Abstract
The present work was aimed to investigate the effect of polyphenols on functional and rheological properties of protein isolates obtained from sunflower seed and kernel. Protein isolates were obtained from both dephenolized and undephenolized meals of seed and kernel by isoelectric precipitation. Protein isolates from dephenolized meals had higher percentage of proteins than protein isolates from undephenolized meals. Concentration of proteins in kernel protein isolates was higher as compared to seed protein isolates. The colour of kernel protein isolates improved considerably after removal of polyphenols, however, colour of seed protein isolates did not improve to a larger extent. Higher solubility, emulsifying activity, emulsion stability, dispersibility, foaming capacity and foam stability were found in protein isolates obtained from dephenolized meal. Lowest values of these properties were obtained at isoelectric point and highest at alkaline pH. Water binding capacity was higher for protein isolates with higher phenolic content and further increased toward alkaline pH. Least gelation concentration was lower for protein isolates with higher percentage of protein and lower phenolic content. Polyphenols in protein isolates decreased their available lysine content and reduced both the storage modulus and loss modulus of protein dispersions and formed more viscous and less elastic gels.
Published Version
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