Clitor J.F. Souza

Complex coacervates obtained from peptide leucine and gum arabic: Formation and characterization

In this study, interactions between polypeptide-leucine (0.2% w/w) and gum arabic (0.03, 0.06, 0.09, 0.12, and 0.15% w/w) were examined at concentrations of NaCl (0, 0.01, 0.25, 0.3, 0.5mol/l) and at different pH values (from 1.0 to 12.0). Formation of insoluble complex coacervates was highest at pH 4.0. At pH 2.0, which is the pKa of the gum Arabic, the dissociation of precipitate occurred. The pHØ2 positively shifted with the addition of higher concentrations of salt. Samples containing 0.2% PL and 0.03% GA and no salt had higher turbidity and increased formation of precipitates showing greater turbidity and particle sizes. The Fourier transform infrared spectroscopy confirms the complex coacervate formation of leucine and gum arabic, and rheological measurements suggest the elastic behavior of 0.2% PL and 0.03% GA complex. Overall, the study suggests that complex coacervates of PLs could be one feasible ways of incorporating amino acids in food products.

Emulsion of systems containing egg yolk, polysaccharides and vegetable oil

This work characterizes the emulsifying properties of systems containing egg yolk (0.1; 1.0 and 2.5 % w/v) and polysaccharides (xanthan gum, carrageen, pectin and carboxymethylcellulose) and three different vegetable oils (sunflower, canola, and palm oils). Emulsifying activity and emulsion stability were measured of each combination and it was found the effect of the oil on emulsion stability correlated to the amount of monounsaturated fatty acid. Additionally, increased egg yolk concentration increased emulsifying activity by reducing coalescence of oil droplets. Lastly, 2.5% egg yolk and 0.2% polysaccharide generated emulsions with high emulsifying activity, excellent stability, and droplet size of 4.32 µm.

Complex coacervation between lysozyme and pectin: Effect of pH, salt, and biopolymer ratio

The complexation between lysozyme and pectin was studied by acidification using zeta potential, turbidity measurements and calorimetry titration. The complexes were analyzed in various NaCl concentrations with different ratios. At ratio 1:1 with 0.01M NaCl, is worth mentioning that the insoluble complexes were formed between pH 2.0 and 7.0, which represents a great range to apply this complex to different food matrices. When the ratio was increased from 1:1 to 3:1, the pH range between the pHφ1 and pHφ2 increased even more. When the NaCl concentration was increased from 0.01M to 0.2M, a progressive reduction of turbidity was observed. At 0.4M NaCl, there was total suppression of complex formation at ratio ≤ 3:1. The process of complex coacervate formation occurred in two different steps, presenting favorable enthalpic as well as entropic contributions. The positive entropy change is a strong indication that water molecules have been released from the complex surface, however the positive sign of TΔS suggests that hydrophobic interactions were involved in the interaction between lysozyme and pectin. Microscopy images of the samples revealed that the complexes presented a spheroid-like appearance which may contribute to possible future applications.