| Summary: | 碩士 === 國立嘉義大學 === 食品科學系碩士班 === 90 === In part I, liquid egg yolk was extracted with 12 fold (W/V) of alcohol and stirred at 30℃ for 30 min, and then filtered. The residues were dried by freeze-drying to remove the solvent to produce the reduced fat and cholesterol egg yolk (RFRC-yolk) powder. The analysis of cholesterol contents and physicochemical characteristics of the RFRC- yolk powder were investigated in this study. Comparison of the functional properties of the RFRC-yolk powder with that of native yolk powder and commercial yolk powder were also investigated. The results showed that the RFRC-yolk powder had the lowest cholesterol content among the three samples. The molecular weight of 43 kDa was reduced on the band of the RFRC-yolk powder as determined by the electrophoresis. In addition, both emulsifying activity (EA) and emulsion stability (ES) of the three samples were increased with increasing protein concentration. After storage at -18℃ for 8 weeks, the emulsifying activity (EA) of the RFRC-yolk powder was the best among the three samples. We also found that the whipping ability and the foaming stability of the RFRC-yolk powder were better than those of the native egg yolk.
In part II, the purpose of this study was to compare the changes chemical components of the reduced cholesterol egg yolk powder with that of the native yolk powder and the commercial yolk powder during storage at room temperature for eight weeks. The results showed that the color difference (ΔE) of native egg yolk powder had the greatest increase among the three samples during storage. As the samples were exposure to fluorescent light or stored at the dark, the changes of peroxide value, carbonyl value and unsaturated fatty acid of the reduced cholesterol egg yolk powder were less than that of the other two samples. The contents of sugars and free amino acids of the reduced cholesterol egg yolk and the native egg yolk powder were decreased with increasing storage time. However, there was no significant changes in sugars and amino acids of the commercial egg yolk powder during storage. When the three egg yolk powders were exposure to fluorescent light or stored at the dark for 8 weeks, the content of total cholesterol oxidation products (TCOP’s) in the three samples was increased due to the oxidation of cholesterol. The content of TCOP’s in the commercial cholesterol egg yolk powder were significantly higher than that in the reduced cholesterol egg yolk powder. Therefore, the reduced cholesterol egg yolk powder had better oxidative stability and lower of TCOP’s content than the other two samples.
In part III, liquid egg yolk was extracted with 12 fold (W/V) of alcohol and stirred at 30℃ for 30 mins, and then filtered. The residues were dried under freeze-drying to remove the solvent to produce the reduced fat and cholesterol egg yolk (RFRC-yolk) powder. Comparing the equality of sponge cakes made from reduced cholesterol with from native yolk powder and commercial yolk powder were also investigated. The results showed that a sponge cake made from the RFRC-yolk powder had a higher swelling volume the other samples and good acceptability in sensory evaluation. In addition, the mayonnaise made from the reduced cholesterol yolk powder had higher viscosity than the other two samples. We also found that the emulsion stability of the mayonnaise made from the three different egg yolk powders was not significantly (p＜0.05) for each other. From the result of sensory evaluation, the mayonnaise made from the reduced cholesterol yolk powder had the highest overall intensity among the three samples. Therefore, the results of this research could be suggested that making reduced cholesterol egg products with reduced cholesterol egg yolk powder was feasible on the standpoint of processing technology.
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