Simulation of aflatoxin testing plans for shelled peanuts in the United States and in the export market

The 1987 United States aflatoxin testing plan for shelled peanuts was designed with a final accept level of 25 parts per billion (ppb) total aflatoxin. Some of the importers of U.S. peanuts use aflatoxin testing plans with accept levels lower than 25 ppb. For example, the accept level of a testing plan used in The Netherlands is 5 ppb B1 or 10 ppb total aflatoxin. Whenever export lots are re-tested for aflatoxin by an importing country, some lots accepted in the United States will be rejected by the importing country's aflatoxin testing plan. Computer models were developed to determine the effects of decreasing the final accept level of the U.S. testing plan on the number of lots accepted and rejected in the United States and the number of exported lots accepted and rejected by The Netherlands testing plan. Decreasing the final accept level of the U.S. testing plan from 25 to 5 ppb increased the number of lots rejected in the United States by 371% while reducing the number of exported lots rejected by 51%. For every additional 8.3 lots rejected in the United States, one less export lot will be rejected.     

Visual and semiquantitative spectrophotometric ELISA screening method for aflatoxin B1 in corn and peanut products: follow-up collaborative study

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, The Netherlands, Switzerland, Tunisia, and the United States. Twelve raw and roasted peanut and corn portions containing various concentrations of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on competition between an enzyme-conjugated aflatoxin B1 and (free) aflatoxins in the test sample for aflatoxin-specific antibodies coated onto interior surfaces of microtiter wells. After a wash step to remove all unbound aflatoxins, a substrate added to each well is catalyzed from a colorless to a blue solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the test portion increases. Final determination of aflatoxin concentrations can be made by either visual comparison with standard solutions or spectrophotometric comparisons (at 650 nm) to knowns. Overall correlation was good between ELISA and thin-layer chromatographic results for corn and roasted peanut products, with 93 and 98% correct responses for visual and instrumental determinations, respectively. For instrumental determinations of aflatoxin in corn and roasted peanuts in the less than or equal to 20 ng/g range, the relative standard deviations for repeatability (RSDr) were 14.9 and 41.4%, respectively, and the relative standard deviations for reproducibility (RSDR) were 45.7 and 43.5%, respectively. For instrumental determination of greater than 20 ng/g, the respective RSDr and RSDR values were 19.4 and 52.7% for corn and 23.3 and 23.3% for roasted peanuts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enzyme-linked immunosorbent assay for screening aflatoxin B1 in cottonseed products and mixed feed: collaborative study

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, South Africa, Switzerland, The Netherlands, Tunisia, and the United States. Twenty-eight samples of raw and roasted peanuts, corn, whole cottonseed, cottonseed meal, ammoniated cottonseed meal, and poultry feed containing various quantities of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on conjugation of pure aflatoxin B1 to an enzyme and the competition between this conjugate and (free) aflatoxins in the product for aflatoxin-specific antibodies coated onto microtiter well walls. After a wash step to remove all unbound aflatoxins, a substrate, added to each well, is catalyzed from a colorless to a green solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the product increases. Overall correlation was good between ELISA and thin-layer chromatographic (TLC) results for cottonseed products and mixed feed. Variable results were reported for corn and peanut product samples. Although some positive samples (greater than 15 ng/g) of cottonseed products and mixed feed were reported to contain less than 15 ng/g by visual determination, a review of data for absorbance measurements showed that the contamination level was close to the greater than or equal to 15 ng/g standard and would not have been reported as negative under routine screening.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of aflatoxin in pistachios. 7. Sequential sampling

Sequential sampling for aflatoxin testing in pistachios is evaluated using the aflatoxin distribution and Monte Carlo results previously obtained (J. Agric. Food Chem. 1999, 47, 3771-3775). The sequential protocol is modeled on the current EU test protocol by applying a three-step sampling, using 10, 20, and 30 kg sample averages. An acceptance level of 15 ng/g of total aflatoxin, under consideration for U.S. standards, is applied. Optimization leads to indifference regions of 2-30 ng/g for the first two steps. The resulting OC curve approximates that for a single 50 kg sample. The sequential protocol is applied to the results for a set of 1293 lots of the 1998 crop year, each tested with a single 10 kg sample. Ninety-five percent of the lots would have been accepted on the basis of the single test and 1.5% would have been rejected, whereas 3.5% of the lots would have required retesting.     

Evaluation of a testing program for aflatoxin in corn

A computer model that accounts for sampling and analytical variability was developed to simulate the aflatoxin testing program administered by the North Carolina Department of Agriculture (NCDA) to regulate aflatoxin in corn meal. Monte Carlo solution techniques were employed to account for conditional probabilities that rise from multiple samples being used in the testing program. The NCDA testing program was then evaluated by applying the computer model to a hypothetical group of 1000 corn meal lots with the same distribution of aflatoxin concentrations as was observed among aflatoxin assays made by NCDA on commercial lots of corn meal from 1977 to 1980. The average of the 1000 lots assayed was 17.7 parts per billion (ppb). The model predicted that 79.5% of the lots would be accepted and 20.5% of the lots would be rejected by the NCDA testing program. The accepted and rejected lots contained an average of 5.7 and 64.2 ppb aflatoxin, respectively. The testing program accepted 7.3% of the lots with more than 20 ppb aflatoxin (consumers' risk) and rejected 1.0% of the lots with 20 ppb or less (processors' risk). A correct decision was made 94% of the time.     

Distribution of aflatoxin in pistachios. 6. Seller's and buyer's risk.

The seller's risk-the probability of a set of samples exceeding an agreed upon aflatoxin level when the lot mean does not-and the buyer's risk-the probability of a lot exceeding this level when a set of samples do not-have been computed using a parametrized experimental aflatoxin distribution and Monte Carlo simulation. The calculations are exemplified using the proposed EC standards (three 10 kg samples, 4 ng/g of total aflatoxin, basis kernels only) as well as for samples up to 250 kg and for varied lot aflatoxin levels. It is found that within this sample size range the seller's risk is as high as 42% at 10 kg and increases with increasing sample size to 80% at 250 kg. Only by reducing lot levels to 0.2 ng/g of total aflatoxin, basis kernels, can the risk be brought down to 2.5%, independent of sample size. The buyer's risk is as high as 58% at 10 kg but falls to 11% at 250 kg samples. The implications for both seller and buyer strategies are discussed.     

Revising the role of pH and thermal treatments in aflatoxin content reduction during the tortilla and deep frying processes.

Naturally aflatoxin-contaminated corn (Zea mays L.) was made into tortillas, tortilla chips, and corn chips by the traditional and commercial alkaline cooking processes. The traditional nixtamalization (alkaline-cooking) process involved cooking and steeping the corn, whereas the commercial nixtamalization process only steeps the corn in a hot alkaline solution (initially boiling). A pilot plant that includes the cooker, stone grinder, celorio cutter, and oven was used for the experiments. The traditional process eliminated 51.7, 84.5, and 78.8% of the aflatoxins content in tortilla, tortilla chips, and corn chips, respectively. The commercial process was less effective: it removed 29.5, 71.2, and 71.2 of the aflatoxin in the same products. Intermediate and final products did not reach a high enough pH to allow permanent aflatoxin reduction during thermal processing. The cooking or steeping liquor (nejayote) is the only component of the system with a sufficiently high pH (10.2-10.7) to allow modification and detoxification of aflatoxins present in the corn grain. The importance of removal of tip, pericarp, and germ during nixtamalization for aflatoxin reduction in tortilla is evident.     

Fluorometric measurement of aflatoxin adsorbed on florisil in minicolumns.

Filter fluorometers have been adapted to measure the fluorescence intensity of aflatoxin absorbed on a Florisil layer in minicolumns. The relationship between concentration and intensity is near linear in the aflatoxin range from 10 to 100 ng. Although individual aflatoxin fractions cannot be resolved, since the measure is one of total intensity, fluorometric measurements advance the minicolumn screening procedure to a semiquantitative level. The detection of 1 ng aflatoxin B1 is well within the limits of a filter fluorometer with a photomultiplier detector. A precision, expressed as per cent coefficient of variation, ranging from 1.2 to 4.2%, was obtained for standard B1 columns.     

Collaborative study of a method for chemical confirmation of the identity of aflatoxin.

The chemical method for confirmation of the identity of aflatoxin by derivative formation directly on the TLC plate was studied collaboratively by 8 participants. The results show that aflatoxin B-1 was confirmed in 17 of 17 sample extracts representing 15 mu-g aflatoxin B-1/kg peanut butter, in 13 of 16 extracts representing 5 mu-g/kg, and in none of the 7 aflatoxin-free extracts. Collaborators commented that the method was easily performed and gave good results. The method has been adopted as official first action.     

Comparing the potential effectiveness of conservation planning approaches in central North Carolina, USA

We compared four approaches to conservation site selection to protect forest biodiversity in the Triangle Region of North Carolina, USA. Using biological inventory data and an inventory-based conservation plan as benchmarks, we evaluated the potential effectiveness of a focal species plan and three “simple” plans (large forested patches, close to wetlands and riparian areas, diverse forest types). Effectiveness was measured in three ways: the number of inventory elements captured at least once by the plan (representation), the total number of inventory elements captured (completeness), and the proportion of land in the inventory-based plan included (overlap). We further examined the potential effectiveness of the simple plans by calculating their overlap with land identified by the focal species approach. The simple and focal species plans did not differ markedly in terms of representation, but diverged when completeness and overlap were considered. Although representation rates for all four plans were relatively high, lower rates for completeness and overlap raise concerns about long-term viability. The simple plans did not identify the same lands as the focal species plan, and are thus unlikely to provide appropriate habitat for the focal species. Each approach we tested failed to capture some subset of species and communities, highlighting the importance of explicit conservation targets and consideration of ecological processes. Forced to act quickly and with little data, our findings suggest using initially a set of complementary simple plans, each focused on a different habitat type. This should be considered a stopgap measure, however, while more sophisticated plans are constructed, defining explicit conservation targets and considering ecological processes.     

Rapid, non-destructive selection of peanuts for high aflatoxin content by soaking and tandem mass spectrometry

Peanut lots are subject to aflatoxin levels high enough to cause concern to health agencies and trade channels. A possible solution would be to mechanically sort out high aflatoxin nuts from the process stream. Only highly contaminated nuts would need to be removed. However, there exists at present no sorting mechanism which meets commercial needs of adequate reduction and product preservation. To build such a sorter requires knowledge of the properties that can be used for sorting. The first step in the design is to select on the order of one hundred undamaged contaminated nuts which can be compared with noncontaminated ones. Because contaminated nuts are rare, a very large number of nuts needs to be examined nondestructively. We present a method to rapidly carry out such a selection. The method is based on dipping nuts into extraction fluid and examining the resulting fluid by tandem MS without preliminary cleanup. This method has been applied to examine over 65,000 nuts, yielding approximately 120 nuts, each containing more than 250-43000 ng/g aflatoxin (depending on process stream).     

面向立柱栽培的机器人移栽苗序与路径分析

为有效提高穴盘苗向立柱自动移栽的作业效率,以自主开发的螺旋式栽培立柱及其配套移栽机器人系统为对象,进行了无碰撞最短路径设计,进而对不同取苗-栽植方案的路径长度差异及其影响因素进行了分析。研究表明,面向立柱移栽时,单穴盘对1 m立柱移栽的累计路径长度差异在25%以上。取苗顺序对路径长度具有重要影响,其中"让苗"现象是造成累计路径长度差异的主要因素。立柱栽植顺序对路径长度的影响随立柱高度增加而显著增大,对3 m立柱移栽时16类取苗方案的自上至下植苗平均累计路径长度比自下至上高9.83%。稳定最优方案分别为最近相邻法和近端开始同向逐行或逐列取苗、自下至上栽植方案。研究成果对实现高效的立柱自动移栽具有积极意义。     

Quantitative fluorodensitometric determination and survey of aflatoxins in nutmeg.

A study is presented for the quantitative fluorodensitometric analysis of aflatoxins in spices, in particular nutmeg (Semen myristicae). Samples were extracted with chloroform, followed by silica gel column cleanup according to the AOAC officail first action method, 26.019(a), and by 2-dimensional thin layer chromatography according to the antidiagonal technique. The method includes a confirmatory test for aflatoxins by hemiacetal formation. The concentrations of aflatoxins in samples were determined by measurement of the fluorescent intensities of the separated aflatoxin spots from sample and standards on the same chromato-plate with a reflectance flying-spot sensitometer. With such a technique, a coefficient of variation value of 5.22 plus or minus 1.24% (P = 99%) was calculated for a series of 5 standard B-1 spots and averaged for 13 TLC plates, demonstrating the precision of the chromatographic and densitometric procedures. An average recovery of 108.4 plus or minus 5.8% (P = 95%) was obtained for 11 spiked nutmeg extracts (5.0-20.0 mu-g B-1 added/kg), whereas an average recovery of 92.6 plus or minus 4.9 (P = 95%) was established for 13 spiked nutmeg samples (5.0-20.0 mu-g B-1 added/kg). The coefficient of variation of the complete analytical procedure for ground nutmeg was 8.80%. In a survey on the occurrence of aflatoxins in 40 commercial nutmeg samples (covering 12 different brands) in The Netherlands, aflatoxins were detected in 30 ground samples (32 ground samples analyzed) in concentrations ranging from 1.0 to 23.2 mu-g B-1/kg or 2.7 to 36.5 mu-g B-1 + B-2 + G-1 + G-2/kg, whereas no aflatoxins were present in whole nutmeg kernels (8 samples analyzed). The lowest level of detection was 1.0 mu-g B-1/kg. In addition, 50 commercial spices consisting of 19 different types of commodities other than nutmeg wer assayed for aflatoxins according to the same procedure. No aflatoxins were detected in these samples, with the exception of 1 sample of bay leaf which contained 5.1 mu-g B-1/kg.     

三峡工程三十余年是与非

本文包括“三峡工程问题简述”、“原则问题,一点也不能含糊”和“再谈关于三峡工程的意见”三篇文章。这三篇文章全面系统地阐明了三峡工程问题的争论,党中央和国务院的指示,最后提出了经济效益、航运和泥沙、水库移民、防洪、三门峡和葛洲坝的经验教训、替代方案等六个问题。归纳起来就是一条重要意见:为了解决有关地区九十年代及以后的用电需要,应以若干方案同三峡方案一起比较,选出一个最优方案。     

Effect of Aflatoxin B1 on Dry‐Grind Ethanol Process

Aflatoxins, like all mycotoxins, are toxic fungal metabolites that can have adverse health effects on animals and human beings. Aflatoxins are a major concern for the dry‐grind corn processing industry as it is believed that aflatoxins affect yeast and reduce its efficacy in producing ethanol. In the present study, aflatoxin B1 (100, 200, 350, or 775 ppb) was added to mycotoxin‐free corn and laboratory‐scale fermentations were conducted. No effect of aflatoxin B1 was observed on the fermentation rates or final ethanol concentrations. Mean ethanol concentration in the fermenter was 14.01–14.51% (v/v) at 60 hr for all the treatments. In the dry‐grind ethanol process, 55% of aflatoxin B1 was detected in wet grains and 45% in thin stillage.     

Does recovery planning improve the status of threatened species?

Recovery planning is a key component of government-funded initiatives to address declining populations of threatened species. To date, there has been limited retrospective evaluation on the impact of recovery plans, despite an increasing interest in evaluating recovery planning motivated by demands for greater accountability and a shift away from single-species focused strategies to multi-species, landscape and ecosystem-based plans. In the context of threatened species management in Australia, we aimed to investigate whether listed species with recovery plans are more likely to have improved their status compared to listed species without recovery plans. Since 1999, over 600 draft and approved recovery plans have been developed for more than 850 of 1663 species currently listed threatened species in Australia. We applied a novel econometric matching analysis to reduce biases associated with the non-random selection of species for listing and recovery planning. We found that the presence or absence of a recovery plan did not have a statistically significant effect on whether a species’ status was improving, stable or declining. The result suggests that recovery plans may not be useful in the short term and uncertainty persists about whether or not they make a long term contribution to species recovery. One major contributing factor is the lack of basic accounting of recovery planning efforts. This limits our ability to refute or confirm the impact of recovery planning on species status, and has the potential to reduce public confidence in government expenditures. Better systems for reporting and evaluation are therefore required to promote transparency, improve existing knowledge and facilitate efficient investments in future management actions.     

Reduction of aflatoxins B1 and B2 with sodium borohydride.

Reduction of aflatoxin B1 and aflatoxin B2 with sodium borohydride quantitatively yielded new fluorescent derivatives, designated as aflatoxin RB1 and aflatoxin RB2. Mass spectrometric data showed that RB1 and RB2 were trihydroxy derivatives of B1 and B2, respectively. Nuclear magnetic resonance analysis revealed that new chemical shifts were present in aflatoxins RB1 and RB2 in addition to those of the parent aflatoxins. The new compounds had lower melting points and different ultraviolet and infrared spectra compared to aflatoxins B1 and B2 and the monohydroxy derivative aflatoxicol. They were lses toxic to chick embryos than the parent toxins. Since the reduction yields were quantitative and since the reduction products could be detected at low levels comparable to those for B1 and B2, the reduction reaction could be used as a confirmatory test for both aflatoxins B1 and B2. Preliminary results obtained from gas-liquid chromatography (GLC) analysis of the trimethylsilyl derivatives of aflatoxins RB1 and RB2 indicated that these compounds could furnish the basis for developing an analytical GLC method for aflatoxins B1 and B2.     

A quantitative method for determination of aflatoxin B in roasted corn.

Roasting aflatoxin-contaminated corn will reduce toxin levels. A quantitative analysis for aflatoxin in roasted corn has been developed by modifying a cleanup technique for green coffee extracts approved as official first action by the AOAC. A chloroform extract is partially purified on a Florisil column, and thin layer chromatographic (TLC) plates are developed with methylene chloride-chloroform-isoamyl alcohol-formic acid (81+15+3+1). Recoveries average 101% and the sensitivity limit is 5 ppb aflatoxin B1. A 2-dimensional TLC procedure can also be used to separate the aflatoxins from background interferences.     

Coastal engineering and european wintering wetland birds

A survey of existing studies was conducted of the most important wintering regions for waterfowl in western Europe as part of the preparatory studies for hydraulic engineering projects in the southwestern part of The Netherlands. Fifty-five areas were found in which at least 1% of a fly-way population of a species winters.The study confirms the belief that the area at the southern part of the North Sea plays a major role in the wintering of waterfowl. It also showed that only a very rough indication of the wintering regions could be compiled from data in the literature, because of a lack uniformity in the presentation and evaluation.It is pointed out that the present approach is based too much on separating the establishment of nature reserves from the overall natural potential of a region. The integration of this with the other uses to which people put a particular region provides many more opportunities to protect the waterfowl populations. This method should then be integrated into the decision-making procedures and regional management by policy analysis and control plans.The presentation of bird-count data should be integrated more satisfactorily with preparatory policy work.