A vacuum pack that's tight when it comes out of the machine and slack the next morning has one of two problems: air is getting in, or gas is coming out of the product. Air gets in through a channel in the seal or a pinhole in the film. Gas comes from bacteria. The pack itself will usually tell you which, if you know where to look.
How do I tell what's causing it?
| What you see |
Most likely cause |
Go to |
| Slack, loosest near the seal end |
Leak in the seal |
Seal leaks |
| Slack, a small air pocket by a bone or edge |
Puncture |
Punctures |
| Slack, but you can't see why |
Pinhole or seal leak |
The water test |
| Puffed up, pouch tight like a balloon |
Gas from spoilage |
Blown packs |
Seal leaks
The seal looks complete but there's a channel through it, usually from fat or liquid that was on the film when it sealed, or a crease across the bar. Air tracks through slowly, so the pack holds for an hour and goes by morning. Look along the seal with the pack held up to the light. A thin line or a bubble running through the seal band is the leak.
The fix is in how the pouch is loaded: a folded cuff to keep the seal area clean, the pouch flat on the bar, the seal time right for the film. The sealing troubleshooting guide goes through each of these.
Punctures
Under full vacuum the outside air presses the film onto the product hard, and anything sharp goes through it. Bone tips, chine bones, fish fins, the corner of a frozen block, crab shell. You'll usually see the air collecting around the point that did it.
- Cover sharp points with a folded square of greaseproof paper or a bone guard.
- Drop the vacuum to around 95% for product going out in a day or two.
- Go up a pouch size so the film drapes over the bone instead of stretching.
- For product that keeps beating 65 micron, use the 130 micron pouch, which is twice as thick.
The bone-in guide covers these in order of cost. Never vacuum pack product that's already frozen. Hard frozen edges cut film from the inside.
The water test
If you can't see where the air's getting in, put the loose pack in a sink of water and press it gently. A stream of small bubbles shows you the hole. Bubbles from the seal band mean a seal problem. Bubbles from the body of the pouch mean a puncture or a pinhole. Do this on a pack you're going to discard anyway.
Blown packs
A pack that's swollen rather than slack has gas inside it. That gas came from bacteria growing in the product. It's a spoilage sign, so don't repack it and don't open it near other food. Throw it away and look at the chain behind it: product temperature at packing, fridge temperature, and the date on the label. The food safety guide sets out the 10-day rule and the controlling factors that allow longer.
What should I do with a pack that's gone loose?
Treat it as a failed pack. The use-by date on the label assumed a sound vacuum. If you find it at the morning check and it's been in the chiller the whole time, most food businesses repack raw product straight away in a fresh pouch and keep the original date. A pack found loose in a customer's fridge, or one of unknown history, should be discarded. Your HACCP plan should say which, so staff don't have to decide on the day.
Does the pouch ever cause it?
Rarely, but it's worth ruling out. All our clear pouches are the same PA/PE co-extruded film. Thickness changes puncture resistance, not the barrier, so a sound 65 micron pack holds vacuum as well as a 130 micron one. If you're seeing leakers across several products and none of the causes above fits, call us with the size, the order date and a photo of the failed seal.
Losing packs on one product? Tell us what it is when you request a free sample pack and we'll include a couple of 130 micron pouches to test against it.
