A Preliminary Study On The Formation Of Black Circles In Cooked Salted Egg Yolk

The production of salted duck eggs in China has a long history,but black circles are common in its production and processing,which not only affects the appearance of salted egg yolks,but also is not conducive to its sales and development.In order to explore the reasons for the formation of the black circle phenomenon of salted egg yolk,the basic composition of the salted egg yolk and the material composition of the black circle were analyzed and identified,and some ideas for improvement were provided on this basis.The research mainly includes the following contents:(1)The effects of different conditions on salted duck eggs are studied from the aspects of raw duck feeding methods,duck egg shell color,duck egg freshness,salt content of different pickling liquids,pickling time,high pressure sterilization temperature and high pressure sterilization time.The effect of the circle phenomenon,the result is a black circle phenomenon,and there is no obvious difference.(2)The composition of the black circle of the salted egg yolk was analyzed and identified.The main conclusions were: the protein content and p H value of the black circle and the non-discolored part were significantly different;the iron ion content of the black circle(118.623 ?g/g))Is higher than the uncolored egg yolk(91.432 ?g/g);the pigment in the salted egg yolk is mostly carotenoids,and the content of the black circle part(0.11 mg/g)is higher than that of the uncolored part(0.080 mg/g);the black circle part The protein microstructure was irregularly dispersed,and the black circle of the salted egg yolk was lighter than the non-discolored part at the 36 KDa band;the test found that the black circle disappeared completely after 24 hours of exposure to an aerobic environment.(3)The basic components(fat content,moisture content,protein content,salt content)and p H changes of each part during the curing process were studied.The results showed that the salted egg yolk black circled parts were In the discolored parts,the p H value gradually rises to alkaline,the water content is seriously lost,and the protein content is significantly reduced.Combined with the identification results of the black circles,the protein hydrolysis during the pickling process reduces the protein content,which reduces the water retention capacity of the salted egg yolk,reduces the water content,and concentrates the pigment,thereby darkening the black circle of the salted egg yolk.At the same time,the potential difference caused by the increase in p H makes the metal ions in the salted egg migrate,and the combination of metal ions,pigments,etc.with the active groups provided by some sulfur-containing amino acids in the salted egg will produce a blue-black substance,that is,a black circle phenomenon..(4)Based on the analysis of the above test results,modified atmosphere packaging and metal ion chelating agent immersion tests were performed on salted eggs,and the results did not produce black circles.Among them,the distribution of iron in modified atmosphere packaged salted egg yolk is consistent with that of non-black circled salted egg yolk in vacuum packaging.The best soaking condition of metal ion chelating agent is:ethylenediamine tetraacetic acid(EDTA-2Na)with a dosage of 3.2 %,soak for 6 h at 10?.