In order to dilute the O2 in a container headspace it has been shown that the gas space or head space needs to be purged with a volume of inert gas that is equal to the volume of the headspace, 4 to 5 times to reduce the Oxygen level to close to zero.  See Factory Mutual Insurance Co., FM Global Property Loss Prevention Data Sheets 7-59, September 1977, revised 2000.

Testing for Oxygen presence is not trivial.  A common response is for the winemaker to say, “Well my match went out, that’s proof of no Oxygen.”   But it is not.

In 1993 some Australian spelunkers studied the problem, and found that:

  • A Butane Flame extinguishes at 14.5% O2
  • Matches sputter out at 13% O2
  • Matches will not ignite below 10% O2

This is a wake-up call for some.  Gaseous O2 can be measured accurately with a probe that costs probably less than $300.

I include the following chart of Gas Cylinders and their Volumes below to make it easier to determine your gas needs.

This chart tells you how much gas is in each tank, and how much gas is released per a 100PSI pressure drop, for the various Tank sizes available:

Cylinder Contents at STP,  Starting with Cylinder at 3,000 PSI    
Cylinder height with Guard, inches Cu. Ft. of Gas in cylinder at start “Gallons” of Gas at Start “Gallons” of gas  released per 100 PSI Pressure Drop
60 330 2469 82.3
56 250 1870 62.3
48 122 913 30.4
36 80 599 20.0
27* 55 411 13.7
22* 40 299 10.0
18* 22 165 5.5
* No Guard
Note: “At STP”  means  “At Standard Temperature and Pressure”,                                                    (20 Degrees C, and 1 atmosphere).

 


By: Denise M. Gardner

By definition, (o)enology is the study of wine and winemaking (Robinson 2006).  The field of enology differs from that of viticulture, the science of grape growing, although the two are often intertwined in academic departments across the United States.

An (o)enologist is one that practices the field of (o)enology, and often understands the scientific principles associated with winemaking, including desirable characteristics associated with the grape itself.  Enologists tend to understand wine analysis and can make educated decisions during wine production based on the analytical description and, potentially, sensory description of a given wine.  Many enologists do not actually have a degree in “enology” per se, although enology degree programs exist throughout the world.  In fact, many industry enologists have a science degree in chemistry, microbiology, biology, food science or another related field.

I find myself often making the argument that an enologist is actually a food scientist that specializes in the production of wine.  While it may appear less glamorous in words, many enologists that have studied in the U.S. have Bachelors of Science degrees from institutions in which “enology” is embedded within the food science department.  While the art of crafting a quality wine is unique to the product, and can require years of adequate sensory training or experience, the equipment and production techniques associated with winemaking are also utilized in the commercial production of many food and beverage products.

 

What does an (o)enologist do?

Being an enologist does not necessarily indicate that that individual is also the winemaker.  In the book, “How to Launch Your Wine Career,” the authors (Thatch and D’Emilio 2009) explain the two arms associated with wine production in California: the winemaker and the enologist.  For a head winemaker position, one typically has to work up the ladder from assistant winemaker, and may find themselves in several assistant winemaker positions prior to holding a head winemaker position.  The enologist position develops through a different ladder within the winery: from a crush (or harvest) intern to a cellar worker to a lab assistant and finally a cellar master before reaching the enologist position.  Note that this development may not always be the case in smaller, commercial wineries.

In larger wineries, many enologists focus on working within a winery’s lab.  Their primary duties could range from conducting daily wine analysis and monitoring quality control parameters of all of the wines, to training additional employees (lab assistants, lab technicians, harvest interns) in running analysis, to assisting the winemaker with specific tasks (e.g., setting up blending trials, recording data on blending trials, field trials, or wine trials, and accomplishing cellar tasks).  In smaller wineries, the enologist will tend to wear several hats, and may also be associated as the head winemaker for the establishment.

Understanding analytical techniques associated with the quality control of wine production is an essential component of being an enologist.   Photo by: Denise M. Gardner

Is an enologist the same thing as a sommelier?

Enologists should not be confused with sommeliers, which the Oxford Companion to Wine defines as a “specialist wine waiter or wine steward.”  Sommeliers are typically employed by restaurants, distributors, or other retail entities to advise consumers on wine purchases at a specific establishment.  It is not uncommon for sommeliers to determine a wine list for a restaurant or to advertise food and wine pairings based on the restaurant’s menu and available wine selection.

Education in a sommelier certificate program focuses on introductory viticulture and winemaking knowledge; a broad overview of terms and basic production practices (i.e., how to make a white wine versus a red wine).  Their focus will feature global wine producing regions (e.g., regions within France like Bordeaux, Burgundy, the Loire, etc.), wine styles and the characteristics associated within specific regionally (terroir-driven) produced wines. Written knowledge is supplemented with educational tastings, and most sommelier and sommelier-like programs have a unique tasting method that is taught and practiced by all pupils.  Additionally, some sommelier programs feature education on the various types of spirits produced internationally and the sensory evaluation thereof.  Sommeliers understand how to interpret wine regions and what to expect stylistically from a wine that is presented to them.  Despite the depth of knowledge in these areas, sommelier training does not focus on actual production techniques.  A sommelier is not trained in a wine processing facility, nor taught the scientific component to winemaking, and their approach to wine tasting often differs from those in production.  I have often found that sommelier’s evaluation of a wine can supplement that of the winemaker in a positive way, and emphasizes how varied sensory perceptions of wine truly are based on one’s training and experience.

 

There are several organizations that train sommeliers.  The most famous and prestigious organizations for sommelier credentials include the Court of Master Sommeliers and the Masters of Wine (MW) programs.  Certification typically requires participants to pass several exams, written and oral (i.e.,mock sommelier serving exams or blind wine tastings with adequate identification of each wine).  The Masters of Wine program also includes a written research paper on a select wine topic.

There is also a number of regional and local sommelier training and certificate programs, or wine education courses, available to interested parties.

Is it important for a winery to hire an enologist?

For a smaller, commercial winery (<10,000 cases), having an on-site enologist is beneficial for a winery, especially if the enologist is trained to make wine, run and interpret lab analysis, and adequately taste wines.  Essentially, their role takes can take the “guess work” out of winemaking.  An enologist’s skill and expertise can completely transform a winery’s brand and quality, especially if that individual is employed to accomplish two production tasks: enologist (i.e., lab analysis) and winemaker.  Additionally, a winemaker can also train to improve their skills in the lab to also act as the winery’s enologist.

How to become more enlightened in enology?

In Pennsylvania, there are a number of ways that one can improve their knowledge in enology.  First, it is best to identify what you want to do.

  • Are you interest in making or producing wine on the production floor?
  • Do you have an interest in science and lab analysis?
  • Or are you looking into a broader knowledge for making wine and food pairings?

For the first two points, if you are looking to switch careers or already employed by the wine industry, but think you need a more in-depth background in the scientific principles associated with wine production and/or analysis, a good starting point is Harrisburg Area Community College’s (HACC) online viticulture and enology Associate’s Degree program: http://bit.ly/HACCVandE

Additionally, Penn State Extension offers several workshops, short courses, webinars, and educational events that are designed for the commercial wine industry: http://extension.psu.edu/food/enology

Sometimes, it is beneficial to enroll in broader food production short courses to enhance one’s baseline knowledge.  Such short courses include like:

Additionally, many other Extension programs feature wine- and grape growing-specific workshops tailored towards to the commercial wine industry.

How to broaden your wine knowledge

However, if you found yourself wanting a broader background in understanding wine regions, wine styles, and wine (in general), without getting into winemaking, then you may want to look into a wine education course that follows a sommelier curriculum.  Several are featured in Pennsylvania, and offer a wide range of expertise levels:

 References

Robinson, J. 2006. The Oxford Companion to Wine. Oxford University Press, New York.

Thach, L. and B. D’Emilio. 2009. How to Launch Your Wine Career. The Wine Appreciation Guild, San Francisco.


The Gas Blanket Myth

“Oxidation of Wine can be significantly delayed by a “blanket” of inert gas.”

The Heavy Gas Myth

“Argon makes a better “blanket” since it is heavier than Nitrogen.”

Referring to the “Ideal Gas Law”,[1] there is no difference in the actions of different kinds of gas particles, and they all are at the same temperature and so are moving with the same energy.   The particles of Argon, being heavier than the two-atom Nitrogen particles, will move more slowly than the Nitrogen particle by a factor which is the square root of the ratio of the mass of Nitrogen gas particle to the mass of the Argon atom.   

Nitrogen is a diatomic gas, two atoms to a gas particle, where Argon is a mono-atomic gas, so the slower velocity of the Argon particle differs from the Nitrogen gas particle velocity by the square root of 28/40, which is  0.836, not a large velocity difference anyway.

But much more important is the theory of gas diffusion first put forth in 1833, developed by Thomas Graham   (Source of Graham’s Law) and the main phenomenon was described by him as follows:[2]

“…gases of different nature, when brought into contact, do not arrange themselves according to their density, the heaviest undermost, and the lighter uppermost, but they spontaneously diffuse, mutually and equally, through each other, and so remain in the intimate state of mixture for any length of time.”

This says that gases can never form a “blanket”, and Ends both the “Heavy Gas Myth”, and the “Gas Blanket Myth”.

 

************************************************

[1]Gas Law Details:

The physical “Law” for Gasses, called the “Ideal Gas Law” where Ideal refers to the Gas, not the Law, involves 4 very well-proven assumptions, so well-proven that they are nearly axioms.  The assumptions are:

  • Any gas is made up of particles. Atoms, Paired Atoms, aka Molecules, and lots of other molecules, and all the particles are in constant motion.
  • There are no attractions or repulsions between the particles; collisions between like and unlike particles are like billiard ball collisions.
  • There is a lot of space between the particles compared to the size of the particles themselves.
  • The speed of the particles increases with increasing Temperature.

As the particles, atoms or molecules of gas, collide with the walls of their container, they exert a force on the walls.  The average force per unit area is the Pressure of the gas.

The speed of the particles is related to the Temperature.  The greater the speed the greater the Temperature.  At any given temperature the velocities of the particles differ by the square root of their masses. Lighter molecules moving faster than heavier gas particles.

The walls of the container define the Volume of the gas.

Avogadro got things started by showing that the weight of a volume of a gas in 22.4 liters of space is equal to the atomic or molecular weight of the gas in grams. Some years later the number of atoms in the volume was computed to be 6.022 x 1023, and to honor Avogadro that number was named for him.

Boyle demonstrated that for a constant Temperature the product of the Pressure and the Volume is constant:                                                                                          PV = Constant, if T is constant

Charles showed that     V/T = Constant, if P is constant

Dalton put it together:    PV=NRT    where N is equal to the sum of all the gas particles in the Volume, or:                                                                                                      PV = RT x (N1+N2+N3. . . .)

 

[2]  Diffusion Processes, Thomas Graham Symposium, ed. J.N. Sherwood, A.V. Chadwick, W.M. Muir, F.L. Swinton, Gordon and Breach, London, 1971.


 

“In 2002, four Danish scientists began examining grocery receipts . . .

Altogether, they examined 3.5 million transactions from 98 super­ markets.  They found that wine drinkers didn’t shop the same way as beer drinkers. Wine drinkers were more likely to place olives, low-fat cheese, fruits and vegetables, low-fat meat, spices, and tea in their carts.

Beer drinkers, on the other hand, were more likely to reach for the chips, ketchup, margarine, sugar, ready-cooked meals, and soft drinks.

Perhaps the health of wine drinkers isn’t caused by wine so much as by the fact that wine drinkers like wine in the first place. The greatest predictor of health, these results suggest, doesn’t come down to this or that nutrient.

It comes down to what a person finds delicious.

Adapted from The Dorito Effect: The Surprising New Truth About Food and Flavor, by Mark Schatzker (published by Simon & Schuster in May)

Taken from The Atlantic (with some deletions), June 2015, page 17


Filtration can remove microbes that might spoil the wine. Some think it removes color.  A few years ago a California winery started putting “Unfined, Unfiltered” on its wine labels to imply superiority.
I toyed with the idea of putting “Uncentrifuged” on my labels, but thought better of it.

In St. Louis, in the 1990’s, I had an outstanding example of one of those unfiltered wines.  The reek of Brettanomyces from the glass poured from the $80, 375 mL bottle was intimidating at 3 feet.  Pad filtration might have captured the Brett microbes, but 0.45 micron membrane filtration would surely have.

Why do some winemakers eschew pad filtration?  I have seen the deposition of color on filter pads and I agree that it seems to be proof of color stripping.  But it is not.  The particles caught on the surface of fibrous filter pads are fairly large, and not the molecules that give the liquid wine its color.  These larger particles do have color molecules attached, but they are particles that will eventually settle out either on the closure or on the glass of the bottle.  The trial that few winemakers care to perform is the comparison between a filtered wine and an unfiltered wine after six months or a year in bottle.  If you doubt the premise, do the trial.

Pad filtration generally goes as far as removing 99.9% of the particles sized down to 1 micron.  0.45 micron membranes can assure removal of all particles greater than 0.45 microns, giving rise to the term “Sterile Bottling”.  Good work has been done showing that color stripping does not occur even with this stringent filtration technique:

From Abstracts from Presentations at the ASEV 63rd National Conference 20–21 June 2012, Portland, Oregon

Evaluating the Effects of Membrane Filtration on Sensory and Chemical Properties of Wine

1. Luke P. Bohanan, 2. David E. Block* and 3. Hildegarde Heymann

     Author Affiliations:
2.  Department of Viticulture and Enology, University of California, Davis, CA 95616
      (deblock@ucdavis.edu)

It is a long-held belief in the wine industry that membrane filtration, specifically sterile filtration below 0.45 μm, will strip a wine of aroma and color. For this reason, many winemakers avoid the use of sterile filters in wine production, which can cause uncertainty in microbial stability of the finished wine. There are currently no studies connecting sterile filtration to a significant sensory effect on finished wine. To assess this, two red wines, a Cabernet Sauvignon and a Merlot, and one aromatic white wine blend were filtered through 0.45 μm polyethersulfone (PES) and polyvinyl difluoride (PVDF) membrane filters. Sensory and chemical characteristics of these wines were compared to unfiltered control wines. Treatments were expanded with the Merlot and white wine blend to also examine the effects of a pad filter and a cartridge depth filter used as prefilters. Possible changes in dissolved oxygen were monitored during bottling, while tannin concentration and color were examined through the course of filtration. There were minor differences in tannin and color after pad filtration, but there was no significant variation during the course of the filtration. Descriptive sensory analyses were conducted for each wine immediately following filtration and on a regular basis for up to 24 weeks. While all three wines exhibited significant variation in sensory descriptors over time, a decrease in astringency between control and filtered Merlot wines was the only significant variation among treatments. Overall, there was no significant impact of sterile filtration on the sensory or chemical properties of the wines tested, regardless of the type of filter material used.
  • ©2012 by the American Society for Enology and Viticulture
Brett will wake up and grow in the bottle, which is why I strongly encourage the use of 0.45 micron membrane filters when bottling.
Dr. Tom Cottrell   7/6/2015

Formol Titration for YAN, using formaldehyde, can now be recommended with the availability of formaldehyde neutralizing pads or materials!

The things you need are Formaldehyde, and the neutralizers for it:

Source of Formaldehyde

Presque Isle Wine Cellars
Formaldehyde (Formaline), 37% liquid, Lab grade, 16 oz. bottle

Source for Formaldehyde Neutralizing Mats, pads or sheets

Newcomer Supply
FAN PAD Size: 8″ x 11″
Volume: 25 pads/pk Order No: ABFAN-811


New, Valid Procedure for Handling Headspaces in Wine Containers

Dr. Tom Cottrell

An important step forward for winemaking last year is the development of this theory and these protocols to safely maintain wine in partially filled wine tanks and other containers. The finding of numerous examples of spoiled wine in partially filled wine containers prompted me to work out and present a true understanding of the problem and its correction, for the first time in winemaking history.

Oxygen uptake by wine must be limited. Wine can generally absorb and dissolve approximately 6 ppm of Oxygen at a time, in the range of what is picked up during racking1. This Oxygen is consumed over 8 to 10 days2. Oxygen already in the headspace will move into the wine in a period of approximately 8 hours, drawing in some outside air which contains even more Oxygen. Oxygen from whatever source will do the dirty work of starting to spoil the wine, and the wine will be ready to accept more dissolved oxygen to continue the spoiling. Reaching approximately 80 ppm of total absorbed Oxygen will ruin most wines, whites faster than reds. Exclusion of ambient air is essential, and so is the removal of Oxygen from the headspace, either before or after moving the wine into the container.

The correct choice of inert gas to replace the Oxygen-containing air is, thanks to the “Ideal Gas Law” and its attendant axioms, simply the least expensive inert gas available, which is generally Nitrogen. CO2, Carbon Dioxide, does NOT qualify as an inert gas, AND it dissolves in wine, up to 107.2 mL/L3, causing the container to “inhale” some make-up ambient air which contains still more Oxygen. Since some CO2 in a wine can be good, CO2 may be added to the headspace to maintain a beneficial level. Argon has been espoused by many with the erroneous belief that the heavy gas could form a “blanket” to protect the wine from Oxygen.

In modern science, the first systematic experimental study of diffusion was performed by Thomas Graham4, the source of “Graham’s Law”. He studied diffusion in gases, and the main phenomenon was described by him in 1831. He stated that “…gases of different nature, when brought into contact, do not arrange themselves according to their density, the heaviest undermost, and the lighter uppermost, but they spontaneously diffuse, mutually and equally, through each other, and so remain in the intimate state of mixture for any length of time.” This disallows the concept of “blanketing”.

The standard (inadequate) procedure used by many wineries to flush the oxygen from the headspace, or non-wine volume of a tank, has been “5 minutes with the nitrogen hose running into the tank” or so. In fact, the correct flushing procedure was developed in 1977 by an insurance company5 serving a different industry, and requires flushing with an amount of gas equal to 5 times the volume of the headspace, to go from 21% Oxygen to 0.21% Oxygen.

The contents of gas cylinders are measured in cubic feet of gas. One cubic foot of gas is equal in volume to 7.48 gallons or 28.3 Liters. So, if the headspace is 1 cubic ft., 7.48 gallons, then 5 times 1 cubic foot, or 5 cubic feet (37.4 gallons or 141.5 Liters), of gas should be flushed through the system to reduce Oxygen levels below 1%

The manner with which many wine makers test for oxygen absence is to see if a match or butane lighter flame is extinguished when entering the tank atmosphere. While handy, the dousing of such a flame occurs while there is still 14.5% Oxygen in the volume, still way too high for wine, and a little too low for humans. This was examined and published by a Spelunker group in 19936.

Once the headspace has been “inerted” the regular practice has been to “seal” the container; a 5-gallon jug, or a 5,000 gallon tank, with an “air-lock”, a small plastic u-tube with liquid in it which will allow gas to pass through, either in or out when the pressure differential corresponds to 1.2 inches of water, or 0.04 psi (pounds per square inch). Changes in temperature large enough to push gas through such a “gas gate” at 0.05 psi, are as small as 1 degree C or 2 degrees F, which are often seen even in well-controlled cellars. In addition, beyond the control of winemakers, the normal barometric pressure changes can be greater than 0.15 psi or 4 inches of water. That makes the u-tube or “bubbler”, or what should be called an “air-passage”, versus an “air-lock”, allow air to move easily through.

With only an “air-passage”, falsely called an air-lock, in place, the wine in a half full container (of any size) will pick up about 2.8 ppm of oxygen per day. A container 90% full will only get about 0.28 ppm per day7. Since 80 ppm of oxygen pretty well kills a wine, there is some motivation to stop those oxygen inhalations. Stainless steel tanks and glass jugs can handle 3 psi positive pressure, so it is better to bung these things tightly if no further fermentation is possible. If a downward temperature change is expected, inert gas may be admitted to the container up to 1 to 2 psi positive pressure(8), and then the container may be bunged tightly. Plastic containers and VCT’s with flat floating heads can swell and contract with temperature and pressure changes, and are best kept tightly sealed at all times.

Further it is often a common practice tore-purge the headspace with nitrogen at regular intervals. Doing so can carry off all the CO2, leaving the wine may be oxidized, and having lost all its CO2 “its odor and taste become insipid” 8.

Dr. Tom Cottrell, 9/18/2014

 

Footnotes:

(1) Riberéau-Gayon, P., Glories, Y., Maujean, A. and Dubourdieu, D. (2000) Handbook of Enology, Vol. 2, The Chemistry of Wine Stabilization Treatments, John Wiley & Sons, New York, page 274 section 10.3.1

(2) IBID. page 360 section 13.3.3

(3) Riberéau-Gayon, P., Dubourdieu, D. Donéche, B. and Lonvard, A. (2000) Handbook of Enology, Vol. 1, The Microbiology of Wine and Vinifications, John Wiley & Sons, New York, page 216, section 9.6.1

(4) Sherwood, J.N., ed., A.V. Chadwick, W. M. Muir, F.L. Swinton, (1971) Diffusion Processes, Thomas Graham Symposium, Gordon and Breach, London.

(5) Factory Mutual Insurance Co., FM Global Property Loss Prevention Data Sheets 7-59, September 1977, revised 2000.

(6) Smith, G. K., Australian Caver No. 133 (1993) pp 20-23

(7) Cottrell, T.H.E., Presented at the 2014 Fruit and Vegetable Growers Conference, Wine Short Course, Lexington, KY, 2014.

(8) Riberéau-Gayon, P., Dubourdieu, D. Donéche, B. and Lonvard, A. (2000) Handbook of Enology, Vol. 1, The Microbiology of Wine and Vinifications, John Wiley & Sons, New York, page 216, section 9.6.1


A wine may be racked 3 or 4 times after removal from the fermentation Lees.

Extend the time between rackings roughly geometrically. The objective is to give smaller particles time to hit the bottom of the container when using 10 foot tall tanks

1) First Racking, off fermentation Lees.

Fining agents, preservatives, enzymes, anything else needed, may be added to the receiving tank during or immediately after any racking

2) 2nd Racking, no less than 2 weeks or more after First Settling Period

Measure pH, add appropriate SO2.

3) 3rd Racking after 2 months or more (or double First Settling Period)

Measure pH, add appropriate SO2.

4) 4th Racking after 4 months or more (or double Second Settling Period)

Measure pH, add appropriate SO2.

Make any final additions to receiving Tank.

5) Coarse filter when convenient, to a clean tank after measuring pH, and adding appropriate SO2 and anything else needed. (ensures complete mixing of final additions)

6) Fine filter to bottles when convenient (days, not weeks later.)

Settling Times: After First Racking: No less than 2 weeks

2nd Period: No less than 1 month

3rd Period: No less than 2 months

4th Period: approximately 4 months (depending on the brightness or clarity of the wine this period may be reduced or eliminated)

Final filtration to bottling, usually no less than 2 days.

Time for recommended treatment: No less than 7.5 months

If omitting or shortening the Fourth Period, the time required may be approximately 3.5 months, or more. This is frequently the “Norm”, if white grape wines are to be bottled in January or February.

Red grape wines are usually given the Fourth Period racking and then barreled.

”Fruit Forward” reds would go to bottle vs barrel, and often have a shortened Fourth Period.

258 Gallon Containers

When using 258 Gallon square tanks the settling schedule required is shown below:

(For 10-foot tall tanks double the settling times.)

Fining agents, preservatives, enzymes, anything else needed, may be added to the receiving tank during or immediately after any racking

1) First Racking, off fermentation Lees.

Fining agents, preservatives, enzymes, anything else needed, may be added during or immediately after any racking

2) 2nd Racking, after First Settling Period of no less than 1 week or more

Measure pH, add appropriate SO2.

3) 3rd Racking after 1 month or more (or double Second Settling Period)

Measure pH, add appropriate SO2.

4) 4th Racking after 2 months or more (or double Third Settling Period)

Measure pH, add appropriate SO2.

Make any final additions to receiving Tank.

5) Coarse filter when convenient, to a clean tank after measuring pH, and adding appropriate SO2 and anything else needed. (ensures complete mixing of final additions)

6) Fine filter to bottles when convenient (days, not weeks later.)

Settling Times:

After First Racking: No less than 1 week.

2nd Period: No less than 1/2 month

3rd Period: No less than 1 month

4th Period: approximately 2 months (depending on the brightness or clarity of the wine this period may be reduced or eliminated)

Final filtration to bottling, usually no less than 2 days.

Total Time for recommended treatment: No less than approximately 4 months

If omitting or shortening Fourth Period: Approximately 2 Months or more

Dr. T. Cottrell, 11/17/13


Nutritional Nitrogen levels in must are season and vineyard dependent. The level that is necessary for a good dependable fermentation (free of hydrogen sulfides or worse) is extremely yeast-dependent (and possibly author-dependent, as well). Depending upon the yeast, an acceptable nitrogen level lies somewhere between 250 and 450 (or more) mg/L of yeast-available-nitrogen (YAN).

The Formol titration in my WineDoc Lab Manual is a simplification of the procedure given in Bruce Zoecklein’s (et al) book, Wine Analysis and Production. Ammonium has been seen to be a fairly consistent 36% of the total YAN, but some variations do occur.

A Lallemand product, GO-Ferm, is designed to provide the start-up yeast cells with everything needed for the first third of the fermentation. It is to be added to the start-up bucket at 110oF, and then have the yeast added at 104oF. Not knowing the YAN numbers, you can safely add 2 pounds of DAP per thousand gallons, and 2 pounds of a supplement like Fermaid K. This particular combination will boost the YAN by 75 mg/L. The DAP and the Fermaid K should be added at about 16 to 15oBrix.

M-L additions: What and When?

The ‘What’ is easy. Use one of the direct addition types: MBR 31, 41, etc. If yeast contact is going to be minimal, or nutrient availability questionable, consider one of the M-L nutrients, such as “Opti ‘Malo” (a difficult pun).

‘When’ is also easy if you have chosen to use a yeast with M-L compatibility, as in low nitrogen requirements, and an M-L bacteria recommended for inoculation early in the fermentation. Dr. Sibylle Krieger-Weber of Lallemand convinced me that M-L inoculation early in the alcohol fermentation is good: either at the onset of alcoholic fermentation, or by 15oBrix. Sticking is not likely to occur if you use a yeast which has low N needs.

Let me know if you have questions in this area.

An important stylistic consideration is whether to maximize or minimize the buttery or diacetyl flavors. To maximize butteriness, hit the wine with SO2 as soon as the M-L fermentation is over. Conversely, to minimize the butteriness, wait until the yeast can metabolize the diacetyl away. Then hit the wine with SO2. This should be a relatively short period of risky exposure with low SO2 in the wine. To keep abreast of the flavor changes requires on-going awareness of the wine’s progress.

To help focus on that awareness, make a sign and put it on your door, or wall by the door: “Taste your wines Frequently!”

Latest research shows that “Co-inoculation” of white wines, a new idea, produces much higher floral character and fruitiness. This information comes from Dr. Sibylle Krieger-Weber also.

Brettanomyces

I supply this info since “Brett” has killed too many “Coulda been good” wines, and not just in Kentucky or the East!

Notes from a talk by Marty Bannister of Vinquiry Barrel Day, 3/16/00, at Wineries Unlimited Lancaster, PA

First identified circa 1900, there are a couple of species, and, now, some different strains. Brett is found in ciders and beers, worldwide.

The microbe can be found in orchards and vineyards, as well as wineries. It is found in all-new wineries, ergo; it came in with the fruit. It thrives in wineries: juice and air moisture are helpful to it.

Aromatic development follows this path:

Loss of fruitiness or varietal character follows a nasty path:

  • Plastic
  • Spicy
  • Leathery
  • Raw meat
  • Animal aromas
  • Fecal stuff

The plastic phase has been characterized as Band-Aid aromas.

The compounds involved in the aromas have been identified as 4-ethyl phenol and 4-ethyl quaiacol, in a ratio of about four to one of the phenol to quaiacol.

Threshold for aroma detection is about 400 ppb; it is ugly at 2000 ppb.

Aroma detection is very close to maximum preference.

100 ppb (0.1 ppm) separates the detection threshold from the defect threshold.

IT IS UNPREDICTABLE.

Brett growth activity does not often occur during primary yeast fermentation. Watch stuck wines carefully, since Brett grows well on low levels of residual sugar.

Dry wine may be defined as having less than 0.1% RS, BUT Brett can still grow at levels down to 0.02% RS.

Faster growth occurs at higher temperatures, and in the presence of Oxygen.

IN BARRELS:

Brett grows much more rapidly in barrels because Brett can eat the disaccharides formed in toasting the wood, and by splitting sugars off polyphenols. Red wines are the most common host.

CONTROL IS BY SO2. 0.8 ppm molecular SO2 kills Brett, and 0.5 to 0.6 seems to control it. When racking, leave bottoms if there is any reason to believe that Brett is around.

Growth habit:

Anaerobic > 4-ethyl phenol

Aerobic > acetic acid

It is important to re-adjust SO2 levels upwards. Use “the Cottrell Rule”.

SENSORY:

It is too late when you can smell it.

4-ethyl phenol can be measured, and that is a way to track Brett growth, BUT culturing should be done, too. In culturing with actidione, Brett forms moth-ball-like domes. Microscope searches can’t pick up Brett until the population is much too large. The typical look is ogive shape with bud scars.

Timing of sampling for Brett: mixing the barrel is best since Brett cells tend to drop to the bottom, otherwise take sample from as deep in the barrel as possible.

IN BOTTLES:

The bad aromas will intensify if live Brett cells are there!

OTHER CONTROLS:

DMDC/Velcorin controls Brett both in bottling and in barrels, but is generally too expensive and too hazardous for small wineries.

Barrel Sanitizing:

Clean it

Peroxycarb (Barrel Builders sells it.)

Ozone – as effective as Peroxycarb.

DRY STORAGE is good.

Crosby & Baker (MA) sell a Di-oxygen sterilant which also works well in Barrels (updated in 2002)

Note: Barrels cannot be sterilized. Barrels which give rise to Brett should be recycled (destroyed for wine use: made into planters, short skis, etc.

Mix it Up! Reduce bottle to bottle variations

Recently I have been surprised by some wild bottle-to-bottle variations.

I remembered an incident in the early nineties when a Nouveau wine bottled on November 13th had gradually increasing sugar from case 1 to case (about) 800.

My trusted and quite good lead cellarman assured me that he had thoroughly mixed the tank after sweetening. We guessed that the sugar had sunk, and never got distributed. Happily, the wine sold so fast that no one ever got a second case, and so, never came across the sugar differences.

Last year a local winery had the same inadequate distribution, but the addition was SO2. The last third of the cased wine will keep for 30 years easily! Consumers attempting to consume wine in that portion were not pleased.

A third incident with another nearby winery has prompted me to put this out for you to consider. Use of ‘Method A’ would avoid theses surprises. Racking close to bottling would also mix the batch well. Please do one or the other.

While it might sound boring for all the bottles in a release to be the same, customers do appreciate it.

Good mixing,

Tom