Haze removal

Incipient hazes may not be removed at all by simple filtration. An array of fining procedures have been developed to achieve stable clarity in such cases. Fining agents ate substances that ate or become insoluble in wines, and, as they precipitate, adsorb or coptecipitation incipient sources of cloudiness. Ptopedy used, the fining agents themselves ate not retained in the wines and thein effect is subtractive rather than additive. 

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. 

Lipoproteins may denature on heating and if present during pasteurization can result in the formation of haze or turbidity in the final product. This material was removed traditionally by filtration through asbestos (qv) sheets (6) however, health hazards associated with asbestos have led to its replacement by alternative filter materials (23,37,193). These media have been less effective than asbestos and further measures have been required to ensure the visual clarity of albumin products, eg, further filtration developments for Hpid removal (194), preferential denaturation of contaminants using in-process heat treatment, and anion-exchange chromatography (49). 

Use of ultrafiltration (UF) membranes is becoming increasingly popular for clarification of apple juice. AH particulate matter and cloud is removed, but enzymes pass through the membrane as part of the clarified juice. Thus pasteurization before UF treatment to inactivate enzymes prevents haze formation from enzymatic activity. Retention of flavor volatiles is lower than that using a rack-and-frame press, but higher than that using rotary vacuum precoat-filtration (21). 

The crospovidones are easily compressed when anhydrous but readily regain their form upon exposure to moisture. This is an ideal situation for use in pharmaceutical tablet disintegration and they have found commercial appHcation in this technology. PVP strongly interacts with polyphenols, the crospovidones can readily remove them from beer, preventing subsequent interaction with beer proteins and the resulting formation of haze. The resin can be recovered and regenerated with dilute caustic. 

Alcoholic Solutions or Extracts. AlcohoHc extracts are prepared by dissolving the flavor-beating body ia a solution of alcohol and water. They may require filtration usiag filter aids to remove any iasoluble precipitates or oils that may form. AlcohoHc extracts are clear solutions and are used ia beverages that do not require a haze or cloudiness. 

The major purpose of ambient particulate sampling is to obtain mass concentration and chemical composition data, preferably as a function of particle diameter. This information is valuable for a variety of problems effects on human health, identification of particulate matter sources, understanding of atmospheric haze, and particle removal processes. 

A similar problem occurs with beer stabilization. A serious problem in the brewing industry is the tendency of some beers to develop hazes during long-term storage due to protein precipitation that is usually stimulated by small quantities of naturally occurring proanthocyanidin polyphenols. In the same way as observed for wine, the excess polyphenols are traditionally removed by treatment with insoluble PVPP, with the same resulting problems. To resolve the problems, several authors have proposed the use of laccase, which forms polyphenol complexes that may be removed by filtration or other separation means. 

Implementation A spectrum of the filtered coconut oil (Fig. 21.5) is obtained and subtracted from the spectrum of the oil containing the haze (solid) (Fig. 21.6). The haze in the crude coconut oil is filtered out of the oil and washed with hexane to remove residual oil. An infrared spectrum of the residue is obtained (Fig. 21.7). The spectra are essentially equivalent (Fig. 21.8). Identification is obtained by search against... 

Interpretation/report Coconut meal, not adequately removed during the oil extraction process, is the haze in the oil and is building up in the centrifuge. 

When methyl 2-cyanoacrylate was applied as an adhesive to rabbit or human eyes, some reports described corneal haze and inflammation other reports with highly purified material indicated less toxicity. Mistaken use in the eyes as eyedrops has caused immediate brief smarting and firm gluing of the eyelids together. Acetone on a swab can be used to unglue the lids and remove the glue from the cornea with minimal, if any, injury to the corneal epithelium. ... 

Chemical analysis of haze materials isolated from a beverage must be interpreted with caution because composition is often not well-related to cause. For example, beer hazes typically contain a high proportion of carbohydrate, with a modest amount of protein, and little polyphenol (Belleau and Dadic, 1981 Siebert et al., 1981). In order to prevent or delay haze formation, however, it is not necessary or helpful to remove carbohydrate. Reducing the amount of either protein or polyphenol typically has that effect. As a result, it appears that the large amount of carbohydrate found in the haze was coagulated with or adhered in some way to the protein-polyphenol haze backbone. 

The removal of macromolecules by ultrafiltration has often been used in the production of clear fruit juices and wine (Girard and Fukumoto, 2000). This treatment removes both proteins and polysaccharides. Ultrafiltration through a 10,000 Da cut-off membrane has been shown to stabilize wines against haze formation (Flores, 1990). 

Adsorbents that remove proteins or polyphenols are used to treat a number of beverages to delay the onset of haze formation. Protein adsorbents include bentonite and silica. Bentonite removes protein nonspecifically (see Fig. 2.19) and so is unsuitable for stabilizing beverages where foam is desirable (beer and champagne). Silica, on the other hand, has remarkable specificity for HA proteins while virtually sparing foam-active proteins in beer (Siebert and Lynn, 1997b) (see Fig. 2.20). Silica removes approximately 80% of the HA protein from unstabilized beer, while leaving foam-active protein nearly untouched at commercial treatment levels. 

Naphthenic acids occur primarily in distillate and some heavy fuel fractions. Topically, caustic treatment effectively removes these compounds. However, even after caustic treatment, alkali salts of heavier naphthenic acids may still remain oil soluble. In fuel, these compounds can act as very effective emulsifying agents. Fuel haze and particulate contamination can be due to these acid salts. Caustic solutions of various strengths can be used to wash fuel. Usually 10 to 20 vol% of a 5% to 10% caustic wash solution is effective for most applications. 

Fuel filtration through sand is sometimes used to physically remove water and particulate matter from fuel. As fuel passes downward through a filtration drum, water and particulates are removed. Water haze can be removed if fuel passes upward through a filtration drum. In severe cases, a 5-micron filter may be required to produce bright and clear fuel. 

The terms demulsifier and dehazer are often used interchangeably to describe compounds which break fuel emulsions or remove water-initiated haze from fuel. The terms can be distinguished as follows ... 

Dehazing refers to removal of water which has been dispersed throughout a fuel matrix. Haze created by water droplets can be removed by coalescence or by further dispersion through the action of a chemical dehazer. 

Demulsifiers are quite effective at clearing fuel of water-initiated haze. Occasionally, upon clearing the fuel, the water will be removed by interacting with a demulsifier to form an emulsion. This emulsion will precipitate from the fuel and settle to the bottom of a fuel storage tank. This emulsion can plug filters and clog small lines if not removed from the tank with the water bottoms. 

To remove water haze from cloudy fuel, refiners will sometimes use fuel dehazers. Some dehazers disperse water into fine droplets so that the water haze cannot be seen. The fuel, thus, appears bright and clear. However, if fuel treated with a dehazer is transported through a pipeline system, the dispersed water can sometimes cling to the pipeline wall and remain as water droplets. 

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