MAP Film & Hit the Right O₂ and CO₂
Designs the film area
Passive MAP lets a respiring crop pull its own headspace to a steady-state O₂ and CO₂. Enter the produce, pack weight, temperature and film, and get the equilibrium gas mix, the required film permeance and area, and whether the pack lands in the safe window — anaerobic and high-CO₂ injury flagged.
Design the retail pack
Next: O₂ falls to 0% — below the ~1% fermentation floor, risking off-flavours. Increase the film O₂ permeance: switch toward PVC stretch wrap or enlarge the film to about 0.14 m² (or perforate), so O₂ holds near the 7.5% target.
Passive-MAP steady-state mass balance: at equilibrium the produce's O₂ consumption equals O₂ permeating in through the film, and CO₂ production equals CO₂ permeating out. Respiration scales with temperature (Q10≈2.5); film permeance rises more slowly (Q10≈1.4). A real pack also has free volume and a pull-down period — verify with a headspace analyser. Sources: Kader/Zagory 1989; UC-Davis Postharvest; Beaudry 2000.
MAP film design — key facts
- Steady-state rule
- O₂ consumed = O₂ permeating in
- Required OTR
- resp × wt × 24 ÷ (area × ΔO₂%/100)
- CO₂:O₂ film ratio (beta)
- ≈ 3–6 for polyolefin films
- Anaerobic floor
- O₂ below ~1% → fermentation
- Respiration Q10
- ≈ 2.5 per 10 °C
- Film permeance Q10
- ≈ 1.4 per 10 °C
- Air baseline
- 20.9% O₂, ~0.04% CO₂
- Privacy
- Runs in your browser; nothing uploaded
The film has to breathe at the same rate the crop does
Cut or whole, fresh produce keeps respiring after harvest — burning oxygen and releasing carbon dioxide. Seal it in a film and the headspace stops being air: O₂ drops, CO₂ climbs, until the gas crossing the film exactly balances what the produce uses. That balance point is the steady-state atmosphere, and modified atmosphere packaging is the art of choosing a film so that point lands where the commodity stores best — low enough O₂ and high enough CO₂ to slow respiration and decay, but never so low that the produce ferments.
This tool sizes that design. From the commodity's respiration rate (scaled to your storage temperature), the pack weight, the film's O₂ permeance and the film area, it solves the mass balance for the steady-state O₂ and CO₂, then tells you the required film permeance and the film area that would hit the recommended window. It flags the two failure modes that ruin a pack: oxygen falling below the fermentation floor, and carbon dioxide rising past the commodity's injury threshold. Pair it with the Cold-Chain Half-Cooling, Mixed-Load Compatibility and Milling Blend-to-Grade tools for a full post-harvest plan.
Recommended atmosphere and respiration by commodity
| Commodity | Group | Resp. O₂ (mL/kg·h, 5 °C) | Target O₂ (%) | Target CO₂ (%) | Note |
|---|---|---|---|---|---|
| Apple | Pome fruit | 4 | 2–3 | 1–3 | Low O2 / low CO2; CO2 injury above 5%. |
| Pear | Pome fruit | 5 | 2–3 | 0–1 | Very CO2-sensitive (core breakdown). |
| Banana | Tropical | 18 | 2–5 | 2–5 | Chilling-sensitive; keep ≥13 °C. |
| Mango | Tropical | 16 | 3–5 | 5–8 | Tolerates higher CO2. |
| Avocado | Tropical | 30 | 2–5 | 3–10 | High respiration; high CO2 tolerance. |
| Strawberry | Berry | 25 | 5–10 | 15–20 | High CO2 suppresses Botrytis. |
| Blueberry | Berry | 12 | 2–5 | 12–20 | High CO2 controls decay. |
| Raspberry | Berry | 30 | 5–10 | 15–20 | Very perishable; high CO2. |
| Table grape | Berry | 5 | 2–5 | 1–3 | SO2-sensitive; modest CO2. |
| Tomato (mature-green) | Fruit veg | 8 | 3–5 | 0–3 | Chilling-sensitive; low CO2. |
| Bell pepper | Fruit veg | 9 | 3–5 | 0–5 | Chilling-sensitive. |
| Cucumber | Fruit veg | 10 | 3–5 | 0–5 | Chilling-sensitive; keep ≥10 °C. |
| Lettuce (crisphead) | Leafy | 12 | 1–3 | 0–2 | CO2 injury (brown stain) above 2%. |
| Spinach | Leafy | 40 | 7–10 | 5–10 | Very high respiration. |
| Fresh-cut salad mix | Fresh-cut | 50 | 2–5 | 5–15 | Cutting doubles respiration. |
| Broccoli | Brassica | 35 | 1–2 | 5–10 | High CO2 holds green colour. |
| Cauliflower | Brassica | 16 | 2–5 | 2–5 | Off-odours under low O2. |
| Cabbage | Brassica | 6 | 3–5 | 5–7 | Stores well; modest MAP benefit. |
| Mushroom | Fungi | 40 | 3–5 | 5–15 | Very high respiration; needs high OTR film. |
| Asparagus | Stem | 45 | 7–14 | 5–10 | Extremely high respiration. |
| Green bean | Legume veg | 20 | 2–3 | 4–7 | Chilling-sensitive. |
| Carrot (topped) | Root | 4 | 5–5 | 3–4 | Low respiration; little MAP benefit. |
| Potato | Tuber | 3 | 5–5 | 0–0 | MAP not recommended (sweetening, CO2 injury). |
| Onion (dry) | Bulb | 3 | 1–2 | 0–10 | Needs dry, ventilated pack. |
Recommended O₂/CO₂ ranges and respiration adapted from UC-Davis Postharvest Technology Center recommendations and Kader, Zagory & Kerbel (1989). Respiration is normalised to 5 °C and scaled with a Q10 of about 2.5.
Packaging films — O₂ permeance and CO₂:O₂ ratio
| Film | Thickness (µm) | O₂ permeance OTR (mL/m²·day·atm) | CO₂:O₂ (beta) | Use |
|---|---|---|---|---|
| LDPE 25 µm | 25 | 7,800 | 4 | Common, moderate OTR. |
| LDPE 50 µm | 50 | 3,900 | 4 | Lower OTR (thicker). |
| OPP 25 µm | 25 | 2,300 | 4.5 | Low OTR; clear & stiff. |
| Micro-perforated OPP | 30 | 60,000 | 1 | Perforations dominate; beta→1. |
| PE/EVOH coex | 40 | 600 | 4 | High barrier; very low OTR. |
| PVC stretch wrap | 12 | 16,000 | 5 | High OTR; retail overwrap. |
| PLA 25 µm | 25 | 5,500 | 6 | Compostable; high CO2 transfer. |
| Breathable OMPP 30 µm | 30 | 11,000 | 3.5 | High-respiration produce. |
Film O₂ permeance and CO₂:O₂ ratio approximated at 5 °C from Exama et al. (1993), Beaudry (2000) and supplier data sheets. Permeance rises with temperature (Q10 ≈ 1.4).
How to design the film in five steps
- 1. Pick the commodity. The tool loads its respiration rate and recommended O₂/CO₂ window from the postharvest tables.
- 2. Describe the pack. Enter the produce weight, the storage temperature and the total film area in contact with the headspace.
- 3. Choose a film. Select a film type; its O₂ permeance and CO₂:O₂ ratio are applied at your temperature.
- 4. Read the equilibrium. The O₂–CO₂ box shows the steady-state point and whether it sits inside the green safe window.
- 5. Tune to target. Adjust the film area or type toward the displayed required permeance until the point lands in the window — anaerobic or high-CO₂ warnings clear.
Frequently Asked Questions
How do I calculate the right MAP film for fresh produce?+
At steady state the oxygen your produce consumes equals the oxygen permeating in through the film, and the carbon dioxide it produces equals the carbon dioxide permeating out. So the required film O₂ permeance is OTR = respiration × weight × 24 ÷ (area × (20.9 − target O₂%)/100). Enter the commodity, pack weight, temperature, film type and film area and the tool returns the steady-state O₂/CO₂, the required permeance and the film area that lands inside the safe window.
What O₂ and CO₂ levels should the package reach?+
It depends on the commodity. Strawberries want roughly 5–10% O₂ with 15–20% CO₂ to suppress Botrytis; apples want 2–3% O₂ and under 3% CO₂; crisphead lettuce wants 1–3% O₂ and under 2% CO₂ because it browns above that. The calculator stores the UC-Davis / Kader recommended ranges for each commodity and draws them as the green safe window your steady-state point should fall inside.
What is equilibrium modified atmosphere packaging (EMAP)?+
EMAP is passive MAP where you do not flush a gas mix — you simply seal the respiring produce in a film whose permeability lets the headspace drift to a steady state on its own. The produce pulls O₂ down and pushes CO₂ up until the gas exchange through the film balances respiration. Choosing the film permeance and area so that equilibrium lands in the safe window is exactly what this tool sizes.
What happens if the film O₂ permeance is too low?+
Oxygen falls too far. Below about 1% O₂ the produce switches to anaerobic respiration, fermenting and producing ethanol and acetaldehyde — off-flavours and off-odours. The tool flags this as an anaerobic-risk verdict and tells you to raise the film O₂ permeance, enlarge the film area, or perforate, so O₂ holds near the commodity's target.
What if CO₂ builds up too high?+
Many commodities suffer CO₂ injury above their tolerance — apples and pears get internal browning, lettuce gets brown stain. Because most films pass CO₂ several times faster than O₂ (a CO₂:O₂ permeability ratio, beta, of about 3–6), CO₂ is usually controlled when O₂ is right, but high-respiration produce in a low-CO₂-transfer film can still over-accumulate. The tool flags a high-CO₂ verdict and suggests a higher-beta film or a larger area.
How does temperature change the design?+
Respiration roughly multiplies by 2.5 for every 10 °C rise (a Q10 of about 2.5), while film permeability rises more slowly (Q10 around 1.4). So a pack that sits perfectly at 5 °C can go anaerobic if the cold chain breaks and the produce warms — respiration outruns the film. The calculator scales both with temperature, which is why warming a pack pulls its steady-state point toward low O₂ / high CO₂.
How big is the film area on a typical retail pack?+
Total film surface area is what matters, not just the top window. A 20 × 15 cm pillow pack has roughly 0.06 m² of film; a small punnet lidded with stretch film might be 0.03–0.04 m²; a large salad bag can exceed 0.1 m². Enter the total film area in contact with the headspace — both faces of a pillow pack count.
What does OTR (oxygen transmission rate) mean?+
OTR is the film's oxygen permeance: how many millilitres of O₂ cross one square metre of film per day per atmosphere of partial-pressure difference, written mL/(m²·day·atm). A 25 µm LDPE film is around 7,800; a high-barrier EVOH coextrusion is a few hundred; a micro-perforated film is tens of thousands because the holes dominate. The tool reports the OTR you need and the closest stock film.
Is 5% O₂ and 16% CO₂ good for strawberries?+
Yes — that is squarely in the recommended 5–10% O₂, 15–20% CO₂ window for strawberries, where elevated CO₂ slows grey mould (Botrytis) and the moderate O₂ keeps respiration low without fermentation. If your pack settles there the tool returns an ideal verdict; if it drifts low on O₂ you would loosen the film, and if CO₂ runs over 20% you would vent it.
Can I use the same film for every commodity?+
No. A low-respiration apple needs a low-permeance film, while a high-respiration commodity like mushroom, spinach or fresh-cut salad needs a high-permeance or micro-perforated film, or it goes anaerobic almost immediately. The calculator's respiration table and film catalogue let you match the film to the commodity rather than guessing.
Does the pack reach steady state instantly?+
No — there is a pull-down period of hours to a day or two while the headspace drifts from air toward equilibrium, set by the free gas volume and the respiration rate. This tool computes the steady-state target you are designing for; the on-screen curves show the approach. For perishable, high-respiration produce equilibrium is reached fast; for low-respiration produce it is slower.
Why does the tool also show a required film area?+
Because you usually cannot buy a film at the exact permeance you need, the easier lever is area. For a chosen film the tool solves for the film area that makes O₂ land on the commodity target, so you can resize the pack instead of sourcing a new film. It also names the closest stock film if you would rather change material.
Does MAP replace refrigeration?+
No. MAP slows respiration and decay on top of the cold chain; it does not substitute for it. A modified atmosphere at the wrong temperature still spoils, and warming the pack can push it anaerobic as respiration outpaces the film. Always design the film for the actual storage temperature and keep the cold chain intact.