Albumens

Minerals, particularly Bentonite, ate used to remove proteins that tend to cause haze in white wines. The natural tannin of ted wines usually removes unstable proteins from them. Excess tannin and related phenols can be removed and haze from them prevented by addition of proteins or adsorbents such as polyvinylpyttohdone. Addition of protein such as gelatin along with tannic acid can even be used to remove other proteins from white wines. Egg whites or albumen ate often used to fine ted wines. Casein can be used for either process, because it becomes insoluble in acidic solutions like wines. 

Chemical Composition. From the point of view of leathermaking, hides consist of four broad classes of proteins coUagen, elastin, albumen, and keratin (3). The fats are triglycerides and mixed esters. The hides as received in a taimery contain water and a curing agent. Salt-cured cattie hides contain 40—50% water and 10—20% ordinary salt, NaCl. Surface dirt is usuaUy about 2—5 wt %. Cattie hides have 5—15% fats depending on the breed and source. The balance of the hide is protein (1). 

Albumen has the largest number of acid and basic groups. It is the most soluble of the proteins present in a hide. The albumen is not a fibrous material, however, and therefore has no value in the leather. Keratin is the protein of the hair and the outermost surface of the hide. Unless the hair is desired for the final product it is removed by chemical and/or physical means. The elastin has Htde acid- or base-binding capacity and is the least soluble of the proteins present. The lack of reactivity of the elastin is a detriment for most leather manufacture. The presence of elastin in the leather greatly limits the softness of the leather. 

Physical Properties. The egg is composed of three basic parts shell, whites (albumen), and yolk. Each of these components has its own membranes to keep the component intact and separate from the other components. The vitelline membrane surrounds the yolk, which in turn is surrounded by the chala2iferous layer of albumen, keeping the yolk in place. Egg white (albumen) consists of an outer thin layer next to the shell, an outer thick layer near the shell, an inner thin layer, and finally, an inner thick layer next to the yolk. Thick layers of albumen have a higher level of ovomucin in addition to natural proportions of all the other egg white proteins. This ovomucin breaks into shorter fibers when the egg white is blended on a high speed mixer (3), or when the egg white ages. Viscosity is gready reduced when the egg white is blended in this way. 

Heteropolyacids (HPA) are the unique class of inorganic complexes. They are widely used in different areas of science in biochemistry for the precipitation of albumens and alkaloids, in medicine as anticarcinogenic agents, in industry as catalysts. HPA are well known analytical reagents for determination of phosphoms, silica and arsenic, nitrogen-containing organic compounds, oxidants and reductants in solution etc. 

The separation of proteins and peptides mixtures is the objective of protein biochemisdy. Albumin (Mr 66 000) concentration in a biological fluid (seaim, urine or cerebrbrospinal fluid) is assayed as markers for a series disease, such as nephritic syndrome or chronic glomuleronephritis. In diabetic patients the progression of microalbuminuria is accompanied by an increase in urinary concentrations of human semm albumen. In normal the excretion of albumin is 20 (tg/ml, in pathology - 20-200 p.g/ml. 

Eiterungserreger, m. suppurative agent. Eitervergiftung, /. pyemia, eiterziehend, p.a. suppurative, pyogenic, Eiweiss, n. albumin albumen, white of egg protein. 

Eiweiss-bedarf, m. albumin requirement protein requirement, -driise, /. salivary gland, eiweiss-formig, a. albuminous, -hsltig, a. containing albumin (or albumen), albuminous containing protein. 

Eiweiss-spaltung, /. cleavage of albumin protein cleavage, proteolysis, -sparmittel, n. albumin sparer protein sparer, -stoff, m. albuminous substance, protein albumen albumin, -verbindung, /. albuminous compound, protein albuminate. 

Nitric add also reacts with proteins (casein in milk [test tube] and albumen in eggs) to give a characteristic yellow color. 

Cholegraphic contrast agents are ionic (acidic) iodi-nated molecules, which reversibly bind to albumen and are actively excreted into the bile. 

Plessit. A Ger blasting expl introduced during WW.I contg K chlorate with not more than 9.5% kerosene and 0.5% albumen. One variety, Wetter-Plessit III, used in coal mines, contained NaCl as well... 

The loss of structure by a protein is called denaturation. This structural change may be a loss of quaternary, tertiary, or secondary structure it may also be degradation of the primary structure by cleavage of the peptide bonds. Even mild heating can cause irreversible denaturation. When we cook an egg, the protein called albumen denatures into a white mass. The permanent waving of hair, which consists primarily of long a helices of the protein keratin, is a result of partial denaturation. 

Thirdly, a stable icing foam requires a tendency for the surface of the extended protein film to solidify, thereby giving structure and permanence to the foam. Egg albumen is a hydrophilic (water-loving) colloid, for it is readily soluble in water. However, when subjected to heat, egg albumen becomes insoluble in water or is said to be hydrophobic (water-hating). Through this phenomenon of changing solubility, egg whites make very stable foams if used at sufficient concentration. 

Other natural materials with expected intrinsic homogeneity properties that could be produced as CRMs include fractionated aerosols, conifer pollen, egg yolk or albumen, plankton of defined origin and size, and certain sediments. However, there are particular problems related to the collection and preparation, of large enough quantities of such matrices for their preparation as RMs. RM producers might initiate research and development to provide technical solutions to handle some of these problems. 

P. Messier, Protein Chemistry of Albumen Photographs, Topics in Photographic Preservation, 4, 124 135 (1991). 

Stabilising the foam is the more difficult part of the process. Some systems such as egg albumen will foam easily and set on cooking, which are desirable characteristics in the food industry. 

The layers between bubbles can be as thin as one molecule thick. Some systems, usually those involving eggs, are fairly robust. Others can easily be caused to collapse. Some years ago purified lactalbumin was offered as a substitute for egg albumin. The purified lactalbumin would foam up when whisked but the foam would collapse if more than a trace of fat was present. While there might be food systems where this would be acceptable it is not generally acceptable as a general replacement for egg albumen. 

In this work the name egg albumen is used to refer to the mixture of proteins in egg white. Around 54% of the protein in egg albumen is ovalbumin. The number of proteins identified in egg albumen will continue to increase with improved analytical techniques. Unless fractionated egg albumen proteins become available this will be of little consequence for confectionery makers. 

Properties of Egg Albumen. Egg albumen is normally used in foods for two reasons it whips into a foam and the foam can be set irreversibly by heat. One advantage of egg albumen is that it is relatively unaffected by the presence of fat. Fat in these systems acts as a foam breaker. Some other whipping agents are badly affected by the presence of fat. In confectionery systems egg albumen is usually set by beating the reconstituted egg albumen into a hot sugar syrup. The coagulation... 

The variation in the performance of different types of egg albumen in different systems is almost certainly caused by variations in the degree of denaturation of the protein. Those products that work best with fresh egg white clearly need an undenatured product. 

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