Study On Processing Optimization And Color And Flavor Quality Of Preserved Eggs

Preserved eggs are traditional Chinese egg products,loved by consumers with a long time.For a long time,duck eggs have been always as the raw eggs for preserved eggs processing instead of chicken eggs,which is inconsistent with the development of Chinese largest egg production industry chain and also affects the development of the egg processing industry seriously.In addition,with attentions of consumers increasing on food safety and green consumption,it needs to improve on high alkalinity and low acceptant color as soon as possible,which has become a key technical innovation content of traditional egg industry.Therefore,in order to meet the requirements of mainstream consumer groups full of healthy consumption ideas on color,flavor and sensory qualities of preserved eggs,it requires further study on the formation mechanism of color and flavor quality in preserved eggs,improving new technology and developing new products,which also will be the development direction of Chinese traditional egg products industry.This paper aims at studying the related basic issues about textural properties of albumen gelatinization,emphases on the color change of the gel and protein structure during chicken preserved eggs processing.On the basis of these studies,we got the final preserved egg processing technic by Response Surface Methodology.Finally,the volatile flavor compounds in the optimized group of preserved egg during processing were analyzed.The main contents,results and conclusions in this dissertation are summarized as follows:1.Study on gel properties and color changes of preserved eggs during processingIn this study,changes in chemical composition,gel characteristics and colors of chicken preserved eggs albumen and yolk were monitored during pickling in the presence of divalent cations(ZnSO4)at level of 0.3%up to several weeks.The result showed that free alkalinity contents,hardness,elasticity,cohesiveness and chewiness increased significantly(P<0.05),and the capacity to gel for egg albumen became lower(P<0.05).Variation tendency of chemical composition,and gel characteristics of preserved eggs albumen tended to become stable as pickling for 28 days.The most of protein degraded in first 14 days during pickling,and protein whose molar weight was greater than 86.6kDa degraded firstly.As the alkalinity of preserved eggs albumen increased,micro molecule peptides accumulated continuously(14.3KDa and 10kDa),and the total free amino acid content of preserved eggs albumen significantly decreased(P<0.05),and the degradation of protein no longer continued as pickling for 21 to 28 days.The variation trend of L*value and b*value of albumen and yolk was different from a*value of albumen and yolk.The variation trend of white value of albumen was correlated negatively with yolk.2.Optimization of golden preserved eggs processingPreserved eggs were soused by immersing fresh eggs as raw materials.The effects of concentration of NaOH and pickling temperature and pickling time on golden preserved eggs qualities were studied by response surface methodology based on single factor experiment,which applied sensory evaluation score and whiteness of final products as the indicators,then optimization of golden preserved eggs processing was solved.Based on the results,effects of different factors on preserved eggs sensory qualities and color change were significant(P<0.05),and the result of which was nonlinear.Based on the results of response surface methodology,there was a significant interaction among NaOH concentration,pickling temperature and pickling time for sensory quality of preserved eggs(P<0.05),and a linearly decreasing trend of NaOH dosage critical values appeared with pickling temperature increasing,a linearly increasing trend of NaOH dosage critical values appeared with pickling time Increasing.Finally,the processing was optimized as:NaOH dosage is 4.06%,pickling temperature is 19?,pickling time is 22.5d,which can be used to process preserved eggs.3.Analysis of volatile flavor compounds in preserved eggs during processingThe volatile components in preserved egg during processing were analyzed by headspace-solid phase microextraction combined with gas chromatography-mass spectrometry(HS-SPME-GC-MS),the extraction of volatile flavor compounds were identified and change of relative content of volatile compound in albumen and yolk of preserved egg during processing have been compared.The results show:In albumen,58 volatile compounds were isolated and identified and in yolk,62 volatile compounds were isolated and identified.In a short,the flavor compounds of preserved eggs formed in the pickled 7-21d mainly and stabilized in the late processing,there is no significant difference compared with flavor compounds of traditional preserved egg.Esters,aldehydes,alcohols are the characteristic flavors of albumen and Esters,alcohols and acids are the main flavor ingredients of yolk in preserved eggs.During processing,the main characteristic flavors of albumen are 2,6,10,15,19,23-hexamethyl-2,6,14,18,22-pentaene group-twenty-four 10,11-diol,decanal,nonanal,geranyl isovalerate,L-ascorbic acid 2,6-palmitate,2,3-dihydro-1,1,3-trimethyl-1H-indene.the main characteristic flavors of yolk are 18-nonadecenoic acid,6-oleic acid,2-octyl-cyproterone Kissin aldehyde,pentadecanoate 14-methyl-methyl butyl phthalate collar myristyl,(E)-10-heptadecenyl-8-hexyne-methyl.Stabilized during processing 21?28d,no significant difference compared with traditional preserved egg.