Aflatoxin degradation in rice

Aflatoxins, secondary metabolites produced by the molds Aspergilllus flavus and A. parasiticus, are estimated to affect upwards of 25% of the world’s global food supply. For Low and Middle-Income Countries like Kenya, a combination of trade, economic, and health challenges related to aflatoxin contamination present a serious threat to food and national security. One option for reducing aflatoxin risks in countries like Kenya is deploying small-scale, reprocessing technologies that degrade aflatoxin in contaminated food products. One potential technology for reprocessing is small-scale extrusion (60 pph) like the TechnoChem Mini-Extruder™. First, to understand the extent of aflatoxin contamination in Kenyan maize, two field work trials were conducted in Uasin Gishu County, Kenya. Aflatoxin levels from each sample were analyzed and compared to a variety of agro-economic variables (e.g. farm size) using a stepwise multiple linear regression. Upon analysis, only 5% of maize samples collected during field work tested positive for unsafe levels of aflatoxin ( >10 ppb). Thus, the resulting regression model is highly biased towards predicting low aflatoxin levels. Such bias makes any inferences to predict high aflatoxin levels in maize largely inconclusive. The inherent heterogeneity of aflatoxin and the history of wide-spread contamination in Kenya further supports the conclusion that more studies are needed to understand the true extent of aflatoxin contamination in Uasin Gishu maize. Second, to test the effectiveness of small-scale extrusion on aflatoxin degradation in maize, contaminated samples were processed at varying motor frequencies (15, 38, and 50 hz) and moisture contents (35, 40, 45 %wb). Moisture content is significant (p-value < 0.05) in aflatoxin degradation. Total aflatoxin degradation varied between 11 and 83% depending on processing conditions. Maximum degradation occurred at 40 %wb product moisture with a residence time of 265.1 s and an effective shear rate of 56.5 1/s. Thermal degradation is considered negligible due to low temperature increases. Consequently, all degradation is attributed to shear forces inside the extruder. Shear rates were approximated using the Harper model with moisture content and residence time being the most significant factors affecting shear effects on aflatoxin degradation. Although significant aflatoxin degradation occurred in the extruder, further studies are necessary to understand the role of processing parameters on aflatoxin degradation before small-scale extrusion can be confirmed as a viable reprocessing technology.

The degradation of aflatoxins (AF) by Aspergillus niger or Aspergillus flavus (AF non-producing strain) from peanuts naturally contaminated and rice artificially contaminated with AF were studied.Conidia of the two strains were separately inoculated into contaminated peanut and rice cultures. The cultures were analyzed at 5, 10, 15, 20 and 25 days after inoculation. At the same time, AF-contaminated peanut and rice cultures without conidia were analyzed as controls. In the culture with A. niger, loss of AF B1, B2, G1 and G2 was faster and more extensive than in the culture with AF non-producing A. flavus. After 5 days, low levels of AF remained in the culture with A. niger (80-90% was lost), and no AF were detected after 10 to 15 days. In contrast, after 15 days, the loss of AF in the culture with AF non-producing A. flavus ranged from about 40 to 90%, and low levels of AF were still detected after 25 days.The degradation of AF by these two Aspergilli was confirmed by means of the chicken embryo test.

Fungal infection in agricultural grains is a global problem, particularly if it is accompanied by mycotoxin production. In this study, the degradation of mycotoxins by laccase and manganese peroxidase was investigated. Aspergillus flavus, Aspergillus fumigatus, and Fusarium graminearum were recorded in infected maize grains. Aflatoxin B1 (AF B1) was detected (from 3.38 to 2.60 ppm) on the infected samples by fungi compared to other detected aflatoxins. Trichothecene (T-2) toxin and deoxynivalenol (DON) were recorded with concentrations ranging from 0.464 to 0.184 ppm and 0.370 to 0.214 ppm, respectively. The addition of laccase and manganese peroxidase to the inoculated medium with A. flavus and F. graminearum individually degraded the produced AF B1, B2, G1, G2, T-2 toxin, and DON from 5.0, 1.33, 0.76, 0.61, 0.63, and 0.38 ppm to 2.77, 0.66, 0.37, 0.15, 0.45, and 0.38 ppm using laccase, to 3.08, 1.25, 0.61, 0.39, 0.55, and 0.36 ppm using manganese peroxidase. The computational technique (docking) demonstrated the laccase and manganese peroxidase activities on aflatoxin and DON degradation. Consequently, the results suggested that laccase (PDB ID: 1HFU) and manganese peroxidase (PDB ID: 1MNP) promise innovative activity toward aflatoxin degradation, while 1HFU has more effect than 1MNP on DON degradation.

This study evaluated the efficiency of ozone for the degradation of aflatoxins in pistachio kernels and ground pistachios. Pistachios were contaminated with known concentrations of aflatoxin (AF) B1, B2, G1 and G2. Pistachio samples were exposed to gaseous ozone in a chamber at 5.0, 7.0 and 9.0 mg L−1 ozone concentrations for 140 and 420 min at 20 °C and 70% RH. Aflatoxin degradation was determined by high performance liquid chromatography (HPLC). The efficiency of ozone for aflatoxin degradation in pistachios increased with increasing exposure time and ozone concentration. The results indicated that AFB1 and total aflatoxins could be reduced by 23 and 24%, respectively, when pistachio kernels were ozonated at 9.0 mg L−1 ozone concentration for 420 min. Only a 5% reduction in AFB1 and total aflatoxin levels could be achieved for ground pistachios under the same conditions. No significant changes occurred in pH, color, moisture content and free fatty acid values of pistachio kernels and ground pistachios. Fatty acid compositions of pistachios did not change significantly after the ozonation treatments. No significant changes were found between sweetness, rancidity, flavor, appearance and overall palatability of ozonated and non‐ozonated pistachio kernels. Significant changes were observed in the organoleptic properties of ground pistachios, except rancidity, after 5.0 mg L−1 ozone treatment for 140 min. Ozonation was found to be more effective for degrading aflatoxins in pistachio kernels than ground pistachios. Copyright © 2006 Society of Chemical Industry

Effect of roasting on degradation of Aflatoxins in contaminated pistachio nuts

Aflatoxins (AF) are highly toxic secondary metabolites produced by various species of Aspergillus, posing significant health risks to humans and animals. The four most prominent types are aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), and aflatoxin G2 (AFG2). These mycotoxins are prevalent in various environments, including water sources and food products. Among these mycotoxins, AFB1 is recognized as the most toxic, mutagenic, and carcinogenic to humans. Consequently, most efforts to mitigate the impact of AF have been focused on AFB1, with photocatalysis emerging as a promising solution. Recent research has demonstrated that using semiconductor photocatalysis, particularly titanium dioxide (TiO2), combined with UV–visible irradiation significantly enhances the efficiency of AF degradation. TiO2 is noted for its high activity under UV irradiation, non-toxicity, and excellent long-term stability, making it a favorable choice for photocatalytic applications. Furthermore, TiO2 combined with visible light has demonstrated the ability to reduce AF contamination in food products. This article summarizes the working conditions and degradation rates achieved, as well as the advantages, limitations, and areas of opportunity of these methodologies for the degradation of AF and preventing their production, thereby enhancing food and water safety.

High moisture content, relative humidity, temperature and environment rich in oxygen (O 2 ) are the main factors for tree nuts to get infected by fungi and so aflatoxins (AFLs) contaminated. During storage and commercialization dry Brazil nuts packs need to maintain their safety and quality. Modified atmospheres in storage (macro-environment) and packaging (micro-environment) have been used to prolong food shelf life by reducing O 2 concentration with inhibitory gases or, more recently, by adding O 2 absorber pads. This work reports the application of O 2 atmosphere reducing methods on stored shelled Brazil nut packs aiming fungi and AFL degradation as well as hygienic conditions improvements. The methods applied were: (a) ozone - O 3 , (b) carbon dioxide - CO 2 and (c) O 2 absorber pads with and without vacuum. Nuts were submitted to microbiological tests (fungi, aflatoxigenic strains, yeast and bacteria), moisture content and AFLs analysis. From all O 2 reducing atmosphere evaluated, the best performance was obtained with O 3 . A reduction on fungi growth (1.8 x 10 4 cfu.g -1 to 2.6 x 10 cfu.g -1 ) and yeast destruction after the first month of storage were registered. Also O 3 was the only nut treatment that was able to degrade AFLs. None of the spiked (AFLs: 15 ppb) nut samples O 3 treated had AFLs detected up to the LOQ of the method (0.36 μg.kg -1 for AFB 1 +AFB 2 +AFG 1 +AFG 2 ) i.e., much lower than the allowed by the European Union regulation (MRL: 4 and 2 ppb for total and AFB 1 , respectively), thus producing safer nuts. All other treatments stabilized and/or inhibited microorganisms growth. Add CO 2 and O 2 pads played an important role on nut quality. Further study will be carried out in order to adjust O 3 concentration and application conditions for longer period of storage.

Aflatoxins (AFs) are fungal metabolites that ubiquitously contaminate many common food crops and contribute to major foodborne diseases in humans and animals. Known chemical strategies have used strong acids and bases to remove contaminating AF, but these methods often lead to undesired ecological waste issues downstream. In this study, the application of weaker acidic and alkaline conditions to removes two types of AFs, AFB1 and AFG2, is investigated. The results showed that an environment buffered at a pH of 9 reduced AFB1 and AFG2 by more than 50 and 95%, respectively, within 24 h, while acidic conditions did not influence AF levels. The AF degradation was shown to occur through lactone ring opening, a known cause of AF toxicity. Further analysis also provided a putative structure of the AFG2 degradation byproduct. The results confirmed that incubation at a pH of 9 reduced the genotoxicity of AFB1 and found that it was a successful strategy for removing both AFs from artificially contaminated cornmeal. The findings indicated that a weakly alkaline environment had the potential to adequately detoxify AF-contaminated food or feed without the need to apply stronger or harsher basic conditions.

Aflatoxins (AFs) have great side effects on human, animals and crops. It causes severe illness to both human and animals, and play a major role in economic loss. Biological decontamination seems to be attractive. The present investigation aimed to found new and safe microorganisms able to degrade AFs and inhibit its producing fungi. Forty three bacterial isolates were isolated from different cultivated soils and animal feces. All isolates were screened for their ability to degrade AFs using Thin Layer Chromatography (TLC). Nine bacterial isolates were able to degrade AFs using TLC and HPLC. HPLC results showed that AFs degradation ratio higher than 90% occurred by 3 bacterial cultures. The identification of the highly degrading isolate CaG6 (with 98.1% degradation ratio) was established by using 16S rRNA gene sequencing as Bacillus cereus. Then sequence was acquiesced to GenBank in accession number MG 751322 with 99% similarity to Bacillus cereus. Bacterial isolates CaG7 and IsW1 (with 94.6, 90.7% degradation ratio, respectively) has been identified by MALDI-TOF MS using the VITEK MS system (bioMerieux) as Brevibacillus sp1 and Brevibacillus sp2. Results showed that cell cultures (viable cells) were more effective in the degradation of AFs than cell free supernatant (CFS), while ppt exhibited no degradation. The three bacteria not only reduced AFs but it could also inhibit Aspergillus flavus NRRL 3145 with inhibition zone ≥20mm after incubation for 96h at 28°C. The AFs degradation by B. cereus, Brevibacillus sp1 and Brevibacillus sp2 enhanced by addition Mn+2 ions to the liquid media.

In this study, we investigated the occurrence of aflatoxins (AFs) and ochratoxin A (OTA) in meju and soybean paste produced in South Korea. Samples were collected from three regions divided on the basis of climate in South Korea. A total of 100 meju samples were analyzed over 3 years (2012–2015), and 45 soybean paste samples were analyzed in 2016. Mycotoxins were extracted with an immunoaffinity column method and quantified by high-performance liquid chromatography. AFs were detected in 10 of meju (10%) and 11 of soybean paste samples (24.4%) with concentrations of 0.2–48.3 μg/kg and 0.88–16.17 μg/kg, respectively. OTA was detected in 50 of meju (50%) and 22 of soybean paste samples (48.9%) with concentrations of 0.1–193.2 μg/kg and 0.88–26.29 μg/kg, respectively. Mycotoxin contamination in meju was more common in the central region than in the southern areas. Thus, more mycotoxins were produced in the central region owing to less fungal competition in meju during fermentation inside households. We also found that about 91% of AFs and 73% of OTA in meju were degraded after the production of soybean paste and soy sauce. Even after degradation of AFs and OTA, the levels of AFB1 and OTA were 0.5 µg/kg and 7.5 µg/kg in soy sauce and 11.9 µg/kg and 190.4 µg/kg in soybean paste, respectively. Thus, our results suggest the need for constant monitoring of meju and soybean paste for AFs and OTA.

Evaluation and detoxification of aflatoxins in ground and tree nuts using food grade organic acids

The degradation of aflatoxins using nonpathogenic microbes and their enzymes is emerging as a safe and economical alternative to chemical and physical methods for the detoxification of aflatoxins in food and feeds. Many bacteria and fungi have been identified as aflatoxin degraders. This review is focused on the chemical identification of microbial degradation products and their degradation pathways. The microbial degradations of aflatoxins are initiated by oxidation, hydroxylation, reduction, or elimination reactions mostly catalyzed by various enzymes belonging to the classes of laccase, reductases, and peroxidases. The resulting products with lesser chemical stability further undergo various reactions to form low molecular weight products. Studies on the chemical and biological nature of degraded products of aflatoxins are necessary to ensure the safety of the decontamination process. This review indicated the need for an integrated approach including decontamination studies using culture media and food matrices, proper identification and toxicity profiling of degraded products of aflatoxins, and interactions of microbes and the degradation products with food matrices for developing practical and effective microbial detoxification process.

Aflatoxins degradation and quality evaluation in naturally contaminated rice by dielectric barrier discharge cold plasma

Aflatoxins (AF) are real public health hazards due to their potential carcinogenic, teratogenic, and mutagenic activities toward humans and a wide range of animal species (Allameh and Razzaghi-Abyaneh 2001; Bennett and Klich 2003). They are a major group of polyketide mycotoxins produced mainly by specific members of Aspergillus section Flavi. AF-producing fungi, especially Aspergillus flavus and Aspergillus parasiticus, have worldwide distribution and they are able to contaminate a wide range of substrates including cereal grains, oilseeds, and tree nuts under favorable conditions of temperature and relative humidity (Bennett and Klich 2003). The importance of these toxins, especially aflatoxin B1 (AFB1), the most potent natural hepatocarcinogen, led to significant advances in the field of secondary metabolism, from biochemistry to genetics and control strategies. Genetic studies of AF biosynthesis in the major producers, A. flavus and A. parasiticus, led to the identification of at least 25 clustered genes within a 70 kb DNA region responsible for the enzymatic conversions in the AF biosynthetic pathway (Yu et al. 2005). The role of regulatory elements, nutritional and environmental factors and fungal development in AF formation has been studied with special focus on micro-array technology using expressed sequence tags of A. flavus and A. parasiticus (Yu et al. 2004). Despite these promising data, concerns over AF contamination concerns are still far from being solved, due to our low level of understanding about signal transduction pathways underlying toxin formation by producing fungi, and about the dynamics of toxigenic fungus-host plant interactions during the infection process. Since the discovery of AF in the early 1960s, a large number of chemicals have been screened with the aim of finding AF biosynthesis inhibitors (Zaika and Buchanan 1987; Razzaghi-Abyaneh et al. 2006a).

Aflatoxin B1 (AFB1) is a hazardous component that can seriously threaten the public health. Terxine is a component used in traditional soup and found in the western mountainous regions of Iran. Several microorganisms have been reported to bind or degrade aflatoxins (AFs) in foods and feeds. This research aimed to investigate the effect of Terxine fermentation byLactobacillus plantarumstrains AF1 and LU5 on AFB1. Fermentation was carried out, and pH, lactic acid and AFB1 amount and microbial count were further determined. In addition, the kinetic experimental data of AFB1 by L. plantarumAF1 and LU5 (obtained at 37°C) were fitted to the zero-order, first-order and parabolic diffusion models. According to the coefficient of determination (R2) and root mean square of errors (RMSE), the zero-order model best described AF degradation. The growth of Lactobacillus strains was increased by the rise in the fermentation time; in this regard, the number of L. plantarum AF1 increased from 4.2 to 5.1 log cfu/g and that of L. plantarum LU5 increased from 4.1 to 5.2 log cfu/g in the first 8h, reaching 7.2 and 7.4 log cfu/g in the next 8h, respectively. The results also showed that the amount of lactic acid increased whereas the pH value decreased during the 24h fermentation. Both microorganisms reduced the amount of AFB1 while L. plantarum AF1 was more effective. Therefore, L. plantarumstrains AF1 and LU5 can be effectively used to reduce AFB1 in fermented foods.