| Prepared meat products are favored by consumers because of their convenience,quickness,rich nutrition,and high added value.Their production and consumption are increasing day by day.However,the conditioning meat products are susceptible to fat and protein oxidation during the frozen storage process,and the juice loss is serious during the thawing process.How to maintain the frozen storage quality of prepared meat products has become an urgent problem.In this study,the conditioning pork patties were used as the research object.First,the effect of freezing method on the quality of conditioning pork patties was investigated.After that,the formulations of water and oil retention agents and antioxidants were optimized,and their application effects were analyzed.Finally,repeated freezing was examined.Effect of melting on water and oil retention and oxidation resistance of conditioning meatloaf.The main research contents and results are as follows:1.Effect of thawing methods on quality of prepared pork patties.In order to explore the effects of different thawing methods on the quality of pork patties and the degree of protein oxidation,The prepared pork patties frozen at-18 ?,then the frozen meat patties were frozen by four different thawing methods namely air thawing,refrigeration thawing,running water soaking and salt water soaking,respectively.The effects of different thawing methods on meat patties quality and myofibrillar protein oxidation were analyzed by determine the water retention properties(thawing loss rate,centrifugal loss rate),p H,TBARS value,TVB-N value,carbonyl content,sulfhydryl content,protein solubility,and SDS-PAGE gel electrophoresis.The results showed that thawing methods had a great effect on the water retention of the prepared pork patties.Air thawing and refrigeration thawing had the best water retention.At the same time,thawing caused significant increase of the value of TVB-N(P<0.05),especially the value of TVB-N by salt water thawing,but the effect of thawing on p H value,TBARS value and color difference of the prepared meat patties were not significant(P > 0.05).Through the determination of the oxidation degree of myofibrillar protein,it was found that thawing methods could increase the carbonyl content of myofibrillar protein,decrease the sulfhydryl content and solubility,which was confirmed by SDS-PAGE electrophoresis.Comparing several thawing methods,it was found that the oxidized degree of myofibrillar protein in refrigeration thawing was the lowest,so the quality of prepared pork patties could be well maintained.2.Optimization of formula to improve water and oil retention of prepared meatloaf.In order to improve the water retention and oil retention of the prepared meat patties,and to reduce the moisture and oil loss of the meat patties during thawing,experiments were carried out to add flaxseed gum,sodium caseinate,purslan powder,and corn modified starch to the modified pork patties.The effects of additives on the water and oil retention of the prepared pork patties were optimized on the basis of L9(34)orthogonal test.The results showed that with the increase of the concentration of the four preservatives,the water and oil loss rate of the prepared meat patties decreased significantly(P <0.05),indicating that the natural extract can effectively improve the water and oil retention of pork patties during freezing storage.The orthogonal test showed that the optimal fit ratios of the four natural extracts were: linseed gum 0.25%,sodium caseinate 5%,purslan powder 3.5%,and corn modified starch2.7%.Under this formula,the water loss rate of pork patties is 15.73%,which is 42.65% higher than that of the original recipe group,and the oil loss rate is 11.97%,which is 42.48% higher than the original recipe.3.Optimized formulations to improve the oxidation resistance of prepared meatloaf.In order to improve the oxidation resistance of the prepared meat patties,resveratrol,proanthocyanidins and tea polyphenols were added to the prepared pork patties respectively,and the TBARS value,TVB-N value,color difference,carbonyl content,thiol content and protein of frozen pork patties were measured Solubility and other indicators were selected through the single factor test for the appropriate addition of the four antioxidants,and based on this,L9(34)orthogonal test was used for compound optimization.The results show that all three natural antioxidants can significantly inhibit the increase of TBARS value,carbonyl group and TVB-N value(P <0.05),reduce the loss of thiol group and decrease of protein solubility(P <0.05).The most suitable ratio of compound antioxidants is: 1 g·kg-1 of resveratrol,1.5 g·kg-1 of proanthocyanidins,and 0.4 g·kg-1 of tea polyphenols.Compared with the blank control,the pork patties TBA treated with this formula Value,TVB-N value and carbonyl content decreased by 62.95%,78.52% and69.35%,respectively,and the thiol content and protein solubility increased by 38.24% and 74.32%,respectively,which increased the antioxidant capacity of pork patties.4.Effect of repeated freeze-thaw cycles on quality characteristics of prepared meatloaf.Take the patties with water and oil retaining agents and antioxidants as the experimental group,and set up a positive control group(with0.2 g·kg-1 Butyl hydroxyanisole Butyl hydroxyanisole,BHA)and a blank control group to study the different freeze-thaw cycles.(0,1,3,5,7 times)Down-regulated pork patties water retention(defrosting loss,centrifugation loss,cooking loss,p H value),degree of fat oxidation(TBARS value,peroxide value POV))and protein oxidation degree(Carbonyl group,thiol group,protein solubility),and the correlation between the three was analyzed.The results showed that as the number of repeated freeze-thaw cycles increased,the p H value increased first and then decreased significantly(P <0.05);the water retention decreased significantly(P <0.05);the degree of oxidation of fat and protein increased significantly(P <0.05).Comparing the three groups,the water retention capacity of the experimental group was significantly higher than that of the BHA group and the blank control group,and the degree of fat and protein oxidation in the experimental group was significantly lower than that of the blank control group.Correlation analysis showed that protein oxidation indexes such as carbonyl,thiol,and protein solubility were significantly correlated with water retention indexes such as p H,thawing loss rate,and cooking loss rate(P<0.01),and TBARS and POV,which represent the degree of lipid oxidation.The values were also significantly correlated with carbonyl,thiol,and protein solubility(P <0.01),indicating that the correlations between water retention,lipid oxidation,and protein oxidation were extremely significant(P <0.01).The test results proved that freeze-thaw cycles severely degraded the quality of prepared pork patties,resulting in reduced water retention and oxidation of fats and proteins.However,the addition of water-and oil-retaining agents and antioxidants can suppress the deterioration of the quality of prepared meatloaf during repeated freeze-thaw cycles. |
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