**4. Discussion**

A number of studies have shown that weather directly influences host susceptibility to aflatoxin contamination [15]. The differences in the intensity of aflatoxin contamination between CIAM and PAN could be attributed to the variability in intensity and duration of rainfall, temperature, and relative humidity between the two locations. In general, CIAM had significantly higher aflatoxin contamination levels compared to PAN. This was attributed to higher than normal temperatures (≥30°C) and late season rainfall which created warm, moist conditions suitable for fungal growth, and subsequent higher aflatoxin contamination levels on the kernels. These outcomes are similar to earlier accounts that wetter and more humid conditions tend to aggravate aflatoxin levels as it enhances the growth of *Aspergillus* species and production of aflatoxins in groundnuts compared to drier climatic conditions [16]. In addition, studies have shown that the optimal temperature range for production of aflatoxin is approximately 25–30°C agreeing with the current study [17].

after physiological maturity. Additionally, the study has shown that delayed harvesting resulted into higher aflatoxin contamination levels greater than the FDA/WHO regulatory levels of 20 ppb [21]. The high aflatoxin contamination levels at H3 were as a result of heavy damage of pods by insects especially termites (*Odontotermes badius* and *Odontotermes latericus*) which provided the ready entry of fungi including *Aspergillus* species and consequently aflatoxin contamination. Kombiok et al. [22] reported that insects influence the levels of aflatoxin contamination in commodities such as maize and groundnut by carrying fungal inoculum and causing damage that provide the ready entry of the fungus, and thereby increasing the chances of aflatoxin contamination. Furthermore, insects such as termites cause scarification of pods, which weakens the shells and makes them liable to crack during harvesting leading

Effect of Harvesting Time and Drying Methods on Aflatoxin Contamination in Groundnut in Mozambique

http://dx.doi.org/10.5772/intechopen.77300

35

High aflatoxin contamination levels at H3 could also be attributed to physical damage of pods as a result of digging using hoes. Harvesting groundnut 10 days after physiological maturity coincided with dry weather making it difficult to harvest the groundnuts by hand pulling which led to digging the nuts out of the soil using hand hoes. Similar to the effect of insect damage to pods, physical damage to pods tended to increase with delay in harvesting perhaps due to the dryness of the soil which made pulling and digging out of pods very difficult. As a result, many pods of the groundnut varieties got damaged which favored the entry and invasion of the nuts by *Aspergillus* Section *Flavi* that later produced aflatoxins as a result of respiration. These findings are concurrent with the findings of Hell et al. [18] who indicated that some factors that influence the incidence of fungal infection and subsequent toxin development include invertebrate vectors (insects), grain damage, inoculum load, substrate composition, fungal infection levels, prevalence of toxigenic strains, and microbiological interactions. Moreover, the highest levels of *A. flavus* and *A. parasiticus* infection and aflatoxin contamination are associated with seed damage caused by either insects or physical damage of pods [24].

It has also been observed that delayed harvesting coincided with high relative humidity (≥75%) and higher air/soil temperatures (30–35°C) which provided hot and moist conditions for fungal growth and subsequent aflatoxin contamination. This phenomenal confirmed the findings of Cotty and Jaime-Garcia [15] who stated that influences of delayed harvesting on aflatoxin contamination are most severe when crops are caught by higher than normal temperatures (25–30°C) and high relative humidity just prior to or during harvest (≥70%). Additionally, harvesting groundnut 10 days after physiological maturity coincided with high populations of *Aspergillus* species in the soil which led to high aflatoxin contamination.

The correct drying of harvested groundnuts is very important, as inappropriate drying can help induce fungal growth and reduce kernel quality for consumption and germination for the following season. At harvest, groundnut fruits have a higher moisture content (38–40%) and must be dried to (7–8%) to prevent growth of fungi [25]. This agrees with the current study and furthermore, the drying method greatly influences the resistance of groundnuts to fungal attack. It has been established from the results of this study that both the A-Frame and tarpaulin drying methods were effective in reducing the moisture content of groundnut to the recommended level of ≤7%, and thereby reduced the chances of heavy aflatoxin contamination on the kernels. However, the tarpaulin drying method was more rapid in reducing kernel

to further insect, microbial, and disease infestations [23].

The study also recorded higher aflatoxin contamination levels in the groundnut kernels above the recommended 20 ppb (US standards) at both CIAM and PAN. This could be as a result higher air temperatures (≥30°C) along with elevated relative humidity (≥70%) which provided optimum conditions for fungal invasion especially for the *Aspergillus* section *Flavi* and later production of aflatoxins. This was consistent with the findings of Hell and Mutegi [18] who reported that environmental conditions that favor *Aspergillus* group of fungi included high soil or air temperature (25–30°C), high relative humidity (70–85%), and drought stress.

Field observations have shown that on average, aflatoxin contamination levels were lower at physiological maturity (H2) compared to harvesting at 10 days after physiological maturity (H3). Furthermore, harvesting the crop at H1 had significantly higher aflatoxin contamination levels than harvesting at H2, with some exceptions. The high aflatoxin levels at H1 were attributed to immaturity of pods, higher pod and kernel moisture content, and adverse conditions of wet and humid weather, which provided conducive conditions for fungal invasion and consequently aflatoxin production. Additionally, most of the pods were small and shriveled, which provided direct access to the entry of microorganisms including fungi into the pods and consequently attacking the kernels and later contaminating the crop with aflatoxins. This confirmed the findings of Okello et al. [1] who reported that harvesting groundnuts too early or when the pods are immature result in high aflatoxin levels in the kernels. The findings were also consistent with the findings by Hell et al. [19] who found that aflatoxin contamination was positively correlated with wet weather during harvest (rainfall). It has also been shown that as a result of early harvesting, drying coincided with some postharvest rainfall which led into high aflatoxin contamination of the crop since there was excess moisture which provided suitable conditions for fungal growth and development and production of aflatoxins.

Harvesting 10 days after physiological maturity (H3) resulted into highest levels of aflatoxin contamination compared to H1 and H2 among the groundnut varieties in both study locations. Confirming the study findings by Mphande et al. [20] who reported that postharvest contamination with aflatoxin in groundnut increased when harvesting was executed 5 days after physiological maturity. Additionally, the study has shown that delayed harvesting resulted into higher aflatoxin contamination levels greater than the FDA/WHO regulatory levels of 20 ppb [21]. The high aflatoxin contamination levels at H3 were as a result of heavy damage of pods by insects especially termites (*Odontotermes badius* and *Odontotermes latericus*) which provided the ready entry of fungi including *Aspergillus* species and consequently aflatoxin contamination. Kombiok et al. [22] reported that insects influence the levels of aflatoxin contamination in commodities such as maize and groundnut by carrying fungal inoculum and causing damage that provide the ready entry of the fungus, and thereby increasing the chances of aflatoxin contamination. Furthermore, insects such as termites cause scarification of pods, which weakens the shells and makes them liable to crack during harvesting leading to further insect, microbial, and disease infestations [23].

**4. Discussion**

34 Mycotoxins - Impact and Management Strategies

drought stress.

A number of studies have shown that weather directly influences host susceptibility to aflatoxin contamination [15]. The differences in the intensity of aflatoxin contamination between CIAM and PAN could be attributed to the variability in intensity and duration of rainfall, temperature, and relative humidity between the two locations. In general, CIAM had significantly higher aflatoxin contamination levels compared to PAN. This was attributed to higher than normal temperatures (≥30°C) and late season rainfall which created warm, moist conditions suitable for fungal growth, and subsequent higher aflatoxin contamination levels on the kernels. These outcomes are similar to earlier accounts that wetter and more humid conditions tend to aggravate aflatoxin levels as it enhances the growth of *Aspergillus* species and production of aflatoxins in groundnuts compared to drier climatic conditions [16]. In addition, studies have shown that the optimal temperature range for production of aflatoxin

The study also recorded higher aflatoxin contamination levels in the groundnut kernels above the recommended 20 ppb (US standards) at both CIAM and PAN. This could be as a result higher air temperatures (≥30°C) along with elevated relative humidity (≥70%) which provided optimum conditions for fungal invasion especially for the *Aspergillus* section *Flavi* and later production of aflatoxins. This was consistent with the findings of Hell and Mutegi [18] who reported that environmental conditions that favor *Aspergillus* group of fungi included high soil or air temperature (25–30°C), high relative humidity (70–85%), and

Field observations have shown that on average, aflatoxin contamination levels were lower at physiological maturity (H2) compared to harvesting at 10 days after physiological maturity (H3). Furthermore, harvesting the crop at H1 had significantly higher aflatoxin contamination levels than harvesting at H2, with some exceptions. The high aflatoxin levels at H1 were attributed to immaturity of pods, higher pod and kernel moisture content, and adverse conditions of wet and humid weather, which provided conducive conditions for fungal invasion and consequently aflatoxin production. Additionally, most of the pods were small and shriveled, which provided direct access to the entry of microorganisms including fungi into the pods and consequently attacking the kernels and later contaminating the crop with aflatoxins. This confirmed the findings of Okello et al. [1] who reported that harvesting groundnuts too early or when the pods are immature result in high aflatoxin levels in the kernels. The findings were also consistent with the findings by Hell et al. [19] who found that aflatoxin contamination was positively correlated with wet weather during harvest (rainfall). It has also been shown that as a result of early harvesting, drying coincided with some postharvest rainfall which led into high aflatoxin contamination of the crop since there was excess moisture which provided

suitable conditions for fungal growth and development and production of aflatoxins.

Harvesting 10 days after physiological maturity (H3) resulted into highest levels of aflatoxin contamination compared to H1 and H2 among the groundnut varieties in both study locations. Confirming the study findings by Mphande et al. [20] who reported that postharvest contamination with aflatoxin in groundnut increased when harvesting was executed 5 days

is approximately 25–30°C agreeing with the current study [17].

High aflatoxin contamination levels at H3 could also be attributed to physical damage of pods as a result of digging using hoes. Harvesting groundnut 10 days after physiological maturity coincided with dry weather making it difficult to harvest the groundnuts by hand pulling which led to digging the nuts out of the soil using hand hoes. Similar to the effect of insect damage to pods, physical damage to pods tended to increase with delay in harvesting perhaps due to the dryness of the soil which made pulling and digging out of pods very difficult. As a result, many pods of the groundnut varieties got damaged which favored the entry and invasion of the nuts by *Aspergillus* Section *Flavi* that later produced aflatoxins as a result of respiration. These findings are concurrent with the findings of Hell et al. [18] who indicated that some factors that influence the incidence of fungal infection and subsequent toxin development include invertebrate vectors (insects), grain damage, inoculum load, substrate composition, fungal infection levels, prevalence of toxigenic strains, and microbiological interactions. Moreover, the highest levels of *A. flavus* and *A. parasiticus* infection and aflatoxin contamination are associated with seed damage caused by either insects or physical damage of pods [24].

It has also been observed that delayed harvesting coincided with high relative humidity (≥75%) and higher air/soil temperatures (30–35°C) which provided hot and moist conditions for fungal growth and subsequent aflatoxin contamination. This phenomenal confirmed the findings of Cotty and Jaime-Garcia [15] who stated that influences of delayed harvesting on aflatoxin contamination are most severe when crops are caught by higher than normal temperatures (25–30°C) and high relative humidity just prior to or during harvest (≥70%). Additionally, harvesting groundnut 10 days after physiological maturity coincided with high populations of *Aspergillus* species in the soil which led to high aflatoxin contamination.

The correct drying of harvested groundnuts is very important, as inappropriate drying can help induce fungal growth and reduce kernel quality for consumption and germination for the following season. At harvest, groundnut fruits have a higher moisture content (38–40%) and must be dried to (7–8%) to prevent growth of fungi [25]. This agrees with the current study and furthermore, the drying method greatly influences the resistance of groundnuts to fungal attack. It has been established from the results of this study that both the A-Frame and tarpaulin drying methods were effective in reducing the moisture content of groundnut to the recommended level of ≤7%, and thereby reduced the chances of heavy aflatoxin contamination on the kernels. However, the tarpaulin drying method was more rapid in reducing kernel moisture levels compared to the A-Frame dying method. This was attributed to the direct exposure of the pods to sunlight compared to the shading of pods with leaves when on the A-Frame.

It may be interesting to research the constraints by adopting such practices (when farmers are knowledgeable about the problem). Besides, it is difficult to avoid in the studied areas of Mozambique the ideal situation of an optimal temperature range for production of aflatoxin (between 25 and 30°C). Wet and more humid conditions quite evidently aggravate aflatoxin levels. Scenarios may be useful to better understand the necessary trade-offs to be made by the farmer to optimize harvesting times and drying method depending on the local context (availability of tarpaulin, A-frames, or Mandela Cork dying methods) and weather forecasts. An assessment of the conditions under which [waiting for] physiological maturity is difficult to respect would have been useful and the reasons why damage to the pods cannot be

Effect of Harvesting Time and Drying Methods on Aflatoxin Contamination in Groundnut in Mozambique

http://dx.doi.org/10.5772/intechopen.77300

37

This publication was made possible through the support provided by the Office of Agriculture, Research and Policy, Bureau of Food Security, U.S. Agency for International Development, under the terms of Award No. AID-ECG-A-00-07-0001 to the University of Georgia as management entity for the U.S. Feed the Future Innovation Lab on Peanut Productivity and Mycotoxin Control. The authors would also like to acknowledge the support provided by the Institute of Agricultural Investigation of Mozambique and Eduardo Mondlane University. Special thanks to Limbikani Matumba and Wezi Mhango for provision of useful insights dur-

The opinions expressed herein are those of the author(s) and do not necessarily reflect the

, Manuel I.V. Amane<sup>3</sup>

1 Department of Crop Protection, Faculty of Agriculture and Forestry Engineering, Eduardo

4 Department of Entomology, Center for Turfgrass Environmental Research and Education,

3 Institute of Agriculture Investigation of Mozambique, Maputo, Mozambique

North Carolina State University, Raleigh, North Carolina, United States of America

, Rick L. Brandenburg<sup>4</sup>

,

avoided.

**Acknowledgements**

ing the research period.

**Conflict of interest**

**Author details**

Emmanuel Zuza Jnr<sup>1</sup>

Andrew Emmott<sup>5</sup>

views of the U.S. Agency for International Development.

\*, Amade Muitia<sup>2</sup>

 and Ana M. Mondjana<sup>1</sup> \*Address all correspondence to: manzyzuzajnr@gmail.com

Mondlane University, Maputo, Mozambique

5 Nut Cellars, Bedford, United Kingdom

2 Nampula Research Station, Nampula, Mozambique

Nevertheless, significant differences were observed in aflatoxin contamination levels between A-Frame and tarpaulin drying methods. Lower aflatoxin contamination levels were observed when using the A-Frame (≤10 ppb) compared to tarpaulin drying (≤20 ppb) which had to some extent higher aflatoxin contamination levels. The high aflatoxin contamination levels when using the tarpaulin method were attributed to alterations of the pod and seed coat as a result of direct exposure to sunlight which resulted into creation of microscopic poles and cracks that provided the ready entry of fungi and later aflatoxin production. The advantage of the A-Frame drying method over tarpaulin drying was that it prevented direct exposure of the pods to sunlight and provided increased air circulation as a result of the pods being on a raised platform which led to efficient and effective drying resulting into lower fungal invasion. This confirmed the findings that if drying is too rapid, there are alterations in the seed coat that favor fungal infection [26].

High aflatoxin contamination levels with the tarpaulin drying method could also be as a result of weather conditions. Postharvest abrupt rainfall during the drying period resulted into wetting of pods and prevented drying of the pods to the open sun on some days when it rained all day which resulted into creation of moist conditions conducive for aflatoxin production by the fungi. This was not the case with the A-frame since the pods were covered with leaves and thereby preventing water from reaching the pods and ensuring exposure to air circulation all the time. One of the disadvantages of drying groundnuts on tarpaulins is the time and effort required to gather the pods together and cover them during rain showers and respreading the pods as soon as possible in order to continue drying; this is difficult and the adverse moist conditions as a result of rain provided optimum conditions for fungal invasion and aflatoxin production.

However, in general, it has been observed that both the A-frame and the tarpaulin drying methods were effective in prevention of aflatoxin contamination of the groundnut crop than would traditional methods of drying which involve field and bare ground drying. Furthermore, the A-frame and tarpaulin drying methods ensured that the groundnut crop attained the recommended moisture content (≤7%) and ensured that the crop was not in direct contact with the soil, thereby preventing easy access of fungi to the pods and thus ensuring minimum fungal invasion.
