Effect of pH on the rheological and structural properties of gels of water-washed chicken-breast muscle at physiological ionic strength

Adjustment of pH from 6.4 to neutrality improved gelling ability and water- holding capacity of twice water-washed, minced chicken-breast muscle signif icantly at physiological ionic strength, at which the majority of the myofi brillar proteins, including myosin, are not soluble. A strain value of 2.2 was obtained at neutral pH. Myofibrils were the main components of the gel network at both pH 6.4 and 7.0; however, the myofibrillar distribution vari ed with the pH value. At pH 6.4, myofibrils formed a network of localized a ggregates leaving large voids between, whereas at neutral pH, an evenly dis tributed network of myofibrils was formed. In addition, at neutral pH, a ne twork of fine strands was found within the network of myofibrils. The netwo rk was much less developed at pH 6.4. The thin and thick filaments within e ach myofibrillar structure were disorganized at both pH values. The intramy ofibrillar spaces were larger at neutral pH than at pH 6.4. It was proposed that adjustment of pH to neutrality increased electrostatic repulsion lead ing to a more even distribution of the myofibrillar proteins, a key factor responsible for the improved gel strength and water-holding capacity.