lautnusantara.com Storage, especially at inappropriate temperatures or for too long, will significantly degrade the physical and chemical quality of barramundi (Lates calcarifer) fillets. This quality decline is generally caused by the activity of microorganisms, enzymatic reactions, and chemical processes such as fat oxidation.
Changes in the Physical Quality of Barramundi Fillets During Storage
The main physical quality parameters that experience changes include:

1. Appearance (Organoleptic):

• Fresh fillets will have a bright creamy white or slightly reddish flesh color.
• During storage, the color will become pale, dull, and slimy.

2. Texture:

• The initial texture of the fillet should be firm and firm (high hardness).
• The texture will soften (become mushy) over time due to protein degradation by enzymes and microorganisms.

3. Odor:

• The initial odor is fresh, typical of fish.
• During storage, the odor will change to an unpleasant sour, putrid, or ammoniacal odor, primarily due to the formation of volatile compounds.

4. Water Holding Capacity (DAP) and Drip Loss:

• The water-holding capacity of fish meat decreases.
• Drip loss (liquid escaping from fillets) increases, especially during frozen storage where thawing is not complete, resulting in reduced fillet weight and texture degradation.

Changes in Chemical Quality of Barramundi Fillets During Storage
Chemical changes occur as components in fish meat degrade, such as:

1. Total Volatile Base Nitrogen (TVB-N) and Trimethylamine (TMA):

• TVB-N and TMA values ​​are key indicators of chemical spoilage in fish.
• These values ​​increase sharply with storage duration and temperature. These compounds result from the decomposition of protein and other nitrogen compounds by specific spoilage bacteria (Specific Spoilage Organisms - SSOs).
• Barramundi fillets can be considered to have begun to spoil when the TVB-N value exceeds 25 mg N/100 g (although this value can vary).

2. pH:

• After fish die, the meat's pH initially drops, then increases (becomes more alkaline) during storage. This increase in pH is caused by the accumulation of alkaline compounds such as ammonia and amines (including TVB-N).

3. Moisture Content:

• In general, the moisture content is relatively high (60-84%). During frozen storage, the moisture content does not change significantly, but its form changes to ice crystals. High drip loss can affect the effective moisture content remaining in the meat.

4. Fat Oxidation (TBARS):

• The oxidation reaction of polyunsaturated fatty acids (PUFAs) increases, indicated by higher TBARS (Thiobarbituric Acid Reactive Substances) values. This oxidation triggers the development of rancid odors and flavors.

5. Free Amino Acids (AAB):

• Significant changes in the concentration of several PUFAs (such as isoleucine, leucine, methionine, and phenylalanine) occur due to catabolism and deamination triggered by enzymes and microbes, which also contributes to the decline in flavor and odor.

Vacuum packaging and the use of natural coatings (e.g. chitosan or cinnamon essential oil) can help extend the shelf life of Barramundi fillets by reducing microbial contamination and oxidation.

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