Frozen storage procedures for salmon and plaice samples: Nutrient composition and implications for preservation

Area of Science:

• Food Science
• Analytical Chemistry
• Nutritional Biochemistry

Background:

• Long-term frozen storage of fish samples is crucial for subsequent nutrient analysis.
• Degradation of vitamins, amino acids, and fatty acids can occur during frozen storage.
• Optimizing storage conditions is essential for accurate analytical measurements.

Purpose of the Study:

• To evaluate freeze-drying as a method to stabilize fish muscle homogenates for long-term frozen storage.
• To compare nutrient stability in freeze-dried versus wet-frozen fish samples under different frozen storage temperatures (-20°C and -80°C).
• To determine the optimal storage conditions for preserving key nutrients in fish muscle homogenates for up to one year.

Main Methods:

• Fish muscle homogenates (Atlantic salmon and European plaice) were prepared and divided into wet-frozen and freeze-dried groups.
• Samples were stored at -20°C and -80°C for up to 12 months.
• Vitamins, amino acids, and fatty acids were quantified at baseline and at 1, 3, 6, and 12 months using validated analytical methods.

Main Results:

• Freeze-drying significantly stabilized amino acids, vitamins, and fatty acids in both fish species when stored at -20°C for up to one year, outperforming wet-frozen storage.
• Storage at -80°C did not offer additional preservation benefits for freeze-dried samples compared to -20°C.
• For wet-frozen samples, -80°C storage was recommended for optimal preservation over one year, though -20°C also showed good preservation for several nutrients.

Conclusions:

• Freeze-drying followed by frozen storage at -20°C is a viable and cost-effective strategy for preserving fish muscle homogenates for at least one year prior to nutrient analysis.
• This approach ensures the stability of amino acids, fat-soluble vitamins, water-soluble vitamins, and fatty acids.
• Freeze-drying may enhance extraction efficiency or alter dry weight, potentially leading to slightly increased measurements of certain fatty acids in lean fish like plaice.