Cottonseed, aflatoxins

Contamination of cottonseed by aflatoxins is a perennial concern. The FDA limits the amount of aflatoxin in cottonseed meal intended for beef catde, swine, and poultry to 300 ppb and for dairy catde the limit is 20 ppb. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

A protocol approved by the FDA to determine the safety of low gossypol cottonseed kernels for human consumption was the basis for the second study by Reber (7 ). To prepare raw cottonseed flour, raw kernels were ground to meet Ro-tap sieve specifications of lab chow. To prepare roasted cottonseed flour, raw kernels were dry roasted at not less than 121°C for not less than 5 min. To prepare cooked cottonseed flour, raw kernels were cooked in steam until batch temperature had been at or above 121°C for 5 min. All cottonseed kernels were ground in the manner described above. The kernels contained not more than 0.037% (370 ppm) of free gossypol. They were free of Salmonella and did not contain detectable amounts of aflatoxin. The proximate analyses of the cottonseed flours are shown in Table I. 

Cotty, P.J., Effect of atoxigenic strains of Aspergillus flavus on aflatoxin contamination of developing cottonseed, PL Dis., 74, 808, 1990. 

DETAILS - Aflatoxins are the poisonous product of a group of polynuclear molds that grow on peanuts, com and in cottonseed meal. They are responsible for the Turkey X" disease which occasionally devastates the poultry industry. The presence of the mold doesn t always indicate presence of the toxin. Toxin production is dependent on various factors such as moisture and temperature. There are two basic types of aflatoxins, both of which are fluorescent under UV (black) light. Once the mold has been identified, the UVI ight is an excellent way to check for toxin production. Aflatoxin B glows blue, while Aflatoxm G glows... 

Table L Prevention of aflatoxin contamination of cottonseed by toxigenic strains of AspergiUus flavus with a strain of the fungus which does not produce aflatoxins (Cotty, 1989. Proc. 38th Oilseed Processing Clinic, pg. 30)...

Several approaches are being explored and developed using new methods in biotechnology to eliminate pre-harvest aflatoxin contamination of food and feed. These approaches resulted from recent information acquired on 1) non-aflatoxigenic A. flavus strains that prevent aflatoxin contamination of cottonseed when co-inoculated with aflatoxigenic strains, 2) molecular mechanisms governing aflatoxin biosynthesis, and 3) plant-derived metabolites that inhibit aflatoxin biosynthesis. 

The uneven distribution of mycotoxins in grain has so far been statistically defined only for aflatoxins in a few matrices (corn, cottonseed, peanuts) (15,16), and sampling plans have been developed worldwide almost entirely for these toxins. 

Aflatoxins are potent carcinogenic, mutagenic and teratogenic metabolites produced by molds. The major food affected with aflatoxins are corn, peanuts, rice, cottonseeds, dried fruit and milk from ingestion (103). The US action standards established by FDA are 20 pg/Kg for foods consumed by humans and 0.5 pg/kg for milk. In the case of animal feed, the levels are from 100 to 300 pg/kg. Therefore, assays capable of detecting at these levels have to be developed, (see Table 1 (104,105)). Detection of aflatoxins entails conjugation of these small molecules with carrier proteins like bovine serum albumin to produce antibodies (20). A number of commercial kits for aflatoxins are available (see sections on kits and immunoaflinity purification). 

Aflatoxin Bi in Cottonseed Products and mixed Feed ELISA Screening Method (Agri-screen) Neogen Corp. 989.06 126... 

Aflatoxin Bi, B2, and Gl in Com, Cottonseed, Peanuts and Peanut Butter ELISA Screening Assay (ImmunoDot Screen Cup) International Diagnostic Systems Corporation 990.34 104... 

In the early 1980s, when it appeared that hexane was in short supply, Johnson et al. described a 56-h pilot plant extrachon of cottonseed using an alternative solvent, methylene chloride (dichloromethane) (158). This solvent extracted the oil and signihcantly reduced levels of the antinutrients gossypol and aflatoxin. However, because of environmental concerns, the commercial use of halogenated hydrocarbons in solvent extraction has not occurred. 

Acetone as a Solvent. Acetone is an excellent solvent for cottonseed oU and for the antinutrients gossypol and aflatoxin. Acetone has found some commercial success in Sicily where Vaccarino used 96% aqueous acetone in a 50 ton/day batch process plant (162, 163). However, acetone has not had any other modern successes, probably because it produces a dark and hard-to-bleach cottonseed and because it imparts a disagreeable cat-like odor to the extracted meal. 

Alcohols as Solvents. As a result of environmental concerns and inability of hexane to extract gossypol and aflatoxin, recent research on the solvent extraction of cottonseed has centered on developing processes using ethanol and isopropanol. The use of these alcohols to extract cottonseed and many other oilseeds is not new. 

Overall correlation (81%) between the ELISA instrumental results and those obtained using the AOAC recommended methods was good. On this basis the AOAC adopted the ELISA method official first action as a screening method for determining the presence or absence of aflatoxin B, at a concentration of >15 ng/g in cottonseed products and mixed feeds, a surprising conclusion in view of the relatively large numbers of both false positive and false negative results encountered. On the other hand, when an ELISA reader was used for quantitation, the RSD, was <51% for cottonseed products and mixed feeds at levels >15 ppb for all other commodities the RSD, was... 

All collaborators correctly identified naturally contaminated corn (101 ng/g) and raw peanut (69 ng/g) positive samples. No false positives were found for control samples containing <2 ng/g. Overall (excluding poultry feed) the average correct responses for spiked positive samples at 10, 20 and >30 ng/g levels were 52, 86 and 96%, respectively (see Figure 2). The method was rapid and simple and was adopted Official First Action by the AOAC as a screening procedure for aflatoxins at >20 ng/g in cottonseed and peanut butter, and >30 ng/g in corn and raw peanuts. (In this case the AOAC required a positive rate of 90% for acceptance.)... 

Asp. Flavus develops on the leaves and blossoms of plants and prevails in maze, cottonseeds and walnuts. It synthesizes Bl and B2 aflatoxins (Santacroce et al. 2007). 

Certain types of molds can produce mycotoxin. A. flavus and A. parasiticus, under favorable conditions of temperature and humidity, can produce aflatoxins. Produces that are commonly contaminated with aflatoxins are groundnut, maize, chili, spices, and cottonseed (Cotty and Jaime-Garcia, 2007 Kumar et al., 2008). Mycotoxins can also occur in milk and milk products as a result of animals consuming mycotoxin-contaminated feed (Moss, 2002 Cotty and Jaime-Garcia, 2007). P. expansum, causing blue mold rot, can produce toxin called patulin (Barkai-Golan and Paster, 2008 Kumar et al., 2008). 

---