There are 3 ways for settling grapes juice prior to fermentation: flotation, cold settling, running trough a centrifuge. Today we’ll talk about flotation vs cold settling.
Flotation is the rapid process of juice clarification using nitrogen and gelatine. Juice cold settling is a clarification method when juice is cooled down to 2-3 *C and after few days is racked of lees.
In the following chart we have a scenario during first 15 days of vintage when we’re crushing white grapes. We can see the number of tanks used for cold settling vs flotation.
For cold settling, after first 3 days of crushing we have 5 tanks full with cold juice and waiting to be racked of lees. In the next couple days we need more men-power for racking and cleaning those 5 tanks.
If we do flotation, the workload is steady, we have only couple tanks with juice for clarification and next day tanks are empty and ready for the new juice. Racking and rinsing couple tanks can be done in 4 hours by one person.
In case of cold settling we need 2 cellar workers every 3-4 days to do the racking and cleaning the tanks in short period of time (usually one day).
- rapid method (can be done right away after pressing and the juice can be inoculated in same day)
- low cost (low energy consumption – only the pump build-in on flotation unit)
- can improve the juices from bad quality grapes (an easy method to get rid of mold)
- low cost method for low cost juices/low quality juices
- saving tank space (the process can take place in one or 2 tanks for all vintage period, clarified juice can be racked in fermentation tanks after couple hours)
- juice doesn’t lose any tartaric acid
- after racking, tanks need only a rinse and are ready for the next flotation cycle
- after settling we have less amount of lees
- losses are smaller (up to 3-5%)
- need a flotation unit
- use some enological materials such as: enzymes, gelatine, siligel, bentonite
- use of nitrogen (for 20000L of juice is consuming 1/4 of nitrogen cylinder – approx 10 NL/min)
- need one person to run and monitor the unit
- is not recommended to be use on high quality/aromatic juices
- if the amount of nitrogen is not proper managed, lots of foam is created and is hard to deal with (it’s not pumpable).
- use less enological material (only enzymes)
- require less men-power
- it is a gentile process (recommended for high quality juices)
- no foam creating
- it is a long process (few days for settling plus 1-2 days for warming the juice)
- use lot of energy (need energy for cooling, after racking need energy for warming the juice prior to fermentation)
- takes lot of tank space (for few days the tanks are occupied with cold juice for settling, at one point you can have 10 tanks on cold settling for a week)
- during cold settling the TA may drop with 0.5 – 1 g/L tartaric acid
- after racking, the tanks needs proper cleaning (caustic, citric washing to get rid of tartrates built on walls)
- lot of lees result after racking (losses are higher, up to 10% in some cases)