Quantificação de estigmatadienos em azeite de oliva (Olea europea L.) por cromatografia em fase gasosa. / Stigmastadiene quantification in olive oil (Olea europaea L.) by gas chromatography.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The olive oil is a product with high nutricional value and has been conquesting their space in the consumer market due to their organoleptic characteristics (aroma and taste). The cultivation of olive trees, the harvesting of the olive fruits, and the extraction of olive oil are hard and time-consuming tasks, contribuing to it high commercial price. Therefore, attempts to adulterate this commodity with less expensive materials, such as refined olive oil, are by no means rare. Needless to say, this practice deteriorates its quality and nutricional value and causes major economic losses. This work proposes to stimulate the bigger advantage of the olive oil inspection and quality control sector, showing the importance of aplication of a more specific methodology in the search for adulteration in this product. This study proposes the stigmastadiene quantification, such as the main technic able to identify frauds in extra virgin and virgin olive oil. This analytical method consists of saponification of the sample with internal standard (cholesta-3,5-diene), extraction of unsaponifiable matter and fractioning of the unsaponifiable components by column chromatography on silica gel and identification and quantification of the stigmasta-3,5-diene and their isomer through gas chromatography with flame ionization detector. The stigmastadiene chromatographic separation was accomplished in melted silica capillary column HP-5 (5% diphenyl 95% dimethyl polisiloxane, 60 m x 0,25 mm x 0,25 ?m), with slope of 2ºC/ min, starting at 235ºC and finishing at 285ºC. Thirty brands of olive oil were purchased (extra virgin olive oil and virgin olive oil) available in Campinas market, imported from Portugal, Spain, Italy, Greece, Argentina and Lebanon, from which 27 brands were bottled in the origin country. The samples had previously undergone a quality analysis, that involves the free fatty acid determination (%FFA), peroxide index and specific extinction coefficient determination (K232, K270 and DK). Later, purity analysis were accomplished, with the fatty acid composition determination and consequent evaluation of mono and polyunsaturated, of trans isomers content, calculated iodine and saponification values, triacylglycerol composition determination (ECN42), stigmastadienes determination and evaluation of sterols composition. It was observed that 2 brands showed an acidity content above the limite values, and another 2 brands showed a peroxide index above the limite established. The absorptivity at 232 nm, 270 nm and DK confirmed the adulteration on 4 brands of olive oil. Through the fatty acid composition and consequent evaluation of saponification and iodine values, only one brand adulteration was detected, due to the low oleic and high linoleic acid. Four brands showed trans isomers contents above the limit values. Through the triacylglycerol composition determination (ECN42), adulteration was detected in 6 brands of olive oil. However, stigmastadiene quantification indicated adulteration in 8 brands. This brands were submitted to the evalution of sterols composition, that indicated frauds in 4 brands with another vegetable oil, 3 brands with refined olive oil and one brand with olive pomace oil. The triacylglycerol composition determination (ECN42), the stigmastadiene quantification and the sterols composition were very efficient in the detection of extra virgin olive oil adulteration with another vegetable oils and with refined olive oil.

ASSUNTO(S)

adulterations cromatografia gasosa gas chromatography 3 5 stigmastadiene azeite de oliva adulterações estigmastadieno olive oil

ACESSO AO ARTIGO

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