Improvement of the gelling properties of meat emulsion gel by the addition of porcine sarcoplasmic proteins

The effects of porcine sarcoplasmic proteins (SP) on the physicochemical properties of meat emulsion gel were examined. Meat emulsion was prepared from water‐washed pork meat (WWM), corn oil and SP. Whole SP (W‐SP) enhanced the breaking stress of the WWM emulsion gel as well as other animal proteins in the presence of 0.2 mol/L NaCl. The breaking stress of the emulsion with W‐SP increased with an increase in corn oil content. Furthermore, this tendency was more noticeable at a lower NaCl concentration (0.15 mol/L) rather than at 0.45 mol/L NaCl. Ammonium sulfate (AS) treatment fractionated W‐SP into three portions (SP‐f1, SP‐f2 and SP‐f3), which were the precipitates at 0–50% and 50–75% AS saturation and the supernatant at 75% AS saturation, respectively. The fractions SP‐f2 and SP‐f3 increased the gel strength more than W‐SP. In particular, the fraction SP‐f3 increased the gel strength approximately 10‐fold compared to the control. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analysis showed that SP‐f3 had several kinds of proteins and a main protein with a molecular mass of 35 kDa, which corresponded to glyceraldehyde 3‐phosphate dehydrogenase. These results indicate that the influence of SP should not be ignored when processing of low‐salt meat products and the fraction SP‐f3 has a gel‐enhancing factor for myofibrillar proteins.     

Simple method for isolation of glyceraldehyde 3‐phosphate dehydrogenase and the improvement of myofibril gel properties

Porcine glycoliytic 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.