Tamper-Evident Seal

Many jarred products carry two separate devices that look similar but do very different jobs. A tamper-evident seal is a security feature that proves the package has not been opened since manufacture. A freshness button — the pop-up disc on the lid of many salsas, sauces, and vacuum-packed jarred foods — is a vacuum indicator; it shows that the headspace was evacuated at the packing facility, but it is not engineered to resist being reset and offers no proof against later opening. Treat the two independently: on most commercial jars a button that lies flush (depressed) signals intact vacuum, while a popped or domed button signals that vacuum has been lost. A depressed button under an unbroken shrink band means the jar left the factory sealed; a popped button under an intact shrink band means the same jar has lost vacuum since packing (age or temperature abuse); a depressed button under a torn or loose shrink band is the suspicious combination — the package was almost certainly opened and resealed — and should be returned.

The seal you can use is dictated by the container, not the product. Induction liners carry an aluminum foil face that the electromagnetic field actually heats; the molten polymer beneath the foil is what bonds to a continuous, flat bottle mouth under a properly torqued cap. The container itself need not be conductive — glass, PET, and HDPE all bond fine — but the mouth must be smooth and the cap must press the liner firmly and evenly against it. Shrink bands work on almost any rigid container — glass, PET, HDPE, metal — but they are decorative and evidentiary, with no barrier function. Breakaway rings require a cap mold designed with a perforated bridge. Tear-notch pouches need a film with machine-direction scoring; not every pouch stock accepts a clean tear. Before specifying a seal for a product, confirm container compatibility with the manufacturer and run a small pilot through your actual capping or filling line.

Sequentially numbered pull-tight seals and tear-strip pouches with lot codes turn a packaging step into a chain-of-custody record. The number on the seal applied to a catering tote, evidence bag, or delivery container is written onto the same HACCP, manifest, or FSMA Section 204 traceability record as the product lot, the employee who applied it, and the time of sealing. A torn seal with the correct number proves the tote was opened in the expected way; a missing or out-of-sequence number flags an undocumented access and triggers an investigation. For institutional, school, and food-bank shipments this practice has become standard, and it is the cheapest form of traceability a kitchen can adopt.