Leafy vegetables are alive when they are packed. They lose water through their leaves rather than releasing it from a cut face, and that single difference reverses what the pad is for. A meat pad takes liquid away; put the same specification under a head of lettuce and it will dry the pack out and speed up the wilting it was meant to prevent. This guide sets out the transpiration mechanism, what the pad actually does in a leafy pack, and how the requirement changes across the vegetable range.
1. Transpiration is not exudate
- The leaf surface is the route. Water leaves through the leaves, continuously and in vapour form, not as a pool of liquid.
- The pack starts dry. A meat pack begins with liquid to remove. A leafy pack begins with none, and the question is how much water stays in the air around the product.
- Both extremes fail. Free water sitting on the leaves is one problem; a headspace that is too dry is another. The pad sits between the two.
This is why a pad specified for meat, applied here, does harm rather than nothing.
2. What the pad is actually for here
- Taking free water, not all water. Condensation and liquid from cut stems have to go, because free water on a leaf surface is where decay starts.
- Leaving the atmosphere alone. The pack should stay humid. An oversized or over-absorbent pad pulls the pack dry and the leaves lose turgor.
- Being part of a pack design, not a substitute for one. The film's perforation and the pack's headspace do most of the work; the pad handles what the film cannot.
The atmosphere inside the pack — including the gases the produce itself produces — is a separate specification, and not something a pad is selected to change.
3. Choosing by category
| Category | How water is lost | What the pad does | Pad direction | Pack fit |
|---|---|---|---|---|
| Leafy greens | transpiration from the leaf surface, continuous | takes free water only; must not dry the headspace | thin, modest capacity, sized well inside the pack | perforated or breathable film; the pad supports the film |
| Root and tuber vegetables | slow transpiration, mostly condensation in the pack | handles condensation rather than product water | moderate, sized to the pack base | a firmer pack; the pad is not under load |
| Prepared and washed greens | transpiration plus surface water from washing | takes the wash water and the condensation | moderate, and fast take-up matters | sealed pack; the pad is the only route for free water |
| Cut and prepared vegetables | cut surfaces release cell fluid, which is a real liquid | behaves closer to a meat pad, but the load is smaller | moderate capacity, sized to the pack base | sealed pack, often with a firm base |
Directions rather than figures, because the pack, the film and the handling all change the answer. Where the same mechanism applies to the fruit side of the range, fruit absorbent pad covers it, and the combined range sits under fruit and vegetable preservation absorbent pads. The wider produce group is under produce absorbent pads.
4. Where leafy pack specifications go wrong
- Carrying a meat specification across. The pad is built to remove liquid, and in a leafy pack that is the wrong job.
- Choosing the largest pad available. More capacity here means a drier pack and faster water loss from the product.
- Ignoring the film. The pad cannot fix a pack whose film does not breathe; it will simply saturate and stop.
- Treating all vegetables as one category. Leafy greens, roots and cut vegetables lose water by different routes and at different rates.
FAQ
Why does a meat pad not work under leafy greens?
Because it is built to remove water, and leafy greens need a humid pack. Removing water from the headspace is the opposite of what the product needs.
Does the pad do anything useful here?
Yes — it takes free water, from condensation and cut stems. That is a real job, and it is a smaller one than in a meat pack.
Should the pad be as large as the pack?
Usually not. A pad sized well inside the pack takes free water without drying the atmosphere around the product.
What about prepared salads?
Those carry wash water as well, so the pad has more to do. It is still a moisture-balance job, not a drainage job.
Browse the range
Start from the vegetable absorbent pads range, or the wider fresh absorbent pads group. Send the product, the pack format and the film in use, and a pad can be matched before samples are issued.