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Farmed fish as a functional food: fortification strategies with health valuable compounds
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Abstract(s)
A actual tendência na indústria de aquacultura para substituir a farinha de peixe e o óleo de peixe por fontes alternativas tem reduzido os níveis de n-3 LCPUFA e microelementos, como iodo e vitamina D3, dos quais o pescado é a principal fonte alimentar natural. A utilização de dietas compostas permite modular a alimentação dos peixes com nutrientes benéficos para a saúde de forma a melhorar a qualidade e o valor nutricional do pescado. A aplicação de um questionário on-line sobre o conceito de fortificação (capítulo 2) revelou que metade dos entrevistados concorda com a fortificação de peixes e estaria disposta a consumir peixe fortificado. Os entrevistados que mostraram um menor interesse em conhecer a origem do pescado (i.e. selvagem vs aquacultura) foram os mais receptivos ao conceito de fortificação. Seguidamente, foram realizados vários ensaios experimentais tendo como principal objectivo a fortificação dos músculos de dourada e de truta arco-íris com compostos benéficos para a saúde humana. Verificou-se um aumento da concentração de iodo e selénio no músculo de dourada e truta como resposta a uma fortificação desses minerais, provenientes de fontes distintas (Capítulo 3). Utilizando níveis semelhantes de suplementação, verificou-se que o teor máximo de iodo no filete de dourada foi maior do que o de truta, o que provavelmente estará associado às diferentes necessidades fisiológicas de homeostasia entre peixes de água doce e marinhos. A eficácia da suplementação alimentar para aumentar a concentração de iodo no músculo dos peixes poderá estar mais dependente da espécie do que da fonte de iodo utilizada. Na truta, obteve-se uma fortificação eficaz de selénio no músculo, após a utilização de uma dieta suplementada com levedura selenizada. A fortificação do músculo de peixes com suplementação alimentar de vitamina D3 é, aparentemente, um processo mais complexo apresentando resultados variáveis (capítulo 4). O aumento de vitamina D3 na dieta, de um nível basal para o nível máximo permitido, não resultou num aumento significativo da concentração de vitamina D3 no músculo. No capítulo 5, discutem-se resultados de um estudo para avaliar o potencial da biomassa de microalgas, recorrendo à diatomácea Phaeodactylum tricornutum, como ingrediente funcional em alimentos para dourada. Observou-se que a utilização de microalgas na dieta permitiu tornar mais apelativa a aparência externa dos peixes, originando uma pigmentação amarela mais viva no opérculo e uma coloração mais clara na região ventral. Além disso, uma avaliação visual realizada por um painel não treinado, mostrou uma clara preferência pelos peixes alimentados com microalgas comparativamente aos alimentados com uma dieta comercial. As matérias-primas provenientes de espécies marinhas, tradicionalmente usadas em alimentos para aquacultura, são recursos escassos, em particular o óleo de peixe rico em n-3 LCPUFA. De forma a estudar a baixa retenção de EPA e DHA alimentar pelos peixes, desenvolveu-se uma estratégia nutricional para promover a retenção metabólica de n-3 LCPUFA no músculo de dourada (Capítulo 6). A composição em ácidos gordos nos tecidos não depende apenas da concentração em gordura dos alimentos, mas é influenciada pelas suas proporções relativas. A composição inicial em ácidos gordos no peixe parece desempenhar um papel importante na eficiência de retenção de EPA e DHA. Observou-se um aumento significativo da retenção de EPA e DHA com a ingestão de MUFA em peixes inicialmente alimentados com uma dieta à base de ingredientes vegetais. A retenção de EPA e DHA no músculo de dourada foi relativamente baixa, sendo a retenção de DHA, geralmente, mais do dobro de EPA.
Em conclusão, relativamente a ensaios de fortificação, a utilização de compostos a partir de fontes naturais e/ou orgânicas foi considerada igualmente ou mais eficaz do que a partir de fontes sintéticas. Nos diversos ensaios de fortificação realizados verificou-se que o contributo nutricional dos filetes de truta e de dourada (dose de 160 g) para uma Ingestão Diária Adequada de EPA e DHA foi acima dos níveis recomendados. A mesma dose de filetes de truta tem um contributo de 98% em selénio, mais de 100% em vitamina D3 e 13% em iodo, para a Dose Diária Recomendada. O consumo de 160g de filetes de dourada cobre 60% em vitamina D3 e 84% em iodo dos níveis da Dose Diária Recomendada. As estratégias de fortificação promoveram o aumento do contributo nutricional dos filetes de truta e de dourada, em compostos benéficos para a saúde, resultando em novos produtos, potencialmente candidatos ao mercado de alimentos funcionais. Ao longo do nosso trabalho, foi possível gerar novos conhecimentos sobre a eficácia de fortificação de rações como ferramentas para modular características nutricionais e de qualidade do pescado de aquacultura
The current trend in the aquaculture industry of replacing fish meal and fish oil by alternative ingredients is reducing the levels of n-3 LCPUFA and microelements such as iodine and vitamin D3, of which fish is the main natural food source. Exogenous feeding in aquaculture unlocks the possibility to tailor fish composition with healthy beneficial nutrients improving quality and nutritional value of edible fish. An on-line survey to inquire about the concept of fish fortification (chapter 2) showed that half of respondents agreed with it and were willing to consume fortified fish. Respondents less interested on fish origin (wild vs aquaculture) were more receptive to fortification. Subsequently, several experimental trials were undertaken targeting the muscle fortification of gilthead seabream and rainbow trout with health beneficial compounds. Seabream and trout were able to accumulate iodine and selenium in muscle as response to a dietary fortification of these trace minerals, supplied from distinct sources (chapter 3). At similar supplementation levels, the maximum fillet iodine content found in seabream was higher than that found in trout which is probably associated with the physiological needs for homeostasis of freshwater and marine fish. Efficacy of dietary fortifications aiming to raise iodine concentration in fish muscle may be more dependent on the targeted fish species than on the iodine source used. In trout, an effective muscle fortification with selenium was achieved with a selenised yeast supplemented diet. Fortification of fish muscle with vitamin D3 via dietary supplementation is apparently a more complex process, showing variable results (chapter 4). Raising dietary vitamin D3 from a basal level to the maximum permitted level did not significantly enhance fillet vitamin D3 contents. In chapter 5, a study was undertaken to assess the potential of microalgae biomass, from the diatom Phaeodactylum tricornutum, as a functional ingredient in seabream feeds. Results showed that algae-fed seabream positively improved external appearence, originating a more vivid yellow pigmentation of the operculum and a lighter colouration of ventral skin. Moreover, an untrained consumer panel showed a clear preference for algae-fed fish when compared with those fed a commercial diet. Marine-derived raw materials traditionally used in aquafeeds are scarce resources, mainly fish oil rich in n-3 LCPUFA. To tackle the low retention of dietary EPA and DHA in fish, our work focused on a nutritional strategy to foster the metabolic sparing of n-3 LCPUFA in gilthead seabream fillets (Chapter 6). The fatty acid composition of tissues is not solely dependent on the quantitative fatty composition of feeds but is also affected by their relative ratios. The initial fatty acid composition of fish seems to play a significant role on the EPA and DHA sparing efficiency. A higher MUFA intake led to a significant increase on EPA and DHA retention in fish with a vegetable nutritional background. Retention of combined EPA and DHA in seabream fillets was relatively low, with DHA retention generally more than double of EPA. The use of natural/organic compound sources in fortification trials were equally or more efficacious than the synthetic ones and should be considered adequate alternatives. In the various fortification trials, the nutritional contribution of trout and seabream fillets (160 g serving) to the daily adequate intake of combined EPA and DHA was well above the recommended levels. The serving amount of trout fillets could contribute to 98% of selenium, over 100% of vitamin D3 and 13% of iodine Daily Recommended Intakes, respectively. In turn, the consumption of 160g of seabream fillets would cover 60% of vitamin D3 and 84% of iodine Daily Recommended Intake levels. The fortification strategies enhanced the nutritional contribution of seabream and trout fillets in health beneficial compounds resulting in novel products, and thus resulting in potential candidates to the functional foods market. Throughout our work we contributed towards the generation of new data on the efficacy of feed fortification strategies as tools to modulate several traits of farmed fish.
The current trend in the aquaculture industry of replacing fish meal and fish oil by alternative ingredients is reducing the levels of n-3 LCPUFA and microelements such as iodine and vitamin D3, of which fish is the main natural food source. Exogenous feeding in aquaculture unlocks the possibility to tailor fish composition with healthy beneficial nutrients improving quality and nutritional value of edible fish. An on-line survey to inquire about the concept of fish fortification (chapter 2) showed that half of respondents agreed with it and were willing to consume fortified fish. Respondents less interested on fish origin (wild vs aquaculture) were more receptive to fortification. Subsequently, several experimental trials were undertaken targeting the muscle fortification of gilthead seabream and rainbow trout with health beneficial compounds. Seabream and trout were able to accumulate iodine and selenium in muscle as response to a dietary fortification of these trace minerals, supplied from distinct sources (chapter 3). At similar supplementation levels, the maximum fillet iodine content found in seabream was higher than that found in trout which is probably associated with the physiological needs for homeostasis of freshwater and marine fish. Efficacy of dietary fortifications aiming to raise iodine concentration in fish muscle may be more dependent on the targeted fish species than on the iodine source used. In trout, an effective muscle fortification with selenium was achieved with a selenised yeast supplemented diet. Fortification of fish muscle with vitamin D3 via dietary supplementation is apparently a more complex process, showing variable results (chapter 4). Raising dietary vitamin D3 from a basal level to the maximum permitted level did not significantly enhance fillet vitamin D3 contents. In chapter 5, a study was undertaken to assess the potential of microalgae biomass, from the diatom Phaeodactylum tricornutum, as a functional ingredient in seabream feeds. Results showed that algae-fed seabream positively improved external appearence, originating a more vivid yellow pigmentation of the operculum and a lighter colouration of ventral skin. Moreover, an untrained consumer panel showed a clear preference for algae-fed fish when compared with those fed a commercial diet. Marine-derived raw materials traditionally used in aquafeeds are scarce resources, mainly fish oil rich in n-3 LCPUFA. To tackle the low retention of dietary EPA and DHA in fish, our work focused on a nutritional strategy to foster the metabolic sparing of n-3 LCPUFA in gilthead seabream fillets (Chapter 6). The fatty acid composition of tissues is not solely dependent on the quantitative fatty composition of feeds but is also affected by their relative ratios. The initial fatty acid composition of fish seems to play a significant role on the EPA and DHA sparing efficiency. A higher MUFA intake led to a significant increase on EPA and DHA retention in fish with a vegetable nutritional background. Retention of combined EPA and DHA in seabream fillets was relatively low, with DHA retention generally more than double of EPA. The use of natural/organic compound sources in fortification trials were equally or more efficacious than the synthetic ones and should be considered adequate alternatives. In the various fortification trials, the nutritional contribution of trout and seabream fillets (160 g serving) to the daily adequate intake of combined EPA and DHA was well above the recommended levels. The serving amount of trout fillets could contribute to 98% of selenium, over 100% of vitamin D3 and 13% of iodine Daily Recommended Intakes, respectively. In turn, the consumption of 160g of seabream fillets would cover 60% of vitamin D3 and 84% of iodine Daily Recommended Intake levels. The fortification strategies enhanced the nutritional contribution of seabream and trout fillets in health beneficial compounds resulting in novel products, and thus resulting in potential candidates to the functional foods market. Throughout our work we contributed towards the generation of new data on the efficacy of feed fortification strategies as tools to modulate several traits of farmed fish.
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Keywords
Nutrição de peixes Suplementação de alimentos Qualidade do pescado Contributo nutricional Percepção do consumidor Alimentos funcionais