Activity of Various Hydrolytic Enzymes in Chicken Egg-white during Egg Storage
Tamara Tripić, Ivan Škrtić, Ljubinka Vitale
Dept. of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička c. 54, 10001 Zagreb, Croatia
Article history:
Received July 15, 1997
Accepted December 1, 1997
Key words:
chicken egg storage, egg-white, aminopeptidase, cholinesterase, N-acetyl-ii-glucosaminidase
Summary:
In order to obtain an insight into possible changes of proteins in chicken egg-white upon aging, its pH, protein concentration and activities of hydrolytic enzymes were followed during four months of eggs storage. In eggs kept after laying a rise of egg-white pH and a slow decrease of soluble proteins content, were observed. Activity of broad specificity aminopeptidase, glutamyl aminopeptidase and cholinesterase persisted during the whole storage period. A small but significant fall of the broad specificity aminopeptidase activity and a rise of activity of the other two enzymes, were late events of egg's aging. On the contrary, activity of egg-white N-acetyl-β-glucosaminidase had a steep decline and was completely lost after 30 days of storage. Thus, aminopeptidases and cholinesterase by their hydrolytic activity can influence a quality of eggs during their storage, whereas N-acetyl-β-glucosaminidase activity could be used as a marker of their freshness.
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