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.

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, A(AC)2, suggesting the deletion of its carcinogenic properties.

Efecto de la adición de ácido cítrico sobre la degradación de las aflatoxinas y las propiedades funcionales de productos extrudidos de sorgo / Effect of citric acid addition on aflatoxin degradation and on functional properties of extruded sorghum products / Efeito da adição de ácido cítrico sobre a degradação das aflatoxinas e as propriedades funcionais de produtos extrudidos de sorgo

Harina de sorgo contaminada con aflatoxinas (AFB1+AFB2) a una concentración total de 140µg·kg-1, fue sometida a extrusión termoplástica usando un perfil de temperatura de 60-80-100ºC. El contenido de humedad (CH) de la harina fue ajustado a 20, 25 y 30% mediante la adición de diferentes cantidades de ácido cítrico (AC) acuoso a concentraciones de 0; 0,5; 1; 2; 4 y 8N. El perfil de temperatura, en combinación con el CH y la concentración de AC, afectaron significativamente la cantidad de aflatoxinas recuperadas en los extrudidos; el máximo porcentaje de eliminación fue de 35,5%. En los extrudidos procesados con altos CH y concentraciones de AC se encontraron los valores más altos en la diferencia de color (DE), así como los valores más bajos en viscosidad. Los índices de expansión fueron favorecidos a mayores CH y altas concentraciones de AC. Los mayores valores de fuerza al corte se encontraron en los extrudidos elaborados con un mayor CH; sin embargo, no se presentaron diferencias significativas para las diferentes concentraciones de AC evaluadas. Empleando condiciones moderadas durante la extrusión en combinación con altas concentraciones de AC se obtuvieron extrudidos con aceptable pH, color, viscosidad, así como con buenas propiedades funcionales y texturales.

Sorghum flour contaminated by aflatoxin at a concentration of 140µg·kg-1 was extrusion-cooked in a single screw extruder with a temperature profile of 60-80-100°C. The moisture content (MC) of the flour was adjusted to 20, 25 and 30% by adding aqueous citric acid (CA) at concentrations of 0, 0.5, 1, 2, 4 and 8N. The temperature profile in combination with the MC and CA concentrations significantly affected the extent of aflatoxin reduction in the extruded sorghum; the maximum percentage of aflatoxin reduction was 35.5%. In extruded sorghum prepared with high MC and CA concentrations, the highest values in color difference (DE) and smallest values of viscosity were found. The expansion index was favored by higher MC and CA concentrations. The highest cutting force values were found in extruded products prepared with a higher MC, but there were no significant differences between those values and the different CA concentrations evaluated. Using moderate extrusion conditions in combination with higher concentrations of CA, products were obtained with acceptable pH, color, viscosity, as well as with good textural and functional properties.

Farinha de sorgo contaminada com aflatoxinas (AFB1+AFB2) na concentração total de 140µg·kg-1, foi submetida ao proceso de extrusão termoplástica usando um perfil de temperatura de 60-80-100ºC. O conteúdo de umidade (CH) da farinha foi ajustado a 20, 25 e 30% mediante a adição de diferentes quantidades de ácido cítrico (AC) aquoso em concentrações de 0; 0,5; 1; 2; 4 e 8N. O perfil de temperatura, combinado com o CH e a concentração de AC, afetaram significativamente a quantidade de aflatoxinas recuperadas nos extrudidos; a máxima porcentagem de eliminação foi de 35,5%. Nos extrudidos procesados com alto CH e concentração de AC se encontraram os valores mais altos na diferença de cor (DE), assim como os valores mais baixos em viscosidade. Os índices de expansão foram favorecidos a maior CH e altas concentrações de AC. Os maiores valores de força ao corte se encontraram nos extrudidos elaborados com maior CH; no entanto, não se apresentaram diferenças significativas para as diferentes concentrações de AC avaliadas. Utilizando condiciones moderadas durante a extrusão em combinação com altas concentrações de AC se obtiveram extrudidos com aceitável pH, cor, viscosidade, assim como com boas propriedades funcionais e texturais.

Evaluación de una metodología para determinar características de textura de tortilla de maíz (Zea mays L) / Evaluation of a methodology to determine texture characteristics maize (Zea mays L) tortilla

La tortilla de maíz (Zea mays L.), es el principal alimento de la población Mexicana, con un consumo anual de 12 millones de toneladas. A pesar de su alto consumo, existe una gran variabilidad en las características de calidad de la tortilla producida comercialmente, principalmente las de textura. Para evaluar la textura de las tortillas se han reportado algunos métodos, pero los parámetros y valores obtenidos han sido muy variados y no comparten una base adecuada para su comparación. Además, la confiabilidad de los parámetros reportados, utilizando un texturómetro, tampoco ha sido evaluada. En este estudio se seleccionaron dos formas de la muestra, rectangular y probeta, así como la de varios parámetros de calidad obtenidos con el texturómetro (fuerza máxima, área total, área hasta fuerza máxima, elasticidad y elongación) y se evaluó su confiabilidad con base a su repetibilidad. De acuerdo a los resultados, la forma de "probeta" fue la más adecuada para las pruebas de tensión y elasticidad. Para la fuerza al corte, las dos formas resultaron con buena repetibilidad. La fuerza máxima fue el parámetro de mayor confiabilidad para las pruebas de tensión y corte, con una repetibilidad de 0.95 y 0.99 respectivamente. La elasticidad resultó con buena repetibilidad cuando la prueba se realizó con la forma de probeta (0.94). Utilizando el texturómetro y la forma de muestra tipo probeta, los parámetros determinados muestran alto grado de confiabilidad y facilitan la comparación de datos de textura para tortillas de maíz