Aflatoxin adsorption from aqueous corn meal dispersions
was used as a more applied and more conservative measure of
aflatoxin retention. Batch adsorption isotherms from aqueous
corn meal (6 points in triplicate with 4 blanks) were prepared
with an initial concentration of 1.5 μg AfB1/mL (3 μg AfB1/g
corn meal) in 2-mL aqueous dispersions containing 1 to 20 mg
(0.1 to 2%) clay or activated carbon and 1.00 g of corn meal.
Blanks were prepared similarly using only AfB1, corn meal,
and water. The 3 μg AfB1/g corn meal is comparable to
highly-contaminated (3000 μg aflatoxins/kg) grain. The
samples were thoroughly mixed using a vortex mixer. After
overnight agitation on a reciprocating shaker, 8 mL of a 60%
methanol/40% 2 M NaCl extracting solution was mixed with
the samples using a vortex mixer. The tubes were centrifuged
and the supernatants passed through 0.2-μm filters and
collected in 20-mL plastic vials. Aflatoxins are more soluble
in methanol than in water. The 60% methanol extraction was
modified from the Asis et al. (2002) procedure to extract and
measure aflatoxins in peanuts. The AOCS method for
aflatoxins in corn, cottonseed, peanuts, and peanut butter
similarly uses an 80% methanol/20% water extraction (AOCS,
1999b).
Aflatoxin adsorption from aqueous corn meal dispersions
was used as a more applied and more conservative measure of
aflatoxin retention. Batch adsorption isotherms from aqueous
corn meal (6 points in triplicate with 4 blanks) were prepared
with an initial concentration of 1.5 μg AfB1/mL (3 μg AfB1/g
corn meal) in 2-mL aqueous dispersions containing 1 to 20 mg
(0.1 to 2%) clay or activated carbon and 1.00 g of corn meal.
Blanks were prepared similarly using only AfB1, corn meal,
and water. The 3 μg AfB1/g corn meal is comparable to
highly-contaminated (3000 μg aflatoxins/kg) grain. The
samples were thoroughly mixed using a vortex mixer. After
overnight agitation on a reciprocating shaker, 8 mL of a 60%
methanol/40% 2 M NaCl extracting solution was mixed with
the samples using a vortex mixer. The tubes were centrifuged
and the supernatants passed through 0.2-μm filters and
collected in 20-mL plastic vials. Aflatoxins are more soluble
in methanol than in water. The 60% methanol extraction was
modified from the Asis et al. (2002) procedure to extract and
measure aflatoxins in peanuts. The AOCS method for
aflatoxins in corn, cottonseed, peanuts, and peanut butter
similarly uses an 80% methanol/20% water extraction (AOCS,
1999b).
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