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Calculate the Perfect Freezing and Storage Temperatures

What will it cost to freeze product? How much time will it take to freeze product? What’s the shelf-life of a product? That’s just a sampling of the innumerable factors refrigerated warehouse managers must consider when accepting new food products.

World Food Logistics Organization (WFLO), a Core Partner of the Global Cold Chain Alliance (GCCA), Scientific Advisory Council (SAC) member Dr. Dennis Heldman showcased the Food Freezing and Storage Calculator during a recent GCCA webinar.

The calculator is a user-friendly tool developed by the SAC for warehouse managers to determine the best way and means to store product, with information on nearly 1,000 specific products in 12 different product categories.

Heldman walked through this GCCA Member-Only resource by examining its functions, using it on real case studies and answering audience questions.

While there was not enough time to answer all of the audience’s questions, Dr. Heldman has provided the following answers to a number of frequently asked questions submitted by audience members during the webinar.

Q: Do you need the weight of the cases to determine the time required?
A: Mass (weight) of the product is not a parameter with direct impact on time-to-freeze. The density of the product (along with the container or package) is considered in the calculation.

Q: Does the calculator use a 3D modeling technique?
A: For the calculations involved, the three dimensions of containers or pallets are sufficient. Several other variables have more impact on the results than shape.

Q: Does pallet overwrap change the time to freeze?
A: Overwrap has significant influence on time-to-freeze, time-to-temper and cost-to-freeze. When overwrap is used, the calculation must use dimensions of the entire pallet as input.  This is due to the lack of air movement over individual package surfaces within the pallet. 

Q: What is the definition of “introducing space between individual boxes?”
A: The introduction of space between individual containers (or boxes) on a pallet is accomplished by introducing “spacers”. These units ensure that there is sufficient space between layers of containers on the pallet, and allow air movement, and reduce time-to-freeze.

Q: Does the calculator also have the option of determining the time to freeze using Quick freeze technologies?
A: IQF using cryogenic refrigerants has not been incorporated into the calculator. The “blast freeze” tab provides a good first estimate of time-to-freeze if the dimensions of the product pieces are used as inputs.

Q: Does the type of packaging material, both inner and outer, significantly affect the time to freeze?
A: Significant amounts of air incorporated anywhere within the package or pallet will increase the time-to-freeze.

Q: The typical ‘temperature curve’ for freezing has a longer time period when hitting change of state … is this longer time period also shown during tempering?
A: Yes; the tempering process is the reverse of freezing; except the final temperature is still remain below the initial freezing temperature of the product.

Q: Can we use the calculator to give a time to freeze gel packs?
A: Specific data for gel packs is not in the current version of the Calculator.  However, since gel packs predominantly contain water, we suggest using another high-water commodity, such as Cucumber or Lettuce, which contain about 96% water.

Q: In general, what kind of traffic movement does the calculator assume while calculating the time / cost of freezing?
A: Time-to-freeze accounts for air movement over the package surfaces; if traffic movement increases air movement, then the estimates might be high. The calculations assume air temperature is constant at the temperature used as input. If traffic causes the temperature to be higher, the estimates will be low.

Q: How much difference would it make if there was “still air” or “blast freeze?”
A: The differences in time-to-freeze estimates for still air as compared to air blast are significant.

Q: How would you differentiate a palletized shape with spaces between vs packed more tightly?
A: When using spacers, the best estimate is to use the dimensions of the individual containers or packages as inputs to the calculator. 

Q: When spacers are used, is the time to freeze the same for the center box vs. all layers?
A: When using spacers, the time-to-freeze should be the same for boxes at the center of the pallet as compared to boxes at the surfaces. In practice, there are likely to be small differences since it is difficult to maintain the same levels of air movement over interior surfaces as compared to the boxes located at the surface of the pallet.

About the Scientific Advisory Council

The WFLO Scientific Advisory Council is an eminent group of food scientists, logistics, and packaging experts from around the world. The council provides cutting-edge research and advice to members of the Global Cold Chain Alliance and its Core Partners. Learn more.

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