Kegging Wine - When to add Nitrogen? || Kegging of wine || Wine making

Hello, wine lovers! Today, we go on an exciting adventure into the world of wine kegging, a method that is revolutionizing how we preserve and serve our favorite vintages. Whether you're a seasoned expert or just starting out in the wine business, understanding the complexities of kegging, particularly with nitrogen, may take your wine experience to new heights. Join me as we explore the art and science of kegging wine and learn how to maintain your wines with nitrogen.

Why Keg Wine?

Before we get into the technicalities of nitrogen and kegging, let's first understand why kegging wine has grown in popularity among both amateur enthusiasts and professional winemakers. Traditional bottling processes, while ageless, can provide difficulties in terms of storage, preservation, and serving. Kegging addresses these issues by giving unprecedented ease while assuring consistent quality with each pour.

Furthermore, kegs minimize the possibility of cork taint and oxidation, two major enemies that can undermine the quality of bottled wine over time. Kegs maintain the freshness, taste, and fragrance of wine by keeping it under pressure in a sealed atmosphere, ensuring that each sip is as enjoyable as the first.

Introducing Nitrogen, The Guardian of Wine Quality.

Let's now focus on the star of the show: nitrogen. Nitrogen, an inert gas, is essential for wine preservation because it forms a protective barrier that keeps oxygen out of the wine. As any seasoned wine specialist will tell you, oxygen is wine's deadliest enemy, capable of irreversibly damaging its delicate tastes and aromas. By adding nitrogen to the keg, we can successfully reduce the danger of oxidation and increase the shelf life of our wines.

But how can we identify the best time to add nitrogen to our kegs?

This is when experience and knowledge come into play. As someone who professionally kegs a lot of wine, I've found that once it's in a stainless-steel keg, wine doesn't mature or change very much. As a result, kegging should be considered the final stage in the winemaking process.

Age the wines as you usually would, enabling them to acquire the ideal flavor profiles and complexity. Once you're pleased with the maturing process, think of kegging as the equivalent of bottling your wines. Ideally, the keg should be filled to the capacity to reduce headroom. If there is unavoidable headspace, it is critical to purge it with nitrogen or another inert gas, such as Argon/CO2, to prevent oxidation and extend the wine's life.

Best Practices for Kegging Wine With Nitrogen

Now, let's look at some recommended practices for kegging wine using nitrogen to ensure maximum preservation and quality:

Before closing the keg, purge the headspace with nitrogen to remove any remaining oxygen. This process is critical for establishing a protective atmosphere that keeps the wine fresh and flavorful.

Maintain Constant Pressure: Keep your nitrogen tank connected to the keg at all times and use nitrogen to drive the wine from the keg into the glass. To reduce oxygen exposure and protect the wine's integrity, avoid opening the keg too frequently.

Follow Beer Brewing Techniques: Borrowing from the beer brewing playbook, consider filling the keg with nitrogen and bleeding the pressure release valve many times to achieve complete oxygen removal. This process helps to remove any leftover air from the keg, preventing oxidation and deterioration.

 

Here is the table with most commonly used wine keg sizes.

Keg Type	Capacity (gal/oz)	Height (inches)	Weight (lbs)	Width (inches)
Mini Keg	1.32/169	9.875	13	6.75
Sixth Barrel	5.16/661	23.375	58	9.25
Quarter Bareel	7.75/992	13.875	87	16.125
Slim Quarter	7.75/992	23.375	87	11.125
Half Barrel	15.5/1984	23.375	161	16.125
Cornelius Keg	5.0/640	23	49	9

Advances of kegging your wine:

Serving wine from a stainless-steel keg may lack the romance and history of popping corks, but a 5-gallon (19-L) keg can carry 25 standard (750 mL) wine bottles. Stainless steel kegs, like glass bottles, are inert and will not change the flavor of wine, even when stored indefinitely. Because there is no cork, there is no risk of trichloranisole contamination (TCA, cork taint) or cork breaking, leaking, or chipping. You also do not require a corkscrew!

Kegs also minimize oxidation. The quantity of headspace as a percentage of wine in kegs is significantly lower than in bottles – you fill the keg to the very top. Second, the kegs have great seals since they are designed to withstand pressure, and unless damaged, they do not leak. Finally, before filling the kegs with wine, they are purged with bottled gas, which removes oxygen. This guarantees that the wine tastes precisely the same as the day you bottle it.

When you keg your wine, you can consume one glass at a time without having to open the entire bottle. If you do need a bottle (for a dinner party or a picnic), you can easily fill it from the keg and cork it as needed. Is there a party upstairs? Go down to the cellar with a carafe or jug, and you'll be ready to serve in no time. Because the wine discharged is replenished with oxygen-free gas, it remains fresh until the bottom of the keg.

Kegs also have the advantage of being highly environmentally friendly. Commercial kegs have a 30-year lifetime, but they are mistreated, banged around in storage and handling, and damaged by cleaning equipment and during transit. With care and maintenance, most of the kegs repurposed from the soda industry have many decades of use ahead of them, and each year they'll save cork, capsule, and label waste, to say nothing of cardboard boxes and bottles lost to breakage and shrinkage.

In the end, kegging wine with nitrogen provides several benefits to both amateurs and experts. Understanding the critical role of nitrogen in wine preservation, as well as following proper kegging procedures, can guarantee that your valuable vintages mature gently and thrill your taste with each sip.

FAQs about Kegging of Wine

Can wine be kegged?

Stainless steel, like glass, is an inert surface that does not affect the flavor of your wine. Furthermore, because the headspace may be purged with an inert gas, such as nitrogen or carbon dioxide, oxidation is reduced in your kegged wine. With your wine in a keg, you may enjoy a single glass without having to open the entire bottle.

How long does wine last in keg?

Sparkling wines have a two-week shelf life, whereas still wines have four weeks. The better the conditions, the longer the shelf life (assuming kegs remain refrigerated). Kegs that have not been opened and are kept appropriately will last for 12 months.

Why do you keg wine?

To keep wine fresh, it must be properly maintained (similar to a significant other), avoiding over-oxidation and/or overheating. Kegged wine makes this much easier because the wine never comes into contact with air or gas until it is ready to be given to a visitor, and a keg is less prone to temperature changes.

Can you ferment wine in kegs?

I ferment in a bucket since it would block any keg, and then when it's clear and no longer dropping sediment in a secondary carboy, I transfer it to the keg. So, absolutely, serve, bottle, or anything from the keg.

How do you keg red wine?

So, if you're kegging some red wine, you'd siphon it from your fermenter into the keg and then set your CO2 regulator to a low pressure - maybe 2-3 psi (7 kpa). Seal the lid, apply pressure, and then release the purge valve multiple times to clear any leftover air from the keg.

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Carbonic maceration in wine || What is carbonic maceration, effects of carbonic maceration on wine || Wine making

 

What is Carbonic Maceration?

Carbonic maceration is the process of putting completely intact entire bunches of grapes in a closed fermentation chamber filled with carbon dioxide. A variety of intracellular responses occur within grape berries that have been handled in this way. Enzymes carry out these processes in the absence of oxygen, with no yeast or microbial activity. The enzymatic processes last about a week at temperatures up to 35°C, after which they stop due to the minimal amount of alcohol generated. The fruit is then destemmed, crushed, and fermented with yeast under standard winemaking conditions.

What reaction happens during carbonic maceration and what is the impact of carbonic maceration on the grape berry/ wine?

The grape berries absorb carbon dioxide, filling them up to around 50% of their capacity. Reactions within the berry, which is still alive while whole, transition from respiratory to anaerobic metabolism.

Malic dehydrogenase is an important enzyme in carbonic maceration because it converts malic acid to ethanol, succinic acid, and aminobutyric acid without creating lactic acid. As a result, titratable acidity decreases and pH increases.

Grape alcohol dehydrogenase converts sugar into ethanol and CO2. Only 0.5-2.2% of ethanol is created, which might be because at this concentration, ethanol begins to impair cell membrane integrity. The amount of carbon dioxide created during the first 24 hours is roughly equal to that absorbed.

Glycerol and shikimic acid are produced, with shikimic acid accumulating within the berry and then degrading to cinnamic acids, and then to the three main aroma compounds associated with carbonic maceration: benzaldehyde ('cherry', 'kirsch', 'almond'), vinylbenzene ('styrene', 'plastic'), and ethyl cinnamate ('cinnamon','strawberry', 'honey'). Other enzymes that can create volatile scents that may contribute to carbonic maceration flavor include ethyl and methyl vanillate ('vanilla'), ethyl 9-decenoate ('sweet', 'fruity', 'quince'), and 1-octanol ('almond'/'buttery').

Carbonic maceration wines generally have lesser primary fruit flavors, which might be due to reduced concentrations of some common wine esters. For example, hexyl acetate ('fruity', 'green', 'pear') can only develop in an oxygen-rich environment during crushing, therefore its formation would be reduced in the anaerobic environment of carbonic maceration.

What is the impact of carbonic maceration on the wine?

Carbonic maceration wines have a particular scent that frequently polarizes tasters. The scents can be characterized as 'fruity' or'musk-like', with'strawberry/raspberry' and 'cherry/kirsch' aromas (especially in Beaujolais wines), as well as 'vanilla','spice', 'almond', 'cinnamon','sandalwood', or 'oak-like' qualities. These characteristics frequently overpower any varietal fruit character, although they can also provide scent to wines with little varietal or fruit character.

In general, the wines are softer, less acidic, and have lesser phenolic component extraction. They are said to develop more quickly than normally fermented wines. As a result, the approach has traditionally been suggested for lighter-bodied/fruity wines meant for early consumption. According to sources, Australian winemakers are experimenting with carbonic maceration or partial whole bunch fermentations in Pinot Noir and Shiraz to produce more refined and aromatic wines, as well as to help in blending.

Effects of carbonic maceration on the phenolic compounds in wine/ grape berries.

Carbonic maceration differs from traditional winemaking in terms of phenolic extraction from grape skins, such as anthocyanins and tannins. While ethanol serves as a solvent for phenolic extraction in both procedures, conventional fermentations have a greater proportion of skin and seed contact time at higher alcohol concentrations than carbonic maceration, resulting in more anthocyanins and tannins being extracted. Carbonic maceration causes anthocyanins to spread from the epidermis into the pulp, resulting in a pink flesh. Any tannin extracted into the pulp at low alcohol percentages is more likely to be skin tannin rather than seed tannin, which may give the impression that the wine has softer tannins.

Risks during carbonic maceration.

Carbonic maceration increases the risk of spoiling by acetic acid bacteria and Brettanomyces yeast due to the higher pH, hotter temperatures, and lack of sulfur dioxide. Furthermore, if a carbon dioxide-rich atmosphere is not properly maintained, aerobic microbes can swiftly take control, resulting in wine deterioration.

How do you do it?

Michel Flanzy created the initial method in 1934. A modified version, patented by Stephen Hickinbotham in 1986, features complete grape bunches packed in a plastic bag supported by a pallet box, which already contains a tiny amount of dry ice in an insulated container. The plastic bag is then sealed and occasionally supplied with a one-way valve that allows carbon dioxide to exit while preventing air from entering.

Carbonic maceration flavor and structure are best achieved when grapes are held at temperatures between 30-32°C for 5-8 days. Lower temperatures provide more delicate and short-term scents, although the strength varies depending on the grape variety or wine style. Carbonic maceration occurs more easily in a gaseous atmosphere, hence the amount of juice produced by the berries is frequently inversely proportionate to the degree of carbonic maceration taste. With more juicing and more aerobic conditions, yeast and bacteria fermentation can occur, with the resultant flavors, as well as those from stem touch, limiting or outweighing those from carbonic maceration.

References

Etaio, I. Elortondo, F. J. P. Albisu, M. Gaston, E. Ojeda, M. Schlich, P. 2008. Effect of winemaking process and addition of white grapes on the sensory and physicochemical characteristics of young red wines. Aust. J. Grape Wine Res. 14:211-222.

Cowey, G. 2018. Ask the AWRI: Carbonic maceration Aust. N.Z. Grapegrower Winemaker (651): 70-71.

Ducruet, V. 1984. Comparison of the headspace volatiles of carbonic maceration and traditional wine. Lebensmittel- Wissenschaft & Technologie 17(4): 217-221.

Flanzy, C., Flanzy, M., Benard, P. 1987. La vinification par la maceration carbonique. Paris: INRA.

Sneyd, T. N. 1989. Carbonic maceration: an overview. Aust. N.Z. Wine Ind. J. 4(4): 281-282.

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The things you should know about Chianti-Classico || Geography, Viticulture & Enology || Italian Wine Region

 

Tuscany: the word alone conjures up pictures of a timeless environment with wooded hills, cypress trees, villas, and old farmhouses. A visitor to the region cannot help but be captivated by the ambiance. As Oz Clarke so well stated, "You can't go to Tuscany without wanting to be more like the Tuscans." Chianti Classico, the most famous wine area in Italy, is located in the heart of Tuscany, between the historic towns of Florence and Siena. In reality, Chianti Montalbano, Chianti Colli Fiorenti, Chianti Rufina, Colli Senesi, Colline Pisane, and Colli Aretini are the other six Tuscan wine regions that can claim the name Chiant. However, it is Chianti Classico, closely followed by Chianti Rufina, that produces the reputed wines.

Geography

The Chianti Classico area spans 40 kilometers north to south and 25 kilometers west to east. The steep topography is far from viticultural monoculture, with vineyards mixed with woodlands, olive orchards, sunflowers, and other vegetation, accounting for just 10% of the total surface area. One explanation is that the principal grape varietals can only mature adequately in the ideal locations. The hills give favorable perspectives and cooling winds; for example, Sangiovese is thought to require a southerly exposure for dependable ripening.

Wine has been produced in the region for centuries; the word Chianti, which refers to red wine, was first attested in 1404. The first effort at territorial delimitation occurred in 1716. Prior to the 1960s, vineyards as we know them were uncommon; grapes were intermingled with other crops, perhaps in single rows between plots used for other crops. Massive replanting occurred in the 1960s and 1970s. There are 7,000 hectares of vineyards with Denominazione di Origine Controllata e Garantita (DOCG) designation.

Sangiovese, like Pinot Noir, is less pigmented than many other red wine varieties--it contains less acylated anthocyanins--and Canaiolo may have been included in the mix to boost color. Malvasia Bianca, on the other hand, is supposed to enhance scent and soften the palate. Also, because the other traditional red types mature before Sangiovese, the wine had more body in weak years. Today, Cabernet Sauvignon or Shiraz are more likely to perform this function than Canaiolo. Nonetheless, some producers may contend that Canaiolo is necessary for the traditional flavor of a Chianti Classico.

Because of the undulating geography, the region's climate is quite varied. Temperature is strongly influenced by altitude, and vineyards may be found at elevations ranging from 250 to 600 meters. However, Sangiovese is thought to mature best when cultivated at elevations lower than 380 meters. Summers are hot, but winters are frigid; for example, MJT is 23.1°C (range from 24.0°C at 50 m to 22.0°C at 450 m), and CTL3 is 17.7°C. Autumn rainfall is critical: there is a negative correlation between vintage rating and September rainfall. The average rainfall throughout the growth season (April to October) is 452 mm, with 79 mm in September. Hail and frost are the main issues. The most favoured soils are the calcareous marls (galestro), principally found in the central part of the region. In the north, clay soils are more common.

Viticulture and Enology

Poggio Amorelli, winery of Chianti region

Row x vine spacing is 1.7 to 2.5 m x 0.75 to 1.0 m, with newer vineyards having tighter spacings. The trellis is a VSP type, with a fruiting wire at 50 to 70 cm, two pairs of moveable foliage wires, and a single fixed foliage wire at the top of the post (110 to 140 cm). Sangiovese is often grown to a unilateral cordon and clipped to single-node spurs. Pruning is typically done by hand, however mechanical pre-pruning may be utilized, and results in the retention of just 3 to 4 spurs per vine. In high-yielding vineyards, all varietals may be planted with at least two arching canes per vine. Shoot density can be as low as 5–6 per lineal m. Bunch thinning near to veraison is common technique to achieve maturation before the autumn rains. Irrigation is not allowed on bearing vines. Budburst occurs in early to mid-April, and harvest usually begins in mid-September (at low elevations) or early October. On deep soils, the most common rootstocks are 420A and 3309, while 110 Richter and 779 Paulsen are used on dry, calcareous soils.

Chianti Classico wines must have a minimum alcohol content of 12% (12.5% for Riserva) and a yield of no more than 8.5 t/ha (or 3 kilograms per vine). Furthermore, five years after planting a vineyard, its I grapes can be utilized for Chianti Classico. Riverva wine (taken from the finest vineyards) accounts for about 20% of total output and is matured in big and small oak barrels with a life expectancy of ten years or longer.

Wine Tasting in Chianti-Classico

Those traveling in Siena or Florence (or the provinces of Siena and Florence) have easy access to the Chianti Classico region's farms and vineyards. The following is a list of well-known wineries/wine stores you may visit directly with your own (or rental) car/bike.

VITICCIO (Greve in Chianti)

Greve in Chianti

Wine tastings are available every day of the week at the Viticcio winery estate and may be scheduled by appointment. Simply call to book a visit at a time that works best for you.

This is a family-run winery, therefore you'll most likely be guided by a family member on your adventure into the world of wine, beginning with their vines and progressing to the winery before tasting their wines, which you can then purchase. Visit their official website for additional information on wine tastings and excursions.

CHIANTI CLASSICO, MONTALCINO & MONTEPULCIANO

Chianti Classico

If you're feeling brave and want to see all three lovely Tuscan wine districts in one day, we recommend taking a guided trip like this small group one (max 8 people). You'll enjoy the journey to Greve, Castellina, and then via Monteriggioni, Montalcino, and Montepulciano, as well as the wines and a lovely lunch, without having to worry about driving. It's a long day, but you'll see a lot of Tuscany in one day dedicated to the region's most famous wineries.

CASTELLO DI BROLIO (Gaiole in Chianti)

Castello Di Brolio

The Enoteca del Barone Ricasoli is accessible for tastings, both individually and in groups, by reservation. In addition to tasting and purchasing Ricasoli wines, the staff enoteca may also sell excellent items from the region, such as honey and olive oil.

If you don't have a vehicle or don't want to drive while tasting wine, you can still visit Castello di Brolio from Siena on this guided trip, which also includes lunch and a visit to a third vineyard in the afternoon, as well as time in a neighboring town. It's a full-day tour (8 hours).

THE CASA DEL CHIANTI CLASSICO (Radda in Chianti)

Radda in Chianti

The "Casa del Chianti Classico" is the first "house of wine" for the Chianti Classico Wine Consortium, having opened in June 2014 in Radda in Chianti. The "Casa Chianti Classico" allows you to taste and buy from the world's greatest selection of Chianti Classico labels, as well as a terrace with a view to enjoy a lunch or supper and various wine-related events, courses, and exhibits. Unfortunately, the most of activities take place during the summer, although the wine shop and patio are open all year. Visit the official website to learn more.

References:

Some of the information in this article was provided by Christian Maurer (Isole e Olena) and Gionata Pulignani (Castello di Fonterutoli).

Clarke, O. (1995) Oz Clarke's Wine Atlas (Websters International Publishers: London)

Nesto, Bill; Di Savino, Frances (2016). Chianti Classico: The Search for Tuscany's Noblest Wine. University of California Press.

Flower, Raymond (2012) [1978]. Chianti: The Land, the People and the Wine. Garrett County Press.

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Malolactic fermentation in red wine.|| MLF/Fermentation || Wine Making

 

Malolactic fermentation (MLF) is a secondary bacterial fermentation that occurs in most red wines. Oenococcus oeni, a member of the lactic acid bacteria (LAB) family, is the primary bacterium responsible for MLF owing to its capacity to withstand the severe circumstances of wine (high alcohol, low pH, and low nutrition) and produce good wine sensory qualities.

One key purpose of MLF is to provide microbiological stability for the subsequent metabolism of L-malic acid. MLF specifically eliminates L-malic acid from wine, which can serve as a carbon source for yeast and bacterial development, potentially resulting in spoilage, spritz, and unpleasant flavours. MLF can also be used in select wines to alter their character.

MLF can be generated by inoculating a specific bacterial strain or happens spontaneously during primary fermentation. Because natural or 'wild' MLF can be unpredictable in terms of onset time and influence on wine quality, malolactic starter cultures are widely employed.

This article provides practical information for induction of MLF in red wine. Achieving effective malolactic fermentation provides further practical instructions for MLF induction, monitoring, and maintenance.

Essential parameters for a successful MLF in red wine.

• Composition of Red Wine or Must.

Alcohol, pH, temperature, and SO2 concentration are key wine compositional parameters influencing MLF performance. Before beginning with MLF inoculation, it is advised to test these parameters and make modifications as needed. Each of these parameters has a range within which MLF is beneficial. As one or more of these criteria grow unfavourable, the MLF will become more challenging (the variables are cumulative). The table below summarises favourable and unfavourable circumstances for MLF in red wine and provides further explanation.

Parameter	Favourable	Unfavourable
Ethanol (%v/v)	<14	>16
Temperature (℃)	18 -22	>16 - <25
pH	3.3-3.5	<3.3
Total SO2(mg/L)	<30	>40

• Alcohol

The possible alcohol concentration of red wine is an important factor to consider while inducing MLF. It is advised that wines with a potential ethanol level more than 15-16% v/v utilize an ethanol-tolerant strain of malolactic starting culture. Furthermore, co-inoculation should be explored since it may help the bacteria culture adapt to increased ethanol concentrations during fermentation. Consider pre-adapting the starting culture to high ethanol conditions.

• Temperature

The optimal growth temperature for LAB in grape juice is approximately 30°C. However, when ethanol content increases, the optimal temperature decreases due to the harmful effects of ethanol on bacteria at higher temperatures. Temperature should be 15-25°C (ideally 18-22°C when other factors are unfavourable and alcohol concentration is about 10% v/v). Inoculation temperature is crucial as it is the development stage that is most vulnerable to suboptimal temperatures. Temperatures over 25°C slow down MLF, increasing the danger of bacterial deterioration and volatile acidity. When using co-inoculation, it's important to prevent high temperatures throughout the alcoholic fermentation process.

• pH

Higher pH levels, especially over 3.5, promote growth of MLF bacteria and other spoilage germs such as Pediococcus and Lactobacillus strains. To prevent the formation of spoilage bacteria in red must and wines with pH levels above 3.5, consider co-inoculation and post-MLF stabilisation.

• SO2 concentration

Lactic acid bacteria, particularly Oenococcus oeni, are extremely sensitive to the molecular form of SO2. To prevent the harmful effects of molecular SO2 on malolactic bacteria, it is recommended that must/wines for MLF induction have no detectable free or molecular SO2. It is worth noting that traditional SO2 measurement methods in red wines, such as aeration-oxidation, can overestimate free and molecular SO2 concentrations. Total SO2 content is a good indicator of a wine's possible influence on malolactic bacteria and MLF, since bound SO2 may hinder them.

Adding a maximum of 50 mg/L total SO2 to grapes before crushing is not expected to negatively impact MLF. However, due to the possibility of SO2 buildup from various extrinsic (e.g., grape harvesting and shipping) and intrinsic (e.g., yeast strains employed in alcoholic fermentation) sources, it is advised that an accurate total SO2 measurement be performed prior to MLF induction.

For ideal MLF conditions, young red wine should have a total SO2 level of less than 30 mg/L. Total SO2 concentrations above 40 mg/L might delay or totally inhibit malolactic fermentation (MLF), depending on the malolactic bacteria strain and wine conditions. Concentrations above 50-60 mg/L may completely inhibit MLF.

• Other inhibitory factors

Pesticide residues, elevated copper levels in the vineyard, and yeast-derived medium-chain fatty acids can all impede MLF.

MLF strain selection criteria for red wine.

• Bacteria strain tolerance

When selecting a malolactic starter culture, it's important to consider the strain's tolerance to the physical and chemical conditions of the wine. This is especially true when selecting a strain for red must/wine, where, for example, in wines with an ethanol level of 15-16% v/v or more, the strains available are limited to those with high alcohol tolerance.

• Malolactic starter cultures for red wine: Oenococcus oeni and Lactobacillus plantarum.

Commercial malolactic starter cultures consist of many Oenococcus oeni strains, each with unique sensitivities to various winemaking conditions and uses. However, starter cultures of Lactobacillus plantarum, another member of the wine lactic acid bacteria family, are becoming accessible for use in red winemaking. Winemakers can use L. plantarum strains' specific physiological features to induce MLF in red wines.

• Yeast-bacteria compatibility

The compatibility of primary fermentation yeast with malolactic bacteria is a significant determinant in the success or failure of MLF. Certain yeast strains may block MLF by producing metabolites such as SO2 and certain fatty acids. Using a yeast strain with high nitrogen demand, especially under low YAN must circumstances, might deplete the nitrogen pool for malolactic bacteria. To lessen yeast inhibitory effects on MLF in red wines, choose an appropriate yeast/bacteria mix (according to supplier/manufacturer recommendations).

• Period of inoculation

Bacteria can be inoculated at various phases of the winemaking process, with sequential and co-inoculation being the most prevalent ways. Timing decisions may be influenced by processing concerns and the type of starting culture employed.

Co-inoculation, which involves inoculating malolactic bacteria at the beginning of alcoholic fermentation (18-24 hours after yeast inoculation), is becoming increasingly popular. Importantly, especially in red winemaking, co-inoculation may potentially facilitate:

• A shorter overall fermentation time, which can lower the risk of spoilage by other microorganisms including Brettanomyces.
• Overcoming MLF problems associated with high ethanol levels and reduced nitrogen content at the end of primary ferment.
• Co-inoculation can improve the usage of particular Lactobacillus plantarum strains for MLF in red winemaking.

Lactic acid bacteria are sensitive to SO2, hence when co-inoculation is performed, bacteria should be added after yeast activity has been detected. After adding SO2, wait at least 18-24 hours after inoculation to allow yeast to bind the free SO2. Co-inoculation requires temperature management, especially in red wines where high fermentation temperatures can harm both bacteria and yeast.

There may be some risks associated with co-inoculation, including:

• Inhibition by high SO2 added during harvest/crushing
• Competition with yeast growth
• Antagonistic yeast/bacteria relationships (MLF strain compatibility is thus important.)
• Stuck primary ferments causing possible production of acetic acid from LAB.

In some red winemaking applications, several timing choices might be employed. Delaying the beginning of MLF, for example, may help to retain colour in lighter-colored red wine varietals from colder winemaking locations. Furthermore, for certain commercial preparations of Lactobacillus plantarum, the producer may prescribe inoculation of a specific starter culture prior to the start of alcoholic fermentation.

Role of Monitoring MLF in quality control parameter in red winemaking.

Monitoring MLF completion is crucial for ensuring quality control in red wine production. Regular assessment of L-malic acid content allows for correct commencement and completion of MLF, as well as efficient post-MLF wine stabilisation (e.g., SO2 addition and pH adjustment).

Controlling MLF with a chosen malolactic strain requires determining its onset. Regular monitoring can easily establish the incidence of delayed or stalled MLF, and if necessary, a rescue starting culture may be immediately deployed. This avoids the dangers associated with uncontrolled proliferation of spoiling bacteria.

To determine MLF completion, strive for a 'not found' malic acid result (<0.05 g/L by enzymatic assay). However, a result of 0.1 g/L or fewer is low enough for the MLF to be regarded nearly complete and to reduce the danger of MLF spoiling after bottling. Precise monitoring of MLF completion reduces the possibility of uncontrolled growth of other wine microorganisms, as well as spoiling. Delays in post-MLF wine stabilisation, in particular, can result in increases in volatile acidity and other spoiling events. Wines are susceptible to oxidation and spoiling from microbes including acetic acid bacteria and Brettanomyces. Accurate identification of MLF completion is therefore critical in preventing such spoilage and quality degradation.

Co-inoculation can lead to MLF completion before alcoholic fermentation. In such instances, it is advised that post-MLF wine stabilisation be carried out once alcoholic fermentation is complete.

References

• Howe, P.A., Worobo, R., Sacks, G.L. 2018. Conventional measurements of sulfur dioxide (SO2) in red wine overestimate SO2 antimicrobial activity. Am. J. Enol. Vitic. 69: 210-220.
• Nordestgaard, S. 2019. AWRI Vineyard & Winery Practices Survey.
• Coelho, JM., Howe, P.A., Sacks, G.L. 2015. A headspace gas detection tube method to measure SO2 in wine without disrupting SO2 equilibria. Am J. Enol. Vitic. 66: 257-265.

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Introducing Oxygen to your Wine || Wine Making

Pump-over Red Wine

Aeration is especially important during red fermentations because it serves a variety of functions that reach well beyond the surface of the fermented must. In this blog, we will dig into the fascinating world of aeration and its critical contributions to winemaking, concentrating on three major areas: enhancing yeast health, reducing reductive smells, and changing phenolic compounds in wine.

Aeration is more than just a method; it's a finely honed skill that winemakers use to shape wines with precision and grace. Aeration has a significant influence on yeast viability, as well as the texture and structure of the finished product. This information sheet serves as a reference for winemakers commencing on the aeration journey, giving a complete overview of the key stages that establish the groundwork for producing great red wines.

Who is this information intended for?

This data sheet will be especially valuable for individuals who utilise open-top fermenters like Potters and SWAPs. Rotary fermenters may require extra engineering to execute ferment aeration, thus they are beyond the scope of this data page.

Methods of Aeration:

As we continue with our study of the delicate art of red winemaking, it is critical that we understand the aeration methods used. In this section, we will discuss two of the key strategies mentioned in our information sheet, each of which provides winemakers with distinct benefits in creating the ideal red wine profile.

In-line Devices: Venturi or In-line Sintering

The first solution we present makes use of in-line devices, notably the venturi or in-line sinter. In-line aeration combines smoothly with pump-over-based cap management procedures, providing an effective solution. A notable benefit is that both processes, aeration and pump-over, need the pump. Winemakers may improve aeration while saving money by combining cap management with a venturi air delivery mechanism. The benefit of this technology is that it eliminates the requirement for a separate air supply.

If you choose an in-line sinter, keep in mind that this device requires a compressed air supply to function. This strategy is beneficial when pump-overs are not used for cap management or when there is a desire to separate aeration from cap maintenance. Choosing an in-line sinter allows winemakers to free up pumps for other processes, lowering total energy expenses.

In-tank Devices: Sinters.

The second strategy focuses on in-tank devices, notably sinters. While in-line aeration works perfectly with pump-over operations, in-tank sinters are an option for individuals who want to separate aeration and cap control. This is especially useful for wineries looking to simplify their operations and reduce the energy expenses involved with the process.

Opting for a drop-in or fitted in-tank sinter frees up pumps for other important winemaking operations. However, it is vital to remember that this method needs a separate air supply. Despite this necessity, the benefits lay in the freedom it provides winemakers, allowing them to adjust their aeration strategy to their own tastes and operational requirements.

What are the requirements to get started?

Much of the equipment required for the most basic aeration activities is likely already present in the winery. The important factors are:

Air delivery equipment can be any of the following:

In-line sintering requires a pump and air supply, while venturi devices simply need a pump for a drop. Air supply is required for both built-in and fitted sinters.

Install point-of-use filters and non-return valves on the air inlets of inline spargers or venturi devices. Point-of-use filters prevent environmental pollutants from entering the system, while non-return valves prevent liquid contamination from the pump line during aeration stops.

Air supply: compressor or bottled gas.

Ensure that the air supply is food-grade. For further information, please see the section on air quality below. Air delivery control, including regulator and gas flow meter. Pump compatible with in-line air delivery equipment (if applicable). Consider the pressure drop across the device and the pump's ability to sustain that pressure/flow rate. This lowers vibration and premature failure of pump seals and bearings.

When and how often should I aerate?

Aeration procedures can begin after a 1-2. Baumé drop occurs when the cap rises or obvious symptoms of fermentation appear. To successfully regulate reductive smells and phenolic chemicals, several daily 30-minute aerations are recommended. This process might continue for several days until 60% of the initial sugar is utilised.

Determine the Appropriate Airflow Rate

One critical aspect of aeration is determining the proper airflow rate. When using in-line or drop-in spargers, a suitable starting point is an airflow rate of 0.5 L/min per kL of ferment volume. A flowmetre with a ball bearing indication is extremely useful for accurately measuring and controlling this airflow. This simple visual aid not only ensures the device's correct operation, but also serves as a preventive precaution against unnecessary and excessive air use.

Flowmetres assist decrease compressor runtime and system pressure variations. Using bottled air might also assist. Limit the quantity of gas cylinders purchased. Although they may appear to be a somewhat pricey purchase, they will yield long-term benefits.

The airflow rate while using venturi injectors is determined by parameters such as pump flow rate, device placement, and pressure drop across the device. As a result, achieving exact control over the air supplied into the ferment may prove difficult. A viable approach is to attach a simple gas flowmetre to the device's input. This feature provides information on the volume of air pulled in, which is essential for monitoring and optimising the aeration process.

Reference and further reading:

Day, M.P., Espinase Nandorfy, D., Bekker, M.Z., Bindon, K.A., Solomon, M., Smith, P.A., Schmidt, S.A. 2021. Aeration of Vitis vinifera Shiraz fermentation and its effect on wine chemical composition and sensory attributes. Aust. J. Grape Wine Res. 27(3): 360–377.

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