food and beverage service

1. THE USE OF GELATINE IN WINE FINING
SYNOPSIS
The basic chemistry of protein is developed to enable an understanding of its fining
reactions in beverage clarification. Results of various European and South African wine
fining experiments are presented. The efficiency of both very high and very low
molecular weight gelatins are discussed and it is proposed that protein isoelectric point
is a more important attribute in determining fining performance than is the Bloom
strength of the gelatine.
Introduction.
Beverages like wine, cider and unfermented fruit juices contain insoluble matter which
imparts a haze to the beverage which is often not practical to remove by filtration.
The process of haze removal is known as fining. It involves the formation of a floccular
precipitate in the beverage which will absorb the natural haze forming constituents while
settling. After a settling period, the supernatant can be withdrawn and given a polishing
filtration prior to sale.
It is important that the settling process be efficient in the removal of natural haze. It must
also be reasonably rapid, and the loss of salable product in the sediment or lees should
be minimal. Finally, the beverage, once clarified, should remain clear and the
clarification or fining process should not have any undesirable effect like the removal of
wanted flavourants or the addition of unwanted flavour components.
Gelatine has been used for the clarification or fining of wine since the Roman civilization
(Ringland 1983) and probably before that as well. At that time the chemistry of the
process was certainly very poorly understood, and hence it is not surprising that the
process is often considered to be an art rather than a science, and like all arts, the
process can be surrounded by misconceptions which can result in inefficiency. Hence, it

2. is the intention to review the chemistry of fining and to present some results of South
African investigations and compare these with results obtained in Europe and to attempt
to account for the discrepancies.
Fining Reactions.
The primary reaction occurring with gelatine is a complex formation between
polyphenols in the wine and the protein of gelatine to give the desired floccular
precipitate.
The second reaction, less well understood, but equally important, is the complex
formation between the natural proteins of the wine and the added protein, gelatin.
The third reaction is between bentonite or silica sol (which should be added after the
gelatin) which absorbs or complexes with any residual dissolved protein, be it gelatin or
natural protein in the beverage.
The Nature of Gelatin.
Gelatin is a protein, that is, it is a polymer of amino acids joined together by peptide
bonds as shown in Figure 1a. Hence, proteins can be depicted as long molecules with
many different side chains (Figure 1b), which accounts for their varying properties.

3. Figure 1. Developing concepts of protein structure, a) the formation of the peptide bond
and the polypeptide, b) peptide side chains, c) peptides as amphoteric compounds and d)
charge on the peptide chain.
The side chains can be, for example:
Neutral Side Chains
R = -H Glycine
R = -CH3 Alanine

4. R =
Tyrosine
Cationic Side Chains
R = -CH2 - CH2 - CH2 - NH2 Lysine
Anionic Side Chains
R = -CH2 - COOH Aspartic Acid
Cyclic Side Chains
Proline
Proline is very important in that it imparts a twist to the chain and affects the shape of
the protein molecule and its rigidity.
The protein chain is more accurately depicted in Figure 1c, that is the molecule is
amphoteric and can carry either a positive or negative charge depending on the pH of
the medium. In wine and beverages at a pH of 3.6, one would expect most of the amino
groups to be positively charged and most of the acidic groups to be uncharged as in
Figure 1d.
The molecule would then behave as a cation provided the pH was below the isoelectric
point, i.e. It would attract and form polar associates with anions in solution. In addition
proteins form associations due to hydrogen bonding using the negatively charged
oxygen and nitrogen atoms in the molecules.
The isoelectric point (pI) of a protein is that pH at which the protein will not migrate in an
electric field. This is due to the fact that at that pH the molecule carries an equality of
positive and negative charges, i.e. the molecule is isoionic, in the absence of added
ions other than hydrogen and hydroxyl ions in solution. Gelatin, is rather unique in that it

5. can have an isoelectric point anywhere between pH 9 and pH 5, depending upon the
source and method of production.
Type A gelatins are usually derived from acid pretreated pigskin and have isoelectric
points between 6 and 9, with the high gel strength (Bloom strength) gelatins having the
higher pI and the low Bloom strength gelatins having a pI closer to 6. Gelatins derived
from limed hide or limed ossein are known as Type B gelatins and all of them have a pI
close to 5. The significance of pI is, of course, that the higher the pI, the greater the
cationic charge on the molecule at a beverage pH of say 3.6. In other words, at pH 3.6,
all gelatins would be positively charged, but the charge density would be far higher for
high pI gelatins.
Phenol - Protein reaction.
Both tannins and anthocyanins in beverages are molecules containing benzene rings
with adjacent hydroxyl groups as shown by the gallic group (Figure 2) which are
proposed as the major source of the hydrogen bonds which are the basis of complex
formation between gelatin and tannins or anthocyanins in beverages (Figure 3):
Figure 2. Galloyl group, a major constituent of tannins.

6. Figure 3. Polyphenol - peptide hydrogen bonding (Ringland 1983).
Gelatin is held to be particularly suited to hydrogen bonding because one third of the
amino acids are glycine, where R = H , and hence steric hindrance to hydrogen bonding
would be far less than with proteins containing less glycine. However, the tannin/gelatin
complex is also very pH dependent and disappears at approximately pH 8, which would
be due to both molecules becoming negatively charged and hence mutually repulsive.
Hence, the role of polar bonding between molecules of dissimilar charge must not be
overlooked.
Protein - Protein Interaction.
Beverage proteins would be derived from the enzymes which are responsible for the
diversity of the biological processes occurring prior to and during conversion of the
substrate into a beverage. In beer the proteins would be in the form of wort enzymes
needed to convert starch into glucose and then alcohol. In wine the growth and ripening
enzymes of the grape and the fermentation enzymes would provide the protein. Both
beer and wine makers know that, with time, these proteins associate to form insoluble
precipitates, i.e. they are responsible for "protein instability". It is worth noting that for
beer fining, Isinglass, a close relative of gelatin derived from fish swim bladder is most
effective. This protein has an extremely high molecular weight and a pI of 4.5 to 4.8 (i.e.
higher than the pH of beer). (Vickers & Bracher 1966).
For protein-protein interaction it is necessary that the two proteins be of opposite charge
at the beverage pH for polar association to occur. This association leads to a reduction
of hydrophilic sites and hence precipitation. Also, further hydrophobic bonding due to
association of hydrophobic sites in aqueous medium can lead to an increase in effective
molecular weight and precipitation.

7. It would be wrong to neglect to mention the two other proteins that have received a fair
amount of use in fining, namely egg albumin and casein. However in both these cases
the floc formation is due to the insolubility of the fining protein at pHs below their pIs,
hence the fining action is not the same as in the case of gelatin which is soluble at all
pHs, even at its isoelectric pH.
Gelatin Fining.
In Europe, from where we inherited the art of wine making, most of the available gelatin
is Type A pigskin gelatin. Ossein gelatin, having a higher viscosity, is mainly employed
in film forming applications, and in Europe there has been a tendency to think that cattle
hide gelatin was only suitable for use as glue. In RSA however, gelatin is only made
from cattle hide and is thus Type B, and we would contend that it is in no way inferior to
Type A, especially in fining applications!
There is a wealth of European data which appears to show quite conclusively that low
Bloom strength gelatin is optimum for fining, as shown in Table 1. This will come as no
surprise to the technologist trained in Europe, and this is so much a dictate of the art
that it requires a real "Thomas" to consider the possibility of reinventing the wheel.
Table 2, however from the study of W. Bestbier of KWV, shows that there really is no
detectable difference in performance between the use of gelatins of between 100g and
275g Bloom strength. This applied to all parameters tested, i.e. sediment volume, clarity
of supernatant and protein stability. Hence the gelatin to use is determined by
economics alone and once again it looks as though the Europeans are correct, because
traditionally, the lowest Bloom strength gelatins command the lowest price. However,
there is one vintner who will not be swayed from the use of "Superfine" 250-270 Bloom
strength gelatin. Such a gelatin, of very high molecular weight, is partly insoluble and
forms a coacervate in 10 % alcohol solution. Hence, this user of gelatin is managing to
add the insoluble floc fining action of egg albumin or casein to the normal fining action
of gelatin and it is not considered to be a trade secret! Thus the advantage of superior
hydrogen bonding reactivity of gelatin protein, as well as the apparently ideal pI of
gelatin protein and additionally, the unusual induced insolubility of gelatin protein, is
used and the result is a vastly superior rate of settling. Overnight settling and a compact
sediment is said to outweigh completely the higher cost of Superfine gelatin. The price
differential between 275g and 100g Bloom Strength gelatin would be 27 c/g and a
usage rate of 4 g/hl would therefore equate to an increased cost of some 1.08 c/hl!
TABLE 1.
The range of quantities of individual types of gelatin which achieve optimum fining.
Gelatin Type - Bloom Strength. Optimum usage rate.
A-267 90-100 g/hl
A-210 80-90 g/hl
A-195 80 g/hl

8. A-141 50-70 g/hl
A-120 40-60 g/hl
A-100 30-60 g/hl
A-80 30-90 g/hl
A-60 25-100 g/hl
From: Wucherpfennig, K., Ph. Possmann, Kettern, W. and Scherpe, W.
TABLE 2.
Gelatin Fining Tests on 1982 Stein, using Type B gelatin at 3 g/hl.
Gelatin Bloom Str. g Control 100 125 150 175 200 225 250 275
Determination Bentonite used g/hl
Sediment % 20
40
60
80
3.2
4.4
5.4
6.2
4.2
5.4
6.4
7.4
4.4
5.3
6.5
7.3
4.4
5.4
6.4
7.4
4.6
5.5
6.5
7.5
4.8
5.2
6.6
7.4
4.6
5.4
6.7
7.5
4.7
5.3
6.5
7.4
4.6
5.6
8.8
7.6
Clarity
(%T @ 520 nm)
20
40
60
80
88
89
89
88
91
92
92
91
92
91
91
91
91
92
91
91
92
91
91
92
92
91
92
91
91
91
91
92
91
92
91
92
91
91
92
91
Protein Stability
O= Unstable
S= Stable
20
40
60
80
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
O
S
S
S
From: Bestbier, W.
In taking the liberty of introducing the advantages of high Bloom Strength gelatin in fining, it is
necessary to emphasize that, if one does not use a very dilute solution of gelatin, then one must
remember that, on cooling, the solution will gel. Hence it is of prime importance to ensure that
when warm gelatin solution is added, it is added at a point of very intense agitation such that the
small amount of gelatin is intimately mixed into a large bulk of beverage before any gelling can
occur. One point of application that can be recommended is into the suction of a centrifugal
transfer pump as depicted in Figure 4.

9. Figure 4. Techniques for gelatin addition under large scale conditions. (Troost 1980)
Liquid Gelatin Fining.
A disadvantage of gelatin fining is the difficulty of gelatin dissolution. It requires both heat and
time, and in addition, gelatin solutions gel on cooling, and further more, they should not be
stored for more than a few hours at a time because gelatin is an excellent nutrient for most forms

10. of microbiological life. Hence, in line with European dictate that lower Bloom strength is better
for fining, a number of manufacturers have produced a highly concentrated solution of non-gelling
hydrolyzed gelatin preserved with SO2 which is allowed in wine. This concept has a lot
of convenience advantages and has received support from the wine industry in New Zealand in
particular. Researchers at KWV were very interested in the concept and have agreed to the use of
previously unpublished results in Tables 3 to 5.
TABLE 3.
Influence of gelatin fining on the polyphenol content of a South African 1984 Riesling.
Fining Polyphenol Content
Control + 40 g/hl bentonite 225 ppm*
Liquifine 3 g/hl + 40 g/hl bentonite 215 ppm
Superfine 3 g/hl + 40 g/hl " 210 ppm
* Method of Slinkard and Singleton (1987)
From: Baumgarten, G. (1984)
TABLE 4.
The influence of gelatin fining on the filter-ability of 1984 Pinotage.
Fining Filtrate ml*
Control 13
Liquifine 2 g/hl 20
3 g/hl 21
4 g/hl 21
Superfine 2 g/hl 21
3 g/hl 21
4 g/hl 20
* ml clear supernatant wine filtering through Whatman No. 1 filter paper in 120 sec.
From: Baumgarten, G. (1984).
TABLE 5.
The influence of gelatin fining on the protein stability of a protein stable 1980 Cabernet.
Fining Protein Stability*
Control Stable
Liquifine 2 g/hl Unstable

11. 3 g/hl "
4 g/hl "
Superfine 2 g/hl Stable
3 g/hl "
4 g/hl "
* Bento test and heating to 85°C for 5 hours.
Table 3 shows that the high molecular weight gelatin "Superfine" removed slightly more
polyphenol from the Riesling than did the low molecular weight "Liquifine". However, both
gelatins removed significant amounts of polyphenol.
Table 4 indicated that the gelatin molecular weight did not affect the filter-ability of the wine
after settling.
Table 5 showed that without adequate precautions by way of bentonite usage, the convenience of
using low molecular weight hydrolyzed gelatin, "Liquifine", can be offset by inducing protein
instability into the wine.
The use of finings at the pressing stage has not received much acceptance, largely it is said,
because the vintner feels he should see what the grapes are providing before he modifies this gift
of God in any way. However, some vintners in Australia have reported greatly increased yields
due to the formation of very compact sediment, by the use of Liquifine hydrolyzed gelatin in the
pre-fermentation stage of wine making. The addition of gelatin to cold grapes would generally
lead to waste due to gelling of the solution and it is here that Liquifine has an undisputed
advantage over gelatin, as a fining agent.
Conclusions.
1. In contrast to the European findings with Type A gelatins, that low Bloom strength
gelatin has optimum performance characteristics, it has been shown with South African
wines and Type B gelatins, that Bloom strength has no influence on fining performance.
2. When it is realised that high Bloom strength Type A gelatins have a pI close to 9,
whereas low Bloom strength Type A gelatins have a pI close to 6 and Type B gelatins
have pI close to 5, it appears probable that the superior fining action of low Bloom
strength Type A gelatins when compared to high Bloom strength Type A gelatins, is
more a function of pI than of Bloom strength, and as has been found with beer, the closer
the beverage pH to the pI of the fining agent, the better is the fining performance.
3. The use of hydrolyzed gelatin as a fining agent has convenience advantages but has been
shown possibly to lead to protein instability.
4. The use of high (250-270) Bloom strength (250-270) Type B gelatine for wine fining has
been reported to reduce greatly the settling time required for the fining of South African
wines.

12. Acknowledgments.
The author wishes to thank Davis Gelatin Industries (Pty) Ltd. and KWV (Suider-Paarl) for
permission to use previously unpublished data.
References.
Baumgarten, G. 1984. The use of Liquifine Gelatine as a substitute for Gelatine powder in wine
preparation. (Private communication.)
Bestbier, W. 1983. Ondersoek na die brei-effekt van gelastien met verskillende Bloom-getalle.
Die Wynboer 621, 61-62.
Ringland, C. & Eschenbruch, R. 1983. Gelatine for juice and wine fining. Food Technology in
New Zealand. August 1983.
Slinkard, K & Singleton, V.L. 1977. Total phenol analysis. Am. J. Enol. Vitic. 28. 49-58.
Troost, G. 1980. Technologie des weines. Verlag Eugen Ulmer, Stuttgart, Germany.
Vickers, J. & Ballard, G. 1966. Fining in perspective. Brewers Guild Journal. June 1966.
Vickers, J. & Bracher, C. 1961. Isinglass & Finings. Brewers Guild Journal. June 1961.
Wucherpfennig, K., Ph. Possmann, Kettern, W. & Scherpe, W. The effect of gelatine type on
fining in white wines. Wein und Rebe, Wissenschaft, Forschung, Praxis. 55, 92-937.