| Frozen storage is an important strategy for storage of meat.Lipid and protein oxidation occurred in meat during frozen storage resulted in deterioration of meat quality.However,there were few studies on the coating protection of frozen meat.This thesis treated frozen cut beef with an antioxidant coating to study the effect of coating on the oxidative stability and the functional properties of beef during frozen storage,aim to provide a new method for the protection of frozen beef quality.There are 3 treatment groups in the experiment: 2% sodium carboxymethyl cellulose coating group(CMCNa group),2% sodium carboxymethyl cellulose + 0.01% tea polyphenol coating group(TP group)and 2 % Sodium carboxymethyl cellulose + 0.01%tea polyphenols + 0.02% vitamin C coating group(VC group),and the uncoated group(PE group)as the control.The storage time of frozen cut beef was 0d,30 d,90d,150 d and 180 d.The results are as follows:1.The degree of fat oxidation and protein oxidation of beef in the four groups increased with extension of frozen storage time.The total mercaptan content of meat in the VC group was 58.05 nmol/mg at 150 d of freezing,which was significantly higher than the other three groups(P<0.05).The carbonyl content of the TP and VC groups was considerably lower than that of the CMC-Na coated group when frozen for 30 d(P<0.05);TBARs values were markedly lower in both TP and VC groups than in the other two groups except for freezing 0d(P<0.05).The above results indicate that the TP and VC groups can dramatically inhibit fat and protein oxidation.2.With the increase of the frozen storage time,the protein structure of beef underwent significant changes,mainly in β-folding,ionic bonding,hydrogen bonding and protein solubility.At the same time,the content of β-turning angle and surface hydrophobicity showed a significant increase(P<0.05).From 30 d to 180 d of storage,ionic and hydrogen bonds’ contents were significantly higher(P<0.05).In comparison,the content of hydrophobic and disulphide bond were lower(P<0.05)in all three coated treatments than in control;At the end of storage,the content of α-helix was significantly higher in the TP and VC groups than in the control group.At the same time,the range of β-rotation was considerably lower(P<0.05).At 180 d of storage,the VC group had the lowest surface hydrophobicity of 62.10 μg among the four groups.The TP and VC groups’ protein solubility was significantly higher than that of the beef in the CMC-Na group(P<0.05),indicating that the anti-oxidant coating treatment with the addition of TP and VC could stabilize the structure of the proteins.3.Compared to 0d,the gel strength and chewiness were significantly lower(P<0.05),and the gel structure was more porous in all four groups at the end of freezing.At 180 d of storage,the gel strength and reversion of the three coated groups were significantly higher than the control group(P<0.05),but there was no difference between the covered groups(P>0.05).The VC group’s hardness value was 6833.39 g,which was significantly higher than the control group(P<0.05).The three coated groups’ gel microstructure was more homogeneous and less porous than the control group throughout the freezing period.The above results indicate that the coating treatment had a beneficial effect on meat’s gel characteristics.4.The sensory characteristics of beef in the four groups deteriorated with the increasing frozen storage time.The VC group’s p H was significantly lower than the other three groups from 30 d to 150 d of storage(P<0.05).At 90 d,the a* values of the four groups decreased significantly;at 150 d of storage,the centrifugal and cooking losses of the VC group were substantially lower than those of the other three groups,and the thawing losses of the CMC-Na group were considerably higher than those of the TP and VC groups(P<0.05),by3.39% and 2.55% respectively.At the end of storage,the corresponding values of volatile aromatic compounds,sulphur-containing compounds,and ammonia were significantly lower in the VC group than in the control group(P<0.05).These results indicate that the addition of TP and VC coating treatments had a significant protective effect on meat quality during storage.In summary,the anti-oxidant coating treatment had a protective effect on beef oxidation stability,protein functional properties,gel properties and meat quality.The VC group had the best protective effect on frozen beef quality in the early storage period.Still,the TP group could achieve similar protective effects as the VC group in the late storage period. |
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