Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/21911
Mackerel (Scomber scombrus), has in the resent years, become one of the most valuable fish spies in Iceland. Utilizing this recourse effectively has create many challenges for Icelandic fish processors. One of those challenges is stopping or diminishing the spoilage rate during frozen storage. The main objective of this project was to study seasonal variation and the influence of frozen storage (-27°C for up to 4 months) on quality degradation of headed and gutted (H/G) mackerel with emphasise on lipid oxidation and hydrolysis. Mackerel samples were collected five times, during the fishing season, from late June to beginning of September,all from the vessel Heimaey VE-1. Quality inspections and frozen storage of the samples were done at fish processing plant belonging to Isfelag HF. Quality inspections of the raw material and final products were carried out using the same methods used at this plant to reflect common practices in the Icelandic processing plants. Samples were stored in cold storage (-27°C +/- 2°C), used by Isfelag for all its products.
The biological stability of initial raw material was evaluated in term of quality parameters,TVB-N measurements conducted to evaluate the freshness and proximate content measured to clarify the seasonal variation of the mackerel. To explore the oxidation stability of themackerel, traditional methods including peroxide value (PV), thiobarbituric acid reactive substance (TBARS) and fluorescence method were used to determine the primary, secondary and tertiary lipid oxidation products respectively. Lipid hydrolysis (free fatty acid) was also measured to evaluate enzymatic activity.
Results showed, as confirmed by numerous other analyses, poor condition of the mackerel early in the season. Later on in the season biological stability improved considerable.
Peroxide values diminished during 4 month frozen storage for all samples except the one from the beginning of the season, late June. FFA, TBARS and fluorescene increased in all samples during 4 months frozen storage. Oxidation rate was higher in fish with higher lipid content(July/August) indicating that spoilage rate of the mackerel was more influenced by lipidcontent than biological stability during frozen storage at (-27°C +/- 2°C).
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