Microbiological quality, fungal diversity and aflatoxins contamination in carob flour (Prosopis flexuosa).

Carob flour is obtained from pods of some species of Prosopis, leguminous trees that abound in many desert habitats worldwide. Currently, this product is available in healthy food stores in several countries, including Argentina, as a nontraditional meal of growing interest with multiple applications for the preparation of puddings, biscuits and snacks, among others. The objective of the present study was to evaluate the microbial quality of carob flour on basis of the presence of deteriorative and pathogenic microorganisms. Fungal diversity of the mycobiota was also studied with a special interest in toxigenic fungi. Eighteen samples of carob flour (Prosopis flexuosa) were analysed. Standard plate count of aerobic mesophilic bacteria showed levels of contamination ranging from <102 (estimative) to 6.8 × 105 CFU/g; total coliforms from <102 (estimative) to 4.7 × 105 CFU/g; moulds and yeasts from 2.1 × 102 to 8.1 × 104. In all samples, the absence of Salmonella sp. was verified in 25 g and counts of Bacillus cereus less than 102 were observed. These results indicate that from the safety point of view the carob flour studied does not have a significant microbial load. Regarding to fungal contamination, Aspergillus and Penicillium were the genera more diverse in species and were present in all the samples. Some of the species identified were potential mycotoxins producers. Among the most frequently detected species in the studied mycobiota were the Aspergillus of the Flavi section, well recognized as potential aflatoxin producers. The A. flavus species was one of the most widely distributed, since it was detected in almost all samples. A. parasiticus and A. arachidicola were found more sporadically. Aflatoxins analysis demonstrated that a high proportion of the samples were contaminated with aflatoxins in concentrations relatively low, ranging from 1.26 to 20.33 µg/kg of total aflatoxins. Type G aflatoxins are much less frequent contaminants than type B aflatoxins, which is consistent with the fact that A. parasiticus and A. arachidicola (producers of type B and G aflatoxins) were detected sporadically, while A. flavus, which produces aflatoxins B1 and B2, was present in a high number of samples. Results of the present work indicate that carob flour is susceptible to Aspergillus section Flavi and aflatoxin contamination and should be subjected to aflatoxin monitoring prior to marketing as required for other traditional crops.

Incidence of Deoxynivalenol in Wheat Flour in Argentina and GC-ECD Method Validation.

Background: Deoxynivalenol (DON) is a mycotoxin produced mainly by Fusarium graminearum. This fungus is the main plant pathogen associated with Fusarium Head Blight (FHB) wheat disease, causing significant economic losses and exposing human population to severe health risks. DON production changes widely among different years and areas and its effects are larger in years with abundant rainfall and high relative humidity. To date, Argentina has not established DON tolerance limits. Objective: To validate a method using GC with electron capture detector (GC-ECD) and to provide evidence of DON contamination in Argentinean commercial wheat flour. Results: A total of 34 different flour samples were analyzed obtaining 91.2% of incidence with a mean level of 243 µg/kg and a median level of 165 µg/kg. The method showed acceptable LOD (24 µg/kg) and LOQ (79 µg/kg), relative SD (RSD) of the intermediate precision (RSD = 5.98%), recovery (89.3%) and uncertainty (14%). Conclusions: The method was successfully validated according to the studied parameters. Incidence results for DON contamination are low and in accordance with previous studies for years with low FHB incidence in wheat.

Assessing the impact of organic and inorganic amendments on the toxicity and bioavailability of a metal-contaminated soil to the earthworm Eisenia andrei.

Metal-contaminated soil, from the El Arteal mining district (SE Spain), was remediated with organic (6% compost) and inorganic amendments (8% marble sludge) to reduce the mobility of metals and to modify its potential environmental impact. Different measures of metal bioavailability (chemical analysis; survival, growth, reproduction and bioaccumulation in the earthworm Eisenia andrei), were tested in order to evaluate the efficacy of organic and inorganic amendments as immobilizing agents in reducing metal (bio)availability in the contaminated soil. The inorganic amendment reduced water and CaCl2-extractable concentrations of Cd, Pb, and Zn, while the organic amendment increased these concentrations compared to the untreated soil. The inorganic treatment did not significantly reduce toxicity for the earthworm E. andrei after 28 days exposure. The organic amendment however, made the metal-contaminated soil more toxic to the earthworms, with all earthworms dying in undiluted soil and completely inhibiting reproduction at concentrations higher than 25%. This may be due to increased available metal concentrations and higher electrical conductivity in the compost-amended soil. No effects of organic and inorganic treatments on metal bioaccumulation in the earthworms were found and metal concentrations in the earthworms increased with increasing total soil concentrations.

Weathering of primary minerals and mobility of major elements in soils affected by an accidental spill of pyrite tailing.

In the present work, soil profiles were sampled 40 days and three years after an accidental pyrite tailing spill from the Aznalcóllar mine (S Spain) in order to figure out the effects of the acidic solution draining from the tailing. The composition of the acidic solution, the mineralogy, and the total and soluble content of the major elements were analysed at varying depths. The results show a weathering process of carbonates and of primary silicates. Calcium released is leached or reacts with the sulphate ions to form gypsum. Magnesium, aluminium and potassium tend to leach from the uppermost millimetres of the soil, accumulating where the pH>/=5.0; also the iron, probably forming more or less complex hydroxysulphates, precipitate in the upper 5 cm. The strong releasing of soluble salts increases the electrical conductivity, while the soluble potassium tends to decrease in the uppermost part of the soil due to the neoformation of jarosite. Iron is soluble only where the pH

Immobilization of heavy metals in polluted soils by the addition of zeolitic material synthesized from coal fly ash.

The use of zeolitic material synthesized from coal fly ash for the immobilization of pollutants in contaminated soils was investigated in experimental plots in the Guadiamar Valley (SW Spain). This area was affected by a pyrite slurry spill in April 1998. Although reclamation activities were completed in a few months, residual pyrite slurry mixed with soil accounted for relatively high leachable levels of trace elements such as Zn, Pb, As, Cu, Sb, Co, Tl and Cd. Phytoremediation strategies were adopted for the final recovery of the polluted soils. The immobilization of metals had previously been undertaken to avoid leaching processes and the consequent groundwater pollution. To this end, 1100 kg of high NaP1 (Na6[(AlO2)6(SiO2)10] .15H2O) zeolitic material was synthesized using fly ash from the Teruel power plant (NE Spain), in a 10 m3 reactor. This zeolitic material was manually applied using different doses (10000-25000 kg per hectare), into the 25 cm topsoil. Another plot (control) was maintained without zeolite. Sampling was carried out 1 and 2 years after the zeolite addition. The results show that the zeolitic material considerably decreases the leaching of Cd, Co, Cu, Ni, and Zn. The sorption of metals in soil clay minerals (illite) proved to be the main cause contributing to the immobilization of these pollutants. This sorption could be a consequence of the rise in pH from 3.3 to 7.6 owing to the alkalinity of the zeolitic material added (caused by traces of free lime in the fly ash, or residual NaOH from synthesis).