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KMID : 1025520090510060521
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Journal of Animal Science and Technology
2009 Volume.51 No. 6 p.521 ~ p.526
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Effect of Irradiation on the Mixture of Egg White Proteins Responsible for Foaming Property.
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Liu Xian-De
Jo Cheo-Run
Jin Dong-Il
Lee Soo-Kee
Han Rong-Xiu
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Abstract
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Irradiation of egg white increased foaming ability significantly. To investigate the protein modification by irradiation responsible for the increase of foaming ability, 3 major egg white proteins were purchased and mixed(7.7g/L ovalbumin, 1.8g/L ovotransferrin, 0.5g/L lysozyme) as a model system and irradiated at 0, 2.5, and 5kGy. The different protein expressions were evaluated using 2-D electrophoresis and it was found that ovotransferrin was cleaved by irradiation and molecular weight and isoelectric point were changed. In addition, many uncharacterized proteins were found and it indicated that irradiation modified proteins randomly but mainly fragmentation was observed. Therefore, it can be concluded that protein fragmentation of 3 major egg white proteins responsible for foaming ability may be the main reason for the improvement of foaming ability.
Egg white is traditionally used as an ingredient by food industry because of its exceptional functional properties: foaming, emulsifying, and gelling properties(Lechevalier et al, 2003). Among them, the foaming ability is one of the most important functions of egg white protein in the manufacturing of bakery and confectionary products. Several studies have been reported that heating and high pressure treatment may improve foaming ability of egg white. Because moderate heat or higher than 450 MPa of high pressure treatment induce denaturation of egg white protein and results a loss of secondary structure, and this change can improve foaming ability of egg white(Donovan et al, 1975; Van der Planken et al., 2005). However, egg white proteins are quite
Correspondingauthor:Dr. Cheorun Jo, Department of Animal Science and Biotechnology, Chungnam National University, Daejeon, 305- 764, Republic of Korea. Tel: +82-42-821-5774, Fax: +82-42-825-9754, E-mail: cheorun@cnu.ac.kr
sensitive to heat treatment inducing insolubility, especially for ovotransferrin. High pressure treatment also has several limitations in a mass production and an increased cost (Song et al., 2009).
Several studies indicated that irradiation improved the foaming ability and foam stability of egg white and more stable viscosity than heated egg white(Ball and Gardner, 1968; Ma et al., 1990; Wong et al., 1996 Song et al., 2009). Irradiation generates hydroxyl radical and superoxide anion radical and these radicals induce chemical changes such as fragmentation, aggregation, and cross-linking between peptides and proteins. This change may improve functional properties of egg white(Moon and Song, 2001). Recently, Song et al.(2009) reported that irradiation improved foaming ability and this improved ability maintained after processing of an angel cake. However, the mechanism of this phenomenon is unclear so far.
Three major egg white proteins known to be responsible for foaming property are ovalbumin, ovotransferrin, and lysozyme and they account for 54, 13, and 3.5% of the egg white proteins, respectively(Stadelman and Cotterill, 1977). Therefore, the objective of this study was to investigate the irradiation effect on foaming ability of egg white and the protein modification of 3 major egg white proteins including ovalbumin, ovotransferrin, and lysozyme, which are known to be responsible for foaming property of egg white.
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KEYWORD
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Irradiation, Egg white protein mixture, Foaming ability, 2-D electrophoresis
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