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Este trabalho descreve métodos de determinação de cromo e manganês nas frações bioacessíveis de suplementos alimentares, como hipercalóricos, whey protein e protein bar por espectrometria de absorção atômica em forno de grafite (GFAAS). Para o desenvolvimento dos métodos, as frações bioacessíveis foram submetidas à digestão assistida por radiação micro-ondas e posterior otimização instrumental das temperaturas de pirólise e atomização. Para o manganês, nas amostras de whey protein e protein bar, obteve-se as mesmas temperaturas de pirólise e atomização: 1100 e 1600 °C, respectivamente; para hipercalóricos foi empregado o uso de modificador químico, Mg(NO3)2, e suas temperaturas de pirólise e atomização foram de 1200 e 1700 °C, respectivamente. Para o cromo, não foi preciso o uso de modificador e as temperaturas de pirólise e atomização otimizadas foram as mesmas para as três amostras: 1500 e 2300 °C, respectivamente. A exatidão dos métodos foi investigada através de ensaios de adição e recuperação de analito, apresentando para o manganês valores na faixa de 84 a 113% e para o cromo, valores entre 101 e 116%. A precisão dos métodos também foi avaliada, mostrando desvios padrões relativos menores que 15%. A massa característica (m0), limites de detecção (LD) e quantificação (LQ) para os métodos de cromo foram de 1,9 pg, 0,07 μg g-1 e 0,2 μg g-1, respectivamente; para manganês em hipercalórico os valores obtidos foram de 1,8 pg, 0,03 e 0,08 μg g-1; já em whey protein e protein bar os mesmos foram de 4,2 pg, 0,12 μg g-1 e 0,3 μg g-1. Os métodos desenvolvidos foram aplicados em 12 amostras de suplementos alimentares, sendo 4 de hipercalóricos, 3 de whey protein e 5 de protein bar. Foram observados valores de porcentagem de bioacessibilidade para cromo: 12% em whey protein, 16% em protein bar e, 39 e 49% em hipercalóricos. Em contrapartida, somente uma amostra de whey protein apresentou porcentagem bioacessível não significativa para manganês, e os resultados variaram de 6 até 99%. This study describes methods for the determination of two minerals, chromium and manganese, in the bioaccessible fractions of food supplements, like hypercaloric, whey protein and protein bars, by graphite furnace atomic absorption spectrometry. For the development of the methods, the bioaccessible fractions were submitted to digestion assisted by microwave radiation and posterior instrumental optimization of pyrolysis and atomization temperatures. For manganese, whey protein and protein bars samples obtained the same pyrolysis and atomization temperatures: 1100 and 1600 °C, respectively; for hypercaloric, the use of the modifier Mg(NO3)2 was employed and the pyrolysis and atomization temperatures were 1200 and 1700 °C, respectively. For chromium, it was not necessary the modifier and the pyrolysis and atomization temperatures for the three types of samples were 1500 and 2300 °C, respectively. The accuracy of the methods were investigated through addition and recovery tests; for manganese the study showed reveries in a range of 84 to 113% and for chromium in a range of 101 to 116%. The precision of the methods was also evaluated and presented relative standard deviation values smaller than 15%. The characteristic mass (mo), limits of detection (LD) and quantification (LQ) for chromium were 1,9 pg, 0,07 i_tg g-1 and 0,2 i_tg g-1, respectively; for manganese, in hypercaloric the values found were 1,8 pg, 0,03 and 0,08 i_tg g-1; and finally, in whey protein and protein bars the values were 4,2 pg, 0,12 ilg g-1 and 0,3 ilg g-1. The developed methods were applied to 12 food supplement samples, being 4 of hypercaloric, 3 of whey protein and 5 of protein bars. Four of those samples presented chromium bioaccessible percentage: 49 and 39% in hypercaloric, 12% in whey protein and 16% in protein bars. On the other hand, only one sample of whey protein did not present significant manganese bioaccessible percentage, varying in a range of 6 to 99%.

Mestrado em Engenharia Alimentar - Processamento de Alimentos - Instituto Superior de Agronomia This work investigates the effect of a drastic cooking treatment in chemical composition, particularly, on lipid profile of two species of farmed fish, salmon and meagre, and quantifies the percentage of each fatty acid bioacessibility on these two species in each culinary treatment. To this end, are used methodologies for extracting total lipids (TL), based on the techniques of Bligh & Dyer (1959), for thin layer chromatography and the transesterification of fatty acid methyl esters (FAME - Fatty Acid Methyl Esters). It is verified that the culinary treatment promotes the moisture loss and, consequent, concentration of the fatty acids from the food, although this effect is not uniform for all fatty acids or to both species concerned. Regarding the bioaccessibility it turns out that the fatty acids more bioaccessible on the salmon, are the polyunsaturated fatty acids with a percentage of 67.40% to 60.72% in raw and grilled and within these, docosahexanoic acid is the most bioaccessíble with a percentage of 92.30% in raw salmon and 60.22% on grilled salmon. In the meagre, the fatty acids more bioaccessible are the saturated, with 86.51% in raw and 56.28% in raw and grilled, thus revealing the consumption of salmon is more healthier

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Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia The black scabbard fish is greatly appreciated by the Portuguese population. However, it has generally high levels of mercury (Hg). The aim of this study was to determine the bioaccessibility of mercury in this species subjected to different culinary treatments (fried, grilled and steamed). The content of Hg and the proximate chemical composition were quantified in raw and cooked samples and the samples were also subjected to simulated digestive tract. The results revealed that the culinary treatments affected the chemical composition of black scabbard fish due to water loss and consequent concentration of other nutrients. All biometric parameters analyzed did not influence the Hg content. However, for culinary treatments, grilled fish showed higher levels of Hg, with 80% of samples above the limit set by the EU. The values of provisional tolerable weekly intake showed that fried, boiled and steamed black scabbard fish should be moderately eaten by pregnant women and children as they are particularly vulnerable to the toxic effects of Hg. A higher Hg bioaccessibility was observed in raw fish samples compared to cooked samples. Intestine was the digestion step where bioaccessible Hg reached the highest levels for absorption. The results indicate that frying cooking induce lower Hg bioacessibility, thus representing a lower risk for consumers.