| Summary: | 碩士 === 台南科技大學 === 生活應用科學研究所 === 98 === In order to develop the multiple products of duck eggs and to further advance the processing utility of duck eggs and expand the consumption market, duck eggs were utilized in this study to investigate the production of the marinated duck eggs with half-coagulated yolk, the quality, and the characteristics for the reference and application of the manufacturers. In the test, the influence of respectively difference heating time, marinating time, and the time for the second sterilization on the quality and characteristics of the marinated duck eggs with half-coagulated yolk, and, later, these eggs were preserved in 4±1℃ for eight weeks to investigate the changes of the quality during the preservation period. The result was summarized as follows:
1.When fresh duck eggs were heated in 90℃, the coagulation of egg white and yolk became harder as the heating time increased. During the heating time between the fifth and thirteenth minute, the water content in the egg white and yolk did not change significantly, but the pH value of the egg white increased due to heating. After being heated in 90℃ for seven minutes, the egg white completely coagulated, and the yolk became golden, sticky, and colloidal, which was employed as the heating condition in this study.
2.The duck eggs with half-coagulated yolk, which were heated in 90℃ for 7 minutes, were marinated in the marinade in 5℃ for respectively 0, 1, 2, and 3 days. The total bacterial counts were approximately 3.07~3.85 log CFU/g, and as the time of being marinated increased, the total bacterial counts increased (p<0.05). After being marinated for two days, the appearance and flavor of the eggs were both fair, and the bacterial counts were less than those being marinated for three days. Therefore, being marinated for two days was applied as the condition for immersion.
3.When the products after being marinated for two days were packed in vacuum packages and heated at 85 ℃ for 0, 6, 8, and 10 minutes for second sterilization, the water content in the eggs was between 61.62% and 64.11%, and the pH value was between 6.96 and 7.17, which became higher as the heating time increased. However, the total bacterial counts reduced as the heating time increased, but the yolk became solidified when they were heated for the ten minutes whereas the yolk was still golden, sticky, and colloidal when they were heated for the eight minutes, which was taken as the condition for second sterilization.
4.The products which were heated in 90℃ for seven minutes, marinated for two days, packed in vacuum packages, and finally heated 85 ℃ water for eight minutes and the products which did not have second sterilization were respectively placed at 4±1℃ for the eight-week preservation test. The result indicated that during the preservation period, the water content of the two groups was stable and did not have significant changes. In the beginning of the preservation period, the pH values of the two groups both decreased slightly. In addition, the values became stable since the second week, and they increased slightly since the fifth week. In the entire preservation period, the pH value of the products with second sterilization was slightly higher than that of the products without second sterilization. As the preservation time passed, the VBN values tended to be stable and increase slowly and slightly, and the values increased more significantly since the seventh week. During the eight-week preservation period, the total bacterial counts of the unsterilized group were higher than those of the sterilized group (p<0.05). After the seventh week, the total bacterial counts of the unsterilized group increased from 103 CFU/g to 104 CFU/g, but those of the group with second sterilization maintained at approximately 103 CFU/g. The products were evaluated after respectively 0, 4, and 8 weeks. The appearance, quality, flavor, and overall acceptance of the products did not change significantly, the evaluation grades were all good, the flavor was fine, and there was not any decay.
In summary, the products which were heated in 90℃ for seven minutes, marinated in the marinade in the freezer (5±1℃) for two days, packed in the vacuum packages, heated in the 85℃ hot water for eight minutes for second sterilization, and preserved in 4±1℃ for weeks still had good quality, flavor, and overall acceptance. This can be employed as the reference for the processing and production of the marinated duck eggs with half-coagulated yolks.
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