Emulsions, Vegetable oils stability

Flavor emulsions are similarly stabilized by the viscosity produced upon addition of a vegetable gum, such as tragacanth, Irish moss extract, arabic, a cellulose gum, or one of the alginates, to the aqueous phase. Here the oil phase, in the form of the flavor, is in small proportion to the water. In the absence of the acetic acid, contained in the vinegar of the French dressing. 

The administration of metabolizable vegetable oils as concentrated sources of nutrition has proved to be valuable for patients who are debilitated and who are unable to take nourishment orally. In addition, oils such as soy bean oil provide a source of essential fatty acids which can be rapidly depleted in a patient after starvation for only a few days. Wretlind and his colleagues devised the phospholipids-stabilized soy oil emulsion now marketed as Intralipid (Pharmacia, now Pfizer, New York, NY) in Sweden during the 1960s and this product has been modified to carry oil-soluble drugs such as diazepam. In Europe this is marketed as Diazemuls and it may be anticipated that other drugs may be presented in the same or similar vehicles. 

Colloid stability enters our daily life in many different ways. A visit to the kitchen provides numerous examples of food colloids with microstructure and stability that are, in no small measure, an important aspect of their appeal to the palate For example, mayonnaise —a mixture of vegetable oil, egg yolk, and vinegar or lemon juice —is an emulsion of oil in water and is stable because the lecithin molecules in the egg yolk provide the needed stability. Milk is another example. We have seen others in the vignettes in Chapters 1 and 4. 

Instant whipped cream is based on the same foam-stabilizing principles but is packaged as a liquid (emulsion) and a gas under very high pressure in an aerosol can (see the footnote to Section 15.5). When the can s valve is released, the tremendous gas expansion through a fine orifice drives the formation of the foam topping. In non-dairy instant whipped topping products the cream is replaced by vegetable oil, water, and a number of emulsifiers, stabilizers, and preservative. 

Garti, N., Remon, G.F. 1984. Relationship between nature of vegetable oil, emulsifier and the stability of w/o emulsion. J. Food Technol. 19, 711-717. 

Salad dressings are made by emulsifying vegetable oil in an aqueous mixture that contains vinegar. When made at home, this emulsion is rather unstable the droplets coalesce relatively quickly, so one has to shake it before use. Commercial variants are usually stabilized by other components. 

Coffee Creamer. Emulsions of vegetable oil in an aqueous phase, including caseinates, are sold (as pasteurized liquid or as a spray-dried powder) as substitutes for cream for addition to coffee. Eor the liquid form, an emulsifier system of some combination of polysorbate 60, polysorbate 65, and sorbitan monostearate is used at a concentration of up to 0.4%. The spray-dried whitener uses the same emulsifier system, at a level of 1-3% of the dried powder. In both cases, sodium caseinate is probably the major stabilizer of the o/w emulsion. 

Other water-borne coatings include water-soluble emulsions, dispersions, and latex resins. Water-soluble resins are rare because most resins derived from vegetable oils are insoluble in water. The true emulsions are based on the emulsification of the oil or alkyd through either the action of a surfactant or a resin that has a surfactantlike character. The alkyd emulsions are readily prepared and can be used for OEM coatings and architectural applications. The submicron size droplets are stabilized by the thickeners (El-Aasser Sudol, 2004 Landfester, 2005 Landfester et al., 2004 Tsavalas et al., 2004 Weissenborn Motiejauskaite, 2000a,b). In dispersions, the resin is a solid and is dispersed in water. The latex resin is usually vinyl acetate, styrene, acrylates, or methacrylates radically copolymerized in a micelle to form particles 0.1 pm in diameter (Bloom et al., 2005 Brister et al., 2000 Jiratumnukul Van De Mark, 2000 Thames et al., 2005). 

The stability of an emulsion depends not only on the surfactant type, but also on die nature of the organic phase. To characterize die oil phase, the concept of a necessary (required) HLB number is used. This number is taken to be equal to die HLB number of die surfactant which ensures the best possible emulsification of the oil. Tables of necessary HLB numbers for various oils were published in Ref 258. For example, with respect to oil-in-water emulsions, the necessary HLB number is 17 for oleic acid, 15 for toluene, 14 for xylene and cetyl alcohol, 10.5 to 12 for mineral oils, 7.5 to 8 for vegetable oils, 5 to 7 for vaseline, and 4 for paraffin. In Refs 263 and 264 the necessary HLB numbers for various oils are compared with the relative dielectric permittivity of the oil e. In the series of saturated hydrocarbons, a weak inverse dependence between the necessary HLB number and e was observed (264) e.g., e =... 

---