Screwcaps for Wine. The Start of a Revolution 26 June 2002. Recent History. Clare Valley Winemakers End of 1999 results of new cork treatments trial prove disappointing. Frustrated winemakers look at alternatives.
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Screwcaps for Wine The Start of a Revolution 26 June 2002
Recent History Clare Valley Winemakers • End of 1999 results of new cork treatments trial prove disappointing. • Frustrated winemakers look at alternatives. • A group of like-minded Riesling producers decide to bottle all or part of 2000 vintage with screwcaps. • Resultant publicity stirs curiosity of New Zealand winemakers.
Recent History New Zealand Winemakers • Similar Frustrations with poor quality cork. • Marlborough Winemakers hold meeting February 2001 to consider alternatives to cork. • Long-skirted screwcaps identified as the most promising closure to replace cork. • Technical subcommittee formed to investigate systems and viability of screwcap closures.
Recent History NZ National Body Formed • Marlborough activity leads to great interest shown from all around the country. • Decided to form a national body to promote the use of screwcap closures. • New Zealand Screwcap Wine Seal Initiative formed. • Manual published and seminars held.
Role & Functions • Promote the use of Screwcaps. • Educate our members on the technical aspects of screwcaps usage. • Educate the wine trade, wine press and consumers about the benefits of using Screwcaps to seal wine.
Wine Tradition • For several centuries, since the use of glass bottles for packaging wine became common, the cylindrical cork seal has been the closure of choice. • Revolutionary, at the time. • Wine more easily transported. • Convenient size. • Benefits of bottle age apparent for the first time.
Cylindrical Stoppers Cork or (more recently) Synthetic • Compressed and inserted into the bottle neck.
Cylindrical Stoppers Cork or Synthetic • Compressed and inserted into the bottle neck. • Relies on the elasticity of the material to provide the seal between closure and glass. • Low pressure elastic seal, over the entire length of the closure.
Cylindrical Stoppers Problems: • Pressure changes in the bottle can cause movement and/or wine creep. • May permit gas permeability, and this may be extremely variable. • Compression of air into wine if insertion machinery faulty. • Absorption of taints.
Screwcap Wine Seals • Screwcap closures differ greatly from cylindrical stoppers in their mode of sealing. • The main difference is that they seal around the rim of the bottle, rather than along the internal surface of the the bottle neck.
Screwcap Wine Seals There are two major screwcap wine seals available in New Zealand currently: • Stelvin®, produced by Pechiney of France • Supervin, produced by Auscap of Australia. Other competing brands will soon be available, in particular GlobalCap from Europe.
Screwcap Wine Seals The current standard size for Screwcaps in New Zealand is 30 X 60.
Screwcap Construction The Roll on Tamper Evident (ROTE) closure, or Screwcap, consists of two parts: • Outer, made of malleable aluminium alloy rolled on to fit the bottle. • Liner, provides the seal between the closure and the bottle.
The Outer Four main functions: • Presents the liner in the correct position for sealing. • Moulds to the bottle and holds the liner in place against the bottle mouth with the required pressure. • Provides the thread to help the eventual removal of the cap. • Space for decoration.
The Liner The Liner is a polylaminate of three parts: • 80 micron layer of neutral PVDC film, which is in contact with the wine, and the bottle rim. • 19 micron layer of tin foil, which provides the gas barrier. • Wad (approx. 2mm) of expanded polyethylene, which provides the elastic resilience to maintain compression. • New generation liners much more reliable than in the past.
Screwcap Closures • Liner compressed onto surface of the bottle rim (120 kg) and held in place by aluminium Outer. • High pressure hermetic seal, capable of withstanding relatively large pressure and temperature increases. • Total gas barrier, perfect inclusion/exclusion.
Past Problems Leakage has been a problem, usually due to side impact at the top of the closure:
Past Problems • Leakage has been a problem, usually due to side impact at the top of the closure: • Now prevented by a process called “Redraw”. • Pressure block modified to “wrap” the outer much closer to the glass finish.
Screwcap Profiles Without Redraw With Redraw
Past Problems • Liner rupture. • Prevented by: • Accurate pressure control at sealing (120 kg) • New liner materials, as described earlier.
Experience • Screwcaps have been in commercial use for wine for over 30 years. • Accumulation of practical, commercial experience. • Several key research projects, particularly in Australia.
Research Results Eric, Leyland & Rankine (1976) “Stelvin” – Evaluation of a New Closure for Table Wines “The results of this investigation indicate that the metal closure with 358 wad performed well on the wines tested in comparison to cork and the other two wadding materials, justifying its use as a commercial closure for table wines.”
Research Results Rankine, Leyland & Strain (1980) Further Studies on Stelvin and related wine bottle closures “The results obtained in this study confirm the superiority of the Stelvin 358 and 323 closures over cork under the conditions used in the comparison.” “These results point to the suitability of certain of these closures as replacements for the traditional bark cork, where the wines stored under these conditions matured better than under cork.”
Research Results P. Godden et al (2001) Australian Journal of Grape and Wine Research. (AWRI) Wide-ranging and complex research project which tested 14 different closures. White wine only (Clare Valley Semillon) Published first results after 20 months. Trial is ongoing.
Research Results P. Godden et al (2001) Conclusions about Screwcaps (Analytical): 1. Lowest Reduction in Free and Total SO2. 2. Highest retained Free SO2. 3. Highest retained Ascorbic Acid. 4. Lowest incidence of Browning (OD420). • Least variation between bottles for all compositional variables.
Range of Brown Colour- 28 months after bottling OD420 0.14 au OD420 0.19 au From: P. Godden, Australian Wine Research Institute
Research Results P. Godden et al (2001) Conclusions about Screwcaps (Sensory): 6. Highest in Overall Fruit. 7. Lowest in Developed and Oxidised Characters. 8. Effectively Zero TCA.
Bottle Maturation Questions that typically arise amongst consumers are: • “But isn’t the cork needed for the wine to develop and age properly?” • “That’s OK for current consumption wines, but great wines need corks to age, don’t they?” • “The wine is a living thing, and it needs to breathe through the cork, doesn’t it?” • In every case, the answer is no.
Bottle Maturation J. Ribéreau-Gayon et al (1976) “Traité d’Oenologie – Sciences et Techniques du Vin” Vol.3 “…les quantités d’oxygène qui pénètrent normalement dans les bouteilles sont infimes sinon nulles. L’oxygène n’est pas l’agent du vieillissement normal en bouteille.”
Bottle Maturation J. Ribéreau-Gayon et al (1976) “Traité d’Oenologie – Sciences et Techniques du Vin” Vol.3 “…the quantities of oxygen that normally penetrate into the bottles are negligible if not zero. Oxygen is not the agent of normal bottle maturation.”
Bottle Maturation E. Peynaud (1984) “Knowing and Making Wine” “It is the opposite of oxidation, a process of reduction or asphyxia, by which wine develops in the bottle.”
Ethanol (fermentation) Acetaldehyde (barrel maturation) Bottle Maturation The reactions are reductive rather than oxidative. Reduction: Acetaldehyde as opposed to Oxidation: Ethanol
Bottle Maturation P. Ribéreau-Gayon et al (2000) “Handbook of Enology - Vol.2 The Chemistry of Wine Stabilization and Treatments” “When a wine ages in the bottle, the oxidation – reduction potential decreases regularly until it reaches a minimum value, depending on how well the bottle is sealed. Reactions that take place in bottled wine do not require oxygen.”
Bottle Maturation P. Ribéreau-Gayon et al (2000) “Handbook of Enology - Vol.2 The Chemistry of Wine Stabilization and Treatments” “During bottle aging, wines develop in a reducing environment, tending towards greater organoleptic quality than they initially possessed”
Bottle Maturation • The aging process which takes place in the bottle after sealing. • Long time frame, years rather than months. • Responsible for the development of bottle “bouquet”. • High quality wines benefit the most. • Arises from slow, reductive reactions, in the absence of oxygen.
Bottle Maturation • Screwcaps are the ideal closures to exclude oxygen from the bottle, and thereby promote the development of bottle bouquet. • Screwcaps are ideally suited to bottle maturation over a long time frame, not just for current consumption. • Screwcaps are guaranteed against failure for 10 years, but realistically can be expected to last at least 20 years.
Conclusion The Advantages of using Screwcaps to seal wine bottles may be summarised as follows: • Total absence of Taint • Superior retention of wine quality characteristics. • Ability to allow further bottle maturation. • Convenience of removal and re-sealing.
References • Ribéreau-Gayon, J., E. Peynaud, P. Ribéreau-Gayon and P. Sudraud (1976) “Traité d’œnologie : Sciences et Techiques du Vin. Tome 3 – Vinifications. Transformations du vin.” Pp.661-668. Dunod. • Eric, B., D.A. Leyland and B.C. Rankine (1976) “Stelvin” – Evaluation of a new closure for table wines. Aust. Grapegrower & Winemaker, No.148, April 1976. • Rankine, B.C., D.A. Leyland and J.J.G. Strain (1980) Further studies on Stelvin and related wine bottle closures, Aust. Grapegrower & Winemaker, No.196, April 1980. • Peynaud, E. (1984) “Knowing and Making Wine” Pp.253-254. Wiley • Ribéreau-Gayon, P., Y. Glories, A. Maujean and D. Dubourdieu (2000) “Handbook of Enology Vol.2 The Chemistry of Wine.Stabilization and Treatments.” Pp.368-372. Wiley • Godden, P., L. Francis, J. Field, M. Gishen, A. Coulter, P. Valente, P. Hoj and E. Robinson (2001) Wine bottle closures: physical characteristics and effect on composition and sensory properties of a Semillon wine. 1. Performance up to 20 months post-bottling. Australian Journal of Grape and Wine Research. 7, 64-105.