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Optimising the quality of farmed barramundi Practical methods to enhance fillet quality

Optimising the quality of farmed barramundi Practical methods to enhance fillet quality. Ben Jones (JCU) Guy Carton (JCU) Sue Poole (DEEDI). Outline. Common quality issues for farmed barramundi Off-flavour, bland fillets. Preliminary research

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Optimising the quality of farmed barramundi Practical methods to enhance fillet quality

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  1. Optimising the quality of farmed barramundi Practical methods to enhance fillet quality Ben Jones (JCU) Guy Carton (JCU) Sue Poole (DEEDI)

  2. Outline • Common quality issues for farmed barramundi • Off-flavour, bland fillets. • Preliminary research • Presence and persistence of off-flavour compounds. • Off-flavour contamination of barramundi. • Current research program • Flavour recovery - Depuration. • Flavour enhancement – Finishing Diet.

  3. Off-flavour Taint • Unpalatable fish are termed ‘off-flavour tainted’ • Primarily Caused by two organic compounds: • Geosmin (GSM) • 2-methylisoborneol (MIB) • Metabolites of freshwater microbes (cyanobacteria).

  4. Bland/Flavourless Fillets • Farmed fish is often regarded as being bland. • Wild caught seafood is typified by a rich flavour/aroma. • Caused by bromophenols. • Produced by marine algae.

  5. Preliminary Research 2010 • Off-flavour tainting of barramundi • Presence and persistence of off-flavour compounds. • Explore the uptake of off-flavour compounds. • Define the nature of the taint for barramundi. • Investigate sensory threshold.

  6. Pond Sampling • Three ponds in North Queensland were sampled weekly. • Analysed for GSM/MIB at DEEDI labs, Brisbane.

  7. Uptake of GSM from Culture Water 0.0µg/l 0.8µg/l 1.72µg/l 2.29µg/l 3.98µg/l • Fillets analysed by GCMS. • Assessed by trained sensory panel.

  8. Pond Sampling Geosmin conc. (μg/l) Persistent concentration 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Time (weeks)

  9. Uptake of Geosmin GSM bio-accumulates at greater conc. than culture water. Flesh GSM conc. (μg/kg) Water GSM conc. (μg/l)

  10. Uptake of Geosmin Off-flavour Taint Overall Desirability Sensory score Sensory score GSM conc. in flesh (μg/kg) GSM conc. in flesh (μg/kg) • Sensory panel detected off-flavour taint at 0.74µg/kg.

  11. Sensory Assessment Overall Desirability Aroma After Taste Flavour

  12. Low Level GSM - 0.74 μg/kg

  13. High Level GSM - 4.47 μg/kg

  14. Findings • First time GSM confirmed in off-flavour tainting of barramundi. • Bio-accumulation of GSM in flesh - higher than exposure level. • Flesh GSM positively correlated with off-flavour tainting. • Sensory panel detected GSM at 0.74µg/kg.

  15. Research Program 2011-2013 • Efficacy of purging/depuration for barramundi. • Practices to accelerate depuration. • Formulate finishing diet to enhance flavour.

  16. Flavour Recovery by Depuration • Holding fish in taint free water to recover flavour quality. • Standard practice in oyster and silver perch industries. • Proven to work in Channel Catfish, Rainbow Trout, Tilapia.

  17. Assess the Efficacy of Depuration • The rate of uptake/depuration will be assessed at three concentrations. • Tainted (0.8 μg/l). • Mildly tainted (4 μg/l). • Grossly tainted (14 μg/l). • The level of off-flavour tainting will be assessed by: • GCMS analysis of fish flesh. • Sensory assessment. • This will tell us how long depuration is likely to take relative taint intensity.

  18. Assess the Efficacy of Depuration 0.0µg/l GSM Uptake – 48h Depuration – 14 days

  19. Preliminary Data • Fish exposed to 14.0μg/l for 48h at 25°C • Depurated for 2 weeks Flesh GSM conc. (μg/kg) 0 1 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Uptake/Depuration period (days)

  20. Compressing the Depuration Process • Temperature control will be assessed as a means of accelerating depuration. Temperature Metabolic rate Gill ventilation Accelerated depuration

  21. Flavour Enhancement by Bromophenol Addition • Can the flavour be enhanced? • Can off-flavours be masked? • Finishing diets will be developed with Ridley Aquafeeds: • For use on purged fish. • For use on unpurged fish.

  22. GSM was present at elevated at levels that will cause off-flavour taint and can be severe, exceeding 14µg/l. • GSM is rapidly taken up and stored by barramundi and causes off-flavour taint in barramundi. • When GSM is reduced in barramundi flesh, quality is improved. • Purging removes GSM and improves quality. • May be possible to mask off-flavours or enhance flavour with finishing diet. Summary

  23. Acknowledgements: Sue Poole (DEEDI) Steve Fuller (DEEDI) - Analytical procedures. Heather Smyth (DEEDI) - Advice and support - sensory assessment. Marty Phillips (Pejo enterprises) - Supply fish and general support of project. GFB Fisheries - Supply of fish and general support of project. Supported by Grants from:

  24. Identify Bromophenol Source • Algal powders. • Krill meal.

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