Study On The Key Technology Of Quick Curing Of Low Salt Salted Duck Eggs

Salted duck egg is one of our traditional egg products,and due to its unique flavor,rich nutrition and"fresh,fine,tender"protein,as well as"loose,sand,oil"yolk,it is deeply loved by people.However,the development of the processing industry of the salted duck egg has been severely restricted due to the long curing cycle,high salt content of egg white,and the potential safety hazards of directly curing salted duck egg without cleaning.Therefore,this paper studied the effects of several chlorine-containing cleaning reagents on the cleaning effects of raw eggs and the color and flavor of the salted duck egg white,thus provides the basis for the selection of cleaning reagents and cleaning methods of raw eggs for salted duck eggs curing.On this basis,the effects of ultrasonic modes on the eggshell（ES）and eggshell membrane（ESM）permeability and the quality of egg contents were studied,based on the prominent cavitation effects of ultrasound,then the optimum ultrasonic parameters were established based on“pore expansion and viscosity reduction”.Finally,a new method for the preparation of low-salt salted duck eggs by ultrasonic assisted vacuum curing technology was established.The main research contents and conclusions are as follows:（1）To study the effects of chlorine-containing cleaning reagent,cleaning temperature and cleaning time on the cleaning effects of raw egg and the color and flavor of salted duck egg white,on this basis,the optimal cleaning method of raw eggs for salted duck egg curing was established.The results showed that compared with pure water cleaning,Na Cl O,HCl O and HCl O+UV washing at 25℃and 40℃could significantly reduce the number of E-coli on the ES surface,and among them HCl O+UV group has the most significant bactericidal effects（P<0.05）;Moreover,HCl O+UV washing can significantly remain the haugh unit,yolk index,and the p H of egg white and yolk of raw eggs while ensuring ES strength and thickness（P<0.05）.In addition,HCl O and HCl O+UV washing at 25℃can retain the alcohols,aldehydes,ketones and some aromatic compounds,while significantly reducing the contents of inorganic sulfide compounds and increasing the whiteness value of salted duck egg protein（P<0.05）.The results of free amino acid（FAA）analysis showed that HCl O and HCl O+UV washing at 25℃could significantly increase the contents of umami FAA and enhance the Taste intensity value（TAV）of salted duck eggs.In summary,HCl O and HCl O+UV cleaning at 25℃can ensure the color and flavor quality of salted duck egg on the premise of ensuring the cleaning effects of raw eggs.（2）To study the effects of ultrasonic modes on the permeability of ES and ESM and the quality changes of egg contents in aqueous and salt systems,and to reveal the"viscosity reducing"mechanism of ultrasound on egg white protein at the molecular level.The results showed that compared with aqueous system,ultrasonic treatments,especially at 40 k Hz and 20/40/60 k Hz,could significantly reduce the viscosity of and Haugh unit of duck egg white,and increase the porosity of ES and ESM,while maintaining the ES strength,ES thickness and yolk index of duck eggs in salt system（P<0.05）.In addition,the results of molecular structure study showed that ultrasonic pretreatment could cause the unfolding of the globular egg white protein,and thus significantly enhance the surface hydrophobicity（H₀）of egg white protein（P<0.05）,but the molecular weight of egg white protein did not change significantly,indicating that ultrasonic treatment just changed the aggregation state of protein but did not change the size of molecular weight of protein.In conclusion,ultrasound at 40 k Hz and 20/40/60 k Hz can play a role of"pore expansion and viscosity reduction"by reducing the aggregation state of egg white protein and increasing the porosity of ES and ESM,while ensuring the quality of ES and integrity of egg yolk in the salt system.（3）To study the effects of ultrasonic assisted vacuum curing technology on physicochemical properties,edible quality and characteristic flavor of salted duck eggs white,and to reveal the molecular mechanism of ultrasonic enhanced vacuum curing technology to improve the oil yield of salted egg yolk.The results showed that ultrasonic pretreatment can significantly accelerate the solidification,dehydration and hardening of salted egg yolk,increase the salt contents and oil yields of salted egg yolk,especially,the ultrasound at 20/40/60 k Hz has the significant strengthening effects on"dehydration and oil production"of egg yolk（P<0.05）.At the same time,ultrasonic pretreatment could also significantly increase the hardness of salted egg yolk,the brightness and whiteness of protein（P<0.05）,and inhibit the migration of water or free lipid in salted egg yolk,and thus improving the water/oil holding performance of salted egg yolk.This conclusion was also demonstrated by the results of the molecular interactions of egg yolk protein.In addition,the results of egg yolk microstructure analysis also showed that ultrasonic pretreatment could induce egg yolk particles to form smaller and more egg yolk particles,thus increasing the sandy tasty of egg yolk,which was consistent with the results of sensory evaluation.The results of flavor analysis showed that ultrasonic pretreatment could significantly increase the contents of aromatic compounds,alcohols,aldehydes,aromatic compounds and other volatile substances in salted egg yolk,especially the contents of hexaldehyde which contributed to the flavor of salted egg yolk.In conclusion,compared with traditional vacuum curing technology,ultrasonic assisted vacuum curing technology can further improve the salt content and oil yield of egg yolk,and to improve the sandy taste and volatile flavor of egg yolk.