Processing of cereals destined to human and animal consumption. Effects on mycotoxin contamination.

Mycotoxins are secondary metabolites produced by filamentous fungi that occur in several commodities such as cereals, spices, nuts, fruits,  beverages, etc.  Under suitable conditions of temperature, humidity and oxygen, fungi proliferate with the subsequent mycotoxin production. Mycotoxins may then enter the food chain through direct  consumption  of contaminated  foods  by  humans,  or through  the  use  of contaminated feeds for livestock. Aflatoxins, ochratoxin A (OTA), Fusarium toxins (deoxynivalenol, zearalenone and fumonisins) and patulin are toxicologically the most important toxins. They are toxic to both animals and humans and are considered to be risk factors for cancer by the International Agency for Research of Cancer (IARC).

Preventing their formation is the preferable way to control their presence in feeds and foods. However, this is often not possible and once contamination of commodities has occurred,  different strategies are needed to ensure the safety of food  and feed products.  Food  processing  methods  have  been  previously  reviewed  worldwide according to their potential of lowering mycotoxin levels in processed products. In the present work, extrusion-cooking, dry-milling and ready-to-eat (RTE) breakfast cereal production methods have been investigated.

Extrusion-cooking of rice and barley reduces aflatoxins and OTA levels up to 95 and 86%,  respectively,  depending  on  the  moisture  content of the  raw material,  the residence time and the temperature of the process.  Moreover,  extrusion-cooking coupled to the use of ingredients such as salt and sucrose added into maize meal decreases fumonisin B1 content as much as 92%. On the other hand, dry-milling of rice results in a concentration of aflatoxins in hull and bran fractions, which are redirected to animal feed production, while polished broken grains and polished whole kernels,  obtained  from  the  inner  part  of  the  grain  and  intended  for  human consumption, are found to have remarkably lower levels than initial aflatoxins. RTE breakfast  cereal  production,  where  dry-milling  of  maize,  cooking  and  roasting processes take place, is also found to significantly decrease fumonisin and aflatoxin levels in breakfast cereals.

From all the results obtained in the present study, it can be concluded that the evaluated industrial methods are capable of producing edible foods with significantly lowered mycotoxin contamination in comparison to raw materials. However, special attention should be given to by-products destined to animal feed production, where mycotoxin contamination is increased.