Structural changes and emulsion properties of goose liver proteins obtained by isoelectric solubilisation/precipitation processes. (March 2019)

• Record Type: Journal Article
• Authors: Xue, Siwen; Yu, Xiaobo; Li, Xin; Zhao, Xue; Han, Minyi; Xu, Xinglian; Zhou, Guanghong
• Is Part Of: Lebensmittel-Wissenschaft + Technologie =. Volume 102(2019)
• Page Start: 190
• Page End: 196
• Publication Date: 2019-03
• Subjects: Devalued animal by-product -- Protein recovery -- Raman spectral analysis -- Protein secondary structures -- Emulsifier; Food industry and trade -- Periodicals; Food -- Composition -- Periodicals; Microbiology -- Periodicals; Nutrition -- Periodicals; 664.005
• DOI: 10.1016/j.lwt.2018.12.019
• Languages: English
• ISSNs: 0023-6438

Abstract

Abstract: Structural changes and emulsion properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were evaluated, with non-treated goose-liver (GL) paste set as the control. Increasing contents of either reactive-sulfhydryl or surface hydrophobic groups were observed in isoelectric solubilisation/precipitation-recovered proteins ( P < 0.05). The ACP-proteins showed higher surface hydrophobicity but lower reactive-sulfhydryl content than that of ALP-proteins ( P < 0.05). Compared to the control, ACP-proteins had lower α-helix and β-sheet contents ( P < 0.05); meanwhile, ALP-proteins exhibited a lower α-helix content but higher β-sheet content ( P < 0.05). Tentative application of these recovered proteins as emulsifiers exhibited that proteins underwent treatment at pH 11.0 had a higher emulsifying activity index (3.2 mg/m 2 ), emulsifying stability index (17.2%) and emulsifying viscosity (62 Pa s) than that of the control ( P < 0.05), along with smaller and spherical droplets uniformly distributed in the emulsion. However, ACP-protein emulsions exhibited adverse trends. Different secondary structures of the proteins in ACP-/ALP-cream layers explained these divergences in part, where the lower β-sheet content of ACP-samples could impair protein interactions, leading to inferior emulsion properties. In contrast, the increased β-sheet fraction of alkali treatment favoured a more stable emulsion. Potential of ALP-proteins as an emulsifier was verified. Highlights: Isoelectric solubilisation/precipitation (ISP)was used to obtain goose liver protein. Acidic or alkali ISP-extracted proteins were found differ in physicochemical traits. Alkali-ISP obtained proteins showed better emulsion traits than acidic counterparts. Higher α-helix in alkali-samples partly explained better emulsion ability & property. Proteins recovered at pH 11.0 ISP-process was the most potential sample as emulsifier.