Mycotoxins in cereal based food products of wheat and oats - effect of processing on free and masked mycotoxins and human risk assessment.

The primary objective of MycoProcess is to ensure production of quality cereal products in Norway with respect to mycotoxin contamination; to ensure that cereal food products are safe to eat, and strive towards a greater part of Norwegian cereals to be used in food production. The cereal of particular interest in the project oat and the food products thereof. An LC-MS/MS method for the simultaneous determination of free and conjugated Fusarium mycotoxins in cereals and cereal-based products has been development and validated (multi-tox method), and has been published in World Mycotoxin Journal. The present method achieves good separation and acceptable sensitivity for the detection of 28 of the most relevant mycotoxins and metabolites. One major focus in the project is the relationship between deoxynivalenol (DON) and its "masked" glucoside, DON-3-glucoside (DON-3G), and both are included in the method. Using the multi-tox method we have in the project tested various cereal processing regimes relevant to the food industry. The impact of dehulling and sequential pearling on the mycotoxin contamination in oats was one process tested. In general, significant reduction in mycotoxin content was achieved through the processing steps. However, we noticed that a greater part of the "masked" mycotoxins, i.e. DON-3G and HT-2-3G, remained in the kernel after dehulling. This is similar to what has been shown in wheat and highlights the potential food safety concerns associated with masked mycotoxins and the bran fractions of cereals, commonly encouraged in the diet because of the high amount of fibers such as beta-glucans. These data are included in the same article as the multi-tox method (Ivanova et al., World Mycotoxin Journal 2016). Another study aimed to assess the effect of flaking and porridge cooking on the mycotoxin levels. DON contaminated oat was taken sequentially through softening regimes, flaking, and cooking, and levels of DON, DON-3G and 3-ADON were determined. Both softening regimes (steaming and conditioning) reduced all three mycotoxins considerably, but steaming was the most efficient for reduction of DON and DON-3G. Conditioning was most efficient for reduction of 3-ADON. Furthermore, flakes of two thicknesses were cooked to produce porridge. Regardless of softening regime, we found a general tendency that thin flakes released more free DON upon porridge cooking than thick flakes, but cooking in itself did not lead to further reduction in the mycotoxin levels. We have also studied mycotoxin levels of DON, DON-3G and 3-ADON through the processes of baking with yeast and sourdough. We found that baking with dry or fresh yeast did not alter the content and composition of DON and its modified forms in the final product. In contrast, baking of sourdough showed that starter culture L73 contributed to a significant increase in DON (~50%) and a reduction in DON-3G. The effect of starter culture was most pronounced when flour had been heat treated. Sequencing of 16S ribosomal DNA revealed that starter culture L73 contains Lactobacillus plantarum, previously shown to hydrolyse DON-3G to DON. Hence, choice of starter culture can greatly affect the mycotoxin levels during fermentation. The last part of the project studies how the mycotoxins behave in the intestinal tract and to what extent they are accessible for uptake through the gut epithelia (bioaccessibility). We used a standardized in vitro digestive model simulating mouth-stomach-small intestine, and DON, DON-3-G and 3-ADON were measured in oat products (yeast and sourdough bread, flake porridge and flour porridge) before and after digestion (in the digestive fluid). Our major finding was that amount of mycotoxin available for absorption does not necessarily correlates with amount of mycotoxin level in the food. We have indications of a negative correlation, however have still to perform some control tests in order to understand this completely. Nevertheless, bioaccessibility seems to be determined by additional factors such as food matrix (granular size and composition).

The risk assessment made by The Norwegian Scientific Committee for Food on mycotoxins in cereal grains in Norway (2013), concluded that children in Norway exceed the tolerable daily intake for DON by consumption of wheat and oat. The knowledge about the f ate of mycotoxins during cereal processing is limited, especially processing on oat, and also the fate of the masked mycotoxins, which can be hydrolyzed to their toxic precursor in the intestine. The primary objective of the MycoProcess project is to ensu re production of safe and quality cereal products in Norway with respect to mycotoxin contamination. This will be done by investigating how various processing technologies of wheat and oat (small scale) affects the stability and the composition of free an d masked mycotoxins. The mycotoxins will be analyzed by multiplex quantification. Optimized processes will be selected and tested in commercial scale together with the industry, as well as risk assessment of the bioavailability of various forms of mycotox ins using in vitro models of the human digestive tract. The results from the project will be communicated to the industry, to consumers and Norwegian authorities, as well as to the peer-reviewed journals. The most challenging part of the project is that t here is no scientific community in Norway today that studies the effect of cereal processing on mycotoxins. The project wants to build this national platform by merging already existing knowledge in the field of cereal chemistry, technology and human heal th (Nofima) with mycology, mycotoxin chemistry and animal health (Veterinary Institute). The final potential of the project findings is that the industry can identify processes that reduce the levels of mycotoxins, decreasing grain spill and add value to the grain industry. It might provide guidelines for future food policies, assert confidence in Norwegian produced food, and maintain the healthy food label of coarse cereal products.