Folatos, capacidade antioxidante e trans-2-nonenal em cerveja brasileira / Folate, antioxidant capacity and E-2-nonenal in Brazilian beer

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

In the present study methods were adapted and applied to quantify levels of folate, antioxidant capacity assessment and E-2-nonenal quantification in Brazilian beers. 5 brands of Pilsen, non-alcoholic and Malzbier beers were used, in can and amber bottle. For determination of folates (folic acid - FA, 10-methyl-folic acid - 10Methyl, 5-methyltetrahydrofolate - 5Methyl, 5-formyltetrahydrofolate - 5Formyl and 10-formyl-folic acid - 10Formyl) B vitamins, a method using liquid chromatography (HPLC) was employed. In the chromatographic step a C18 column was used and was applied a gradient elution with mobile phase consisting of an acetic acid 2.0% solution adjusted to pH 2.8 and acetonitrile, at a flow rate of 0.5 mL / min. The detection was performed with the diode array detector at 290nm for FA and 10Methyl, and with a fluorescence detector at ?exc. 290nm and ?emis. 360nm in the detection of 5Methyl and 5Formyl, and at ?exc. 290nm and ?emis. 445nm for the 10Formyl. After its validation, the method presented correlation coefficients ranging from 0.9970 to 0.9999 mg/100 mL, detection limits from 0.07 to 2.42 mg/100 mL and quantification limits between 0.22 and 8.07 mg/100 mL. The standard deviation (SD) was between 0.75 and 5.01% and intermediate precision was from 1.20 to 9.99%. Tests of recovery levels were resulted between 92 and 107%. Folates found in beers were 10Methyl, 5Methyl and 10Formyl. The total folate levels found among types of fresh beers ranged from 18.26 to 23.99 µg/100mL. These vitamins were monitored during beer shelf life (6 months), being evaluated in freshly brewed beer and at every subsequent 2 months. Overall levels of folate found decreased over the shelf life, but it was not possible to verify the effect of package to protect beer against degradation of the vitamins. Evaluation in different batches showed a great variation, with SD up to 52.42%. To determine the total phenolic content was applied the Folin-Ciocalteau method, by which they were found 47.05, 18.67 and 21.83 in mg/100mL equivalents gallic acid (EGA) for Malzbier beer, alcohol-free Pilsen and Pilsen, respectively. The type of packaging used, can or bottle, had relevance to the total phenolic content only for Pilsen beer. Nonalcoholic beer showed the highest variation. To evaluate the antioxidant capacity, tests using the radical 2,2 - diphenyl -1 - picrylhydrazyl (DPPH) and the ferric reduction antioxidant power (FRAP) were performed. The two tests indicated the beer Malzbier has the highest antioxidant capacity, which agrees with the content of total phenolics. For identification and quantification of E-2-nonenal, a major cause of aged flavor in beers, it was used a headspace method with micro solid phase extraction and gas chromatography technique coupled with mass spectrometry (HS-SPME-GC-MS). A 5%- phenyl-methylpolisiloxane (HP-5MS) column was used. The chromatographic conditions used beginning in temperature of 60 ºC, ranging from 3 ºC / min up to 100 ºC. Then, ramp of 10 °C / min until 200 ºC and then stay at 200 ºC for seven minutes to clean the column. The carrier gas (helium) had constant flow of 1.0 mL / min. The monitored ions were 55, 70 and 83 (m/z) (source of ionization 70eV), after verification of mass spectra of the compound. Levels of E-2-nonenal ranged from 0.11 to 0.46 µg/L in beer cans, being above its threshold. For this compound significant difference was found between samples of the same type of beer, but there was no significant difference between the three types of analyzed beer. This study showed that the Brazilian beer have beneficial substances to human health, with similar content to other food, and that the E-2-nonenal is still present in quantities above the threshold in the beverage, which can compromise its quality. In general, the packaging, can or bottle, did not influence the content of the analyzed substances, and Malzbier beer stood out for greater antioxidant capacity

ASSUNTO(S)

cerveja cromatografia folatos antioxidantes trans-2-nonenal beer chromatography folates antioxidants e-2-nonenal

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