| Resumo: | In the last years, the consumption of processed foods has increased, mainly due to changes in consumers’ lifestyle. Therefore, dietary habits of people are changing and it is of utmost importance to evaluate the nutritional quality of processed foods. Processed foods are recognized as sources of sugar, salt and fat. With respect to fat, according to the literature, these foods are mainly rich in saturated fatty acids. Moreover, since some of these foods have partially hydrogenated edible oils as ingredients, it is also very important to evaluate trans fatty acids (TFA) content of processed foods. Gas chromatography is the most used analytical method to determine the fatty acids profile of foodstuffs, since this technique presents better sensitivity and it allows separation of the different fatty acids isomers. In the present study, gas chromatography has been used to evaluate the nutritional quality of 236 processed foods (bakery products, soups, burgers, patties, seeds, nuts, French-fries, potato crisps, pizzas, sauces, cereals, biscuits, ready to eat meals, among others). Samples to be analysed were selected by reviewing existing data on the contribution of processed foods to the intakes of saturated fat, TFA and salt. Samples were purchased from supermarkets and fast-food restaurants. The selected processed foods were analysed regarding their fatty acids profile. The methylation of fatty acids was performed using 0.25 mL of methanolic potassium hydroxide (2 M) and 2 mL of n-heptane. Then, a gas chromatograph equipped with a flame ionization detector was used. Fatty acids methyl esters were separated in a Supelco®-2560 column (100 m x 0.25 mm i.d., 0.25 µm film thickness). According to the obtained results, for the bakery products, it was possible to confirm that fatty acids profile can be used to discriminate the different types. For example, it was possible to identify the healthier processed food, between similar foods, using the fatty acids analysis. Moreover, for potato crisps group the determination of fatty acids profile was also very useful to identify the oil/fat that was used as the frying medium. For other groups of processed foods this type of analysis was not sufficient, and a deeper analysis using other parameters, such as salt, was used to evaluate its nutritional quality. Regarding TFA, in general the analysed processed foods have low contents. Authors consider that the content of TFA has significantly been reduced during the last years, possibly due to industry reformulations. In conclusion, the obtained results will be essential to perform an update regarding the fatty acids profile of processed foods consumed by the Portuguese people. Also, these results will be included in the Portuguese Food Composition Database, which from a nutritional point of view, will make possible to perform associations between the intake of these foods and the impact that they can have in the health status of consumers. In the near future, we intend to include more types of processed foods in order to take a broader view of the current situation in Portugal.
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