[Beta-glucan content and hydration properties of filamentous fungi].

The aim of this work was to isolate and identify filamentous fungi from several sources to study the dietary fiber and beta-glucan content. The fungal hydration properties such as water absorption and water holding capacities were also evaluated. Total dietary fiber of isolates exhibited a noticeable variability from 16 to 53% and the highest values were obtained for the genera Paecilomyces and Penicillium, a fact consistent with a higher content of beta-glucans (24 and 17%, respectively), higher than previously reported for Basidiomycetes and yeast. We observed a large decrease (75%) in the water holding capacity when the mycelia were dried. Isolates of filamentous fungi with greater water holding capacity also exhibited greater absorption capacity. Paecilomyces variotii and Penicillium nalgiovense had the best hydration properties. Our results contribute to the search for new unconventional ingredients providing a high protein and beta-glucans content. The addition of these dried mycelia could change the hydration properties in the food system.

Determination of hydration properties and thermal behavior of Paecilomyces variotii by differential scanning calorimetry.

Due to the structure and the composition of Paecilomyces variotii, the mycelia of this fungus could have potential applications as ingredients in wettable foods. For this use, drying could be employed, justifying the study of thermal behavior of P. variotii. The objectives of this work were to perform a study of thermal behavior of P. variotii isolates, to evaluate the hydration properties of these mycelia and to analyze the effect of different technological parameters on the latter properties. Wet cultures exhibited a wide endothermic transition, with mean values of peak temperature of 61 degrees C and denaturation enthalpy of4 J/g dry matter. Initial (50 degrees C) and final (80 degrees C) temperatures of the endothermic transition were used to dry the mycelia. Freeze-drying was also assayed. For all dried mycelia, a decrease in denaturation enthalpy between 40 and 50% was observed for drying at 50 degrees C and freeze-drying, and a drastic decrease of almost 100% for drying at 80 degrees C. According to the hydration properties, wet mycelia exhibited water holding capacity (WHC) value of 45 g water/g dry matter. Significant differences among dried mycelia, resulting WHC values in order: 50 degrees C > freeze-dried > 80 degrees C (p < 0.05) were revealed for each P. variotii strain. Fungi obtained by drying at 50 degrees C and by freeze-drying, showed a rapid water absorption (t(1/2) < 0.1 min). Ionic strength, pH and particle size of dried mycelia influenced the hydration properties.

Comparison of growth characteristics and roquefortin C production ofPenicillium roqueforti from blue-veined cheese.

The properties of 21 isolates ofPenicillium roqueforti from just as many commercial blue-veined cheeses, purchased from the Argentinean market (domestic and imported products) were comparatively examined. Isolates were investigated for their ability to grow at different temperatures, pH values and concentration of NaCl, as well as for their proteolytic and lipolytic activities, respectively. The potential of these strains to produce roquefortin in vitro, and the actual levels of roquefortin in 10 of these cheeses were analysed by TLC. All strains showed similar growth properties in aspects of salt concentration and pH-value of the medium, and all grew well at 10 °C. Only four strains showed proteolytic activity on casein agar, while all strains were lipolytic on trybutirin agar. After incubation at 25 °C for 16 days, all strains produced roquefortin in Yeast Extract Sucrose (25.6-426.7 µg/g) and in reconstituted (10%) sterile skim milk (26.9-488 µg/g). Roquefortin at >0.1 µg/g was also found in 9 out of 10 analysed samples of blue-veined cheeses (8 from Argentine, 1 from Spain), with a maximum value 3.6 µg/g. During the ripening process of blueveined cheese, production of roquefortin seems to be unavoidable. Care should be taken to select strains with low toxin production characteristics, to minimize potential health risks. Roquefortin C production byP. roqueforti in vitro was not correlated with roquefortin C levels found in cheese.

Mycotoxin production byAlternaria strains isolated from tomatoes affected by Blackmold in Argentina.

A survey on 28 samples of Blackmold" affected tomatoes cultivated in Argentina was made.A. alternata was the most frequently occurring species.A. tenuissima, A. longipes yUdocladium spp. were also isolated. All theAlternaria strains (25) were able to produce mycotoxins, including Alternariol, Alternariol Monomethyl Ether and Tenuazonic Acid, on autoclaved rice (at 25°C and 8°C) and in fresh surface disinfected tomatoes at 25°C.