Effects Of NaCl And Three Polyphenols On The Structure And Gel Quality Of Chicken

Spices and Chinese herbs are often used as condiments in traditional meat processing to improve the quality of meat products and prolong the shelf life of food.Among them,Chlorogenic Acid(CA),Tannic Acid(TA)and Gallic Acid(GA)are common and representative water-soluble polyphenols,which have good bioaccessibility and reacts easily with meat protein.Na Cl,as the most common food condiment,can affect the interaction between other substances and muscle protein during meat processing.Myofibrillar Proteins(MP),the important components and main structural proteins of meat products,contain all essential amino acids required by human body and determine the quality of meat products to a large extent.Therefore,it is of great significance to systematically investigate the combined effects of salt and polyphenol on MP structure and gel quality to optimize traditional meat processing technology and promote the development of meat industry.In this paper,the mechanism of three polyphenols react with MP was investigated.The effects of three polyphenols on the structure of MP under different Na Cl conditions were analyzed.The effects of three polyphenols on gel quality under high salt(0.6 mol/L Na Cl)and low salt(0.2mol/L Na Cl)conditions were investigated,and the following conclusions were mainly drawn:(1)The interaction mechanism between MP and polyphenols was explored by multi-spectral means combined with changes in MP aggregation behavior.The results showed that CA and GA had no significant effect on MP surface hydrophobicity and solubility,while MP’s D4,3 could be increased.The addition of TA significantly reduced MP’s solubility and surface hydrophobicity,and significantly increased particle size.The results showed that the three polyphenols could promote MP to stretch,and TA had the strongest crosslinking ability with MP.The ultraviolet results showed that the addition of three polyphenols decreased the absorbance value of MP at 208 nm and 280 nm,because polyphenols could expose the amino residues in MP to the hydrophilic environment,and the amide group underwent pi→pi* transition,resulting in the decrease of absorbance and the change of the tertiary structure of MP.The results of thermodynamic analysis and circular dichroism showed that the polyphenols were combined with MP by static quenching,and the α helical structure of MP was reduced by forming hydrogen bond with MP.Among the three kinds of polyphenols,TA and MP had the strongest covalent binding ability.(2)The effects of 0.2 mol/L Na Cl,0.4 mol/L Na Cl and 0.6 mol/L Na Cl on MP structure were investigated.It was found that the surface hydrophobicity of MP increased with the increase of salt concentration,and the salt concentration exposed the reactive sulfhydryl group in MP.Increasing the proportion of the transformation to disulfide bond resulted in the decrease of MP’s total sulfhydryl group.Three polyphenols(5mg/g proteins)can enhance MP’s surface hydrophobicity at 0.2 mol/L Na Cl and 0.4 mol/L Na Cl,but MP’s surface hydrophobicity does not increase or even decrease(CA)at 0.6 mol/L Na Cl concentration.This may be due to the hydrophobic interaction between CA and MP hydrophobic amino acids,covering the hydrophobic groups exposed on the surface of MP,resulting in reduced exposure of hydrophobic groups.With the increase of salt concentration and the addition of polyphenols,MP’s total sulfhydryl group decreased,indicating that the salt promoted the exposure of the reaction groups in MP,and increased the conversion ratio of sulfhydryl group to disulfide bond.The three polyphenols reacted with the mercaptoquinone of cysteine(Cys)in protein to produce mercaptoquinone compounds,and GA tended to covalently react with MP.All three kinds of polyphenols are effective quenching agents for MP’s fluorescence,and can promote the transformation of MP’s fluorescence group microenvironment to hydrophilicity.Modeling analysis of MP structure showed that positive and negative charges of myosin were arranged alternately in the rod-shaped tail,and salt ions combined with myosin through electrostatic action to expand the MP structure,which is conducive to the interaction between polyphenol-MP and MP-MP.(3)The effects of three polyphenols(5mg/g protein)on the quality of MP gel under high and low salt conditions were investigated.It was found that CA,TA and GA had little effect on the strength and water holding capacity of MP gel under low salt conditions,but they could significantly enhance the water holding capacity,gel strength and energy storage modulus of MP gel under high salt conditions.SEM images showed that MP formed rod-shaped stacked and uniform mesh three-dimensional gel structures at low salt concentration and high salt concentration respectively.The addition of polyphenols made the distribution of MP gel network structure more uniform under the condition of high salt,in which the addition of GA(the most likely covalent reaction with MP)could obtain the best gel.