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New World Wine Maker Blog - Technical Articles

Grapevine Shoot Chips: A Novel Alternative to Oak Chips in Winemaking

The use of oak barrels in wine fermentation and aging increases wine aromatic complexity and improves overall quality. Despite a higher price tag, this technique is often used for red and some white wine aging. Due to higher costs, and other factors, many have sought alternatives that can produce a very similar style/quality wine at a fraction of the price. Most of you are already familiar with the use of oak chips in wine.  Oak chips are typically made from wood already utilized for wine barrels, and undergo similar toasting treatments to provide the aromas, flavors, and aging characteristics desired. Because of the increased surface area available by the small-sized chips, winemakers don’t need to use very many oak chips compared to the size of the barrel that would be needed to achieve comparable results.

Another way to impart oak flavors into wine, which isn’t as common but has been studied a bit in the literature, is oak extract application on grapes or grape vines. While studies have shown this sort of treatment may produce similar aromatic and sensory characteristics in the finished wine as a wood-aged treatment would, it’s likely just a way to get a “flavor now!” response and not a functional aging ability.

Of course, there are many other oak alternatives utilized in commercial especially home winemaking, but I won’t go into that now.

One new study, currently available online and to be published in print in October 2018 in the journal Food Chemistry, aimed to add one more potential oak alternative to the winemakers’ arsenal that I wasn’t expecting: grapevine shoots. Partially a response to growing demand for oak barrel alternatives, and partially a response to the amount of physical waste generated after the grape harvest, a team of Spanish researchers aimed to evaluate the use of grapevine shoot “chips” (toasted) as an alternative to oak chips in winemaking …

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50 SHADES OF ROSÉ

Oh my…it’s so big….the growth of rosé wine popularity that is.

rosé
ˈrəʊzeɪ/
noun

any light pink wine, coloured by only brief contact with red grape skins.

“a glass of rosé”

Such a simple and one-dimensional definition for a complex, diverse and let’s be honest, sexy product. Pale onion-skin orange to almost purple; still, semi sparkling or sparkling; sweet to bone-dry; this genre of wine is as diverse as the cultivars you can use to make it.

The production numbers at a glance…

  1. global rosé production: approx. 25 million hL
  2. accounts for approx. 10% of still wine production
  3. 80% of production: France, Spain, United States and Italy

Increase in rosé production since 2002:

  1. South Africa: 200%
  2. Chile: 400%
  3. Australia: 450%

The consumption numbers at a glance…

  1. global rosé consumption: approx. 23 million hL
  2. 20% increase in rosé consumption since 2002
  3. France and US: consume approx. half of global rosé production

Increase in rosé consumption since 2002:

  1. United Kingdom: 250%
  2. Sweden: 750%
  3. Canada: 120%
  4. Hong Kong: 250%

Call it what you will…a French rosé, a Spanish rosado, an Italian rosato or a German roséwein…this blush-coloured phenomenon has shaken off the frumpy “sweet and unsophisticated” persona and slipped into something a little bit more comfortable…the new crisp, dry and fruit-driven style of rosé taking the market by storm.

The three major rosé production methods, maceration, saignée and blending, will provide you with different styles and colour of rosé wines.

During the maceration method, the grapes are destined primarily for rosé production and the maceration period can differ significantly according the shade and intensity of rosé being produced. This method is popular for commercial rosé production. The saignée or bleeding method sees you remove some of the juice from the red wine production process to produce rosé and at the same time intensify the colour and tannin concentration of the red wine being produced. This method usually results in darker and more savoury rosé styles. The final method, blending, is less popular and more regulated in certain rosé producing areas like France, where white wines are enriched with coloured musts to produce a rosé wine. A less common method is that of vin gris, where the rosé is produced by the immediate pressing of red grapes without any skin contact. This method is generally practised on lighter coloured varieties like Cinsaut, Gamay noir, Pinot noir and Grenache.

So what makes a good rosé? The style that is gaining in popularity is that of a clean, fruit forward wine with crisp acidity, where freshness and complexity is balanced. To produce this, there are a couple of key factors:

  1. Light touch
  2. Gentle handling of the fruit
  3. Short and light press cycle
  4. Cold settling
  5. Fermenting at cool temperatures to retain aromatic compounds
  6. Use a dedicated yeast and enzyme combination to enhance bright, rich, fruity flavours

The style of rosé’s produced with these different methods, despite coming in a veritable rainbow of pink shades, can vary anywhere from light and mineral-like, to round and floral and rich and savoury. From a visual point of view, you can expect anything from a pale onion-skin hue, interspersed with salmon, rose, coral, watermelon coloured wines, all the way to the cherry and ruby red offerings. Rosé really has an outfit for every occasion…

With so many styles of rosé, differing in colour, sweetness, bubbles and aroma, you are sure to find the one that makes you blush!

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Non-Saccharomyces yeasts, MLF and Chardonnay flavour

by Heinrich du Plessis & Neil Jolly. 

This study follows similar studies done by us on Chenin blanc and Pinotage. The aim of this study was therefore to determine the effect eight different non-Saccharomyces yeast strains had on MLF and Chardonnay flavour.

Introduction

Wine production includes two important fermentation processes, i.e. alcoholic fermentation conducted by yeast, and malolactic fermentation (MLF) conducted by lactic acid bacteria (LAB)1. The yeasts drive alcoholic fermentation by converting sugar to alcohol, carbon dioxide and other secondary compounds that affect the aroma and taste of wine.1,2Malolactic fermentation contributes to further flavour complexity and microbiological stability of the wine, as well as the reduction of total acidity. During MLF, l-malic acid is decarboxylated to l-lactic acid and CO2. White wines do not usually undergo MLF, but it is desired in the production of certain full-bodied white wines.3,4

At the start of alcoholic fermentation, a large number of non-Saccharomyces species may be naturally present in the grape must, but the final stage of fermentation is usually dominated by alcohol-tolerant Saccharomyces cerevisiae strains.1,5 Non-Saccharomyces yeasts have different oenological characteristics to S. cerevisiae and they have been shown to enhance aroma and improve complexity of wines.5,6 During alcoholic fermentation, both Saccharomyces and non-Saccharomyces yeasts deplete the nutrients found in wine. These deficiencies, combined with toxic metabolites produced by the yeasts, can inhibit the growth of LAB.1,7,8 Despite considerable research, MLF remains a difficult process to initiate and control.9 The interaction between non-Saccharomyces yeasts and LAB is another factor that needs investigation.

Materials and methods

Eight non-Saccharomyces yeast strains (one Candida zemplinina, two Lachancea thermotolerans, one Metschnikowia pulcherrima, one Hanseniaspora uvarum and three Torulaspora delbrueckii) were used in mixed fermentations with one S. cerevisiae wine strain. Yeast strains were commercially available cultures or were obtained from the ARC Infruitec-Nietvoorbij microorganism culture collection. Yeast treatments without malolactic fermentation (MLF) and in combination with simultaneous MLF were investigated. A commercial lactic acid bacterium culture was used to induce simultaneous MLF. In total 18 treatments were evaluated in triplicate, and the Chardonnay wines produced with S. cerevisiae with or without MLF, served as the reference treatments. A standardised small-scale winemaking protocol was followed at an ambient temperature of 15°C. After completion of MLF, wines were bottled and subjected to descriptive sensory evaluations four months later.

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An Academic Foray Into Complexity in Wine: An Analysis of Language

By Becca Yaemans of The Academic Wino.

You see it often in wine tasting notes: “the wine is complex”, or something along those lines. But what does “complexity” in wine mean? Is it complex because of the number of compounds contributing to the flavors/aromas and structure of the wine? Or is it complex because of what we perceive to be tasting/feeling when we drink the wine? Or is it a combination of these or something completely different? The answer isn’t straightforward, with the definition of complexity in wine being different for different people.

For many in the wine business, complexity in wine refers to the combination of flavors and aromas in a wine evolving over the course of a tasting session. The Wine & Spirits Education Trust (WSET), “complexity is a desired feature in a wine and one which can result from fruit character alone or from a combination of primary, secondary and tertiary aromas and flavors.” However, it’s not as simple as plainly stating that a wine in and of itself is complex.  WSET doctrine continues, “only use the word ‘complex’ with context. It is not enough to say whether a wine is complex or not; you have to explain what provides the complexity.”

In academic literature, complexity in wine is an ongoing topic of study and one that has been met with mixed results. In general, studies seem to support the idea that complexity in wine is related to the number of aromas/flavors, balance, finish, etc., though understanding of the concept seems to differ between trained professionals and the average consumer (which shouldn’t be too surprising).

A new exploratory study, available online now and in print in the September 2018 issue of Food Quality and Preference, aimed to investigate how complexity in wine is perceived by “social drinkers”, with an attempt to identify specifically what characteristics were associated with the concept of complexity in wine.

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The malolactic enzyme – parameters effecting expression

By Wineland Media

Lynn Engelbrecht, Senzo Mtshali, Bronwen Miller & Maret du Toit

The results obtained showed that pH, ethanol and malic acid play an important role in the expression of the malolactic enzyme gene.Malolactic fermentation is a very important process in winemaking, resulting in deacidification, microbial stability and aroma modifications. The direct conversion of l-malic acid to l-lactic acid during malolactic fermentation is catalysed by the malolactic enzyme. Here we report on the results of two studies investigating the effects of pH, ethanol and malic acid on the expression of the malolactic enzyme gene (mle) from Oenococcus oeni and Lactobacillus plantarum. The expression of the mle gene was enhanced at lower pH levels (pH 3.2 vs. 3.8), as well as in the presence of malic acid, while expression decreased in the presence of ethanol. A higher expression level of the mle gene encoding the malolactic enzyme may be linked to a faster and/or successful malolactic fermentation and a better understanding of which parameters and how they affect mlegene expression, could aid in managing a successful malolactic fermentation. Our results also support the use of co-inoculation as a malolactic fermentation inoculation strategy.

Introduction

Genes are part of a living organism’s genome and are responsible for specific traits and characteristics. Each gene contains a set of instructions on how to produce a functional product, for example an enzyme. The process by which the information contained within a gene is used to produce this functional product or enzyme is called gene expression. Not every gene product is needed all the time. The organism assess the environment and then reacts on internal and external signals which triggers the expression of certain genes necessary for the development and survival of the organism at that specific moment.

Malolactic fermentation is a very important step in the winemaking process. By the conversion of l-malic acid to l-lactic acid, it contributes to deacidification of the wine, microbial stability, as well as softening, while the aromatic profile is also being influenced. Oenococcus oeni is the lactic acid bacteria mainly associated with malolactic fermentation and is the most favourable species used in malolactic starter cultures. However, the species Lactobacillus plantarum, which is also frequently found in grape must and wine, and effective in completing malolactic fermentation successfully,1 has also now been used in commercial malolactic starter cultures either as a single strain or mixed with O. oeni.

Ideally, O. oeni prefers to grow at a pH of 4.8, in a medium with £10% (v/v) ethanol and at a temperature of 22°C,2 whereas in wine O. oeni is exposed to harsh environmental conditions, including high ethanol concentrations (>12%), low pH (<3.8), sulphur dioxide, low temperatures (<18°C) and limited nutrients. However, it is able to survive this multi-stress environment and therefore the best adapted wine lactic acid bacteria. In order to survive these conditions, O. oeni employs different stress response mechanisms to preserve energy and to defend and protect the cell envelope. The main mechanism of survival is the metabolism of l-malic acid which generates a proton motive force, resulting in the production of energy through ATP synthesis and deacidification of the intracellular pH3 and in the presence of ethanol for example, O. oeni has showed to respond by increasing the fatty acid content in its membrane to regulate membrane fluidity.4,5

The direct transformation of l-malic acid into l-lactic acid by wine lactic acid bacteria is the result of the malolactic enzyme. A better understanding of the when, the where and what conditions promotes or prevents the expression of the gene coding for the malolactic enzyme, provides valuable information on predicting the effectiveness of malolactic fermentation.

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When microbiology is a data problem: Putting science together to make better pictures of yeast

A Portuguese-based group is suggesting that winemakers could have more useful information about choosing a yeast strain if scientists did a better job of putting together data from different kinds of experiments.

Scientific research generates a lot of different shapes and sizes of data. How does anyone make it work together?

Contemporary scientific research has a lot of big challenges, but here are three: funding, replicability, and integration. Funding is a great big gory topic for another day.

Replicability has seen a lot of attention in recent science news: scientists across disciplines have been reporting difficulty duplicating their colleagues’ results when they try to repeat the same experiments. This is worrisome. (Most) science is supposed to be about making observations about the world that remain the same independent of who is making the observations. Two careful people should be able to do the same experiment in two different places and obtain the same results. Well-trained scientists, however, are finding themselves unable to replicate the results described in scientific papers, and the community isn’t sure what to do about it.

Integration – how to fit together large amounts of lots of different kinds of data – looks like a separate kind of problem. Scientists (microbiologists, biochemists, systems biologists, geneticists, physicists…) study a thing – yeast, say – in many, many different ways. They generate data in many different shapes and sizes, using all manner of different kinds of instruments to make numbers that don’t just tidily line up with each other. But, at least in theory, all of those data are about the same thing – the same yeast – and so finding ways to integrate data from different kinds of experiments should massively improve our understanding of how yeast works as a whole ….

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