Mycotoxin Contamination In Rice Research Articles

Public health risk due to aflatoxin and fumonisin contamination in rice in the Mekong Delta, Vietnam

Mycotoxin contamination in rice can lead to a health risk for consumers. In this study, the health risk among different age groups of Vietnamese population in the Mekong Delta, Vietnam was evaluated through rice consumption. Total aflatoxins (AFs) and fumonisins (FBs) in raw rice samples (n = 50) were analyzed using an ELISA method. A survey (n = 155) was used to collect data on rice consumption and consumer practices for the evaluation of mycotoxin exposure. Results showed that the frequency of AFs and FBs contamination was 60 and 74% with the average concentrations in raw rice ranging from 1.88–4.00 ng/g and 227–290 ng/g from the lower bound (LB) to the upper bound (UB), respectively. The average AFs exposure due to rice consumption was estimated from 0.81 to 2.44 ng/kg bw/day at scenarios LB – UB with the medium bound (MB) of 2.10, 1.60, 1.92 and 1.23 ng/kg bw/day for children, adolescents, adults and elderly, respectively. These values ranged from 343 to 724 ng/kg bw/day with respect to FBs (scenarios LB - UB), which are below the provisional maximum tolerable daily intakes (PMTDI) value (2000 ng/kg bw/day). The margin of exposure (MoE) to AFs ranged from 160 to 1585,179-2669,149–2175 and 206–3480 for children, adolescent, adults and elderly, respectively from UB - LB, indicating a high health risk for this carcinogenic hazard since the values are so lower than 10,000 (safe limit). However, for FBs, MoE value ranged from 105 to 575 (UB-LB) for all groups, which are higher compared to 100 (safe limit), indicating no risk for public health. The mean cancer risk due to estimated AFs exposure at LB - UB was 0.05–0.13 cases/year/100,000 individuals with MB of 0.08–0.13 cases/year/100,000 people for all four age groups. This study provides new insights into probabilistic risk assessment and potential health impact of mycotoxins in rice in the Mekong Delta, Vietnam.

Distribution of mycotoxin-producing fungi across major rice production areas of China

Mycotoxin contamination of rice (Oryza sativa), especially that from aflatoxins (AFTs), is one of the greatest chemical hazards to humans and animals. However, few studies have investigated the relationships between fungal communities and mycotoxin contamination of rice grains. In the present study, we collected rice grain samples from 10 provinces in the northeastern (NE), southeastern (SE), and southwestern (SW) regions of China, encompassing the major rice-producing areas of China. The Fungal diversities of rice grains were significantly different among different regions and significantly higher in the SE and SW regions compared to the NE region. Geographic location was highly associated with fungal community alpha and beta diversity differences. Environmental variables determined the distribution of fungal communities, with winter mean temperature (WMT), mean annual precipitation (MAP), harvest mean wind speed (HMW), and grain moisture (GM) being the most important factor shaping the fungal communities, and the higher HMW could significantly reduce the abundance of aflatoxigenic fungi and aflatoxins. The Aspergillus flavus and A. parasiticus were defined as the major AFT-producing fungal taxa observed in the SE and SW region communities. The NE region exhibited a lower risk of AFT contamination due to its much lower prevalence of toxigenic fungi. Furthermore, keystone taxa of co-occurrence network analyses indicated that species belonging to the genera Clonostachys, Cryptococcus, Hannaella, Leptosphaerulina, Leptosphaeria, Phaeosphaeria, Sarocladium, Sphaerulina, Wallemia and Ustilaginoidea exhibited abundances that were negatively correlated with AFT-producing fungal abundances and could potentially inhibit the growth of AFT-producing fungi. The results provide potentially important data for the strategic guidance of local rice grains storage in order to better control toxin contamination and improve grain quality.

Mycotoxin Contamination of Consumed Rice in Iran: A Review

: Mycotoxin contamination of rice has been introduced as a big challenge for public health in developing countries in numerous studies. Rice consumption is also considered the main source of secondary metabolites in Iran. Given the diversity of climatic conditions in this region as well as unsuitable storage conditions, including high temperature and humidity, rice can be extremely contaminated via various fungi. The current study is a review of the occurrence of mycotoxins in rice in Iran. In this regard, some investigations had revealed that rice could be contaminated by mycotoxins such as aflatoxins (AFTs) (B1, B2, G1, and G2), deoxynivalenol (DON), fumonisin (FM) (B1 and B2), ochratoxin A (OTA), T-2 toxin, and zearalenone (ZEN). Moreover, the amount of mycotoxins in rice was reported in varying ranges in different provinces and regions and normally less than Iranian maximum tolerated dose (MTD). Given the importance of rice in the Iranian diet, it was finally recommended to screen consumed rice to find about fungal contaminations and mycotoxins.

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

Rice is part of many people's diet around the world, being the main energy source in some regions. Although fewer reports exist on the occurrence of mycotoxins in rice compared to other cereals, fungal contamination and the associated production of toxic metabolites, even at lower occurrence levels compared to other crops, are of concern because of the high consumption of rice in many countries. Due to the diversity of fungi that may contaminate the rice food chain, the co-occurrence of mycotoxins is frequent. Specific strategies to overcome these problems may be applied at the preharvest part of the crop chain, while assuring good practices at harvest and postharvest stages, since different fungi may find suitable conditions to grow at the various stages of the production chain. Therefore, the aim of this review is to present the state-of-the-art knowledge on such strategies in an integrated way, from the field to the final products, to reduce mycotoxin contamination in rice.

Mycotoxin concentrations in rice from three climatic locations in Africa as affected by grain quality, production site, and storage duration.

Information on the mycotoxin contamination of rice in Africa is limited although the risk of contamination is high. In this study, domestic milled rice processed by actors using suboptimal methods was purchased and total fumonisin (FUM), zearalenone, and aflatoxin concentrations determined at 0, 90, and 180 days after storage. Three different climatic locations, Cotonou (Benin) in the Guinea savanna, Yaoundé (Cameroon) in the Tropical forest, and N'diaye (Senegal) in the Sahel, were selected as storage sites. Subsets of the samples collected from Glazoue (Benin), Ndop (Cameroon), and Dagana (Senegal) were stored in plastic woven bags under room conditions in the respective sites with or without calcium oxide (burnt scallop shell—BSS, 0.1% w/w) treatment. Multivariance analysis showed that FUM concentration was positively influenced by the duration of storage only while zearalenone concentration was negatively influenced by relative humidity and head rice but positively by impurities. Zearalenone concentration was also influenced by sample collection/storage location, processing type, and duration of storage. Aflatoxin concentration was influenced negatively by storage room temperature and head rice but positively by impurities and chalky grains. In addition, aflatoxin concentration was influenced by collection/storage location and processing type. BSS treatment followed by storage for 6 months had no effect on the concentration of the three assessed mycotoxins. Strategies to reduce the risk of mycotoxin contamination in study sites will include the improvement of physical rice quality through better pre‐ and postharvest practices and proper packaging of both treated rice and untreated rice in hermetic systems before marketing and storage.

Isolation and Identification of Fungal Species from the Insect Pest Tribolium castaneum in Rice Processing Complexes in Korea.

The red flour beetle, Tribolium castaneum, is one of the most common and economically important pests of stored cereal products worldwide. Furthermore, these beetles can act as vectors for several fungal post-harvest diseases. In this study, we collected T. castaneum from 49 rice processing complexes (RPCs) nationwide during 2016–2017 and identified contaminating fungal species on the surface of the beetles. Five beetles from each region were placed on potato dextrose agar media or Fusarium selection media after wet processing with 100% relative humidity at 27°C for one week. A total of 142 fungal isolates were thus collected. By sequence analysis of the internal transcribed spacer region, 23 fungal genera including one unidentified taxon were found to be associated with T. castaneum. The genus Aspergillus spp. (28.9%) was the most frequently present, followed by Cladosporium spp. (12.0%), Hyphopichia burtonii (9.2%), Penicillium spp. (8.5%), Mucor spp. (6.3%), Rhizopus spp. (5.6%), Cephaliophora spp. (3.5%), Alternaria alternata (2.8%) and Monascus sp. (2.8%). Less commonly identified were genera Fusarium, Nigrospora, Beauveria, Chaetomium, Coprinellus, Irpex, Lichtheimia, Trichoderma, Byssochlamys, Cochliobolus, Cunninghamella, Mortierella, Polyporales, Rhizomucor and Talaromyces. Among the isolates, two known mycotoxin-producing fungi, Aspergillus flavus and Fusarium spp. were also identified. This result is consistent with previous studies that surveyed fungal and mycotoxin contamination in rice from RPCs. Our study indicates that the storage pest, T. castaneum, would play an important role in spreading fungal contaminants and consequently increasing mycotoxin contamination in stored rice.

Multiple Mycotoxins in Rice: Occurrence and Health Risk Assessment in Children and Adults of Punjab, Pakistan.

Mycotoxin contamination in rice can create a health risk for the consumers. In this study, the measurement of 23 mycotoxins in rice samples (n = 180) was performed using a validated LC–MS/MS method. A food frequency questionnaire was used to get rice consumption data for the assessment of mycotoxin dietary exposure, before calculating the health risk in adults and children of north and south regions of the Pakistani Punjab province. The prevalence of aflatoxin B1 (56%), aflatoxin B2 (48%), nivalenol (28%), diacetoxyscirpenol (23%), fumonisin B1 (42%), zearalenone (15%), HT-2 toxin (10%), deoxynivalenol (8%), and ochratoxin A (6%) was estimated in samples with a mean concentration range between 0.61 and 22.98 µg/kg. Aflatoxin degradation by traditional Pakistani cooking recipes was evaluated and observed to be 41–63%. The dietary exposure to aflatoxins exceeded the tolerable daily intake at all levels, and ochratoxin A and zearalenone posed health risk at high contamination and high consumption levels. The margin of aflatoxin B1 exposure ranged between 10 and 69 in adults and 10 and 62 in children. The mean cancer risk by aflatoxin B1 exposure was 0.070 (adults) and 0.071 (children) cases/year/100,000 people in South Punjab population, and 0.122 (adults) and 0.127 (children) cases/year/100,000 people in North Punjab population. This study will provide new insights for the planning and management of mycotoxins in Pakistan.

Mycotoxin Contamination of Rice in China

Mycotoxin contamination in rice is generally lower than in other cereals such as corn or wheat. However, over 65% of the population in China consumes rice as a staple food. Due to the diversity of the climate across China, the southern region is characterized by high temperatures and humidities, especially in rainy season. Such conditions are optimal for the growth of fungi. The accumulative and transferrable characteristics of fungi mycotoxins pose a great potential threat as confirmed by high incidences of liver cancer in the Yangtze delta region. Major mycotoxins identified in China are aflatoxins and ochratoxin A, as well as fumonisins. The contents of aflatoxin B1 (AFB1 ) in rice are varied among different provinces and regions and generally less than 5 μg/kg. Although high incidences of positive aflatoxins samples have widely been detected, few samples were detected as exceeding the national's maximum residue limit (10 μg/kg). Limited information is available on risk assessment of human health hazards of mycotoxins in rice, children should be paid more attention to due to their having the highest mycotoxins exposure level, although the risks are generally at low levels from rice. Mycotoxins are mainly distributed in the outer layer of the paddy rice (also called rough rice, referring to whole rice grain with the hulls), and the AFB1 content in bran is 8.4 times greater than that in brown rice (hulled rice). Further investigation should focus on isolation and identification of mycotoxins-producing fungal strains, especially unknown mycotoxigenic fungal strains determination. Infection resistant rice breeding of mycotoxigenic fungal species may be a fundamental approach to guaranteeing rice safety in China.

INCIDENCE, PHYLOGENY AND MYCOTOXIGENIC POTENTIALS OF FUNGI ISOLATED FROM RICE IN NIGER STATE, NIGERIA

The study reports on the natural occurrence of fungi in 21 samples of field (10), stored (6) and marketed (5) rice (Oryza sativa L.) collected from Niger State, Nigeria. Fungal isolates were primarily identified based on morphological characteristics, while representative isolates were characterized genetically. An evolutionary tree was constructed from the resulting sequences of the isolated fungi. The toxigenic potentials of some of the isolated fungi were also determined. A total of 357 fungal isolates of nine genera including Aspergillus, Fusarium, Sarocladium, Acremonium, Curvularia Botryosphaeria, Penicillium Alternaria and Ascomycota in decreasing order of predominance were identified. The most frequent fungal contaminants of the rice samples were A. flavus, A. fumigates, A. niger, A. parasiticus and F. proliferatum. All strains of A. flavus (aflatoxins B1 and B2), A. parasiticus (aflatoxins B1, B2, G1 and G2), A. ochraceus (ochratoxin A), F. proliferatum and F. verticillioides (fumonisins B1 and B2) tested, were excellent producers of their respective mycotoxins. Patulin was produced by A. terreus, whereas deoxynivalenol, zearalenone and T-2 toxin were produced by F. chlamydosporum and other Fusarium spp. The increased prevalence of toxigenic fungi in rice, a highly consumed food grain in Nigeria, poses serious health concerns to the general public. PRACTICAL APPLICATIONS This study investigated the natural fungal occurrence of rice grown in Nigeria using polymerase chain reaction-based techniques as well as the toxigenic potentials of some of the identified fungi. The resultant fungal profile of rice, gene sequences of the fungi detected in the survey, which were deposited in the GenBank and the constructed evolutionary tree, will serve as reference data for the incidence of fungal species in rice and will help to evaluate the safety of Nigerian rice. It could be used in developing and predicting the degree of mycotoxin contamination in rice from Nigeria for effective mycotoxin control. The toxigenic fungi acquired from the work will be excellent microbial sources for production of mycotoxin standards namely aflatoxins BI, B2, G1 and G2, ochratoxin A and fumonisin B1 and B2.

Preparation of an in-house reference material containing fumonisins in Thai rice and matrix extension of the analytical method for Japanese rice.

Mycotoxin contamination in rice is less reported, compared to that in wheat or maize, however, some Fusarium fungi occasionally infect rice in the paddy field. Fumonisins are mycotoxins mainly produced by Fusarium verticillioides, which often ruins maize. Rice adherent fungus Gibberella fujikuroi is taxonomically near to F. verticillioides, and there are sporadic reports of fumonisin contamination in rice from Asia, Europe and the United States. Therefore, there exists the potential risk of fumonisin contamination in rice as well as the need for the validated analytical method for fumonisins in rice. Although both natural and spiked reference materials are available for some Fusarium mycotoxins in matrices of wheat and maize, there are no reference materials for Fusarium mycotoxins in rice. In this study, we have developed a method for the preparation of a reference material containing fumonisins in Thai rice. A ShakeMaster grinding machine was used for the preparation of a mixed material of blank Thai rice and F. verticillioides-infected Thai rice. The homogeneity of the mixed material was confirmed by one-way analysis of variance, which led this material to serve as an in-house reference material. Using this reference material, several procedures to extract fumonisins from Thai rice were compared. Accordingly, we proved the applicability of an effective extraction procedure for the determination of fumonisins in Japanese rice.

Mycotoxins in rice

Mycotoxin contamination in rice is usually lower as in wheat or corn. However, there are some reports that rice has been contaminated with mycotoxins such as aflatoxin B 1, B 2, G 1, G 2 (AFS), citrinin, deoxynivalenol (DON), fumonisin B 1, B 2, B 3 (FMS), fusarenon-X (Fus.-X), nivalenol (NIV), ochratoxin A (OTA), sterigmatocystin (STE), and zearalenone. Rice in Japan is preserved in warehouses where moisture content and temperature are regulated. Therefore, mycotoxin contamination from post harvest fungal growth occurs very seldom. Trichothecenes, aflatoxins, and STE in rice were recently analyzed in our laboratory. In 1998, a typhoon struck before rice harvesting in Japan, and the unpolished rice was found to be stained brown. Samples were collected and analyzed for the presence of trichothecenes. Mycotoxins DON, Fus.-X, and NIV were detected and confirmed with GC-MS. The quantity of trichothecenes was determined using GC-ECD. STE is a carcinogenic mycotoxin produced by Aspergillus versicolor and some other fungi. STE contamination of rice was studied in our laboratory since 1973. GC-MS, LC-MS, LC-MS/MS, and LC-UV methods for STE determination were examined, giving good results for the LC-UV method using a photo diode array detector. Different techniques for the extraction of STE from rice were also studied. Finally, brown rice was ground, and the ground rice was extracted with acetonitrile-water. An Autoprep MF-A 1000 column was used to clean up AFS and STE. The cleaned-up extract was analyzed with HPLC-UV. Forty-eight brown rice samples were analyzed, and none of them were contaminated with STE. These rice samples were also analyzed for AFS and FMS, and none of the samples were contaminated. The Ministry of Agriculture, Forestry and Fisheries in Japan is making the appropriate Institutes develop analytical methods for mycotoxins and survey mycotoxin contamination on rice as well as wheat, corn, and some other cereals.