Ernesto Moreno-Martínez

Effect of Sitophilus zeamais and Aspergillus chevalieri on the oxygen level in maize stored hermetically

Abstract Maize grain of hybrid AN 447 was: (a) infested with Sitophilus zeamais and infected with Aspergillus chevalieri ; (b) infested with S. zeamais ; (c) infected with A. chevalieri ; and (d) grain free of insects and fungus (control); the treatments were stored for 30 days at 26°C and 15% moisture content, under hermetic and non-hermetic conditions to monitor the oxygen concentration, insect mortality, insect offspring, grain germination, and fungal growth. The oxygen was depleted to 0% after 6–9 days in those treatments infested with insects, whereas the same oxygen level was reached after 24 days in grain with the storage fungus alone. The oxygen level gradually decreased to 8.4% after 30 days in the control treatment. All insects were dead after 6 days in grain with insects and fungus, and after 12 days in grain with insects alone. A low mortality rate (1.5–3.5%) occurred in equivalent treatments of the non-hermetic conditions. Because oxygen was depleted to 0% after 6 to 9 days in those treatments infested with insects, the weevils of both infested treatments under hermetic conditions produced a significantly lower number of offspring compared with those in the non-hermetic conditions. Under hermetic conditions in grain treated or not treated with fungicide, the storage fungus A. chevalieri invaded a low percentage of grains. A low percentage of fungal invasion occurred in grain stored under non-hermetic conditions also, where the decreased moisture content did not favor fungal growth. The grain germination of those treatments stored under hermetic conditions was significantly lower than those treatments stored under non-hermetic conditions. The insects were the main oxygen consumers, followed by the fungus and finally by the grain. Under sealed storage conditions, insects and fungus combined forces to deplete the oxygen of hermetically stored maize, creating an unfavorable atmosphere for their own survival.

Effect of Microwave Heating during Alkaline‐Cooking of Aflatoxin Contaminated Maize

UNLABELLED To evaluate the effectiveness of maize detoxification achieved with a modified tortilla-making process (MTMP), maize contaminated with aflatoxin B(1) (AFB(1)) and aflatoxin B(2) (AFB(2)) at levels of 22.46, 69.62, and 141.48 ng/g (AFB(1)+ AFB(2)) was processed into tortillas. Aflatoxin content was determined according to the 991.31 AOAC official method. Based on the results obtained with spiked samples (0.78 to 25 ng/g), the mean recovery was 92%, with a standard error of 1.2, and a coefficient variation value of 4.4%. The MTMP caused 68, 80, and an 84% decrease in aflatoxin content, respectively. Extract acidification (as occurs during digestion) prior to mycotoxin quantification caused some reformation of the aflatoxin structure in tortillas (up to 3%). According to these results, the MTMP seems to be safe for decontamination since a low percentage of the initial aflatoxin concentration can be reverted to the original fluorescent form upon acidification. PRACTICAL APPLICATION The potential presence of aflatoxins in maize destined for human consumption is a serious problem to the Mexican food supply, as these toxic compounds may persist during the traditional alkaline-process for tortilla elaboration. Consequently, new detoxification procedures are needed that eliminate or at least minimize the aflatoxin risk, through lowering aflatoxin concentration in maize-based products. Under these considerations, the use of MTMP is recommended, since it has definite advantages including non-production of wastewater and reduced energy/time consumption.

Role of lactone ring in structural, electronic, and reactivity properties of aflatoxin B1: a theoretical study.

This study involved quantum mechanical calculations to explain the chemical behavior of the lactone ring of aflatoxin B1, which is a carcinogenic hazardous compound. The aflatoxin B1 compound, produced by the fungi Aspergillum flavus, was studied with the B3LYP/6-311+G(d,p) method; its reactivity properties were accounted for by means of the calculated geometrical and electronic parameters. The results obtained indicate that the fused A, B, C, and D rings of aflatoxin adopt a continuous planar conformation. The carbon atom of the lactone group presents a highly electrophilic character, since the population analysis yields a high positive charge for this atom, whereas high negative charges were recorded for both oxygen sites of that group. Thus, in an acidic aqueous medium, the oxygen atoms could be protonated and the carbon site may suffer a nucleophilic attack by water. Accordingly, the OC−O bond length has been lengthened substantially. So it was demonstrated that the lactonic ring of aflatoxin B1 is hydrolyzed under acidic conditions by an acid-acyl bimolecular mechanisms, AAC2, suggesting the deletion of its carcinogenic properties.

Aflatoxins and Their Impact on Human and Animal Health: An Emerging Problem

Aspergillus is a fungus that essentially belongs to grains storage flora. It grows optimally at 25 °C with a minimum necessary water activity of 0.75. It starts to produce secondary metabolites at 10-12 oC, but the most toxic ones are produced at 25°C with a water activity of 0.95 (Hesseltine 1976). Those toxic secondary metabolites named aflatoxins (AF) is a group of mycotoxins produced by a large number of Aspergillus species, basically by three phylogenetically distinct sections. The main producers are A. flavus, and A. parasiticus, but it has been demonstrated that A. nomius, A. pseudotamarii, A. parvisclerotigenus, and A.bombycis of section Flavi, A. ochraceoroseus and A. rambellii from section Ochraceorosei and Emericella astellata and E. venezuelensis from Nidulatans section also generate aflatoxins (IARC 2002; Frisvad et. al., 2005). All of them contaminate a large fraction of the world’s food, including maize, rice, sorghum, barley, rye, wheat, peanut, groundnut, soya, cottonseed, and other derivative products made from these primary feedstuffs in low-income countries (Rizzi et al., 2003; Saleemullah et al., 2006; Strosnider et. al., 2006; Masoero et. al., 2007; Caloni, 2010). Although aflatoxins have been a problem throughout history, until 1960 they have been recognized as significant contaminants within agriculture, because in this year they were initially isolated and identified as the causative toxins in “Turkey-X-disease” after 100,000 turkeys died in England from an acute necrosis of the liver and hyperplasia of the bile duct after consuming groundnuts infected with Aspergillus flavus (Asao et. al., 1965; D’Mello, 1997; Strosnider et. al., 2006). Williams et al. estimated in 2004 that 4.5 billion of the world’s population is exposed to aflatoxins because they are also everywhere. Some essential factors that affect aflatoxin contamination include the climate of the region, the genotype of the crop planted, the soil type, the minimum and maximum daily temperatures, and the daily net evaporation (Strosnider et. al., 2006). Moreover, aflatoxin contamination is also promoted by stress or damage to the crop due to drought before harvest, the insect activity, a poor timing of harvest, the heavy rains during and after harvest, and an inadequate drying of the crop before storage. Levels of humidity, temperature, and aeration during storage are also important factors that are

Effect of citric acid supplemented diets on aflatoxin degradation, growth performance and serum parameters in broiler chickens #

RESUMEN Este estudio fue realizado para investigar los efectos del acido citrico (CA) sobre la degradacion de las aflatoxinas, el crecimiento y algunos componentes del suero sanguineo de pollos de engorda. 300 pollos de un dia de edad (Ross) fueron divididos aleatoriamente en cinco grupos con tres repeticiones de 20 pollos cada uno. Cuatro grupos recibieron la dieta suplementada con CA (6,25, 12,5, 25 y 50 g/kg), mientras que el otro sirvio como grupo control. La dieta fue preparada con base en las recomendaciones de la NRC, y el experimento fue terminado cuando las aves alcanzaron 28 dias de edad. Los resultados mostraron que las aflatoxinas en la dieta a una concentracion de 39 ng/g fueron degradadas (92%) por el procedimiento de acidificacion. En general, el peso vivo (LBW) fue ligeramente mayor en los animales alimentados con la adicion de CA; la dieta con la concentracion mas alta (50 g CA/kg) resulto en un aumento significativo en el LBW y una mejora en el indice de conversion. Sin embargo, a medida que se incremento la concentracion de CA, valores altos en la actividad de la enzima aspartato aminotransferasa fueron registrados. Por el contrario, el hematocrito, las proteinas totales y la albumina no fueron afectados por cualquier nivel de inclusion de CA en la dieta. De estos resultados, se concluye que el CA puede ser usado como un aditivo para degradar a las aflatoxinas en la dieta, asi como para promover el crecimiento en pollos de engorda jovenes.

Effect of lactic and citric acid on the stability of B-aflatoxins in extrusion-cooked sorghum

Aims:  To evaluate the effect of the extrusion‐cooking process with the addition of different acids concentration on the stability of B‐aflatoxins in sorghum.

Maize seed coatings and seedling sprayings with chitosan and hydrogen peroxide： their influence on some phenological and biochemical behaviors

ObjectiveTo evaluate the effect of chitosan (CH) and hydrogen peroxide (H2O2) seed coatings and seedling sprinklings on two different maize varieties by measuring their phenology, the H2O2 presence, the catalase (CAT) activity, and the protein quantity.MethodsSeven groups of ten seeds for each maize variety were treated with CH (2% (20 g/L) and 0.2% (2 g/L)) or H2O2 (8 mmol/L) by coating, sprinkling, or both. Germination and seedling growth were measured. One month after germination, the presence of H2O2 in seedlings in the coated seed treatments was evaluated. Protein content and CAT activity were determined under all treatments.ResultsH2O2 seed coating enhanced the germination rate and increased seedling and stem length in the quality protein maize (QPM) variety. Seedlings had a higher emergence velocity under this treatment in both varieties. CH and H2O2 sprinklings did not have an effect on seedling phenology. Exogenous application of H2O2 promoted an increase of endogenous H2O2. CH and H2O2 seedling sprinkling increased the protein content in both maize varieties, while there was no significant effect on the CAT activity of treated seeds and seedlings.ConclusionsCH and H2O2 enhance some phenological and biochemical features of maize depending on their method of application.

Cytotoxic and Genotoxic Evaluation of Tortillas Produced by Microwave Heating during Alkaline-Cooking of Aflatoxin-Contaminated Maize

UNLABELLED In vitro cytotoxicity and genotoxicity induction by aflatoxin B1 (AFB1) from maize (ME) and tortillas (TE) produced by microwave nixtamalization were investigated in monkey kidney (Vero cells) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the induction of lipid peroxidation, the oxidative damage by means of glutathione (GSH) depletion, and the Salmonella-microsomal screening system (Ames test). Our results showed that, at higher concentrations, both ME and TE extracts that contained varying amounts of aflatoxin caused a considerable decrease in Vero cell viability (up to 37%) after 4 h of exposure. Aflatoxins from ME induced greater oxidative damage by enhancing lipid peroxidation (up to 6.05 ± 0.14 μmol/mg protein) as compared to TE; however, TE also induced significant malondialdehyde formation in particular at the higher aflatoxin concentration tested (up to 2.7 ± 0.19 μmol/mg protein). The decrease in GSH level was also more pronounced in ME as compared to TE. Moreover, the Ames test results indicated that the mutagenic activity of TE was greatly reduced compared with that of ME based on his(-) → his(+) reversions in the Salmonella TA100 strain. According to these results, it is concluded that the microwave nixtamalization procedure reduced aflatoxins and their in vitro toxicity and mutagenic activity. PRACTICAL APPLICATION In Mexico, aflatoxins are often found in maize destined for the tortilla industry; consequently, tortilla consumption invariably leads to an important intake of intact and/or modified aflatoxin molecules caused by the thermal-alkaline treatment used during production. Therefore, it is of the highest importance to check whether such intake has the potential to lead to higher risk for adverse human health effects. In view of these considerations, in vitro tests may thus be useful for predicting the potential cytotoxicity and genotoxicity of tortillas produced for human consumption using aflatoxin-contaminated maize.

Novel Methods for Preventing and Controlling Aflatoxins in Food: A Worldwide Daily Challenge

Talking about Aflatoxins is not a new issue. Aflatoxins are a big problem that day by day turns more important due to their implication in crop production, food quality and human and animal health. Aflatoxins are also everywhere because those toxic secondary metabo‐ lites are mycotoxins produced by a large number of Aspergillus species, being A. flavus, and A. parasiticus the main producers; nevertheless, species like A. nomius, A. pseudotamarii, A. parvisclerotigenus, A.bombycis, A. ochraceoroseus, A. rambellii, Emericella astellata and E. venezue‐ lensis are aflatoxin generators too [1,2]. Since those toxins have been recognized as a signifi‐ cant worldwide problem in 1960 (because of being isolated and identified as the causative toxins in “Turkey-X-disease” after 100,000 turkeys died in England from liver acute necrosis and bile duct hyperplasia after consuming groundnuts infected with Aspergillus flavus) [3-5], researchers have studied lots of ways to fight against this threat; however, after more than a half century, aflatoxins are still a big problem that has not been easy to deal with, because humans are not able to manipulate essential factors that affect aflatoxin contamination like the region weather, the crop genotype, the soil type, the minimum and maximum daily tem‐ peratures and the daily net evaporation [5].

Protección contra estrés biótico inducida por quitosán en plántulas de maíz (Zea mays L.)

espanolEl maiz (Zea mays L.) es un cultivo importante en Mexico, que es a menudo afectado por la presencia de hongos patogenos. El objetivo de este estudio fue determinar el efecto protector del quitosan en plantulas de maiz sometidas a estres biotico. El experimento se llevo a cabo en la Facultad de Estudios Superiores Cuautitlan, UNAM, durante 2008. Para cumplir el objetivo, despues de algunas pruebas de calidad, tres grupos de semillas fueron sometidos por separado a los ataques de Aspergillus flavus y Fusarium moniliforme. Un primer grupo fue considerado como testigo positivo, otro fue recubierto con solucion de quitosan y un ultimo grupo fue danado mecanicamente antes de la aplicacion del biopolimero. Durante cinco semanas, el crecimiento de las plantulas se evaluo midiendo la longitud total, longitud de las hojas, de los tallos y el grosor de estos. No hubo incremento significativo en el tamano de las plantulas, provenientes de semillas recubiertas con quitosan al compararse con el resto de los grupos; sin embargo, la ausencia de enfermedades en las plantulas tratadas con el biopolimero fue evidente. En la quinta semana de crecimiento, las estructuras foliares de las plantulas se sembraron en agar PDA, para determinar la presencia de los hongos estresantes. Se encontro que las hojas provenientes de las semillas tratadas con quitosan, desarrollaron carga fungica nula, lo que sugiere que el quitosan actua como un activador de mecanismos de defensa en plantulas de maiz, impidiendo la infeccion por los hongos patogenos utilizados. EnglishMaize (Zea mays L.) is an important crop in Mexico, which is often affected by the presence of pathogenic fungi. The objective of this paper was to determine the protective effect of chitosan in maize seedlings subjected to biotic stress. The experiment was conducted at the School of Advanced Studies Cuautitlan, UNAM, in 2008. In order to achieve the aim, after some quality tests, three groups of seeds were separately subjected to attacks by Aspergillus flavus and Fusarium moniliforme. A first group was considered as a positive control, another was coated with chitosan solution and, a final group was mechanically damaged before application of the biopolymer. For five weeks, the seedling growth was evaluated by measuring the total length, length of leaves, stems and, their thickness. There was no significant increase in the size of seedlings from seeds coated with chitosan when compared to the other groups, but, the absence of diseases in the seedlings treated with the biopolymer was quite evident. In the fifth week of growth, leaf structures of the seedlings were planted in agar PDA in order to determine the presence of stresful-fungi. It was found that, leaves from the seeds treated with chitosan developed no fungal burden, suggesting that, chitosan acts as an activator of defense mechanisms in maize seedlings, preventing infection by the pathogenic fungi.