Mimicking myofibrillar protein denaturation in frozen-thawed meat: Effect of pH at high ionic strength.

• Freezing-thawing cycles of pork decreased water-holding capacity of myofibrils. • A 160 kDa myosin-4 fragment appeared in SDS-PAGE following freezing-thawing cycles. • Water-holding of myofibrils decreased after exposure to low pH-high ionic strength. • Low pH-high ionic strength exposure mimics myofibril denaturation in freezing. • A model is proposed linking low pH-high ionic strength to protein denaturation. This study aims at providing new insight on protein denaturation in freezing-thawing. Freezing-thawing minced pork reduced water-holding of myofibrils and increased surface hydrophobicity. One additional freezing-thawing cycle at slow freezing rate caused appearance of a 160 kDa myosin-4 fragment in SDS-PAGE, further decreased water-holding of myofibrils and increased surface hydrophobicity. Fresh minced pork was exposed to either high salt (2 M KCl) only or high salt with lower pH to mimic conditions in freezing. Exposure to high salt only increased water-holding of myofibrils and hence did not reproduce myofibrillar protein changes in freezing. Exposure to combinations of lower pHs and high salt decreased water-holding and increased surface hydrophobicity, suggesting myofibrillar protein denaturation occurred by a comparable mechanism as in freezing-thawing. We propose that exposure to decreased pH combined with high solute concentrations in the unfrozen water of frozen meat is the primary cause of myofibrillar protein denaturation in frozen-thawed meat. [ABSTRACT FROM AUTHOR]