Rosés : a guide to successful maceration

Note: when they are present, the first aromas diffused by the pulp are grassy and vegetable. Most of these stabilise within the wine.

Note: grassy and vegetable aromas and the sensory acidic tannic and grassy sensations of the skin diffuse quite rapidly. Most stabilise within the wine.

This is especially notable when there is a gap in time between the technological maturity of the pulp and the aromatic and phenolic maturity of the skin.

Production objectives

Maceration helps to develop stable characteristics such as roundness, varietal aromas, coating or enrobing acidic sensations. The colour develops red hues.

Maceration entails investments and running costs higher than direct draining or pressing.

II. The key points to Maceration: the different elements to combine for a thorough and coherent procedure

The ICV "Guide to Successful Maceration" analyses the impact of 50 (!) key points before and after Maceration: from the sensorial profile of suitable grapes through to the detailed procedures of ageing.

This guide also outlines the levels of conformity of the monitoring indicators, in view of mastering the technique of maceration.

A coherent combination of the different key points is required to entirely complete this procedure.

We have limited this Flash to just a couple of examples.

A. Sanitary grape profile

In view of the quick diffusion of all the metabolites of pathogenic vine fungi, it is economic sense for healthy grapes to undergo Maceration.

Practical indicators of work focusing on visual criteria (this data comes from the ICV Vines & Wines Consultancy File - a document compiled by Consultants from ICV's Vines and Wines Department).

Note: by applying the right methods of protection against oxidation (fractionnated sulphiting), with a Maceration of 2 to 4 hours at 15°C, it is possible to fix the limit above 5% without rising above 10%.

B. Maceration & Temperature: objectives and methods of control

Temperatures ranging between 5 and 15°C are considered to be conforming for rosé wines. It is recommended to manage both the time and the temperature

 

Setting the right temperature is the first key point.

It requires specific equipment to cool down the fresh crushed grapes.

One option is that of harvesting grapes at the right temperature: morning or night, or during a cold day.

When it comes to big quantities it is practically impossible to organise a work schedule without the use of other specific methods of cooling down the fresh crushed grapes.

High-performance equipment controlling the temperature of the fresh crushed grapes is frequent in New World wine producing areas. This is one of the competitive strengths of companies in these countries.

Keeping the grapes at the right temperature during Maceration is the second key point to long macerations (over 6 hours).

Whether the objective is that of setting the temperature or maintaining it, actions shouldn't result in triturating or cause the oxidation of the grapes.

The security of cellar staff must be ensured, especially when "dry ice", "carbonic snow" or liquid CO2 are used.

C. Length of Maceration

In this paragraph, considerations about the length of time are only valid when the other Maceration parametres are conform: protection against oxidation, enzyme addition, destemming, crushing, temperature setting and control, no triturating, etc.

After 2 hours of maceration, a notable amount of hydrosoluble compounds are released, changing the analytic and sensorial profile of the juice and the wine, compared to direct pressing and draining.

As of 24 hours at 10°C, there's a change in style. Polysaccharides and polyphenols are released, stabilising the colour with phenomenon similar to those of red wine. The tannic sensation is stable and distinctly perceptible in the wine. This only currently represents a small segment of the today market.

D. Handling the fresh crushed grapes during Maceration

It is recommended not to handle the crushed grapes during maceration thereby excluding any pumping over, release or rotation of the press.

Indeed this could provoke the release of compounds producing tannic, aggressive and bitter sensations.

There's also a risk of violent uncontrollable oxidation.

As a result the inputs (SO2, enzymes, tartaric acid, asorbic acid) have to be added evenly.

Moreover the setting of the temperature has to be homogenous.

E. Inputs: doses and when to add them.

Inputs are the different additives and winemaking manufacturing products.

During a rosé maceration the main inputs are: SO2, enzymes and tartaric acid.

1 - SO2

It is best to split up the dose of SO2 to be added to the grapes. The key point is for the SO2 to be evenly distributed throughout the entire fresh crushed grapes.

The role of SO2 is that of blocking the chain of oxidative reactions.

Not to prevent oxygen to enter the mass of juice and crushed grapes : this is a non realistic vision of winemaking.

To this end a constant dosage of total SO2 is enough (always > 30mg/litre). No need to look for free SO2 at this stage.

The details of how to use SO2 are presented in Harvest Flash Info N°8 (click here to directly access to it).

It is recommended not to add more than 5 g/hl at any time to avoid violent chemical reactions.

A unique dose added to grapes above what is required (6-7 g/hl in the cellar) will make the fermentary yeast react violently: production of acetaldehyde and bad and bitter/metal smelling suphur off odours and off falvours.

When the correct Maceration, racking and fermentation procedures are implemented, there's a risk in using more SO2 than needed.

The prevention of microbial risks isn't better and selected yeast will react to this additional SO2:

In addition even if the total SO2 content is low at the end of Alcoholic Fermentation, this additional SO2 on the grapes will greatly delay the start to malolactic fermentation when it is required.

2 - Enzymes

Enzymes actively participate in achieving Maceration objectives: early diffusion of sought-after hydrosoluble compounds without triturating.

When the correct length of time and temperatures are respected, selected oenological enzymes remain sufficiently active.

It is recommended to correctly use enzymes: choice of preparation, immediate use, exact dosing in line with the pulp's mechanical resistance, homogeneity within the mass.

Afterwards enzymes result in the release of more juice during gravity extraction or gentle pressing.

Increases in colour (evaluated once the wine is finished) are not significant when the maceration is shorter than 24 hours, when compared to a control macerated during the same time without enzymes.

However the red tonality of rosé increases: +20% of 520 nm absorbance red nuances and -20% of 420 nm absorbance yellow nuances. (ICV R & D test).

Reminder: since the early 90's, ICV has demonstrated that the intensity of the final colour of a rosé depends upon the grape's colour potential and the intensity of the mechanical action of extracting, in particular the pressure of extracting.

The length of Maceration and enzymes affect the tonality of the colour and especially the aromas and the structure on the palate, not really the final colour.

3 - Tartaric acid.

It should be used immediately (or in the vineyard in the case of machine harvesting) to increase the effect of the SO2.

Reminder: all of the tartaric acid added to the grapes ends up in the juice, none of it is lost within the grape pomace;

Applying the ICV good practice for tartaric acid addition you don't loose your money (as many people fear) !

4 - Ascorbic acid

In countries where this product is authorised in producing white and rosé wines, it is recommended to immediately add it to the fresh crushed grapes along with the first addition of SO2.

From our trial and industrial experience, a dose of 5g/hl of ascorbic acid is sufficient to bring about the desired effects.

After the publication of some molecular research, some winemaker stopped using ascorbic acid in their cellars, changing dramatically their commercially established wine style.

Our practical vision : after 10 years of practical experimentation and experience all over the world, we have always seen the long term positive effect of ascorbic acid, as far as some Total SO2 can be measured (i.e. more than 30 mg/L) in the juice and then the wine.

To our experience there are no special risks due to the ascorbic acid even when there is no free SO2, even in high pH juice and wine.

Of course if the juice and the wine are lacking of SO2 protection, they will probably oxidize, without or with ascorbic acid. Ascorbic acid do not amplify the risk, as we measured it in the practice complex conditions.

Ascorbic acid has a positive effect on yeast during fermentation: it dramatically limits the production of some bad-smelling sulphur compounds and of a particular molecule (2 amino-acetophenone) both of which provoke "atypical ageing" (also known as ATA) characteristics.

This ATA is characterised by the rapid apparition (within a year) of chemical aromas and flavours: wax, oxidised honey, metal characteristics.

This phenomenon frequently occurs when the grapes aren't ripe enough, when SO2 hasn't been properly added to the grapes and the juice, or the wrong yeast has been used.

To our international experience, rosés from all countries can be sensitive to ATA.

Ageability of a rosé wine on a 18 month shelf life is a key issue for wines that are exported thousands of miles from their home. A fresh fruity aroma right after harvest is not a clue for good ageability. Maybe too many people think their rosé this way. Then who recognizes his own wine in the orange dull ethereal beverage taken on a supermarket shelf after 12 months ? It is not always the fault of the shop keeper...

F. Mastering and coherence of the following steps

Maceration is worthwhile when the wine has potentially a big foremouth volume with varietal flavours and good stability.

Choice of the following factors has to be in line with production objectives:

If the proper fermentation and maturing practices aren't applied, the wine sold in bulk or bottled after 4 to 6 months could develop chemical and rough characteristics, masking the varietal qualities.

To limit this risk, it is recommended :

These points are particularly important for wines made from grapes lacking in ripeness (<12% vol potential) or from overly ripe grapes (>13.5%). These wines tend to development sensory chemical characteristics when youth characteristics vanish.

They may develop mineral and grassy characters when maturity is low. They may develop ether, burning and bitter characteristics when maturity is high.

To respect all the consumers, winemakers should first think the way their wine will taste at the end of their shelf life and apply good ageability practice. Rather than try to elaborate trendy fresh rosé. Who else than the winemaker himself during harvest and show jury will apreciate it ? Such wines age very quickly and do not resist temperature and light stress during shelf life. Most consumers will only get an ex-fresh wine, ruined by time and the lack of prevention of bad ageability during winemaking.