Effects of food preservatives on Alternaria alternata growth and tenuazonic acid production.

The effects of different organic acids on Alternaria alternata growth and tenuazonic acid production (TeA) were evaluated. Both TeA pure toxin solution and TeA production in solid medium were considered. Sodium benzoate, potassium sorbate and sodium propionate, all preservatives commonly used by food industry in Argentina, were tested. TeA was stable as pure toxin solution when was treated with the salts of organic acids used. A differential effect was observed when the preservatives were evaluated in relation to A. alternata growth and TeA production in solid medium. Levels above 10 mg/kg of sodium benzoate and potassium sorbate produced a total inhibition of fungal development and toxin biosynthesis. Sodium propionate produced a 59% decrease in A. alternata growth and total inhibition of TeA production only at the highest concentration of preservatives used.

Effect of heat treatments on stability of altemariol, alternariol monomethyl ether and tenuazonic acid in sunflower flour.

A study was carried out to evaluate the effect of heat treatment on the stability of alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) in sunflower flour and the effectiveness of this treatment by a biological assay in rats. The concentrations of AOH and AME remained constant during heating at 100°C for up to 90 minutes while TeA concentration decreased with time to 50% after 90 minutes. The most effective treatment in reducing AOH and AME levels was heating at 121°C for 60 minutes. Histopathological evaluation in the biological assay in rats fed withAlternaria toxins showed marked atrophy and fusion of villi in the intestines and liver cell damage; these lesions were less severe in rats fed heat-treated sunflower flour in line with the reduced toxin content. However, a lower weight gain and a noticeable renal damage in rats were produced when they fed decontaminated flour.

Fungal and aflatoxin contamination of medicinal herbs.

Since the consumption of aromatic and medicinal herbs has been increasing in the last years, the Argentinian Health Authorities are concerned to control the quality and security of them. Fungal and aflatoxin contamination are two parameters to be taken into account, to ensure the harmlessness of the phytomedicinal products. In 81 different samples, grouped in end products (EP), raw material (RM) and at harvest (SH), fungal flora (enumeration and identification) as well as naturalAspergillus flavus and aflatoxin occurrence were investigated. In all samples fungal counts fulfilled the international general recommendation limits (maximum 10(5) cfu/g). Predominant flora was made up by xerophilic species ofAspergillus(100%), byPeniciIlium (< 50%) and in less percentage byFusarium (5.6%). Among the Aspergilli, A.flavus was present in all the three groups of samples. Using a TLC method, 47% of A. flavus isolates were toxinogenic, producing aflatoxin B1 and B2. In herbs, 4.7% of RM samples were naturally contaminated with aflatoxins B1 and B2. Considering the carcinogenic activity of aflatoxins it is essential to regulate them in the raw material (vegetal drug).

Occurrence of deoxynivalenol and Fusarium graminearum in Argentinian wheat.

During the 1993 harvest period there was a high incidence of Fusarium head blight in wheat in Argentina. Fusarium species that produce trichothecenes in wheat have been reported in several countries including Argentina. Several studies have shown that F. graminerarum and deoxynivalenol (DON) were the main contaminants detected in wheat and by-products in Argentina. The objective of this study was to evaluate the occurrence of Fusarium spp. and DON contamination in wheat from Córdoba, Argentina during the 1993/94 harvest season. F. graminearum was the main Fusarium species isolated. From 40 samples analysed, 80% showed DON contamination. The levels of DON found ranged between 300 and 4500 micrograms/kg. There was good correlation between F. graminearum and DON contamination. Only five samples showed levels of DON higher than those established in the guidelines in Canada and the USA for food and feedstuffs.

Evaluation of Alternaria and its mycotoxins during ensiling of sunflower seeds.

Sunflower (Heliantus annuus) is an important crop in the economy of Argentina due to its high production and demand from domestic and export markets. The aim of this study was to evaluate the presence of Alternaria species and its mycotoxins in ensiled sunflower seeds. The sampling was carried out in three periods: at the beginning of ensiling, on the second month and finally on the fourth month. The mycological analysis was made with disinfected seeds, cultured on Dichloran-Rose Bengal-Chloramphenicol (DRBC) and Dichloran-Chloramphenicol-Malt Extract-Agar (DCMA). The toxins were analyzed by thin layer chromatography (TLC). A alternata was the main fungal species isolated. The incidence of Alternaria species and the levels of alternariol and tenuazonic acid decreased as the time of ensiling increased. Alternariol monomethyl ether was detected in two samples from the second and third sampling periods.

Sanitary factors and mycotoxin contamination in the argentinian wheat crop 1993/94.

In Argentina, due to climatic conditions, Fusarium head blight (FHB) caused by Fusarium graminearum, affected the 1993/94 wheat crop. To evaluate the severity of this disease, samples of wheat where gathered from four zones of the wheat area. Sanitary conditions and mycotoxin contamination were determined. One zone (IIN) was intensely affected by FHB with 90% of samples in grade III (bad quality). No samples were grade I (good quality). The other zones were less affected falling into grade I or II (moderate quality). In all samples tested F. graminearum was the most prevalent species singly or in combination with others. Zone II N, with a DON mean level of I1.26 ppm, did not fulfil aceptability limits, whereas zones IIS, III and IV with overall means of 2.12, 1.57 and 1.0 ppm, respectively, did. Statistical analysis showed a close relation between percentage FHB and DON contamination (r:-0.71, p<0.01) in infected samples.

[Relation between the production of deoxynivalenol and zearalenone and the mycelial growth of Fusarium graminearum on solid natural substrates]. / Relación entre la producción de deoxinivalenol y zearalenona y el crecimiento micelial de Fusarium graminearum en sustratos naturales sólidos.

A toxicogenic strain of Fusarium graminearum which produces DON and ZEA was cultivated on natural solid substrates (wheat, polished rice and hulled rice) under different environmental conditions. The production of both toxins and mycelium growth (in terms of glucosamine) were evaluated to establish the relation between the production of DON and ZEA and the different mycelium growth on the substrates mentioned above. Polished rice was the substrate on which most production of both toxins was obtained. Comparing the three substrates studied, the highest quantities of DON were obtained at a temperature of 27 degrees C during incubation period, being indifferent to the presence of light except in the case of hulled rice. Whereas for ZEA the best conditions in wheat and polished rice were medium temperatures (17 degrees-21 degrees C respectively) and darkness. While in hulled rice the ideal conditions for the production of both toxins were temperature of 27 degrees C and the presence of light. Concerning the mycelium growth, this was very scarce when cultivated in hulled rice, increasing in polished rice and being largest in wheat. The increase or reduction of the mycelium growth in the different substrates was not proportional to the increase or decrease of the production of both toxins. Therefore, production of DON and ZEA could be subjected to the nature of the substrate and environmental conditions, more than the rate of development of Fusarium graminearum in cereal grains.

Aflatoxins in sunflower seeds: influence of Alternaria alternata on aflatoxin production by Aspergillus parasiticus.

The aim of the present work was to determine the influence of Alternaria alternata upon aflatoxin production by Aspergillus parasiticus. A mixture of spores of both strains was inoculated in sunflower seeds at 0.90 aw and incubated for 42 days at 28 degrees C +/- 1. The cultures were observed and analyzed every 7 days to determine the infection level of the seeds and the production of aflatoxins. Results showed that when the seeds were inoculated only with Aspergillus parasiticus, 100% were infected from the 7th day. When Aspergillus parasiticus and Alternaria alternata were simultaneously inoculated the infection level of the seeds was 100% for Aspergillus parasiticus following 7 days of inoculation and 0% for Alternaria alternata. After the 14th day of inoculation there was no significant difference in the infection percentage of both strains (approximately 80% of each one). As far as toxin production is concerned a remarkable decrease was observed when seeds were inoculated with both strains simultaneously. In accordance to the results, Alternaria alternata would not compete with Aspergillus parasiticus in colonization of seeds but would either degrade the aflatoxins by Aspergillus parasiticus or compete for aflatoxin biosynthesis precursors. Alternaria alternata could also secrete some substance that specifically inhibits aflatoxin synthesis.

Incidence of aflatoxin, zearalenone, and deoxynivalenol on corn in Argentina.

The study of the incidence of aflatoxins, zearalenone, and deoxynivalenol was the aim of this work. This investigation was carried out upon recently harvested corn samples collected in the Departamento of Rio Cuarto, Province of Córdoba, Argentina. 150 samples of corn were analized to investigate aflatoxins B1, G1, and zearalenone contamination. Out of these 150 samples 58 were selected and deoxynivalenol was examined.The incidence value for aflatoxin B1 was of 3.3% (5 samples), aflatoxin G1 1.3 % (2 samples), and zearalenone 6 % (9 samples).The analysis of the 58 samples showed that 24% of them were contaminated with deoxynivalenol.

Aflatoxins in sunflower seeds: effect of zinc in aflatoxin production by two strains of Aspergillus parasiticus.

Growth and aflatoxin production by Aspergillus parasiticus NRRL 2999 and Aspergillus parasiticus RC 12 were studied both in sunflower seed and a synthetic culture medium (with and without zinc enrichment). On a synthetic culture medium the strains behaved in different ways according to the zinc concentration. In sunflower seed medium the influence of zinc was not so evident. Thus the results show that the influence of zinc is not the same for different strains and substrates.

[Susceptibility of hybrid varieties of sunflower to the formation of aflatoxins]. / Susceptibilidad de variedades de híbridos de girasol a la formación de aflatoxinas.

Aflatoxin is produced on sunflower varieties and hybrids. Since it has been demonstrated that sunflower seed are a natural substrate for aflatoxin production in our country, 4 varieties and 11 hybrids were studied to determine aflatoxin susceptibility. The samples were analyzed after 7 days of inoculation with A. parasiticus NRRL 2999. The varieties and hybrids showed different capacity of toxin production being the varieties more susceptible than the hybrids.

Susceptibilidad de variedades de híbridos de girasol a la formación de aflatoxinas. / [Susceptibility of hybrid varieties of sunflower to the formation of aflatoxins]

Aflatoxin is produced on sunflower varieties and hybrids. Since it has been demonstrated that sunflower seed are a natural substrate for aflatoxin production in our country, 4 varieties and 11 hybrids were studied to determine aflatoxin susceptibility. The samples were analyzed after 7 days of inoculation with A. parasiticus NRRL 2999. The varieties and hybrids showed different capacity of toxin production being the varieties more susceptible than the hybrids.

[Determination of aflatoxins and toxicogenic fungi in mixed feed for poultry]. / Determinación de aflatoxinas y hongos toxicogénicos en alimentos balanceados para aves.

The presence of aflatoxins was determined in 155 samples of chicken feeds, as well as their fungal contamination. Aflatoxins were detected in 3 of the analized samples; one of them contained 1620 micrograms/kg, a highly dangerous amount for chickens. The amount found in the remaining 2 samples was 30 micrograms/kg. A study of toxigenic fungus showed a prevalence of 69.3% of Aspergillus flovus: 72.4% of this percentage corresponded to aflatoxins producing strains. The prevalence of Aspergillus ocraceus was 18.6%; ten per cent of it corresponded to ochratoxin A producing strains. Chicken feeds are an adequate substratum for the formation of aflatoxins; this was demonstrated by raising the humidity contents of initially negative samples, which contained toxigenic Aspergillus flavus spores. The danger of storing chicken feeds under certain humidity and temperature conditions was demonstrated.

Determinación de aflatoxinas y hongos toxicogénicos en alimentos balanceados para aves / [Determination of aflatoxins and toxicogenic fungi in mixed feed for poultry]

The presence of aflatoxins was determined in 155 samples of chicken feeds, as well as their fungal contamination. Aflatoxins were detected in 3 of the analized samples; one of them contained 1620 micrograms/kg, a highly dangerous amount for chickens. The amount found in the remaining 2 samples was 30 micrograms/kg. A study of toxigenic fungus showed a prevalence of 69.3

of this percentage corresponded to aflatoxins producing strains. The prevalence of Aspergillus ocraceus was 18.6

; ten per cent of it corresponded to ochratoxin A producing strains. Chicken feeds are an adequate substratum for the formation of aflatoxins; this was demonstrated by raising the humidity contents of initially negative samples, which contained toxigenic Aspergillus flavus spores. The danger of storing chicken feeds under certain humidity and temperature conditions was demonstrated.

Determinación de aflatoxinas y hongos toxicogénicos en alimentos balanceados para aves. / [Determination of aflatoxins and toxicogenic fungi in mixed feed for poultry]

The presence of aflatoxins was determined in 155 samples of chicken feeds, as well as their fungal contamination. Aflatoxins were detected in 3 of the analized samples; one of them contained 1620 micrograms/kg, a highly dangerous amount for chickens. The amount found in the remaining 2 samples was 30 micrograms/kg. A study of toxigenic fungus showed a prevalence of 69.3

of Aspergillus flovus: 72.4

of this percentage corresponded to aflatoxins producing strains. The prevalence of Aspergillus ocraceus was 18.6

; ten per cent of it corresponded to ochratoxin A producing strains. Chicken feeds are an adequate substratum for the formation of aflatoxins; this was demonstrated by raising the humidity contents of initially negative samples, which contained toxigenic Aspergillus flavus spores. The danger of storing chicken feeds under certain humidity and temperature conditions was demonstrated.