Raman spectroscopic study of changes in fish actomyosin during setting

Area of Science:

• Biochemistry
• Food Science
• Protein Chemistry

Background:

• Surimi processing relies on the thermal gelation of fish actomyosin (AM).
• Understanding the low-temperature gelation ('setting') mechanism is crucial for surimi quality.
• Actomyosin structure dictates its functional properties in gel formation.

Purpose of the Study:

• To investigate structural changes in actomyosins from different fish species during low-temperature setting.
• To elucidate the role of protein conformation in surimi gelation at 40°C.
• To identify factors preventing gelation in certain fish species.

Main Methods:

• Raman spectroscopy was used to analyze structural changes in actomyosins.
• Actomyosins were isolated from tilapia, lemon sole, ling cod, and rock fish.
• Proteins were subjected to heating at 40°C to induce gelation.

Main Results:

• Lemon sole, ling cod, and rock fish AMs showed alpha-helix unfolding and hydrophobic residue exposure, facilitating gelation.
• Hydrophobic interactions among AM molecules were observed during the setting process.
• Tilapia AM exhibited a stable alpha-helical structure, resisting gelation at 40°C.
• The gauche-gauche-trans (g-g-t) conformation was frequent in disulfide bonds of set gels.

Conclusions:

• Actomyosin (AM) alpha-helix unfolding is a prerequisite for low-temperature gelation ('setting') in surimi.
• Species-specific differences in myosin's alpha-helical stability influence gelation capability.
• Understanding these conformational changes can optimize surimi processing and product development.