**5. Harvest and postharvest mitigation measures and management**

Controlling harvest and storage conditions is critical to effectively prevent mold growth and mycotoxin production in wheat postharvest. Harvesting strategies, moisture, water activity (Aw), temperature, storage period, contamination rate, broken grains, insect presence, and oxygen rate are the main critical points to manage in order to mitigate the mycotoxin risks postharvest [48, 50–52, 99].

*Harvest management:* Wheat should be harvested as soon as possible to reduce fungal growth and spread during favorable weather conditions. Management strategies during harvest include wheat harvest at low moisture or Aw, reduced mechanical seed damage, and the use of different grain harvest strategies to remove diseased kernels which are often lighter than the healthy ones. The use different harvesting configurations, with varying fan speeds and shutter openings, resulted in lower *Fusarium*‐damaged wheat kernels and DON content in harvested wheat [99, 100]. The removal of damaged grain implies a loss in the yield of har‐ vested grain, but results in better storage conditions and improvement in grain safety offset‐ ting the economic losses.

*Postharvest management:* Efficient drying and storage of wheat in silos free of insect pests and moldy material are critical points to reduce mycotoxin contamination. Harvested grain must be dried to <14.5% moisture content and at a relative humidity of 70% to avoid mold spoilage or increase of preharvest contamination with mycotoxins [48, 51, 101, 102]. Besides humidity, the temperature during storage is another critical point for fungal growth and activity. During storage, humidity and temperature are strictly related and cause changes in the microclimate conditions favoring or inhibiting fungal growth and colonization and influencing the pat‐ tern of mycotoxin contamination [49, 51, 103]. A comparison of environmental conditions for fungal growth and toxin production by some common fungal species is reported in **Table 2**.


AFLA, aflatoxins; DON, deoxynivalenol; NIV, nivalenol; OTA, ochratoxin A; T‐2, T‐2 toxin; ZEA, zearalenone; Aw, water activity; n.a., not available.

**Table 2.** Comparison of environmental conditions for fungal growth (G) and toxin production (TP) by some common fungal species (modified from Ref. [104]).

In wheat, positive relationships between dry matter losses caused by *F. graminearum* under different environmental conditions (temperature, humidity, Aw) and the level contamination with DON have been reported [49, 51]. Moreover, it has been shown that the pattern and the levels of mycotoxin production in wheat grains by various *Aspergillus* sp. are different in rela‐ tion to different relative humidity values and storage periods [101].

(Aw), temperature, storage period, contamination rate, broken grains, insect presence, and oxygen rate are the main critical points to manage in order to mitigate the mycotoxin risks

*Harvest management:* Wheat should be harvested as soon as possible to reduce fungal growth and spread during favorable weather conditions. Management strategies during harvest include wheat harvest at low moisture or Aw, reduced mechanical seed damage, and the use of different grain harvest strategies to remove diseased kernels which are often lighter than the healthy ones. The use different harvesting configurations, with varying fan speeds and shutter openings, resulted in lower *Fusarium*‐damaged wheat kernels and DON content in harvested wheat [99, 100]. The removal of damaged grain implies a loss in the yield of har‐ vested grain, but results in better storage conditions and improvement in grain safety offset‐

*Postharvest management:* Efficient drying and storage of wheat in silos free of insect pests and moldy material are critical points to reduce mycotoxin contamination. Harvested grain must be dried to <14.5% moisture content and at a relative humidity of 70% to avoid mold spoilage or increase of preharvest contamination with mycotoxins [48, 51, 101, 102]. Besides humidity, the temperature during storage is another critical point for fungal growth and activity. During storage, humidity and temperature are strictly related and cause changes in the microclimate conditions favoring or inhibiting fungal growth and colonization and influencing the pat‐ tern of mycotoxin contamination [49, 51, 103]. A comparison of environmental conditions for fungal growth and toxin production by some common fungal species is reported in **Table 2**.

**T, °C pH Optimal Aw**

Optimum: 3.5–8.0

Optimum: 3.5–8.0

3.0 at 25°C and

Optimum: 6.0–7.0

Range: 3.5–8.0 Optimum: 6.0

Range: 3.5–8.0 Optimum: 6.0

0.84 0.87

0.80 0.82

2.4–3.0 0.90 0.90

n.a. 0.80 0.86

**Species (mycotoxins) G TP G TP G TP**

12–40 Range: 2.1–11.2

12–40 Range: 2.1–11.2

37°C

4–20 Range: 2.0–10.0

AFLA, aflatoxins; DON, deoxynivalenol; NIV, nivalenol; OTA, ochratoxin A; T‐2, T‐2 toxin; ZEA, zearalenone; Aw, water

**Table 2.** Comparison of environmental conditions for fungal growth (G) and toxin production (TP) by some common

24–26 24–26 2.4 at 30°C and

In wheat, positive relationships between dry matter losses caused by *F. graminearum* under different environmental conditions (temperature, humidity, Aw) and the level contamination with DON have been reported [49, 51]. Moreover, it has been shown that the pattern and the

postharvest [48, 50–52, 99].

236 Wheat Improvement, Management and Utilization

ting the economic losses.

*A. parasiticus* (AFLA) Range: 10–43

*A. flavus* (AFLA) Range: 10–43

*P*. *verrucosum* (OTA) Range: 0–31

fungal species (modified from Ref. [104]).

*Fusarium* species (T‐2, DON, NIV, ZEA)

activity; n.a., not available.

Optimum: 32–35

Optimum: 32–35

Optimum: 20

*Use of physical, chemical, and biological decontaminating methods:* Despite efforts to control, miti‐ gate, and reduce fungal and mycotoxin contamination, wheat mycotoxin contamination is unavoidable and unpredictable, and postharvest decontaminating approaches can offer a last resort. Different decontaminating methods can be used to eliminate or reduce mycotoxin con‐ tent in cereals before their entry in the food supply chain (**Table 3**).


**Table 3.** Mycotoxin contamination: main post‐harvest physical, chemical, and biological based decontamination strategies.

Jard et al. [120] underlined that the decontaminating approaches must consider several topics concerning safety issues: they must not generate toxic products, ensure the nutritional value of the food, and should not induce negative modification for food processing.

A wide variety of chemical decontamination processes including oxidation, reduction, ammo‐ nization, alkalization, acidification, and deamination has been reported [48, 121]. These meth‐ ods have some limitations concerning safety issues, efficacy coupled with cost and regulatory implication. The use of chemical methods for the decontamination of cereals that exceed the mycotoxin threshold limits are not allowed in the European Union [122]. In the United States of America, only ammonization is licensed for detoxifying aflatoxins [123, 124]. In addition to chemical methods, natural plant extracts and spices are known to prevent mold growth and mycotoxin production. In recent years, the use of essential oils as natural food preservatives to control mold and mycotoxin contamination is gaining interest [117]. Several essential oils have been found to be effective in controlling growth of several *Fusarium* sp. and produc‐ tion of mycotoxin in stored wheat [125, 126]. However, more studies should be performed to identify the components of essential oils with modulatory activity on the growth and toxin production of *Fusarium* sp.

Currently, many researches have been carried out to evaluate the possible use of biologi‐ cal agents or biological transformations for mycotoxin detoxification, as an alternative to the chemical one. This approach includes fungal, microbial, and enzymatic degradation of myco‐ toxins. Several very recent reviews on this topic can be found in the literature to which the reader is directed for specific insights [84, 118, 119, 127, 128]. Despite the many publications on this topic, this promising approach is still at a research level and far from an immediate outcome and application in practice for mycotoxin detoxification of food at industrial level. More research is needed to fully understand mycotoxin biotransformation mechanisms, to evaluate the toxicity of metabolites and the feasibility of application in wheat industry. All these topics must be considered and evaluated keeping in mind the existing regulatory issues for food safety.

Physical decontamination reducing mycotoxins in wheat can be carried out during industrial processing. For the wheat milling industry, the precise knowledge of the fate of mycotoxins during milling is vital and may provide a sound technical basis to conform to legislation requirements, support risk management and regulatory bodies in order to reduce human and animal exposure to mycotoxins, and reduce the risk of severe adverse market and trade repercussions. Wheat sorting, cleaning, debranning, and milling influence mycotoxin repar‐ titioning in wheat milling fractions entering the food chain. The effects of wheat milling and thermal processes on the fate of mycotoxins have been extensively studied [8, 33, 105–112, 121, 129–133]. Published data confirm that milling reduces mycotoxin concentration in frac‐ tions used for human consumption, but concentrates mycotoxins into fractions commonly used as animal feed. Physical and mechanical processes, such as sorting and cleaning prior to milling, reduce mycotoxin contamination in wheat by removing kernels with extensive mold growth, broken kernels, fine materials, and dust. The results indicate that the effect of pre‐ milling processes and the efficiency of mycotoxin removal are extremely variable. The concen‐ tration of mycotoxins in cleaned wheat ranges from 7 to 63% for DON, from 7 to almost 100% for NIV, and from 7 to 40% for ZEA, of the contamination level in unclean grains [28, 134, 135]. A reduction of 62 and 53% of T‐2 and HT‐2, respectively, has been reported in wheat grains after cleaning [136]. Several factors may be involved in this response, such as the initial con‐ dition of the grains, the type and extent of the contamination, and the type and efficiency of the cleaning process. Debranning before cleaning is used in industrial processing to enhance the milling performance of wheat and the degree of refinement of flour and semolina [137]. Debranning before milling further reduces the level of mycotoxin content in wheat grain. As for the cleaning and sorting procedures, the effect of debranning and the efficiency of myco‐ toxin removal are extremely variable. A reduction of DON in debranned wheat ranging from 15 to 78% has been reported [134, 138–140]. Despite the high variability in removal efficiency of mycotoxin, overall results indicate that the physical processes that are carried out before milling (such as sorting, cleaning, and debranning) are very efficient methods to reduce wheat mycotoxin content before milling. As in cleaning and debranning, in the milling process there is no step that destroys mycotoxins; however, mycotoxin contamination may be redistributed in milling fractions [141–143].

Overall results regarding the efficacy of mycotoxin reduction/repartition wheat industrial processing showed a high variability and sometimes appear conflicting. This is related to the type of mycotoxins, the level and extent of fungal contamination, and a failure to under‐ stand the complexity of the milling technology. The knowledge of mycotoxin repartitioning in wheat milling fractions is largely limited to DON, using different approaches (artificially vs. naturally contaminated wheat; wide range of mycotoxin contamination levels; laboratory; semi‐industrial; and industrial milling), but there is still a lack of data for other mycotoxins. Fewer data are available regarding the distribution of other mycotoxins and modified myco‐ toxins in milling fractions [45, 142–146], but a similar scenario has been found, such as myco‐ toxins concentration in milling fractions intended for animal feed.
