We just had another update about what Sandy Paetz is doing at the
MSU Viticulture & Winemaking School - “Pre-Bottling
Adjustments - Racking / Microfiltration”
This program was brought to our attention a few years ago when
a MSU student, Bernard Call, who is taking this course, purchased some
grapes at our farm and was carefully measuring the brix of the grapes
with a refractometer. The following year he returned to our farm after
being in the program for one year and he was very enthusiastic, interesting
and knowledgeable about the course.
Sandy Paetz, one of our past Sales Stand Associates, had also
enrolled in the MSU program. When the two of them found out
that they both were taking the courses, the conversations became very
stimulating and they agreed to forward some of their program notes to
us for our newsletter.
We have some inside stories of what Bernard and Sandy are doing
at MSU.
HRT 435L January 28, 2004 Michigan State University
“Pre-Bottling Adjustments - Racking / Microfiltration”
W.C. PAETZ
Abstract:
During our lab exercise we tasted the wines that we had measured
last week to discern what additions or amelioration might be required
to enhance their organoleptic properties. An examination of
our results from last week was used as a basis for understanding the
flavor components and wine stability. As we approached the lab our intention
was to rack the wines to remove sediment. Decisions were made regarding
amenable factors, which required action. Each wine has certain features
which foster conclusions regarding whether or not a certain wine style
is suitable and possible or not.
INTRODUCTION:
Bottling is the culmination of years of viticulture and enology
activity. Several important issues must be considered prior
to this final act. The final presentation of the wine may include a
program of bottle aging, however the ability to correct or enhance a
wine, is for all intense and purposes terminated when the wine is bottled.
Clarity, filtration, fining, stabilization, aging and possible blending
of the wine all must be considered prior to bottling. These post fermentation
decisions are crucial to the success of the wine maker and must never
be left up to chance.
In an article by Andrew Wood, from Divine Magazine(1.)
The story was told of a vintage of a particular wine, McGuigan Genus
4 Old Vine Hunter Valley Shiraz. This wine had been judged in several
blind tastings in Melbourne, Sydney and Canberra as one of the top wines
in the competitions. As a result of these evaluations the magazine published
a strong recommendation. Many of their readers rushed out to purchase
cases of this special wine as soon as it was released commercially.
Many consumers and judges complained when the wine did not begin to
live up to the reputation the magazine and judges had conferred upon
it. When the wine maker was confronted, He offered several explanations
including barrel samples are not really the same and that is what had
been judged, he went on to say that the earlier wine did not suffer
from bottle shock and that given time the wine would live up to all
of the accolades it had received. Eager to address the concerns of all,
the magazine directed an analysis of the wines. They actually had some
of the original bottles that had been submitted for the contest and
purchased others for comparison. Ultimately they concluded that there
was a difference in the constituents in the wine. The wine maker admitted
that due to marketing pressure they had released the wine too early.
Because of the differences in color and palate weight the bottles were
analyzed. The tests found significant differences between them. The
first bottling contained over 2 g/l of residual sugar, while the second
bottling had virtually no residual sugar. The first bottling was ½
percent higher in alcohol than the second. In other words the first
wine was stronger and slightly sweeter, the wine commercially available
carries the gold medal stickers from the wine shows. Eventually the
wine maker said the wine had been bottled at different times from two
different batches. Although he argued that the wine’s properties
were almost identical, except for slight differences in sugar and alcohol,
he will be hard pressed to convince the buying public again to try his
award wining wines. Industry authorities did not find him culpable,
with out sounding cynical, I would suggest that the Michigan Grape and
Wine Counsel would not be so likely to protect one of their own from
this type of error. The real lesson here is for one to understand the
importance of integrity in wine making. Most enologists go to tremendous
effort to produce consistent results.
So what are the compelling elements of wine making that dictate
how a wine can be perfected. Included are several post fermentation
activities that assure that a wine’s character can be guaranteed
year after year. Included are elements such as pH.
According to Eutech Instruments, (2.) “pH
is a fundamental element of the wine making industry. PH strongly
influences wine properties such as color, oxidation, biological and
chemical stability.”
Lower pH values are known to improve the stability of wine, so wine
makers prefer a pH range of 3.0 to 3.5. There are many advantages to
low pH values in wine. Low pH inhibits bacteria, causes sugar fermentation
to progress more evenly and makes malolactic fermentation easier to
control. Low pH also has a direct influence on the hot stability of
wine. Low pH results in better visual qualities for both red wine and
white wine color intensity. When wine pH has high values, bacteria grow
rapidly and undesirable bacterial fermentation is more problematic.
Clarity is a desirable factor for all wines. A brilliant
crystal clear polished wine is sought after by all wine makers. According
to Lum Eisenman, (3.) “Practically all white and blush wines require
special clarification treatments. These wines need fining and tight
filtration before they attain adequate clarity.”
Racking a wine is the process of removing the wine from container
and leaving the sediment behind. This simple operation is repeated
several times by most wine makers on wines to promote the gradual clarity
without the use of harsh fining materials that might strip out color
or flavor from the wine.
Stability issues encompass several factors. These can all be
measured and must be known to be able to factually comment on the suitability
of a wine for bottling. The status of measures such as pH, free SO2,
residual sugar, acid level all contribute to a wines stability and predictable
longevity.
Materials and Methods
Titratable Acidity Reduction:
Equipment:
1.) Chart from last weeks experiments
2.) Yardstick to measure volume
3.) Wine thief
4.) Tasting glasses
5.) Scale
6.) Calcium Carbonate
7.) Plastic tray to weigh material
8.) Mixing devise on drill bit
Method:
1.) Measure volume of wine in each carboy
2.) Sample extraction wine thief
3.) Tasting to confirm acidity
4.) Calculate amount of Calcium Carbonate to reduce acid.
5.) Measure and scale C.C.
6.) Place in carboy
7.) Mix
Results
(Figure 1)
L Addition of
Cultivar Vol pH TA Cal. Car.
Carbonic Maceration Foch 96 2.95 9.6 128
Carbonic Maceration Foch 51 2.95 9.6 68
Delaware *A 3.02 7.6 *A
N.W. Vignoles 3.36 12.4 na
Sparkling Foch 56 2.91 12.4 na
Late Harvest Vignoles 102 3.12 14.9 137
Discussion
The ability to follow a consistent program and to keep accurate records
regarding what has been done and when it was completed with respect
to every wine you make will give you a library to follow regarding the
steps for wine making.
There are certain prescribed protocol elements that will direct a wine
maker. At all times an up to date document should be maintained regarding
every wine being made. It must include cultivar, dates, operations,
ingredients, temperature, brix readings, alcohol volume, T A, pH, free
SO2.
In addition to racking and fining the process of cold stabilization
to remove tartrate crystals may be completed prior to bottling especially
in whites. The use of pasteurization or high temperature for a very
short time will protect a wine and provide microbial-stability.
Compositional adjustment of acidity, sugar level, ethanol level, tannin
removal and sulfide/ mercaptan removal are other adjustments which should
be considered.
There are an infinite plethora of considerations regarding the Vinification
of an exceptional wine.
Conclusion
This study was not only worth while but extremely important.
The capacity to evaluate a wine with analytical tools revealing factual
data can lead you to make technologically accurate wines. The capacity
to taste a wine and be able to discern taste component dimensions requires
much more experience. The only valid rational conclusion is that wine
making is as much art as science.
Appendix
Refer to figure 1 in text.
References:
1.) A. Wood, Divine Magazine, Numbers 30 and 31. May 2003
2.) Measuring pH in Wine-Making :www.eutechinst.com/techtips/tech-tips42.htm
3.) L.Eisenman, Home Wine Makers Manual, Chapter 17
Http://home.att.net/~lumeisenman/chapt17.html
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