Effect Of Tea Polyphenols On The Emulsifying And Gelling Properties Of Mutton Batters After Repeated Freeze-Thaw Cycles

At present,the frozen was still the main storage method of meat batters products.In the process of transportation,storage and consumption,the freeze-thaw was inevitable.The formation of irregular ice crystals during the freeze-thaw lead to the water infiltration and mechanical damage of muscle cells,and induce oxidation of lipid and protein in meat batters products.Adding tea polyphenols(TP)could inhibit the oxidation of meat batters.However,the interaction between tea polyphenols and protein might change the structure of muscle protein,which in turns affect the emulsifying and gelling properties of meat batter products.In this paper,the effects of TP and freeze-thaw on the quality of mutton batter were investigated.The TP were added into the mutton batters with different concentration,named CG,TP1,TP2,and TP3.All samples were treated with 0,1,3,5,7 and 9 freeze-thaw cycles.The surface hydrophobicity,protein solubility,emulsifying stability,fat particle size,water retention,texture characteristics,gel strength and microstructure of mutton batters were measured and the TP content with optimal emulsifying and gelling properties were selected.The mechanism of TP influence the emulsifying and gelling properties of freeze-thawed mutton batters were explored.The detailed contents and results were as follows:1.Repeated freeze-thaw had an adverse effect on the emulsifying properties of mutton batters.After 3 freeze-thaw cycles,the surface hydrophobicity,juice loss rate and fat particle size of mutton batters had the maximum values(P<0.05),while protein solubility and emulsifying stability were the worst.Among them,the protein solubility of CG,TP1,TP2,and TP3 were 2.93 mg/m L,4.40 mg/m L,5.96 mg/m L and 7.08 mg/m L respectively.It indicated that freeze-thaw changed the emulsifying abilities of mutton batters.At the same time,an appropriate amount of TP(0.01%)significantly reduced the surface hydrophobicity and juice loss rate(P < 0.05),increased the protein solubility,and had an improved effects on the emulsifying properties of mutton batters.2.Freeze-thaw had a destructive effect on the gelling properties of mutton batters,especially after third freeze-thaw of mutton batter,the gelling properties of mutton batters became deteriorated,and water holding capacity and hardness were the worst(P < 0.05).The cooking loss of CG,TP1,TP2 and TP3 increased by 7.27%,3.74%,2.95% and 4.08%respectively,which might be caused by the destruction of protein structure in meat batters by irregular ice crystals.Compared with the control group,adding 0.01% TP could improve the water retention,texture characteristics and microstructure of mutton batters.However,excessive addition of TP would destroy the gel of mutton batters.Scanning electron microscopy results showed that the addition of excessive TP made the gel structure rougher and looser in texture,there were more irregular pores with larger sizes in mutton batters.3.Repeated freeze-thaw also affected the protein conformation and water migration in mutton batters.The protein conformation changed with the increase of freeze-thaw cycles.The protein chain unfolded,the a-helix transformed into random coils,the hydrophobic groups were exposed,the hydrogen bond and fluorescence intensity decreased,the thermal denaturation temperature increased,and the tightness of the bond with water molecules decreased.After 3 freeze-thaw cycles,the protein structure changed vastly and the proportion of a-helix in the CG and TP groups were reduced by 7.21% and 4.00%respectively compared with no freeze-thaw samples.Adding TP reduced the ratio of ?-helix,hydrophobic force and thermal denaturation temperature in mutton batters(P<0.05),while hydrogen bonds and the tightness of water molecules illustrated an upward trend,indicated that the addition of TP would influence protein conformation and water migration in mutton batters.