Shelf Life Monitoring

1
Shelf Life Monitoring
2
Time-Temperature Indicators (TTI)

• Sensors that indicate temperature history or end
  of shelf life
• Integrate distribution exposure with kinetics
• End of shelf life indicated based on exposure
  time at different temperatures during storage
• Physical, chemical, enzymatic reactions are used
• Need to know the key deterioration reaction
• Kinetics of the reaction in the food should be
  similar to that of the reaction in the TTI
• Color change, movement of color along a scale

3
Time-Temperature Indicators

• Critical temperature indicators
• Partial history indicators
• Full history indicators
• indicator response at a constant T and activation
  energy used to predict a constant T equivalent of
  the indicator response
• constant T equivalent is used to predict the
  amount of quality attribute remaining

4

• Critical temperature indicators
• respond if a critical temperature is reached
• no temperature history
• used for freeze-sensitive or thaw-sensitive
  products
• when the temperature exceeds the critical value
  color of the indicator changes

5

• Partial history indicators
• respond if a temperature is reached and indicate
  time of exposure
• a chemical diffuses through a porous wick (scale)
  only when the temperature exceeds its melting
  point
• can choose chemical to use at different
  temperatures
• 3M

6

• Full history indicators
• continuous response to temperature changes
• two pouches containing a lipolytic enzyme and a
  lipid substrate
• activated by breaking the seal between them
• enzymatic activity causes pH change
• color of the indicator changes
• polymerization of diacetylene monomers, color
  change

7

• Full history indicators have range of activation
  energies
• 3M 41 kJ/mol (frozen fruits and vegetables)
• Lifelines 86 kJ/mol (sensory scores)
• I-Point 141 kJ/mol (firmness of tomatoes)

8

• Disadvantages of TTI
• need to have a good correlation between shelf
  life and indicator response
• specific for the location of the indicator
• expensive

9

• Time/Temperature Recorders
• Sensors that collect time/temperature data during
  storage
• especially important during shipment of
  perishable or frozen food products
• control of cold chain

10
Smart packaging

• interact with food or package environment and
  give signals
• indicate time/T history
• indicate spoilage, remaining shelf life, end of
  shelf life