by StarmanSkye » Wed Jan 11, 2006 4:19 am
Curious what the heck ochratoxin IS, suspecting it might have a contaminated storage/transport system link or be due to environmental/land-use poisoning, I did a web search and found it's a fungus often caused by improper storage, esp. in such temperate climates found in Canada. Apparently, EU has expressed concerns about closely regulating the importation of human and animal foodstuffs that can be contaminated by the highly toxic variety, Ochratoxin A.<br><br>Anyway, for anybody who always wanted to know about ochratoxin but was afraid to ask (and as a convenience), I've posted the info from 3 websites below.<br><br>Sure glad governmental regulation is working to prevent these kinds of unconscionable crimes for the sake of 'profit'.<br>Starman<br>***<br><br><!--EZCODE AUTOLINK START--><a href="http://www.helica.com/food-safety/ochratoxin/">www.helica.com/food-safety/ochratoxin/</a><!--EZCODE AUTOLINK END--><br>Ochratoxin A<br><br>Ochratoxin A is a toxic metabolite produced by several molds of the Aspergillus flavus and Penicillium genera, including Aspergillus ochraceus. The fungal species has the potential to produce ochratoxin A , a known nephrotoxin and carcinogen. It has been frequently detected in human foods and animal feed, mainly in cereal products, although a range of commodities has been reported to contain the toxin. In humans, exposure to ochratoxin A has been linked with Balken endemic nephropathy (BEN), a chronic kidney disease associated with tumors of the renal system. In animals, impairment of renal function has been reported in swine. In turkeys and chickens symptoms included retarded growth, decreased feed conversion, nephropathy and mortality. Feed refusal has also been observed in turkeys. A decrease in egg production and shell quality was reported in both turkeys and chickens.<br>*<br><!--EZCODE AUTOLINK START--><a href="http://www.oardc.ohio-state.edu/ohiofieldcropdisease/Mycotoxins/mycopageochratoxin.htm">www.oardc.ohio-state.edu/...atoxin.htm</a><!--EZCODE AUTOLINK END--><br>Toxin Characteristics <br><br>This toxin is produced by some species of Penicillium and Aspergillus in cereal grains. Ochratoxin A, affects kidney function. <br><br>Crops and Weather Conditions <br><br>Toxin production occurs over a wide temperature range. Optimal conditions for ochratoxin production are at a temperature range between 68-77° F and a crop moisture content of 16% or above. <br>*<br><!--EZCODE AUTOLINK START--><a href="http://193.132.193.215/eman2/fsheet3.asp">193.132.193.215/eman2/fsheet3.asp</a><!--EZCODE AUTOLINK END--><br>Fact sheet 3<br><br>Ochratoxin A is the most important and most commonly occurring of a structurally related group of compounds, and is often abbreviated to OTA or OA. It is produced by some species of Aspergillus, such as A. ochraceus, mainly in tropical regions and by Penicillium verrucosum, a common storage fungus in temperate areas such as Canada, eastern and north western Europe and parts of South America.<br> <br>Ochratoxin A<br> <br>There are reports of other penicillia and aspergilli producing ochratoxin A, but many of these reports are probably the result of misidentification of the fungi or contamination of cultures. Ochratoxin A consists of a polyketide-derived dihydroiso-coumarin moiety linked through the 12-carboxy group to phenylalanine.<br><br>Ochratoxin B differs in structure only by the absence of the chlorine atom. It can occur naturally but is much less toxic. Other related molecules include ochratoxin C, ochratoxin a and ochratoxin ß.<br><br>Chemical and Physical Properties<br><br>Ochratoxin A is a colourless crystalline compound, exhibiting blue fluorescence under UV light. It crystallises from benzene to give a product melting at 90 ºC containing 1 molecule of benzene. This can be removed under vacuum at 120 ºC to give a substance melting at 168 ºC. It crystallises in a pure form from xylene. The sodium salt is soluble in water. As the acid, it is moderately soluble in polar organic solvents such as chloroform, methanol and acetonitrile and dissolves in dilute aqueous sodium bicarbonate. On acid hydrolysis, it yields phenylalanine and an optically active lactone acid, ochratoxin a . Reaction in methanol + HCl yields the methyl ester, while methylation with diazomethane gives the o-methyl methyl ester. It can be stored in ethanol for at least a year under refrigeration and protected from light.<br><br>Toxicity and Importance <br><br>Ochratoxin A is a potent toxin affecting mainly the kidneys, in which it can cause both acute and chronic lesions, whereas its dechloro derivative, ochratoxin B, is non-toxic. A nephrotoxic effect has been demonstrated in all mammalian species. In acute toxicity studies, LD50 values vary greatly in different species, the dog being especially susceptible. Many feeding trials lasting up to 90 days or more have examined the progressive effects on kidney function and damage through prolonged exposure and led to both sub-acute and sub-chronic effects. <br><br>Ochratoxin A is a potent teratogen in mice, rats, hamsters and chickens, but not apparently in pigs when fed to sows during early pregnancy. Both teratogenic and reproductive effects have been demonstrated. It is known to affect the immune system in a number of mammalian species.<br><br>Ochratoxin A is genotoxic both in vitro and in vivo, but the mechanism of genotoxicity is still unclear. Because human exposure to ochratoxin A has been clearly demonstrated by its detection in blood and breast milk, the presence of ochratoxin A in foodstuffs is clearly undesirable.<br><br>Products Affected and Natural Occurrence <br><br>Ochratoxin A was first reported as a natural contaminant of cereals in a sample of corn. Concentrations found are usually below 50 µg/kg but when products are stored badly much higher concentrations can develop. In temperate regions a significant proportion of cereal samples may be contaminated with very small amounts below 1 µg/kg although a few may contain much higher levels. Many surveys for ochratoxin A in cereals have been carried out but in recent years it has been found in a wide range of other stored products and processed foods including coffee, beer, dried fruit, wine, cocoa and nuts. Information on the worldwide occurrence of ochratoxin has been reviewed and reported in several publications.<br><br>Many experiments have been carried out in laboratory culture to identify the optimum conditions for the formation of ochratoxin A by Aspergillus ochraceus and Penicillium verrucosum. However, under field conditions it is often formed in cereals under conditions marginal for the formation of the fungi and this aspect has only recently been addressed, but is vital for understanding how its formation can be avoided. <br><br>Sampling and Analysis<br><br>As with other moulds and mycotoxins, it is crucial that sampling is carried out in a way that ensures that ochratoxin A in the analytical sample is truly representative of the consignment. Failure to do this may invalidate the subsequent analysis. Analytical methods used are based on TLC, HPLC or ELISA. Extraction with aqueous acetonitrile or methanol, followed by clean-up of the extract solutions using immunoaffinity columns combined with HPLC, provides sensitive and selective results for a wide range of foods and animal feed. Limits of detection below 1 µg/kg can be routinely achieved with analytical precision of ±30% for most foods. Acidified chloroform is also a good extractant but is now less popular with analysts as the use of halogenated solvents is discouraged on environmental and health grounds. Detection by TLC is based on its blue fluorescence under UV radiation but the sensitivity of this technique may not be satisfactory to determine ochratoxin A at the low limits now being demanded by some countries to enforce recent legislation. ELISA methods may be qualitative or semi-quantitative and are probably most suitable for rapid screening purposes. It is important to have assurance that such methods have been thoroughly validated.<br><br>Stability and Persistence <br><br>Ochratoxin A is a moderately stable molecule that will survive most food processing to some extent and may thus occur in consumer products. Processing may involve boiling, baking, roasting or fermentation, and the degree to which it is destroyed will further depend on other parameters such as pH, temperature and the other ingredients present. A number of these processes have been examined in detail although much remains to be done. Literature reports have reviewed its fate during malting and brewing, bread making, the processing of cereals into breakfast cereals, production of coffee products, animal feed production and its carry over into meat products. In biological systems, it will bind to serum albumin. <br><br>Because of its persistence through the food chain, current research is concentrated on its prevention. HACCP-like approaches are being developed for application to a number of commercial processes.<br><br>Legislation and Control <br><br>A review of worldwide regulations for mycotoxins carried out in 1995 showed that few countries had any regulations for ochratoxin A. However, there is continued evidence of human exposure to ochratoxin A. Surveys carried out in several countries have clearly demonstrated its presence in human blood and breast milk. This is consistent with surveillance of food commodities that are confirming that ochratoxin A can occur in a wide range of stored products. Estimates of daily intakes range from 0.7 to 4.7 ng/kg bw derived from analyses of food, and from 0.2 to 2.4 ng/kg bw derived from blood samples. In Europe, about 50% of this intake can be attributed to cereal and cereal products. <br><br>Risk assessments have been carried out in Canada and in Scandinavia, and by JECFA. The presence of ochratoxin A in foodstuffs is clearly undesirable, and the EU has recently proposed statutory maximum limits for ochratoxin A of 5 µg/kg in raw cereal grains including rice and buckwheat, 3 µg/kg for derived cereal products or for cereal grains for direct human consumption, and 10 µg/kg in dried vine fruits. Limits for other products are being considered.<br><br>Understanding the factors leading to formation of ochratoxin A will enable strategies to be introduced to limit its formation and this, together with legislation, should ensure that the consumer is adequately protected.<br> <p></p><i></i>
