The effect of high‐pressure treatment on bovine intramuscular connective tissue was investigated under various pressures (0.1 to 500 MPa) at 8 °C for 5 min. Shear force value, heat solubility of collagen, and structural changes of pressurized intramuscular connective tissues were evaluated. High hydrostatic pressure tenderized bovine intramuscular connective tissue as well as meat. The heat solubility of collagen increased (P < 0.05) with high pressure, which indicates a reduction of collagen thermal stability. However, high pressure could not degrade collagen molecules by sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis. Collagen‐derived peptide analysis also suggested that high pressure could not degrade the molecular structure of collagen, but could dissociate the collagen fibers or fibrils into fibrils or molecules. Histological study showed that high pressure induced structural weakening of intramuscular connective tissue, especially perimysium.

Porcine glycolytic enzyme, glyceraldehyde 3-phosphate dehydrogenase (G3PD) was prepared effectively by a combination of ethylene diamine tetra-acetate (EDTA) pretreatment and affinity purification. After salting out of porcine sarcoplasmic proteins (SP) with ammonium sulfate at 75% saturation, the obtained supernatant (SP-f3) was treated with EDTA, leaving G3PD in the supernatant (G3PD-E) and most other SPs in the precipitate. At that time, the separation of G3PD-E required more than 20 mmol/L EDTA. G3PD-E was then subjected to affinity purification by batchwise method using blue-sepharose CL-6B, and purified G3PD (G3PD-AP) was obtained using 2 mol/L potassium chloride (KCl) as an eluent. Texture analysis showed that the hardness, adhesiveness and gumminess of the myofibril gel at 0.2-mol/L NaCl increased with the addition of G3PD-AP. Scanning electron microscopy revealed that the G3PD-AP reinforced the gel network of the myofibril. However, scanning electron micrograph analysis showed that the network-structure of the gel by the addition of G3PD-AP developed in a different manner from that by adding 0.6 mol/L NaCl. These results showed that glycolytic enzyme, G3PD, contributes to the improvement of the rheological properties of meat products.

Previously, it was clarified that myofibril gelation was enhanced by the basic protein glyceraldehyde 3-phosphate dehydrogenase (GPD). In this study, the mechanism of the gel-enhancing action of GPD to myosin B was evaluated through the study of the surface properties of GPD. GPD and myosin B were prepared from pork loin. Succinylated GPD (S-GPD) was successfully prepared without any loss of solubility at a weight ratio (succinic anhydrate to GPD) of 1.0. Though gelation of myosin B alone required a minimum protein concentration of 4.0% (w/v), the addition of GPD enhanced the gelation of myosin B at a concentration of 3.5% (w/v). Furthermore, GPD increased the gel strength drastically at concentrations above 4.5% (w/v). On the other hand, the addition of S-GPD did not improve the gelling property of myosin B. SDS-PAGE showed molecular interaction between GPD and myosin B, but not between S-GPD and myosin B. However, in the case of GPD, the GPD band became insoluble under coexistence of GPD with myosin B. Meanwhile, the myosin heavy chain was partially soluble. Furthermore, actin and GPD bands became thicker in the insoluble fraction after mixing of G-actin and GPD. These results indicate that positive charges on the surface of GPD are necessary to enhance the gelation of myosin B.

In this study, the effect of glyceraldehyde 3-phosphate dehydrogenase (G3PD) on the molecular state of porcine myofibrils was investigated by observing the structural changes in myosin and actin in myofibrils using phase-