lautnusantara.com The main influence of filleting methods on the yield and quality of Red Emperor fish (Lutjanus sebae or Lutjanus spp.) depends heavily on the timing of filleting relative to the rigor mortis phase of the fish, as well as the skill of the workers.
The following is a summary of these influences:
Influence on Yield
Yield is the percentage of fillet meat produced from the total weight of the whole fish.
1. Skill and Equipment: The skill of the operator and the sharpness of the knife directly affect how efficiently the meat is separated from the bones. The more skilled the operator, the less meat remains on the bones, resulting in higher yield.
2. Rigor Mortis Phase: The processing time relative to rigor mortis has a significant impact:

• Post-rigor filleting (after the fish has passed the stiff phase): This method tends to produce higher fillet yield compared to pre-rigor filleting. This is because the fish muscles have relaxed or undergone natural tenderization, making them easier to cut without damaging the meat structure.
• Pre-rigor filleting (immediately after death before rigor mortis): Although it can provide high initial yield, fillets produced immediately after death (and then chilled or frozen) are at risk of greater length contraction and potential structural damage if freezing is done before rigor mortis is complete.

In general, the yield of Red Snapper (Lutjanus spp.) fillets processed in the industry ranges from an average of 43% to 48% of the whole fish weight after filleting and trimming.

Impact on Meat Quality
The quality of fillet meat is influenced by how the filleting method minimizes physical and biochemical damage:

• Drip Loss (Mass/Distilled Water Loss): This is the water that comes out of the fillet, indicating a loss of water and nutrients, which has a negative impact on texture and yield. Post-rigor filleting has been shown to result in less water loss (drip loss) after freezing and thawing.
• Gapping (Separation of Meat Fibers): Fillets processed while the muscle is still undergoing contraction (rigor mortis) and experiencing cold shock (sudden cooling immediately after death) are at risk of gapping or the formation of gaps in the meat fibers. Pre-rigor filleting and immediate freezing can cause significant gapping after thawing.
• Texture and Contraction: Fillets processed post-rigor show less fillet length contraction, helping to maintain the natural shape and texture of the fillet.

It is important to note that pre-fillet handling (such as the capture process and handling of fish immediately after death) also greatly determines fillet quality. Fish that experience high stress before death will have a rapid post-mortem metabolic rate, which can exacerbate drip loss and gapping regardless of the filleting method.
 

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