Spotlight on non alcohol wines. Part 2 – Australia

Posted on August 12, 2021 by The Wine Commander

Australian Vintages McGuigan Zero range now makes up 10 per cent of sales of the entire McGuigan portfolio.

 In part 1 of this topic we looked at no and non alcoholic wines progression in NZ. In this blog we examine theproduers and methods of producing no and low alcohol wines in Australia. 

It was late in 2018 when the idea of entering the alcohol-free wine category was raised at Australian Vintage after experimenting for more than 20 years.  In 2019 McGuigan Zero was launched comprising a Sauvignon Blanc, Chardonnay, Shiraz, Rosé and Sparkling. And the response by consumers has meant the McGuigan Zero range now makes up 10 per cent of sales of the entire McGuigan portfolio.

“The popularity of Zero has completely exceeded all our expectations,” remarks Australian Vintage’s chief winemaker Jamie Saint. “The popularity just keeps growing and now our challenge is to make sure we have enough stock to keep supplying  our customers.”

The growth has been phenomenal in Australia. The Endeavour Group recently reported that sales of non-alcoholic drinks in its BWS and Dan Murphy’s outlets increased 83% in the month of June 2021 compared with July 2020, with beer followed by wine the best-sellers in the category.

This demand inspired the recent opening of ‘Sans Drinks’, Australia’s first alcohol-free bottle shop in the suburb of Freshwater, located on Sydney’s northern beaches. Another trail blazer is ‘Brunswick Aces’ non-alcoholic bar in the Melbourne suburb of Brunswick East. It boasts more than 100 non alcoholic beers, wines and cocktails.

In the past a lot of the no and low alcohol products have been pretty average and has scared away consumers who thought, ‘Oh, that was terrible, I’m not going back there’.

 Generally, the wine industry has been “lagging behind” in responding to the growth in this segment of the market, largely due to the capital costs involved in producing low and no alcohol wines.

Australian Vintage chief winemaker Jamie Saint with the company’s spinning cone column.

Innovation ‘a problem’

 Smaller players haven’t been able to afford the technology to produce so   innovation is limited to things like piquette, where grape skins are rehydrated, fermented out, then bottled. But that’s not wine — that’s a grape-based beverage.

In Australia, labelling regulations state that a regular wine is anything that contains 4.5% ABV and above; between 0.5-1.15% ABV is regarded as a low alcohol wine, while anything less than 0.5% ABV can be labelled non-alcoholic or alcohol free wine. These regulations vary in overseas markets.

There have been two techniques favoured by most wineries in Australia and around the world to remove alcohol: reverse osmosis and spinning cone column.

The spinning cone column is probably the industry standard for de- alcoholisation down to 0.5% or 0.05% ABV. You generally get a better sensory result using those products. It’s gentler and it’s done at a cooler temperature.”

A global leader in spinning cone column technology is Australian company Flavourtech, based in Griffith, New South Wales, which specialises in the manufacture of technology designed to recover, extract and evaporate aromas for food, beverage and pharmaceutical products. But, one day, Flavourtech co-founder Andrew Craig was asked whether the spinning cone column could also be used to remove alcohol from wine.

“It did work and it worked really well,” remarks Flavourtech’s global sales manager Paul Ahn. “[Craig] was standing next to the condenser at the time and could smell the lovely varietal aromas being extracted. And, so, he decided he should look into this aroma aspect of the spinning cone column as well.”

Now this is interesting.

While a few refinements to the technology have been carried out since, the fundamentals remain the same.  The spinning cone column is a multi-stage distillation process that uses steam to strip, in this case, wine of alcohol.  Inside its stainless steel body lies a central rotating shaft and a number of alternating stationary and spinning cones attached to either the wall of the column or the shaft. Wine is fed into the top of column and onto the first stationary cone. It then falls down the cone by gravity and onto the spinning cone directly underneath whereby it is flung upwards and outwards by the centrifugal forces of the spinning cone. The wine then hits the wall of the spinning cone column and falls onto another stationary cone directly underneath, and the process continues down the column.

At the same time, steam is introduced at the bottom of the spinning cone and flows up, carrying with it the volatiles, namely the aroma compounds and alcohol, from the wine.  These volatiles are then condensed and stored while the de-aromatised and de-alcoholised wine exits from the bottom of the column.  The aroma compounds can subsequently be added back to the wine.

 The temperature of the column and steam are kept low, between 30-45°C. Ahn explains that wine is in the column for less than 30 seconds and this, combined with the low operating temperature, ensures the process has minimal or no impact on wine.

You can see why producing low and no alcohol wines has been a barrier to uptake by smaller producers.  The price starts at just over $400,000.

 It is the application of a spinning cone column that has resulted in McGuigan Zero.

Australian Vintage’s Tempus Two Lighten Up range includes a prosecco, rosé and Pinot Noir which have an ABV of 6.8%.

Australian Vintage’s Tempus Two Lighten Up range includes a prosecco, rosé and Pinot Noir which have an ABV of 6.8%.

Understanding changes and effects

In June this year, Australian Vintage launched a new lower alcohol range of wines under its Tempus Two label called Lighten Up. With an ABV of 6.8%, the range includes a Prosecco, Rosé and Pinot Noir and, like the McGuigan Zero, were made using the same spinning cone column technology.

McGuigan has now grown to become the number one selling alcohol-free wine in Australia, New Zealand and the United Kingdom.

VAF Memstar is another Australian-based company with a history in the treatment of wine to reduce alcohol using a ethanol reduction process.

Casella Family Brands has applied reverse osmosis in the production of its lower-in-alcohol [yellow tail] Pure Bright wines, which was released in June and trailed since 2015. Comprising a Pinot Noir and Sparkling with an ABV of 10.8% and 8.5%, respectively, the wines were also released onto the US and Canadian market earlier in 2021.

 “The production of [yellow tail] Pure Bright started towards the end of 2019. It was developed to provide a lighter, more refreshing alternative with fewer calories and less alcohol when compared to our core range, which meets consumer demands while also attracting a younger demographic”, explained David Joeky of Casella.

(Left) The [yellow tail] Pure Bright range is currently available in a sparkling and Pinot Noir. (Right) Casella Family Brands winemaker David Joeky.

It is also accepted that regular wine consumers have increased their frequency of wine consumption at home due to the COVID-19 pandemic, a trend that is expected to continue for the next few years beyond the pandemic.

 “Our vines are selected and pruned to maximise the leaf protection from the sun, protecting the grapes and slowing their development whilst maintaining fruit flavour and intensity. The grapes are picked earlier, while they have a lower natural sugar content, converting to lower alcohol in the wine. We also implement night harvest to keep the grapes cool and crisp in order to maximise the aroma and flavour” says Joeky.

Joeky says that while white varieties and light-bodied reds have responded better to the alcohol targets, reds have proved trickier to achieve the desired alcohol level without losing balance in the wine and the tannins increasing.

“Some products work better than others. Sparkling wines, whites, they’re probably easier than the reds. Reds present a formidable challenge to figure out how to replicate wine. he said”

“Alcohol is one of the important balancing components in wine. If you just take the alcohol out, it’s like cutting off one leg of a chair. If you think of the legs of a chair as alcohol, tannin, acid and sugar, if you take out just one of them, then you unbalance that wine. And that’s why, consistently, most of the tastings of zero or very low alcohol wines have not been particularly satisfying, because people imagine that you can take a wine, a good Barossa Shiraz or Coonawarra Cabernet, take out the alcohol and then somehow it remains like that. It doesn’t work that way, especially with red.”

Diagrams explaining how VAF Memstar’s technology removes alcohol: (left) this highly magnified schematic cross-section of a wall of a tubular membrane shows the migration of alcohol through microscopic pores, from a high concentration stream to a lower concentration stream on the inside of the tube; this process is known as evaporative perstraction and (right) alcohol reduction by reverse osmosis and evaporative perstraction where water is used to strip alcohol from the permeate stream of reverse osmosis processed wine. This permeate is then recombined with the wine from which it was extracted, thus lowering the alcohol of the blend.

Left: Flavourtech’s Spinning Cone Column is a multi-stage distillation column that employs steam as the stripping medium. It consists of a stainless steel body, central rotating shaft and  cones.

I hope you found this series interesting. I learnt alot from my research. But I am off now to drink a nice 15%  Barossa red. Care to join me?

Thanks to Sonya Logan in Grapegrower & Winemaker magazine. Article edited.
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Spotlight on non alcoholic wines. Part 1 – NZ

Posted on August 11, 2021 by The Wine Commander

 Above: John Forest from Forest wines in Marlborough, NZ with The Doctors range of wines.

You may not like to drink them but the fact is there is a growing demand for no and low alcohol wine around the world. 18 wine companies in NZ for instance, formed the  ‘New Zealand Lighter Wines’ initiative which has led to the release of a range of initially low and more recently no alcohol wines called NOLO wines for short.  

 New Zealand wine producer John Forrest, became a NOLO pioneer in 2006.  “I had zero interest in lower alcohol wine up until 2006 because, quite frankly, I quite enjoyed a big 14.5-15% Aussie Shiraz and still do. But, because I’m a Riesling-file, and I didn’t have a Kabinett style Riesling in our portfolio I made one”.

The Kabinett-style Riesling was bottled under its own label called The Doctors’ and launched at a tasting in Christchurch in September 2006. “Everybody commented that it was a nice Riesling, but they loved the idea of good wine with less alcohol. I thought if I could make a lower alcohol, high quality Marlborough Sauvignon Blanc typical of its style, you would be onto a sure winner, given that Sauvignon Blanc was the biggest volume and biggest value white wine in the world at the time. But in the first two years I made “some pretty average wine samples”.

Giesen’s Ara Zero Marlborough Sauvignon Blanc, which was launched in mid-2020.

Turning attention to the vineyard

An abstract from a research article out of Germany’s Geisenheim University described some success by reducing alcohol levels via leaf removal.

For two or three years he selectively removed leaves according to different timings and the number and position in the canopy. He found that a certain set of leaves at a certain time clearly slowed the rate of sugar, but when you tasted the juice, it tasted ripe.

Secondly, he changed the shoot positions in the canopy structure so that the leaves he wanted to trim off were above the top of the trellis posts.

The first Sauvignon Blanc under The Doctors’ label was released in 2009 at 9.5% alcohol and three years later the 2012 vintage picked up the wine’s first gold medal. Success followed with UK supermarket chain Waitress, taking a contract for 40,000 cases a year and then local viticultural consultant David Jordan came knocking. Jordan was aiming to make the New Zealand wine industry the international leader in the production of premium lower-in-alcohol wines.

David Jordan, program manager for New Zealand’s Lighter Wines initiative.
 Forrest Wines would become one of 18 New Zealand wine companies that contributed either cash or in-kind support to the research and development that became known as NZ Lighter Wines.
Beginning in 2014, it was led by New Zealand Winegrowers, with the support from the participating wineries supplemented by industry levy funding and the NZ Government, bringing the total funding pool to $15 million (AUD) in dollar terms. The largest research initiative ever undertaken by the New Zealand wine industry. Its challenge was to solve how to naturally lower the alcohol content without compromising the quality, flavour and style of wine.

“We wanted to hold true to what New Zealand wines are internationally renowned for: that they be vibrant and flavoursome, still refreshing and have all the quality attributes of the wines that has enabled us to have an export profile and sell significant volumes which are now achieving NZ$2 billion worth of export earnings around the world,”  Jordan explained.

“We wanted to better understand the role of alcohol as you come down the scale to less than 10%. Model Sauvignon Blanc wines were developed to understand exactly what aspects of the sensory experience were affected by reductions in alcohol. A reduction in alcohol from 12.2% to 9.5% increased the perception of acid and conversely decreased the perception of sweetness, bitterness, full-bodiedness, smoothness and palate length” he said.

 They found the aromas and flavours better than at a higher alcohol level   and subsequent work revealed that some of the more tropical flavours that Sauvignon Blanc is known for, present better at a lower alcohol.

Various techniques were trialled for their ability to delay sugar accumulation and impact on other wine parameters: short periods of deficit irrigation at key vine growth stages; fertiliser treatments; reducing canopy size through shoot thinning or leaf removal; and clones that were naturally lower in acidal selection.

“Technically, what we’re talking about is delaying ripening so you can pick with the same flavours, same acid but at a lower sugar, in combination with the role of clones,” Jordan says. “

Investigating winery manipulations 

It gets a bit technical here but stay with me please!

Winery manipulations were also investigated as part of the Lighter Wines initiative: the influence of skin contact to substitute the loss of texture, body and heat in reduced-alcohol wines; whether there was an optimal fermentation temperature to minimise the ethanol produced by yeast while maximising wine body and aromas in early harvest grapes; the effectiveness of different inoculation methods in reducing the conversion of sugar to ethanol in producing lower alcohol wines; and whether non-Saccharomyces yeast species could be used early in ferments to reduce the amount of sugar available to S. cerevisiase to ferment; and the role of oxygen during fermentation in reducing ethanol.(I hope you are still with me!)

Because the Lighter Wines initiative was based around producing lower alcohol wines naturally, this meant the lowest limit that could be achieved in wines like Sauvignon Blanc was 9-9.5%.

“It’s very difficult to have wines of all the appealing character, aroma and flavour of Sauvignon Blanc or Pinot Gris if you go below that. If you’re down to near 0%, you’ve transformed the beverage immensely and  you’ve got an even more significant challenge to actually get a wine to look wine-like,” he explains.

But now an increasing number of lower and zero alcohol products have hit the shelves. A number of them have wines at the mid strength level of 5-7%. with some down at zero.

In 2018, Giesen released a Marlborough Sauvignon Blanc and Pinot Gris at 9% alcohol under the label Pure Light. In early 2020, the company also released the Giesen 0% Sauvignon Blanc, with stocks in New Zealand and Australia selling out shortly after release. Then in mid 2020, Giesen released its Ara Zero Marlborough Sauvignon Blanc.

Giesen’s 0% Marlborough Sauvignon Blanc.

Thanks to Sonya Logan in Grapegrower & Winemaker magazine. Article edited.

 

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Grange tasting

Posted on July 1, 2021 by The Wine Commander

We were very privileged indeed to have Peter Gago, the Chief Winemaker at Penfold’s join seven of us for a unique tasting of Grange Hermitage at Melbourne’s Kelvin Club.

The entry was that each attendee bring a bottle of Grange from their cellar. After all, many of us hoard Grange but never seem to find the opportunity, courage or occasion to open it!

wine

Peter very kindly opened the batting with a special bottling of 2012 Champagne Thienot X Blanc de Blanc Grand Cru. Not being a champagne drinker, this wine blew me away. I frankly never knew champagne could be so delightful. Pale yellow with peach aromas with flavours of peach, apricot and grapefruit. Long with crisp acidity, great texture and and flavour. 19.5/20. $280.00. No auction price available.

We then settled in to work our way through eight bottles of Grange ranging from 1969 to 2016. Peter explained that his policy is always drink and serve wine from the oldest to the youngest.

He reminded us to always stand older vintages upright 24 hours before opening to allow sediment to settle at the bottom of the bottle. Extract the cork carefully and slowly decant the wine into a clean jug in a continuous stream ensuring the sediment is not disturbed. He recommends double decanting by rinsing the original bottle out with clean water to dispose of the sediment, hold the bottle upright to drain any surplus water and carefully re-pour the jug back into the original bottle. Re- cork and keep your fingers crossed.

Sterling Wine auction last sales range follow the assessments. 

1969 Grange Hermitage. A very wet growing season followed by a mild wet vintage. 12.5% in a 1 pint 6 fl oz bottle. Faded and past its best. Peter agreed with this. 12/20. $1200-$1499.

1983 Grange Hermitage. Ullage was to lower shoulder on this bottle which found it slightly oxidised and Peter commented that it would not make it at the bi-annual Penfold’s top up clinic. Whilst past it was still sweet on the palate. In good condition it would have the hall marks of chocolate, blackberry, hazelnut and and fine lacy textures. You may recall the dry northerly winds which led to the Ash Wednesday bush fires followed by February rains and March flooding. This bottle 15/20. In good condition 18.5/20. Peter says drink to 2040. It is recommended that you always try a wine in the mid of the drinking maximum range he says. $612-$1066.

1989 Grange Hermitage. Nose slightly closed but showed fresh dark chocolate, cherries, plum. Was sweet but soft with persistent acidity. Beautiful despite a burst of very hot weather in February that shrivelled the grapes, followed by heavy rains which made for a difficult vintage. 18/20. Drink now to 2030. ( Note the last vintage which has Grange Hermitage on the label. Future vintages simply say Grange). $545-$790.

1996 Grange.  A Cracker. Bright and elegant. Blueberry and blackberry fruits with generous dark cherries. Rich, with fine firm tannins – even apricots. Rated one of the best vintages in the 90’s.  Hot summer and damp March conditions. 19/20. Drink window to 2050. $670-$900.

1998 Grange. Opened slightly corked and was dull and sappy. Disappointed as this year is rated an exceptional vintage. Peter explained an early mild growing season followed by very hot dry weather laced with plenty of dam water. Should have been rich and full bodied showing all the classic fruits a Grange should have. Dark plum, mulberry, blackberry, liquorice, chocolate and black cherry. This bottle 14/20. Peter 19.5/20. Drink now to 2055. $670-$900.

2005 Grange. Was slightly closed and oxidised but underneath wow! Deep colour, long rich fruit and nicely balanced through the spectrum. Not a typical Grange said Peter but still developing. 18/20. Drink 2028 to 2050. (opposite is the 1969 bottle). $520-$760.

2008 Grange. Youthful and exuberant with cassis, bitter chocolate,  violet and liquorice overtones. Chewy and grippy tannins. Great power and density. Apparently a difficult, remarkable year marked by the longest heatwave ever recorded in South Australia. A run of 15 days above 35 degrees. An outstanding result and one of the great Penfold vintages.  19.5/20. Drink 2025 to 2060. $625-$760.

2016 Grange. What a way to finish. Easy to describe. Gorgeously  seductive with dark cherry, blackberry, dried plum fruits, rich dark chocolate with ripe tannins. long with density and power. Everything in harmony. The weather conditions allowed the Barossa Shiraz (97%) and Coonawarra Cabernet (3%) to to ripen perfectly. Drinking the latest release gave us an insight to the beginning of a life that will span 2030 to 2070. Remember if you live that long good luck but remember at the end of the day it is a bottle of wine that requires you to drink it and not leave it to the grand kids. 19.5/20. Drink 2030 to 2070. $660-$740.

Summary

While a couple of the bottles bought along had wine faults due to storage, heat, corkage or cellaring, it was interesting to see how this affected the complexity of the wine. To have Peter Gago with us for four hours to listen to his world wide travel experiences and share his vast knowledge was  to behold. Thank you.

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Penfolds Masterclass – the real review

Posted on June 9, 2021 by The Wine Commander

You may recall I previously reviewed the recent releases of the Penfold’s collection in 2019 in this blog. The 2021, ‘101 Masterclass’ was a slick affair held in May. It was evident at the masterclass that the domestic marketing of Treasury Estates has gone up a notch or two. Probably due to the China impact.
Generous pours, non stop hors d’oeuvres, an informative colourful 20 page brochure, (no ‘Rewards of Patience’ though) and hosted by Jamie Sach, Penfold’s Global Ambassador. The 65 attendees were treated to nine of the recent releases starting with 2021 Koonunga Hill Autumn Riesling and 2018 Max’s Chardonnay.

2020 Koonunga Hill Autumn Riesling
From Eden Valley it is highly aromatic, spicy and quite zingy and with just 3-4 grams of sugar it finished beautifully on the palate. Off dry. $25.00. 16/20.

2018 Max’s Chardonnay
A complex Chardonnay from the Adelaide Hills. The range is a tribute to Max Schubert but this wine was over oaked for my palate.Underneath was rich lemon sneaking onto the palate.
$35.00.14/20

2019 Bin 311 Chardonnay
This wine sits behind the flagship Yattarna and is known as the ‘baby Yattarna’. The first Bin 311 vintage was in 2006. This vintage comes from 3 of the Penfold’s best cool climate Chardonnay regions of Tasmania, Adelaide Hills and Tumbarumba. Balanced mouth watering acidity with nice finish of citrus stone fruits. Will continue to mature over 5 years added by a screw cap. BUY. $50.00. 17.5/20.

2018 Bin 23 Pinot Noir
From parcels sourced from Tasmania, Adelaide hills and Henty. This was light/medium in colour, light bodied, rose petals, hints of strawberries and soft finish throughout the palate. A very delicate style for those who like a softer rather than full bodied pinot. $50.00. 17.5/20.

2017 Cellar Reserve Tempranillo
Tempranillo is a variety of black grapes and mainly used to make full bodied reds. This ‘noble grape of Spain’ is from McLaren Vale. I found the nose quite closed with dark lifted cherries and strawberries coming through and nicely balanced on the finish. I was reminded by the Chair to vigorously decanter young wines to release the aromatics something which I preach. Also for older wines the shorter the breathing the better, as oxygen is the enemy of old wines and will escalate oxidation. $85.00. 17/20.

“Numerous questions were asked and the answers were very informative in response. I asked about the pricing structure of Penfold’s wines and the continued increase in price each year. That the prices were now getting beyond long and loyal buyers who were now seeking quality value under $30. I pointed out that not so many years ago Bin 389 could be bought for under $50 and Grange at $250. The answer lies in the hands of accountants we were told.”

2018 Bin 28 Kalimna Shiraz
This work horse was first made in 1959 and is the oldest wine in the Bin range. It was the highlight of the night for me delivering on price and quality. Now stand by as the grapes were blended from parcels from Barossa, McLaren Vale, Padthaway, Wrattonbully, Fleurieu, Robe, Mt Lofty, Adelaide Hills and Langhorne Creek! Wow what a massive undertaking. Dark deep colour, it was big, bold and robust showing cedar, peppermint, chocolate, raspberries and hints of spice. Wonderful full mouth hit. Cellar for up to 15 years if you dare!  BUY.$50.00. 19.5/20. Cheaper if you hunt around the liquor chains.

2017 Bin 389 Cabernet Shiraz
Another ripper blended from 6 regions. Touted as the ‘Baby Grange’ it was first made by Max Schubert in 1960. Bin 389 matures in the previous vintages of Grange barrels. It is also listed as Australia’s no 1 most collected wine by Wine Ark. Big and bold it does not hold back. Loaded with cherries, chocolate, blackberries, spice and mint. Has a delightful balance of sweetness (Cabernet Sauvignon) and savoury (shiraz). It leaps out of the glass and we were told it will be at it’s peak in a band of 15-20 years. BUY. $100.00. 19.5/20. Hunt around for price. Pity about the continuing price rises!

2017 St Henri Shiraz
You might classify this as a stylish, old fashioned aristocratic wine made in the same mould as previous vintages. Deep black brooding colour before you are hit with purity of fruit laced with chocolate, blackberries, cherries and black olives. Long on the palate with a hint of mint on the front of the tongue.
At the moment it is certainly stylish and seductive but ideally needs a band of 10- 30 years. I will hop into it much, much sooner than that. BUY. $135.00 19.5/20. Once again check the internet for a better price.

Grandfather Rare Tawny Port
Comes in a gift box. 14 year old barrels worked in the solera maturation method. There was raisin, fruitcake and liquorice on the palate but I think spoilt by the high level of alcohol over powering on the nose. Nevertheless rich, powerful and nutty but that alcohol over rides this wine. $100.00. 16/20

Summary.
There is no doubt that this Penfold’s release is a class act particularly with the BUY recommendations indicated.  Top of the list and best value is the 2018 Bin 28 Shiraz followed by the 2019 Bin 311 Chardonnay for white wine lovers. If you can afford the others go for it but I suggest not, if you are approaching your 80th year as the wine will outlive you. Refer to the 2019 review in Posts.

Add your comments below.

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The influence of different screw caps on wine quality

Posted on May 18, 2021 by The Wine Commander

I came across this interesting article which is quite technical but may explain and clarify screw tops and its effect on bottle ageing. Now I do warn you to stay with it as it is complicated in its narrative.

I acknowledge the academic author Volker Schneider. I have edited the story the best I can without losing its context.

Summary
Screw caps differ in the oxygen barrier effect of their sealing inserts. Too much oxygen promotes oxidative ageing, too little oxygen promotes reductive ageing. Reductive ageing under hermetically sealing bottle closures is due to the formation of increased levels of volatile sulphur compounds, in particular thiols and H2S, whose odour causes reductive taints. Their prevention by the addition of copper salts before bottling is commonly opposed due to a variety of concerns. As an alternative, a functionalised liner for screw caps has been developed. It traps the thiols responsible for the occurrence of post-bottling reduction flavour and at the same time protects the fruity varietal aromas from oxidative ageing through its perfect oxygen barrier effect.

Introduction

Fruity white wines develop different sensory expressions of ageing. The best known of these is typical ageing, which is intensified by oxygen uptake via the bottle closure. Conversely, it is largely prevented by the widespread use of screw caps, in some cases with hermetically sealing inserts. However, such closure systems promote the so-called reductive ageing through the formation of reductive taints in the bottle. The development of a functionalised liner for screw caps opens up a way out of this dilemma.

From the moment a wine is bottled with different closures, the emergence of different wines from the same initial wine begins. In white wines, essentially four different sensory expressions of maturation and ageing develop:

  • Typical or oxidative ageing,
  • Atypical ageing (ATA),
  • Petrol flavour,
  • Reductive ageing.

Without any doubt, every white wine is subject to ageing. The only question is which of the above-mentioned types of ageing it is and how quickly it develops. In most wines, the bottle closure, and particularly its oxygen permeability, plays a prominent role.

 Different chemical reactions and odour-active compounds are responsible for the formation of the various forms of ageing. Two of them are predetermined by viticultural factors. Petrol flavour, for example, occurs almost exclusively in Riesling wines obtained from physiologically ripe grapes grown under hot-climate conditions, whilst the development of atypical ageing is observed exclusively in wines obtained from stressed fruit. The occurrence of these two very specific types of ageing is not related to the availability of oxygen. Consequently, it is not influenced by the oxygen permeability (OTR) of the bottle closure.

Regardless of this, the development of petrol flavour is significantly increased with screw caps because, in contrast to internally sealing closures such as corks, these have little material that could absorb the compound responsible for petrol flavour (TDN).

Typical or oxidative ageing

The situation is completely different with oxidative ageing. It has always been known and is, globally speaking, the most common sensory expression of white wine ageing. It is mainly due to the oxygen ingress through the bottle closure. In this process, odour-active compounds are formed under the influence of oxygen, of which methional, benzaldehyde, 2-phenylacetaldehyde, 3-methylbutanal and furfural are the most important ones and are considered indicator substances. They are higher aldehydes formed by oxidation of their corresponding alcohols. Their aroma notes of nuts, dry herbs, honey, cooked vegetables and boiled potatoes increasingly mask the fruity varietal aroma and cause a distinct madeirized aroma in extreme cases.

In contrast to the well-known acetaldehyde, which in its free form elicits its typical smell reminiscent of bruised apples and sherry and which can be bound by sulphur dioxide, these higher aldehydes barely react with SO2. Therefore, their formation cannot be effectively prevented by bottling with increased levels of free SO2. The reactions that lead to their formation are largely irreversible. They are controlled by oxygen supply and significantly accelerated by warm bottle storage.

Screw caps counteract oxidative ageing because they protect the bottled wine relatively well or even hermetically from absorbing atmospheric oxygen. This is one of the reasons for their almost universal acceptance in some countries. On the other hand, the assumption that the well-sealing screw caps protect the wine against any kind of adverse ageing is wrong.

Screw caps as an answer to oxidative ageing

In oxygen-sensitive white wines, differences in oxygen uptake of more than 5 mg/L O2can be discriminated by sensory means. This led to the initial assumption that the ideal closure for such wines would seal hermetically and prevent any oxygen ingress in order to preserve the fruity primary aromas for as long as possible. Since screw caps fulfil this requirement better than most other closures, there was initially nothing against their widespread introduction. This was especially the case when, a few months after bottling, the oxygen dissolved in the wine and the oxygen trapped in the bottle headspace has been completely bound and consumed by the wine, the closure takes control of oxidative ageing. With increasing bottle storage, the influence of the bottle closure comes more and more to the fore.

Significance of the sealing insert in the screw cap

Contrary to popular belief, however, screw caps are not a uniform type of closure, but are distinguished from one another by different sealing systems with different oxygen barrier effects.

Each screw cap consists of an outer aluminium cylinder and a single or multi-layer sealing insert. The outer cylinder fixes the insert in the correct position and presses it onto the bottle rim with the required pressure. The sealing insert provides the seal between the product and the closure, seals the bottle and prevents the diffusion of gases and liquids. It determines the tightness and functional quality of the screw cap. Thanks to their specific characteristics, the inconspicuous sealing inserts are the central element of screw caps and their functional end. In other words: Screw caps are as good as their sealing inserts. The latter are produced by specialised companies. The multitude of screw cap manufacturers is supplied by only a few manufacturers of sealing inserts.

Originally, the sealing insert consisted only of simple elastomers such as PVC or PE, which were injected into the aluminium cylinder. In the wine business, such inserts are mainly found in the short-skirted MCA or roll-on pilfer proof screw caps, which are preferably used in the segment of simple and inexpensive wines.

The gold standard for screw caps is now considered to be the long-skirted (60 x 30 mm) variants such as “Stellvin” or “Longcap”, which require a BVS bottle neck finish. Instead of injected elastomers, multi-layer sealing liners are predominantly used in these closures. Two main variants of such sealing liners are known (Figure 1):

Figure 1: Structure of common liners used for screw caps.fig1

Reductive ageing

At the turn of the millennium, when the hermetically sealing screw cap with a tin-saran liner was introduced, Australia’s and New Zealand’s wine industries took a pioneering role. One of their reasons was the pursuit of better preservation of the fruity varietal aroma of white wines under absolute oxygen exclusion. After a short delay, the wine industry in several European countries also adopted this logic.

The initial euphoria ‘Down Under’ soon gave way to more sober reflection when a greater tendency of the wines to developing aromas described as reductive or sulphurous was demonstrated under conditions of absolute air exclusion such as under the tin-saran lined screw caps.

The oxygen supply through the selected bottle closure determines whether the ageing of the wine is driven more in the oxidative or more in the reductive direction.

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