DAN - Dissertações de mestrado
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- Eficácia de um filme ativo na oxidação lipídica de alimentos com alto teor de gorduraPublication . Castro, Frederico; Vilarinho, Fernanda; Dias, DeodáliaFood packaging is currently manufactured using synthetic polymers, such as polyethylene, and its main function is the protection against external factors such as temperature changes, radiation, micro and macroorganisms. In response to the last few years the high demand for an improvement in packaging and increase in foods shelf life, innovative packaging have emerged, including active packaging. These packages are intended to interact with packaged foods through the emission or the absorption of compounds and/or substances, delaying the natural process of food’s degradation such as lipid oxidation or growth of microorganisms, thereby increasing its shelf life. There are two types of active packaging: absorption and emission. In the case of emission active packaging, they contain in their matrix active compounds that interact directly with the packaged food. These compounds may be of natural origin, being the extracts of aromatic plants a valid option due to their biological properties such as antioxidant and antimicrobial capacity. The application of extracts of aromatic plants in food have been studied, and several of them are approved by the FDA (Food and Drug Administration) and by the European Union. With sustainability in mind, the food industry and the scientific community are increasingly looking for biopolymers that can be used in the production of food packaging, such as whey protein, a by-product of the dairy industry. The main objective of this work was the study of the efficacy of an edible active film, based on whey protein incorporated with an extract of aromatic plants, in the delay of the lipid oxidation of a high fat food. In a second part of this work, a survey was also carried out on the Portuguese population about canned food consumption habits and their knowledge about innovative packaging. Initially the antioxidant capacity of extracts from two aromatic plants, rosemary (Rosmarinus officinalis L.) and green tea (Camellia sinensis L.) were compared. Rosemary extract was obtained by a solid-liquid extraction method, while green tea was obtained directly as an extract. In order to compare the antioxidant capacity, four methods were performed: the DPPH free radical inhibition system, the β-carotene bleaching test, the determination of the total phenolic compounds and the determination of the total flavonoids. Next, it was verified if there was a synergistic effect between the extracts, by comparing the antioxidant activity of three mixtures with different percentages of the extracts of green tea and rosemary. The required amount of extract to inhibit 50 % of the DPPH free radical (EC50) was also determined. Based on the obtained results, the green tea extract was the chosen one for the incorporation into the active film. Afterwards, the whey protein based film was produced. The process was optimized and different percentages of glycerol (plasticizer) and green tea extract were tested. The chosen model food was fresh salmon, due to its high lipid content and short shelf life. Fresh salmon slices, approximately 30-35 g, were packed with the active film and the control film (without green tea extract), and stored at 5 ° C for different storage times (0, 5, 7, 10, 14 and 17 days). The level of lipid oxidation of unpackaged salmon slices, maintained at the same temperature, for 0, 3, 5, 7, 10 and 12 days was also tested. To evaluate the oxidative status of salmon fat, four methods were used: the peroxide index, the p-anisidine value, the TBARS assay and the hexanal monitoring. The results obtained in this work indicate that the active film based on whey protein, incorporated with green tea extract, was successfully produced and showed efficiency in delaying the lipid oxidation of fresh salmon samples up to 17 days of storage. Further studies are needed to evaluate the mechanical properties of the packaging, microbiological activity, sensorial analysis and additional tests for evaluation of the oxidative state, in order to commercialize the packaging. Regarding the results of the questionnaire, where 314 responses were obtained, it was verified that the Portuguese population consumes a large number of products in canned foods, namely tuna. However, very few individuals are aware of the migration of chemical compounds from the packaging to foods. In the case of innovative food packaging, a small number of respondents are aware of their functions. In the future, information on these packages should be disseminated in order to increase the knowledge of the Portuguese population.