By: Gerald Dlubala

Quality winemaking requires quality ingredients. Nothing new, you think. No big revelation there, you say. You take great care of your vineyard, with constant attention to the vines, fruit structure and soil. Your timing is just right for pruning, harvesting and the winemaking process. Then, after meticulously planning and carrying out the harvest, crush and fermentation with precision instruments and experience, it’s time to put that product into the barrels for aging.

  Are you as meticulous with your barrels? Even though grape quality is the main attribute in producing quality wine, there’s no doubt that cooperage is an expensive component in wine production, always coming in near the top of the expenditure list. Wooden oak barrels are challenging to clean and sanitize because they are, by nature, part of a living organism that is porous and layered. Combine this with a small access point, and you have an environment that is susceptible to micro-organisms that cause spoilage, with Brettanomyces being the primary concern.

  Often labeled as a winemaker’s biggest sanitation headache, Brettanomyces is a type of yeast found in nearly every stage of the winemaking process, from the grape skins to the barrels. It can be challenging to control or eradicate because it grows into the barrel wood and becomes hidden. Brettanomyces seldom reveal themselves during the fermentation process but rather prefer to flourish during aging. Some winemakers claim that a low level of Brettanomyces can give wine desirable characteristics, but any more than that will ruin the whole batch.

  In-barrel wine spoilage and short barrel life are problems facing the wine industry. Under the best conditions, wine barrels require a routine maintenance regimen to control taste- and aroma-fouling bacteria in affected barrels and keep them from taking over new, unaffected barrels.

Steamericas: Blending Science With

Eco-friendly Process

  “Winemakers should clean and sanitize their barrels absolutely after every use,” said Yujin Yoo Anderson, General Manager of Steamericas. “By sanitizing with a dry steam process, you can simultaneously sanitize and hydrate them to prepare them for their next use. The same goes for breweries and distilleries when hydrating vats or foeders before filling them.”

  Anderson told The Grapevine Magazine that there are many reasons that a sanitation program using dry steam is preferable over the lesser effective traditional methods.

  “The eco-friendliness aspect is always a priority,” said Anderson. “But ultimately, science has taught us that high heat effectively kills unwanted organisms. Dry steam, a gaseous state of boiled water above 212 degrees Fahrenheit, can penetrate barrel’s staves up to eight to nine millimeters depth and deliver high enough heat to remove Brettanomyces, which grows into the wood and is particularly hard to remove using other traditional cleaning methods. Additionally, there are quantifiable operational benefits to using dry steam sanitation for your barrels as well. Less water use means less time filling the barrels and less water and treatment costs. Dry steam uses as little as half a gallon of water per barrel in the entire sanitation process. Using dry steam is the quickest and most thorough way to sanitize a barrel, and it’s also a popular method to swell or rehydrate wooden barrels for not only wineries but also breweries and distilleries.”

  Anderson said that Steamericas’ Optima steamer uses only about a half-gallon of water to rehydrate and sanitize a barrel, and it accomplishes this in just a matter of minutes. The lack of wastewater production and the elimination of chemicals allow wineries to comply with the Clean Water Act.

  “The biggest challenge of using dry steam for your sanitation process is the upfront investment along with having enough power source,” said Anderson. “We typically recommend an 18kW steamer or higher for winery applications, requiring a three-phase power with preferably 480V. Wineries with 208-230V will need much more amperage. This type of investment may not make sense for a micro-winery with lower production rates and no bottling line. But to help offset the cost, a dry steamer with the proper accessories can serve as a winery and vineyard pressure washer without the wastewater runoff to clean equipment, fermentation tanks, floors and facilities, and whatever else needs a thorough cleaning.”

  Steamericas’ Optima steamer can be used as a stand-alone cleaning station to sanitize two barrels simultaneously. For more extensive facilities, the Optima can be paired with an automatic barrel washer line and loading system to clean and sanitize four barrels at a time. Maintenance largely depends on the facility’s water quality. Softened water is a must, meaning water treatment may be necessary for some instances. Steamericas sells and services their equipment through local distributors, but the machines come with display screens for real-time communication, so remote service is available if needed.

The Hot Water Treatment

  Hot water treatments using water heated to 85 degrees Celsius for at least 20 minutes have proven to effectively clean oak barrels and remove the acetic acid bacteria, Brettanomyces and yeast from the wood surface down to a depth of five to nine millimeters. The disadvantage of using hot water exclusively is the amount of time spent filling the barrels, the amount of water used and the resulting amount of wastewater produced.

Specialty Chemicals Can Harbor Hidden Expense

  Some sanitation methods for barrels require the use of specialty chemicals. One of the most popular chemicals for barrel sanitation is a Sodium Bisulfite solution mixed with a specific recommended amount of citric acid solution. It’s added to a barrel with water, sealed tightly, and then agitated, so the solution comes in contact with all interior surfaces. Next, the barrel is drained, thoroughly rinsed, filled with fresh, clean water and left to soak overnight. Several more rinses are needed before the barrels are ready for use, so the time and labor required for this method may be a deterrent as a standard sanitation method.

Aggressive Sanitation Methods Include Barrel Deconstruction

  Dry ice blasting and shaving of the inner surface area of the barrel can be effective but require at least partial deconstruction of the barrel, resulting in a time-consuming, expensive process. These aggressive processes also strip the barrel of any oak flavors and other qualities built up from prior use. As a result, the barrel becomes neutralized and no longer imparts flavor to the wine. Some winemakers use neutral oak barrels intentionally, depending on the winemaker’s goals. Still, continued use of these more aggressive sanitation methods naturally decreases the number of times a barrel can be sanitized.

Bubble-tech gmbh: High Power Ultrasound Sanitization Retains Barrel History and Integrity

  “The location of viable micro-organism cells within any barrel environment determines their chances of survival,” said Darren Bates of Bubble-tech gmbh. “Populations located within the arc of the barrel between the head stave and bilge have the greatest opportunity to survive and proliferate. Our studies show that applying high pressure or hot water sprays to the interior of barrels does not completely inactivate Brettanomyces cells. Methods like power washing, scraping and blasting destroy the toasted oak aroma compounds formed and retained in the toasted layer of a barrel. When using High Powered Ultrasound, a sonotrode gets inserted into the barrel with a small amount of heated water. The barrels are cleaned and disinfected in five to 13 minutes with no need for additional chemical rinses and using minimal energy consumption. HPU has also shown to better retain the organoleptic properties that are present over other cleaning and sanitization methods.”

  Bubble-tech gmbh specializes in using ultrasonic technology in industrial processes for beverage industries, including cleaning, sanitation, extraction and defoaming methods. Bates has extensive experience providing industrial ultrasonic technology and solutions for the wine industry, successfully cleaning and sanitizing oak barrels ranging from one through seven years of age.

  “In terms of how long we can extend the life of a barrel, on the conservative side, I would say two years as a minimum, but realistically it could go up to four years with an HPU cleaning frequency of one-to-two-year intervals. The HPU sanitation procedure has been successful in eliminating tartrates and reducing and removing viable cells of Brettanomyces while preserving the toasted oak qualities that winemakers desire in their red wines.”

  The advantages of using a clean technology like HPU for barrel sanitation include consistent and repeatable results with no chemical residue that reduces sulfur dioxide and taint-causing or hazardous chemicals while lowering labor, energy and barrel costs.

Not All Barrels Are Salvageable

  Dr. Bates told The Grapevine Magazine that infections of barrels with spoilage micro-organisms like Brettanomyces could have a marked influence on whether a winemaker can reuse a barrel. By using HPU, he hopes to extend barrel life by effectively removing tartrates, solid residues, micro-organisms, biofilms and taint compounds from surfaces and pores, and also removing anthocyanin pigments that Brettanomyces can break down.

  “Additionally,” said Anderson. “If a barrel wasn’t stored properly and the gaps between staves are beyond repair with swelling, or the labor and time spent to sanitize an affected barrel outweighs the cost of a new one, then it may be time to call it quits and make it into a cool souvenir.”

Choose Environmentally Friendly Options

  “Mainly, you want to consider the amount of water used, the resulting wastewater that will require treatment, and the potential side effects to humans and the environment of any chemicals used,” said Anderson. “While ozone is a powerful sanitizer, it can adversely affect humans in contact with it before it’s dissolved in water, causing nausea, headaches and respiratory issues. Mainstream methods of barrel sanitation tend to use a lot of water and chemicals that need treatment to lower the Biological Oxygen Demand before disposal.

  Water with a high BOD level means less available oxygen for aquatic organisms, potentially stressing and killing them. A typical Burgundy barrel holds 60 gallons, and a medium-sized winery could have thousands of these barrels in use. Imagine how much water and ecosystem you could save if you do not have to fill the barrels to capacity to sanitize them. It’s easy to see that the sanitation method that you choose as a winemaker is important.”

Final Notes

  When using any sanitation method, it’s crucial to include a barrel inspection. Even under optimal conditions, the best sanitation practices can produce side effects, ranging from the production of unwanted byproducts, some of which may be corrosive, to causing damage to already degrading rubber fittings, gaskets and some metals.

By: Alyssa Ochs

The cost of winery tanks tends to increase each year and can be heavily taxed in certain situations. So, it is wise to do your research and stay up-to-date about what types of tanks are available, effective and trending. Choosing a winery tank may seem straightforward enough, but there are a lot of factors and considerations to keep in mind before making a purchase.

  Various types and styles of tanks are available to wineries today based on size, material, and function. Fortunately, there are businesses specializing in tanks and tank-related products for the wine industry. These companies can offer a wealth of information about the best uses for this vital piece of equipment.

An Overview of Winery Tanks

  Tanks are used for many different purposes in a winery setting, including clarifying and removing tannins, proteins, and other solids. Tanks aid the prolonged aging of wine and assist with wine fermentation so that yeast grows properly and oxygen is controlled. Certain tanks can make wine smoother, fuller or fruitier in taste.

  A variety of materials are used for constructing wine tanks, including steel, wood and concrete. Porcelain, oak, clay/amphorae and plastic are other tank materials used by wineries.

Pros & Cons of Stainless-steel Tanks

  The type of tank chosen for your winery will depend on the purpose, budget and availability. For example, both general and multi-purpose tanks are used to make wine. Meanwhile, wineries use tanks for non-winemaking purposes, such as storing water for irrigation, collecting wastewater generated from winemaking, collecting chemicals for cleaning and having emergency water on hand for potential wildfires.

  Stainless steel tanks are cost-effective and last a long time. They come in different shapes and don’t add tannins or flavors, which is desirable for many wines. However, lately, there has been more international demand for stainless steel bought in bulk, making the costs higher than in the past.

  Scott Dapelo, the sales manager for Quality Stainless Tanks, told The Grapevine Magazine that enclosed, top fermentation and storage tanks are the most popular type that his company sells to wineries.

  “We make them in sizes from 500- to 50,000-gallon capacities,” Dapelo said. “The most common are the 2,000- and 6,500-gallon versions.”

  Based in Windsor, California, Quality Stainless Tanks provides custom-designed and ready-made tanks for wine, beer, spirits and special applications. The company hand-crafts its products in Northern California’s wine country and has the wine industry’s largest line of in-stock fermentation and storage tanks.

  “The sanitation aspects of stainless is a great advantage, as is its unparalleled longevity when compared to wood, plastic or concrete vessels,” Dapelo said.

  Julien Roussel from Algor, a stainless steel tank producer in Italy, told The Grapevine Magazine that his company’s most popular models are the FVPP and FCPT. These are pre-configured variable capacity tanks that come standard with welded legs, a sample valve, drain and racking ports and a complete floating lid kit.

  “FVPP tanks have flat bottoms with sump and accommodate volumes of 230 to 1,500 liters, or 60 to 396 gallons,” Roussel said. “FCPT tanks come with dish bottoms and accommodate volumes of 2,000 to16,000 liters or 528 to 4,226 gallons. Additionally, FCPT vessels come standard with a man-way door, 360-degree cooling jacket, thermometer and pulley arm. These versatile lines offer aseptic environments and can be used for vinification and storage. Moreover, our customers value the fact that all the accessories are manufactured in-house for seamless integration and consistent quality.”

  Roussel said Algor uses certified European AISI 304 and AISI 316 grade stainless steel alloys for its tanks. Both tanks offer high corrosion resistance and ease of cleaning, resulting in negligible product contamination.

  “The 304 is perfect for most applications and budget-friendly,” Roussel said. “The 316 can be worth the expense if you need to have superior corrosion resistance, such as if the tanks live outside and in the proximity of the ocean or if you produce wine vinegar. Our customers also opt for 316 when producing some specific wines such as whites from the Burgundy and the Chablis regions in France.”

Pros & Cons of Other Types of Tanks

  Wood tanks intentionally change the flavor and texture of wine. They are usually cylindrical and often used for decades; however, they offer the best sensory changes within the first two to three years of use. Wood tanks keep the fermentation at a warmer temperature, making it necessary to monitor that temperature closely and requiring more labor hours.

  Meanwhile, concrete tanks are porous and let some oxygen in during fermentation. Concrete offers more gradual fermentation and a more authentic representation of the wine without adding oak. However, concrete tanks can be challenging because of sanitation difficulties and cracking due to temperature changes.

  Amphorae is a nostalgic and historically used tank material that offers a natural approach to winemaking. These types of tanks come in various sizes but are not readily available and are more labor-intensive to use than the other options.

  Plastic tanks started being more widely used for wine in the 1980s and are still cost-efficient today. They can help wineries maximize their floor space and allow oxygen to permeate through the tank walls because of the polymer construction. There have been concerns about the quality of wine produced in plastic tanks, the wine’s lack of character, and the plastic odors left behind in wine from the tanks. Yet the stigma of plastic tanks has been fading away with the emergence of higher quality polyethylene tanks that defy all of these concerns and are safe for food and beverage purposes.

Other Wine Tank Considerations

  Cost is always a huge consideration when choosing wine tanks. Stainless steel tanks are often produced locally, making them easier to find and eliminating high shipping costs. Also, stainless-steel tanks tend to last considerably longer than oak and can save a winery money over time. Variable-capacity tanks commonly run between $500 and $5,000, based on size and features. But don’t forget about the costs of tank accessories and ongoing maintenance, so they don’t exceed the equipment budget for the year.

  Another consideration is how to keep tanks and their contents safe and protected in case of an emergency or natural disaster. Onguard Seismic Systems is a New Zealand-based company that provides patented seismic systems for liquid storage tanks that protect the tank, its contents, the people and the environment from earthquakes.

  “Losses suffered from earthquakes in global wine regions are numerous and include loss of product, loss of market share, insurance deductibles and compromised infrastructure,” Will Lomax, Onguard’s founder and managing director, told The Grapevine Magazine. “These losses can be avoided with the use of the Onguard seismic system. Unlike most incumbent anchoring methods seen in the U.S., Onguard’s energy-dissipating anchors also meet the U.S. building code’s seismic requirements for the design and construction of liquid storage tanks. The Onguard system can be installed on new tanks or retrofitted to existing tanks to improve seismic performance and resilience.”

  Lomax explained that winery tanks are generally either mounted onto elevated stands or placed directly onto a concrete slab or elevated pedestal. He said that tanks on stands require a full engineering design of the stand and the tank, which often gets overlooked.

  “Optimum seismic performance of tanks on stands is achieved by detaching the tank from the stand and installing the Onguard anchors between the two, rather than at the feet,” Lomax said. “Tanks mounted onto concrete are a simpler structural system, as loads are transferred directly from the tank to the concrete. In recent years, some owners in the U.S have elected to mount the tank onto a stainless steel ‘skirt’ which is then infilled with a concrete slurry after the tank has been placed on the concrete slab. This method is very common in New Zealand and results in a very clean and tidy facility, with no projections for hoses to catch on and easy wash-down.”

  While some tank styles were once commonly used for winemaking, they are becoming less common now in modern times. For instance, concrete has been a less common material for wine tanks in recent decades due to safety concerns and the popularity of stainless-steel tanks. Yet more recently, concrete has become much safer to use and comes in egg shapes and square shapes to increase the surface area contact between the wine and yeast. Clay/amphorae tanks are rarely used today but are a historical relic and throwback to old times for wineries looking to tap into their customer’s sense of nostalgia.

  “Historically, it was common to leave tanks unanchored or poorly anchored,” Lomax said. “Thankfully, things have changed, and more attention is now paid to improving seismic performance. Unanchored or poorly anchored tanks should be assessed and retrofitted. The investment is well worthwhile given the potential for significant losses and can also lead to preferential insurance terms.”

Choosing the Ideal Tanks for Your Winery

  Stainless steel is timeless and long-lasting, so it is the material of choice for many wineries––at least at the start. Some wineries also prefer oak, but they need to be prepared for extra maintenance hours for cleaning, curing, topping off, emptying, and doing sulfur treatments.

  Lomax from Onguard Seismic Systems said that the structural design of tanks is a complex exercise and should only be undertaken by engineers who have the knowledge and experience to provide functional and compliant designs.

  “The tank, anchorage and foundation should be designed as one integrated system and should comply with the seismic requirements of the current building code,” Lomax said. “The code mandates ductility in the anchorage system and energy dissipation through the permanent stretching of the anchors in a seismic event. This is often overlooked, for example, when tanks are simply welded to steel plates embedded into the concrete foundation, which almost guarantees significant losses in a design-level earthquake.”

  Roussel from Algor said that some wineries make the mistake of believing that more expensive is always better. For example, there are two bottom configurations for Algor’s large tanks: dish bottom and slope bottom.

  “The dish bottom is rounded with a drain at the center and lowest point of the dome,” Roussel said. “Slope bottom vessels have a flat bottom that slopes at a 5 % angle towards the drainage outlet. This design is recommended if you are frequently draining your tank. It is generally understood that dish bottom tanks are better for white wines and slope bottom vessels for red wines. However—and this may sound obvious—if budget is a concern and the goal is to make great wine, it is more important to focus on the quality of the grape than going over your budget to get all the possible bells and whistles.”

  Meanwhile, Dapelo from Quality Stainless Tanks told The Grapevine Magazine that a common mistake wineries make is buying cheap, imported tanks that are less durable and impossible to get repairs and parts when needed. He said wineries should “deal with a local provider that has a history of reliable performance, offers custom designs and keeps their promise on when you’ll receive your tanks.”

By: Tom Payette, Winemaking Consultant  

A precise test for a winery to measure the free Sulfur Dioxide in juices, musts, wines and at bottling is critical.  Selecting the proper test can be challenging due to cost and expertise.  Make certain to investigate the options of the many available tests to determine which one gives reliable results when working with your wines.  Having the precise number is imperative to take proper action if needed.  One of the tests, aeration oxidation, is discussed below.  It may seem antiquated but many well established cellars still adhere to this testing system.

  The equipment to run the aeration oxidation test is not inexpensive, the chemistry somewhat daunting, and the glass apparatus has the appearance of being overly fragile and complicated.  The units are expensive however, since we are seeking to measure a chemical in parts per million. A tool to do just that is bound to be costly.  The mechanics and chemistry are not complicated.  Without drawing large chemical equations a summary follows:  Free SO2 is drawn off of a sample of wine after a shift in the pH brings the sample to a very low ph range allowing all the free SO2 to be released and measured.  Once in the gaseous state, the gas is pulled through a hydrogen peroxide reaction flask with an indictor in the flask’s solution.  The hydrogen peroxide (H2O2) reacts with the SO2 to form H2SO4 (a very low concentration sulfuric acid) and H2O (water).  This in turn lowers the ph of the Hydrogen Peroxide collection flask and then the lab technician can titrate this sample with a weak base.  The weak base is measured volumetrically to determine how much of the base it took to neutralize the acid sample and then mathematically use that to formulate the Sulfur Dioxide content of the wine being tested.

Tools and Chemicals

•   25% Phosphoric acid

•   30% Hydrogen Peroxide

•   0.01 Normal Sodium Hydroxide

•   0.01 Normal Potassium Acid Phthalate or Hydrochloric acid.

•   Aeration oxidation indicator dye

•   10 milliliter burette – class A volumetric

•   20 milliliter pipette – class A volumetric

•   25 milliliter delivery cup squeeze bottle set at 10 milliliters delivery –  approximate.

•   100 milliliter graduated cylinder

•   Burette stand and a burette clamp

•   Vacuum source (adjustable) – only a light vacuum source is needed.

•   Aeration oxidation apparatus

•   Distilled water

Mixing and Standardizing Chemicals

•   Purchase or pre-mix your sodium hydroxide to 0.01 Normal.

•   Standardize the 0.01 Normal Sodium Hydroxide against the 0.01 Normal Potassium Acid Phthalate or 0.01 HCL.  Do this daily before each day’s work with this unit to be certain your results will be accurate.  This is a critical part of this test because it must be exact!

•   Purchase or premix the 25% Phosphoric acid.  Pre-mixing may be done by adding 1 portion of 85% phosphoric acid to 2 portions of distilled water. Example:  333.33 milliliters phosphoric acid to 666.33 milliliters water to make one liter.  Transfer a portion of this mixture to the preset squeeze bottle, set at 10 milliliter delivery, so it is ready for use.

•   Purchase the dye indictor because making it is much too daunting.

•   Purchase 30% Hydrogen Peroxide and mix 3.0 milliliters into 97.0 milliliters of distilled water (this should be ample to cover very high free SO2’s).  Add about 2 drops of 0.01 Normal Sodium Hydroxide to this fresh stock mix to shift the pH slightly to the basic side.  This will help the indictor solution to give a vivid “seawater” green at the beginning of each test and after the titration is complete.  Do not use store purchased hydrogen peroxide from a local pharmacy.

Procedure

1.  Make sure your apparatus is clean, set up properly and in good working condition.   After cleaning, rinse all of the lab ware with distilled water to remove any minerals and residues.  Allow to dry.

2.  Make sure the chemicals are readily available and mixed to the proper concentrations.

3.  Fill the 10 ml volumetric burette with 0.01 N. NaOH and make sure all air bubbles are out of the stopcock and delivery tip area.  Inspect.

4.Standardize the 0.01 N NaOH if not already done above.  This is crucial for good measurement.

5.  Rinse the reaction flask with a small amount (5 milliliters) of the premixed 0.3% (or greater) hydrogen peroxide (H2O2).

6.  To the Hydrogen peroxide reaction flask add the amount of 0.3% H2O2 (approximately 10 mils) and 5-6 drops of dye indicator.

7.  Attach the reaction flask into the clamp holder and place the glass bubbler portion back into the reaction flask.

8.  Select a fresh representative sample of the wine to be tested that was already collected and placed in the lab.  Using the 20 milliliter volumetric pipette transfer exactly 20 milliliters of wine into the lower boiling flask.

9.  Be ready to place the wine sample boiling flask onto the remaining glassware to complete the set up.

10.      Add 10 milliliters of the 25% phosphoric acid to the wine sample in the lower boiling flask.  [Be careful with this phosphoric acid since it may splash onto you or into unwanted areas of the apparatus.  Perhaps hold it away from the Aeration-Oxidation set up and over a sink.

11.      Immediately place the rubber stopper onto the wine sample boiling flask making the assembly complete and a “closed system”.

12.      Now turn on the vacuum source to vacuum air through the complete set up.  You should see a “boiling” action in both the wine sample boiling flask and the reaction flask.  This should be vigorous but not so vigorous that effluent is being transferred from one reaction vessel to the next – only air should be moving through the tubing.

13.      Time the operation of the units vacuum for 10 minutes – note the reaction flask should have turned purple in color in the first minute – if any Free Sulfur Dioxide is present.  Continue to monitor the test during the timed 10 minute interval making adjustments to the vacuum source, if necessary.

14.      Turn off the vacuum source after the desired 10 minutes.

15.      Disconnect the reaction flask (the one that turned purple) – from the rest of the lab set up assembly.  This will be done by removing the bubbler assembly from the unit and rinsing off any remaining solution on the bubbler tip with a small amount of distilled water.

16.      Turn to your pre-prepared and standardized 0.01 Normal Sodium Hydroxide burette and record the amount of solution in that burette.

17.      Titrate the solution in the reaction flask from the bright purple it has become back to the seawater green it was before starting the test. 

      (Note: Make sure to capture this endpoint since overshooting it will result in an inaccurate calculation of the sulfur dioxide on the high side)

18.      After the seawater green has been achieved, record the number of milliliters in the burette and write this number down on a piece of paper or in the lab book.

19.      Subtract the number of milliliters used to titrate the solution in the reaction flask and record this number to be used in the calculation portion of the test.  Obtain the exact volume of NaOH, to the tenth, used to neutralize the reaction flask content.  Example: 2.3 mils.

Calculation:

  Here is the formula to calculate the free sulfur dioxide:

Free SO2    =    Milliliters of NaOH * Normality of NaOH * 32000

                                          20 milliliters of wine sample tested

The Knowns Above Are:

  The milliliters of sodium hydroxide used to titrate the reaction flask effluent from purple to green as calculated from the reading on the burette.

  The normality of the sodium hydroxide used above since it was standardized recently.

  The given 32000 number

  The sample size of 20 milliliters.

  From this formula we now have enough information to calculate the free sulfur dioxide in the sample of wine.  If the Normality of the Sodium hydroxide is exactly 0.01N one may see results as follows:

  Let’s assume 2.3 milliliters of Sodium hydroxide was used to titrate the reaction flask effluent back to the seawater green color.  So 2.3 times 0.01 times 32000 divided by twenty yields 36.8 parts per million free sulfur dioxide present in the sample tested.  Part per million is also equal to milligrams per liter.

Summary

  This test is really very simple once one gets over the intimidation of the unit and chemistry.  It is recommended to follow these directions in the lab for 8 to 10 test runs and then to run several dozen others to commit the process to memory.  After running this process approximately one hundred times – read this procedure over again and much of the process will become crystal clear.  When learning this test, try to find a time when few interruptions will be expected so focusing on the task at hand will be easy.

Other Helpful Tips

  Once the phosphoric acid is added to the wine sample – all of the free SO2 is released – it is important to capture all of this SO2 in the Hydrogen peroxide solution – hence the need for connecting the wine sample boiling flask as rapidly as possible to the complete set up.  Make sure the Pasteur pipette is positioned to extend to the bottom of the boiling flask, well below the liquids surface, for best results.

  Set your aeration oxidation unit up as the manufacture has intended for the unit to be assembled.

  While performing the test make sure there is not an exogenous source of Sulfur Dioxide in the area of the testing – such as weighing metabisulfite and creating a dust or pungent aroma.  This may throw off the test leading to false readings on the high side.

  Endpoint: Be sure to catch the end point during titration at exactly the precise time the color changes being sure to swirl the reaction flask during titration.

  Send samples to an outside lab for a free sulfur dioxide test to see if the results achieved “in house” are in range with the certified labs.  Once accuracy is achieved, one may wean themselves off the outside lab but periodically send a random sample to an outside lab to pick up on any discrepancies.

  Wine samples tested should be at or below 68 degrees F and preferably at a cool 55 degrees F cellar temperature.

  Wines abnormally high in volatile acidity and carbon dioxide may give false high reading with this test.

  Water system pressure tanks, with many rural water systems, may cause a fluctuation in the vacuum source while oscillating between the pressure switch settings.  Be ready to compensate for this in the lab, adjusting the vacuum if an aspirator is used.

  The author does not recommend using this set up for total SO2 because it is time consuming, hard on the apparatus’s rubber parts and gives the unit a burned dirty look.  For total SO2 the author recommends the Ripper Method, provided ascorbic acid has not been used in the wine or any components of the blend.   An outside lab may be best for this test in terms of total SO2 as many wines rarely reach very high total SO2’s with today’s winemaking.

Reminders:

•   Make sure all chemicals and reagents are standardized and strengths known.

•   Make sure only gases transfer in the hoses – not liquids.

•   Keep a watchful eye on the vacuum to ensure it is proper and even.

•   Be patient and have quiet time to learn this procedure.

•   Sulfur dioxide is important.  An accurate measurement of the free sulfur dioxide in your wine, in PPM, is critical to your winemaking choices.

Other Suggestions to Consider:

1.  Run several tests on the same wine to see if the number can be reproduced. (?)

2.  Have an outside lab run some tests on the same wine.  Are your numbers in line?

3.  If using sorbates in wine – make sure you have ample SO2 in them at bottling.

4.  Run this test, at a minimum, monthly and more so as adjustments are needed and toward bottling.

5.  Consult a winemaker to determine an appropriate storage free SO2 of your wine and the correct bottling measurement.

  Tom Payette, Winemaking Consultant, has over 30 years’ experience with winery start-ups and assisting wineries already established in the industry.