study of thermal properties, turbidity, effective factors on particle size and oscillatory rheology of pectin-caseinate biopolymer nanocomplexes

the biopolymer-based nanocomplexes are a group of nanocapsules that are used for encapsulation and control delivery of nutraceuticals. they are formed by binding of proteins and polysaccharides. in this study, complex formation between pectin and sodium caseinate was taken place by addition of pectin solutions(0.2, 0.45 and 0.7 % w/v) into the caseinate solutions (0.5, 1 and 1.5 % w/v) and adjusted their ph below isoelecteric point of sodium caseinate. the effect of various factors such as biopolymer concentration, salt concentration, temperature and time of ultrasound on the properties of pectin-casein nanocomplexes was investigated. differential scanning calorimetry (dsc) and particle size analyzer were used for study of complex formation and particle size determination, respectively. the results of dsc and turbidimetry showed complex formation between the pectin and casein at ph below 5 and the results of particle size showed formation of stable dispersion with a minimum size of 86 nm at ph 4.1, caseinate of 1 % w/v and pectin 0.45 % w/v concentration. the ultrasound for more than 1 min reduced particle size and addition of salt at high and low concentrations had different effects on the stability of the colloidal system. the lowering of temperature from 21 to 4°c resulted in smaller particle size of nanocomplexes. the oscillatory rheological results showed that with increasing pectin concentration, viscoelastic moduli were increased and loss moduli were higher than storage modulus.