On the origin of thaw loss: Relationship between freezing rate and protein denaturation

Abstract

The role of protein denaturation in formation of thaw loss is currently not well understood. This study investigated denaturation of myofibrillar and sarcoplasmic proteins of pork loins caused by freezingthawing in relation to freezing rate. Compared to fast freezing, slow freezing caused 28% larger thaw loss, decreased water-holding capacity of myofibrils and increased surface hydrophobicity, indicating more pronounced denaturation of myofibrillar proteins. We here propose a model: In slow freezing protons are concentrated in the unfrozen water resulting in reduced pH in proximity of structural proteins causing protein denaturation. In parallel, large ice crystals are formed outside of muscle fibers resulting in transversal shrinkage. In fast freezing small ice crystals trap protons and cause less severe protein denaturation and reduced thaw loss. Differential scanning calorimetry and tryptophan fluorescence spectra indicated sarcoplasmic protein denaturation in drip due to freezing-thawing. However, sarcoplasmic protein denaturation was independent of freezing rate.

Deep freezing to maintain the freshness of pork loin during long-term storage

“…In addition, many studies have analyzed factors affecting thawing loss, such as post-mortem aging, frozen storage, and thawing conditions (Añón and Calvelo, 1980 ; Kondratowicz et al, 2006 ). In this study, thawing loss of pork loin frozen at − 18 °C was higher than in samples frozen at − 60 and − 50 °C; this result was similar to the findings of Zhang and Ertbjerg ( 2019 ), which showed that slow freezing induced more thawing loss in pork than fast freezing due to protein denaturation, resulting in water loss in myofibrillar proteins. At deep-freezing storage temperatures, there was no significant difference between storage periods, with about 0.5% difference in thawing losses between two storage temperatures after 1 month.…”

Quality characteristics of shucked crab meat ( Eriocheir sinensis ) processed by high pressure during superchilled storage

“…HPP‐shucking can increase the hydration capacity of proteins and lead to the infiltration of water molecules in the protein core (Oliveira et al., 2017), which resulted in muscle to absorb the water that would be easier to leak out during storage (Yi et al., 2013). In addition, Zhang and Ertbjerg (2019) reported that the formation of thaw loss in pork loins muscle might be due to the denaturation of structural proteins caused by concentrated protons in the unfrozen water, as well as the transversal shrinkage of muscle fibers induced by large ice crystals during the freezing process. Besides, Duun and Rustad (2007) claimed that the drip loss of cod ( Gadus morhua ) fillets during storage might be ascribed to the increased proteolysis which resulted in a looser structure.…”

“…HPP-shucking can increase the hydration capacity of proteins and lead to the infiltration of water molecules in the protein core (Oliveira et al, 2017), which resulted in muscle to absorb the water that would be easier to leak out during storage (Yi et al, 2013). In addition, Zhang and Ertbjerg (2019)…”

The influence of the freezing rate on the physico-chemical properties of pork meat (M. Longissimus dorsi)

“…In the case of fast freezing and the formation of a large number of small crystals, the amount of water during defrosting is small. During slow freezing processes, the intracellular crystals become larger, which is accompanied by a significant increase in the amount of water released during meat defrosting (12,16). During the storage of meat, changes in the crystal structure of ice that are associated with changes in the protein state take place, and the intensity of these changes depends on the length of storage (17).…”

“…The water-binding capacity is an indirect measure of protein denaturation. Most authors believe that rapid freezing causes minor changes in proteins due to a shorter maximum crystallization interval of the tissue (16,22).…”