A review with 83 refs. is given. Research activities carried out on various gums as emulsifiers are discussed and questions related to adsorption at interfaces of certain gums are clarified. Gum arabic, galactomannans (guar, locust bean, and fenugreek gum), xanthan gum, Portulaca oleracea and Opitus ficus gums, tragacanth gum, and pectins are included. Adsorption isotherms and the role of proteins in galactomannans, mechanistic considerations, protein-polysaccharide interactions, the stabilization by solid particles (colloidal microcryst. cellulose as emulsifier), and biosurfactants are discussed. [on SciFinder(R)]
It is well documented that weak or strong interactions between macromols. such as proteins or polysaccharides can synergistically improve the emulsifying capabilities of each of the biopolymers. A study was made to explore the nature of the adsorbed layer in emulsions formed in the presence of casein and a new anionic hydrocolloid extd. from Portulaca oleracea in several emulsification protocols. Electrophoretic mobility of medium chain triglyceride oil emulsion droplets and the corresponding adsorbing creamed phases were measured. The zeta potential magnitudes were calcd. in view of the possible pH dependent ionic-hydrogen bonding interactions between casein and a new ionic gum at the oil-water interfaces. Emulsions stability were detd. from the emulsification stability indexes and emulsification activity index. It was found that POG can adsorb by itself or together with casein onto the oil-water interface. Displacement of the POG from the interface by the casein will take place at pH values that will enhance repulsion forces between the biopolymers. However, complementary adsorption of a possible casein-POG complex will occur if the pH is enhancing the strong attraction interaction between the two biopolymers. The attraction forces between the two biopolymers will enhance the stability of oil-in-water emulsions formed in the presence of the two macromol. amphiphiles. [on SciFinder(R)]
New crystal forms of aspartame were prepd. by using microemulsions comprising: (a) introducing aspartame into a microemulsion formed from an oil phase, an aq. phase and at least one emulsifier; (b) destabilizing the microemulsion to effect recrystn. of aspartame; (c) sepg. solid phase crystals from the liq. phase in which they are contained; and (d) cleaning the crystals to remove traces of the oil phase and surfactant. Thus, aspartame (22 g) was solubilized by mech. stirring in a microemulsion contg. 234 g (65%) of isooctane, 36 g (10%) of water and 90 g (25%) AOT at 65°. The microemulsion was then cooled at a rate of 1° per min with const. sirring to a final temp. of 5° and stirred at this temp. for an addnl. two hours to induce crystn. The crystal gave an X-ray pattern characteristic of form III aspartame. [on SciFinder(R)]
The properties of a new gum extd. from the leaves of an edible herb (Portulaca oleracea) were studied. The biopolymer is a relatively small mol. wt. polysaccharide and exhibits significant charge d. at pH \textgreater 2. The extd. gum has surface and interfacial properties derived from its chem. compn. and structure. The Portulaca oleracea gum (POG) adsorbs onto the oil (n-tetradecane or soya) interfaces and stabilizes oil-in-water emulsions. Emulsions (5 wt% oil and 0.7 wt% gum) are stable to flocculation and coalescence at room temp. (for a year) but upon heating the gum desorbs and the emulsion coalesces. Mechanistic considerations regarding its adsorption isotherms, the role of the residual proteinaceous matter contaminating the polysaccharide and the charge are discussed. POG is a good example of a new gum that can be considered as a food emulsifier. [on SciFinder(R)]
The most complex emulsions are those of foods and, therefore, are difficult to stabilize. An infinite no. of microstructures of combinations of proteins, carbohydrates, fats and lipids are present in food systems. There is an increasing awareness of many investigators to the relevance of the principles of colloid and surface science to many of the technol. problems related to advanced foods. Amphiphilic mols. play a key role in the stabilization of many of the food colloids. It is, therefore, very important to understand the interfacial behavior of these mols. and to select the proper ones for the proper activity. Synthetic surfactants and emulsifiers are widely used in many of our foods, but, it becomes very important to replace them by natural mols. with good health records. The following review with 49 refs. discusses the main natural occurring mols. that are in use today and the future trends in this area. Monomeric emulsifiers such as mono- and diglycerides, lecithins and lysolecithins are still key players. Glycolipids are present only in very minor concns. in plants and animals and therefore are not com. available. Saponins are a very interesting group of materials with increasing potential. The polymeric amphiphilic compds. are "native" and enzymically modified proteins. However, in situ products chem. modified by a Maillard reaction can also be used as emulsifiers. The most interesting new emulsifiers are some selected hydrocolloids that exhibit surface properties and emulsification capabilities. Enzymically modified hydrocolloids show significant promise. Bio-surfactants have also been studied and considered as emulsifiers, but are not food grade products. New trends and progress will also be discussed. [on SciFinder(R)]
A galactomannan isolated from fenugreek seed has ≥50 repeating units of mannose and galactose in a ratio of 0.5-1.0 and 1.8-1.0, a protein content of ≤20%, a saponin content of ≤5%, and a lipid content of ≤1%, and is useful as an active ingredient in nutraceutical and cosmetic products. [on SciFinder(R)]
Phospholipase A2 (PLA2) was used to hydrolyze phosphatidylcholine (PC) in microemulsions. Phase diagrams were constructed for mixts. of alcs. (C2-C6), medium chain triglycerides (tricaprylin, TC) or vegetable oils, PC and water, and areas corresponding to isotropic systems were identified. The PC hydrolysis was carried out with high yields at various PC/(TC+alc.) compns. within the areas of isotropic systems at increasing amts. of solubilized water. The initial reaction rates depended on the aggregation state of the PC (size and nature of microemulsion structures), as well as on temp. and mode of calcium addn. At low enzyme concns., hydrolysis was preceded by a "lag phase" followed by an abrupt increase in rate. By contrast, no latency was obsd. at higher PLA2 PC ratios and the rate was significantly higher. The easy access of the enzyme to the substrate in the curved phospholipid-contg. microemulsion particles facilitate activation of the enzyme and "pushes" the reaction to completion. Hence, these microemulsions can serve as microreactors for the enzymic high yield hydrolysis. [on SciFinder(R)]
Two techniques for extn. and purifn. were used in order to obtain a purified saponins ext. from several sources (fenugreek, soybean, locust bean and sesame). The results indicate that fenugreek steroid saponins ext. has the best surface properties and reduces the surface tension to 33.3 mN/m and the tetradecane-water interfacial tension from 44 mN/m to 7.5 mN/m. The HLB value was 18. Three different types of oil (n-tetradecane, soybean oil, tricaprylin) were emulsified with a 6 wt% aq. soln. of saponins to give an av. droplet size of 0.7 $μ$m (stable after month). An effective synergism is seen when these emulsions were prepd. with sucrose fatty acid esters as co-surfactant. Foaming power was also evaluated. [on SciFinder(R)]
N Garti, Clement, V, Leser, M, Aserin, A, and Fanun, M. 1999.
“Sucrose Ester Microemulsions.”. Journal Of Molecular Liquids, 80, 2,3, Pp. 253–296. doi:10.1016/S0167-7322(99)80010-5.
A review with 95 refs. Sucrose esters are biodegradable surfactants that can be manufd. in various hydrophilic-lipophilic properties using different fatty acids varying in their lipophilic chain length. These surfactants are used in different industries including pharmaceutical, food processing, detergents, agricultural and others. Few no. of works had been done using sucrose esters in microemulsions. In this review we tried to introduce the relevant works that enlighten the behavior of sucrose esters in phase diagrams prepd. using different oils and medium chain alcs. We hope that this review article can be an aid to those researchers interested in microemulsions based on sucrose esters and their applications. [on SciFinder(R)]
