The aim of this study was to determine the multi-mycotoxin occurrence in cereal and oilseed products most consumed in Côte d'Ivoire. A total of 238 samples of rice (88 produced locally or imported), maize (79, cracked or flour) and peanut paste (71) were collected in the main markets of Abidjan, Bouaké and Korhogo. An UHPLC-MS/MS method allowed the analysis of 77 mycotoxins. All the peanut paste samples were contaminated by aflatoxin B1 (AFB1) with 99% exceeding the EU limits of 2 µg.kg-1 for AFB1 and 4 µg.kg-1 for total aflatoxins (AFT: B1+B2+G1+G2), and concentrations reaching up to 4535 µg.kg-1 (AFB1) and 8094 µg.kg-1 (AFT). Maize (96%) and rice (57%) samples were also contaminated by AFB1 with 58% and 24% respectively above the EU limits and maximum levels of 80 µg.kg-1 for maize and 14 µg.kg-1 for rice. Only 6% of the cereal samples (3 rice and one maize samples) had ochratoxin A content above the EU limit (3 µg.kg-1). Fumonisins and zearalenone were detected, respectively, in 91% and 8% of the maize samples, and in 18% and 5% of the rice samples but at levels below EU limits. Out of the 238 samples, 91% were contaminated with more than one mycotoxin including EU regulated mycotoxins and/or other mycotoxins mainly beauvericin (79% of the samples), equisetin (71%), aflatoxin M1 (45%), cyclopiazonic acid (32%), fumonisin B3 (29%), sterigmatocystin (24%), citrinin (18%), ochratoxin B (16%) and fusaric acid (15%). The peanut paste samples represented the highest risk to consumer health followed by maize and rice samples.
Several strains of a new aflatoxigenic species of Aspergillus, A. korhogoensis, were isolated in the course of a screening study involving species from section Flavi found contaminating peanuts (Arachis hypogaea) and peanut paste in the Côte d’Ivoire. Based on examination of four isolates, this new species is described using a polyphasic approach. A concatenated alignment comprised of nine genes (ITS, benA, cmdA, mcm7, amdS, rpb1, preB, ppgA, and preA) was subjected to phylogenetic analysis, and resulted in all four strains being inferred as a distinct clade. Characterization of mating type for each strain revealed A. korhogoensis as a heterothallic species, since three isolates exhibited a singular MAT1-1 locus and one isolate exhibited a singular MAT1-2 locus. Morphological and physiological characterizations were also performed based on their growth on various types of media. Their respective extrolite profiles were characterized using LC/HRMS, and showed that this new species is capable of producing B- and G-aflatoxins, aspergillic acid, cyclopiazonic acid, aflavarins, and asparasones, as well as other metabolites. Altogether, our results confirm the monophyly of A. korhogoensis, and strengthen its position in the A. flavus clade, as the sister taxon of A. parvisclerotigenus.
Fruit ripening is associated with many hydrolase activities involved in the softening of the fruit during the maturation. This study investigates the relationship between the loss of firmness along with the changes of sugar content and the enzymatic activities in Carica papaya L.var solo 8 during post-harvest storage. Three maturation stages (green immature: the fruit is entirely green, green mature: the fruit shows 1/32 yellow skin and fully mature: the fruit shows 1/8 yellow skin) have been selected and stored at 15, 22 and 28°C. The reduction of fruit firmness, total sugar contents, refractive index (% Brix) and enzymatic activities were measured. Low enzymatic activities (0.035 μmol/min/mg) were recorded in fruit harvested at the green immature stage with no significant (p≥0.05) effect on the softening while fruit harvested at the green mature and fully mature stages showed enzymatic activities 7 times as high as those of the green immature stage. These high enzymatic activities were responsible for the loss of firmness of the fruit. Accordingly, papayas at the green mature and fully mature stages displayed higher maxima of sugar content (4.8 g/100 g at 28°C at day 12, and 10.2 g/100 g at 22°C at day 8, respectively) at higher temperatures. Meanwhile in green immature papayas, the maximum was only 4.3 g/100 g at 22°C and day 12 of storage. The results show that the loss of firmness of the papaya was highly related to the hydrolytic enzyme activities and the sweet taste to the presence of simple sugars such as galactose liberated from the polysaccharide complexes.
This study was conducted to assess the antibacterial and the antifungal activity of a polyhexamethylene guanidine hydrochloride (PHMGH)-based disinfectant and to determine if it could be used as a disinfectant for the treatment of cocoa beans. The activity of PHMGH was tested in vitro for efficacy against five reference strains of pathogenic bacteria and six strains of fungi isolated from cocoa beans. All the strains tested were sensitive to the disinfectant. The MICs reported were between 0.01 and 1.9 mg/ml and equal to the MBC or minimum fungicidal concentration (MFC) regardless of the strains of those microorganisms. The bacteria were more sensitive to PHMGH than were the fungi. Enterobacter cloacae was the most sensitive bacterium with a MIC and MBC of 0.01 mg/ml, whereas the genus Aspergillus was the least susceptible of the microorganisms tested, with a MIC and MFC from 1.0 to 1.9 mg/ml. The time required for the activity of PHMGH varies from 2 min for Enterobacter cloacae to 12 min for Aspergillus tamarii and generally increases with the MBC or the MFC. Through this in vitro study, the PHMGH has been proved to be bactericidal and fungicidal on the strains studied. Hence, it could probably serve as a fungicidal disinfectant for the treatment of cocoa beans after harvesting.
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