Incubation Method

A. Introduction 

Non-destructiveTo determine whether a package has lost hermetic barrier by holding containers at an ideal temperature for sufficient time to ensure microbial growth.Not applicableOff-line> $10,000

B. Operation 

Hermetic integrity is the condition that bars entry of microorganisms into a package. Growth of microorganisms indicates either insufficient processing or loss of hermetic barrier. Growth may be observed as gas formation, change in pH, growth of viable organisms, or changes in the appearance of food.

  • Insulated box or room to serve as an incubator
  • Heater with thermostat
  • Storage racks
  • Recording thermometer
  • Temperature recording charts
  • Knife, scissors
  • pH meter
  • Inoculating loop and flame
  • Sterile culture dishes and tubes, and culture media
  1. Obtain representative sample packages containing processed product.
  2. Inspect all samples visually for defects.
  3. Place packages in incubator for recommended period of time at recommended temperature.
    Products stored in incubator at 95oF (35oC)
    • FDA products - 14 days
    • USDA products - 10 days
    Products stored in warehouse
    • 85-95oF (29-35oC) 30 days 
    • 70-85oF (21-29oC) 60 days 
    • 60-70F (16-21oC) 90 days
  4. Visually inspect packages for evidence of spoilage.
  5. Open and inspect all (or some) packages for visible signs of microbial growth, aroma, and change in pH.
  6. Never taste incubated product if spoilage may have occurred. Aseptically obtain product samples to culture microbiologically and confirm cause of spoilage.
  7. Conduct appropriate integrity test on package to identify presence or absence of microleaks.
  8. Dispose of product safely.
  9. Autoclave any product or packages showing spoilage before disposal.

Positive

Spoilage has occurred and is evident as swelling, putrefactive odor, change in product pH from normal, or change in appearance.

Negative

Spoilage has not occurred.

False positive

Chemical reaction or enzymatic activities alter product characteristics without microbial activity.

False negative

Should not occur because this would be commercial sterility.

C. Application 

PACKAGE TYPES AND DEFECTS

 PACKAGE TYPE
DEFECTSFlexible PouchSemi-rigid and Rigid plastic containerPlastic Can (Double-seam Metal End)Paperboard
Abrasion
Corner Dent   
Crushed 
Cut (Fracture)
Delamination 
Double Seam Defects*   
Flexcracks 
Foreign Matter Inclusion  
Gels  
Hotfold   
Label Foldover   
Leaker   
Leaker (Channel) 
Leaker (Corner)   
Leaker (Notch)   
Leaker (Perforation)   
Leaker (Pulltab)   
Leaker (Seal)   
Loose Flap or Ear   
Malformed  
Puncture (Pinhole)
Seal Defects (Blister)   
Seal Defects (Blocked)   
Seal Defects (Burnt)   
Seal Defects (Compressed)   
Seal Defects (Contaminated)  
Seal Defects (Convolution/Embossing)   
Seal Defects (Creep)   
Seal Defects (Crooked)   
Seal Defects (Incomplete)   
Seal Defects (Misaligned/Deformed)  
Seal Defects (Nonbonding/Weak)   
Seal Defects (Plastic Lumps)   
Seal Defects (Seal-width Variation)   
Seal Defects (Stringy)   
Seal Defects (Uneven Impression)   
Seal Defects (Uneven Juncture)   
Seal Defects (Wrinkle)  
Swell (Swollen Package)
Waffling   

D. Source 

Not applicableARNDT., G.W. JR. 1998. Chapter 22C Examination of Flexible and Semirigid Food Containers for Integrity. FDA Bacteriological Analytical Manual (8th Ed)

21 CFR 113.60. Containers. Government Printing Office (GPO), Superintendent of Documents, New Orders, P.O. Box 371954, Pittsburgh, PA 15250-7954.

9 CFR 318.301 - Containers and closures. Government Printing Office (GPO), Superintendent of Documents, New Orders, P.O. Box 371954, Pittsburgh, PA 15250-7954.

MIL-PRF-44073E. http://www.troopsupport.dla.mil/subs/support/specs/pcrs/mre/44073.pdf