2.1.4. Acid

Food-grade acids can be used for the degradation of many mycotoxins [62]. These acids affect mycotoxins differently. Ochratoxins are reduced through their conversion to phenylalanine and lactone acid. Aflatoxins could be reduced by an acid-catalyzed addition of water to the vinyl ether double bond of AFB1 and AFG1, and they will be converted to their hemiacetal [58].

The high efficiency of food-grade acids in the reduction of aflatoxins is confirmed when used at a concentration of 9% for 15 min at two moisture levels (10 ± 3% and 16 ± 3%), reaching 99% for citric acid, 99.9% for lactic acid, and 96.07% for propionic acid. The most favorable results are obtained following the use of citric acid because of its efficiency in the reduction of the four aflatoxins (AFB1, AFB2, AFG1, AFG2) without the formation of any hazardous residues or metabolites [57].

The conversion rate of AFB1 to AFB2a by citric acid solution (1 M) reached more than 97% when implemented at room temperature for 96 h. This rate increased to 98% and the process was accelerated so that it could be accomplished in only 20 min when boiling was used [59].

Another study evaluated the effect of citric acid and lactic acid solution on the reduction of DON and its derivatives. This study showed that the 5% solutions of both acids are effective in reducing the DON and its derivative 15Ac-DON but have no or small effect on zearalenone, fumonisins, and culmorin [58]. The organic acid may affect the quality of some products causing discoloration and slight changes in odor and taste [59]. The high cost of organic acids is a challenge for their use in the detoxification of feeds [62].

The instability of ozone may support its safety in being used for the degradation of mycotoxins in food and feed without leaving harmful residues in the treated materials. The results shown from different studies in Table 1 put forward the efficiency of the ozonation and ammoniation. Ammonia was able to achieve higher reduction rates of AF and DON than ozone in different food materials. It is worth noting that ammoniation has not been approved by the FDA and may cause many sensorial quality problems [55], and its effect on aflatoxins may be reversible in an acid medium such as the gastrointestinal tract [54]. Many studies proved the high efficiency of citric acid solution in the reduction of mycotoxins and, especially, aflatoxins, reaching 99% with few detrimental effects on food quality. The limitation of its scalability and its use at the industrial level is related to the high cost of these acids [58].

Nixtamalization is a processing step of maize that can be used as a means to eliminate or reduce the number of mycotoxins [65]. Contradictory results about the effectiveness of the traditional nixtamalization process (TNP) are presented in Table 1. Maureen et al., proposed the high efficiency of this process to reduce AF (up to 90%) [50], while Rodríguez– Aguilar et al., declared that TNP is not efficient in reducing the AF in maize and confirmed the contribution of this process to environmental pollution through the high amount of wastewater generated during its execution [51,52]. A potential solution to this harmful effect on the environment could be attributed to the change in the cooking ingredient [53]. The absence of the ideal chemical treatment for the mitigation of mycotoxins imposed the necessity to find other alternatives to be discussed in the next section.
