1. Effect of frozen storage time and temperature on quality of Atlantic mackerel (Scombrus scomber) Paulina E. Wasik PhD student Matís ohf. & University of Iceland Dr. Magnea G. Karlsdottir Research Group Leader Matís ohf. Dr. Hordur G. Kristinsson Chief Science Officer Matís ohf. & Adjunct Associate Professor University of Florida Sigurjon Arason Chief Engineer Matís ohf. & Professor University of Iceland

2. © Matís 2015 2 Atlantic Mackerel (Scombrus scomber)  Atlantic mackerel (Scombrus scomber) is known from widespread relocations and has been discovered in Icelandic waters since 2006 and gained great economical importance  Frozen storage of the mackerel is main long term preservation method  Main quality changes of the seafood occurs due to lipid oxidation Source: Statistics Iceland Decrease in: Emulsifying activity Proteins solubility Generation of: Hydroperoxides Aldehydes Dimers Trans fatty acids Millard type products Losses in: PUFA Vitamins A, D, E Antioxidants Off odor Off flavor Discoloration Undesirable texture Sensory aspects Nutritional values Technological Toxicity

3. © Matís 2015 3 Factors affecting lipid oxidation development during frozen storage  Seasonal variation  Geological variation of fishing grounds  Fish processing of raw material  Freezing methods  Frozen storage time  Frozen storage temperature

4. © Matís 2015 4 Main methods  Lipid oxidation: PV (1°), TBARS (2°), and fluorescence intensity (3°)  Enzymatic activity: FFA  Physical and chemical properties: Colour, drip, water content, lipid content, lipid composition  Alternative methods: NIR spectroscopy, colorimetric  Quality evaluation: texture, appearance, gaping, blood spots, peritoneum deterioration

5. © Matís 2015 5 The effect of storage temperature on fish quality and stability of lipids -18 °C -25 °C Free fatty acids (FFA) level were significantly higher for samples stored at -18˚C than -25˚C

6. © Matís 2015 6 The effect of storage temperature on fish quality and stability of lipids Primary oxidation products were at significantly higher level for samples stored at -18˚C than -25˚C

7. © Matís 2015 7 The effect of storage temperature on fish quality and stability of lipids Secondary oxidation products were at significantly higher level for samples stored at -18˚C than -25˚C

8. © Matís 2015 8 Effect of different storage temperature on fish muscle quality -25 ˚C, 12m -18˚C, 12m

9. © Matís 2015 9 Conclusions  Different pathways of lipid degradation  Storage temperature and time are important factors regarding oxidative stability of frozen fish products  Recommended to store at -25 °C instead of -18 °C

10. Acknowledgment