Influence of Aging and Salting on Protein Secondary Structures and Water Distribution in Uncooked and Cooked Pork. A Combined FT-IR Microspectroscopy and ¹H NMR Relaxometry Study

Abstract

Fourier transform infrared (FT-IR) microspectroscopy and low-field (LF) proton NMR transverse relaxation measurements were used to study the changes in protein secondary structure and water distribution as a consequence of aging (1 day and 14 days) followed by salting (3%, 6%, and 9% NaCl) and cooking (65 degrees C). An enhanced water uptake and increased proton NMR relaxation times after salting were observed in aged meat (14 days) compared with nonaged meat (1 day). FT-IR bands revealed that salting induced an increase in native beta-sheet structure while aging triggered an increase in native alpha-helical structure before cooking, which could explain the effects of aging and salting on water distribution and water uptake. Moreover, the decrease in T2 relaxation times and loss of water upon cooking were attributed to an increase in aggregated beta-sheet structures and a simultaneous decrease in native protein structures. Finally, aging increased the cooking loss and subsequently decreased the final yield, which corresponded to a further decrease in T2 relaxation times in aged meat upon cooking. However, salting weakened the effect of aging on the final yield, which is consistent with the increased T2 relaxation times upon salting for aged meat after cooking and the weaker effect of aging on protein secondary structural changes for samples treated with high salt concentration. The present study reveals that changes in water distribution during aging, salting, and cooking are not only due to the accepted causal connection, i.e., proteolytic degradation of myofibrillar structures, change in electrostatic repulsion, and dissolution and denaturation of proteins, but also dynamic changes in specific protein secondary structures.

Gelling properties of myosin as affected by L-lysine and L-arginine by changing the main molecular forces and microstructure

“…This was consistent with a previous description.- [21,26] An increase in PT 22 was also observed in chicken salt-soluble protein gel [19] and chicken actomyosin in the presence of Arg. [18] Increases in the solubility of myosin [12,13] and formation of the gel with fine pores may contribute to the increased PT 22 .…”

Physicochemical changes of myofibrillar proteins during processing of Cantonese sausage in relation to their aggregation behaviour and in vitro digestibility

“…Significant changes in intensity caused by salting and processing were observed. The intensity decreased primarily during the 36 h, then increase gradually during the last 36 h. Salting and heating reduced the intensity of the band at 1653 cm À1 (Wu et al, 2006). Fig.…”

Comparison of thawing assisted by low-intensity ultrasound on technological properties of pork Longissimus dorsi muscle

“…Previous studies evidence a correlation between cooking losses and the ageing process. Shanks et al (2002) showed that muscle loses ability to preserve humidity with ageing, while Wu et al (2006) conclude that higher cooking losses in aged meat can be due to protein aggregation after ageing. Furthermore, Straadt et al (2007) noticed that extended ageing associates with the growth of cooking losses while microstructural alterations occurring in ageing result in severe structural alterations.…”