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THAW/DEFROST INDICATORS
Quality of certain frozen perishables, such as ice creams, frozen foods, blood products and certain pharmaceuticals deteriorate rapidly if they are brought above the freezing temperature (usually zero degree centigrade). Hence, there is a strong need for a defrost or thaw indicators. A number of thaw indicators have been reported in the literature. None of the thaw indicator has been successful in the market mainly because they change color too rapidly. When we go for grocery shopping, we pick up a frozen food package, place it in the cart, check out, place it in the car/trunk and go home to put it in the freezer. The perishable does not loose its quality during this normal handling or just because the surface of the container was above the freezing temperature. We have developed thaw indicators with a delayed effect for the color change, we call them “thaw-time-temperature (TTT) indicators”. These indicators monitor effect of integral value of time and temperature above the freezing temperature. The general properties of the thaw time-temperature indicators are outlined below:
Color
- The color change is irreversible, e.g., Blue-to-red
Time required for the color change
- Time required for the color change can be varied (e.g., minutes to one day)
Temperature
- Temperature for the color change can be varied (e.g., +15 to –20oC), Wider temperature range is possible
- Can be designed to change color over a certain temperature range
- The device changes color only above a predetermined low temperature
- No color change below a predetermined temperature
Preparation/Manufacturing
- Easy to make
- Commercially available equipment can be used for manufacturing
Simplicity
- Single coating/layer thin device
- Can be prepared in form of labels
Safety/Hazard
- No toxic/hazardous chemicals
Cost
Additional information
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