Rheological and Physicochemical Studies on Emulsions Formulated with Chitosan Previously Dispersed in Aqueous Solutions of Lactic Acid

摘要

Chitosan, a natural, cationic polysaccharide, may be a hydrocolloid strategicto formulate acidic food products, as it can act as both bio-functional andtechnofunctional constituent. Typically, acetic acid is used to dispersechitosan in aqueous media, but the use of this acid is limited in foodformulations due to its flavor. In this study, chitosan was firstly dispersed(0.1% m/V) in lactic acid aqueous solutions (pH 3.0, 3.5 or 4.0), and thenevaluated regarding its thickener and emulsion stabilizer properties. O/Wemulsions were prepared and characterized in terms of rheological properties,droplets average diameters and droplets $\zeta$-potential. Emulsions containingchitosan were 3 times more viscous than controls without chitosan, andpresented storage modulus ($G'$) higher than loss modulus ($G''$). Furthermore,they displayed two different populations of droplets (average diameters of 44and 365 nm) and positive $\zeta$-potential values (+50 mV). Droplets averagediameters and $\zeta$-potential did not present significant changes ($p$ >0.05) after storage at 25 $^{\circ}$C during 7 days. This study showed that i)food organic acids other than acetic acid can be used to disperse chitosan fortechnological purposes, and ii) chitosan dispersed at very low concentrations(0.1% m/V) had relevant effects on rheological and physicochemical aspects offood-grade emulsions.