Effects of acid-induced aggregation on physico-chemical properties and texture characteristics of hen

• Main Authors: Dong-Sheng Shiau, 蕭東昇
• Other Authors: Jan-Jeng Huang
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/52354850761963729000

碩士 === 國立嘉義大學 === 食品科學系碩士班 === 90 === ABSTRACT Hen eggs, it was separate to egg white and yolk, then the egg white filled into inedible acetate cellulose casing, and soaked in 5% acetic acid, lactic acid or citric acid solution. The pH of egg white from 9.2 decreased to 3.8, acidity from 0% increased to 1% after 0.5 hrs acidic solution soaking, and the pH decreased to 2.5; the acidity increased to 4% after 4 hrs soaking, they were not significantly change after 96 hrs acidic solution soaking. The hen egg white was yellowing transparent, but it changes to turbid after soaked, and it was increased with increased soaking time. The viscosity of hen egg white was increases after 36 hrs acidic solution soaking, and it trend to gelation up to 96 hrs soaking. The soluble protein content of hen egg white from 120 mg/ml decreased to 90 mg/ml after 96 soaking, it decreased about 25%. The surface hydrophobicity intensity and sulfhydryl group of fresh hen egg white was 25.2 So/mg protein and 0.05 mmole/g protein, respectively. Increasing acidic soaking time from 0.5 hr to 6 hrs, the surface hydrophobicity intensity and sulfhydryl group of egg white was 1150 So/mg protein and 3 mmole/g protein, and it was 15000 So/mg protein and 4.5 mmole/g protein until acidic soaking for 96 hrs, respectively. In SDS-PAGE, it was not significantly different of hen egg white after acidic soaking. Denaturation of hen egg white after acidic soaking were studied using a differential scanning calorimeter(DSC) by monitoring the transitions. All the Samples showed the transition temperature was decreased with increase acidic soaking. The hen egg white aggregate after 96 hrs acidic soaking, was dissolved by different protein reagent solvent, and the solubility of aggregate was β-mercaptoethanol > urea > propylene glycol > water > sodium chloride > sodium thiocyanate. Increasing soaking times, the storage modulus was decreased, and the transition temperature was decreased at the same times. After acidic soaking, the hen egg white was heated at 90℃ for 30 minutes, the gel transparency declined dependent on increased acidic soaking time. The gel strength and gel rigidity were broken down with increased acidic soaked time. The microstructure of hen egg white gel was observed by scanning electron microscopy(SEM), it showed the protein molecule aggregated each other and form a large granule of fresh hen egg white gel, but the protein molecule of hen egg white gel was straight and smooth after 3 hrs acidic soaking, and it had not significantly effect on protein molecule arrangement when increased acidic soaking time.