Biologia | Ambiente
Aki Giulia Bücher, 2003 | Lostallo, GR
Salmon eggs are rich in polyunsaturated fatty acids (PUFAs) such as alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are essential for human health. However, the eggs are often thrown away. This work focused on creating a food product containing salmon eggs and therefore being a source of PUFAs. During the production process, attention was put on preventing fatty acids oxidation, which causes off-flavors formation. Data obtained from the nutritional analysis have shown, that a high content of fatty acids and other nutritional values, such as proteins and micronutrients were present in the product and the best storage environment to prevent fatty acids oxidation, is a dry one. This work has demonstrated that a food by-product can be reused and can contribute to a complete nutritional diet.
Atlantic salmon is well known to be a fish rich in omega-3 PUFAs. Studies have shown that omega-3 PUFAs such as EPA and DHA are important for human health and cognitive development. Salmon’s eggs, head, skin and organs are rich in these essential substances, but are usually not eaten. This scientific research aims to recognize the values of essential fatty acids and other nutritional values, such as proteins and minerals, in salmon roe and then use them to prepare a culinary product source of PUFAs.
The salmon roe was supplied by Swiss Alpine Fish and marinated to reduce the typical taste and smell of raw eggs. Ingredients such as carrots and rosemary were added due to their aroma and antioxidant properties. To produce the salmon roe crackers, the ingredients were mixed, shaped and dried in the oven, at temperatures lower than 50 °C, to avoid fatty acids oxidation. The analysis measured the contents of water, protein, fatty acids, minerals, carbohydrates and fiber in both the eggs and the crackers. A shelf-life test of the culinary product under different storage conditions was conducted daily, during a period of two months, followed by sensorial tests.
The results of the analysis showed a high content of fatty acids, especially polyunsaturated fatty acids, and other nutrients such as carbohydrates, proteins, minerals and micronutrients in the culinary product. During the drying process, there was an oxidation of 0.68 g out of 1.95 g of DHA and 0.05 g out of 0.6 g of EPA. The best conservation method was in a dry environment with humidity of 30-40 % and temperature of 21-24 °C, in a closed container or a bag under vacuum.
In the culinary product was present a high amount of carbohydrates, including fiber; this is due to the use of other ingredients such as flour and carrots. A partial lipids oxidation occurred, DHA oxidated 0.68 g out of 1.95 g and EPA oxidated 0.05 g out of 0.6 g. DHA oxidated more than EPA, probably because of the chemical structure of omega-3 fatty acids that makes them chemically unstable, resulting in an extreme vulnerability to heat even at very low temperatures. However, at the chosen temperature (50 °C) the risk of microbial growth is not prevented. Moreover, under these conditions, the crackers are only dried and not cooked (no starch gelatinization), therefore digestibility is probably very limited. These problems can be overcome by using other methods, such as a higher temperature of the oven. The storage is better in a dry environment in a container or a vacuum bag, which can reduce the contact with humidity and oxygen, so that the shelf life of the product is longer.
It is demonstrated that salmon roe as a by-product can be reused to create a nutritious food product. This product is enjoyable by every age group. Cooking at higher temperatures such as 200 °C for 10 min is one of the best choices to elaborate the product. The storage of this product has been demonstrated through a sensorial test to be better and to have a longer shelf life when it is in a dry environment with 30-40 % of humidity and 21-24 °C of temperature in a container or a bag under vacuum.
Valutazione del lavoro espressa dall’esperta
Aki ha svolto un lavoro di ricerca innovativo, su un tema rilevante ed attuale come il riutilizzo di scarti alimentari. Il suo approccio sistematico le ha permesso di sviluppare un nuovo prodotto alimentare, tenendo conto di diversi fattori chiave per l’industria alimentare come il valore nutrizionale, la stabilità ossidativa durante la shelf-life e la conservazione dell’alimento.
Il lavoro presentato è strutturato secondo un procedimento scientifico, tenendo ben presente la letteratura scientifica attuale sul tema presentato. I risultati sono espressi in modo chiaro ed esaustivo.
Premi speciali: Aldo e Cele Daccò – European Union Contest for Young Scientists (EUCYS) | Alfred Escher – ETH Student Project House
Bündner Kantonsschule, Chur