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Natural occurrence of toxigenic fungi and mycotoxins in rice bran
P Jayaraman1, I Kalyanasundaram
1Department of Botany, University of Madras, India.
Abstract:
Thirty four samples of rice bran, of which 9 were from raw (untreated) rice (RR) and 25 from parboiled rice (PbR) were collected from commercial rice mills in and around Madras and analysed for storage mycoflora and mycotoxins. Fungi of the Aspergillus flavus group were present in 29 of the 34 samples (8 from RR and 21 from PbR) in quantities ranging from less than 1-432 thousand propagules/g, though not always as the dominant mycoflora. Fungal numbers were usually higher in RR than in PbR samples. Five of the 9 RR samples and 6 of the 25 PbR samples were positive for aflatoxins. Among 29 isolates of A. flavus obtained from the bran samples, 16 isolates -6 from RR bran and 10 from PbR bran - were found to be toxigenic in vitro. Some isolates of A. candidus also seemed to produce aflatoxin and other fluorescent substances.
Insights
Rice bran mycoflora analysis revealed Aspergillus flavus contamination in most samples. A significant portion of Aspergillus flavus isolates from both raw (RR) and parboiled rice (PbR) bran were toxigenic, indicating a mycotoxin risk.
Area of Science:
- Food Science
- Mycology
- Agricultural Science
Background:
- Rice bran is a significant byproduct of rice milling.
- Storage mycoflora and mycotoxins in rice bran pose food safety risks.
- Parboiling may influence fungal contamination and mycotoxin production.
Purpose of the Study:
- To analyze the mycoflora and mycotoxin contamination in raw (RR) and parboiled rice (PbR) bran.
- To identify the prevalence and toxigenicity of Aspergillus flavus group fungi.
- To assess potential differences in fungal contamination between RR and PbR.
Main Methods:
- Collection of 34 rice bran samples (9 RR, 25 PbR) from commercial mills.
- Analysis of storage mycoflora and mycotoxin presence.
- Isolation and in vitro toxigenicity testing of Aspergillus flavus.
Main Results:
- Aspergillus flavus group fungi were found in 29 of 34 samples (8 RR, 21 PbR).
- Fungal numbers were generally higher in RR than PbR samples.
- Aflatoxins were detected in 5/9 RR and 6/25 PbR samples; 16/29 A. flavus isolates were toxigenic.
Conclusions:
- Rice bran, particularly raw rice bran, is susceptible to Aspergillus flavus contamination.
- Toxigenic Aspergillus flavus isolates were prevalent in both raw and parboiled rice bran.
- Further investigation into aflatoxin production by Aspergillus candidus is warranted.