Avaliação de resíduos de transgênicos em alimentos no Brasil e desenvolvimento de metodologias de análise

• Autor(a) principal: Marcelino, Francismar Corrêa
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1415
• topic: OGM; PCR quantitativo; Alimentos transgênicos; GMO; Quantitative PCR; Transgenic foods; CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA MOLECULAR E DE MICROORGANISMOS

Since the liberation of the first transgenic variety for human consumption, the tomato Flavr savr , in 1995, the plantation and commercialization of genetically modified organisms (GMOs) has increased over 50 times, reaching 90 million hectares planted with some kind of GMO in 21 countries, in 2005. It is estimated that in 2006 this value will surpass 100 million hectares. In Brazil, the liberation of plantation and commercialization of GMOs only occurred in 2003, with the soybean Roundup Ready® (RR). The increase on planting and commercialization of GMOs is reflected on the increase of their presence in the composition of foods. In the present work, the national panorama of the presence of GMOs in different products, analyzed by the company AgroGenética, between the years 2000 and 2005, is shown. Different types of food were analyzed which presented, mainly, soybean and/or maize in their composition, as well as grains and products in natura, derived from different regions of the country. According to the results, GMO residues are present in foods commercialized in the country since the first year of their analysis by the company; each year, the number of samples containing transgenic residues has increased, being mainly detected in foods with high soybean content in their composition, such as sausages and breaded foods. This situation has led to the necessity of developing methodologies that allow the detection, quantification and identification of these residues. One of the main difficulties in the analysis of transgenic residues in food is the need of extracting satisfactory amounts of DNA and with good quality for analysis. This work also presents the process of validation of DNA extraction procedures for analysis of presence and quantification of transgenic residues in sausages, the product class that presented the greatest number of positive samples for the presence of transgenic residues (70.73%). In addition to the availability of good quality DNA, another critical stage for the GMO quantification by the quantitative PCR technique is the establishment of a calibration curve to be employed in the analysis. The presence of GMOs in a sample is given in absolute terms, so that a calibration curve must be established with standards that present carefully defined GMO concentration. The reference standards are essential for the determination of the percentage of GMOs present in the samples, and are specific for each type of event and organism. Currently, certified reference standards are not available in the international market for all events and transgenic varieties, and the only commercialized ones are calibration standards that vary only from 0.1 to 5% in flour weight of the genetically modified grain in relation to the flour weight of the normal grain of the species in question. At the final stage of this work, the development of calibration standards based on plasmid DNA is described. The established curve based on plasmid DNA allowed the precise quantification of the percentage of transgenic residues in the samples, when compared to the quantification using genomic DNA obtained from certified reference standards.