Mycotoxinspresence and stability during processing of cereal based food

Abstract

.1. Summary (English) Mycotoxins are toxic secondary metabolites produced by fungi that contaminate various agricultural commodities either before harvest or under post-harvest conditions. The most important producing genera are Aspergillus, Fusarium and Penicillium. Mycotoxins can be present in a wide range of products and their intake is of concern because they can produce a wide range of harmful effects to human and animal. Cereal products represent one of the main sources of exposure to mycotoxins. Several mycotoxins have been identified up to the present, but those of special interest in food and feed safety are: aflatoxins (B1, B2, G1 and G2), fumonisins (Fbs), ochratoxin A (OTA), patulin, trichothecenes (deoxynivalenol and nivalenol), and zearalenone (ZEN). However, unaltered mycotoxins might not be the only threat for health consumers, because they can be present in conjugated forms which cannot be detected in the routinary mycotoxins analysis, but they can become as dangerous as parent mycotoxins. The objectives of this thesis were determine the presence of some mycotoxins in cereal products, study the stability of them during the food process and assess the mycotoxin exposure. To reach these aims different studies have been done. Firstly, cereals and cereal based food commercial samples have been analysed to study the presence of aflatoxins (Afs), deoxynivalenol (DON), nivalenol (NIV), ZEN, OTA and some of them conjugated mycotoxins. Bread making and pasta making processes have been deeply studied and some factors have been evaluated to observe the stability of mycotoxins. Mycotoxins exposure has been assessed through two different methods: 1) the combination of contamination data with consumption data and 2) using biomarkers. All mycotoxin analyses have been conducted using liquid chromatography, by ultraviolet, fluorescence and mass spectrometer detectors were used in different studies. Mass spectrometer detectors were handled when conjugated mycotoxins were searched in the different matrixes. Moreover, some new analytical methods have been developed successfully to improve the detection of mycotoxins. Analysis of cereals and cereal based foods showed that mycotoxins are very prevalent. Trichothecenes have showed the highest presence and also the largest concentrations. Thus, some bran analysed samples had DON levels over the limit set by the European legislation. Although DON and NIV were the most common analysed mycotoxins, the rest of the mycotoxins also showed a worrying high presence. More controls on conjugated mycotoxins should be done, because results showed their common presence in the analysed products and in some cases even the concentration of conjugated mycotoxins was higher than parent mycotoxins. Although mycotoxins are considered extremely stable compounds, food processes can cause changes in mycotoxin concentration. Bread fermentation is a complex step where many factors play a role. OTA concentration does not change in concentration during fermentation. Unlike OTA, DON is highly affected by this step (it may either decrease or increase). Actually its fate depends on several factors: temperature, time, enzyme and sourdough presence. Similar to DON, DON-3-glucoside also depends on the same factors as DON during fermentation. Although OTA is more stable than DON and its conjugates during baking, all of them can be reduced in function of some factors as: time, temperatures, enzyme presence and heat transmission. The DON reduction observed in boiled pasta was caused by DON transfer from pasta to broth due to his high solubility. Kinetics to anticipate the mycotoxins fate at the end of food processes have been built as a useful tool for food industry with a good fit (r > 0.75). Because of the important levels of DON found in cereal bran analysed, exposure assessment of DON through bran consumption was calculated. Therefore, fibre supplements intake can be an important source of DON. Biomarkers of DON and OTA were studied through plasma and urine analysis and the results revealed that the exposure to DON and OTA could be of concern for the Catalonia population. Even, a high exposure to DON could be held throughout the time by the same person, exceeding the tolerable daily intake systematically instead of eventually. 1.2. Resum (Catalan) Les micotoxines són metabòlits secundaris produïts per fongs que poden contaminar diferents productes agrícoles abans o després de la collita. Els gèneres més importants de fongs productors de micotoxines són Aspergillus, Fusarium i Penicillium. Les micotoxines poden estar presents en una gran varietat de productes i la seva ingesta pot ser de gran perillositat perquè produeixen una gran varietat d’afectes perjudicials per la salut dels humans i animals. Els productes a base de cereals representen una de les principals fonts d’exposició a les micotoxines. Varies micotoxines s’han identificat fins a dia d’avui, però aquelles micotoxines amb major interès per la seguretat dels aliments i el pinso són: les aflatoxines (B1, B2, G1 i G2), les fumonisines (Fbs), la ocratoxina A (OTA), la patulina, els tricotecens (deoxinivalenol i nivalenol) i la zearalenona