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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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