Percorrer por autor "Duarte, Karina Sofia"
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- Effect of heat treatment on the quality and composition of canned tuna coating liquidPublication . Ferreiro, Nuno Manuel; Duarte, Karina Sofia; Fernandes, Conceição; Pereira, J.A.; Rodrigues, NunoCanned tuna is one of the most popular products on the market with great commercial value.1 It is a product rich in protein, and fat that is mainly unsaturated fatty acids, namely omega-3 as an essential fatty acid. Tuna can be presented and commercialized with different covering liquids. Olive oil is a vegetable oil rich in monounsaturated fatty acids with different organoleptic properties from other vegetable oils.2 According to the intensity of fruitiness, extra virgin olive oil can be classified as ripe fruity and green fruity, the latter being classified as mild, medium and intense, depending on the intensity. Temperature is one of the factors that degrade the organoleptic characteristics of olive oil.3 In this sense, the present work aims to study the effect of the application of heat treatment on tuna coating liquids. To this end, different coating liquids were studied (sunflower oil, refined olive oil, mature olive oil, soft green and intense green), and the behaviour with the application of heat was verified. Fifty cans were filled with coating liquid, closed in a crimping machine and pasteurized following the usual procedure in the industry. The filling liquids were analysed before and after heat treatment, namely at time 0 (T0) and at the end of six months (T6), having been stored at room temperature and at 50ºC. Quality parameters (free acidity, peroxide value, specific extinction coefficients), oxidative stability by the Rancimat method and antioxidants (DPPH and total phenols) were evaluated for each sample. Regarding the quality parameters at T0, it was found that most of the values are within the legal limits established by regulation 2568/1991, except for the acidity parameter in mature olive oil, which presented an average value of 0.98%, and also for the sunflower oil in K232, K268 and ΔK that exceeds the established value. Regarding the covering liquids in T6 with heat treatment at 50ºC, it was verified in the free acidity that they all exceed the legal limit. In the case of peroxide value, all meet the legal limits and for K232 only sunflower oil exceeds the legal limit. In K268 the limits are exceeded by all hedging nets. In the case of ΔK, only sunflower oil exceeds the legal limit. There was a clear increase in the parameters: free acidity and peroxide value from T0 to T6 50ºC, where as in the specific extinction coefficients, this increase was not registered. Regarding the oxidative stability, comparing the T0 with the T6 50ºC, it was found that both in the T0 and in the T6 50ºC the sunflower oil was the one with the lowest oxidative stability. At T0, refined olive oil was the one that showed the highest oxidative stability, while at T6 50ºC, the mature green olive oil showed the highest stability. Regarding the antioxidants, namely DPPH, it was found at both times that sunflower oil had the lowest percentage of inhibition and intense green olive oil the highest. The same happened in the total phenols. With this work, it is possible to see that sunflower oil is clearly the liquid coverage that has the lowest qualities for consumers since it was the one that presented the lowest values in all parameters, even not respecting the legal limits of some parameters. It was found that olive oil is, from the quality and benefit to the consumer point of view, the best topping liquid to adopt to accompany tuna, given that even with the application of temperature, there are drastic drops in the proportion of antioxidants. Adopting olive oil as a vegetable covering will make it possible to have a combination of nutritional and organoleptic properties of better quality for the consumer.
- Utilização de azeite virgem extra com diferentes intensidades de frutado como líquido de cobertura na valorização de conservas de pescadoPublication . Duarte, Karina Sofia; Fernandes, Conceição; Rodrigues, NunoO azeite e o pescado são dois importantes constituintes da Dieta Mediterrânea, dado as suas propriedades altamente nutritivas e saudáveis. Estes dois produtos muito ricos, podem ser misturados como forma de complemento, um ao outro. A inovação e a qualidade dos produtos têm sido, nos ultimos anos, alvo de procura dos consumidores, nesse sentido, as industrias do pescado têm trabalhado formas de inovar e aumentar a qualidade dos seus produtos para responder às exigencias dos consumidores. Assim, com a presente dissertação procurou-se estudar o efeito da utilização de diferentes azeites virgem extra, como líquido de enchimento, nas características físico-químicas e sensoriais em conservas de atum, e relacionar estes, com o azeite refinado e o óleo vegetal. Além disso, estudou-se o efeito do tempo de prateleira no T0 (15 dias) e T6 (6 meses), quer à temperatura ambiente, quer em condições de aceleração a 50º. Foram utilizados diferentes azeites virgem extra com crescentes intensidades de frutado maduro, verde suave e verde intenso. Os parâmetros avaliados incluíram no atum a atividade antioxidante, cor, textura, pH, humidade e cinzas, bem como as características sensoriais; no óleo de girassol e nos azeites a atividade antioxidante, parâmetros de qualidade, estabilidade oxidativa e análise sensorial. Os resultados obtidos mostraram que os azeites/óleo de girassol, após o processamento possuem menor estabilidade a nível da atividade antioxidante, no entanto verificou-se que o azeite verde intenso é o azeite que possui maior atividade antioxidante comparativamente com as outras amostras, seguido do verde suave. O atum em contato com o óleo de girassol e os azeites, perdeu a consistência ao longo do armazenamento, em contrapartida, houve um aumento na intensidade dos outros atributos (p.e. suculência), para o T0 (após os 15 dias de enchimento) e T6 (após os 6 meses de enchimento). Nos parâmetros, como a agradabilidade do sabor e do aroma, e intensidade, o óleo de girassol e os azeites tiveram valores muito próximos, mas nas conservas de atum em contato com o óleo de girassol e o azeite refinado foram obtidas maiores intensidades para quase todas as amostras (T0 e T6). Constatou-se ainda que o tratamento térmico diminui a qualidade das amostras e que a diferença foi mais expressiva para as amostras no T6, principalmente à temperatura de 50ºC (teste de aceleração). De uma forma geral pode-se dizer que a utilização dos azeites com intensidades de maduro, verde suave e verde intenso, em comparação com o azeite refinado e o óleo de girassol (comumente utilizado), acresce qualidade nutricional e organolética às conservas de atum. Os azeites virgens extra verde intenso e verde suave demostraram ser os azeites mais promissores.