Lecture 6

Question 1

Preventing permeability of gas and vapor through packagages:

1. Describe modified atm. packaging
2. Describe selective permeability

Answer 1

Modified packaging:
1. reducing oxygen by adding nitrogen and oxygen
-slows respiration of microbes killing microbes
-slows metabolism of vegetables (increasing shelf life)
-reduces oxidation reactions
Reducing humidity- reduces water moisture available to be absorbed by the food product restricting water activity and thus restricting microbial growth

2. Selective permeability-slows down the rate at which oxygen goes into the package or eliminates it completely (impermeable packaging not always economically or customer friendly). You must research and find the appropriate polymer that slows down oxygen to your desired rate.

Question 2

Impact of degree of crystallinity on a package:

Answer 2

Greater the degree of crystallinity-the greater the rigidity of the package
Lesser the degree-more amorphous»>more flexible

Question 3

Describe advanced atm. packaging:

Answer 3

Antimicrobials and antioxidants are added to the atmosphere to take antimicrobial action and oxidation reduction to the next level

Question 4

Impact of molecular weight on a molecule

Answer 4

The greater the molecular weight the greater the:

1. Tensile strength
2. Impact strength
3. Melting viscosity-makes it more difficult to push through extruder

Question 5

HDPE-
PET-
PVC-
LDPE-

Answer 5

HDPE -High density polyethylene
high degree of crystallinity

PET-

PVC-Plasticizer