Oyster preservation by high-pressure treatment

Area of Science:

• Food Science
• Microbiology
• Food Engineering

Background:

• Oysters are susceptible to microbial spoilage and quality degradation.
• Traditional preservation methods have limitations in maintaining oyster quality.
• High-pressure processing (HPP) is an emerging technology for food preservation.

Purpose of the Study:

• To evaluate the impact of continuous and pulsed high-pressure processing on oyster quality.
• To assess the effect of HPP on microbial load, chemical indicators, and texture.
• To compare the efficacy of continuous versus pulsed pressure treatments.

Main Methods:

• Oysters (purified and unpurified) were subjected to continuous or pulsed high-pressure treatment (400 MPa, 7°C).
• Microbial counts (total viable count, H2S-producing microorganisms, lactic acid bacteria, Brochothrix thermosphacta, coliforms, Salmonella spp.) were determined.
• Total volatile bases (TVB), pH, and shear strength were measured to assess quality.
• Samples were stored at 2°C for 41 days, with regular quality assessments.

Main Results:

• High-pressure processing reduced target microorganisms by up to 5-log units.
• Microbial reduction remained stable during 41 days of refrigerated storage.
• Pressurized oysters exhibited higher shear strength and stable pH compared to controls.
• Increased total volatile bases were observed in non-pressurized samples, indicating spoilage.
• Pulsed pressure treatment offered no significant advantage over continuous pressure treatment.

Conclusions:

• High-pressure processing is effective in reducing microbial load and preserving oyster quality.
• HPP extends the shelf life of oysters by inhibiting microbial growth and maintaining texture.
• Both continuous and pulsed pressure treatments are viable for oyster preservation, with no clear benefit of pulsed over continuous application.