Tannin process

GUSTAVSON, K. H. (1956). The Chemistry of Tannin Processes, Academic Press, New York. 

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. 

A considerable quantity of oil can be extracted from waste material from shelling and processing plants, eg, the inedible kernels rejected during shelling and fragments of kernels recovered from shells. About 300 t of pecan oil and 300—600 t of English walnut oil are produced aimuaHy from such sources. The oil is refined and used for edible purposes or for the production of soap the cake is used in animal feeds (see Feeds and feed additives). Fmit-pit oils, which closely resemble and are often substituted for almond oil, are produced on a large scale for cosmetic and pharmaceutical purposes (143). For instance, leaves, bark, and pericarp of walnut may be used to manufacture vitamin C, medicines, dyes and tannin materials (144). 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

Chemical cleaning was suggested. A tannin-citric acid process was tested and produced good results. 

A final are we should discuss is color removal. This is perhaps the most difficult impurity to remove from waters. In surface waters color is associated with dissolved or colloidal suspensions of decayed vegetation and other colloidal suspensions. The composition of this material is largely tannins and lignins, the components that hold together the cellulose cells in vegetation. In addition to their undesirable appearance in drinking water, these organics can cause serious problems in downstream water purification processes. For examples ... 

Tannin-containing woods also darken with ammonia, a process which is usefully employed in darkening oak furniture by fuming . Ammonia stains can originate from animal glue, amino-type adhesives and concrete additive sources, particularly where damp conditions exist. 

Contact corrosion may be reduced by the presence of natural inhibitors, such as tannins, in the wood, and will be promoted by sulphates and chlorides in it, especially if mineral preserving processes involving these ions have been applied. 

Tannins make excellent BW inhibitors. They are multifunctional, possessing several characteristics that make them entirely suitable for the treatment of HW heating and LP steam boilers. They also are generally suitable for use in industrial and process WT boilers at pressures of up to 650 or even 950 psig. 

Under poor operational conditions, tannin chemistry is a particularly forgiving form of internal treatment because it tolerates FW with significant variations in quality. It is capable of delivering clean, corrosion-free waterside surfaces in many types of boilers, despite low FW temperatures, high oxygen levels, and hardness ingress. It is especially suitable for use in smaller facilities that do not have the benefit of full-time, trained operators, and under on-off, batch process, or permanent low-fire circumstances. 

Although tannins and lignins have been available for well over 50 years (and perhaps twice as long), they remain very useful as low-cost, general-purpose particulate-matter dispersants. Both tannins and lignins are coproducts of the wood pulping process... 

Tannin solutizer process. In this process, alkyl phenols or isobutyric acid is used in combination with tannic acid and caustic solution. The spent tannin solution is again regenerated by air blown into the solution. 

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