Packaging

Question 1

Antimicrobial packaging - active compounds
-bacteria can’t get into food as active compounds in the packaging kill the bacteria before they get through the packaging.

Answer 1

• Silver substituted Zeolite. Matrix: LLDPE, PE, PVE, rubber. Application: Film, Wrap, milk containers, paperboard cartons. Toxic to kill bacteria, not very soluble so not likely to leach into food. Used in socks
• Triclosan. Matrix: polyre, rubber. Application: food container.

Question 2

Anti-microbial substances released as gas

Answer 2

• gas is introduced inside the packaging once the packaged has been closed, no gas in factory
• Example chlorine dioxide (ClO2)
• formed by Sodium chlorite (NaClO2) and citric acid are stable when dry (both solid then dry)
• When exposed to water (e.g. vapour from food), they react to form chlorine
• Concentrations inside package: high enough to disinfect the content (microorganisms)
• Amount of toxic gas after opening of package: too small to do harm but high enough to kill micro-organisms

-Example 2: SO2 released
-Botrytis cinerea
-very common in grapes
calcium sulphite & organic acids(citric acid) = sulphur dioxide gas

Question 3

Anti-microbial packaging - Materials that release disinfectant gas

Answer 3

• Chlorine dioxide. Matrix: Polyolefin. Application: Film, sachet
• Ethanol. Matrix: silicon dioxide. Application: sachet
• sulfur dioxide. Matrix: Laminated plastic sheet with Na2S2O5. Application: Sheet or pad for postharvest storage of grape fruits
• Wasabi extract. Matrix: Encapsulation in cyclodextrin. Application: Coated PET film, tablet

Question 4

Control of atmosphere

Answer 4

• The atmosphere is replaced with another gas (mixture)
• Package must be completely impermeable
• Breach of seal must be easy to detect (e.g. ‘balloon’ effect)
• Remove oxygen; prevent oxidation and reduce spoilage
• Introduce other gas; change colour, antimicrobial, flavouring effect

Question 5

Control of atmosphere - manage gas exchange

1. slow equilibrium
2. Modified atmosphere

Answer 5

1. replace atmosphere at time of packaging
   influx of air slowly normalises composition
   eventually atmosphere becomes same as ambient

2.
normal atmosphere at time of packaging
respiration or other process changes gas composition
slow exchange of air, due to diffusion through membrane
proportional to gradient (difference)
results in stable equilibrium

Question 6

Control of atmosphere - oxidant scavenging materials

Answer 6

-oxgyen free air
-put something in that pick up the oxygen that gets through packaging
-Iron-based system
-Fe 1g = 300cm3 O2
Fe Fe2+ + 2e-
Fe2+ + 2(OH)- Fe(OH)2
Fe(OH)2 + O2 + H2O Fe(OH)3 (rust)

Question 7

Intelligent packaging

Answer 7

Focus on communication with users
Time-temperature indicators:
length of time exposed to particular temperature

Freshness indicators:
packaging react to chemicals produces as product ages

Question 8

Time temperature technology

Answer 8

length of time (cumulative) exposed to particular temperature
chemical polymerisation
chemical enzymic hydrolysis (colour changes)
Consumer labels more problematic
Technology can provide technical information
However consumers expect legally binding advice
Erring on the side of caution is not cost-effective

Question 9

Spoilage senors

Answer 9

Based on pH-sensitive materials that react with volatile amines produced in decaying fish

Shows if it smells! (not if it is safe)

No safety indicator (pathogens) approved yet