Soaking of corks - Microwaving of corks?

Cork Questions: Wine Wizard

Issue

Dec 06/Jan 07

Dear Wine Wizard, I’ve heard both “yes” and “no” on soaking corks before bottling. All of the commercial wineries I’ve visited don’t soak their corks before bottling. Can you set us straight on whether to soak or not to soak? Jack Anders Lindenwold, New Jersey Wine Wizard replies: No commercial wineries that I’ve worked with soak their corks before bottling because it’s not necessary for larger-scale businesses. Commercial wineries buy corks by the thousands from reputable companies with high turnover. They buy full bags and only order enough for their scheduled bottling runs, ensuring that small excess quantities aren’t left over to dry out, get dusty and become unusable over time. They ensure that their suppliers (the cork companies) test for moisture content, screen for TCA and spoilage microbes and deliver fresh, clean, ready-to-use corks. The corks come right out of the hermetically sealed, sulfur-dioxide sparged, factory-packed plastic bag. The problem for small-scale and boutique winemakers is that it can be harder (not to mention more expensive, since they can’t match a big winery’s economy of scale) to procure such a high quality and consistent cork supply. This is probably, in a roundabout way, the reason why many small operations continue to soak their corks even in the face of better overall cork quality. Finding the reason is as easy as answering the following question: Who tends to be on the bottom of the cork supply food chain? Not commercial wineries, which are large, repeat customers but the small mom and pop home winemaking retailer, who maybe only order one bag of 1,000 corks at a time (enough for about three barrels of wine), a few times a year. Since their home winemaker customers tend to buy corks in small quantities, the well-intentioned shopkeeper rips open the sealed bag from the cork factory and divvies them into their own plastic baggies. Even worse, some retailers just tip their corks loose into bulk bins for customers to paw through, selecting the exact number of corks they want. Since all of this breaking-down of the standard-sized 1,000-cork bag makes for dried-out, dusty and potentially contaminated corks, it’s no wonder that small-scale winemakers have historically doused their corks in a strong sulfite solution in an attempt to mitigate these potential threats! Luckily, these days stores and Websites that supply small-scale winemakers are understanding the importance of cork quality more and more. Most do their best to keep corks in the original suppliers’ bags or, if they must break down orders, to gas plastic bags with sulfur dioxide, which retards the growth of microbes. Similarly, retailers understand that they can’t keep last year’s corks around for this vintage’s clients and will destroy (or turn into decorative cork boards) inventory that has passed its expiration date. So, should you soak your corks or not before you use them? If you are fortunate enough to order your corks direct from the factory, in a sealed bag, you don’t need to, unless it helps you slip the cork into the bottle easier with your hand corker. Similarly, if you buy your corks from a winemaking supply store that you know has a lot of customers and a high turnover of their cork inventory, you probably don’t need to rinse or soak your corks either. If, however, you aren’t in either of the above camps and don’t know how long your corks have been exposed to the air, where they came from or how old they are, it might be a good idea — or at the least it’ll make you feel like you’re doing something to help. I think this is where most of our good-intentioned soaking of corks comes from. Since we know we may have to (at least in some situations) accept less-than-ideal corks, we feel that a quick dip in a 70 ppm sulfite solution spiked with 1 g/L of tartaric acid (one of the many sulfite cocktails I’ve seen in use) may at least rinse the dust away and retard some surface-dwelling bad guys. Unfortunately, the reality is that once a cork has dried out and a mold colony has invaded its nooks and crannies, there’s very little that a winemaker can do, whether working for a top of the line facility or simply making it work in their garage. Even a rigorous wash in a sulfite solution, or any other available sanitizing compound — no matter how strong — won’t be able to do much. Wash corks in water that isn’t sulfited and you may even increase the chance of infecting your corks by providing opportunistic microorganisms with a source of moisture. So what’s a small-scale winemaker to do? Make sure that you buy your corks from a reputable supplier with high turnover. Never take chances on old, dried out corks that could spoil your wine or cause your bottles to leak. Better yet, to ensure the best cork quality, go in with a group of friends or your local winemaking club and place “real winery” orders in multiples of 1,000 corks at a time in sealed bags. Dear Wine Wizard, A friend recommended microwaving corks in a bowl of water to sanitize them. Is this a better alternative to soaking them in sulfite solution? Simon Cole United Kingdom Wine Wizard replies: Corks seem to be on everyone’s mind as of late — it must be bottling time! As I think I’ve mentioned before in this column, it’s impossible to sterilize corks and it’s almost impossible to properly sanitize them. Corks are plugs of tree bark, after all. Mold and bacteria are held in check relatively well by cork manufacturers who use ozone, high pressure, sulfur dioxide and all manner of things to knock down the populations of microbial visitors. As I mention above, however, once the bag from the manufacturer is opened (as they are in most home winemaking supply stores) all bets are off as the protective sulfur dioxide dissipates, the corks dry out and mold and bacteria take their toll. This is why many home winemakers choose to attempt to sanitize corks before using them — we clean and sanitize the rest of our winemaking equipment, so we at least make an attempt at sanitizing our corks, right? Also, that little bit of moisture can sometimes help the corks slide better into the bottles since we don’t have the benefit of the pounds of pressure of commercial corking machines. But is microwaving corks the best way to do it? Since it’s impossible to sterilize corks with high heat (that would take a hospital-grade autoclave which a microwave would never accomplish) it’s quite possible that you might only be able to heat the corks to a warm internal temperature that might encourage, rather than discourage microbial growth. My advice is the same as my previous answer. Try to get unopened, fresh bags of corks and use them up among a group of friends or your winemaking club within a month or two.

Origin information: Wine Maker Magazine

The Chemistry of Post–bottling Sulfides in Wine

Un interesante artículo científico del enólogo y químico Alan Limmer sobre la evolución del vino según los diferentes tipos de tapones puede consultarse en The Chemistry of Post–bottling Sulfides in Wine

Hongos transgénicos contra el olor fúngico en el vino

Hongos transgénicos contra el olor fúngico en el vino

Un equipo de investigadores del Instituto de la Viña y el Vino de Ponferrada, adscrito a la Universidad de León, ha logrado desarrollar un hongo transgénico para sustituir a otro que causa la mayor parte de los aromas fúngicos que se pueden producir en el vino y que merman la valía del producto.

Sin embargo, el desarrollo de este organismo modificado genéricamente se encuentra con una importante dificultad legal. Y es que está prohibido el uso de organismos alterados por la mano del hombre para su aplicación en la alimentación humana.

Por eso, los científicos estudian ahora cómo evitar que este hongo permanezca en la botella, según informan desde Dicyt.

Juan José Rubio Coque, que forma parte del equipo de investigación de este Instituto leonés, explica que el desarrollo de este hongo transgénico consiste en un “diseño de microorganismos” que crecen en el corcho y sustituyen a los hongos causantes de los aromas fúngicos. Previamente a este paso, los científicos identificaron el gen que codifica la enzima responsable del mal olor.

Origen del problema
Antes de la extracción de la corteza del alcornoque o durante el proceso industrial de fabricación de los tapones de corcho, este producto puede adquirir sustancias de origen microbiano que causan en el vino olores desagradables. Los más importantes son producidos por cloroanisoles, que son compuestos volátiles generados por el hongo -en la mayoría de los casos el Trichoderma longibrachiatum- a partir de pesticidas, por lo que estos productos químicos son, en primera instancia, los causantes del problema.

El primer paso sería eliminar estos pesticidas. Pero, al contrario de lo que pueda parecer, no es tan sencillo combatir contra los cloroanisoles. “Están tan extendidos que suponen una forma de contaminación ambiental”, explica José Rubio Coque.

Por eso, los científicos se han planteado introducir mejoras biotecnológicas. Cuando logren encontrar hongos que carezcan del gen que activa la producción de tricloroanisol, los expertos plantearán la sustitución de los hongos actualmente comunes por otros que no causen olor fúngico. El paso final será la eliminación de estos hongos transgénicos de los tapones de las botellas, para que los organismos no intercedan en la cadena alimenticia humana.

Origen información: Mercados del Vino

La inversión en I+D en el sector europeo de la alimentación crece un 5,28%

La inversión en I+D en el sector europeo de la alimentación crece un 5,28%

Entre las 35 empresas comunitarias que más gastan en labores de investigación sólo hay dos españolas.

Pese a que la media general de inversión en I+D de las principales empresas europeas se redujo el 2,6% en 2009, la industria alimentaria comunitaria ha seguido una tendencia bien distinta.

Así, el sector de alimentación y bebidas de la Unión Europea (UE) invirtió el pasado año un total de 2.214,44 millones de euros en labores de investigación y desarrollo, lo que representa el 5,28% más que en el año anterior, según se refleja en el último cuadro de indicadores sobre la inversión industrial en I+D que la Comisión Europea ha hecho público recientemente.

A nivel mundial, esta partida aumentó el 2,51%, con una inversión total de 4.512,21 millones de euros, según recoge Alimarket.

En cuanto a los países europeos que más gastan en I+D en el sector alimentación, lidera la clasificación Reino Unido, con diez compañías incluidas entre las 35 primeras por nivel de inversión. Esta posición se entiende fácilmente teniendo en cuenta que Unilever, empresa británica, se sitúa de nuevo como la firma más comprometida, con 891 millones de euros en 2009, muy lejos de la segunda, que no es otra que la francesa Danone, con 206 millones de euros destinados a labores de investigación.

Entre las 35 primeras sólo se encuentran dos españolas: Ebro Puleva, con un volumen de inversión de 9,68 millones de euros y Pescanova, con 5,4 millones de euros. Aunque ambas han aumentado de forma considerable el gasto en investigación y desarrollo. La primera invirtió el pasado año el 16,4% más que en 2008 y, la segunda, ha destinado el 10,2% más a estas labores.

La Comisaria europea de Investigación, Innovación y Ciencia, Màire Geoghegan-Quinn, ha hecho hincapié en el hecho de que “las grandes empresas de la UE hayan mantenido en gran medida sus inversiones en I+D”, lo que, a su parecer, “demuestra que comprenden que la I+D es la clave para salir reforzados de la crisis”.

Por D. Sanjuán

Origen información: Mercados del Vino

Guía internacional para la compra de tapones de corcho para vinos tranquilos (diversos idiomas)

Guía internacional para la compra de tapones de corcho para vinos tranquilos

Código internacional de prácticas taponeras

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Guia para compra da rolhas

Código internacional das práticas rolheiras

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International guide for buying cork stoppers

International code of cork stopper manufacturing practices

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Guide internationale d'achat des bouchons en liège

Code international des pratiques bouchonnières

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Códice internazionale delle pratiche per la produzione dei tappi di sughero

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Internationaler codex zur herstellung von korken

How is cork made?

An incredibly versatile natural material, cork is harvested from living cork oak trees somewhat like wool is gathered from sheep. The trees are unharmed by the process, and they continue producing cork for an average of 150 years.

Background

Cork is composed of dead cells that accumulate on the outer surface of the cork oak tree. Because of its honeycomb-like structure, cork consists largely of empty space; its density (weight per unit volume) is one-fourth that of water. Unlike a honeycomb, however, cork consists of irregularly shaped and spaced cells having an average of 14 sides. With 625 million of these empty cells per cubic inch (40 million per cubic centimeter), cork is like many layers of microscopic Bubble Wrap, making it an effective cushioning material. Its low density makes cork useful in products like life preservers and buoys. The large amount of dead-air space makes cork an effective insulation material for both temperature and noise. Furthermore, it is fire retardant; flames will only char the surface, and no toxic fumes are generated. Cutting the surface of cork turns many of the microscopic cells into tiny suction cups, creating an effective non-slip surface. In addition to being flexible, cork is highly resilient. After being crushed under a pressure of 14,000 lbs/in2 (96,000 kPa), cork will regain 90% of its original size in 24 hours. Cork absorbs neither dust nor moisture, and it resists both rot and insects. Highly resistant to wear, it is used for polishing diamonds.

Among the many products made from cork are flooring materials (e.g., linoleum), shoe insoles, roofing panels, gaskets, safety helmet liners, bottle stoppers, dartboards, bulletin boards, and cores for golf balls and baseballs. Numerous artificial materials have been developed to substitute for cork in specific applications (e.g., a synthetic pea in a referee's whistle, foam insoles for shoes, or Styrofoam life preservers). However, no general substitute has been developed for cork that can be used in diverse applications.

History

Cork bottle stoppers have been found in Egyptian tombs dating back thousands of years. Ancient Greeks used cork to make fishing net floats, sandals, and bottle stoppers. Two thousand years ago, Romans widely used cork in variety of ways, including life jackets for fishermen. For hundreds of years, Mediterranean cottages have been built with cork roofs and floors to keep out summer heat and winter cold—and to provide a soft walking surface.

Glass bottles were invented in the fifteenth century, but their use did not become widespread until the seventeenth century. The popularity of cork as a stopper led to deliberate cultivation of cork trees, which prior to about 1760 had simply been harvested wherever they happened to grow. The revolutionary crown cap—a metal lid lined with a disk of natural cork commonly known as a bottle cap—was invented in 1892

A great deal of the cork harvest was wasted until around 1890, when a German company developed a process for adding a clay binder to cork particles and producing sheets of agglomerated (composite) cork for use as insulation. The following year, an American named John Smith developed a technique for producing pure-cork agglomeration out of waste material by subjecting cork particles to heat and pressure without adding any binder. The next major development occurred in 1909 when Charles McManus invented a type of agglomerated cork that could be used to line crown caps. Since then, many other techniques have been developed to produce cork compounds with a variety of properties and uses.

Raw Materials

The raw material for cork products is harvested from the cork oak tree (either the evergreen Quercus suber or the deciduous-Quercus occidentalis). The trees typically reach a height of 40-60 ft (12-18 m) and a trunk circumference of 6-10 ft (2-3 m). Virtually all of the world's commercial cork trees grow in the western Mediterranean region and the Iberian Peninsula. Portugal's cork forests are the most productive. Accounting for 30% of the existing trees, they produce half of the world's harvested cork.

A cork tree is ready for its first harvest when it is about 20 years old. The first harvest is of poor quality, and can only be used to make agglomerated cork products. Subsequent harvests occur at nine-year intervals, when the cork layer reaches a thickness of 1-2 in (2-5 cm). The harvest from a young tree yields about 35 lb (16 kg) of cork, while the yield for an older tree may be 500 lb (225 kg). Each tree has a productive life of about 150 years.

During the production of bottle stoppers, chemical baths are used to condition the corks. Among the more popular are a chlorinated lime bath followed by a neutralizing bath of oxalic acid, a hypochlorite bath neutralized by sodium oxalate, and a peroxide bath neutralized with citric acid.

Production of compound agglomerated cork involves adding a binder or adhesive agent to cork granules. Different binders are chosen, depending on the qualities desired in the ultimate product (e.g., flexibility, softness, resistance to wear). Among those frequently used are asphalt, rubber, gypsum, glue, and plastic.

The Manufacturing Process

Using a specially designed hatchet, the harvester slices through the cork layer on the trunk of the tree, taking care not to cut deep enough to damage the living portion of the trunk. Horizontal cuts are made at the base of the trunk and just below the lowest branches. A few vertical cuts separate the circumferential cork ring into sections of an appropriate size. Using the wedge-shaped handle of the hatchet, the harvester strips each panel of cork from the tree. On some large trees, cork is also stripped from the lower branches.
The cork planks are stacked outdoors and left to cure for a time ranging from a few weeks to six months. The fresh air, sun, and rain encourage chemical changes that improve the quality of the cork. By the end of the curing process, the planks have flattened out and lost about 20% of their original moisture content.
The planks are then treated with heat and water to remove dirt and water-soluble components like tannin, and to make the cork softer and more flexible. This process typically involves lowering stacks of cork planks into large copper vats filled with boiling water containing a fungicide. Heavy weights are placed on top of the cork to keep it submerged for 30-75 minutes.
When the planks are removed from the vat, a hoe-shaped knife is used to scrape off the poor-quality outer layer of cork, which amounts to about 2% of the volume of the plank but 20% of its weight. The planks are stacked in a dark cellar and allowed to dry and cure under controlled humidity for a few more weeks.
The cork planks are trimmed to a uniform, rectangular shape and are sorted by quality. The finest quality material will be used to make natural cork products like wine bottle stoppers. Poorer quality material will be ground and used to make composition or agglomerated cork.

Boffle corks

Cork slabs of the desired thickness are placed in a steam chamber for 20 minutes to soften them. The slabs are then cut into strips whose width corresponds to the intended length of the bottle stoppers. The strips are fed through a machine that punches hollow metal tubes through them, removing cylinders of cork.
Although some beverage bottlers want cylindrical corks, others want tapered ones. To achieve this shape, the cylinders are arranged on a slanted conveyor that carries them past a rapidly rotating circular knife. As they pass the blade, the corks are also revolving on the conveyor, so they are trimmed to a taper.
Both cylindrical and tapered corks are washed, bleached, and sterilized in large vats. Rotating wooden paddles continually push the corks down into first a washing solution and then a neutralizing solution.
After being dried in a large centrifugal dryer, the corks may be marked with an identifying label (with ink or a hot-metal stamp). Some are also coated with a sealant such as paraffin or silicone. Then, they are packed in airtight bags in quantities of 1,000 or 1,500; the air is removed from the bags and replaced with sulfur dioxide (SO2) to keep the corks sterile.

Agglomerated cork

Waste cork is passed through a machine that breaks it into small pieces. The pieces are washed and dried, and then sent through two successive grinders to further reduce the particle size. After another washing and drying process, the particles are screened for uniform size.
Pure agglomerated cork is formed by packing cork particles into a mold and covering it securely. Superheated steam (600° F or 315° C) is passed through the mold. Alternatively, the mold is baked at 500° F (260° C) for four to six hours. Either process binds the cork particles into a solid block by activating their natural resins.
Compound agglomerated, or composition, cork is made by uniformly coating the cork granules with a thin layer of an additional adhesive agent. The coated granules are pressed into a mold and slowly heated (the temperature varies, depending on the adhesive used). When removed from the mold and cooled, the blocks are stacked to allow air circulation and are allowed to season.
The agglomerated cork is cut for its intended use. For example, sheets may be cut from rectangular blocks. Or if a tubular mold was used, the resulting cork rod may be sliced into discs. A large, cylindrical block might by revolved against a knife blade to shave it into a long, continuous sheet that is rewound into a roll.

Cork waste generated during the manufacturing process is ground and used to make agglomerated cork products. Cork powder that is generated by the grinding process is collected and burned to help fuel the factory. Chemical components removed from cork during its processing can be recovered as useful byproducts and include tannin (used for curing leather), hard wax (used in products like paraffin, paint, and soap), resinous gum (helps vanish adhere to copper and aluminum), and phonic acid (used to make plastics and musk-scented toiletries).

Origin information: How is cork made?