How Does Bottom End Design Affect Canned Food Shelf Life?

1. Why does the can bottom affect the shelf life of canned food?

In commercial thermal sterilization (such as 121℃/15 PSI steam or water bath sterilization), the pressure in the can, the temperature gradient, and the expansion of the food will cause stress concentration on the can structure. If the food can bottom ends are not well designed, it is easy to bulge, lose roundness, develop double seam stress abnormality or coating damage, which will affect vacuum maintenance, metal corrosion protection, and microbial safety, thereby shortening the shelf life. On the contrary, structural optimization can significantly improve pressure resistance, sealing stability, and long-term storage reliability.

2. Bottom geometry and pressure resistance: an anti-bulging bottom means sealing

Common food can bottoms use concave, stepped reinforcement ring (bead), spherical or reverse arch geometry, the purpose is to:

Disperse the internal pressure during heat sterilization to the circumference to improve the ability to resist “bulging bottom”;

Allow limited elastic recovery during the vacuum cooling stage to avoid metal fatigue cracks.

Maintain balanced support under stacking pressure.

Insufficient pressure resistance causes permanent expansion of the bottom, which will stretch the double-sealed area and potentially leak, thereby destroying the sterile barrier.

3. Double-sealed compatibility: The matching of the food can top and bottom ends structures is critical

The shelf life really depends on the sealing integrity of the whole can. The bottom seal (body hook + cover hook + sealant) must reach the designed compression and overlap rate; if the bottom film thickness, flange width or coating slip coefficient does not match, it may cause “false seal” and “microchannel”, and micro-oxygen will enter and cause corruption, browning, or bulging of the can. When designing, the top and bottom of food and beverage cans need to be evaluated as a complete system, not an isolated component.

4. Inner coating and corrosion life

Acids, salts, and sulfides in food will slowly corrode metals; the bottom is most likely to accumulate heaviness, precipitation, or salt precipitation, and the risk of corrosion is high.

Epoxy phenolic, BPA-free composite, or special acid-resistant paint suitable for the type of food should be selected.

Acidic materials such as tomatoes and fruits, and vegetables need to strengthen the acid-resistant system; high-protein brine for meat needs to be chlorine-resistant.

Once pitting and perforation occur, the can loses its seal and the shelf life ends.

5. Heat transfer and process consistency

Thermal sterilization relies on “reaching and maintaining the target F value”. The bottom metal thickness, molding shape, and inner liquid circulation path will affect heat penetration:

When the bottom is deep and thick, local cold spots are likely to appear in the bottom corner area.

It is necessary to cooperate with stirring, rotating, or swinging sterilizers to ensure heat distribution.

When developing the process, the temperature probe should be arranged at the “coldest point” of the bottom of the can for verification.

Insufficient sterilization = residual microorganisms = shortened shelf life.

6. Stacking, transportation, and drop impact

When the storage cycle is long, the weight of the pallet stack is concentrated on the contact surface of the can bottom. The ribbed bottom/stacked bottom design can reduce local stress; TFS or thin aluminum specifications need to be compensated by beads. Micro pits caused by transportation impact may also damage the coating or induce delayed corrosion.

7. Top and bottom systems of food and beverage cans: top and bottom synergistically extend shelf life

The top and the bottom must have matching materials, thickness grading, coating compatibility, and unified sealing parameters; sterilization heat curve, vacuum/nitrogen filling, and filling head space directly affect the force balance at both ends. Well-designed top and bottom sets of food and beverage cans can:

Maintain long-term vacuum or moderate internal pressure.

Reduce transportation bulging and denting.

Reduce metal migration and corrosion failure.

Stabilize shelf life and improve the can opening experience.

8. Worunda Metal Packaging: Professional manufacturing of food and beverage can tops and bottoms

Worunda Metal Packaging focuses on the research and development, and manufacturing of food and beverage can tops and bottoms, providing high-strength, corrosion-resistant, and batch-traceable metal closure solutions for global canning plants.

Product models cover: 153mm tomato sauce can bottom, 50mm beverage can bottom TFS, 73mm fruit can top, 99mm tomato sauce can bottom, etc.; support customized diameter, material (tinplate/TFS/aluminum), coating system and sealing parameters.

Structural design focus: heat-resistant sterilization and anti-drum bottom geometry, reinforcement ring anti-stacking, food-compatible inner coating, vacuum retention sealant; matching with easy-pull tops to build a complete canning system.

Quality and compliance: The factory has passed the food contact material safety certification. Batch testing covers canning pressure resistance, sealing tightness, coating adhesion, and salt spray corrosion. And meets export-grade processing standards.

Results: Help customers improve canning yield, reduce the risk of can bulging returns, extend product shelf life, and enhance brand reputation.

If you need sample evaluation, can bottom structure selection, or crimping technical parameter support, please contact us.

Заключение

The can bottom is not simply “sealing a piece of metal plate”. It is directly involved in the management of pressure resistance, sealing, corrosion protection, and thermal process stability. The real long shelf life comes from “food formula + sterilization process + crimping quality + food and beverage can top and bottom structure coordination”. Cooperating with manufacturers with engineering experience and food certification qualifications (such as Worunda Metal Packaging) can significantly reduce the risk of failure and ensure a stable product launch cycle.