Title page for ETD etd-08312000-14550031

Type of Document Master's Thesis
Author Gibney IV, Matthew Joseph
Author's Email Address mgibney@vt.edu
URN etd-08312000-14550031
Title Predicting Package Defects: Quantification of Critical Leak Size
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Marcy, Joseph E. Committee Chair
Blakistone, Barbara A. Committee Member
Davis, Richey M. Committee Member
Hackney, Cameron Raj Committee Member
  • leakers
  • hermetic seal
  • microbial ingress
  • package sterility
  • threshold leak size
Date of Defense 2000-06-30
Availability unrestricted
Threshold leak sizes and leak rates were calculated for a number of liquid food products exhibiting a wide range of surface tension and viscosity values. From this data, one can see that mathematically, under typical pressure differentials generated in food packages (less than or equal to ±34.5 kPa), a leak will never start through a 2 μm defect. The calculated leak rates were compared to calculated evaporation rates. The evaporation rate exceeds the leak rate at lower sized microholes (2, and 5 μm diameter) under typical pressure differentials found in food packages. If the liquid, typically aqueous in food products, is evaporating off faster than the leak itself, then there will be solids left behind that could effectively plug the leak.

The critical leak size is the size micro-defect that allows microbial penetration into the package. The critical leak size of air-filled defects was found to be 7 μm at all pressures tested. This size is considerably important to food packagers because this is when sterility of the package is lost. Previous leak studies have shown that the critical leak size for liquid-filled defects coincide with the threshold leak size and pressure. If this is in fact true, then air-filled defects should exhibit a larger critical leak size than the liquid-filled defects. In this study, air-filled defects were examined. A bioaerosol exposure chamber was used to test micro-defects, nickel microtubes of known diameters 2, 5, 7, 10, 20, and 50 μm hydraulic diameters, against pressure differentials of 0, -6.9, -13.8, and -34.5 kPa.

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