Mycotoxins and Your Meal 2

2. Ochratoxin A

Ochratoxins are a group of chemically related mycotoxins commonly found in diverse food items like grains, coffee, cocoa, tubers, dried fruits, wine, beer and animal based meals meals As mycotoxins they are poisons produced by moulds on food, particularly in unhygienic regime. Ochratoxin A or OTA is the most important and toxic member of the family. OTA was first, in 1965 isolated from Aspergillus ochraceus, a fungus. However, as a result of contemporary advances in molecular studies, this fungus from which OTA was originally isolated was later identified as Aspergillus westerdjikiae. That was in the year 2004. Another fungal species known to produce OTA is Penicillium. The importance of this mycotoxin lies in its impact on health and export. And like most mycotoxins, OTA is associated with climatic and economic challenge. Exposure to dietary OTA in animal may result in ochratoxicosis, expressing as cancer of the kidney. In fact it has been classified as group 2B carcinogen by the International Agency for Research on Cancer IARC , meaning that it is a possible carcinogen for humans .The IARC is an arm of the WHO.

The FAO/Who publication of 2001 revealed that the Joint Expert Committee on Food Additives (JECFA) established a provisional tolerable weekly intake (PTWI) of 100 ng/kg body weight based on the lower amount of the toxin that caused adverse effects to swine kidneys . J L Schaler has reported that male and female Fischer rats given oral doses of OTA had dose- related increase in kidney tumors: renal-cell adenomas, and renal-cell adeno-carcinomas. With metastasis of the renal cell tumors. It also has an adverse effect on the the body weight, feed intake, and feed conversion in broiler chicken

Humans: Balkan endemic neuropathy (BEN) associated with OTA occurs in countries like Bulgaria, Croatia, Turkey, Egypt, and Yugoslavia where OTA is relatively high in the diet. Individuals with BEN were surveyed for the presence of urinary tract tumors. The incidence of tumors in the urinary system was elevated in both men and women. The poison damages the foetus and the DNA The major source of OTA in the diet in Europe are cereals and wine. Coffee was thought to be important in this respect, but is now considered less significant. Researchers in a few Nigerian Universities and at the Cocoa Research Institute of Nigeria have worked on the incidence of ochratoxin on coffee

Like all mycotoxins, setting of standard that are allowable in meals is based on toxicological, occurrence, distribution and epidemiological data . Some European countries have set limits ranging from 2-10 microgram per kilogram in cereals ,roasted coffee, wine and grape juice. Although Nigeria now adopts EU standards for available regulated mycotoxins, enforcement on OTA limits in food and feed are fairly lax . The Standards Organization of Nigeria is saddled with setting and monitoring standards . However this mandate is expected to be carried out in complimentary ways with the efforts of the NAFDAC, Nigerian Agricultural Quarantine Service, Nigerian Export Promotion Council, and Consumer Protection Council. On the global scale, the World Trade Organisation (WTO) Agreements on Sanitary and Phytosanitary Measures (SPS) and Technical Barriers to Trade (TBT), promote greater harmonization and transparency in the establishment of food regulations that protect the consumer and facilitate trade.

It is relatively heat stable and so can survive cooking processes. Processing like roasting and baking may lead to a slight reduction in levels. On the field, ensuring that crops are harvested at a safe moisture level is a sure preventive measure. Safe moisture prevents mould growth and so OTA production. Rapid and effective drying, ruling out insect invasion and avoidance of damage resulting in wounds as well as physical separation are also effective postharvest strategies

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Dele Fapohunda


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