712 Modern Food Microbiology
during aging when temperatures approached 30
◦ C, but not at temperatures below 15
◦ C or relative
humidity (RH) above 75%.
10 They have been found in a wide variety of foods, including milk, beer,
cocoa, raisins, soybean meal, and so on (see below). In fermented sausage at 25
◦ C, 160 and 426 ppm
of AFG 1 were produced in 10 and 18 days, respectively, and 10 times more AFG 1 was found than
B 1 .
51 Aflatoxins have been produced in whole-rye and wholewheat breads, in tilsit cheese, and in
apple juice at 22
◦ C. They have been demonstrated in the upper layer of 3-month-old cheddar cheese
held at room temperature
52 and on brick cheese at 12.8
◦ C by A. parasiticus after 1 week but not for A.
flavus.
78 AFB 1 was found in 3 of 63 commercial samples of peanut butter at levels less than 5 ppb.
69
From a 5-year survey of around 500 samples of Virginia corn and wheat, aflatoxins were detected in
about 25% of corn samples for every crop year, with 18–61% of samples containing 20 ng/g or more
and 5–29% containing more than 100 ng/g.
80 The average quantity detected over the 5-year period
was 21–137 ng/g. Neither aflatoxins nor zearalenone and ochratoxin A were detected in any of the
wheat samples. The 1988 drought led to an increase in the amount of aflatoxin produced in corn in
some midwestern U.S. states that received less than 2 inches of rain in June and July. About 30% of
samples contained more than 20 ppb compared to 2–3 ppb levels during normal rainfall.
83
In a study of AFB 1 in foods and feedstuffs in Cuba for the years 1990–1996, 17% of 4529 samples
were positive with 83% of sorghum and 40% of peanuts being the most contaminated.
32 The incidence
in corn was 23 and 25% in wheat. In Botswana, 120 peanut samples were tested for aflatoxin and 78%
were positive at levels from 12 to 329 µg/kg, and 49% contained >20 µg/kg.
59 Twenty-one percent
of these samples contained cyclopiazonic acid at levels from 1 to 10 µg/kg.
Cyclopiazonic acid is produced by some A. flavus strains and it is thought to contribute to the
toxicity of aflatoxin. In an examination of seven truckloads of corn, it was found in four at levels of
25–250 ng/g.
49 Also found in four of five loads was deoxynivalenol (DON, vomitoxin) at levels of
46–676 ng/g.
The effect of temperature cycling between 5
◦ and 25
◦ C on production in rice and cheese has been
investigated. A. parasiticus produced more toxin under cycling temperatures than at 15
◦ , 18
◦ , or 25
◦ C,
while A. flavus produced less under these conditions.
68 On cheddar cheese, however, less aflatoxin was
produced than at 25
◦ C, and these investigators noted that cheese is not a good substrate for aflatoxin
production if it is held much below the optimum temperature for toxin production.
Aflatoxin production has been demonstrated to occur on an endless number of food products in
addition to those noted. Under optimal conditions of growth, some toxin can be detected within 24
hours—otherwise within 4–10 days.
18 On peanuts, Hesseltine
40 has made the following observations:
1. Growth and formation of aflatoxin occur mostly during the curing of peanuts after removal from
soil.
2. In a toxic lot of peanuts, only comparatively few kernels contain toxin, and success in detecting
the toxin depends on collecting a relatively large sample, such as 1 kg, for assay.
3. The toxin will vary greatly in amount even within a single kernel.
4. The two most important factors affecting aflatoxin formation are moisture and temperature.
The U.S. Food and Drug Administration (FDA) has established allowable action levels of aflatoxins
in foods as follows: 20 ppb for food, feeds, Brazil nuts, peanuts, peanut products, and pistachio
nuts; and 0.5 ppb for milk.
48 A committee of the Codex Alimentarius Commission has recommended the following maximum levels of mycotoxins in specific foods: 15 µg/kg of aflatoxins in
peanuts for further processing; 0.05 µg/kg of aflatoxin M 1 in milk; 50 µg/kg of patulin in apple juice
and apple juice ingredients in other beverages; and 5 µg/kg of ochratoxin A in cereals and cereal
products.
61
during aging when temperatures approached 30
◦ C, but not at temperatures below 15
◦ C or relative
humidity (RH) above 75%.
10 They have been found in a wide variety of foods, including milk, beer,
cocoa, raisins, soybean meal, and so on (see below). In fermented sausage at 25
◦ C, 160 and 426 ppm
of AFG 1 were produced in 10 and 18 days, respectively, and 10 times more AFG 1 was found than
B 1 .
51 Aflatoxins have been produced in whole-rye and wholewheat breads, in tilsit cheese, and in
apple juice at 22
◦ C. They have been demonstrated in the upper layer of 3-month-old cheddar cheese
held at room temperature
52 and on brick cheese at 12.8
◦ C by A. parasiticus after 1 week but not for A.
flavus.
78 AFB 1 was found in 3 of 63 commercial samples of peanut butter at levels less than 5 ppb.
69
From a 5-year survey of around 500 samples of Virginia corn and wheat, aflatoxins were detected in
about 25% of corn samples for every crop year, with 18–61% of samples containing 20 ng/g or more
and 5–29% containing more than 100 ng/g.
80 The average quantity detected over the 5-year period
was 21–137 ng/g. Neither aflatoxins nor zearalenone and ochratoxin A were detected in any of the
wheat samples. The 1988 drought led to an increase in the amount of aflatoxin produced in corn in
some midwestern U.S. states that received less than 2 inches of rain in June and July. About 30% of
samples contained more than 20 ppb compared to 2–3 ppb levels during normal rainfall.
83
In a study of AFB 1 in foods and feedstuffs in Cuba for the years 1990–1996, 17% of 4529 samples
were positive with 83% of sorghum and 40% of peanuts being the most contaminated.
32 The incidence
in corn was 23 and 25% in wheat. In Botswana, 120 peanut samples were tested for aflatoxin and 78%
were positive at levels from 12 to 329 µg/kg, and 49% contained >20 µg/kg.
59 Twenty-one percent
of these samples contained cyclopiazonic acid at levels from 1 to 10 µg/kg.
Cyclopiazonic acid is produced by some A. flavus strains and it is thought to contribute to the
toxicity of aflatoxin. In an examination of seven truckloads of corn, it was found in four at levels of
25–250 ng/g.
49 Also found in four of five loads was deoxynivalenol (DON, vomitoxin) at levels of
46–676 ng/g.
The effect of temperature cycling between 5
◦ and 25
◦ C on production in rice and cheese has been
investigated. A. parasiticus produced more toxin under cycling temperatures than at 15
◦ , 18
◦ , or 25
◦ C,
while A. flavus produced less under these conditions.
68 On cheddar cheese, however, less aflatoxin was
produced than at 25
◦ C, and these investigators noted that cheese is not a good substrate for aflatoxin
production if it is held much below the optimum temperature for toxin production.
Aflatoxin production has been demonstrated to occur on an endless number of food products in
addition to those noted. Under optimal conditions of growth, some toxin can be detected within 24
hours—otherwise within 4–10 days.
18 On peanuts, Hesseltine
40 has made the following observations:
1. Growth and formation of aflatoxin occur mostly during the curing of peanuts after removal from
soil.
2. In a toxic lot of peanuts, only comparatively few kernels contain toxin, and success in detecting
the toxin depends on collecting a relatively large sample, such as 1 kg, for assay.
3. The toxin will vary greatly in amount even within a single kernel.
4. The two most important factors affecting aflatoxin formation are moisture and temperature.
The U.S. Food and Drug Administration (FDA) has established allowable action levels of aflatoxins
in foods as follows: 20 ppb for food, feeds, Brazil nuts, peanuts, peanut products, and pistachio
nuts; and 0.5 ppb for milk.
48 A committee of the Codex Alimentarius Commission has recommended the following maximum levels of mycotoxins in specific foods: 15 µg/kg of aflatoxins in
peanuts for further processing; 0.05 µg/kg of aflatoxin M 1 in milk; 50 µg/kg of patulin in apple juice
and apple juice ingredients in other beverages; and 5 µg/kg of ochratoxin A in cereals and cereal
products.
61