Fate of Fusarium mycotoxins during food production. Cases of beer and cereal-based infant food.

Mycotoxins are secondary metabolites of a high concern for the food and feed industry. Their transfer from raw materials to the final product was often studied and demonstrated among the recent years. The present work is designed to investigate the fate of Fusarium mycotoxins throughout the production process of two food products with specific consumption characteristics: beer, the most consumed alcoholic beverage worldwide, and cereal-based baby food, which represents the main energy source at the very early stage of
human life.

For practical reasons, experimental designs were built for several specific stages of both production processes, focusing on the stages that had been previously reported as able or possibly able of mitigating mycotoxin contamination. Thus, malting, mashing, boiling and alcoholic fermentation were selected for beer making technology; and flour roasting, followed by the pre-gelatinization and enzymatic digestion were chosen for the baby-food production process. All the processes were reproduced at laboratory scale production and samples were taken. Various sample preparation and analytical techniques for Fusarium
toxins were chosen to achieve the proposed objectives. Sample preparation was mostly performed by immunoaffinity columns and QuEChERS with or without a clean-up. The detection of the mycotoxins was achieved by HPLC coupled to either fluorescence, diode array or triple quadrupole mass spectrometer detectors.

The study of the mycotoxins in beer started by identifying the occurrence of multiple mycotoxins in commercially available beers from Lleida (64 different beers) and Veracruz (61 beers), additionally estimating the possible deoxynivalenol exposure scenarios related to beer consumption in the respective geographical areas. The results showed a total of 20.3 and 26.2% of contaminated samples in Lleida and Veracruz, respectively. Some of the samples were co-contaminated with two or more mycotoxins produced by different Fusarium species.

DON, ZEN and DON-3-Glc changes were studied during malting. Barley batches contaminated in two different ways and at different mycotoxin levels were used for malting. The study of the effect of mashing and boiling similarly involved various contamination sources and levels of mycotoxins, and also included other analytes such as fumonisins and the modified forms of DON and ZEN. The results identified a reduction of DON levels during steeping and its glycosylation during germination. ZEN was unchanged during steeping, but a peaked after 48h of germination. Kilning did not lead to any significant change in the levels of the studied mycotoxins.

The high solubility in water allowed the transfer of DON, DON-3-Glc and FBs from malt to wort during mashing, the first stage of mashing (15 min at 45ºC) being the most significant. ZEN also was partly transferred, but more gradually, probably due to the high temperature and relatively long time of contact with water. Boiling led to a significant reduction in all studied mycotoxins after the first 30 min of the treatment. Although almost 99% of ZEN was reduced, final DON concentration represented 30 to 60% of the level
initially contained in the contaminated malt.

Fifteen different Saccharomyces species were studied for their ability to adsorb DON and ZEN. Malt contaminated with a Fusarium graminearum strain was used for the study. The results showed that 11 to 17% for DON and up to 72% of ZEN were adsorbed by the yeast cell wall. The presence of mycotoxins did not affect alcohol production during the process.

Three different cereal flours were used to study the effect of cereal-based baby food production process on mycotoxin contamination, namely barley, wheat and oat. The roasting was performed by choosing two temperature levels (105ºC and 120ºC) and two treatment times (30 and 40 min). The study did not show a significant change in the initial level of the mycotoxins, similar to the data already reported in the literature.
For the enzymatic treatment two different doses of a-amylase and glucoamylase were chosen, with three different incubation times. The results showed different enzymatic activity levels for the different flours, probably explained by the different structure and composition for each cereal. No significant changes in the mycotoxin levels was identified, however a slight increasing trend in ZEN and its modified forms was found. Also, no relationship of transformation of the parental forms into modified mycotoxins could be proven. Thus, the present thesis proves a partial or complete reduction of Fusarium mycotoxins during beer production process at different stages of it. Nonetheless, no significant changes in the mycotoxin levels were registered in the case of infant food.

Full-text available at: https://www.tdx.cat/handle/10803/669276