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Advisor(s)
Abstract(s)
Canned 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.
Description
Keywords
Canned Tuna Research Subject Categories::TECHNOLOGY::Chemical engineering::Food technology
Pedagogical Context
Citation
Ferreiro, Nuno Manuel; Duarte, Karina Sofia; Fernandes, Conceição; Pereira, J.A.; Rodrigues, Nuno (2022). Effect of heat treatment on the quality and composition of canned tuna coating liquid. In XVI Encontro de Química dos Alimentos - Bio-Sustentabilidade e Bio-Segurança Alimentar, Inovação e Qualidade Alimentar: Livro de Resumos. Castelo Branco
Publisher
Sociedade Portuguesa de Química