Influences of storage temperature, washing, certification and formation of hairline cracks on quality of Taiwan retail shell egg during storage

• Main Authors: Yu-Chi Liu, 劉瑀琪
• Other Authors: 譚發瑞
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/47435568764114024219

碩士 === 國立中興大學 === 動物科學系所 === 103 === Chicken egg, which contains rich nutrients, is one of the most important sources of animal proteins in the human diet. In addition to the genetic background and feeding management, egg quality is influenced by many factors such as washing, storage temperature and time. Egg shell is mounted with a layer of cuticle which is composed of glycoproteins. Not only performs antimicrobial activity with the aid of some antimicrobial compounds, cuticle but also enhances the mechanical strength of egg shell. Egg washing might diminish cuticle and influence the qualities of eggs during storage. Therefore, the objective of experiment 1 was to investigate the quality of retail eggs collected in various Taiwanese retail markets base on categorization of different storage conditions including stored at chilling shelf temperature (CST), cooling room temperature (CRT), and ambient temperature (AT), washed or not, and CAS certification; the objective of experiment 2 was to investigate the quality of eggs washed or unwashed and stored at 7°C (WC and UC) or 25°C (WR and UR) during 4 weeks of storage. In addition to some conventional egg quality indexes, such as Haugh unit, yolk index, and albumin pH, some indexes including S-ovalbumin content, cuticle coverage, egg shell roughness, quantification of molecular functional groups, and scanning electron microscope (SEM) images were also applied to evaluate the qualities of eggs; the objective of experiment 3 was to investigate the egg quality and microbial characteristics of non-hairline cracked egg (NE), minor hairline cracked egg (MHC), serious hairline cracked egg (SHC) and cracked egg (CE) during 21 days storage at 25°C. In experiment 1, the results showed that the albumin quality and yolk index of CST were significantly superior to AT (P < 0.05). Yolk pH, yolk moisture, yolk chroma, air cell size and eggshell quality were not significantly different (P > 0.05) among CST, CRT and AT. The thick albumin ratio, albumin pH and albumin moisture of unwashed ones were significantly superior to the washed ones (P < 0.05). Haugh unit, albumin pH and yolk index of CAS were significantly superior to non-labeled. In experiment 2, the results showed that the Haugh unit, albumin pH, thick albumin ratio, S-ovalbumin content, yolk index, and air cell size of UC were significantly superior than WR (P < 0.05), indicating the better qualities of UC than WR. For the shell quality, the SEM images showed that cuticle coverage decreased during storage. The pores of UR were exposed when stored for 4 weeks and the amounts of cuticle in unwashed samples were significantly higher than the ones in washed ones (P < 0.05). The shell roughness of unwashed ones increased significantly during storage (P < 0.05). The amounts of OH band and amide I band increased significantly and the amounts of polysaccharide band decreased significantly during storage (P < 0.05). In experiment 3, the results showed that the Haugh unit of NE was significantly superior than others within 18 days (P < 0.05); thick albumin ratio, yolk moisture and whole egg moisture of CE were significantly lower than others (P < 0.05); albumin pH and air cell size were significantly higher than others (P < 0.05); there were no significant differences in yolk index, yolk pH, whole egg pH, egg shell thickness, total plate counts and pathogen in egg contents between 4 treatments (P > 0.05). In conclusion, retail CAS-certified eggs perform better qualities. As considering the quality and safety, it is suggested shell eggs should be washed and stored at refrigerated temperature. Many attempts should be made in order to avoid the happenings of hairline cracks to improve quality of eggs and satisfy the needs of consumers.