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Document Type:Latin Dissertation
Language of Document:English
Record Number:55042
Doc. No:TL24996
Call number:‭NR32246‬
Main Entry:Ali R. Taherian
Title & Author:Rheology and stability of beverage emulsions in concentrated and diluted formsAli R. Taherian
College:McGill University (Canada)
Date:2007
Degree:Ph.D.
student score:2007
Page No:174
Abstract:Consumer's demand for more natural and high quality food products products, presenting health benefits, has increased over the years. Besides the nutritional aspects, an appealing appearance and texture is also required. Cloudiness or opacity (cloudy appearance) is an important citrus drinks property (orange, lime, lemon, etc.), since it gives natural fruit juice appeal. This property can be achieved through addition of clouding agents, which also help in uniform distribution of flavors throughout the liquid beverage. A common problem in the beverage industry is producing cloud or flavor emulsions that remain stable over the desired shelf life. Beverage cloud emulsions are oil-in-water emulsions to provide cloudiness and are prepared in a concentrated form, but diluted prior to the consumption. Optical and rheological properties of beverage cloud emulsions as a function of water-phase and oil-phase concentrations were investigated. The specific gravity of phases, particle size distribution and creaming stability of prepared emulsions in diluted forms were evaluated. The rate of cloud emulsion creaming by determining the rheology of water phase, difference in specific gravities of the phases and droplet properties of the emulsion in presence and absence of weighting agents (sucrose acetate isobutyrate and brominated vegetable oil) or/and xanthan gum was studied. Flow and dynamic rheological properties of single-phases and emulsions containing modified starch and arabic gum as surface active hydrocolloids as well as xanthan and tragacanth as stabilizers gums were investigated. Finally, stability of cloud emulsions in orange juice drink was examined. Oil-phase concentration had a significant effect (P < 0.05) on increasing the opacity of emulsion. Raise in viscosity of emulsions was more pronounced as oil concentration increased and shear thinning behavior of oil added emulsions was associated with droplet flocculation. Creaming in acidified sugar solution of 11°Bx and pH 3 was observed when the oil-phase specific gravity decreased and sedimentation occurred at the lower viscosity of water phase. Addition of xanthan gum into the water phase decreased the flow behavior index (n) form 0.88 down to 0.31 and increased elastic modulus (G') over 20 times at elevated frequency (ω = 50 rad/s) and perk up the stability of the emulsion. The xanthan gum added emulsion indicated smaller average particle size and demonstrated 14 and 5 times slower separation compared to the emulsions without or with the addition of weighting agents respectively. Starch-xanthan stabilized emulsion and associated water phase at 1.5:1 surface active gum to oil ratio demonstrated viscoelastic behavior (G' ≥ G") with lower droplets coalescence and creaming rates, 0.013 nm/day and 0.02 percent backscattering/day respectively. Conversely, arabic-xanthan stabilized emulsion at 1:1 gum to oil ratio showed the highest rate of droplets coalescence at 0.057 rim/day and greater degree of creaming at 0.61 percent transmission/day. While creaming were associated with arabic gum stabilized emulsions, after 3 month storage, modified starch illustrated appropriate shelf stability with no sign of creaming in orange juice drink.
Subject:Biological sciences; Beverage; Clouding agents; Emulsions; Rheology; Stabilizer gums; Weighting agents; Food science; 0359:Food science
Added Entry:McGill University (Canada)