U.S. Food & Drug Administration
Center for
Food
Safety &
Applied
Nutrition
Bacteriological
Analytical
Manual
Online
January 2001
|
|
Chapter 22B
Examination of Containers for Integrity
II. Examination of Glass Containers for Integrity
Authors
(Return to Table of Contents)
Almost all low-acid foods packaged in glass containers are sealed with
vacuum-type closures. Currently 4 types of vacuum closures are widely used on
low-acid food products: LT (lug-type twist) cap, PT (press-on twist-off) cap,
pyr-off (side seal) cap, and CT (continuous thread) screw cap (Fig. 25).
Packers' tests and examinations to ensure a reliable hermetic seal of
containers are required by 21 CFR 113.60 (a) (2) and (3).
|
|
Vacuum Twist Lug Finish |
Vacuum Pry Off Finish |
|
|
Press On Twist Off Finish |
Continuous Thread Finish |
Figure 25. Types of vacuum closures and glass finishes.
- Visual examination for closure and glass defects (for definition of terms, see the
glossary section of this chapter)
cap tilt
crushed lug
chipped glass finish
cut-through
cocked cap
stripped cap
cracked glass finish
- Seal integrity examination
- Vacuum. Use standard open-closed type of vacuum gauge or USG No.
12118 gauge with both vacuum and pressure scales (Fig. 26). Wet
rubber gasket on piercing device with water. Shake off excess water.
Puncture closure, using piercing needle attached to vacuum gauge.
Read and record vacuum in inches (0-30 inches), or pressure (0-15
psi).
Figure 26. Vacuum gauge for seal integrity examination.
- Removal torque (cam-off) for PT or LT type closures (Fig. 27).
Properly secure jar on torque meter. Ease closures off in smooth,
continuous motion rather than rapid, jerking motion. Use one hand to
twist cap counterclockwise to open cap from sealed jar while
avoiding any downward pressure on cap. Record maximum torque in
inch-pounds required to open cap.
Figure 27. Torque meter.
- Security values (lug tension) on lug-type twist cap (Fig. 28). Make
vertical line on cap and corresponding line on container wall with
marking pen. Turn closure counterclockwise just until vacuum is
broken. Reapply closure to container just until gasket compound
touches glass finish and closure lug touches glass thread (or until
closure is at 2 inch-pound reapplication torque to achieve
uniformity for application). Measure and record, in 1/16 inch
increments, distance in front of vertical lines that were made
before opening. Security is considered positive if line on cap is to
right of line on container, and negative if line on cap is to left
of line on container.
Figure 28. Security measurement for lug type twist closure.
- Pull-up (lug position) for lug-type twist cap (Fig. 29). Mark
vertical neck ring seam on glass finish. Measure distance from this
vertical line, in 1/16 inch increments, to leading edge of cap lug
position nearest it. Record lug position measurements made on right
side of vertical neck ring seam (as analyst looks at package) as
positive (+) and those to left side of parting line as negative (-).
Figure 29. Pull-up lug position of LTD measurement.
Hypertext Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998. Chapter 22.
*Authors: Rong C. Lin, Paul H. King, and Melvin R. Johnston
Top
B A M |
B A M Media |
B A M Reagents |
Bad Bug Book
Foods Home |
FDA Home |
Search/Subject Index |
Disclaimers & Privacy Policy
|
Accessibility/Help
Hypertext updated by bap/kwg/cjm 2001-OCT-24