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Food Biophysics (2012) 7:155162 DOI 10.1007/s11483-012-9253-4
ORIGINAL ARTICLE
Rheology and Microstructure of Lecithin-Stabilized Tuna Oil Emulsions Containing Chitosan of Varying Concentration and Molecular Size
Supakchon Klongdee & Masubon Thongngam &
Utai Klinkesorn
Received: 25 November 2011 /Accepted: 16 March 2012 /Published online: 19 April 2012 # Springer Science+Business Media, LLC 2012
Abstract The purpose of these experiments was to determine the influence of chitosan concentration (00.25 wt.%) and molecular weight (120, 250 and 342.5 kDa) on the rheological properties and microstructure of lecithin-stabilized tuna oil emulsions. The apparent viscosity of the emulsions significantly increased with increasing chitosan concentration and molecular weight (P0.05). However, the studied chitosan chain lengths did not play a major role in determining the flow characteristics of the emulsions. The emulsions containing 0.10.25 wt.% chitosan were stable to droplet aggregation. All of these emulsions showed Newtonian flow with a flow behavior index of approximately 1. In the contrary, the 0.05 wt.% chitosan emulsions showed highly unstable droplet aggregation and a shear thinning behavior. The emulsion microstructure visualized using a confocal laser scanning microscope was consistent with the rheological data. These results have important implications for the utilization of tuna oil emulsions stabilized by lecithin-chitosan membranes in emulsion based food products.
Keywords Oil-in-water emulsion . Microstructure .
Rheology. Chitosan . Lecithin
Introduction
Polysaccharides are usually added to oil-in-water emulsions to create a desirable texture characteristic and to stabilize the emulsion droplets against gravitational separation.1 In most cases this is achieved either by enhancing the viscosity or by forming a gel network in a continuous phase.25 Furthermore, some of polysaccharide, e.g. gum arabic (Acacia senegal), modified starches, some kinds of pectin, can show surface activity as well.69 Polysaccharides are also capable of promoting droplet flocculation in emulsions through depletion and bridging mechanisms.10 For example, polysaccharide induced emulsions flocculation via depletion through the addition of excess non-adsorbing polysaccharides.3,1114 Where
as the origin of bridging flocculation may be caused by an electrostatic interaction between charged groups on different polymeric surfaces or the adsorption of the polymer to form a bridge between adjacent surfaces.12,15
Chitosan is the name used for low acetyl substituted forms of chitin, the second most abundant polysaccharide on earth after cellulose. It is composed primarily of glucosamine, known as (14)-2-amino-2-deoxy-(D-glucose) and has a...