Raymond Coker | University of Greenwich (original) (raw)
Papers by Raymond Coker
A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and... more A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and feeds grown in Bangladesh. The study also included groundnuts utilized as snack food. In the first two phases of the program the samples collected were analyzed only for aflatoxins, but in the third phase, as well as for aflatoxins, samples were tested for the presence of fumonisin B1, ochratoxin A, zearalenone, deoxynivalenol, and T-2 toxin. Of the foods and feeds tested, the incidence of aflatoxin contamination varied from low (rice collected from farmers' stores, 8%) to high (maize, 67%). However, both the average total aflatoxin contents (< 1.0 microg/kg) and the maximum aflatoxin B1 contents (< or = 5.0 microg/kg) recorded for pulses, rice and its various products, and wheat were low. On the other hand, the levels of contamination of maize, roasted and raw groundnuts, and poultry feed were considerably higher, with average total aflatoxin B1 contents of 33, 13, 65, and 7 ...
Medical laboratory sciences
The presence of mycotoxins in a wide range of foodstuffs can lead to many different toxic conditi... more The presence of mycotoxins in a wide range of foodstuffs can lead to many different toxic conditions in both man and domestic animals. The major fungi responsible for producing these toxins are species of Aspergillus, Penicillium, Fusarium and Alternaria, although other genera are involved as well, for example Claviceps, Diplodia and Arthrinium. An overview is given of the major mycotoxins responsible for illnesses following ingestion of contaminated foods, with particular emphasis on the effects produced in humans. Compounds discussed include the aflatoxins, cyclopiazonic acid, tenuazonic acid, the trichothecenes, zearalenone, wortmannin, fumonisins B1 and B2, patulin, ochratoxin A, diplodiatoxin and diplosporin.
British journal of biomedical science
A comparison has been made between pre-column and post-column derivatisation of aflatoxin B1 (AFB... more A comparison has been made between pre-column and post-column derivatisation of aflatoxin B1 (AFB1) during estimation by high-performance liquid chromatography of this toxin in groundnut meal. The effect of the use of different derivatisation reagents on the quantification of aflatoxin B2 (AFB2) has also been evaluated. Both AFB1 and AFB2 were analysed at eight levels of artificial contamination. Five replicate analyses were carried out at each level on both groundnut meal extract (acetone-water, 85:15, v/v) and extraction solvent alone. A statistical evaluation of the results gave limits of detection of 1.1 and 0.3 micrograms/kg for AFB1 and AFB2 respectively, using pre-column derivatisation compared with 1.5 and 0.8 micrograms/kg for the post-column method. Recoveries of over 90% from the spiked groundnut meal extracts were achieved for both derivatisation methods.
Applied and environmental microbiology, 1999
We tested a novel colorimetric toxicity test, based on inhibition of beta-galactosidase activity ... more We tested a novel colorimetric toxicity test, based on inhibition of beta-galactosidase activity in the yeast Kluyveromyces marxianus, for sensitivity to a range of mycotoxins. A variety of trichothecene mycotoxins could be detected. The order of toxicity established with this bioassay was verrucarin A > roridin A > T-2 toxin > diacetoxyscirpenol > HT-2 toxin > acetyl T-2 toxin > neosolaniol > fusarenon X > T-2 triol > scirpentriol > nivalenol > deoxynivalenol > T-2 tetraol. The sensitivity of detection was high, with the most potent trichothecene tested, verrucarin A, having a 50% effective concentration (concentration of toxin causing 50% inhibition) of 2 ng/ml. Other mycotoxins (cyclopiazonic acid, fumonisin B1, ochratoxin A, patulin, sterigmatocystin, tenuazonic acid, and zearalenone) could not be detected at up to 10 micrograms/ml, nor could aflatoxins B1 and M1 be detected at concentrations up to 25 micrograms/ml. This test should be useful ...
Society for Applied Bacteriology symposium series, 1989
1. Introduction, 105s 2. Sampling problems, 106s 2.1 Sampling plans, 108s 3. Errors arising durin... more 1. Introduction, 105s 2. Sampling problems, 106s 2.1 Sampling plans, 108s 3. Errors arising during sample preparation, 109s 4. Analytical procedures, 11 1s 5. Statistical models for sampling plans, 111s 6. Conclusions, 115s 7. References, 115s 106s K. Jewers et al.
Journal of natural toxins, 2002
A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and... more A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and feeds grown in Bangladesh. The study also included groundnuts utilized as snack food. In the first two phases of the program the samples collected were analyzed only for aflatoxins, but in the third phase, as well as for aflatoxins, samples were tested for the presence of fumonisin B1, ochratoxin A, zearalenone, deoxynivalenol, and T-2 toxin. Of the foods and feeds tested, the incidence of aflatoxin contamination varied from low (rice collected from farmers' stores, 8%) to high (maize, 67%). However, both the average total aflatoxin contents (< 1.0 microg/kg) and the maximum aflatoxin B1 contents (< or = 5.0 microg/kg) recorded for pulses, rice and its various products, and wheat were low. On the other hand, the levels of contamination of maize, roasted and raw groundnuts, and poultry feed were considerably higher, with average total aflatoxin B1 contents of 33, 13, 65, and 7 ...
Biotechnology letters, 2000
Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscop... more Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscopy showed no evidence of cytochrome P450, in contrast to microsomes isolated from a control strain of Saccharomyces cerevisiae. Benzo[a]pyrene produced a typical Type I-binding spectrum with microsomes of both yeasts, with K s values of 82 µM (S. cerevisiae) and 70 µM (K. marxianus). While aflatoxin B 1 generated a typical Type I-binding spectrum with microsomes from S. cerevisiae (K s of 178 µM), the toxin did not produce a recognisable binding spectrum with microsomes from K. marxianus.
The Analyst, 1992
A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2,... more A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2, AFG1 and AFG2 in palm kernel samples has been developed by optimizing the sample preparation, solvent extraction, sample clean-up and quantification procedures. The aflatoxins are extracted from a slurried palm kernel sample with an acetone-water (80 + 20, v/v) mixture and the crude extract is cleaned up by solid-phase extraction using a phenyl bonded phase cartridge. The extract is passed through the cartridge with a water-methanol (93 + 7) mixture. Subsequent elution of the aflatoxins retained on the cartridge is achieved with a 3 ml aliquot of chloroform. The aflatoxin content of the eluate is quantified using a bi-directional high-performance thin-layer chromatography procedure. A critical evaluation of the proposed method was carried out by statistical comparison with the British Standard Method. The proposed procedure was shown to be more efficient and precise. Consistent recoveries of over 90% were achieved from spiked palm kernel extracts and detection limits were found to be 3.7, 2.5, 3.0 and 1.3 micrograms kg-1 for AFB1, AFB2, AFG1 and AFG2 aflatoxins, respectively.
Phytochemistry, 1994
ABSTRACT From a 1960s sample of groundnut cake, which had been implicated in the first record of ... more ABSTRACT From a 1960s sample of groundnut cake, which had been implicated in the first record of turkey ‘X’ disease, cyclopiazonic acid has been detected at a level of 31 μg kg−1. The presence of this mycotoxin, along with aflatoxins, explains the toxic symptoms originally recorded after the groundnut cake had been ingested by turkeys.
Magnetic Resonance in Chemistry, 1988
The Statistician, 1994
ABSTRACT Aflatoxins are suspected human carcinogens and levels of contamination are subject to le... more ABSTRACT Aflatoxins are suspected human carcinogens and levels of contamination are subject to legislation. A case-study is presented which examines the application of a sequential acceptance test. The test is based on the analysis of a small number of samples of palm-kernels, ground-nut cake and peanut butter. It is proposed that the test, which has the potential to discriminate between acceptable and unacceptable batches, be adopted for commodities which are difficult to sample or process.
Journal of Microbiological Methods, 1999
A novel colorimetric microbial bioassay for toxicity has been developed; it shows particular sens... more A novel colorimetric microbial bioassay for toxicity has been developed; it shows particular sensitivity to trichothecene mycotoxins. The assay uses inhibition of expression of b-galactosidase activity within the yeast Kluyveromyces marxianus as a sensitive toxicity indicator, cultures remaining yellow, rather than turning deep green-blue, in the presence of X-gal, a chromogenic substrate. The assay is conducted in standard microtitre plates, permitting small volumes (160 ml) and many replicates, and can be scored either automatically by a plate-reader, or by eye. Factors likely to affect the efficacy of the bioassay, including carbon source, solvents, inoculum cell density, and the use of membrane-modulating agents (MMAs), were assessed. Polymyxin B nonapeptide was the most effective toxicity-enhancing MMA tested, enabling the trichothecene mycotoxin, verrucarin A, to be detected at a concentration of about 1 ng / ml. The assay's reproducibility was examined using polymyxin B sulfate, a cheaper MMA, and another trichothecene mycotoxin, T2 toxin: reproducibility and sensitivity were better for the b-galactosidase X-gal endpoint than for an alternative chromogenic toxicity indicator, the respiratory substrate 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT).
Journal of Microbiological Methods, 2009
A novel aflatoxin B(1) bioassay was created by introducing a Lipomyces kononenkoae alpha-amylase ... more A novel aflatoxin B(1) bioassay was created by introducing a Lipomyces kononenkoae alpha-amylase gene into a strain of S. cerevisiae capable of expressing the human cytochrome P450 3A4 (CYP3A4), and the cognate human CYP450 reductase. This strain and a dextranase-expressing strain were used in the development of a microtitre plate mycotoxin bioassay, which employed methanol as the solvent and polymyxin B nonapeptide as a permeation enhancer. Stable co-expression of the CYP3A4 gene system and of the dextranase and amylase genes in the two bioassay strains was demonstrated. The bioassay signalled toxicity as inhibition of secreted carbohydrase activity, using sensitive fluorimetric assays. The amylase-expressing strain could detect aflatoxin B(1) at 2 ng/ml, and was more sensitive than the dextranase-expressing strain. Aflatoxin G(1) could be detected at 2 microg/ml, and the trichothecene mycotoxin T-2 toxin was detectable at 100 ng/ml.
Journal of Food Quality, 2000
ABSTRACT One of the main objectives of artisanal rice parboiling is to reduce the levels of broke... more ABSTRACT One of the main objectives of artisanal rice parboiling is to reduce the levels of broken grains (brokens) on milling. Rice samples that had been parboiled using different regimes of soaking temperatures and steaming times were analyzed for their physical properties and cooked rice textures. It was established that inappropriate soaking and steaming regimes resulted in greater levels of brokens than raw-milled paddy. Consequently, in artisanal parboiling, the initial soaking temperature should be about 90C and the steaming time should be more than 8 min, ideally, about 12 min. On cooking, more severely parboiled rice samples had firmer textures than mildly parboiled samples. The commercially parboiled sample and the more severely laboratory-parboiled samples required a rice-to-water ratio of 1:3, while the raw-milled sample and the mildly parboiled ones required a 1:2½ rice-to-water ratio for optimum cooking.PRACTICAL APPLICATIONSArtisanal rice parboiling is carried out mainly to reduce the levels of broken grains and increase the yield of milled rice in many countries. If this is carried out very well, there are economic benefits as more rice of better quality is available to be sold. This study provides information on optimum processing conditions, i.e., initial soaking temperature of about 90C and a steaming time of about 12 min. The study also provides recommendations on optimum cooking conditions, i.e., rice-to-water ratio, for the variably parboiled rice samples.
Journal of Chromatography A, 2010
Two polymers were computationally designed with affinity to two of the most abundant mycotoxins a... more Two polymers were computationally designed with affinity to two of the most abundant mycotoxins aflatoxin B1 (AFB1) and ochratoxin A (OTA) for application in the ToxiQuant T1 System. The principle of quantification of AFB1 and OTA using the ToxiQuant T1 instrument comprised of a fluorimetric analysis of mycotoxins adsorbed on the polymer upon exposure to UV light. High affinity of the developed resins allowed the adsorption of both toxins as discrete bands on the top of the cartridge with detection limit as low as 1 ng quantity of mycotoxins.
Food Chemistry, 1995
The efficiency of two different immunoaffinity columns and a phenyl bondedphase column were compa... more The efficiency of two different immunoaffinity columns and a phenyl bondedphase column were compared during the extraction, clean-up and quantification of aflatoxin Bl from sorghum and maize. Fluorodensitometry of high performance thin-layer chromatograms was used for quantification of aflatoxin B,. Maize had a simple matrix, and comparable precisions and accuracies were obtained for each of the methods. The sorghum matrix was complex and the bonded-phase procedure was the most accurate and precise method. There was evidence to suggest that the lower aflatoxin B, recovery from sorghum by immunoaffinity columns is a solvent extraction problem. Better aflatoxin B, recoveries were obtained from naturally contaminated sorghum and maize when acetonitrile was replaced with acetone as the extraction solvent.
Food Chemistry, 1995
A solid-phase clean-up method for the determination of aflatoxins in groundnut cake has been stat... more A solid-phase clean-up method for the determination of aflatoxins in groundnut cake has been statistically examined. The method involves the clean-up of an acetone and water (85 + 15) extract on a bonded-phase (PH) cartridge and quantification by HPLC with fluorescence detection following post-column derivatisation with iodine. Average recoveries were calculated as 84.1, 86.1, 88.0 and 82.1% with limits of detection of 2.7, 1.6, 2.5 and 3.2 &kg for aflatoxins B,, B,, G, and G2 respectively. This method was compared with the official AOAC (CB) method for its ability to determine the aflatoxin B, and B2 contents of groundnut cake samples. The precision of the two methods was found not to be significantly different at the 5% level, but the PH method recorded significantly more aflatoxin B,. The direct extraction of aflatoxins with aqueous acetone was also compared with a slurry extraction method. It was demonstrated that the slurry technique extracted significantly more aflatoxins B, and B,; the precision of these two extraction methods was found not to differ significantly.
A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and... more A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and feeds grown in Bangladesh. The study also included groundnuts utilized as snack food. In the first two phases of the program the samples collected were analyzed only for aflatoxins, but in the third phase, as well as for aflatoxins, samples were tested for the presence of fumonisin B1, ochratoxin A, zearalenone, deoxynivalenol, and T-2 toxin. Of the foods and feeds tested, the incidence of aflatoxin contamination varied from low (rice collected from farmers' stores, 8%) to high (maize, 67%). However, both the average total aflatoxin contents (< 1.0 microg/kg) and the maximum aflatoxin B1 contents (< or = 5.0 microg/kg) recorded for pulses, rice and its various products, and wheat were low. On the other hand, the levels of contamination of maize, roasted and raw groundnuts, and poultry feed were considerably higher, with average total aflatoxin B1 contents of 33, 13, 65, and 7 ...
Medical laboratory sciences
The presence of mycotoxins in a wide range of foodstuffs can lead to many different toxic conditi... more The presence of mycotoxins in a wide range of foodstuffs can lead to many different toxic conditions in both man and domestic animals. The major fungi responsible for producing these toxins are species of Aspergillus, Penicillium, Fusarium and Alternaria, although other genera are involved as well, for example Claviceps, Diplodia and Arthrinium. An overview is given of the major mycotoxins responsible for illnesses following ingestion of contaminated foods, with particular emphasis on the effects produced in humans. Compounds discussed include the aflatoxins, cyclopiazonic acid, tenuazonic acid, the trichothecenes, zearalenone, wortmannin, fumonisins B1 and B2, patulin, ochratoxin A, diplodiatoxin and diplosporin.
British journal of biomedical science
A comparison has been made between pre-column and post-column derivatisation of aflatoxin B1 (AFB... more A comparison has been made between pre-column and post-column derivatisation of aflatoxin B1 (AFB1) during estimation by high-performance liquid chromatography of this toxin in groundnut meal. The effect of the use of different derivatisation reagents on the quantification of aflatoxin B2 (AFB2) has also been evaluated. Both AFB1 and AFB2 were analysed at eight levels of artificial contamination. Five replicate analyses were carried out at each level on both groundnut meal extract (acetone-water, 85:15, v/v) and extraction solvent alone. A statistical evaluation of the results gave limits of detection of 1.1 and 0.3 micrograms/kg for AFB1 and AFB2 respectively, using pre-column derivatisation compared with 1.5 and 0.8 micrograms/kg for the post-column method. Recoveries of over 90% from the spiked groundnut meal extracts were achieved for both derivatisation methods.
Applied and environmental microbiology, 1999
We tested a novel colorimetric toxicity test, based on inhibition of beta-galactosidase activity ... more We tested a novel colorimetric toxicity test, based on inhibition of beta-galactosidase activity in the yeast Kluyveromyces marxianus, for sensitivity to a range of mycotoxins. A variety of trichothecene mycotoxins could be detected. The order of toxicity established with this bioassay was verrucarin A > roridin A > T-2 toxin > diacetoxyscirpenol > HT-2 toxin > acetyl T-2 toxin > neosolaniol > fusarenon X > T-2 triol > scirpentriol > nivalenol > deoxynivalenol > T-2 tetraol. The sensitivity of detection was high, with the most potent trichothecene tested, verrucarin A, having a 50% effective concentration (concentration of toxin causing 50% inhibition) of 2 ng/ml. Other mycotoxins (cyclopiazonic acid, fumonisin B1, ochratoxin A, patulin, sterigmatocystin, tenuazonic acid, and zearalenone) could not be detected at up to 10 micrograms/ml, nor could aflatoxins B1 and M1 be detected at concentrations up to 25 micrograms/ml. This test should be useful ...
Society for Applied Bacteriology symposium series, 1989
1. Introduction, 105s 2. Sampling problems, 106s 2.1 Sampling plans, 108s 3. Errors arising durin... more 1. Introduction, 105s 2. Sampling problems, 106s 2.1 Sampling plans, 108s 3. Errors arising during sample preparation, 109s 4. Analytical procedures, 11 1s 5. Statistical models for sampling plans, 111s 6. Conclusions, 115s 7. References, 115s 106s K. Jewers et al.
Journal of natural toxins, 2002
A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and... more A three-year surveillance program assessed the extent of mycotoxin contamination of key foods and feeds grown in Bangladesh. The study also included groundnuts utilized as snack food. In the first two phases of the program the samples collected were analyzed only for aflatoxins, but in the third phase, as well as for aflatoxins, samples were tested for the presence of fumonisin B1, ochratoxin A, zearalenone, deoxynivalenol, and T-2 toxin. Of the foods and feeds tested, the incidence of aflatoxin contamination varied from low (rice collected from farmers' stores, 8%) to high (maize, 67%). However, both the average total aflatoxin contents (< 1.0 microg/kg) and the maximum aflatoxin B1 contents (< or = 5.0 microg/kg) recorded for pulses, rice and its various products, and wheat were low. On the other hand, the levels of contamination of maize, roasted and raw groundnuts, and poultry feed were considerably higher, with average total aflatoxin B1 contents of 33, 13, 65, and 7 ...
Biotechnology letters, 2000
Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscop... more Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscopy showed no evidence of cytochrome P450, in contrast to microsomes isolated from a control strain of Saccharomyces cerevisiae. Benzo[a]pyrene produced a typical Type I-binding spectrum with microsomes of both yeasts, with K s values of 82 µM (S. cerevisiae) and 70 µM (K. marxianus). While aflatoxin B 1 generated a typical Type I-binding spectrum with microsomes from S. cerevisiae (K s of 178 µM), the toxin did not produce a recognisable binding spectrum with microsomes from K. marxianus.
The Analyst, 1992
A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2,... more A rapid, simple and reproducible method for the simultaneous estimation of aflatoxins AFB1, AFB2, AFG1 and AFG2 in palm kernel samples has been developed by optimizing the sample preparation, solvent extraction, sample clean-up and quantification procedures. The aflatoxins are extracted from a slurried palm kernel sample with an acetone-water (80 + 20, v/v) mixture and the crude extract is cleaned up by solid-phase extraction using a phenyl bonded phase cartridge. The extract is passed through the cartridge with a water-methanol (93 + 7) mixture. Subsequent elution of the aflatoxins retained on the cartridge is achieved with a 3 ml aliquot of chloroform. The aflatoxin content of the eluate is quantified using a bi-directional high-performance thin-layer chromatography procedure. A critical evaluation of the proposed method was carried out by statistical comparison with the British Standard Method. The proposed procedure was shown to be more efficient and precise. Consistent recoveries of over 90% were achieved from spiked palm kernel extracts and detection limits were found to be 3.7, 2.5, 3.0 and 1.3 micrograms kg-1 for AFB1, AFB2, AFG1 and AFG2 aflatoxins, respectively.
Phytochemistry, 1994
ABSTRACT From a 1960s sample of groundnut cake, which had been implicated in the first record of ... more ABSTRACT From a 1960s sample of groundnut cake, which had been implicated in the first record of turkey ‘X’ disease, cyclopiazonic acid has been detected at a level of 31 μg kg−1. The presence of this mycotoxin, along with aflatoxins, explains the toxic symptoms originally recorded after the groundnut cake had been ingested by turkeys.
Magnetic Resonance in Chemistry, 1988
The Statistician, 1994
ABSTRACT Aflatoxins are suspected human carcinogens and levels of contamination are subject to le... more ABSTRACT Aflatoxins are suspected human carcinogens and levels of contamination are subject to legislation. A case-study is presented which examines the application of a sequential acceptance test. The test is based on the analysis of a small number of samples of palm-kernels, ground-nut cake and peanut butter. It is proposed that the test, which has the potential to discriminate between acceptable and unacceptable batches, be adopted for commodities which are difficult to sample or process.
Journal of Microbiological Methods, 1999
A novel colorimetric microbial bioassay for toxicity has been developed; it shows particular sens... more A novel colorimetric microbial bioassay for toxicity has been developed; it shows particular sensitivity to trichothecene mycotoxins. The assay uses inhibition of expression of b-galactosidase activity within the yeast Kluyveromyces marxianus as a sensitive toxicity indicator, cultures remaining yellow, rather than turning deep green-blue, in the presence of X-gal, a chromogenic substrate. The assay is conducted in standard microtitre plates, permitting small volumes (160 ml) and many replicates, and can be scored either automatically by a plate-reader, or by eye. Factors likely to affect the efficacy of the bioassay, including carbon source, solvents, inoculum cell density, and the use of membrane-modulating agents (MMAs), were assessed. Polymyxin B nonapeptide was the most effective toxicity-enhancing MMA tested, enabling the trichothecene mycotoxin, verrucarin A, to be detected at a concentration of about 1 ng / ml. The assay's reproducibility was examined using polymyxin B sulfate, a cheaper MMA, and another trichothecene mycotoxin, T2 toxin: reproducibility and sensitivity were better for the b-galactosidase X-gal endpoint than for an alternative chromogenic toxicity indicator, the respiratory substrate 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT).
Journal of Microbiological Methods, 2009
A novel aflatoxin B(1) bioassay was created by introducing a Lipomyces kononenkoae alpha-amylase ... more A novel aflatoxin B(1) bioassay was created by introducing a Lipomyces kononenkoae alpha-amylase gene into a strain of S. cerevisiae capable of expressing the human cytochrome P450 3A4 (CYP3A4), and the cognate human CYP450 reductase. This strain and a dextranase-expressing strain were used in the development of a microtitre plate mycotoxin bioassay, which employed methanol as the solvent and polymyxin B nonapeptide as a permeation enhancer. Stable co-expression of the CYP3A4 gene system and of the dextranase and amylase genes in the two bioassay strains was demonstrated. The bioassay signalled toxicity as inhibition of secreted carbohydrase activity, using sensitive fluorimetric assays. The amylase-expressing strain could detect aflatoxin B(1) at 2 ng/ml, and was more sensitive than the dextranase-expressing strain. Aflatoxin G(1) could be detected at 2 microg/ml, and the trichothecene mycotoxin T-2 toxin was detectable at 100 ng/ml.
Journal of Food Quality, 2000
ABSTRACT One of the main objectives of artisanal rice parboiling is to reduce the levels of broke... more ABSTRACT One of the main objectives of artisanal rice parboiling is to reduce the levels of broken grains (brokens) on milling. Rice samples that had been parboiled using different regimes of soaking temperatures and steaming times were analyzed for their physical properties and cooked rice textures. It was established that inappropriate soaking and steaming regimes resulted in greater levels of brokens than raw-milled paddy. Consequently, in artisanal parboiling, the initial soaking temperature should be about 90C and the steaming time should be more than 8 min, ideally, about 12 min. On cooking, more severely parboiled rice samples had firmer textures than mildly parboiled samples. The commercially parboiled sample and the more severely laboratory-parboiled samples required a rice-to-water ratio of 1:3, while the raw-milled sample and the mildly parboiled ones required a 1:2½ rice-to-water ratio for optimum cooking.PRACTICAL APPLICATIONSArtisanal rice parboiling is carried out mainly to reduce the levels of broken grains and increase the yield of milled rice in many countries. If this is carried out very well, there are economic benefits as more rice of better quality is available to be sold. This study provides information on optimum processing conditions, i.e., initial soaking temperature of about 90C and a steaming time of about 12 min. The study also provides recommendations on optimum cooking conditions, i.e., rice-to-water ratio, for the variably parboiled rice samples.
Journal of Chromatography A, 2010
Two polymers were computationally designed with affinity to two of the most abundant mycotoxins a... more Two polymers were computationally designed with affinity to two of the most abundant mycotoxins aflatoxin B1 (AFB1) and ochratoxin A (OTA) for application in the ToxiQuant T1 System. The principle of quantification of AFB1 and OTA using the ToxiQuant T1 instrument comprised of a fluorimetric analysis of mycotoxins adsorbed on the polymer upon exposure to UV light. High affinity of the developed resins allowed the adsorption of both toxins as discrete bands on the top of the cartridge with detection limit as low as 1 ng quantity of mycotoxins.
Food Chemistry, 1995
The efficiency of two different immunoaffinity columns and a phenyl bondedphase column were compa... more The efficiency of two different immunoaffinity columns and a phenyl bondedphase column were compared during the extraction, clean-up and quantification of aflatoxin Bl from sorghum and maize. Fluorodensitometry of high performance thin-layer chromatograms was used for quantification of aflatoxin B,. Maize had a simple matrix, and comparable precisions and accuracies were obtained for each of the methods. The sorghum matrix was complex and the bonded-phase procedure was the most accurate and precise method. There was evidence to suggest that the lower aflatoxin B, recovery from sorghum by immunoaffinity columns is a solvent extraction problem. Better aflatoxin B, recoveries were obtained from naturally contaminated sorghum and maize when acetonitrile was replaced with acetone as the extraction solvent.
Food Chemistry, 1995
A solid-phase clean-up method for the determination of aflatoxins in groundnut cake has been stat... more A solid-phase clean-up method for the determination of aflatoxins in groundnut cake has been statistically examined. The method involves the clean-up of an acetone and water (85 + 15) extract on a bonded-phase (PH) cartridge and quantification by HPLC with fluorescence detection following post-column derivatisation with iodine. Average recoveries were calculated as 84.1, 86.1, 88.0 and 82.1% with limits of detection of 2.7, 1.6, 2.5 and 3.2 &kg for aflatoxins B,, B,, G, and G2 respectively. This method was compared with the official AOAC (CB) method for its ability to determine the aflatoxin B, and B2 contents of groundnut cake samples. The precision of the two methods was found not to be significantly different at the 5% level, but the PH method recorded significantly more aflatoxin B,. The direct extraction of aflatoxins with aqueous acetone was also compared with a slurry extraction method. It was demonstrated that the slurry technique extracted significantly more aflatoxins B, and B,; the precision of these two extraction methods was found not to differ significantly.