Reconditioning and Disposition of Aflatoxin-Contaminated Peanut: A Guide for US Peanut Producers

Various biotic and abiotic stresses pose a threat to peanut production. Among these stresses, the soilborne fungi Aspergillus flavus and A. parasiticus contaminate peanut seeds with aflatoxins rendering them unsuitable as food. In this communication, US peanut producers learn about recommendations for reconditioning and disposing of aflatoxin-contaminated peanuts.

Peanuts are produced mainly in the southern United States, with Georgia, Florida, and Alabama being the lead producers (figure 1).¹ Peanuts (Arachis hypogaea) are used for various purposes, including oil extraction, snack, candy, and peanut butter production (figure 1).² The use of peanuts for butter production has increased significantly over the past two decades (figure 1). Various biotic and abiotic stresses pose a threat to peanut production. Among various stresses, the soilborne fungi Aspergillus flavus and A. parasiticus are among the major causes of yield reduction and quality deterioration leading to reduced economic returns and produce wastage. These notorious plant pathogens infect and contaminate peanut seeds with aflatoxins. These infections could occur in the field and during storage. For more information on types of aflatoxins, their flow in the food chain, and management, readers are referred to the “Management of Aflatoxins in Peanut” publication (https://bit.ly/36lYpwU).³

Both A. flavus and A. parasiticus are reported from all peanut-growing regions of the southern United States (figure 2).⁴ These pathogens are present in almost all peanut production regions and infect peanut pods before (in the field) and after harvest (in the storage). The prevalence of the two species varies geographically and corresponds to the type of crops produced and factors like frequencies of drought and soil temperature.⁴ A. flavus is present in fields from east-central Texas to south-central Georgia. The S strain of A. flavus produces numerous small sclerotia (a fungal propagule consists of a compact mass of fungal hyphae) <400 m diameter. The L strain produces sclerotia > 400 m in diameter.⁵ The S strain produces higher quantities of aflatoxin B1 than the L strain and is present primarily in the cotton (Gossypium hirsutum) fields of east-central Texas and Louisiana. The L strain of A. flavus is found in the rest of the areas of occurrence. The highest incidences of A. parasiticus were observed from south-central Alabama to eastern Virginia, with vegetative compatibility group 1 (VCG1) of A. parasiticus widely distributed in peanut fields.⁴ Fungi were assigned to VCGs based on the ability of their hyphae (fungal filaments) to anastomose (form a bridge-like structure that connects the touching hyphae), allowing the exchange of genetic material. Hence, the knowledge of the VCGs is vital in determining which biocontrol product should be applied at a site as it provides information if an atoxigenic biocontrol strain would be able to exchange genetic material with a conventional toxicogenic strain or mate with it sexually, which may lead to the reversal of atoxigenic strains into a toxicogenic strain.^6-8 Both pathogens have a broad host range and infect row and horticultural crops, including peanut (Arachis hypogaea), corn (Zea mays), cotton (Gossypium hirsutum), soybean (Glycine max), tree nuts [pistachio (Pistacia vera), almond (Prunus dulcis) and walnut  (Juglans regia)], chili (Capsicum annuum), and black pepper (Piper nigrum), to name a few. The frequent drought stress and insect infestations favor A. flavus invasion.⁷

Policy for Detoxification/Reconditioning of Peanut Aflatoxin

Currently, no policies exist for the detoxification of aflatoxins in peanuts. However, processes like blanching can reduce contamination levels, as discussed below. The peanut aflatoxin content exceeding the allowed level of 20 ppb must be reported to the US Food and Drug Administration (FDA), which regulates aflatoxin in both food and feed under the Federal Food Drug and Cosmetic Act (FFDCA).⁸ Although the FDA observed action limit for aflatoxins (cumulative) is 20 ppb, in practice, the industry generally follows a strict, self-imposed limit of 15 ppb total aflatoxins for peanuts.⁹ Also, the peanut aflatoxin level (cumulative) observed in different countries varies significantly^10,11 (figure 3), which affects the trade.

Peanut Aflatoxin Reconditioning Procedure

The United States Department of Agriculture (USDA) will allow the reconditioning of aflatoxin-contaminated peanut under the following conditions¹⁴ (as of June 2021):

1. Peanut lots that fail to qualify the certification for human use can be disposed of for livestock consumption (recommendations provided in the next section in table 2). The aflatoxin-contaminated lots should be identified by red tags, and the shipping paper of contaminated lots should state, “The peanuts covered by this bill of lading (or invoice, etc.) are not to be used for human consumption.”
2. Contaminated lots that fail the established quality standards (table 1) may be used for milling. However, if lots satisfy the established quality standards (table 1) after milling, those could be used for human consumption under the required aflatoxin certification.
3. Shelled peanuts that fail the quality standard (table 1) may be blanched. If the peanut lots satisfy the quality standards after blanching (table 1), the lots may be used for human consumption under the required aflatoxin certificates. Damaged kernels and minor defects are exempt from fall-through standards (table 1) before and after blanching.
4. A valid grade inspection certificate should identify lots of shelled peanuts transported for milling or blanching. Milling and blanching should be performed at the USDA-approved centers.
5. Peanuts received after milling or blanching should be identified by red tags and returned to the handler for disposal under the USDA-approved crushers.
6. USDA has the right to reinspect domestic or imported peanuts if they suspect the peanuts to be contaminated, damaged, or deteriorated under the storage conditions. In such a scenario, USDA can reject the then-effective inspection certificate, and the owner may be required to request re-inspection to know if peanuts may or may not be used for human consumption.
7. The peanuts owner should bear the cost of the inspection, transportation, sampling, chemical analysis, identification, milling, blanching, certification, and peanut disposition.

Table 1. Minimum quality standards of shelled peanuts for human consumptions.¹²

Excluding Lots of “Splits”
Type and Grade Category	Moisture (%)	Unshelled Peanuts, Damaged Kernels, and Minor Defects (%)		Foreign Materials (%)			Total Fall Through Sound Whole Kernels and/or Sound Split and Broken Kernels
Runner	9.0	3.50		0.20			6.0%; 17/64 round screen
Virginia (except No. 2)	9.0	3.50		0.20			6.0%; 17/64 round screen
No. 2 Virginia	9.0	3.50		0.20			6.0%; 17/64 round screen
Spanish and Valencia	9.0	3.50		0.20			6.0%; 16/64 round screen
Runner with splits (not more than 15% sound splits)	9.0	3.50		0.20			6.0%; 17/64 round screen
Virginia with splits (not more than 15% sound splits)	9.0	3.50		0.20			6.0%; 17/64 round screen
Spanish and Valencia with splits (not more than 15% sound splits)	9.0	3.50		0.20			6.0%; 16/64 round screen
Lots of “splits”
Type and Grade Category	Moisture (%)		Unshelled Peanuts, Damaged Kernels, and Minor Defects (%)		Foreign Materials (%)	Total Fall Through Sound Whole Kernels and/or Sound Split and Broken Kernels
Runner (not less than 90% splits)	9.0		3.50		0.20	6.0%; 17/64 round screen
Virginia (not less than 90% splits)	9.0		3.50		0.20	6.0%; 17/64 round screen
Spanish and Valencia (not less than 90% splits)	9.0		3.50		0.20	6.0%; 16/64 round screen

Source: FR 57140; Electronic Code of Federal Regulations; 2021

Note: The FDA observed action limit for human consumption is 20 ppb. However, in practice, the industry generally follows a stricter limit of 15 ppb total aflatoxins for peanuts.⁹

Disposition of Aflatoxin Contaminated Peanuts

After receiving the peanut lot’s screening resulting from the reconditioning process, the peanut grain industry must strictly follow the FDA’s aflatoxin disposition policy. Generally, contaminated grains disposition should occur as follows:

1. Peanut screening may be used for animal feed only if the aflatoxin amount meets the FDA-imposed feed guidance (table 2). Once appropriated to be screened for feed use, the screening should not flow back into the human food channel in any manner.¹³
2. Reconditioned peanut that contains less than 20 ppb aflatoxin may be handled without any restriction and regulations. However, when the reconditioning request result again indicates that peanuts exceed the actionable level of 20 ppb aflatoxin, proper disposition should be based on the FDA policy.¹³

For more information regarding the disposition of aflatoxin, contact your local FDA office for specific questions and concerns.

Table 2. FDA aflatoxins limits in animal food.¹⁴

Animal Food Ingredient	Intended Use	Action Level
Peanut products	Finishing (i.e., feedlot) beef cattle	300 ppb
Peanut products	Finishing swine of 100 pounds or greater	200 ppb
Peanut products	Breeding beef cattle, breeding swine, or mature poultry	100 ppb
Peanut products	Immature animals*	20 ppb
Peanut products	Pets (dogs, cats, rabbits, fish, etc.) of all ages	20 ppb
Peanut products	Dairy and other animals, including wildlife, or when the intended use is not known	20 ppb

Source: FDA Sec. 683.100 Action levels for aflatoxins in animal food compliance policy guide. 2019

*For example, ducks and chicken less than 8 weeks old, turkey less than 12 weeks old, pigs, sheep and goats less than 4 months old, equine and cattle less than 6 months old.

Acknowledgments

This work was supported by the National Peanut Board, SC Peanut Board, and NIFA Hatch/Multi-state grant (S009).

References Cited

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