Protein Solubility and Textural Changes in Heated Bonito Meat: Including Low-temperature Cooking Conditions

Abstract

This study examined the effects of temperature and duration of heating, including low-temperature cooking conditions, on the texture and protein solubility of bonito (Katsuwonus pelamis) meat. Raw bonito was heated at 65℃ or 85℃ for 15 or 60 min, and changes in weight, moisture, texture, and protein composition were assessed. Higher temperatures caused more weight loss and a harder texture. Protein analysis showed that heating reduced the water-soluble and salt-soluble fractions, while the alkali-soluble fraction rose to 93-95%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the raw samples contained water-soluble sarcoplasmic proteins, including glycolytic enzymes, and salt-soluble myofibrillar proteins such as actin and myosin. After heating, most of these components shifted to the alkali-soluble fraction. At 65℃, a distinct 35 K band, identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was found in the water-soluble fraction and drip supernatant, but was absent at 85℃. This finding suggests that GAPDH is more heat-stable than other glycolytic enzymes.