Relationship between aflatoxin production and mold growth as measured by ergosterol and plate count

LWT ◽  
1995 ◽  
Vol 28 (2) ◽  
pp. 185-189 ◽  
Author(s):  
H. Gourama ◽  
L.B. Bullerman
1981 ◽  
Vol 64 (4) ◽  
pp. 955-960
Author(s):  
Gerald C Llewellyn ◽  
Mary Lee Burkett ◽  
Thomas Eadie

Abstract Ground spices and herbs are evaluated as substrates for mycelial growth, sporulation, and aflatoxin production. Three toxigenic strains of Aspergilli, A. flavus ATCC 15548, A. flavus NRRL 3251, and A. parasiticus NRRL 2999, were cultured on moist, commercially packaged herbs and spices. All substrates used were ground and included thyme, celery seed, oregano, cinnamon, ginger, caraway seed, clove, mustard, sesame seed, and rosemary leaves. Following inoculation of the natural materials in sterile bottles containing sterile water, the cultures were incubated 30 days at 23 ± 4°C. Not all strains of Aspergilli grew, sporulated, or produced toxins. There were definite strain differences and definite substrate differences for the variables evaluated. Sesame seed produced toxins B1, G1, and G2, with a mean of 167 ppm for 3 strains. A. flavus ATCC 15548 was the greatest overall toxin producer followed by A. partsiticus NRRL 2999 and A. flavus NRRL 3251. Ginger and rosemary leaves were also substantial producer-substrates. Mustard, caraway seed, and celery seed were judged as intermediate-producing substrates. Absolute antimycotic substrates were cinnamon and clove. Antiaflatoxigenic substrates were thyme and oregano. Mustard also may be antimycotic. Aflatoxins B1 and G1 were the more commonly found toxins


1990 ◽  
Vol 53 (3) ◽  
pp. 230-236 ◽  
Author(s):  
ANJANI KARUNARATNE ◽  
ELENORA WEZENBERG ◽  
LLOYD B. BULLERMAN

The effect of three individual species of lactobacilli (Lactobacillus acidophilus, L. bulgaricus, and L. plantarum) and a commercial silage inoculant, containing three different strains of the same species, on growth and aflatoxin production of A. flavus subsp. parasiticus NRRL 2999 was determined. The study was done in three substrates; a liquid semi-synthetic broth, rice, and corn. The effect of the growing cell masses of the lactobacilli as well as the effect of metabolic products contained in cell free filtrates were determined in the liquid medium. The cells were effective in preventing growth of the mold, and bacterial metabolites were effective in reducing the amount of aflatoxin produced, although growth was not affected. The prevention of growth that was observed was determined to be relative to a pH effect and microbial competition; however, the lower levels of aflatoxin obtained in the presence of cell free supernatant culture fluids could not be explained on the basis of pH or competition. Mold growth was not affected by the presence of the silage inoculant on the rice and corn. However, increased levels of aflatoxin B1 were observed in the presence of the silage inoculant on rice, and decreased levels of aflatoxin G1 were observed on the presence of the silage inoculant on corn.


1981 ◽  
Vol 44 (10) ◽  
pp. 736-741 ◽  
Author(s):  
AHMED E. YOUSEF ◽  
ELMER H. MARTH

Two media [basal (M1) and enriched (M2)] containing potassium sorbate (0–300 ppm as sorbic acid) were inoculated with spores (104 – 106/flask) of Aspergillus parasiticus and incubated for 5 days at 28 C. The greater the amount of sorbate added, the higher was the pH of the media after incubation and the smaller was the yield of mold mycelium. Intermediate amounts of sorbate sometimes resulted in greater accumulation of aflatoxin than when media were free of sorbate. Sorbate more effectively inhibited mold growth and aflatoxin production in medium M2 than M1 and when the small rather than the large inoculum was used. A second trial was done with 106 or 105 spores/flask of M2 (ca. 27 ml) and 105 spores/flask of M2 (ca. 27 ml) containing sorbate (200 ppm of sorbic acid). Cumulative data for mold growth. pH and content of aflatoxin in the medium showed that relative effects of different treatments changed during the incubation period. An index to measure the capacity of molds to synthesize aflatoxins was developed. Application of the index indicates that sorbate delayed mold growth but did not inhibit biosynthesis of aflatoxin. The ability to synthesize aflatoxin was greatest in the early stages of mold growth and then decreased linearly as mold growth progressed.


1983 ◽  
Vol 46 (3) ◽  
pp. 210-215 ◽  
Author(s):  
JAERIM BAHK ◽  
ELMER H. MARTH

Red ginseng saponin (0.36%) inhibited mycelial growth, sporulation and aflatoxin production by Aspergillus parasificus during 9 d at 28°C. The mold caused no change in pH of the medium when it contained red ginseng saponin or ginseng tea (9%). Most ginseng products permitted mycelial growth and production of aflatoxin B1, but inhibited production of aflatoxin G1. However, when compared to the control, aflatoxin production by A. parasiticus was reduced by the presence in the medium of most of the ginseng products that were tested, Ginseng tea (9%) resulted in a higher index of maximum accumulation of aflatoxins per interval of mold growth than occurred in the control. Red ginseng was more effective than white ginseng for inhibiting mold growth and aflatoxin production.


1982 ◽  
Vol 65 (3) ◽  
pp. 659-664 ◽  
Author(s):  
Gerald C Llewellyn ◽  
Thomas Eadie ◽  
William V Dashek

Abstract The susceptibility of blackberries, cherries, and strawberries to Aspergillus growth and aflatoxin production has been examined. Three aflatoxigenic isolates of Aspergillus, A. flavus ATCC 15548 and NRRL 3251 as well as A. parasiticus NRRL 2999, were cultured on homogenates of the fruits for 14 days at 28 ± 2°C. Percent mycelial growth and spore infestation were determined each day with a calibrated grid. At day 14 each culture was frozen at –5°C until aflatoxins were extracted with methylene chloride and water. Aflatoxins were separated by thin layer chromatography (TLC) with benzene-methanol-acetic acid (90 + 5 + 5). This extraction and solvent system provided satisfactory separations of the aflatoxins and was free of background interference on the TLC plates. Although all fruits served as substrates for both Aspergillus growth and aflatoxin production, cherries appeared to be a more favorable substrate than did blackberries, and the latter was more favorable than strawberries. Whereas A. flavus produced both B1 and G1 on all substrates, it yielded B2 and G2 only on cherries. Although A. parasiticus NRRL 2999 synthesized B1, B2, G1, and G2 on both blackberries and cherries, no aflatoxins were detected on strawberries. In contrast, A. flavus NRRL 3251 failed to produce detectable levels of aflatoxin on any substrate. All substrates supported both mycelial growth and subsequent sporulation with cherries > blackberries > strawberries.


1988 ◽  
Vol 51 (5) ◽  
pp. 361-363 ◽  
Author(s):  
MARY W. TRUCKSESS ◽  
LEONARD STOLOFF ◽  
PHILIP B. MISLIVEC

Portions of corn, a commodity in which aflatoxin is frequently found, were held at 16, 26 and 32°C after the moisture contents were adjusted to achieve water activities (aw) ranging from too low to ample for support of mold growth. Suspensions of mold spores from toxigenic cultures of Aspergillus flavus, A. ochraceus, Penicillium citrinum, P. cyclopium and P. urticae were added to the test portions, either as A. flavus alone, as A. flavus with one of the other molds or as a mixture of all 5 species. Additional water was used to obtain the proper moisture levels. A temperature of 16°C was generally too low for aflatoxin production by either the added or native strains of A. flavus, although the mold was able to grow at 16°C at aw values as low as 0.80, 0.77 and 0.85 on corn, soybeans and pinto beans, respectively. Aflatoxin production was essentially the same at 26 and 32° C with limiting aw values in the range of 0.85–0.89. Limiting aw values for mold growth at 26 and 32°C were 0.73, 0.69 and 0.75 for corn, soybeans and pinto beans, respectively. This study provided no evidence that substrate suitability at limiting temperatures and aw levels is a factor in the observed difference in the risk of aflatoxin contamination for these commodities. The study did indicate that the associated mold flora, when the seed is exposed to mold invasion, is a risk determinant.


1984 ◽  
Vol 47 (8) ◽  
pp. 637-646 ◽  
Author(s):  
LLOYD B. BULLERMAN ◽  
LISA L. SCHROEDER ◽  
KUN-YOUNG PARK

Mycotoxin production is favored by high humidity and high water activity (aw). To control mycotoxin formation on the basis of moisture, the moisture content must be maintained below a certain critical level for each commodity. Aflatoxin production is favored by temperatures of 25 to 30°C, whereas below 8 to 10°C, aflatoxin production can occur, but the amounts produced are less and the time required for production is longer. Cycling or changing temperature may or may not increase aflatoxin production, depending on the temperatures, mold species and substrates involved. Other mycotoxic molds respond to temperature differently than the aspergilli. Species of Penicillium, Fusarium and Cladosporium are capable of growing at temperatures below 5°C, and some even just below freezing. Penicillium spp. can produce patulin, penicillic acid and ochratoxin at temperatures from 0 to 31°C, whereas Aspergillus ochraceus does not produce ochratoxin or penicillic acid below 12°C. Penitrem production by Penicillium crustosum can occur at refrigeration temperature. Fusarium spp. can produce zearalenone and the trichothecenes at temperatures below 10°C and even below freezing. Maintaining storage temperatures of stored commodities at 5°C or lower will prevent the production of aflatoxins and ochratoxin by aspergilli but will not prevent the production of mycotoxins by Penicillium spp. and Fusarium spp. Mycotoxic molds may grow on a vast array of substrates, but some substrates support little or no mycotoxin production while supporting extensive mold growth. Most substrates that support aflatoxin production are plant products, such as peanuts, Brazil nuts, pecans, walnuts, almonds, filberts, pistachio nuts, cottonseed, copra, corn sorghum, millet and figs. Animal products are less likely substrates for aflatoxin production. The main source of aflatoxins in animal products are residues in milk and animal tissues as a result of consumption of toxic feed by the animal. Some herbs and spices have antifungal properties and do not support mycotoxin production. However, aside from this, most food substrates are susceptible to mold growth and mycotoxin production. Some substrates, such as cheese, cured meats and soybeans, might be less favorable for mycotoxin production, but may still support mycotoxin formation. Drought stress, insect damage and mechanical damage may increase the ability of Aspergillus flavus and other fungi to invade peanuts, cottonseed and grain. Some measure of control can be gained by minimizing drought stress through irrigation and minimizing insect and mechanical damage. Development of peanut varieties and corn hybrids that are resistant to preharvest invasion by A. flavus may also offer some measure control. Competing microorganisms tend to restrict fungal growth and mycotoxin production. Low oxygen concentration (<1%) and/or increased concentrations of other gases (i.e., >90% CO2) may depress mold growth and mycotoxin formation. Antimycotic agents can be used to control mold growth and mycotoxin production. Sorbic acid, potassium sorbate, propionic acid and propionates appear to be more effective antimycotics over a greater range of conditions than benzoates. Other substances, such as sodium diacetate and BHA, also have antifungal activity. Certain herbs and spices, particularly cinnamon, cloves and mustard, may contain enough antifungal activity to exert a protective effect at normal usage levels.


1992 ◽  
Vol 55 (8) ◽  
pp. 583-587 ◽  
Author(s):  
ROSA H. LUCHESE ◽  
JOSÉ F. P. MARTINS ◽  
WILKIE F. HARRIGAN

The effect on aflatoxin production by Aspergillus parasiticus of eight individual strains of Pediococcus and Lactobacillus was determined. The study was conducted in an axenic cultural system in which irradiated meat was employed in the formulation of a meat medium. The medium composition and incubation temperatures were simulations of Brazilian salami processing conditions. All single cultures of A. parasiticus supported aflatoxin production. More aflatoxin was produced in samples treated by the addition of lactic acid than in nontreated ones. Aflatoxin was not detected when A. parasiticus was grown with lactic acid bacteria, although visible mold growth was observed in all such cultures.


1995 ◽  
Vol 58 (11) ◽  
pp. 1249-1256 ◽  
Author(s):  
HASSAN GOURAMA ◽  
LLOYD B. BULLERMAN

A mixture of Lactobacillus species from a commercial silage inoculum reduced mold growth and inhibited aflatoxin production by Aspergillus flavus subsp. parasiticus. Actively growing Lactobacillus spp. cells totally inhibited germination of mold spores. Culture supernatant broth from the mixture of strains inhibited mold growth but did not destroy mold spore viability. Some mold spores were observed microscopically to have germinated and produced short nonbranching germ tubes; then growth ceased. While the pH of the culture broth and supernatant were about 4.0, acidification of nonfermented broth to pH 4.0 with HCl and lactic acid did not cause a similar inhibition of spore germination. The mixture of Lactobacillus species growing in a dialysis sack inhibited aflatoxin production by the A. flavus culture growing outside of the sack in broth, whereas mold growth was not affected. The pH values outside of the dialysis sack in the control and the treatments were similar (6 to 7) throughout the incubation period. When a dialysis sack with a molecular weight cutoff (MWCO) of 1,000 was used, there was little inhibition of aflatoxin B1 production, but with MWCOs of 6,000 to 8,000 and 12,000 to 14,000 aflatoxin production was greatly inhibited. In mixed culture experiments, levels of aflatoxin B1 and G1 were depressed compared to the control (monoculture). Mold growth in this case was also reduced compared to the monoculture system. Purified isolates of Lactobacillus from the commercial mixture had a slight effect on mold growth and aflatoxin production, but supernatant liquid of one isolate was quite inhibitory to production of aflatoxins B1 and G1, without affecting mold growth.


1994 ◽  
Vol 57 (2) ◽  
pp. 136-140 ◽  
Author(s):  
SHAO W. FANG ◽  
CHIN F. LI ◽  
DANIEL Y. C. SHIH

The inhibitory effect of chitosan, a deacetylated form of chitin, on the growth of Aspergillus niger and the aflatoxin production of Aspergillus parasiticus was evaluated. The inhibitory effect of chitosan against A. niger was increased as the chitosan concentration was increased from 0.1 to 5.0 mg/ml (pH 5.4). At concentrations of 4.0 or 5.0 mg/ml, chitosan was less effective than potassium sorbate in inhibiting the growth of A. niger. The greatest inhibitory effect of chitosan against A. parasiticus was found at 3.0–5.0 mg/ml. In addition, chitosan could completely prevent aflatoxin production by A. parasiticus at the concentration of 4.0–5.0 mg/ml. Chitosan (2.0 and 5.0 mg/ml) induced considerable leakage of UV-absorbing and proteinaceous material of A. niger at pH 4.8. Using the response surface methodology, a second order polynomial model was derived and used to predict the number of days to obtain visible mold growth under various combinations of chitosan concentrations and °Brix in candied kumquat. The results showed that there was no significant difference in shelf-life extension of candied kumquat at chitosan concentration of 3.5–6.5 mg/ml. However, °Brix had a significant effect on shelf life. Candied kumquat with 6.0 mg/ml chitosan concentration and 61.9° Brix had a predicted mold-free shelf life of 65.3 d.


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