| At present, In Chinese sales market of fresh eggs, dark spots egg has become a serious problem, the formation of dark spots eggshell not only causes serious damages to the appearance and the quality of eggs, it aslo inflicts huge economic losses for producers and sales. In this paper, dark spots eggs was used to be experimental subjects, dark spots part and no spots part were peeled from dark spots eggs, in order to study the dark spots part, the no spots part and normal eggshell on the physical and chemical indicators and structure differences, and the impact of the growth of the eggshell of dark spots and different coverage on egg freshness and microbial indicators, aiming at exploring the reasons for the formation of the eggshell and dark spots on the storage performance of eggs. The main results are as follows:1. Preliminary exploration on the reasons for the formation of dark spots in eggshellIn this paper, some physical and chemical indicators of normal eggshell and dark spots eggshell calcareous hard shell were tested, such as thickness, hardness, moisture, crude ash, mineral elements(Ca, Mg), protein content, crystal structure and ultrastructure, as well as the thickness and protein content of shell membrane, the results showed that: the dark spots part was compared to the no spots part and the normal group, the hardness of dark spots part calcareous hard eggshell was minimum and the water content of dark spots part calcareous hard eggshell was maximum, the difference was significant(P<0.01), no spots part and normal group had no difference; the calcareous hard shell thickness was no difference among the three groups, but the thickness of dark spots part shell membrane was significantly lower than no spots part and normal group(P<0.01), the thickness of no spots part was significant lower than normal egg shell membrane(P<0.05); calcareous hard eggshell protein content of three groups was no significant difference(P>0.05), while the protein content of dark spots eggshell membrane was significantly lower than normal eggshell membrane protein content(P<0.01), calcareous hard eggshell crude ash, Ca, Mg elements content and crystal structure of three groups were not significantly different (P> 0.05). Electron microscopy was used to observe the cross-section, the inner and outer surfaces of calcareous hard shell, the inner and outer surfaces of the shell membrane, compared to no spots part and normal group, the calcareous hard shell section of dark spots part showed significant loose texture, the inner and outer surface chapped severely, inside and outside surface of dark spots part shell membrane also showed more cracks, large voids, loose structure and other characteristics, the structure of normal eggshell was smooth, solid and compact.According to comprehensive analysis of detection index and the images, It was preliminarily concluded that the formation of dark spots eggshell was due to that the shell membrane under the dark spot position was thinner and larger mesh, as a result of this, water was more easily through the shell membrane penetrate into the calcareous hard eggshell, and then, the water was more accommodated by calcareous hard shell in the portion of the gap. Thereby dark spot was formed on a macroscopic.2. Impact of different dark spots coverage on the quality of eggThis paper discussesed the influence of the egg shells of different dark spots coverage,such as 0%±、10%±、30%±、60%±, for storing fresh eggs on the weight loss, relative density, yolk index, egg white pH value, Haugh unit and other indicators and total bacterial count, colibacillus, mold, salmonella and other microorganisms. During the storage, colibacillus and salmonella among different dark spot coverage eggs were not detected, but the rate of freshness declined and microbial growth of dark spots eggs were faster than those normal eggs, and with the increase of egg shell dark spots coverage, the decline in egg freshness and microbial growth became faster. Egg shell with dark spots has a bad influence on the quality of eggs, greatly accelerated the decline in the quality of eggs and increased the rate of corruption and shorten the storage period. |
