VINKEM

CORK

TESTING PROCEDURES

& PRACTICES

The Supplier to the Australian Wine Industry which introduced a Taint Testing Regime in accordance with…

The Australian Standard AS1199!

Would you expect anything less from your Cork Supplier?

PROCESS CONTROL SUMMARY

GOODS INWARDS

1. Moisture Content

2. Taint Test

3. Grading

FINISHED GOODS

Moisture Content

Treatment Integrity Test – Wine Travel Test

3. Extraction Test

Packaging

GOODS INWARDS Q.A. REPORT

The following procedures are carried out on the arrival of a cork container at Vinkem Pty Limited.

1. MOISTURE CONTENT OF CORKS

The amount of moisture present in wine corks is expressed as a percentage of the corks' dry weight.

The moisture content of corks will be generally between 5% and 7% on arrival in the cork user's store.

Each bale is randomly checked by pulling out 10 corks and measuring their moisture content of the corks using an "Aquaboy" moisture meter. Moisture contents of up to 7% are acceptable.

GOODS INWARDS Q.A. REPORT cont.

2. TAINT TEST

(Ref: Australasian Grapegrower & Winemaker Technical Edition, June 1997, page 62 and 64)

The sample size is in accordance with AS1199 General Inspection Level II

For example: - A. cork is placed individually in a 100ml Schott Bottle and filled with neutral dry

DOUBLE SAMPLING PLAN

AQL 1.5

BATCH SIZE			Accept / Reject
10k - 35k	1st	80	2	7
	2nd	80	6	7
35k - 150k	1st	125	3	8
	2nd	125	8	9
150k - 500k	1st	200	5	10
	2nd	200	12	13
500k +	1st	315	5	10
	2nd	315	12	13

If the taint falls between the accept and reject level on the 1st trial then do the 2nd trial.

(A) Each cork is placed individually in a 100ml Schott Bottle and filled with neutral dry white wine which has not been in contact with either cork or oak.

(B). The corks are left for 16 hours (overnight) and evaluated the following morning for evidence of taint.

(C). Set out above is the acceptance number and rejection number of tainted samples per batch size.

(D). However, the customer has the right to impose more stringent acceptance and rejection criteria on Vinkem.

With a sample size of 500 corks the following statistical data for a particular result can be expected.

An average of 2% (or 10 corks) tainted, will with 95% confidence give an expectation of between 0.8 and 3.2% taint in the population. However, the chances of the batch having 3.2% taint is only 5%.

An average of 3% (or 15 corks) tainted, will with 95% confidence give an expectation of between 1.5 and 4.5% taint in the population. Similarly, the chance of the batch having 4.5% taint is only 5%.

References "Introductory Statistics" by A.H. Pollard

"AS 1199 Sampling Procedures and Tables for Inspection by Attributes"

Technical Review (112) 1998

Institute Notes

Screening of corks for taint

Recent experiments conducted in our laboratory have indicated that when four corks are added to 200ml of wine that has been spiked with TCA, up to 80% of the TCA can be absorbed from the wine by the corks in 24 hours, and up to 90% in 48 hours. Methods commonly employed by industry for screening batches of cork for possible taint involve soaking 20 lots of five corks, each

in 200 – 500 ml of wine. If a wine that has been in contact with five corks appears to be free of cork taint, then it is assumed that none of those five corks was contaminated with TCA. However, if one cork out of five was contaminated with enough TCA to impart a weak to moderate taint to a wine, this would not necessarily become apparent to an assessor because most of this taint could be reabsorbed by the four clean corks.

These results indicate that current screening procedures are likely to underestimate significantly the proportion of corks in a batch that are tainted. Our laboratory will, therefore, be investigating alternative screening strategies. In the meantime, industry should consider soaking corks individually for screening, even though this entails an increased workload for all concerned. In developing alternative methods for taint assessment, we will endeavour to get around the reabsorption problem without industry having to resort to such an increased workload in the future.

Mark Sefton

Senior Research Chemist

3. GRADING

Following, is a grading sheet that is used to identify the grade of cork.

CORK GRADE QUALITY LEVEL REPORT

STRAIGHT WINE CORKS

Date:__________________ Date Received:_______________

Container Ref No:______ Lot Size:_____________________

Cork Size______________ Grade__________ Sample Size:_________________

DEFECT DESCRIPTION	CRITICAL	NON-CRITICAL
Belly Spots
Broken Edges
Cracks
Cut close to Bark Face
Cutter Grooves
Green Wood
Growth Rings
Large Holes
Large fissures on Cork Ends
Out of specification, Dimensionally
Woody Corks
Dry Year Line
TOTAL
PERCENTAGE OF SAMPLE

V.K. RATING__________ SIGNED_____________________

COMMENTS__________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

"THE VK RATING SYSTEM"

We use an in-house system called the "VK RATING SYSTEM". This is a score out of 100 whereby we factor the critical and non-critical faults and subtract from 100.

METHOD:

From the taint-testing sample taken from the shipment, (see Section 3), 100 corks are examined for the incidence of faults.

CRITICAL FAULTS are multiplied by 1.5

NON-CRITICAL FAULTS are multiplied by 0.5

The results are then summed and subtracted from 100.

EXAMPLE:

If; Incidence of Critical Faults is, 5%

And; Incidence of Non-Critical Faults is, 20%

Multiplying by weighting factors:-

CRITICAL: 5 x 1.5 = 7.5

NON-CRITICAL: 20 x 0.5 = 10.0

Therefore the VK Rating = 100 - 17.5

= 82.5

VK Rating Cork Grade. VK Rating Cork Grade.

91 - 00 Ref Fleur Grade (Tops Plus). 61 - 65 Ref 2 Grade

81 - 90 Ref Tops Grade 56 - 60 Ref 3A Grade

76 - 80 Ref 1A Grade 51 - 55 Ref 3 Grade

71 - 75 Ref 1B Grade. 46 – 50 Ref 3 SP Grade

66 - 70 Ref 2A Grade 41 – 45 Ref 3B Grade

"THE VINKEM CORK COATING SYSTEM"

A highly effective and proven Coating Process using FDA & EEC approved Products that satisfy the most stringent of Wine Travel and Sealing tests and demands. Coatings are measured and applied individually for each lot and atomized over the corks with our "Ultra Clean Air". A filtration system which ensures "contaminant free" carrier air.

Cork Defects.

Defects in corks can be of two forms, either cosmetic or physical. Cosmetic defects are generally of a non-critical nature, whereas physical defects can be of a critical or non-critical form, depending on the seriousness of the fault. Critical defects can be generally defined as those that are likely to cause leakage, or hinder corking.

A non-critical defect can be generally defined as one that may promote some wine travel into the cork, or more commonly, between the cork and the glass without directly leading to leakage, or to creating difficulties during the corking process.

Defects such as green wood, fissures (piths) on cork ends, a large number of lenticels or connected lenticels, belly spot grooves and woodiness can promote leakage.

List of Cork Defects.

In addition to the general blend mix guidelines and parameters, certain defects in individual cork stoppers are unacceptable at different cork grade classifications.

Defect levels for each grade are determined as follows: -

1. Grooves.

A cutter channel of 66% or more of the length and of a depth of 2mm of the cork is an unacceptable, critical defect. Non-critical acceptance levels are up to 66% of the cork length.

2. Green Wood.

A critical defect is characterised by deep folds and dents extending over 50% of cork length of a depth of 2mm or more in the surface of the cork.

3. Cracks.

Cracks that will cause ends to chip, and cracks running with the length of the cork are objectionable. In the latter category, cracks over 50% of the length of the cork will be counted as critical, regardless of depth. In addition, cracks of less than 50% of the length of the cork, but 2mm or more in depth, will be counted as a critical fault.

4. Woody Corks.

This defect is apparently caused by cutting the cork too close to the bark surface, leaving hard pieces in the cork surface. Rough bark-like surface exceeding 50% of the cork length will be counted as a critical defect.

Cork Defects cont.

5. Large Holes.

This defect is more predominant in lower grade cork. Holes are in part, due to insect damage of the corkwood. Any large holes over 2mm in diameter and connected or joined for more than 50% of the cork length will be regarded as a critical defect. This is, in effect, the measure of the number of and size of pores within a cork.

6. Belly Spots.

This defect is caused by cutting the cork too close to the inside surface of the corkwood.

Belly spots more than 2mm in depth and covering 25% of the cork length will be counted as a critical defect regardless of their length.

Belly spots covering more than 50% of the cork's length, regardless of their depth will also be regarded as critical.

7. Pithy Fissures or Lenticels on Cork Ends

These are soft, pith-like tubes evident on the ends of the corks. This defect is more evident in lower grade corks. Lenticels running the diameter of the cork, and more than 2mm wide, are counted as a non-critical defect in determining cork grades.

8. Broken Corks

Corks with 20% of the cork's length missing, broken off etc., will be considered to be a critical defect, and are totally unacceptable.

9. Chipped Cork Edges

Corks with greater than 40% of the circumference broken off from either end of the cork are regarded as being critical defects.

10. Foreign Odours

Foreign odours emanating from the cork of either microbial origin or chemical contamination, are totally unacceptable.

11. Growth Rings

Must be more than 5 rings or less than 5mm between rings. If not, this is considered a critical defect.

12. Cork Dimensions

Cork dimensions are included in the " Cork Grading " section.

The tolerances allowed for cylindrical stoppers are as follows:-

For Length L +/- 0.5mm

For Diameter D +/- 0.4mm

FINISHED GOODS Q.A. REPORT

MOISTURE TEST

As was carried out in the incoming raw corks, the amount of moisture present in wine corks is expressed as a percentage of the corks' dry weight.

2. TREATMENT INTEGRITY TEST & WINE TRAVEL TEST

The Treatment Integrity test is a simple test, which is applied to determine the effectiveness and stability of cork coatings. To check coating stability, 6 bottles are filled with a 12% aqueous alcohol solution with dye added. Corks are then inserted into the bottles. The bottles are then incubated for 24 hours @ 35° C after which the bottles are examined for evidence of Wine Travel.

3. EXTRACTION TEST

Twelve "Cetie Finish" bottles are plugged with the test corks from each treated batch. Six bottles left @ room temperature and six bottles placed in refrigerator and left for approx. 16 Hours. The corks are extracted using a force-measuring gauge and the result recorded in Newtons. Extraction force range required is 180N to 250N.

VINKEM QUALITY ASSURANCE CERTIFICATE

Order Number Size Grade____________

Quantity: Container Reference:

Print Description: Wash Type:

Treatment Ref:

Cork Grading: _____% Critical Faults _____% Non-Critical Faults

Average VK Rating _______

Taint Test : Sample Size:_____________

Total taints:______________

Extraction Results: (Newtons)

Average Extraction: ________________ Newtons

Moisture: Moisture Minimum: ________________

Moisture Maximum: _______________

Moisture Average: ________________

Signed: ____________________

GOOD CORKING PRACTICES

1. Corker Jaw Type:

The 4-segment sliding jaw type cork compression system is recommended. Other types such as Roller or Iris jaws can lead to wrinkles / creasing of the cork which may result in leakage.

Corker Maintenance Check:

That Machines are maintained to suppliers specifications.
That Jaws move in a smooth consistent manner during compression.
That Jaws are free of any kinks or damage.
That bottle is correctly aligned in centering bell to ensure seal of bottle.
That the Vacuum System (including lines and gauges) be well maintained and integrity verified by checking bottles on-line (every 30 mins – pierce test).
That Plunger is correctly centered and adjusted for cork insertion, 1 – 2 mm from bottle lip..
That daily cleaning of cork handling surfaces such as Hopper, Feed tube, Orientater, jaws, Plunger etc.
That a 24mm cork not be compressed to less than 16 mm.

Cork Handling & Storage:

a. Upon receival corks should be stored in a Cool Dry Location (NOT Bottling Room, Barrel or Chemical Storage areas). Storage temperature should be 15 to 21 ° C with humidity 50 to 70%.

Cork Bags should not be opened until just prior to use at the hopper. Corks should not be left in opened bags or container.
Corks recovered from corking machine after bottling should be returned to the polyethylene bag or another food grade container, "dosed" with sulphur dioxide Gas and sealed. Refer item 3a for storage recommendations.

Moisture Content:

a. Corks which have been stored for extended periods of time (greater than 9 months) should be checked for moisture content prior to use. Corks returning an average of less than 5% should be discarded. Alternative arrangements can be negotiated with the supplier for re-processing.

For best sealing performance, inner neck of the bottle should be dry.

Internal Bottle Pressure::

At bottling, ideal wine temperature should be between 16 - 21° C. Lower temperatures will require "Fill Height" adjustment downwards to compensate for expansion in the bottle when ambient temperatures are reached.
Expansion in the bottle will create an increase in pressure.
Fill height being too high will also reduce Vacuum efficiency. Note; refer item 2e re vacuum efficiency and maintenance.

Bottles should remain upright for at least 24 hours after corking. Note; It is recommended that the combined parameters above should result in internal bottle pressure of no more than 3 p.s.i. (0.2 bar, 21 Kpa) at 20 ° C.

The above information is offered as recommendations, which together will promote enhanced bottling / cork performance. It does not account for wine condition and / or preparation at time of bottling.

Thank you for choosing VINKEM Pty Ltd

Jose Gomes Da Rocha

P.O. Box 58 VALADA

4538 Santa Maria De Lamas Codex

PORTUGAL.

Contact: Mario Da Rocha

The father of the present owners formed the company in 1967. In 1992 the three sons purchased it and under their direction the company has sustained continued growth.

The plant has been equipped with the most sophisticated equipment available thus enabling it to positively respond to the varying market demands.

Da Rocha’s production is currently around 150 million corks from which half is committed to annual supply contracts to major clients, including those based in Australia, France, USA and Germany.

They are well established in the main markets, with the increase of share resulting from the ability to deliver in excellent, consistent qualities, correct finishing in treatments as requested, and at competitive prices.

Cork Purchasing by Da Rocha

All Da Rocha Cork Bark (Planks) is purchased in the Alantejo region in the South of Portugal.

They have two main suppliers for the wood, which is bought direct from the forest. This direct purchase represents at least 80% of their annual stock.

They have been doing this for the past 20 years and it is this personal purchase which gives confidence and consistency to its product.

Da Rocha also buys a small percentage of wood in stacks (or bales) which have already been sorted for use by the wine industry. This wood is purchased in two categories namely; Reference A and reference B.

Manufacturing Process

STRIPPING

The "Reproduction Cork" which is the third re-growth of the cork oak bark provides the required stopping properties of cork. This is the grade of cork, which is used for the wine industry. Following the stripping the cork planks are stored in the open for at least 6 months.

During this "Seasoning Period" the effects of rain and sun result in several chemical changes, which better suit the cork’s intended use.

This seasoning results in;

Leaching of sap
Removal of greenness
Polyphenols oxidation
Texture stabilisation

BOILING OPERATION

This operation is undertaken in two stages. At the first stage an aqueous extraction at boiling temperature takes place thus identifying chains, Polyphenols (the tannin content is reduced by more than 50% and sugars in batches.

At the second stage the cork is again boiled in order to increase the size and improve its visual appearance by cleaning the surface.

The cork will increase in length, height and endure a linear decrease in width. Each stage lasts for 45 minutes.

The water in the "boiling" tanks is changed every 1 or 2 days.

RESTING PERIOD

The cork planks are rested for three weeks so as to achieve a decrease in moisture and to allow the cork to stabilise "mechanically" The stabilisation room is well ventilated and is environmentally controlled (RH<70%) to prevent microbial growth.

The cork’s microflora is virtually killed during the boiling procedure. Very few thermophile species survive.

SELECTION & CLASSIFICATION OF CORK PLANKS

The cork Planks are selected for the appropriate quality (Grade) required for cork stoppers. Experienced workers undertake this critically important stage.

SLICING

The cork planks are cut in to strips, which are slightly wider than the final length of the cork.

PUNCHING

Following the slicing operation the corks are punched. At this stage the corks are punched in the perpendicular direction of the growth of the cork. This results in the cork lenticels remaining in the transversal position when inserted in to the neck of the bottle. This reduces the possibility of leakage.

Due to the variability of cork in any given strip, it very much depends on the operator doing the punching to obtain the best possible quality from each strip.

DRYING

Prior to polishing, the corks are dried (to a level less than 10% humidity) so that dimensional properties are stabilised to desired end. They are then ready for the next stage of processing.

POLISHING - THE WASHING PROCESS

There are many washing methods i.e. Peroxide or as in the past Chlorine or even PMS).

Today the most common wash type is with Peroxide. The washing is conducted in a specially built machine, which has a computer-controlled process thus reducing potential for human error, and allows for consistency of each cycle.

The corks are showered continuously with Fresh Product (this bleaching product is Not recycled). The corks are tumbled and centrifuged several times during the work cycle, which also provides an efficient dedusting and cleaning process.

The Washing Process

Introduction of water by shower
Centrifugation
Washing with a mix of water perydrol (H2O2) and Cinelave NH. These products are atomised over the corks whilst the drum rotates for 15 minutes.
Empty corks from drum.
Reintroduce corks in to drum and shower corks with water for 10 minutes.
Introduce water and hydrol (citric acid) over corks in rotating drum for a further 15 minutes.
Centrifugation and emptying from drum.
Corks are deep washed until a pH level of between 6 and 7 is attained.
Heat the corks so that a lighter "Bleach Colour" is attained. (varying "Bleach Colour" is possible)
Corks are then ready for centrifugation and drying. Following this cycle the corks relative moisture is between 6% -8%.

DRYING

The corks are dried in atmospheric or vacuum ovens. This stage is closely controlled to ensure internal moisture is eliminated without damaging the cellular structure of the cork.

The target moisture level after drying is 5% - 8%. If moisture is lower than 5% at bottling elasticity and therefore saleability is negatively affected. Conversely if moisture is greater than 8% potential for microbial growth is increased.

In Australia VINKEM P/L Moisture adjust cork batches as required so that prior to Treating / Coating and thus end use by the customer cork is received at around 6% to 7.5%).

SELECTION

The cork stoppers are selected according to their specific characteristics; there are 7 categories.

Initially corks are "graded" by electronic measures. Following this stage workers at the

Da Rocha Plant further separates the corks in to specific qualities. The process under which these corks are manually selected is via a conveyor belt passing the corks in a rolling motion by the workers.

BRANDING

Corks are branded by ink and / or fire branding as specified by the customer.

PACKAGING

Corks are sent to VINKEM Raw and in bales of 5,000. They are stored in a clean and dry warehouse until required for processing.

SURFACE TREATMENT

Jose Gomes Da Rocha sells corks fully treated and ready for use to many customers worldwide. In Australia VINKEM P/L import the corks "Raw" and Process and Treat the corks in-house in its modern plant.

Food Grade and approved paraffin’s and silicones are used to coat the corks.

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