and autumn samples with a mean of 0.14 ng.l^?1 had the highest and lowest concentrations, respectively, and differed significantly (P?<?0.05). AFM₁ content in 722 samples (33.4 %) was higher than the maximum tolerance limit of 50 ng.l^?1 accepted by the European Union (EU). As contamination of milk with AFM₁ is a potential risk for human health, raw milk should be monitored for its presence.     

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.     

Evaluation of hot and cold extraction of bioactive compounds in teas

This study evaluated the bioactive compounds of different types of tea by comparing hot and cold infusions. A multivariate data analysis was carried out, where the principal components analysis (PCA) and hierarchical cluster analysis (HCA) were used. Phenolic compounds varied between 267.27–2896.00 mg GAE L^?1 and 215.10–7351.33 mg GAE L^?1 for hot (80 °C) and cold extraction (20–25 °C), respectively. In the case of their antioxidant activity, results with DPPH were 43.10‐73.67% for hot extraction and 46.80‐77.13% for cold extraction. The average values for the ABTS˙⁺ method ranged between 2535.43 and 33 300.17 μmol TE L^?1 and between 1110.34 and 38 300.67 μmol TE L^?1, respectively, for hot and cold extraction. Different compounds were identified by liquid chromatography in the samples evaluated, where caffeine presented the higher concentrations in the teas. Samples of green and black tea (hot extraction) and white tea (cold extraction) showed bacteriostatic activity for S. aureus and E. coli. No extract had any bactericide activity. The current study revealed that cold infusion was more efficient in the extraction of bioactive compounds.     

Aflatoxins in sunflower seeds and unrefined sunflower oils from Singida,Tanzania

A total of 61 samples comprising sunflower seeds (40) and unrefined sunflower oils (21) samples collected randomly from Singida, Tanzania were analysed by Reverse Phase-high performance liquid chromatography (RP-HPLC). 15% (6/40) of the seed samples were contaminated with aflatoxin B₁ ranging from limit of detection (LOD) to 218 ng g^?1 with three of them exceeding the European Commission/European Union (EC/EU) and Tanzania Bureau of Standards (TBS)/Tanzania Food and Drug Authority (TFDA) maximum limits of 2 ng g^?1 for AFB₁ in oilseeds. The levels of total aflatoxins (AFT) in seeds ranged from LOD to 243 ng g^?1. Other aflatoxins, except AFG₂, were also detected. For the unrefined sunflower oils, the levels of AFB₁ ranged from LOD to 2.56 ng mL^?1. About 80.9% (17/21) of the analysed oil samples contained AFB₁ of which 17.65% (3/17) exceeded the EC/EU and TBS/TFDA maximum limits of 2 ng mL^?1. Other aflatoxins were also detected in the oils. The measured levels indicate there is a need for food quality education among food processors.     

Tannase from Aspergillus melleus improves the antioxidant activity of green tea: purification and biochemical characterisation

Tannase is an inducible enzyme used extensively in food, feed, pharmaceutical and chemical industries. In this study, tannase production and its biochemical properties were evaluated. From 42 Aspergillus strains analysed for potential tannase selection, Aspergillus melleus yielded the best results. Production was analysed using a complete factorial planning of 2³. Maximum activity (452.55 U mL^?1) was obtained in the optimal conditions of substrate (5.0 g), initial moisture (60%), tannic acid (2%) and 48 h of fermentation. The molecular weight of the purified enzyme was estimated as 69.52 kDa; its optimum temperature and pH were 40 °C and 5.5, respectively. Regarding the chemical effectors used, tannase was inhibited by ZnCl₂, ZnSO₄, Triton X‐100 and SDS. The addition of tannase to green tea improved its antioxidant potential by approximately 85% when compared to the control. The present results suggest that tannase may be used as an adjuvant to increase the antioxidant potential of green tea.     

Aflatoxin levels and exposure assessment of Spanish infant cereals

Aflatoxins (AFB₁, AFB₂, AFG₁ and AFG₂) are immunosuppressant, mutagenic, teratogenic and carcinogenic agents with a widespread presence in foodstuffs. Since human exposure to aflatoxins occurs primarily by contaminated food intake, and given the greater susceptibility of infants to their adverse effects, the quantification of these mycotoxins in infant food based on cereals is of relevance. Aflatoxin levels were determined in 91 Spanish infant cereals classified in terms of non- and organically produced and several types from 10 different manufacturers, using a extraction procedure followed by inmunoaffinity column clean-up step and HPLC with fluorescence detection (FLD) and post-column derivatisation (Kobra Cell system). Daily aflatoxin intake was also assessed. Preliminary analysis showed a valuable incidence of detected infant cereal samples at an upper concentration level than the detection limit for total aflatoxin (66%), corresponding to a 46, 40, 34 and 11% for AFB₁, AFB₂, AFG₁ and AFG₂, respectively. Lower aflatoxin values (median, Q₁, Q₃) in conventional infant cereal (n?=?74, AFB₁: <LOD (n.d.; 0.02), AFB₂: n.d. (n.d.; 0.01), AFG₁: <LOD (n.d.; 0.004), and AFG₂: n.d. (n.d.; <LOD) and total AF (AFtotal): 0.01 (<LOD; 0.04 µg?kg^?1) in comparison with infant cereal ecologically produced (n?=?17, AFB₁: 0.02 (0.02; 0.21), AFB₂: n.d. (n.d.; 0.03), AFG₁: 0.02 (0.01; 0.05), and AFG₂: 0.007 (n.d.; 0.02) and AFtotal: 0.05 (0.03; 0.31 µg?kg^?1) were found. In addition, five organic formulations (3.11, 1.98, 0.94, 0.47 and 0.21 µg?kg^?1) exceeded European AFB₁ legislation (0.10?µg?kg^?1) versus two conventional cereals (0.35 and 0.12 µg?kg^?1). According to the type of infant cereal, those with cocoa had the highest aflatoxin levels. Gluten‐free and cereals with dehydrated fruits had an intermediate level and milk- or honey-based cereals and multi-cereals contained the lowest levels. With the exception of the non-compliant cocoa-based organic formulation, none of the infant cereals analyzed gave a higher intake of 1?ng?kg^?1 body weight per day, suggesting that infants fed on infant cereals are exposed to a low health hazard. Nevertheless, manufacturers are advised for continued efforts in routine monitoring and a more careful selection of raw material to minimize aflatoxin levels in these infant foods.     

Aflatoxins in sunflower and safflower seeds from Iran

Aflatoxin content of 173 sunflower and safflower seeds was determined by HPLC with immunoaffinity column (IAC) clean-up and fluorometric detection. Aflatoxin B₁ contamination was found in 111 samples: in 8 of the sunflower seed samples (16%) at a mean level of 40.68?ng?g^?1 and in 103 safflower seed samples (83.7%) at a mean level of 2.81?±?0.44?ng?g^?1. In 5 sunflower seed samples and 1 safflower seed sample, aflatoxin B₁ levels were higher than the maximum levels of AFB₁ under Iran regulations (5?ng?g^?1). Aflatoxin B₁ levels in 5 sunflower and 2 safflower seed samples were higher than the European Union maximum limit (2?ng?g^?1).