Study On New Process Of Passivating Endogenous Enzymes In Meat Products Based On Ultrasonic Assisted Heating

During storage and processing,cold meat is inevitably affected by endogenous enzymes and microorganisms,triggering a series of biochemical reactions and causing quality deterioration.Excessive lipid oxidation during storage will not only bring unpleasant flavors such as halal and rancidity to meat products,but also cause the content of unsaturated fatty acids to decrease,resulting in loss of nutrients and increased storage difficulties.Among them,lipoxygenase(LOX),as an oxidoreductase,participates in the important lipid oxidation enzymatic reaction.The deterioration of meat texture is related to the degradation of myofibrillar protein.Microorganisms and endogenous proteases can decompose myofibrillar protein in chicken,which is manifested as a decrease in meat hardness and elasticity.Therefore,lipoxygenase and protease are important endogenous enzymes that cause a decline in sensory quality and deterioration in texture,resulting in flavor changes and loss of nutrients.Although refrigerated preservation technology has been widely used in the preservation of cold meat,pre-refrigeration treatment is essential to extend the shelf life of products and reduce quality changes during storage.Ultrasonic waves,due to their unique cavitation effect,can inhibit microorganisms and enzymes in foods.Therefore,ultrasonic-assisted processing technology has attracted much attention in recent years.However,there have been no reports on the use of ultrasound-assisted heat treatment to passivate endogenous enzymes in yellow-feathered chicken,regulate enzymatic lipid oxidation and improve meat quality during storage.In this study,the yellow-feathered chicken was used as the experimental material,and the endogenous enzymes in the chicken were subjected to ultrasound-assisted heat passivation test to determine the best treatment conditions,and the method of combining it with refrigeration was used to analyze the quality changes and the preservation effect,which is expected to provide data support and theoretical reference for the application of ultrasonic technology in the processing and storage of poultry products.First of all,the comparative study of the changes in the enzymatic activity of endogenous proteases and lipoxygenase under the conditions of ultrasound-assisted heat treatment and heat treatment of yellow-feathered chicken.The results showed that ultrasound-assisted heat treatment led to significant inactivation of chicken endogenous enzymes and the inactivation effect increases with the increase of temperature.Within the temperature range set by the experiment,with the extension of the treatment time,the residual rate of enzyme activity is lower and irreversible.Under the two treatment methods based on different temperatures,the inactivation mechanics of chicken endogenous enzymes all follow the first-order reaction kinetics law.The analysis shows that the inactivation rate constant k of the endogenous enzyme of chicken under ultrasound-assisted heating is higher than that of pure heat treatment,especially at 55℃ and 60℃,the ultrasound-assisted heat treatment(0.22 W/cm2)is significantly different from other treatment methods,which indicates that ultrasound-assisted heat treatment can significantly accelerate the inactivation of endogenous enzymes.The study found that compared with heat treatment,ultrasound-assisted heat treatment increases the Ea value of the enzymatic reaction,making the enzymatic reaction more difficult to occur,while significantly reducing the DT value of the passivation time,shortening the treatment time at the same treatment temperature,improve the passivation efficiency of endogenous enzymes.In short,the effect of ultrasound-assisted heat treatment to passivate the enzyme is better than traditional heat treatment methods.Considering that treatment at a lower temperature is beneficial to reduce the effect of treatment on meat quality,55℃ is selected as the optimal passivation temperature for chicken endogenous enzymes.At this temperature,the corresponding DT values of total protease,cathepsin B,calpain and lipoxygenase were:11.77 min,3.44 min,8.95 min and 35.33 min,that is,ultrasonic heating treatment at 55℃for 15 min,the protease was completely inactivated,and the activity of lipoxygenase decreased to 41%.Therefore,under this test condition,we explored the effect of ultrasound-assisted heat treatment on the quality changes of yellow-feathered chicken during refrigeration.Based on the high efficiency of ultrasonic-assisted heat inactivating enzymes,the treatment under vacuum packaging combined with 4℃ refrigeration was used to study the effect of this treatment on the quality changes of yellow-feathered chicken during storage.By measuring total viable counts,endogenous enzyme activity,protein degradation,microstructure,texture,and other indicators,it was found that ultrasonic-assisted heat treatment had good effects on the sterilization and inactivation of enzymes in chicken.No microorganisms were detected during the entire storage process,and the number of colonies in the control group exceeded the upper limit on the 9th day of refrigeration,and the shelf life of samples with ultrasound-assisted heat treatment was extended by at least 2 days.Secondly,the protease activity of chicken was completely lost and irreversible after ultrasound-assisted heat treatment,and the lipoxygenase activity was reduced by 80%.The enzyme activity was kept at a low level during storage,indicating that this treatment can effectively inactivate protease and significantly inhibit lipoxygenase activity.Meanwhile,the content of malondialdehyde,carbonyl and other indicators was used to monitor the lipid oxidation,protein degradation and texture changes of chicken during storage.It was found that ultrasound-assisted heat treatment will cause a certain degree of oxidation and degradation of chicken lipids and proteins.The TBARS value and carbonyl content of the treatment group in the early stage(day 0)were slightly higher than those in the direct refrigerated group,but no significant changes occurred during storage.However,the control group exceeded treatment group in lipid oxidation and protein degradation on the third day,and TCA-soluble peptide and MFI increased significantly with storage time.In the later period of storage,protein in the control group was severely degraded,showing that the texture deteriorated and the hardness value was significantly reduced.The observation of the microstructure showed that the myofibrils were broken and the gap was continuously expanded.SDS-PAGE analysis showed that the actin and myoglobulin of control group degraded during storage,new electrophoretic bands appears.In short,ultrasonic-assisted heat treatment effectively slowed the degradation of chicken protein,controlled the oxidation of lipids and protein degradation,and maintained good texture characteristics,thereby playing an important role in improving the quality of chicken during storage.