Composition and rheological properties of beta-Lactoglobulin/pectin coacervates: effects of salt concentration and initial protein/polysaccharide ratio.
The composition and rheological properties of beta-lactoglobulin/pectin coacervates have shown significant correlations with sodium chloride concentration (C(NaCl)) and initial protein/polysaccharide ratio (r). An increase of C(NaCl) from 0.01 to 0.21 M at r = 5:1 leads to the increase in both beta-lactoglobulin and pectin contents in the coacervates, which can be explained in terms of salt-enhanced effect at lower salt concentrations. Further increase of C(NaCl) from 0.21 to 0.41 M decreases the proportions of these two biopolymers in the coacervates, exhibiting salt-reduced effect at higher salt concentrations. Moreover, the stronger self-aggregation of beta-lactoglobulin with increasing salt concentration gives rise to a decreasing actual protein/polysaccharide ratio in the coacervates at 0.01-0.21 M C(NaCl) and r = 5:1. An increase of r from 5:1 to 40:1 often increases the actual amount of pectin chains in beta-lactoglobulin/pectin coacervates, but it exhibits a maximum in beta-lactoglobulin content at r = 20:1. A much higher storage modulus (G') than loss modulus (G' ') for all beta-lactoglobulin/pectin coacervates suggests the formation of highly interconnected gel-like structure. The values of G' increase as C(NaCl) increases from 0.01 to 0.21 M, whereas a further increase of C(NaCl) from 0.21 to 0.41 M causes G' values to decrease to much lower values. These results further disclose the salt-enhanced effect and the salt-reduced effect at low and high salt concentrations, respectively. On the other hand, increasing r from 5:1 to 40:1 favors the formation of stronger gel-like beta-lactoglobulin/pectin coacervates, which mainly originates from the higher actual amount of pectin chains in beta-lactoglobulin/pectin coacervates at higher r values.
Wang
Xiaoyong
X
Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, New Jersey 08901, USA.
Lee
Jooyoung
J
Wang
Yu-Wen
YW
Huang
Qingrong
Q
D001671:Biochemistry / Q000379:methods*; D001704:Biopolymers / Q000737:chemistry; D002240:Carbohydrate Sequence; D007782:Lactoglobulins / Q000737:chemistry*; D046911:Macromolecular Substances; D008956:Models, Chemical; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010368:Pectins / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D012212:Rheology / Q000379:methods*; D012492:Salts / Q000494:pharmacology*
D001704:Biopolymers; D007782:Lactoglobulins; D046911:Macromolecular Substances; D011134:Polysaccharides; D012492:Salts; D010368:Pectins