Effect of oxidation on the gel properties of porcine myofibrillar proteins and their binding abilities with selected flavour compounds

Protein oxidation (P-OX) is an innovative topic of increasing interest among meat researchers. Carbonylation is generally recognized as one of the most remarkable chemical modifications in oxidized proteins. In fact, the quantification of protein carbonyls by the dinitrophenylhydrazine (DNPH) method is the most common procedure for assessing P-OX in meat systems. Numerous studies have investigated the occurrence of protein carbonylation right after slaughter and during subsequent processing and cold storage of meat. However, the significance of protein carbonylation in meat systems is still poorly understood. Beyond their role as markers of protein oxidation, specific protein carbonyls such as α-aminoadipic and γ-glutamic semialdehydes (AAS and GGS, respectively) are active compounds that may be implicated in several chemical reactions with relevant consequences on meat quality. The formation of protein carbonyls from particular amino acid side chains contribute to impair the conformation of myofibrillar proteins leading to denaturation and loss of functionality. Recent studies also highlight the potential impact of specific protein carbonyls in particular meat quality traits such as water-holding capacity (WHC), texture, flavor and its nutritional value. As a truly emerging topic, the results from current studies provide grounds from the development of further investigations. The present paper reviews the current knowledge on the mechanisms and consequences of protein carbonylation in meat systems and aims to encourage meat researchers to accomplish further investigations on this fascinating research topic.

A simple and reliable method for the determination of surface hydrophobicity of nonsolubilized myofibrils (from pig M. longissimus dorsi) was developed and validated. This method is based on the interaction of the hydrophobic chromophore bromophenol blue (BPB) with myofibrillar proteins and the separation of free and bound BPB by centrifugation. The titration of bound BPB is performed by absorption spectroscopy, and the amount of bound BPB is considered as an index of protein hydrophobicity. Heating, which is known to increase protein hydrophobicity, was performed in order to validate this method. Fixation of BPB to myofibrils increased with heating time and temperature, strongly suggesting that it may be closely related to protein hydrophobicity.