Effect Of Five Plant Polyphenols On Structure And Gel Properties Of Pork Myofibril Protein At Oxidation Conditions

Protein oxidation often occurred during process and storage of meat and meat products that will affect the structure and functional properties of protein.Protein oxidation is one of the main causes of corruption and deterioration of meat and meat products.Therefore,it is necessary to find methods to reduce protein oxidation.Recently,food polyphenols and proteins interactions are one of the focuses in the Food Chemistry field.Protein is an important component in foods and its structure and functional properties display an important impact on food quality.Plant polyphenols possess the antioxidant and antibacterial activities.The plant polyphenols could bind to the proteins via hydrogen bonds,hydrophobic and covalent bonds and have affects on the protein characteristics.In the present paper,myofibril protein(MP)was extracted from pork longissimus dorsi.Fenton oxidation system(10?mol/L FeCl3,100 ?mol/L Vc and 1 mmol/L H2O2)of MP was established.The gallic acid,catechin,genistein,rutin and quercetin(10,50,100 and 150 ?mol/g protein)was used as antioxidants and added into the system.The inhibition effect of polyphenols on protein oxidation and changes of amino acid residue side-chain groups were investigated.The different effects of polyphenols on MP structure and the extent of crosslinking between polyphenols and proteins were also investigated.Futhermore,the relationships between protein gel properties and the interactions of the polyphenols and protein were illustrated.The main conclusions are as follows:1.Gallic acid,catechin,genistein,rutin and quercetin were added to the pork MP at oxidation conditions and the carbonyl content was decreased.High concentrations of allic acid,rutin and quercetin,100 ?mol/g catechin and 10 ?mol/g genisteing showed the best inhibition effects.Compared with the oxidized control group,gallic acid,catechin(50,100 and 150?mol/g),genistein,quercetin and rutin decreased the sulphydryl content to different extent.Catechin and the lower concentrations of gallic acid,rutin and quercetin reduced the surface hydrophobicity.Compared with the control group,the addition of genistein(50 and 150 ?mol/g)decreased the surface hydrophobicity.Compared with the oxidized control group,except to 100?mol/g genistein and 150?mol/g quercetin,other different concentrations of polyphenols increased the ?-helical content.Except to 10?mol/g gallic acid and 150 ?mol/g quercetin,the protein with other concentrations and types of polyphenols had higher tryptophan fluorescence intensity than control which indicated that the polyphenols could protect the tryptophan.2.Compared with the oxidized control group,the addition of gallic acid,catechin,genistein,rutin and quercetin decreased the protein solubility.With the increase concentrations of gallic acid,catechin and genistein,the particle size increased gradually,but the particle size moving toward smaller gradually with the increase concentrations of rutin and quercetin.The gallic acid and catechin showed no effect on the intensity of myosin heavy chain(MHC).However,the addition of genistein,rutin and quercetin,the intensity of MHC decreased.The intensity of actin almost showed no loss at low and medium concentrations of genistein,rutin and quercetin(0,10 and 50 ?mol/g),but decreased at high concentrations.The crosslinking interaction between gallic acid,catechin,genistein,rutin and quercetin and proteins were reducible.3.The effect of polyphenols on gel properties of MP at oxidation conditions was investigated.Oxidative protein gel network structure was weaker,and the form ability of gels was decreased.With the increase of gallic acid and catechin concentration,gel strength and water-holding capacity were decreased,whiteness of gel was increased slightly and microstructure was destroyed.At higher concentrations(50,100 and 150?mol/g),the typical characteristics of rheological properties were lost.Compared with the control group,the addition of gallic acid and catechin(50,50 and 150 ?mol/g)increased the free-water.With the increase of genistein,rutin and quercetin concentration,the gel strength,rheological properties and microstructure of MP can be improved;a part of the free-water was translated to immobilized water;and rutin and quercetin decreased the whiteness of gel;genistein increased first and then decreased the gel whiteness.Therefore,the interactions between MP and polyphenols have an impact on the protein gel properties which is related to the type and concentration of polyphenols.