Haze formation

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). 

Schleier, m. veil haze screen, curtain (as of smoke) lawn (the fabric) (Pkotog.) fog cloudiness, turbidity, -bildimg, /. haze formation, fogging. 

An important issue in caramel applications is their compatibility with food. The compatibility is defined as the absence of flocculation, precipitation, and haze formation. These effects are the results of colloidal interactions between charged high molecular weight components of caramel and the food components thus the charge of caramel is essential for specific food applications. ... 

Rhamnogalacturonase may be useful in the prevention of haze formation in apple Juice concentrates. In combination with other enzymes it mi t improve liquefaction, resulting in increase juice yield and clarification. 

Whitaker JR (1984) Pectic substances, pectic enzymes and haze formation in fruit juices. Enzyme Microb Technol 6 341-349... 

R. W. Jahnke, J. Kreutner and G. Ross. Con-tent/container interactions phenomenon of haze formation on reconstitution of solids for parenteral use. Int. J. Pharm., 77, 47 (1991). 

The possibility of widespread haze formation by sunlight irradiation of terpenoid compounds from vegetation was first suggested by Went. Went, Rasmussen and Went, and Rasmussen estimated the annual worldwide contribution of forest hydrocarbon emission and con-... 

Wilson, W. E., Jr., W. E. Schwartz, and G. W. Kinzer. Haze Formation—Its Nature and Origin. Columbus, Ohio Battelle Columbus Laboratories, 1972. 77 pp. 

Many deleterious effects have been associated with photochemically polluted air ozone is deflnitely associated with respiratory problems, plant damage, and material damage PAN has deflnitely been associated with plant damage, and some other members of this class of chemical compounds have been associated with eye irritation the hydroxyl radical is considered to be an important factor in the conversion of gas-phase intermediates to end products, such as sulfur dioxide to particulate sulfate the particulate complex is responsible for haze formation and has also been associated with eye irritation and respiratory effects. The aldehydes have been associated with eye irritation. Ozone and PAN themselves do not cause eye irritation. For purposes of control, much more research is needed, in order to relate the laboratory data about the concentrations of these various materials that have significant effects to their formation in the atmosphere from emission and their atmospheric distribution. The lack of convenient measurement methods has hindered progress in gaining this understanding. 

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. 

Because warming can often disperse protein-polyphenol hazes, it is clear that covalent bonding is not involved in their formation. Asano et al. demonstrated that protein-polyphenol haze formation is inhibited by the nonpolar solvent dioxane and the hydrogen bond acceptor dimethylforma-mide (DMF), but not by a solution of sodium chloride (Asano et al., 1982). 

The time course of protein-polyphenol haze development in many packaged clear beverages has a two-phase pattern (see, for example, Fig. 2.17). At first no observable change occurs for some time. After this, haze formation begins and follows an essentially linear development rate. This phenomenon has been reported in beer (McMurrough et al., 1992) as well as apple juice, grape juice, and cranberry juice cocktail (Siebert, 1999, 2006). 

VI. ANALYSES RELATED TO PROTEIN-POLYPHENOL HAZE FORMATION... 

It is normal to employ beverage-processing steps that lead to a reduction in the likelihood of haze formation, or at least a delay the onset of haze development beyond the intended shelf life of a product. 

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. 

At one time, broad spectrum proteolytic enzymes (mainly papain and bromelain) were widely used to delay or minimize haze formation in beer (de Clerck, 1969). The enzymes cleaved protein chains, that when... 

Asano, K., Shinagawa, K., and Hashimoto, N. (1982). Characterization of haze-forming proteins of beer and their roles in chill haze formation. /. Am. Soc. Brew. Chem. 40,147-154. 

Eastmond, R. and Gardner, R. J. (1974). Effect of various polyphenols on the rate of haze formation in beer. J. Inst. Brew. 80,192-200. 

Gramshaw, J. W. (1969). Beer polyphenols and the chemical basis of haze formation. I. Phenolic constituents of beer and its raw materials. Tech. Q. Master Brew. Assoc. Am. 6, 239-251. 

Another typical enzyme application in the production of beer is the use of proteases, such as papain or laccases in chill-proofing, which is the prevention of haze formation that can occur at low temperatures during or after the maturation of beer. Finally, to... 

Phenolic compounds are of interest due to their potential contribution to the taste (astrin-gency, bitterness, and sourness) and formation of off-flavor in foods, including tea, coffee, and various fruit juices, during storage. Their influence on the appearance of food products, such as haze formation and discoloration associated with browning in apple and grape products, is also significant. Furthermore, analysis of these phenolic compounds can permit taxonomic classification of the source of foods. The importance of each phenolic compound and its association with the quality of various foods is described further in Sec. IV, on food applications. 

The addition of an alkanolamine, such as diethanolamine, to TYZOR TBT, as well as the use of a less moisture-sensitive alkanolamine titanate complex such as TYZOR TE, has been reported to prolong catalyst life and minimize haze formation in the polymer (475—476). Several excellent papers are available that discuss the kinetics and mechanism of titanate-catalyzed esterification and polycondensation reactions (477—484). 

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