For compressed air that touches dough, egg wash or cream, you need at least dried air, then at the station a coalescing fine filter followed by an activated carbon filter, fitted as close to the nozzle as possible. The ISO 8573-1 class to reach is set station by station, with our technicians, the machine manufacturer and your HACCP plan. In a bakery and patisserie these stations are few and usually use less than 300 l/min in total, so there is no need to treat the whole network to the strictest level.
The air demand of the whole bakehouse is covered on our page on the compressor for bakeries and patisseries. The general principles of food contact, which apply across the food industry, are in our article on compressed air in contact with food. Here we apply them to the bakehouse and the pastry kitchen.
Which stations put air in contact with the dough?
Sort your stations into three families. This classification decides the filtration.
| Family | Bakery and patisserie examples | What the air touches |
|---|---|---|
| Direct contact | blowing out moulds just before filling, air pushing cream in a pneumatic piston injector without a diaphragm, airbrush on a cake | the product or the surface that receives it |
| Indirect contact | egg wash spray gun, release agent spray bar, bag opener blowing air before bagging | the sprayed product or the packaging |
| No contact | cylinders on dividers, moulders, sheeters and clippers | nothing, the air stays inside the machine |
On an injector or depositor, look at the diagram in the manual. On many models the air drives a piston or a diaphragm and never touches the cream. On others, the air pushes the contents of a hopper directly. The two cases do not call for the same filtration.
Why filter the air from a lubricated compressor?
Our compressors are oil-lubricated. The air leaving the screw element carries three contaminants:
- water, as vapour and then as droplets once the air cools in the pipes;
- particles, from the air drawn in and from the network;
- traces of oil, as aerosol and vapour.
On the K series, the built-in refrigerated dryer and filtration remove most of the water, particles and aerosols. That is a good base, but it is not yet air for food contact. The rest is added at the station. Our article on oil in compressed air explains where the oil comes from and how it is captured.
Which filtration chain at the point of use?
For a station with direct or indirect contact, the typical chain, in the order the air flows through it, is:
- A coalescing fine filter, which stops fine particles and droplets of oil and water.
- An activated carbon filter, which captures oil vapour and odours. It always goes after the coalescing filter, otherwise it saturates within a few days.
- A pressure regulator with gauge, set to the pressure given in the tool's manual.
- A clean hose, kept for that station only, and a nozzle or spray gun cleaned as the manual says.
Fine filters go as close as possible to the point of use, after the network: an old steel pipe can release rust downstream of the dryer. Our article on fine filters explains the role of each element.
How do you size the station filters?
A filter is chosen for a flow at a given pressure. If it is too small, the pressure drops at the nozzle and the element saturates faster.
Example of a pastry kitchen with two contact stations (guide values, to be replaced with those in your manuals):
- Egg wash spray gun: 80 l/min.
- Airbrush: 20 l/min.
- Blowing out moulds before filling, one nozzle: 100 l/min.
- Flow of the contact stations: 80 + 20 + 100 = 200 l/min.
- Safety margin of 25%: 200 × 1.25 = 250 l/min. The filters for these stations are chosen for at least 250 l/min at network pressure.
- Rest of the bakehouse with no contact (cylinders, bagging machine, blow gun in bursts): 200 l/min.
- Compressor total: 200 + 200 = 400 l/min, then × 1.25 = 500 l/min, then × 1.2 for expansion = 600 l/min.
The K 75 delivers 1,100 l/min at 8 bar with its dryer and filtration, so it covers everything. In a busier central production kitchen, the K 110 delivers 1.7 m³/min and the K 150 2.2 m³/min at 8 bar.
Which ISO 8573-1 class should you aim for?
An ISO 8573-1 class is written as three digits: particles, water, oil. The lower the number, the cleaner the air. There is no single class for bakeries: it depends on the station, the machine and your customers. The method:
- List the stations with direct contact, then those with indirect contact.
- Note the class required in each machine's manual, where it is given.
- Check what your HACCP plan and your customers' specifications require, for example a supermarket chain.
- Send us this list: our technicians set the class for each station with you, and the filtration that achieves it.
- Have the air tested at the station if your quality system requires it.
Our ISO 8573-1 air quality guide explains how to read each digit.
The mistakes that spoil air quality
- A compressor that sucks in flour. The dust it draws in clogs the intake filter and loads the oil. Install the compressor outside the bakehouse, as explained in our article flour, dust and the compressor air intake.
- The carbon filter before the coalescing filter. It soaks up liquid oil and stops capturing anything.
- Elements that are never changed. Write the fitting date on each filter and respect its manufacturer's replacement interval, even if the pressure drop still looks low.
- A forgotten drain. A coalescing filter collects oily condensate. Its drain must work, and the condensate must be collected for treatment.
- Blowing to clean. A blow gun on a floured worktop puts the flour back into the air, where it forms a combustible cloud and settles on the products. Use a vacuum instead.
For spraying, also read our article on egg wash and release agent spraying. Then list your contact stations in the configurator and send them with a quote request: we define the filtration for each station with you.
For your trade: Air compressor for bakeries, patisseries and viennoiserie.