Occurrence of Aspergillus section Flavi and aflatoxins in Brazilian rice: From field to market

Abstract

The guarantee of the high quality of rice is of utmost importance because any toxic contaminant may affect consumer health, especially in countries such as Brazil where rice is part of the daily diet. A total of 187 rice samples, from field, processing and market from two different production systems, wetland from the state of Rio Grande do Sul, dryland, from the state of Maranhão and market samples from the state of São Paulo, were analyzed for fungi belonging to Aspergillus section Flavi and the presence of aflatoxins. Twenty-three soil samples from wetland and dryland were also analyzed. A total of 383 Aspergillus section Flavi strains were isolated from rice and soil samples. Using a polyphasic approach, with phenotypic (morphology and extrolite profiles) and molecular data (beta-tubulin gene sequences), five species were identified: A. flavus, A. caelatus, A. novoparasiticus, A. arachidicola and A. pseudocaelatus. This is the first report of these last three species from rice and rice plantation soil. Only seven (17%) of the A. flavus isolates produced type B aflatoxins, but 95% produced kojic acid and 69% cyclopiazonic acid. Less than 14% of the rice samples were contaminated with aflatoxins, but two of the market samples were well above the maximum tolerable limit (5μg/kg), established by the Brazilian National Health Surveillance Agency.

Pre‐ and Postharvest Strategies to Minimize Mycotoxin Contamination in the Rice Food Chain

“…Recent reports show that the infection of rice grains with A . flavus is a chronic problem in some regions and that consumers in these countries can be at risk because of high level exposure to aflatoxins (AFs) (Hussaini, Timothy, Olufunmilayo, Ezekiel, & Godwin, ; Katsurayama et al., ; Reddy et al., ). In tropical Asia, for example, rice is predominately contaminated with AFs as a result of a pre‐ and postharvest colonization of the grains with A .…”

“…In tropical countries where temperature is high throughout the year and frequently paired with high relative humidity (RH), Aspergillus flavus is the main fungus in this regard. Recent reports show that the infection of rice grains with A. flavus is a chronic problem in some regions and that consumers in these countries can be at risk because of high level exposure to aflatoxins (AFs) (Hussaini, Timothy, Olufunmilayo, Ezekiel, & Godwin, 2007;Katsurayama et al, 2018;Reddy et al, 2009a). In tropical Asia, for example, rice is predominately contaminated with AFs as a result of a pre-and postharvest colonization of the grains with A. flavus (Reddy et al, 2009a;Sales & Yoshizawa, 2005;Toteja et al, 2006).…”

“…In processed rice products, the co-occurrence has not been well documented, and most of the information is related to the co-occurrence of mycotoxins in red yeast rice (RYR) (Samsudin & Abdullah, 2013). Nevertheless, this is a rather susceptible product for AF occurrence and high levels have been detected (Katsurayama et al, 2018).…”

Aspergillus species and mycotoxins: occurrence and importance in major food commodities

“…In a recent study carried out on Brazilian rice, five species were distinguished from Aspergillus section Flavi: A. flavus, A. caelatus, A. novoparasiticus, A. arachidicola and A. pseudocaelatus [35]. This was the first report of these last three species from rice and rice plantation soil.…”

Predominant Mycotoxins, Pathogenesis, Control Measures, and Detection Methods in Fermented Pastes

“…Crops contaminated by different Aspergillus species demonstrate various levels of risk regarding the presence of aflatoxins in final fermented pastes. For example, small grains like soybean and wheat do not have affinity with Aspergillus species, and aflatoxins can only be produced during untimely drying or storage at high-temperatures after harvest [27]. Crops such as peanuts and maize have higher risk levels than others, because A. flavus and A. parasiticus are commensal with these crops [28].…”