Informative material kindly provided by APCOR

Bottling, shipping and storage of wines are crucial stages in the life of the wine, and some basic rules should be followed to obtain the most from the properties of the cork stoppers, which are:

In the selection of stoppers appropriate for the bottles used and for the type of wine to be;

In the correct storage of the cork stoppers before bottling;

In bottling (with special care in the correct use of stoppers in the filling line, especially in regard to the suitable conditions of the clamps), shipping and storing of wine.

Compliance with these rules is decisive in ensuring quality when the wine is consumed.

As stoppers to be used must be chosen while accounting for the bottling machine, the type of bottle and the siz e of the neck, as well as the type of wine to be bottled and the circuit expected for the wine on the market (shipping and turnover time).

For most wines, and keeping in mind the int ernal size of the neck, the diameter of the natural stopper should be at least 6 mm larger than the smallest diameter of the neck.

For longer aging in the bottle, a diamet er of more than 6 mm is recommended, but no more than 8 mm.

Due to their higher density, if using technical or agglomerated stoppers, the size should be 1 mm less in selecting the diameter.

The stopper should be both longer and larger in diameter when the aging time scheduled for the wine in the bottle is longer. However, in relation to the length of the stopper, the space required between the lower end and the surface of the wine should always be observed (a minimum of around 15 mm) so as to have an expansion chamber to compensate for any expansion of the wine due to thermal effects.

For wines with some gas ( internal pressure above normal), stoppers should be chosen with a larger diameter than those recommended for still wines. In general, and as an example, for wines with about 1 bar internal pressure, a diameter of 8mm larger than the smallest internal of the neck is recommended (Figure 1).

Whenever possible, cork stoppers must be used soon after being received. Long periods of storage should be avoided. The maximum advisable period is up to 6 months, in the appropriate storage conditions.

Stopper packaging should only be opened when stoppers are to be used. In general, stoppers are packaged in bags containing SO2. This gas acts both as an anti-septic and antioxidant, protecting the stoppers.

Unused stoppers should be returned to packaging in bags with SO2 (between 0.5 g and 4 g of SO2 per bag of 1000 stoppers).

Storage of the stoppers should be:

In a cool dry place at a stable temperature of between 15 C (59F) and 20 C (68F ) and at a relative humidity of between 50% and 70%(Figure 2);

ln places free of smells and without mold, away from any type of fuel, or products containing chemicals, such as cleaning products or paints, for example;

In places where there is no wood treated with chloride products (for example in structures with recently built roofs, or on shipping pallets).

Compliance with all these recommendations is essential so that when bottling, the stoppers continue to have the same physical and chemical characteristics and are not subject to any kind of outside contamination.

Making use of the compressibility of cork, the bottling machine compresses the stopper so that it can be inserted into the neck of the bottle.

Suitable compression is carried out when the stopper is 2mm smaller than the smallest diameter of the neck and when greater compression of the diameter of the stopper of more than 33% is avoided. Thus, a stopper of 24 mm diameter should not be compressed to a diameter smaller than 15.5 mm for insertion into a neck of 18.5 mm diameter (Figure 3).

Compression must never be more than 33% of the diameter of the stopper, as there is a risk that this could compromise its elasticity, with loss of part of the memory and consequent difficulty in correct sealing of the wine in the bottle. Thus, for a stopper of 24mm in diameter, the recommended compression is of about 8mm (which is equivalent to the 16.5mm as mentioned previously).

Making use of its elasticity, the stopper recovers its volume in the first 5 to 10 minutes after being corked, adapting itself to all the irregularities of the neck; and, after just one hour, a uniform force is exercised over the whole surface of the glass. To this end, it is advisable that the bottle not be placed in the horizontal position soon after being corked (Figure 4).

In the case of bottling lines where corking comes immediately before the bottles are laid horizontally in their boxes, the risks can be minimized by prolonging the time that the bottle remains on the conveyor belt from the corking machine to the labeling machine. All that is needed is to add some sections of track, making a tight “S” bend so that space is not wasted.

During shipping and also when in storage at the distributors, with rare exceptions, the bottled wine is not immune to variations in the ambient temperature. These variations in temperature are responsible for the:

Variation in the diameter of the neck of the bottle due t o the natural effects of contraction or expansion of the glass;

Variations in the volume of the wine. As a guide, wine expands on average about 0.2ml for each degree centigrade (33.8F) of rise in temperature, increasing the internal pressure in direct proportion.

Although the variations in diameter of the neck can naturally be compensated by the excellent elastic properties of the cork, the same cannot be said in relation to the variation in volume of the wine and consequent variation in internal pressure. To avoid this problem, the following recommendations should be followed at the time of bottling:

Bottling the wine at an ambient t emperature of between 15 and 20 Celsius (59F to 68F) to obtain an appropriate volume of the wine (Figure 5);

The bottling machine, with the correct selection of the length of the stopper, should be calibrated to allow at least a space of 15mm between the surface of the wine and the stopper (values for 750 ml bottles). This free space is essential to allow the expansion of the wine if the temperature rises during shipping or storage (Figure 6);

In sparkling wines, this spacing should be greater;

To minimize the effects of alteration of the internal pressure which may lead to leakage of the wine, it is recommended that it be done in a vacuum or by injecting CO2. The CO2 is gradually absorbed by the wine, and ends up creating a small amount of depressurization inside the bottle. Bottling in a vacuum or by injecting CO2 protects the wine better against premature oxidation and may assist in the prevention of microbial multiplication (Figure 7);

The internal pressure of bottles that have just left the bottling line must be checked frequently to confirm that the vacuum or injection of CO2 system is functioning correctly The internal pressures, in the case of still wines, should be as close as possible to zero (Figure 8);

At limit conditions, high internal pressures hinder the perfect adaptation of the stopper to the neck after bottling and tend to force the discharge of wine in order for the internal pressure to come into balance. In these cases, the wine does not leak continually, but a few milliliters are expelled until the internal pressure is re-established. This is not a problem with the stopper, but rather with the internal pressure of the bottle.

Further care to be taken at the time of bottling:

1. Regarding the place of bottling, care should be taken that:

It is free of insects, especially wine moths (Figure 9);

It is correctly ventilated using a ventilation/forced exhaust system;

That it is at a constant ambient temperature of between 15 C and 20 C (Figure 10).

2. The bottles should be taken from the pallets only at the time of bottling. Before bottling, the bottles must be w ell washed and thoroughly dried (almost all bottling machines do this automatically).

3. Pallets with bottles should be k ept in a warehouse at moderate temperatures and in a dry place, free of mold and free of chloride compound treated woods. The pallets should have planks, which are not made of cardboard or wooden composite material, to separate the bottles from other materials.

4. Never pass the stoppers in water or wine before bottling. In the past this technique was used to clean the stoppers or to facilitate their insertion into the neck, but this meant that these liquids accumulated in the pores of the stopper, and developed tastes and aromas that could slowly migrate to the wine. Currently, stoppers come fully ready to be used, and need no treatment or additional operation. If the stoppers must be cleaned for any other reason, then it is recommended that a solution of sulfite be used, releasing SO2.

5. The interior of the neck of the bottle must be clean and dry. A damp neck has a thin incompressible liquid film which hinders the expansion of the stopper, as well as reducing its adherence to the glass (Figure 11).

6. In standard bottles, the top of the stopper should not be more than 1 mm below the top of the neck. Ideally, the stopper should be +/- 0.5mm from the top of the neck. If the stopper is too far in, this may cause a rise in the internal pressure (if not using bottling by vacuum or CO2) and create a space between the stopper and the capsule which will only serve to promote the formation of fungus. If the stopper is too far out, there will certainly be problems when it comes to placing the capsule.

7. Stoppers with humidity of less than 4% should undergo a process of rehydration at the supplier’s premises and stoppers with humidity of more than 9% should undergo a process of drying at the supplier’s premises.

The maintenance of bottling equipment is fundamental to obtain good performance from the stoppers and consequently to prolong the life of a wine. Here are some measures to be taken in relation to the equipment:

Maintain the feeder channels of the stoppers very clean, as well as all the mechanisms of the machine;

Ensure the alignment of the pist on and the upkeep and alignment of the centralizing cone. This is essential for the correct introduction of the stopper

in the neck (Figure 12);

Check the level of wear in the compression jaws frequently

as the least wear or defect can make lateral grooves in the stopper which may lead to leakage of the wine or infiltration of air (Figure 13);

The bottling machine should work smoothly, especially during compression of the stopper, but also quickly, above all, at the time of introduction of the stopper into the neck (Figure 14);

Keep all surfaces where the cork stopper passes clean, using chlorine free products (Figure 15);

Before starting to bottle, the machine should be sanitized. Washing with a jet of a solution of water with metabisulfite at 80 degrees centigrade is recommended (176F) followed by drying any water condensation.

The flow or “Couleuse” is a defect in which the wine passes between the neck and the stopper. This problem may have various causes and can be avoided by following the rules already mentioned. This problem almost always is the result of a combination of various factors and is never easy to identify systematically and in a clear manner.

The causes of this problem are:

Excessive internal pressure. An excessive internal pressure does not give rise to a continual leaking of the wine, but rather to a temporary loss of a few milliliters of wine. This leaking occurs only until the internal pressure of the bottle is re-established;

Defects in the compression jaws. These defects may result from wear of the jaws and result in grooves on the surface of the stoppers;

Unsuitable diameter of the stopper, resulting in an insufficient force against the neck, compromising its impermeability;

“Green spot”. This is a problem that may arise in a stopper produced from cork which has not been properly dried. Only when green spot is present in a stopper in large amounts will this cause flow. A stopper that has “green spot” will reduce its volume inside the neck, very probably becoming creased at the sides, allowing the wine to pass. This is a completely random problem and very rarely appears in finished stoppers, since the various stages of production are rigorously controlled, from inspection of the planks to visual control of the finished stoppers;

Channels – worm and ant holes. Caused by insects when the cork is on the tree. This defect is easily detectable after the cork has been harvested and as such is extremely rare in a finished stopper;

Fabrication defects. These are problems that may arise during the production process, but which are in general easily detectable, as there is a rigorous quality control during the various stages of the manufacturing process.

Because of the adverse conditions that bottled wine is subject t o during the long journeys to be made to arrive at its destination, it is recommended that bottles always be transported in the vertical position(Figure 16).

The use of thermally insulated containers is recommended and the cooler seasons of the year should always be chosen to ship wines, especially for wines which have to be shipped between continents.

If the wine is to be shipped in maritime containers, the last type of cargo used in the container should be informed. If the container is not clean, free of smells and completely dry, it must be rejected. If this is not possible, it should be cleaned with a solution of metabisulfite and then properly dried, for example.

Humidity due to condensation during shipping leads to the appearance of fungi which may later lead to the formation of chloroanisoles or other compounds responsible for undesirable odors.

The expression “the cellar makes the wine” is as old as it is true. The temperature, humidity and hygiene of a cellar contribute to the final quality of the wine. The cellar should have the following characteristics:

Ambient temperature of between 15 C (59F) and 20 C (68F), with no great variation either during the day or throughout the year;

Humidity of between 50% and 70%;

The cellar should be free of insects and rodents. This does not include spiders, as these are excellent predators of undesirable insects;

The cellar must not have chemically treated wood;

The cellar must be free of odors;

Chemical products, such as paints or cleaning products must not be stored in the cellar;

The bottles must be kept in a horizontal position so that the wine is in contact with the stopper and so that it keeps its excellent elastic properties.

in “Manual Técnico de Rolhas PT 2015 – APCOR”