Title: Analysing physical-chemical parameters for processing dried mackerel and cod products for Cabo Verde.

Final project
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Supervisors: Asbjorn Jonsson


This study focuses on the drying process of fish heads from different Icelandic species (lean and fat fish) which can be used in the Cabo Verdean market. The effects on sensory attributes (odour, appearance, flavour and texture), physico profile (pH, aw, weight reduction and Total Volatile Basic Nitrogen (TVB-N)) and chemical composition (moisture, protein, sodium chloride and fat) were evaluated between heads of the Atlantic mackerel (Scomber scombrus) and Atlantic cod (Gadus morhua) before and after drying. This experience also allowed to develop a standard procedure and a processing guideline for the drying of fish in Cabo Verde. Cod and mackerel heads were dried following the Icelandic method of utilising geothermal energy in a drying chamber. During the drying the temperature, humidity and drying velocity were measured from the chamber readings. The test results showed that different factors, such as humidity, the rate and extent of water loss, the salt content, the time, the heat treatment temperature and the pH, can change the composition and quality of the final product. The protein, lipid content, TVB-N and salt content increased significantly after the drying process for both species. The protein in the cod head was 14.3% to 59.4% before and after drying and the mackerel head was 13.3% to 28.5% before and after drying. The lipid content of the cod head was 0.35% to 1.9% before and after drying, the mackerel head was 22.6% to 49.2% before and after drying. The TVB-N for the cod head was 13.05 mg N/100g to 218.1 mg N/100g before and after drying, the mackerel head was 20.2 mg N/100g to 27.9 mg N/100g before and after drying. Salt was used only for mackerel heads and was 1.07% before and 4.4% after drying. Sensory evaluation of the fatty fish after drying detected a strong rancid odor due to the high fat content of the mackerel. In the lean fish, blood was found in the flesh of the heads, which eventually accelerated the deterioration of some samples. However, in samples that had no blood, the flavour resembled traditional Icelandic dry fish.

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