Aflatoxin pollution of consumed rice in Iran

Introduction: Aflatoxins are one of the most important categories of mycotoxins produced as secondary metabolites by three species of Aspergillus in a wide variety of foods and feeds. AFTs (B1, B2, G1, and G2) are considered as potent teratogens, mutagens, hepatotoxins, and immunotoxins. AFTs are known as the most potent and typical toxins in contaminated grains which have been the locus of research studies in most countries. According to the national standards in Iran, the maximum residue limit (MRL) for AFTs and AFB1 in rice have been respectively reported by 30 and 5 ng/g ppb. Methods: The search included PubMed-Medline, Scopus, Web of Science and Google Scholar databases by up to September 20, 2017. All relevant results published were chosen for final review. Results: Faraji et al. found that all rice samples had AFTs and AFB1 in 8.3% of the samples was higher than ISIRI. AFB1 was reported as the highest amount of contamination in the study by Karajibani, but AFG was not detected. No imported rice had AFTs higher than standard which were consistent with the findings by Mazaheri in which the mean of AFB1 was lower than Iranian ISIRI. Feizi et al. reported that 68.9% of the samples had AFB1 at levels greater than 0.2 ng/ g-1. The mean AFB1 concentration in rice from the city of Mashhad was 0.72 mg/ g-1. Discussion: It had been reported that AFT contamination could be often associated with drought and temperature and some synthetic or natural protectants could even help in inhibiting aflatoxigenic fungi and AFT formation during storage. The summer heat and high humidity could also lead to mold growth and AFT production; so, it seemed that the amount of AFB1 in white and yellow rice samples in the summer was more than that in the autumn and the winter. The rice grain might also contain some enzymes or chemicals inhibiting AFT production. Numerous methods have been proposed and utilized to detoxificate AFT in foodstuff including citric, sodium hypochlorite and ozone. Fumigation process is typically utilized for imported products, which can decrease AFT contamination rates. The results of the study by Karajibani in this domain suggested that AFTs had been reduced in imported rice using these methods. It was noted that the most significant approach to control the amount of AFTs in rice was to control contamination in the field; however, this was very difficult as it could be primarily affected by climatic conditions such as humidity and temperature. Nevertheless, it had been reported that the highest concentrations of AFTs were associated with post-harvest growth of Aspergillus molds on poorly stored foodstuff. Currently, this mycotoxin is not assumed as a risk and even a serious public health issue, though routine monitoring such as food quality control measurement is required. It should be noted that rice is not considered as a conductive product of Aspergillius growth and AFT contamination within normal conditions; however, it can be susceptible to AFT contamination once exposed to heavy rain or high moisture.

Keywords:

Aflatoxin , Rice , Risk Assessment