2.2.9. Milling

The milling process is effective in reducing mycotoxins in feeds and foods [68,109]. The weakness of this method lies in the redistribution of mycotoxins in the resulting fractions of milling and their concentration in the products intended for animal feed [67].

Scarpino et al., showed that cleaning maize grains may cause a reduction in the fungal metabolites by 1.2 to 2 times. In this study, the milling process of maize kernel caused an unequal redistribution of the mycotoxins in the different maize fractions and concentrated most mycotoxins in the germ. The highest mycotoxin contents were found in animal feed products, and the healthier products are large flaking grits [93]. A study was conducted using this principle by implementing dry and wet de-germination to maize and showed that the latter was more efficient for decreasing fumonisins in the milled products. Cleaning the kernels reduced FBs by 42%. Furthermore, the tempering degermination process of the uncleaned kernels achieved high reduction rates as compared to the dry degermination, reaching 94% for the largest-sized flaking grits. This process was able to facilitate the separation of the horny endosperm from the fine milling fractions. [94].

By evaluating the results of the different chemical treatments in Table 1 and the results of the different physical treatments in Table 2, we can conclude that chemical treatments are able to achieve the highest degradation rates of different mycotoxins in solid foods and feeds. In contrast, the physical treatments achieve lower degradation rates, but their effects on the quality of treated materials are smaller.

The shadowing or shielding effect is the principal limitation related to the use of photocatalysis and UV-C irradiation in the reduction protocols of mycotoxins in solid food materials. Many studies (Table 2) tried to overcome this limitation by rotating the irradiated peanuts to ensure UV uniformity, but no significant increase in the reduction rates occurred. Photocatalysis achieved higher reduction rates of DON, reaching a total elimination of DON in wheat [76]. CAP is a superficial treatment with low penetration depth. It showed good efficiency in reducing AFT and AFB1 without deterioration in the quality of the treated product. Furthermore, SBD plasma was more effective than DBD plasma since it achieved the complete elimination of AFB1 [77,79]. As working gas, nitrogen achieved the highest reduction rates as compared to oxygen and air when using the DBD system [78]. The pulsed light effectiveness was superficial and showed greater AF reduction rates when applied to rice bran than to rough rice. The AFB reduction rates are defined by the PL intensity and the initial concentration of mycotoxins in the food to be treated [83]. Gamma irradiation showed good effectiveness in reducing mycotoxins in food containing a high amount of water and reducing the fungal load in solid food. Low gamma irradiation doses were able to eliminate fungi and reduce mycotoxin formation in maize, but higher doses were required to reduce the already produced OTA in this material. Mycotoxins were not

completely eliminated in any of the mentioned studies (Table 2) [86–88]. The electron beam showed its efficiency as a disinfectant by the reduction of different microorganisms such as bacteria, yeasts, and molds, but it was not effective in the reduction of OTA in red pepper powder [92]. The milling process resulted in the reduction of mycotoxins in many edible fractions of maize but caused the concentration of these fungal metabolites in the germ, especially in the fractions used as animal feeds [93].
