Title: Fish silage from side streams of processing factories as raw material for aquafeed.

Author(s): Aysha Aktar
Final project
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Supervisors: Sigurjon Arason , Marvin Ingi Einarsson


In this study, silage was produced from viscera of Atlantic Red fish using two organic acids, formic and lactic acid at two different temperature (25°C and 45°C) conditions. The changes in pH, hydrolysis, protein in soluble phase, amino acid compositions, and free fatty acid formation were analysed for untreated raw material and the fish silages. The temperature 45°C was used to accelerate the rate of hydrolysis and on day 5, heat treatment was done to inactivate the digestive enzymes for the rest of the storage. Formic acid silages were stabilized at pH 3.38 (25°C) and 3.26 (45°C) while lactic acid silages were found to be stable at 4.09 (25°C) and 4.12 (45°C) respectively. There was no sign of putrefaction in the silages during 5 weeks of storage. Aqueous or soluble phase was found to increase due to hydrolysis in both formic and lactic acid silages with time and the proportion was more in 45°C silages. The protein in soluble phase was observed to increase in all the silages than in the initial stage. However, it was proportionately more in lactic acid silages than in the formic acid silages. The essential amino acid tryptophan was found to be more in concentration in both formic acid and lactic acid silages (25°C) than in the untreated raw material. Free fatty acid content was observed to rise in the silages at the beginning before slowing down. The increase was proportionately more in the silages of 45°C which may be a direct influence of higher temperature.

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