Sodium Caseinates with an Altered Isoelectric Point As Emulsifiers in Oil/Water Systems

Abstract

Sodium caseinate was chemically modified in order to alter its isoelectric point (pI). Negatively charged carboxylic groups were introduced to lower the pI, and positively charged amino groups to achieve the opposite. Different chemical amino acid modification approaches were studied and the modified proteins were characterized using free amino group assays, SDS-PAGE, MALDI-TOF mass spectrometry, and zeta potential measurements. Oil-in-water emulsions were prepared using these modified caseinates. The pH stability behavior of the emulsions was monitored, and interestingly, the stability of the emulsion could be modulated through steering the pI of caseinate. Using different modified caseinates, it was possible to create emulsions that were stable in the acid, neutral, and alkaline regions of the pH spectrum. The stability behavior of the emulsions correlated well with the theoretical and experimentally determined pI values of the caseinates. Storage stability of emulsions was also studied at pH values around 7, and emulsions made of modified caseinates showed storage stability similar to that of unmodified caseinate emulsions.

Development of tyrosinase-aided crosslinking procedure for stabilizing protein nanoparticles

“…Prior to crosslinking and acidification, the zeta potential of native SC 336 dispersion was approximately -32.4 mV (Fig. 5), which was consistent with previously 337 reported results (Ma, et al, 2009). Upon the introduction of CaCl 2 , the zeta potential 338 decreased significantly (in terms of its absolute value, same hereinafter) to -13.0 mV.…”

Collagens from the skin of arabesque greenling (Pleurogrammus azonus) solubilized with the aid of acetic acid and pepsin from albacore tuna (Thunnus alalunga) stomach

“…The p I of ASC and PSC was estimated to be 6.31 and 6.38, respectively. The pH where the ζ‐potential is zero corresponds to the p I of the protein,33 in which a net electrical charge of zero at the surface is obtained. At the p I of proteins, hydrophobic–hydrophobic interaction increased, thereby promoting the precipitation and aggregation of protein molecules 11.…”

Flocculation of protein-stabilized oil-in-water emulsions

“…While the extent of self-association in aqueous solution is reduced at high sucrose concentrations [73], the aggregation state is enhanced by increase in temperature, addition of calcium ions, and lowering of the pH towards pI. In fact, the main practical drawback of sodium caseinate as a food emulsifying agent is its insolubility close to pI; shifting the pI by chemical modification is one effective way to overcome this deficiency [74].…”