Characteristics and emulsifying properties of acid and acid-heat induced egg white protein. (March 2016)

• Record Type: Journal Article
• Authors: Chang, Cuihua; Niu, Fuge; Su, Yujie; Qiu, Yan; Gu, Luping; Yang, Yanjun
• Is Part Of: Food hydrocolloids. Volume 54 Part B(2015:Dec.)
• Page Start: 342
• Page End: 350
• Publication Date: 2016-03
• Subjects: Egg white -- Acid-heat induced -- Physicochemical characteristics -- Structure -- Emulsifying properties; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2015.09.026
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: This study investigated the influence of acid (pH 3.0) or moderate heat (60 °C, 15 min, pH 3.0) treatments on physicochemical characteristics (ζ-potential and hydrophobicity), structure (Raman spectra) and emulsifying capacity of EWP after re-adjusted to various pH. Simultaneously, the stability of the emulsions prepared with acid and acid-heat induced EWP (AEP and AHEP) was tested by measuring particle diameter and microstructure of the droplets after salt (0–200 mM NaCl) and heat (90 °C, 30 min) treatments at pH 3.0–4.2. The results revealed that the emulsifying capacity of EWP was enhanced after acid or acid-heat treatment with more hydrophobic amino acids and charged groups exposed on the surface, but little changes in secondary structure. Proteins adsorbed at the oil-water interface were mainly ovotransferrin and ovalbumin. The emulsions made with AEP and AHEP were stable to droplet aggregation with no phase separation during storage for 3 weeks at pH below isoelectric point (pI ≈ 5.0), but exhibited some aggregation at pH near or above pI. The heat stability of emulsions depended on pH and thermal history. The emulsions made with AHEP performed better heat stability than AEP-stabilized emulsions. The salt stability of emulsions depended on the net charge. At pH 3.0, the emulsions were stable in the presence of ≤100 mM NaCl. At other pH, the emulsions showed good tolerance to 50 mM NaCl. These results have important implications for the formulation and production of emulsion based acid products, using egg white protein as emulsifier. Graphical abstract: Heat stability of EWP emulsions depends on pH and thermal history correlated with hydrophobic interaction and electrostatic repulsion. Highlights: Acid or acid-heat treatments induce protein tertiary structure transition. Main components of EWP adsorbed at the interface were ovotransferrin and ovalbumin. Adsorbed proteins may be stripped away from interface induced by repulsion. Heat stability of EWP stabilized emulsions depend on pH and thermal history. EWP-stabilized emulsion can keep stable under 50 mM NaCl during 1 day.