The Physics of Snack Preservation
Three factors determine how long a snack product stays fresh in a can: moisture ingress, oxygen exposure, and mechanical protection. A composite paper can addresses all three: the spiral-wound body provides mechanical rigidity (crush resistance), the inner liner blocks moisture and oxygen (barrier function), and the sealed cap maintains the internal environment after opening (resealability).
Moisture: The Primary Staling Mechanism
For most dry snack foods, moisture gain is the primary cause of quality degradation. A potato chip that absorbs just 2% additional moisture by weight becomes perceptibly less crisp. At 5% moisture gain, it's noticeably stale. The moisture vapor transmission rate (MVTR) of the packaging determines how long it takes to reach these thresholds.
MVTR and shelf life relationship for a 73mm × 230mm chip can at 25°C, 50% RH:
| Liner Type | MVTR (g/m²/day) | Est. Shelf Life |
|---|---|---|
| Uncoated Kraft | 400–600 | <1 week |
| PE-coated (30μm) | 40–60 | 1–3 months |
| Metalized PET | 3–8 | 6–12 months |
| AL foil (7μm) | 0.5–2 | 12–18 months |
Oxygen: The Flavor Degrader
Oxygen reacts with fats and oils in snack products, causing rancidity — the "off" flavor that develops in nuts, chips, and other oil-containing snacks. A sealed composite can with an AL foil liner has oxygen permeability near zero (<0.01 cc/m²/day). The headspace air in the can is the primary oxygen source; it's typically about 10–15% of the can volume. For products with high unsaturated fat content (nuts, premium chips), nitrogen flushing — replacing the headspace air with nitrogen — extends shelf life by 3–6 months beyond passive barrier protection.
Mechanical Protection: The Hidden Value
In distribution, snack packaging endures: vertical compression (stacking in warehouses and trucks), impact (drops during handling), and vibration (transport). A composite can's spiral-wound paper body resists vertical compression up to approximately 80–100 kg (73mm diameter, 4-ply wall). A flexible pouch resists effectively zero. This is why chip can products have dramatically lower damage rates in e-commerce (<2%) compared to bagged products (8–15%).
For chip can preservation specifications and testing data, email support@kuzopacking.com or WhatsApp +86 153-0553-6396.