Coffee is one of the few products that fights back after you seal it. Roasted beans release carbon dioxide for three to seven days, and if that gas has nowhere to go, your bag inflates like a pillow, your case stacks badly, and your retailer sends photos.
Everything specific about coffee packaging follows from that one fact.
Freshly roasted coffee is still alive
During roasting, beans build up CO2 inside the cell structure. After cooling, that gas keeps diffusing out. A bag sealed two hours after roasting will be tight and firm by the next morning and rock hard by day three.
There are three ways to handle it: let the coffee rest before packing, install a one-way valve, or pack with a controlled flush and accept some inflation. Most roasters do the first and the second together.
Valve or no valve
A degassing valve is a small one-way membrane that lets CO2 out and keeps oxygen from coming in. It costs a few cents, it changes the bag structure, and it changes the machine, because the valve has to be applied in the right position without creasing the film around it.
Without a valve, you have three options and all of them are worse: pack stale coffee, pack under nitrogen and let the bag balloon anyway, or pack and then puncture, which nobody does twice.
For whole bean in 250 g to 1 kg bags, a valve is close to mandatory. For ground coffee in small sachets, degassing is faster and the bag is small enough that inflation is tolerable, so many roasters skip it.
Bag styles that work for coffee
- Side gusset bag with valve – the traditional retail look, needs a VFFS with a gusset former or a premade pouch machine
- Flat bottom bag – best shelf presence, almost always premade, holds shape well after opening
- Stand-up pouch with zipper and valve – the craft roaster standard, premade only in practice
- Tin tie or paper bag – for very small roasters, usually hand-filled, and a poor fit for automation
- Bulk 5 to 25 kg – woven or laminated sacks, linear weighing, no valve
The bag choice drives the machine choice more than the other way around. If you want a flat bottom bag with a valve and a zipper, you want a premade pouch machine. If you want a 1 kg side gusset at 60 bags a minute, you want a VFFS with a gusset attachment. Our pouch vs VFFS comparison works through the cost side of that decision.
Fill weight is harder than it looks
Coffee density changes with roast level, bean origin, and how long it has rested. A dark roast fills a 250 g bag at a different volume than a light roast, and the same coffee packed on Monday and Friday behaves differently as it degasses.
Two practical consequences. First, use a multihead weigher with a small hopper and gentle feed if you are packing whole bean at retail accuracy, because a 1 g error on a 250 g bag is 0.4 percent and your margin is thinner than that. Second, re-check your fill volume whenever you change origin or roast, not just weight. A volumetric filler set for last month’s coffee will overfill or underfill the bag and change its shape.
Net content rules matter here. Most markets allow a small negative tolerance on average but require that no individual pack falls below a defined limit. A weigher with a narrow spread is cheaper than the fines.
Oil and fines on the seal
Coffee leaves oil on everything, and ground coffee leaves fines in the seal zone. Both cause channel leaks that only appear when the bag is squeezed in a case.
The fixes are mechanical, not chemical: a product guard that keeps the fill stream centred, a short air purge at the seal zone, and a jaw cleaning routine at every break. Dark roasts are worse than light roasts, and ground is worse than whole bean.
Nitrogen: what it does and does not do
Flushing displaces oxygen and slows staling. On a VFFS, a well-positioned lance can get residual oxygen below 2 percent in a 250 g bag; on a pouch machine, the same result needs a properly sealed fill station and a decent dwell.
It does not stop degassing, it does not fix a leaking valve, and it does not make stale coffee fresh. If your oxygen readings are inconsistent, check the seal and the valve before you increase gas flow.
Output, realistically
A single VFFS with a 10-head weigher on 250 g bags typically runs 35 to 55 bags a minute with a valve applicator, slower than the same machine on snacks because of the valve, the gusset, and the film stiffness. A four-station premade pouch machine runs 25 to 40 pouches a minute. Plan your capacity on the lower number and you will not be disappointed in week two.
For a roastery doing 200 kg a day into 250 g bags, that is 800 bags, or roughly two and a half hours at 35 a minute. The machine is not the constraint; the roaster and the packing labour usually are.
Frequently asked questions
Do I need a valve on every bag?
For retail whole bean, effectively yes. For ground coffee in small sachets or bulk catering packs, often no. The test is simple: seal a bag, leave it 24 hours, and see whether it stands up on its own.
How long should coffee rest before packing?
Most roasters rest 12 to 48 hours before packing, which reduces the gas load enough that a valve can handle the rest. Packing immediately after roasting is what makes bags balloon.
Why is my fill weight drifting through the day?
Product settling and degassing change bulk density. Re-weigh the target every few hours on a new roast, and always after changing origin.
Can I run valves on a VFFS?
Yes, with a valve applicator that applies and seals the valve to the film before forming. It adds cost and slows the machine, and it needs careful setup to avoid creasing the film around the valve.
Related reading: VFFS machines for coffee and premade pouch machines.