Finings’ actions may be broadly categorized as either
electrostatic,
adsorbent,
ionic, or
enzymatic. The
electrostatic types comprise the vast majority; including all but activated carbon, fining yeast, PVPP, copper sulfate, pectinase and pectolase. Their purpose is to selectively remove proteins,
tannins (polyphenolics) and coloring particles (melanoidins). They must be used as a
batch technique, as opposed to
flow-through processing methods such as
filters. Their particles each have an
electric charge which is attracted to the oppositely charged particles of the
colloidal dispersion that they are breaking. The result is that the two substances become bound as a stable
complex; their net charge becoming neutral. Thus the agglomeration of a semi-solid follows, which may be separated from the beverage either as a floating or settled mass. The only
adsorbent types of finings in use are
activated carbon and specialized fining yeasts. Although activated carbon may be implemented as a flow-through filter, it is also commonly utilized as a batch ingredient, which later must be separated and discarded from the beverage. Activated carbon can remove
benzenoid compounds and all classes of
polyphenols non-specifically, either completely or partially, thus decolorizing and deodorizing juices and wines. Traditionally, yeast fining has involved the addition of hydrated yeasts used as
adsorption agents. Consisting of approximately 30% protein, yeast cell walls have a
chemical affinity with wine compounds, such as those that may be polyphenolic or metallic. Indeed, yeast fining is a practical means of removing excess copper ions (greater than 0.5 mg/L) when copper sulfate is used to bind selected
volatile sulfur compounds (VSCs). The ionic finings are copper sulfate and PVPP. When dissolved in aqueous beverages, copper sulfate's copper ions can
chemically bind undesirable sulfides. The resulting
complexes must be removed by other finings. The action of PVPP appears to be through the formation of
hydrogen bonds between its
carbonyl groups and the phenolic hydrogens of the polyphenols. It attracts the low molecular weight polyphenols rather than the condensed tannins and
leucoanthocyanins that are removed by gelatin. The enzymatic finings are pectic and pectinase. They aid in destroying the large
polysaccharide molecule named
pectin, which otherwise causes haze in fruit wines and juices. They are among the few finings that are added
before juices are
fermented. ==Nutritional concerns==