Siwen Xue

High-pressure effects on the molecular aggregation and physicochemical properties of myosin in relation to heat gelation

Myosin was extracted from the M. psoas muscle of rabbits, and dissolved in 0.6M KCl buffer (pH6.5). Effects of high-pressure (HP, 100 to 300MPa, 9min, 25°C) treatment on myosin solubility, molecular traits (molecular weight and morphology), flow behavior and strength of heat-induced myosin gels were studied and compared with the untreated controls. Myosin subjected to 200MPa HP treatment had lower solubility than samples treated at other pressures (P<0.05). Molecular dimerization and morphological swelling of myosin was observed using gel-permeation chromatography and atomic-force microscopy. Additionally, the shear-thinning behavior of myosin solutions (10mg/mL) was improved by HP treatment (≥200MPa), and a positive trend in gel-strength enhancement was inferred. It is postulated that significant morphological changes in myosin accounted for changes in its functional properties, by the influence of HP treatment on protein-protein and/or protein-water interactions. There is a relationship between molecular morphology and the coalescing behavior of myosin, since significant changes of both attributes were observed at pressures ≥200MPa.

Effect of pH-values on gelation properties of myosin extracted from high-pressure treated pre-rigor rabbit muscle

Myosin was extracted immediately from pre-rigor rabbit muscles (PRRMs) after high-pressure (HP) treatment (200 MPa, 25 °C for 15 s) to investigate the effect of pH (5.0, 5.5, 6.0, 6.5 and 7.0) on gel properties under the defined parameters. The water characteristics of the formed gel was modified as the pH altered. Improved water-holding capacity (WHC) was observed as the pH increased away from 5.5 and the highest value was reached at pH 7.0 (P<0.05). Assessment of rheological properties and secondary structures demonstrated that the thermal-induced aggregation of myosin after 50 °C was hindered at pH 6.5 and 7.0, and the unfolding of myosin conformational structures was intensified. Moreover, rapid exposure of buried amino groups in the temperature range between 40 °C and 70 °C occurred at pH 6.5 and 7.0, which contributed the formation of gel. These alternations give partial interpretation to the quality of gels obtained and verified the importance of monitoring the pH when applying HP treatment to the production of meat products.