136 R. Marchal and P. Jeandet
as a dilute solution of gelatin; one must remember that, on cooling, the solution will
gel. Hence it is of prime importance to ensure that when a 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 beverages before any gelling can
occur. In fact, there is really no detectable difference in performance between the use
of HMW and LMW gelatins (Marchal et al. 1993). This applied to all parameters
tested, i.e. sediment volume, clarity of supernatant and protein stability. Hence, the
gelatin to use is often (essentially!) determined by economics (the lowest Bloom
strength gelatins commend the lowest price) and facility of use.
Remark 1: Gelatin solution gel is an excellent nutrient for most forms of micro-
biological life. Hence, a number of manufacturers produce a highly concentrated
solution of non-gelling hydrolyzed gelatin preserved with SO 2.
Remark2: The use of finings at the pressing stage has not received much accep-
tance, largely, it is said, because the vintner feels he should see what the grapes are
providing before he modifies it in any way. Also, addition of gelatin to cold grapes
would generally lead to waste due to gelling of the solution.
Remark3: Gelatin is primarily used to soften red wines but it is also used to
reduce the phenol level and brown color in white juices before fermentation. The
potential for overfining with gelatin is great. Kieselsol, a negatively charged silica
compound, is recommended for white wines. Kieselsol helps to moderate the effect
of gelatin on wine flavor, and it reduces the amount of gelatin needed and the volume
of lees produced. Kieselsol or tannins must be added to most white wines following
gelatin fining or the gelatin will remain suspended in solution.
5.1.3 Fining with Plant Proteins: A Solution for the Future
Bentonite treatments are very efficient for protein removal and can also reduce
browning. But this mineral fining agent is also responsible for loss of wine aromas,
a negative sensorial perception that is a serious problem in enology. The influence
of treatments with tannins complexed with gelatin on wine composition and sensory
perception have largely been reported in scientific studies. These have often focused
on the factors contributing to protein-polyphenolic interactions, which are respon-
sible for the expected flocculation and clarification. The incidence of the bovine
spongiform encephalopathy (“mad cow disease”) led to grave concerns about the
use of proteins derived from animal sources in the food supply, and winemakers are
encouraged to discontinue use of gelatins (especially bovine gelatin) and more gen-
erally animal proteins. In Europe, the concern of transmitting this disease to humans
led to a ban on the use of bovine plasma and blood cells, commonly but incorrectly
called blood albumin and glue (Regulation CE 2087/97. Council, 20 October 1997).
Some winemakers are also hesitant to usecaseins because of their bovine origin.
The problem is the same for isinglass because of its animal origin too. Given the
above, it was important to develop treatments that could replace gelatin and ben-
tonite finings. Since 1999, many investigations have been carried out with wheat
prolamins, commonly called gluten, as white musts and wines clarifying agents.