关键词: 全蛋液；菌落总数；分离鉴定；典型菌株

Abstract: In order to establish the correlation between aerobic plate count on the eggshell surface and liquid whole egg’s shelf life, the typical bacterial strains on the eggshell surface were isolated and purified by the gradient dilution and streak plate methods and were identified by morphological observation, physiological and biochemical tests and 16S rRNA gene sequencing. Then the isolated strains were separately inoculated into liquid whole egg, which was subsequently stored at 4 ℃, and their spoilage potential was comparatively evaluated by measuring growth kinetics curves as well as the total volatile basic nitrogen (TVB-N) content, pH, textural properties and sensory evaluation of liquid whole egg. The results showed that microbial contamination on the surface of eggs was an important factor affecting the shelf-life of liquid whole egg (P < 0.05), and the typical strains we obtained included Escherichia coli (E), Bacillus subtilis (B), Kocuria marina (D) and two strains of B. cereus (A and C). All inoculated samples became spoiled after storage at 4 ℃ for 30 h, showing significantly higher TVB-N value than the non-inoculated control. In addition, the pH value, gel hardness and water-holding capacity of the samples were decreased significantly as compared with those of the control samples. By comparing changes in the storage quality of the samples, the spoilage potential of B. cereus was the strongest among the spoilage bacteria, followed sequentially by E. coli, B. subtilis and K. marina.

Key words: liquid whole egg; total number of bacterial colonies; isolation and identification; typical strains