THE NATURE OF CORKS

Natural wine corks are  one of the most remarkable products of nature, and have played a critical role in the development of the premium modern wine world.The incredible properties of natural cork are primarily the result of cork's unique structure.

The bark of the cork oak tree is composed of tiny cells, each a 14-sided polyhedron, with the intercell space entirely filled with air.  There are approximately 40 million of these cells in a single cubic centimeter of cork bark. These cells give cork an unmatched ability to seal a wine bottle.  The cellular membranes are very flexible, making the cork both elastic and compressible.  These cell walls are impermeable to both liquids and gasses.  When released from pressure, the cork quickly recovers its original shape and volume.

This allows the cork to quickly conform to a bottle neck and seal it tightly against the primary enemy of fine wine--air.  Equally important, the natural cork maintains its flexibility for decades, making the seal long-lived, and making removal a simple process.  This tremendous longevity helps the cork protect fine wines for decades. 

The use of natural corks to seal wine bottles in the late 1600's and early 1700's encouraged winemakers to begin making richer, more powerful wines which would improve with age for decades, protected by natural corks.  Today the greatest wines in the world owe their style and fame to the use of corks to seal their  legendary (and costly) bottles.  The sound and feel of a natural cork being pulled  from the bottle signals the start of one of life's greatest pleasures  -- good friends, good food, and a great bottle of wine.

How can one material have so many unique properties?  The story begins in the forest. QUERCUS SUBER Cork is the bark of the cork oak tree (Quercus suber) which grows only in specific regions of the Western Mediterranean.  Attempts to grow this tree in other regions of the world with similar climates have not succeeded.

The cork oak requires a great deal of sunlight and the unusual combination of low rainfall and somewhat high humidity.  The quality and thickness of the bark of the cork oak  varies according to these growing conditions. The fact that corks are made from bark harvested from living trees has encouraged European environmentalists to encourage the use of cork over other, less natural alternatives.  Cork forests not only reduce the need for other polluting industries, they also help clean the air of the pollutants caused by these industries.

In fact, the cork forests are among the most regulated agriculture in the world--the forests are considered national treasures, and every step is carefully documented and regulated for the government.

The largest cork producing country is Portugal, followed by other Mediterranean countries such as Spain, Algeria, Italy, France, and Morocco.  Portugal produces nearly 50% of  the cork in the world, and the quality of its cork makes the country a leader in both quantity and quality.

THE CORK FOREST

Traditionally, cork forests have been wild--left to themselves and harvested when appropriate.  But recent investments in the industry have led to developments in the forest--including genetic selection of better trees. The resulting young trees are straighter than usual, and they are growing much quicker.  Dr. Tom Leydig is heading a research program determining the genetic variation of cork trees in the Mediterranean, so that more successful cross breeding can be done.

These new trees will get their first harvest after only fifteen years, rather than the usual 25 or more, and the straight trunks will allow more profitable harvests, as well. These new plantings have invigorated the cork industry--the average age of corks trees in Portugal is under 80 years old, while the tree will continue to produce for 200 years or more.

In Portugal, the revolution of 1974 had a significant impact on cork agriculture.  In the days after the revolution, the forests were broken up into small  parcels, and the result  was an uneconomic scale of farming.  It was simply not cost effective to bring in the farm equipment to control the cover crops which steal water and nutrients from the trees.  Each year, more forests are getting the attention and care that they need to produce great  cork--clean fields, healthy, carefully pruned trees.

THE HARVEST

Cork trees are harvested in the summer, every nine or ten years, after they reach 25 centimeters in diameter.  This harvesting process in very strictly regulated  by the government.

Harvesting a cork oak is very skilled labor.  Specialized axes are used to cut a ring around the tree at the top of the trunk, and then make one vertical slice down the trunk.  The axe is then used as a lever--it is inserted into the vertical cut and used to gently pry the cork off the tree.  The cork is peeled off in large panels and stacked in the orest. Obviously, great care is taken to avoid cutting into the cambium layer of the tree, which is still alive.

There is a significant difference between first harvest, or virgin, cork, and third harvest.  The virgin cork is rough, crumbly, and can only be used for cork board, insulation, gaskets, shoe soles, etc.  By the third harvest, the cork is beautiful, clear bark that will make great wine corks. After the cork is harvested, it is left to age for a period of months to allow the moisture content to stabilize. 

While the cork is aging in the forest, the cork producers come to the forest to inspect it, select their lots, and negotiate the price. 

CORK PRODUCTION

 All cork must be boiled before it is worked, to make it more pliable, and to fully expand the lenticels.  These cells are collapsed and wrinkled before boiling, but after boiling, the air in the cells expands, and creates a very tight, uniform cell structure that looks like a honeycomb.Some producers are now using a giant autoclave to boil the cork.  This has a number of advantages:  it is much quicker than boiling, it allows the moisture content to be very carefully controlled, so that the cork may be worked very soon after, and the gases from the autoclave can be analyzed for quality control studies.  

All good producers analyze their incoming cork for quality control purposes-- another example of how the cork industry is making an investment in quality. This investment is critical.  Demand for top quality cork by such organizations as the Cork Quality Council in California has encouraged a focus on quality.  In fact, top cork suppliers will only work with those companies investing in quality and new equipment and techniques.

When the cork has been boiled and dried to 20% moisture content, it is ready to work. It is graded by a worker who slices the cork to expose a clean surface.  Only the very best cork wood will become wine stoppers.  Such wood has very few defects, and is very consistent in color, texture, and density.

Following the grading process, the cork is sliced into narrow strips as wide as a wine cork is long, from which the corks will be punched.  The very best corks will be more than 50 millimeters long.  Each cork shows the growth rings of the tree running vertically through the cork.

The punching is very technical work.  While machines have been used, they are incapable of making the critical judgment calls that veteran punchers make so well.

After punching, the extra material will be used for champagne cork tops, gaskets, cork flooring--even insulation on NASA's space shuttle.

CORK WASHING

Once punched, the corks are ready for washing.

The latest washing systems use rolling cylinders to spin the corks in the liquid.  Huge tanks hold carefully monitored chemicals, which are pressure washed into the corks and then rinsed by a similar computer controlled process.

This provides better interaction between the corks and the washing liquids, better quality control, and more accurate testing.  This machinery is a major step forward. There are now a variety of washes--the popular chlorine wash, hydrogen peroxide, and sulfur dioxide wash as well.  Each is effective, as long as it is done properly.  

Much of the research concerning washes is done at CTCOR, the cork industry's technical laboratory outside Porto.  Here they study virtually every factor in cork production, and provide research and analysis to the 150 or so international members which sponsor it.  Some members of California's CQC are also members of CTCOR.

In addition to the new equipment and washing techniques, top producers are placing great emphasis on clean, professional facilities.  Moisture control following washing is a critical element in this effort. 

Today, top producers are using a combination of techniques to quickly dry the corks.  First a conveyor belt furnace dries off any surface moisture within minutes of the washing.  Then a temperature and humidity controlled room dehydrates them even further.

The moisture is lowered to 8%, where no mold can grow, and kept there for the rest of the life of the cork.  After the corks are washed and dried, they are visually graded yet again.  One procedure is via a team of very highly trained women, who inspect a large lot of corks and quickly judge them for visual quality.

The latest system involves optical sensors programmed by computer to select corks on the basis of a number of factors.  And while these are very fast and efficient, most cork producers will tell you that they still  prefer to use the women for a final check-- because they are more accurate than the  computers.

Corks are graded VISUALLY-they are graded by what they look like, not what they do.  Very expensive corks are beautiful and nearly perfect, but even less expensive corks will seal a bottle effectively.  One of the most complicated subjects in the cork industry is the concept of grading.  Because they are natural products, it is impossible to perfectly classify corks--some people may prefer one type, while others look for something else.  To eliminate some of the confusion surrounding cork grading, the Cork Quality Council has developed some basic visual grading standards for the California wine industry.  The new standards use specific and measurable visual criteria to describe each grade.

   
Once the corks are washed, dried, and graded, they are almost ready for use.  They receive a final coating  of paraffin and silicon.  This will help them seal the bottle and be removed easily.  

    QUALITY CONTROL

Because of its dominant position, the Portuguese cork industry has a huge impact on the cork industry as a whole.  In the last twenty years, the Portuguese cork industry has been in transition, making changes to improve both the quality and consistency of its corks from the trees in the forest to the finished product in the wine bottle.

Of course, many of these developments have been made possible by Portugal's entry into the European Community.   European companies are investing in the future of cork--an environmentally sound industry which adds to the quality of life in their community.

There are extensive quality control laboratories at cork  producers in Portugal, and they provide a great deal of data to the industry.  By comparing the results they get with the results members of the California-based Cork  Quality Council,transport problems can be easily identified.

    THE CQC'S ROLE IN QUALITY

The Cork Quality Council is an organization of seven cork suppliers who work together to improve the quality and  consistency of corks in America, while educating the wine industry to improve bottling  techniques and the proper use of those corks.

The CQC is currently involved in a series of research projects concerning cork coatings, bottling techniques, and     bottle variation.  In addition, they organize educational "round-table" seminars for the wine industry, and have     developed a infomational materials about corks. These are important, because there is more mis-information about corks than about any other factor in winemaking.

The members of the Cork Quality Council must track all incoming corks to mil spec standards.The organization has
provided the wine industry with a series of recommended bottling procedures to eliminate problems at the winery.  And the CQC has developed  new standardized visual grading classifications to help wineries understand corks better.   

The Cork Quality Council works with top wineries on these projects for two important reasons.  The first is to make sure that the final recommendations are applicable to the state of the industry today.  And second, these wineries have excellent quality control procedures, and can document their success.  

Since these cooperating  wineries have very few problems with their corks, they serve as an excellent example to any winery which is having trouble.  

The CQC is currently working with Dr. Ken Fugelsang of Fresno State on a series of studies to determine the best way to treat corks, and the best way to use them.  The research has already pointed to a number of new directions for wine and cork quality.

Recent research indicates that as wineries reduce the use of sulfur dioxide, they may run the risk of more wine spoilage.  

>>  Dr. Fugelsang has created moldy, musty aromas in wines without any contact with corks.  Low levels of hydrogen sulfide can interact with ethyl acetate to create compounds easily confused with cork taint.

    >>  Wines with lower amounts of sulfur dioxide, and wines with higher pH are much more likely to develop cork taint in the bottle.  One wine, with a pH of 3.15, and SO2 of 38 ppm, developed no identifiable cork taint, even when sealed with mold infested corks!

Dr. Fugelsang, is also working with a number of wineries and members of the CQC to develop a series of Quality Control Procedures which will help wineries understand the issues at stake.

    CORK TAINT

So called "cork taint."  is 2,4,6 Trichloroanisole, or TCA, and is often mis-identified and blamed for
any flaw in wine.  TCA smells like mildewed paper, and it is present in coffee, chocolate, raisins, beer, bottled water, and even soft drink cans.  It is present, in very small  percentages (1% more or less) in corks.  

TCA is created when molds metabolize trichlorophenols. Tricholorphelols are omnipresent, due to their role as disinfectants throughout the world.  The key to eliminating TCA is to limit the presence of mold.

The measures discussed above have made a huge impact on the incidence of TCA in corks, and all of the above industries are working to eliminate it entirely.  Ironically, because it has been found in both beer, with a crown cap, and bottled water, in a plastic container, the solution will be something that  improves ALL foods and beverages, not just wine corks.

There are currently a number of different research projects concerning TCA in progress, from bottling techniques to microbiology, to coating technologies, to pull strength tests and  leakage analysis.  

And while each of these indicates even more directions for research, they have all shown one thing: compared to the alternatives, corks continue to be the best choice for sealing bottles of wine.  Which is why the best wineries in the world will continue to use natural corks for their finest wines.

    COMMON MYTHS AND ERRORS

 >>  Occasionally, there is a news report of the demise of the cork forests of Europe.  This is simply not true. There is one small section of a single cork forest in Portugal which is being affected by industrial pollution nearby.  The effects of this pollution are limited to approximately ten percent of the trees in this one forest, or less than one percent of all cork trees in Portugal.  The pollution is being controlled to eliminate the problem.

Perhaps one source of this curious falsehood is a British wine magazine which printed a story concerned a nematode called "Primiaprilis Americensis"  (First of April in America) which was attacking the cork tree roots.  The humor was well intentioned, but some people may not have understood it!

    >>  Despite illustrations in the children' story Fernando the Bull, corks do not grow on trees like almonds or olives.  

    >>  Nor are the cork tree harmed or killed in order to harvest the cork.  The trees can live for hundreds of years, and will continue to produce cork for that period.

    >>  There is also an astonishing rumor that cork production is failing to keep up with the increasing demands of the wine industry.  In fact, wine consumption is down in every major country, and the demand for corks has shown an equivalent drop.

    >>  A recent American Society of Enology and Viticulture presentation noted that if cork bark is not boiled immediately after harvest with chlorine, it will rot in a matter of weeks.  This is obviously not true. Cork fishing floats continue to float for centuries, and corks have sealed the greatest wines in the world for decades.

    >>  The same ASEV presentation also noted that the cork SLABS were washed in chlorine.  In fact, only the punched corks themselves are ever washed.

    CORK REFERENCE MANUAL

    To improve the use of  corks by the wine industry, the Cork Quality Council has developed the following reference materials.

    These materials are intended to be used as guidelines, and there may will be reasons to adapt these procedures to the specific equipment and goals of the winery.

    Nevertheless, we strongly encourage wineries to use these guidelines as a foundation upon which to build a bottling and quality control manual.

     CORK WASHING STANDARDS

CTCOR, the Cork Technology Center of Portugal, has developed the following recommended  guidelines for the processing of corks.  While these are general guidelines, the CTCOR laboratory has spent considerable time researching these processes and analyzing the results.  

 The Cork Quality Council, recognizing CTCOR's leadership in this field, has provided these general guidelines as a part of our on-going educational efforts on  behalf of cork and the wine industry.  

    TRADITIONAL CHLORINE WASH

    1.  Begin with a tank (without dust) with an aqueous solution super saturated with calcium hypochlorite.  The end result should be a final bath with a maximum total  of 30 grams per liter of free chlorine. Submerse the corks in this bath, agitating them for approximately two minutes.

    2.  Allow the corks to remain at ambient temperature for a time not to exceed two hours.

    3.  Repeat steps 1 and 2 ONE or a maximum of TWO times.

    4.  Immerse the corks in a bath of clean water, agitating them for two minutes.

    5.  Submerse the corks in an aqueous solution of oxalic acid at 6 to 8 grams per liter, agitating them for a period of two minutes.
    6.  Immediately centrifuge the corks, and then dry them until the moisture level becomes stabilized at a humidity which should be between 6% and 8%.

    HYDROGEN PEROXIDE (H2O2) WASH

1.  Submerse the corks in an aqueous solution
containing 10% hydrogen peroxide and 3% (by volume) of commercial ammonia, agitating the corks for approximately five minutes.

    2.  After removing the corks from this bath, allow the corks to remain for thirty minutes at ambient temperature.

    3.  Immerse the corks in clean water for two minutes, agitating them.

    4.  Submerse the corks in a solution of 1% citric acid by weight, agitating them for approximately five minutes.

    5.  Immediately centrifuge the corks, and then dry them until the moisture level becomes stabilized at a humidity  which should be between 6% and 8%.

    POTASSIUM METABISULFITE (SO2) WASH

    1.  Submerse the corks in an aqueous solution of potassium metabisulfite (1% by weight) for approximately five minutes.

    2.  Immediately centrifuge the corks, and then dry them until the  moisture level becomes stabilized at a humidity which should be between 6% and 8%.

       SULFAMIC ACID WASH

    1.  Submerse the corks in an aqueous solution of sulfamic acid (2% by weight), agitating the mixture for approximately five minutes.

    2.  Allow the corks to remain at ambient temperature for 10 minutes after removing them from this bath.

    3.  Immerse the corks in clean water for two minutes, agitating them.

    4.  Immediately centrifuge the corks, and then dry them until the moisture level becomes  stabilized at a humidity which should be between 6% and 8%.

      CORK QUALITY COUNCIL VISUAL GRADING STANDARDS

 The seven members of the Cork Quality Council have developed standardized visual grading criteria for the corks they supply to the wine industry.  The CQC has developed these standardized visual grading criteria to provide a consistent terminology for the visual aspects of the corks sold in the United States.  

This follows years of confusion between different companies and  even different countries  concerning the terminology used for the  visual grading of corks.  The new visual grading standards will be used by all seven members of the Cork Quality Council, and are designed to be used by wineries to better understand the individual  lots of cork they purchase.

However, there are three key points which must be understood by those who use these new criteria to describe the visual aspects of the corks they purchase from the members of the CQC.

>>  Corks are a natural product.  As such, the visual aspect will vary from cork to cork and from lot to lot.  These new visual grades are designed to describe a range of corks of similar visual appearance.  Because of the natural variation between individual lots of cork, all corks of a single visual grade will not be identical in every characteristic.

    >>  The CQC visual grades describe the physical appearance of the cork, rather than the structural integrity of the cork.  While there is some correlation between the visual aspect of a cork and its structural integrity, there is no direct mathematical relationship between these two elements of cork quality.

    >>  Every defined lot of corks will inevitably contain a mixture of corks of more than one visual grade.

    >>  Because there will be some variation within a single visual grade of cork, the CQC strongly recommends the use of samples of appropriate size when evaluating lots of corks.  The CQC suggests the use of Mil Spec Standards to determine sample size for an individual lot of corks.

    CQC GRADE "A"

 These are corks with top quality visual appearance --excellent surfaces, with no major visual flaws and few small ones.  As such, there should be:

    >>  No holes or pores which exceed 2mm.
    >>  No cracks originating at the ends which exceed 11% of cork length.
    >>  No cracks in the body of the cork to exceed 18% of cork length.
    >>  All cracks must be tight and not open.
    >>  No horizontal cracks.
    >>  No worm holes, hardwood, belly spots, or greenwood.
    >>  Several narrow and shallow lenticels are acceptable if they are free of dust and particles.

    CQC GRADE "B"

These are corks of good visual appearance with no major visual flaws and with surface visual flaws of no depth or substance.  In these corks there should be:

    >>  No holes or pores which exceed 5mm.
    >>  No cracks originating at the ends which exceed 18% of cork length.
    >>  No cracks in the body of the cork to exceed 25% of cork length.
    >>  All cracks must be tight and not open.
    >>  Lenticels and horizontal cracks on body must not open up when the ends of the cork are bent.
    >>  No greenwood, no angled or deformed corks.
    >>  Very small chips and lateral worm activity in the middle of the body of the cork may be acceptable.
    >>  Lenticels at ends must not be wide or deep and should be free of dust and  particles CQC GRADE "C"

    These are corks of
    average visual appearance
    with one or more major
    visual flaws which will
    be of cosmetic nature
    only.  Thus they may be
    esthetically unappealing, but functional.  In these corks there should be:

    >>  No cracks, channels, hardwood, or belly spots which exceed 55% of cork length.
    >>  Lenticels and horizontal cracks on body may open up when the ends of the cork are bent.
    >>  Greenwood to 55% of  cork length is acceptable  unless severe depth or width.
    >>  Large chips are  acceptable
    >>  No worm activity from end to side which exceed 55% of cork length.
    >>  No dry years which exceed 55% of cork length.
    >>  There may be heavy, but not continuous,  porosity.

    CQC GRADE "D"

    These are corks of poor  visual appearance with major visual flaws which will not cause a malfunction in the  performance of the cork. In these corks there  should be:

    >>  No cracks, channels,  hardwood, or belly spots which exceed 75% of cork length.
    >>  Lenticels and horizontal cracks on body  may open up when the ends of the cork are bent.
    >>  Greenwood to 75% of cork length is acceptable, or less if of  severe depth or width.
    >>  Large chips are acceptable
    >>  No worm activity which exceeds 75% of cork length.
    >>  No dry years to exceed 75% of cork length.
    >>  There may be heavy, continuous, porosity.
    >>  There may be badly  stained corks.
    >>  There may be corks of incorrect size.

    CQC GRADE "E"

    These are corks which do not meet the standards for Grades A-D.

    CORK DEFECT DEFINITIONS

Belly Spot.--Surface depression - caused by the dense inner surface of the cork strip from which the cork is cut.

Channels.--A groove  running along the surface of the cork - caused by cutting corks too close together.

Chips.--Irregular pieces missing from the cork surface usually on or near the ends - caused by  processing damage due to dry or brittle cork wood or faulty corker jaws.

Cracks.--A crack or fissure in the surface of the cork - generally caused by the wood being too dry or brittle. This can cause chips during processing.

Dry Years.--Narrow woody growth rings - caused by a lack of rain during the growth year.

Greenwood.--Undulations in the surface of the cork - caused by moisture related conditions.

Hard Wood.--Hard rough areas on the surface of  the cork - caused by cutting the cork too close to the bark surface.

Lenticells.--The cell structure of the cork - it runs horizontally in cork closures.  Each  lenticell is a 14 sided polyhedron with the intercell space entirely filled with a gaseous mixture almost identical to air. 1 cubic centimeter of cork wood contains about 40 million individual cells.

Pores.--Holes or fissures or soft pith-like tubes/canals in the lenticell structure.

Porosity.--High density pore activity.

Worm Holes.--Holes in the cork caused by worms forming canals from their entrance in the cork to their exit from it.

                  
CORK QUALITY COUNCIL INCOMING QUALITY CONTROL FOR CORKS(REVISED APRIL 1993)

    I.    Sampling Plan:

Individual lots of corks should be sampled using U.S. Government Military Standard 105-D plan. From the sample taken, smaller sub-samples are randomly selected to undertake the following quality tests.

    II.   
    Acceptance/Rejection:

    Guidelines for acceptance and rejection to follow US, Government Military Standards 105-D Inspection Plan (reduced inspection), at the various acceptance levels as indicated per test below.

    III.  Test Procedures:

     A.  Sensory Test:

       1. Sniff Test: The number of corks to be tested will be in accordance with Mil Std 105-D:

       2. Six corks from each bale taken as per IIIA1, above will be immersed in a 500ml container of  neutral dry white wine for 24 hours, then checked organoleptically for changes in sensory character when compared to a control wine. If TCA  taint is suspected, an  immersion test will be made from six corks from every bale. Any bale with  TCA taint will be rejected.

     B.  Visual Quality:

Corks sampled, at a minimum,  will be in accordance with Mil Std
    105-D (reduced). Individual corks are classified into pre-           
determined categories depending on the physical            
qualities agreed on with the producer.

     C.  Moisture:

    Cork moisture will be tested on a sample size of 25% of the Mil Std 105-D (reduced) per lot. A Moisture Register Co. or Aqua-Boy cork moisture instrument will be used. Cork shipments should be received with a moisture level below 8% average, with a tolerance per AQL 4.0.

    If moisture level average is above 8% but below 10.5%, the following procedure may be followed:

       1. Corks are to be placed in a drying area which is physically separate from the storage area for accepted corks.

       2. When corks are resampled for reduced moisture levels, the cork moisture will be tested on a sample size of 25% of the Mil Std 105-D (reduced) per lot.  A Moisture Register Co. or Aqua-Boy cork moisture instrument will be used.  Moisture level must be below 7.5% average, with a tolerance per AQL 4.0.

       3. All sensory testing must be done again following procedure outlined in III.A before corks can be accepted into ongoing inventory of corks suitable for sale.
     
     D.  Dimensions:

    Cork dimensions will be checked on a sample size of 25% of the Mil Std 105-D (reduced) per lot using an electronic or dial caliper accurate to +/- 0.01mm.  Tolerance range per ISO 3863, and acceptance at Military Standards 105-D.

    Diameter: as specified (+/- 0.50 mm)   AQL = 1.5

    Length:   as specified (+/- 1.00 mm)   AQL = 4.0

     E.  Residual Oxidants:

    One cork from each bale taken as per paragraph IIIA1 above will be tested using a qualitative analysis involving the reaction of potassium iodide with residual oxidants in the presence of a starch indicator. A change in the test solution from clear to blue/violet color is a positive result:

Acceptance:
     
Traditional washed: per CTCOR

Peroxide washed: ZERO

Natural (Metabisulfite)   ZERO
                     

    IV.  A lot is defined as a particular wood quality, size and wash from an individual supplier in a single shipment.
     
V.  Permanent records of the quality control tests  for each lot will be kept for a period of at  least five years.

    OUTGOING QUALITY CONTROL FOR STILL WINE CORKS

    I.   Test Procedures:

     A.  Batch Quality:

The batch quality should match any samples presented to clients on which the order was based. Cork samples sent to a client should contain a minimum of 24 corks.

     B.   Cork Moisture:

    Randomly sampled corks from the prepared batch  are analyzed using the same procedure as Incoming Cork  QC. Prepared batches should have an average moisture range of 5% to 8%.

II.  An injection of at least 2 grams of sulfur dioxide should be added to each bag of corks for the control of micro-organisms.
        
III.  Permanent records of the quality control tests for each lot will be kept for a period of at least five years.

IV.   Every reasonable effort will be made to ensure the pristine character of the corks is preserved while in processing at members' facilities in this country.
    
      CORK QUALITY COUNCIL RECOMMENDED CORKING PRACTICES

    I.   Corker Jaw Type:

     A.  The 4 segment sliding jaw type cork compression system is recommended. Roller or iris type jaws tend to cause wrinkles in the cork which can cause leaking.

    II.  Corker Maintenance to Ensure:

     A.  Corking machines are maintained to manufacturers recommended  standards at all times.

     B.  Smooth action in compression stage.

     C.  No nicks or other damage to the jaw segments.

     D.  Good alignment and seal of bottle neck in centering bell.

     E.  Properly centered plunger.

     F.  Daily cleaning and sanitation of cork handling surfaces; i.e.  hopper, feed tube, orienter, and jaws.

    G.  A 24mm cork should not be compressed to less than 16mm.

    III. Cork Handling and Storage:

A.  Do not open plastic cork bags until immediately before loading corks into the loading machine. No bags containing corks should  be left open for any reason.

     B.  Corks recovered from the corking machine after the bottling is completed should be returned to the plastic bag or another closable container,  "dosed" with sulfur dioxide gas (vapor) and sealed tightly.

     C.  Corks should be stored in a cool dry location, not in a bottling room, barrel storage area, or chemical storage area. The temperature should be 55 to 70 degrees Fahrenheit and the humidity 50 to 70 percent.

    IV.  Moisture Content:

     A.  New shipments of cork, as well as corks which have been stored for extended periods of time, should be checked for moisture content before use. Corks below 5% average moisture level should be discarded or returned to the supplier for re-hydration and sterile packaging.

B.  Corks with an  average moisture content of over 8% should be regarded with suspicion as such a moisture level could support mold growth.

V.   Internal Bottle Pressure:

A.  Wine temperature  should be between 60-70 degrees F. If lower temperatures are used then the fill point should be adjusted down to compensate for expansion in the bottle when room temperature is reached. (Be sure to maintain legal fill volume.)

     B.  If the fill point is too high, less vacuum can be achieved.

     C.  The vacuum system should be well controlled and maintained. Gauges which continuously display vacuum status at the corking head and frequent (each 1/2 hour)  online QC of corked bottles (pierce test) are highly recommended.

D.  Bottles should remain upright for 24 hours after corking.It is recommended that the above elements be combined to produce a net effect of no more than 3 psi internal bottle pressure at 68 degrees F.
           
     

    COMMON WINE SPOILAGES

2,4,6, Trichloroanisole, also called TCA or "cork taint,"  is often mis- identified.  It has a distinctive "mildew" that is not easily forgotten once it has been experienced.  

 This unpleasant odor has been found in bottled water, wine bottled in screw caps, beer, and even raisins--none of which have contact with corks.  Thus it is more correct use the term TCA to describe it.  

Laboratory analysis by top wineries indicates that less than 1% of their wine is affected by TCA.  Unfortunately, much of what others call "cork taint" in wine is not accurately identified.  Below are a number of other types of wine spoilage and their characteristics, which can be found in wine.

Oxidation--a flat or caramel aroma. A flat, cardboard-like taste inthe wine, sometimes, but not always accompanied by a browning of the color of the wine.  Caused by  interaction of oxygen  with wine.

Hydrogen Sulfide--a rotten egg smell. Often due to lack of attention in winemaking.

Volatile Acidity--a sharp vinegar-like or nail polish smell. May be associated with acetic acid and bacterial infection.

Sulfur Dioxide--the odor of freshly burnt matches. Used as a anti-oxidant in wines. Caused by overuse of sulfites.

Brettanomyces--smell associated with cheese or wet horses. Normally caused by spoilage yeast in barrels.

Mercaptans--aroma is reminiscent of bad onions, cooked cabbage or burnt tires. Odors which  result from bound hydrogen sulfide. Caused by bacterial spoilage, usually originating in the barrels.

Quaiacol--a musty, vegetal smell.  A  very rare contamination from barrels or corks.

Geosmin--a smell of beets. Earthy. Extremely rare, it may originate in cork or barrel.

Geraniol--smells like geraniums or lemon grass. Increasingly rare by-product of potassium sorbate. Used as a preservative in wine.

Deccara--a burnt sugar smell.  The result of a poorly managed fermentation.

In addition, certain wines may be:

Overly tannic--a dry, puckering feel in the mouth.  Tannin is a natural component of the grape itself.

Overly alcoholic--a hot feel in the mouth.  Caused by fermenting grapes with high amounts  of sugar. Overly acidic--a sharp taste along the sides of the mouth--cause by unripe grapes or acidification.

        WINE CORKS: WHAT  ARE THE ALTERNATIVES?

Corks and corkpullers are an integral part of wine--and have been for nearly 300 years.  But every so often word comes of a new and improved seal for a wine bottle.  

Here is a simple analysis, comparing the advantages with the disadvantages of each.

       AGGLOMERATE CORKS:  

 These are made by binding together smaller pieces of cork into a single closure.  While less expensive than a true cork, they suffer from virtually every comparison-- they are not as attractive, they may not last as long as true corks, and they do not have the same resilience as cork--a critical element in making a perfect seal of the bottle.   

Nevertheless, some wineries are happy with these agglomerate corks for their less expensive wines designed to be drunk in the near future.

         COLMATED CORKS:

These are usually lower grade corks which are treated with a combination of adhesive and cork dust to fill the fissures and holes in the corks.  They offer a lower cost alternative to attractive corks, but do not offer equal appearance, performance, or image.

         THE SCREW CAP: 

Often mentioned as the epitome of cheap wine,  these closure do carry a negative connotation in the marketplace.   They are very inexpensive, but require a special threaded bottle.

Unfortunately, there are no long term studies to indicate how well these closures hold up under the long term storage planned for fine wines--there are also concerns about oxygen transpiration across the relatively narrow surface of the plastic seal. 

For the liner of a screw cap to seal effectively,  it must contain a high percentage of plasticine, which imparts flavor.   Lower percentages do not impart flavor, but will not seal as well.  Quality control is necessary to monitor this variable. Screw caps are easier to open and close than corks, but there are concerns about the bottling process, specifically the ability to draw a vacuum in the  headspace to remove  oxygen.

     THE BOTTLE (CROWN) CAP: 

This is very similar to the screw cap in every way--except that there may be even less evidence  in favor of long term aging potential.  They  are even less expensive  than screw caps, and also  require a special bottle.  TCA from cardboard case boxes can be transmitted  through the plastic liner of crown caps  into the liquid.

       THE SYNTHETIC CORK: 

Made from a plastic, this closure resembles cork, but is easily identified on close inspection.  It does not offer the same recovery from  compression, which means  that bottling lines must leave bottles upright for a time before they can trust the seal.  A number of other concerns about these stoppers  have been noted in the wine media.

             U.S. MILITARY SPECIFICATION STANDARDS 105D

    TOTAL CORKS      # BALES TO SAMPLE   # CORKS PER BALE              
    
    50,000                    2                 125

    100,000                   3                 125

    200,000                   5                 125

    400,000                   8                 125

    600,000                   13                125

    800,000                   13                125

    1,000,000                 20                125



Common Grape Guide

Vitis vinifera is the classic family of wine grapes and includes such renowned varietals as Zinfandel and Chardonnay. The vines originated in what's now southwestern Russia. In the United States, v. vinifera now thrives in California and the Pacific Northwest, and also does well in microclimates scattered from the Mid-Atlantic to the Midwest. V. labrusca is a family of vines that's native to North America. These vines are more hardy and disease-resistant than v. vinifera, but aren't quite as ideal for making wine. Hybrids, also called French-American hybrids, are a cross between v. vinifera and v. labrusca. Hybrids can produce excellent wines; they combine the superior wine-making qualities of v.vinifera with the toughness of v. labrusca. Below is a quick guide to some common wine grapes.

VITIS VINIFERA

Whites -

Pinot Grigio This fine Italian varietal lends itself well to dry, acidic, crisp styles.

Pinot Blanc A traditional grape of Burgundy, Pinot Blanc is a subtle varietal that should be gently taken through a cool fermentation and then barrel aged.

Muscat The Muscat family of grapes (which inclues Orange Muscat, Muscat Canelli and Muscat de Frontignan) all exhibit heady floral aromas while packing a strong fig-guava punch.

Gewürztraminer Typically thought of as a German varietal, this grape actually originated in northern Italy. It is often made in sweet or off-dry styles and carries floral and spice notes.

Riesling Laden with floral, apricot and peach notes, Riesling makes wonderful sweet as well as dry wines - all aromatic and lush in aroma and flavor.

Chardonnay Often called the "King of the White Varietals," Chardonnay has never been more popular among wine consumers. When crisp, bright and judiciously oaked, Chardonnay lives up to its royal title.

Sauvignon Blanc The "Other Chardonnay" is a native of the Bordeaux region of France. Sauvignon Blanc is relatively easy to make and can range from grassy and vegetal to fruity and floral. It is often fermented cold and not barrel aged.

Reds -

Syrah The Syrah grape originated in Asia Minor where it was called the "Shiraz" grape, as it still is by the Australians. Syrah makes up the primary red wines of the Rhone Valley of France and can make for lush, berry-cherry wines or spare, truffle-earthy wines.

Zinfandel Zinfandel is one of the most popular grapes grown in California and is known for its robust tannins, well-rounded aromas and lush flavors. Jammy, berry, fruit and black pepper are the most common descriptors.

Sangiovese The superstar of the Tuscan winemaking scene, Sangiovese takes a long, warm growing season to produce the best fruit, redolent of truffles, blackberries and black currants.

Cabernet Sauvignon Cabernet Sauvignon is perhaps the most famous grape varietal in the world. California's best red wines often are made of this grape, which is suprisingly easy to grow and make into wine. Abundant aromas and flavors are black currant, bell pepper, cedar and blackberry jam.

Merlot Merlot is the most important grape varietal grown in Bordeaux and forms the backbone of many "meritage" (Bordeaux-style) blends. It is similar to Cabernet Sauvignon, but displays more fruity than herbaceous or vegetal character.

Pinot Noir Burgundy's most important red grape varietal, Pinot Noir has become a sort of Holy Grail for winemakers of late. It is a very difficult wine to get right. Its brambleberry and coffee aromas often show their best in the most expensive cool-climate fruit.

VITIS LABRUSCA

Whites -

Niagara Known for its heady, heavily-scented wine, Niagara is a varietal grown for the bottle as well as for eating.

Catawba Hearty and productive, well-established in American winemaking history, Catawba tends to ripen late. So it often has inadequate sugar levels.

Reds -

Concord Concord is most famous for being the "grape juice" grape. It's also most likely to end up in a jam or jelly jar! Concord's distinctive grape-juice aroma renders it only suitable for winemakers who enjoy this element in their wines.

Delaware Small clusters and pink-skin berries distinguish this grape. When treated correctly, it can rival the aromatic and perfumed off-dry wines of Alsatian France and Germany.

Ives Not very resistant to cold or disease, Ives may be on the way out these days. But for decades, it was - and still is - known for port-style red wines.

HYBRIDS

Whites -

Seyval Blanc This hybrid can compete with some of the finest dry white wines made from Chardonnay and Chenin Blanc.

Vignoles With a delicate floral aroma, this white varietal has won many commercial and amateur winemaking contests.

Vidal Blanc Vidal Blanc is often used in late-harvest dessert wine styles but must be watched carefully in the vineyard. If left to ripen too long into a damp, early winter, mildew and bunch rot are quite likely to develop.

Reds -

Marechal Foch An early ripener with cranberry-currant flavors and a bright red color.

Chancellor Quite tannic and known for its plum-cedar aroma, this grape is susceptible to powdery mildew and must be carefully scrutinized before crushing.

Chambourcin Possibly the most abundantly planted red hybrid varietal, Chambourcin has blue-black berries with cherry-berry aromas.

Planting a Vineyard

SELECTION OF VINEYARD SITE

A desirable vineyard site should have adequate air drainage (free from trees and bushes), moderate degree of slope, and a deep, well‑drained soil. An adequate site with the proper soil conditions will produce large, vigorous vines which will return big yields. Shallow soil with poor drainage will produce weak vines. For this reason, vines set on poorly or slowly drained soils should be planted closer together in the rows in order to make use of the entire trellis area.

As soon as possible after the selection of a site for planting, it is advisable to consult your county agricultural agent about taking a soil sample and having a complete analysis made. The results of such an analysis can be used as a guide in preparing the soil before the roots are actually planted. Your county agricultural agent should also be consulted in interpreting the results of an analysis.

If there is any reason to believe, or the soil analysis shows, that the organic matter in the soil is low, every effort should be made to build this up by the addition and incorporation of such ma­terials as manure, cured hay or straw, wood chips, sawdust, etc. Nitrogen should be added to any of the other materials, with the exception of manure, at the time of the incorporation with the soil. Green cover crops, such as clover, turned under will con­tribute to the soil organic matter, but not to the extent that liberal applications of dry, ripe material such as straw or cured hay will. Because spring is the best time to plant vines in most parts of our country, the soil should be turned over thoroughly in the fall. This will allow time for the partial breakdown of any cover crop being turned under, which might seriously interfere with the planting operation if done in the spring. If practical to do so, some means of protection can be given the ground during the winter. A very thin layer of straw or old hay spread over the turned‑over ground for protection from erosion can be very easily disked into the soil in the spring without interfering with the planting operation. Even if it is not possible adequately to protect a vineyard area during the winter months, it is still better to turn the ground over in the fall. A large amount of unrotted organic matter in the soil will greatly lengthen the time involved in hand planting.

PURCHASING YOUR VINES

When selecting the varieties and vines for your home vineyard, keep the following in mind:

1. Yield and composition of the grapes under your soil and climatic conditions.

2. Inherent vigor of the vine.

3. Scion‑stock interrelationships. In many areas, desirable varie­ties must be grafted to soil‑adapted rootstock.

4. Susceptibility to disease.

5. The influence of environmental conditions‑rainfall, wind, fog, humidity, exposure, mean daily temperature, time of maturity.

6. The basic quality of the wine produced by the variety.

It is well, in making preliminary plans, to take a look through the vineyards of your region, noting the excellences and the faults. Seek the advice of the owners of good plantings. The United States Department of Agriculture, agricultural colleges, state ex­periment stations, and the county agent also give help that is almost indispensable in making selections of vines, as well as on the entire subject of grape growing. Still another source of in­formation and inspiration is the nurseryman's catalog. From these sources, plus the recommended species given earlier in this chapter, you should be able to select the best varieties for your vine­yard.

When purchasing the vines, select the best possible ones from a reliable nurseryman. (We have listed several in Appendix C.) 'The grapevines normally available to the grower for planting are sold under the following grades:

The grade 1‑X represents the very best grade of one‑year‑old vines grown during the past season. These are the "cream of the crop" and the number available each year is limited. Vines of this grade have consistently outgrown vines of the other grades and matured a year ahead of them. The premium price asked for 1‑X grade vines is well worth paying.

The grade 1‑1 represents the best average grade of one‑year‑old vines grown during the past season which have a good dense, sub­stantial root growth. The largest portion of the vines grown each year will be of this grade, providing growing conditions are op­timum. The 1‑1 grade vines are highly recommended for planting.

The grade 1‑2 represents the one‑year‑old vines with the top and root growth just below average. This grade of vine can be successfully used for planting, but will be slower in coming into bearing than the 1‑1 grade vines. If the 1‑X and 1‑1 grade vines are available, they should be purchased in preference to the 1‑2 grade vines.

The one‑year‑old vines which have made the poorest top and root growth are termed "culls." The abundance of culls in the nursery in any one year can depend on several factors. Poor wood used for cutting material will result in vines of cull grade. However, unsatisfactory top and root growth are not necessarily the result of this. A wet, cool growing season will result in a large number of culls due to insufficient root growth regardless of how good the cuttings were at the time of planting in the nursery. A very dry growing season will also cause the number of culls to be proportionately greater.

The best of the culls from the one‑year‑old vines and the grade 1‑2 vines not sold on the market are planted in the nursery the following spring and permitted to develop an additional season. When these are removed from the ground in the late fall and graded, the most vigorous vines are sold on the market as grade 2‑1. This grade of vine is satisfactory for planting providing that the root growth is dense, vigorous, and compact. In purchasing vines of this grade, the grower should not accept vines with a long, coarse root system, nor should he accept vines with a scanty root system. A general recommendation can be made to all growers, regardless of the variety and grade they are buying: be sure that the vines have a good, substantial, healthy, and sound root system.

It is not difficult to propagate your own rootings from cuttings. This can be done to expand your vineyard from your own vines or obtain stock from vines that particularly interest you. The simplest way to do this is to make cuttings with three buds from the varieties you want while the wines are dormant. The cuttings are bound in bundles, kept cool and moist, and dug in sand or sawdust until spring. Then they are trenched into the ground with only the top bud exposed. If cultivated with a hoe or trowel and kept in moist soil, the cutting will develop roots and foliage that can be handled as regular nursery stock in the fall.

A few precocious vines bear fruit two years after being set in the vineyard; most varieties bear at three years; and a few do not begin to bear until they have been planted four years. None, of course, come to full bearing until several years later. These ages are modified by soil, climate, and the care given the vines, though nature cannot be hurried greatly by rain.

PLANTING A VINEYARD

The difficulties of planting a home vineyard are greatly exag­gerated. If the land is properly prepared, and the vines in good condition, planting is easily, safely, and quickly done. For in­stance, the slope of the land largely determines the direction of rows. On sloping land, rows should follow the drainage grade laid out by local soil conservation technicians. Such a planting plan is the best way to prevent or reduce erosion and to preserve the site for the long life of the vineyard. Rows at right angles to the slope (cross‑slope planting) are a better arrangement than rows parallel to the slope, and when the vineyard consists of both slope and level ground it is also best to run the rows at right angles to the slope.

Space needed by power equipment, if you plan to use it, largely governs the distance between rows in the vineyard. Rows spaced 7 or 8 feet apart allow ample room for any home vineyard power equipment‑tractors and sprayers‑now in use. It is suggested that vines be set 8 feet apart in the row. However, in experiments highest yields have been obtained at closer spacings, especially between rows. If low vigor is anticipated, vines should be planted closer than 8 feet apart in the row to get more plants in a given area and higher yields.

There are many ways to mark the field. If it is to be planted along a drainage grade, the curved rows are already marked. To get straight rows, you can drive a white stake at each corner of the proposed planting, then drive other stakes at 7‑ or 8‑foot intervals between the corner stakes, using a 7‑ or 8‑foot pole to measure. By keeping the end stakes in line with the corner stakes, the pole affords an easy way to space the rows. A pole the length of the vine spacing can be used in the row to space each vine as it is planted.

In setting grapevines, these essentials should be kept in mind:

1. All the roots that are alive and sound should be retained and kept moist and cool until covered by soil.

2. All these roots should he set 12 to 15 inches deep, be reason­ably spread, and be firmly packed with friable soil. The union of grafted vines should be several inches above the vineyard floor.

Within these conditions, a wide array of planting techniques is successful. Usually, planting is done by hand in a furrow. The vine spacing is measured by a pole of the correct length, or by a planting wire marked at appropriate distances and stretched along the furrow. It is inadvisable to put any fertilizer in the furrow or hole at planting time because of the danger of injuring the roots.

The top of the new vine should be pruned to the best single cane and this should be pruned to two or three buds. When the new shoots are no more than one inch long, all except the two topmost are broken off to promote growth in height. If the 1‑inch shoots cannot be broken off at the proper time, the best cane should be pruned to two buds at planting time. If fruit clusters develop, they should be removed in early summer.

A major cost in establishing a vineyard is the trellis. It should be constructed during the first growing season or the following spring; further delay will postpone the harvesting of profitable crops. All vertical trellises for commercial vineyards in New York, for example, are of the same general type: two or three wires, one above the other, stretched tightly on firmly set posts. Two wires are adequate for umbrella Kniffin and 4‑arm Kniffin, the most common systems, but three wires are necessary for some other training systems. For vine vigor that is at least average, the top wire of the trellis should be 51/2 to 6 feet above the ground to provide good exposure to sunlight and to facilitate insect and disease control. The bottom wire should be 2/2 to 3 feet above the ground. Comparisons of yields of vigorous vines on trellises 4 feet high with those 5 V2 feet high have shown signifi­cantly higher yield and higher soluble solids from vines on the higher trellises. These increases were noted only if the vines were sufficiently vigorous to cover the trellis completely with foliage in August.

Posts serve two functions. The intermediate or line posts pro­vide vertical support for the trellis wires. Although the end posts support the wire, too, their main purpose is to provide anchor points for tightening the wires.   (to be continued....)