Emulsions foodstuffs

Sodium carboxymethylcellulose is acceptable for use in food, and is employed in a variety of foodstuffs. It is used to prevent formation of ice crystals in ice creams to control the consistency of cheese spreads to stabilise the emulsions needed in salad creams and to thicken toothpaste. 

The most widely studied deformable systems are emulsions. These can come in many forms, with oil in water (O/W) and water in oil (W/O) the most commonly encountered. However, there are multiple emulsions where oil or water droplets become trapped inside another drop such that they are W/O/W or O/W/O. Silicone oils can become incompatible at certain molecular weights and with different chemical substitutions and this can lead to oil in oil emulsions O/O. At high concentrations, typical of some pharmaceutical creams, cosmetics and foodstuffs the droplets are in contact and deform. Volume fractions in excess of 0.90 can be achieved. The drops are separated by thin surfactant films. Selfbodied systems are multicomponent systems in which the dispersion is a mixture of droplets and precipitated organic species such as a long chain alcohol. The solids can form part of the stabilising layer - these are called Pickering emulsions. 

The term food colloids can be applied to all edible multi-phase systems such as foams, gels, dispersions and emulsions. Therefore, most manufactured foodstuffs can be classified as food colloids, and some natural ones also (notably milk). One of the key features of such systems is that they require the addition of a combination of surface-active molecules and thickeners for control of their texture and shelf-life. To achieve the requirements of consumers and food technologists, various combinations of proteins and polysaccharides are routinely used. The structures formed by these biopolymers in the bulk aqueous phase and at the surface of droplets and bubbles determine the long-term stability and rheological properties of food colloids. These structures are determined by the nature of the various kinds of biopolymer-biopolymer interactions, as well as by the interactions of the biopolymers with other food ingredients such as low-molecular-weight surfactants (emulsifiers). 

Collagen and gelatin are of commercial importance. As insoluble collagen, this material may be cross-linked further by tanning and thus converted to leather. The soluble gelatins are used in the manufacture of foodstuffs, film emulsions, and glue. 

The Extrelut cleanup method is suitable for most foodstuffs, such as cheese, yogurt, and other samples that tend to form emulsions during extraction. The prepacked or refilled Extrelut column in a plastic tube consists of a wide-pore kieselgel column. A sample is homogenized in 0.5 N sulfuric acid, diluted with water, and applied onto the Extrelut column for at least 15 min. The absorbed preservatives are eluted with a chloroform - isopropanol (9 1) mixture, and the elu-ate is collected and evaporated carefully nearly to dryness. The last few milliliters of solvent are removed with a gentle flow of nitrogen to prevent substantial losses of BA and SA, which have relatively high vapor pressures. The residue is transferred with methanol into a 10-ml volumetric flask and diluted to volume with methanol. To speed up the dissolution, the use of an ultrasonic bath is recommended. The filtered extract is analyzed on a /zBondaPak Cl8 column, with a... 

Many foodstuffs consist of gelled emulsions, due to deliberate addition of gums and thickeners to increase the mass thickness (e.g., sausages) or due to denaturation of proteins to form protein micelles (e.g., cheese). Food emulsions containing water in oil have an internal water phase that is dispersed as droplets within an oil (or lipid) phase. The microorganisms are mostly found in the droplets (Verrips and Zaalberg, 1980 ... 

The use of activated carbon constitutes an integral part of the processing of many food products.1 It is adaptable to foodstuffs that are in a liquid state or can be dissolved in a suitable solvent. Activated carbon should not be applied to foods such as milk, butter, mayonnaise, in which a colloidal state must be preserved. When such a product—e.g., mayonnaise—is treated with carbon, the protective colloids are adsorbed and the emulsion is broken. 

A certain body of recent research has focused on the microstructural stability of protein stabilized oil-in-water emulsions that are structurally similar to recently developed foodstuffs (e.g., dairy alternative or fresh cheese type products, etc.). - The image of such an emulsion has been visualized by the use of Confocal Laser Scanning Microscopy (CSLM). However, not much research has been done yet on the oxidative destabilization of these emulsion systems. A better understanding of the factors monitoring the oxidative deterioration of emulsions would offer antioxidant strategies to improve the organoleptic and nutritional value of the related products. 

Already at an early stage in the development of surfaee and colloid science emulsions received a lot of attention. It was primarily clear that the properties of foodstuffs like milk, butter, and sauces contained dispersions of one liquid phase in another either oil (as fat) in water or water in oil (fat). Pioneering studies were performed by Baneroft in the first quarter of this century and his studies were followed up by Harkins and others, leading to a phenomenologieal knowledge that is still relevant today. Attempts were also made to understand and rationalize the experimental findings, but in this aspect progress was much slower. 

Microemulsions are widely used in cosmetics, cleansing products, foodstuffs, pharmaceuticals, and other products where ultrafine dispersion of one phase in another is desired. Other applications are tertiary oil recovery and polymer synthesis in a so-called emulsion polymerization process. 

In other applications, proteins are adsorbed by purpose, for example, as immobilized enzymes in biosensors and bioreactors, immunoglobulins in immunoassays, drugs in drug targeting and controlled release systems, and as stabilizers of dispersions, emulsions, and foams in foodstuffs, pharmaceuticals, and cosmetics. 

In most practical systems, as the ones mentioned in the introductory part of this chapter, stable foams and emulsions are preferred. However, sometimes the development of a foam or emulsion is inconvenient, such as in oil drilling, in fermentation tanks, and in infusion preparations. It could also be that we prefer a foam or emulsion of intermediate stability, for instance, when compounds such as flavors in foodstuffs or drugs in medical products have to be released from the dispersed phase at a desired rate. 

The polyol esters have many interesting properties which make them useful as additives in foodstuffs, cosmetics and pharmaceutical preparations, detergents, etc. It is obvious that the functional properties of polyolesters, such as emulsification and stabilisation of emulsions, improvement of texture or consistency of foodstuffs, crystal modification, detergent activity etc.,are dependent largely on their chemical structure type of polyol and fatty acid,mono- di- triester ratio, presence of soap and free polyols, etc. For each specific application, the chemical composition has to be optimized. 

General application areas for LR-NMR are given in Table 7.27. Low-resolution pulsed H NMR has found widespread application in a variety of QC laboratories and research establishments in the food industry, polymer and chemical industries, mineral oil industry, pharmaceutical and cosmetic industries, and medical research because it offers rapid analysis without the need for difficult sample preparation [30, 199,210]. Applications of LR-NMR in the food industry, e.g. as applied to measurement of moisture in foodstuffs, were described as long as 50 years ago [211], Applications now include measuring oil or fat in cosmetics, oilseeds, chocolate and other foodstuffs, solid-fat content, droplet size in oil-inwater emulsions total moisture content in seeds, milk powder, pharmaceuticals oils in/on polymers... 

Emulsions are a very important type of colloid, being found in foodstuffs, pharmaceutical products, cosmetics and agricultural products, for example. Emulsions in food colloids are so important that we defer a full discussion to the next section. Here we consider both emulsions and microemulsions. The two are distinguished by the fact that emulsions (macroemulsions) are thermodynamically unstable, whereas microemulsions are stable. In addition, the dynamics are distinct, the kinetics of exchange of molecules in and out of the stabilizing film being much greater in microemulsions than in emulsions. As su ested by the name, the dispersed phase in microemulsions is characterized by a smaller droplet size than in emulsions, and this historically was used to define them. Microemulsions are discnssed more fully below. 

One important role of surfactants in household products and foodstuffs is as an emulsifier. Emulsions are all around us in the kitchen, forming part of a wide variety of different sauces and creamy foods. When you whip air or oil into a liquid, how can the result be a stable phase What keeps hollandaise sauce or gravy from separating The answer is an emulsifier. Emulsifiers can take a variety of forms but are essentially just molecules that localize at the interface between the aqueous and oily components of the mixture. 

By modifying sorbitan s pattern of esterification to different degrees with ethers of ethylene oxide, products marketed under the trade name Tween are made (Fig. 39). As is the case of most compounds of this type, their industrial use depends on the nature of the fatty acid with which the alcohols are esterified, the degree of esterification, and the formation of polyoxyalkylene derivatives [93]. When such products are ethoxylated (with 20 mol of ethylene oxide), a hydrophilic range of sorbitan esters called polysorbates is produced. Owing to these factors, sorbitan esters can exhibit a wide range of HLB values, from 1.8 to 16.7, and can be used as W/O or O/W emulsions for numerous applications [92]. Many of the polysorbates have been used in feeding studies in animals. It was concluded that the polysorbates are no more toxic than many other foodstuffs. 

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