Virginia Fernández Pinto

Fungal spoilage of bottled mineral water

The occurrence of filamentous fungi together with bacteriological parameters was assessed in 126 samples of still bottled mineral water of eight different commercial brands in Argentina. In spoiled samples with visible mycelium growth, the most frequently isolated fungal species were Penicillium citrinum, P. glabrum, other Penicillium species, Cladosporium cladosporioides and Alternaria alternata. In unspoiled samples, the genera found were Penicillium, Cladosporium, Rhizopus, Aspergillus and Phoma. Only three of the 126 samples failed to meet the required microbiological standards because they were found to contain faecal streptococci.

Influence of water activity and temperature on the growth of Wallemia sebi: application of a predictive model

Germination and growth of Wallemia sebi were examined on media of a(w) adjusted with glycerol in the range of 0.96-0.77, at 25 degrees C and 30 degrees C. The effect of temperature on the germination time was significant except between 0.95 and 0.88 a(w). At low a(w) levels as well as above 0.95, the increase of temperature produced an increment in the germination time. The minimum a(w) for germination was also affected by temperature, being lower at 25 degrees C (0.80 a(w)) than at 30 degrees C (0.82 a(w)). Radial growth rates at 25 degrees C were higher than at 30 degrees C. The optimum a(w) value for growth of W. sebi was 0.94 at both temperatures. The minimum a(w) for growth was higher than minimum for germination and was also dependent on temperature (0.84 at 25 degrees C and 0.86 at 30 degrees C). An empirical mathematical model was fitted to the measured growth data, providing a good approach to the description of the effect of a(w) on the radial growth rate of W. sebi.

Effect of water activity and temperature on production of aflatoxin and cyclopiazonic acid by Aspergillus flavus in peanuts

It is well known that some isolates of Aspergillus flavus are able to produce cyclopiazonic acid (CPA) in addition to aflatoxins (Luk et al., 1977; Gallagher et al., 1978). CPA producing strains of A. flavus are frequently isolated from substrates such as peanuts (Blaney et al., 1989; Vaamonde et al., 2003) and maize (Resnik et al., 1996), indicating that this toxin could be a common metabolite and thus is likely to be present in some aflatoxin contaminated foods. Natural co-occurrence of both toxins has been detected in peanuts (Urano et al., 1992; Fernandez Pinto et al., 2001) and it has been hypothesized that the presence of both toxins in food and feeds may result in additive or synergistic effects. CPA is toxic to poultry and may have contributed to the outbreak of the classic “Turkey X” disease which killed about 100,000 turkey poults in England in 1960 (Cole, 1986). Some disease outbreaks of unknown aetiology observed in chickens in Argentina could also be attributed to the presence of CPA in peanut meal used as a raw material in poultry feeds, as strains of A. flavus capable of producing

Determinación de perfiles de producción de metabolitos secundarios característicos de especies del género "Alternaria" aisladas de tomate

BACKGROUND Many Alternaria species have been studied for their ability to produce bioactive secondary metabolites, such as tentoxin (TEN), some of which have toxic properties. The main food contaminant toxins are tenuazonic acid, alternariol (AOH), alternariol monomethyl ether (AME), altenuene, and altertoxins i, ii and iii. AIMS To determine the profiles of secondary metabolites characteristic of Alternaria strains isolated from tomato for their chemotaxonomic classification. METHODS The profiles of secondary metabolites were determined by HPLC MS. RESULTS The Alternaria isolates obtained from spoiled tomatoes belong, according to their morphological characteristics, to the species groups Alternaria alternata, Alternaria tenuissima and Alternaria arborescens, with A. tenuissima being the most frequent. The most frequent profiles of secondary metabolites belonging to the species groups A. alternata (AOH, AME, TEN), A. tenuissima (AOH, AME, TEN, tenuazonic acid) and A. arborescens (AOH, AME, TEN, tenuazonic acid) were determined, with some isolates of the latter being able to synthesize AAL toxins. CONCLUSIONS Secondary metabolite profiles are a useful tool for the differentiation of small spored Alternaria isolates not easily identifiable by their morphological characteristics.

Detection and Determination of Alternaria Mycotoxins in Fruits and Vegetables

Publisher Summary Species of Alternaria are known to produce a great number of secondary metabolites; however, only seven major toxins belonging to three different structural classes are known as possible food contaminants with a potential toxicological risk. The genus Alternaria includes both plant pathogenic and saprophytic species that damage crops in the field or cause post-harvest decay of fruits and vegetables. Alternaria spp. are the most common fungal species invading tomatoes and are important pathogens of various pome and stone fruits, citrus fruits, and other fruits. During their development in the host tissues, species of Alternaria are also known to produce a great number of secondary metabolites. Only seven major mycotoxins belonging to three different structural classes are known as possible food contaminants with a potential toxicological risk.

Plant Extracts as Natural Antifungals: Alternative Strategies for Mold Control in Foods

Because of their ability to grow in almost all food products, molds can generate off-flavors and spoilage, and can also produce mycotoxins. A wide range of chemical fungicides have been added to extend the shelf life of foods. However, there is a problem with the effective use of these chemicals in areas where the fungi have developed resistance. To overcome this problem, higher concentrations of these chemicals are used, but this increases the risk of a high level of toxic residues in the product. Plants may be a source of antifungals since they have had to synthesize compounds to resist infections by fungi present in their environment. Thus, there has been growing interest in the possible use of plant extracts as natural antifungals, which are less damaging to human health and the environment. Hurdle technology which involves simultaneous multiple preservation approaches has generally met with success in controlling fungal pathogens and maintaining food quality during storage. A combination of preservation treatments allows the required level of protection to be achieved.