Pseudoplasticity, elasticity help stabilize citrus drink emulsions.

As you may know, gums are water-soluble biopolymers consisting of high-molecular-weight polysaccharides. These emulsifiers, stabilizers and viscosity builders can be used to emulsify citrus-based drinks. Several hydrocolloids, such as gum arabic, modified starches, xanthan gum, propylene glycol alginate and guar gum, have been mentioned as food additives because they can retard the creaming and the sedimentation of oil droplets in citrus drink emulsions.

But what's not clear is the importance of the rheological properties linked with these gums when they're used as either emulsifiers or stabilizers in citrus drink emulsions. The aim of Canadian research was to highlight those rheological properties associated with stability in citrus drink emulsions as a function of both emulsifier and stabilizer gums with the absence of weighting agents.

Investigators prepared citrus drink emulsions using gum arabic and two types of modified starches-Purity Gum Be and Purity Gum 2000-as emulsifier gums at two different concentrations. A constant amount of vegetable oil was added to each gum solution. Then the scientists added even amounts of xanthan gum or xanthan and PGA gums, or xanthan, PGA and guar gums as stabilizers.

The researchers examined the flow and elastic properties of each prepared emulsion using commercial instrumentation. After diluting the emulsions in an acidified sugar solution, the rate of creaming and sedimentation were tested based on quantity and quality parameters.

Results indicate that, in addition to viscosity, the pseudoplasticity and elasticity of emulsions play a significant role in stabilizing citrus drink emulsions. The elasticity of the emulsions is related to the pseudoplasticity. The more elastic the emulsion, the more pseudoplastic and more stable it is as well. Emulsions prepared with Purity Gum Be, xanthan, PGA and guar gums had the greatest pseudoplasticity, elasticity and stability.

Further information. P. Fustier, Food Research and Development Center, Agriculture and Agri-Food Canada, 3600 Casavant Blvd. W., St. Hyacinthe, QC J2S 8E3, Canada; phone: [phone]; fax: [phone]; email: [e-mail].