by Della Toffola Pacific MD, Paul Baggio
WINEMAKERS AGREE that the more rapid the grape juice is separated and drained from the polyphenol oxidase enzymes a lower concentration of browning fractions and oxidation occurs. It would hold then that a juice extraction design that more effectively efficiently ensures juice separation would be the press of choice for winemakers.
By virtue of the membrane press bag in any side bag press design taking up 50% of the tank surface area, little surface remains for drainage screens with side bag press designs by comparison to a design where by the whole tank surface is covered by drain screen. Take into account loading doors the typical drain screen surface available for side bag presses is only 22% – 24% of the press tank surface. When compared to the Della Toffola press design which provides 88% of its tank surface area with drain screens, it is clear why a Della Toffola press design is on many levels the superior pressing technology.
Central membrane press design by comparison to Side Bag press design:
- The whole inner press tank wall gets covered with drain screen surface;
- The axial feed can be positioned in the centre of the press tank (ref attached) to ensure more effective organic distribution of in-fed grapes occurring along the drain screen surface. With an axial infeed positioned at any one end of a tank press as per a side bag press design the pumped in grapes fall ultimately all at one end of that tank press. Positioning the axial feed at the end of any large tank press imposes the requirement to constantly rotate the tank using the flights within the press tank to distribute the grapes within the tank to any drain screen available. The larger the press the more significant the problem. The process of grinding skins continuous along the flights we know increases solids generation significantly. The design of the Della Toffola press with the axial feed pipe positioned in the centre of the press tank is the suitable position to enable the in-fed grapes, in a static position (not requiring drum rotations) to distribute left and right screen areas. A significant reduction in suspended solids generation by comparison; and
- The juice drainage in central membrane presses occurs without the back pressure as occurs in side bag presses. The back pressure within side bag membrane presses has nowhere to go but to sheer through the skins and juice volume competing to push through the same drain channels out of the tank, very much through the very same path the juice must travel. This is not the case for central membrane presses where by the path of least resistance for the back pressure/ air gets vented in the opposite direction of the draining juice to atmosphere out the north-facing axis. The concentrations of dissolved oxygen mixing with the concentrations of polyphenols is dramatically reduced for Della Toffola press designs. Studies performed by the University of Adelaide highlighted this dynamic, resulting in lower concentrations of browning fractions for Della Toffola extracted juice compared to side bag juice extraction.
The popularity of vineyard destemming is changing a lot of the thinking surrounding front-end grape receival. How suspended solids and ‘lees’ are generated and how best they are managed has dominated the winemaking narrative in these last years. The investment into floatation and importantly the costs associated with high solids cross flow to process juice lees has had the most striking impact as to focusing on how juice solids can be reduced. Investing in a press technology that reduces the solids loading for down-stream processes is what is influencing the decision to invest in Della Toffola press technology.
- Della Toffola tank presses can be loaded at faster rates of 100-130m3/hr. They can simultaneously drain at rates faster than 100m3/hr and can do so in a static position with the door hatch closed. A 240hl press can have loaded some 75tn, a 100m3/hr pump would load and drain a 240hl Della Toffola press in 3/4hr. The performance of side bag presses by comparison accept 50-55tns of grapes and require 1.30hrs on average to load;
- The load volumes of a Della Toffola 480hl press are 110tn to 120tns and can be loaded with a 130m3/hr pump in under an hour. Press cycles for Della Toffola presses are typically 90 to 100 minutes. The same cycle time is required for the 240hl press as for a 480hl press. The vertical channel drain design coupled with the fact that with a central membrane the distance of extension and retraction of the membrane press bag being half that of side bags the performance no matter how more longer or wider the press tank may be the press cycle remains linear. This is certainly not the case for side bag presses. The larger they get the less efficient and less effective the drain and separation becomes;
- As Della Toffola presses can have positioned two marc doors on each axis the marc removal time is only 15 minutes. The time required to remove the same volumes from side bag presses is significantly more and becomes more cumbersome as the presses increase in dimension and volume; and
- Cleaning time required for grape to grape processing is approximately 15 minutes. Hot water and caustic can be injected into the tank press to effect any more intensive CIP regimes or to accelerate a more intensive clean program. The ability to install three, even four doors, for a central membrane press enables the most effective ease of access of any tank press design. If internal access to tank presses are a priority concern, then the Della Toffola design better mitigates the issues of confined work space compared to other presses.The total complete turn-around press cycle time for a Della Toffola press is three hours, with one of our large clients processing per day with two 240hl Della Toffola presses 700-750 tonnes per day. It is technically possible to perform six cycles in a 24 hour period.Thus not only do central presses extract a lower suspended solid extract, with lower polyphenol browning fractions, but each tank press load can have added up to 40% additional grape volume by comparison and will process in a turn-around time nearly twice as fast as any side bag press.Do the screens need to be taken off? The resoundingly feedback by our customers is that they only remove the screens once a year post vintage. Some of our most experienced customers have concluded that they do not need to remove the screens at all. Where increasing Occupational Health and Safety legislation is encroaching on the ability of technicians being able to access confined spaces, the proven design of the Della Toffola vertical screen design not requiring any need to be removed has been welcomed. As already outlined, the mere fact that our current advised CIP times are only 15 minutes to effect what most wineries claim is best practice, any more intensive regimes required can be easily accommodated.
NB: Given per day the performance of any Della Toffola is twice as fast as any side bag press, if clients really wish to remove press screens in between each press load, they would certainly have far more time to do so with any Della Toffola press compared to a side bag press operation.
Similarly with bag changes. I understand a lot is being said by our competitors about the duration of what it takes to change a bag. Sure a bag change is inevitable yet how that is managed can occur many ways. As per discussions with some wineries we have run drills off season, if the notion of down time in harvest is such a dramatic concern for the sake of what is the cost of a bag (about Euro 6,000) why not change a bag in the down time/post or pre vintage period would be a suggestion. In any case, our experienced teams using a 240hl press takes around 5 – 6 hours. The larger 480hL press, due to the weight of the press bag, our customers potentially could take up to 7 – 8 hours. Yet those times are largely due by virtue that bags are not regularly changed and customers are not expert.
Our perspective is that a press is invested into as the winery has a requirement to extract juice. Without knowing the time frame the same skilled team would take to change one bag versus another let’s just accept for the purposes of discussing this issue that changing a DT press bag may possibly take two to three hours more than a side bag press bag change as per our competitors comments. Given those time frames are the worst case, if a bag change is required every 7 to 8 years would someone seriously decide on a press investment disregarding all the major benefits as to actual press extraction?
The Della Toffola central membrane press is a very proven press technology that presses twice as fast as any side bag press, per press load presses significantly more volume, delivers a substantial greater proportion of extract as free run juice per press load and is faster and significantly more easier to clean. So a typical side bag 260hl press processes 55tns and turns around every 5.5 to 6 hours. This represents 9 tns/hr. The Della Toffola 240hl press processes 70-75tns and turns around in 3 hours delivering a median average of 24tn/hr. There is a subtle suggestion that the two or three additional hours being raised by competitors as being the significant problem for Della Toffola presses in respects to press bag change over times is arguably inconsequential to the more significant problems faced by side bag press operation cycle times, phenol and solids generation.
This all said the real story for press investments moving forward is somewhere very different. At a recent client meeting the question was asked, ‘are there any new developments on the DT pressing front’?. The Della Toffola presses provide an extract juice 60% lower in suspended solids to side bag presses for whites and red winemaking. The Della Toffola press best enables an inline continuous drain separation of juice intake with reduced solids loadings than any press. This dynamic is influencing the effectiveness of juice clarification, down-stream with type and scale of investment towards inline continuous floatation and inline high solids recovery/cross flow technology spend. ‘Spend’ being the operative word! – Reduce the solids loadings at the press extraction point and that translates to more bang for buck investment potential with high solids separation and in line continuous clarification technology.
There is a lot of new, well-proven exciting technologies that are being adopted these last years. The advantages of Della Toffola presses compared to side bag presses are very clear. The real benefit of a Della Toffola press investment is the more efficient adoption to new technologies at the front-end winery for clarification and separation technologies. It is in this space that payback is being focused on, and it is the central membrane press that is central to achieving more fluency with the far wider narrative of achieving better quality and or more effective winemaking in winery operations.
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