Container package having improved seal

A retortable container package comprising:

• a container including a finish portion that terminates in a circular lip, a taper is formed on an inboard side of the finish portion and merges into the lip, the taper in transverse cross section forms an angle of 6° to 14° from vertical;
• and
• a composite closure capable of being applied to the container, the closure including:
• a circular skirt;
• a disk-like insert including a peripheral bead, a raised channel inboard of the peripheral bead, and a circular center portion inboard of the channel;
• the raised channel including an outer wall, a substantially flat top portion, and an inner wall sloped at approximately the same angle as the taper angle;
• and
• a sealant disposed in the channel, the sealant being partially deformed upon application of the closure onto the container such that the sealant forms a seal between the closure and each of (i) an outer wall of the finish portion proximate the lip, (ii) the lip, and (iii) the taper;
• whereby after retorting, the seal between the finish portion taper and the channel inner wall is enhanced by the contraction of the finish portion diameter.