Interfacial Competitive Adsorption And Emulsification Of Sarcoplasmic/Myofibrillar Proteins Under Different Processing Conditions

Meat batters,especially Frankfurter sausages,are popular among consumers due to their rich nutrition,unique taste and fine texture.The flavor of meat batters is mainly derived from the fat particles which evenly dispersed in matrix.Emulsification is an important theory for the production of such products,which depending on the functional properties of the extracted muscle protein during processing.It is generally believed that the salt-soluble myofibrillar protein plays the most important role in emulsification.Therefore,most of the researches focus on the emulsifying properties of the myofibrillar protein.Because it is easily extracted,water-soluble sarcoplasmic protein would play a certain emulsifying effect during prepared meat batters.However,at present,the effect of sarcoplasmic protein on the adsorption of myofibrillar protein at the O/W interface and the emulsifying properties is unknown,especially under the different processing conditions(oxidation or polyphenols from spices).Therefore,the objective of this study was to investigate the interface adsorption behavior of sarcoplasmic protein and myofibril protein and the emulsifying properties,and the influence of common hydroxyl radical oxidation and gallic acid(GA,C₆-C₁ structure)or chlorogenic acid(CA,C₆-C₃ structure).Firstly,the competitive adsorption behavior of pork sarcoplasmic(SP)and myofibrillar(MP)proteins,alone or mixed(ratios 6:4,5:5 and 4:6,w/w)at the oil-water interface was investigated.SP adsorbed more rapidly than MP at the oil surface establishing a?10 m N/m dynamic interfacial pressure(?).However,the dilatational elasticity(E_d)of the SP film was low when compared with MP.For corn oil emulsions prepared with mixed proteins,the poor interfacial adsorption(29%)and low emulsifying activity(3.42 m²/g)of SP were overcome by substitutions with MP that strongly bound to oil.Unabsorbed proteins were mostly SP and secondarily tropomyosin and C-protein from MP.Smaller droplets were observed in MP emulsions than in SP emulsions.Therefore,while both SP and MP contributed to the formation of O/W emulsions,MP played a far more competitive role due to its stronger interfacial adsorption and adhesion properties.Secondly,the effect of the interaction between phenolic acid and meat protein under oxidized(Fenton oxidation system,1 m M H₂O₂)or non-oxidized conditions is studied,which would provide structural information for the subsequent study of protein interface properties.It is found that the phenolic acid had little effect on structure of meat protein.After oxidation,the carbonyl contents in SP and MP were increased and the tertiary structure of protein was unfolded.Besides,the oxidized MP would cross link in result reduced the content of sulfhydryl groups.However,oxidized SP did not cause significant cross-linking due to the lack of active sulfhydryl groups.The addition of CA and GA could inhibit the formation of carbonyl groups.However,oxidation enhanced the protein unfolding and the interaction between protein and phenolic acids.As a result,the interface hydrophobicity of the protein was further decreased and the aggregation increased.CA had a stronger effect on protein than GA,which may be related to its own structure.The oxidizing conditions were selected for follow-up research due to the two phenolic acids caused a higher degree of oxidized protein structure changes than non-oxidized.Finally,the effect of phenolic acid on the interface properties and emulsifying properties of oxidized protein was studied.Under oxidation,the oil affinity of MP and the interaction between interfacial protein were weaken,and the viscoelasticity of the protein film was weaken resulting the lower emulsifying activity.There was not significant change in interfacial and emulsifying properties of oxidized SP.CA and GA could influenced the adsorption behavior of protein through the oxidation which could make protein unfolding then exposed more active group.The phenolic acid enhanced the E_d value of oxidized SP and MP,in other word the oil affinity and the interaction between protein were enhanced then the emulsifying activity was improved.The influenced of interfacial and emulsifying properties of CA was stronger than GA.In addition,mild oxidation did not damage the antioxidant properties of the two phenolic acids.During the storage,the content of TBARS decreased significantly with the increase of polyphenol concentration.In summary,during the emulsification process,MP competitive replaced SP at the O/W interface forming a more stable emulsion.Under different processing conditions,phenolic acid can significantly change the structural properties of oxidized SP and oxidized MP.In turn,it affects the interface adsorption behavior of the protein and changes the emulsifying properties of the protein.The interface properties of muscle protein are closely related to the emulsification properties,which will provide more ideas and guidance for the improvement of meat product emulsification in the future.