The most common method is T-peel testing according to ASTM F88 or similar standards. You cut 15mm-wide strips of the retorted pouch, place the two tails in a tensile tester's grips, and pull them apart at 200–300 mm/min. However, retort packaging requires two critical extra steps: (1) test both before and after retort to measure retention, and (2) test in both directions — with the pouch seam and across it — because delamination often starts at the sealed edges. Some labs also perform a "heat creep" test under constant load at 120°C to simulate real-world failure modes that a standard T-peel cannot reveal.

https://www.sinstarsl.com/bond-strength-in-retort-packaging-can-solvent-free-qualify

Retort causes three things to happen. First, heat softens the adhesive layer, reducing its internal cohesion. Second, moisture penetrates the edges of the laminate and hydrolyzes certain adhesive chemistries (especially polyester-based polyurethanes). Third, different materials expand at different rates — aluminum foil expands very little, while polypropylene expands significantly. That thermal expansion mismatch creates shear stress at the interface. A well-formulated retort-grade adhesive will lose only 10–25% of its initial bond strength after retort. A poor adhesive can lose 70% or more.

https://www.sinstarsl.com/bond-strength-in-retort-packaging-can-solvent-free-qualify