[On the presence and the content of aflatoxin M in commercial cheese samples (author's transl)]

Determination of aflatoxin M1 levels in Iranian white and cream cheese

A screening survey on the occurrence of aflatoxin M1 (AFM1) was accomplished on 210 cheese samples composed of white cheese (116 samples) and cream cheese (94 samples) purchased from popular markets in central part of Iran (Esfahan and Yazd provinces). The quantitative analysis of AFM1 levels in the samples was performed by using the competitive enzyme-linked immunosorbent assay (ELISA) technique. Aflatoxin M1 at measurable level (50 ng/kg) was detected in 161 (76.6%) samples, consisting of 93 (80.1%) white and 68 (72.3%) cream cheese samples. The concentration of AFM1 in the samples ranged from 52.1 to 785.4 ng/kg. Comparing to legal regulation (250 ng/kg) accepted by some of the countries, 24.2% of the samples exceeded the accepted limit. Among these, the AFM1 levels in 28.4% of white and 19.1% of cream cheese samples were not in accordance with the safety limit. The results indicated that contamination of the samples with AFM1 in such a level appear to be a potential hazard for public health. This paper represents the data of the first survey on the occurrence of AFM1 in cheeses consumed in central part of Iran.

Reduction of aflatoxin M1 in milk using hydrogen peroxide and hydrogen peroxide plus heat treatment

Use of hydrogen peroxide (H2O2) under various conditions of temperature and time to inactivate aflatoxin M1 in artificially contaminated raw milk was examined. The degree of inactivation was measured by Enzym Linked Immunosorbent Assay (ELISA). It appeared that there is no change in the content of aflatoxin M1 in milk contained H2O2 and examined after 24 hours without heat treatment and in contaminated milk without add of H2O2 and heat treated treatment at (63 degrees C for 30 min, 75 degrees C for 15 sec) but slight inactivation (4.3%) was obtained in milk boiled for 5 min without H2O2. Maximum inactivation (27.8%, 28.8% and 45.1%) were obtained using 1% H2O2 followed by heat treatment at 36 degrees C for 30 min, 75 degrees C for 15 sec and boiling for 5 min respectively.

Presence of aflatoxin M1 in commercial ultra-high-temperature-treated milk

Forty-seven samples of commercial ultra-high-temperature-treated milk from a dairy facility in the northwest part of Spain were analyzed for the presence of aflatoxin M1. A total of 14 samples (29.8%) were positive for aflatoxin M1 (4 in May, 3 in November, 3 in December, 1 in January, 1 in April, 1 in July, and 1 in August), 29 (61.7%) were negative, and 4 (8.5%) were doubtful, i.e., they showed trace quantities of aflatoxin M1. The range of aflatoxin M1 content was 0.02 to 0.1 ng/ml.

Association of aflatoxin M1 with casein

Equilibrium dialysis was used to determine whether aflatoxin M1 (AFM1) binds to casein. Simulated milk ultrafiltrate (SMUF) containing 10 or 20 ng/ml of AFM1 was dialyzed against SMUF containing casein micelles. After 24 h at 7 degrees C, the casein suspension contained 2.5- or 2.9-fold, respectively, more toxin than that found in SMUF. An average of 17.9 or 55.3 micrograms of AFM1, respectively, per gram of casein was bound. In a separate experiment, milk naturally contaminated with AFM1 was treated with a proteolytic enzyme. An average of 30.7% more toxin was found in treated than in untreated milk. This result also suggests binding of AFM1 by milk protein.

Studies on the formation of aflatoxin M1 in bakery products. Mycotoxins in foodstuffs. XIII

The aflatoxinogenic moulds Aspergillus flavus NRRL 3251, A.parasiticus CMI 89717 and A.parasiticus NRRL 2999 are able to grow on various types of bread, yet, only the last fungus can produce aflatoxin M1 on these substrates. The highest yields (4 micrograms/kg) of the toxin were found on whole wheat bread at a "Säuregrad" (total acid content) of 5-6 and at an incubation temperature of 30 degrees C. The toxin levels decreased with increasing time of growth; this was probably due to a further metabolism of aflatoxin M1. A.flavus NRRL 3251 and A.parasiticus CMI 89717 grew better and produced more toxin on cake ("Rührkuchen") with aw 0.92 than on cake with lower water activity.

[Aflatoxin M1 in milk and milk products. A comparison of some determination procedures]

Usual TLC-methods for the determination of Aflatoxin M1 in milk and milk products sometimes do not separate interfering substances with similar optical and chemical properties from Aflatoxin M1, thus leading to considerably incorrect results. Even after an additional clean-up on polystyrene column the solutions contain so many compounds that the identification of Aflatoxin M1 is difficult. The resolving power of HPLC yield pure frations, which may be determined by their MS and UV spectra.

Production and characterization of antibody against aflatoxin M1

Antibody against aflatoxin M1 was obtained after immunization of rabbits with bovine serum albumin-afla M1 oxime conjugate. The antibody has greatest binding efficiency for afla M1, and was less efficient for afla B1. Cross-reaction of antibody with aflatoxin Q1, aflatoxicol, and aflatoxin B2a was weak. Aflatoxin B2, G1, and G2 and afla B1-guanine adducts showed almost no cross-reaction with the antibody. The sensitivity of the binding assay for aflatoxin M1 detection is in the range of 1-10 ng per assay. Detailed methods for the preparation of the conjugate, production of immune serum, and methods for antibody determination are described.

[Introduction in mycotoxin problems (author's transl)]

In Part I the occurrence of mycotoxins is discussed in general terms with emphasis on how they originate in the food, taking full account of presence as secondary contaminants. Further discussions emphasize the occurrence of aflatoxin in foods with a detailed table containing 106 references. Finally, the discussion goes into the factors which influence the formation of mycotoxins and the consequences for the consumer. Part II is concerned with problems in sampling foods with aflatoxin. Difficulties in sampling arise from the different levels of aflatoxins present and from their instability in foods. Based on proposals of different investigators, sample quantities of more than 1 kg are recommended. Regulatory agencies expect concrete plans for statistical evaluation similar to those used for determination of salmonellae. It is particularly important that a solution should be found for the sampling of packaged foods so that a fair and reliable control is possible.

[Harmlessness to human health of the mold cultures used in cheesemaking]

Mould cultures are used for the manufacture of soft and blue cheese. The report deals with the present stage of knowledge of the question of mycotoxin-producers in mould cultures used for cheesemaking. The PR-toxin was isolated repeatedly from Penicillium roqueforti strains which were incubated on special media, but also from P. roqueforti cultures used for cheese manufacture. However, cheese ripening conditions do not favor the production of this toxin. Other catabolites from P. roqueforti such als roquefortine and isofumigaclavine have been found in cheese, but there is not much known about their toxic effect. No cancerogenic mycotoxins have been discovered in these types of cheese, except alfatoxin M1, which might however originate from contaminated milk. It must be concluded that the occurrence of tumors after feeding of a pure P. camemberti var. candidum culture is due to the effect of mycotoxins. On the other hand, further animal experiments with various mould culture stains used for cheesemaking have not confirmed these findings. On the basis of the literature consulted it may be said that the use of mould cultures for cheesemaking does not involve any risk for human health, that means it is toxicologically harmless.

[Sampling of cheese for aflatoxins (author's transl)]

Due to the greatly differing incidence of molds on cheese and thus the extremely differing amounts of aflatoxin reliable sampling in cheeses is difficult, particularly if only one semi-hard of hard cheese is available. Experiments were undertaken now to sample--hopefully without losses and suitable for commercial application--in order to be able to ascertain the possible aflatoxin content of a cheese. Based on storage results with artificially contaminated Provolone and Tilsit cheeses as a pretest determination of aflatoxins in scrapings from a 100 cm2 surface are is recommended. At high levels (20-30 microgram/kg) the sampling of several borings at different locations on the cheese is necessary. The aflatoxin content on the surface is not constant, a fact which can be explained by biochemical reactions and by migration of aflatoxins into deeper layers. Washing of cheeses seems not to be of any significant influence on the aflatoxin-content.