Changes in Salt Solubility and Microstructure of Proteins from Herring (Clupea harengus) after pH-Shift Processing
Journal article, 2012
Salt solubility of pH-shift isolated herring (Clupea harengus) muscle proteins was studied in relation to pH exposure and microstructure using transmission electron microscopy (TEM). Using protein solubilization at pH 11.2 with subsequent precipitation at pH 5.5, salt solubility of the proteins decreased from 78 to 17%. By precipitating the alkali-solubilized proteins at the pH of native herring muscle, 6.5, salt solubility only decreased to 59%, proving that pH values between 6.5 and 5.5 affected protein salt solubility more than the pH cycle 6.5 -> 11.2 -> 6.5. Precipitation at pH 5.5 resulted in hydrogen bonds, hydrophobic interactions, and S-S bridges, whereas precipitation at pH 6.5 resulted only in the formation of hydrophobic interactions. The alkaline pH-shift isolation process severely rearranged the protein microstructure, with precipitation at pH 6.5 forming a finer, more homogeneous network than precipitation at pH 5.5. The former protein isolate also contained less lipid oxidation products and formed more deformable gels, without affecting protein yield.
lipid oxidation
characteristics
salt solubility
protein
acid
alkali
precipitation
recovery
pH-shift
gelation
trout oncorhynchus-mykiss
alkaline solubilization
cod muscle
storage
extraction
fish muscle proteins
Author
Sofia Marmon
Chalmers, Chemical and Biological Engineering, Life Sciences
A. Krona
SIK – the Swedish Institute for Food and Biotechnology
Maud Langton
SIK – the Swedish Institute for Food and Biotechnology
Ingrid Undeland
Chalmers, Chemical and Biological Engineering, Life Sciences
Journal of Agricultural and Food Chemistry
0021-8561 (ISSN) 1520-5118 (eISSN)
Vol. 60 32 7965-7972Subject Categories
Chemical Sciences
DOI
10.1021/jf301352s