Packaging and Coolant Information

This information was provided to Home Grown Cow by Periship, our shipping partner.

Temperature is one of the most critical factors affecting the quality of perishable food products. Temperature controls the growth of bacteria which cause spoilage. The lower the temperature, the slower the rate of growth for the bacteria.

The effect of bacterial growth translates directly into spoilage, shortened shelf-life, reduced product's value and loss of business. Therefore, when tendering perishable food products for transportation, a shipper must ensure that the product has been prepared and packaged to minimize the effects of ambient temperature and shipping environment.

Designing an effective packaging system requires an understanding of your own internal distribution, the transportation environment, and the overall understanding of challenges and opportunities a Perishable Supply Chain presents. Failing to understand could result in damaged packages that will generate extra costs and customer dissatisfaction.

Based on the experience PeriShip gained after managing the shipment of several millions pounds of perishable food products, we want to share some important generally recognized packaging requirements that emphasize the elimination of void space, proper coolant ratio, and utilization of solid core EPS (expanded polystyrene) containers.

FedEx makes great efforts in trying to prevent damages in transit, however because the rapid automated sorting systems required to process millions of packages in only few hours, a great deal of preventive packaging is a good idea.

The shipper needs to ensure that a package can withstand: 

  • Impact shocks and drops during loading
  • Vibrations
  • Extreme high and low temperatures
  • Traveling upside down on conveyor belts
  • Sliding and tumbling
  • Experience lateral forces during conveyor jams and sorting

A container used to ship perishables must be strong enough to withstand the express shipping environment and depending on the product shipped we usually recommend the usage of solid core containers with walls at least 1.5" thick that are enclosed in sturdy outer corrugated boxes.

Depending on the product shipped a two mm or thicker plastic liner should be placed in the inner container to prevent leaking. In addition absorbent pad (s) consistent with the size of the inner container must be used to absorb possible leaks.

Very important is to choose the right container size, and immobilize the products inside the container by managing the void space around it. Using cushioning material such as molded EPS, corrugated pads and shapes, bubble wrap, kraft paper or butcher paper will prevent rolling, shifting or tumbling. Failure to completely immobilize the product inside will amplify the shocks, and the vibration forces will lead to a possible container/product breakage and also the coolant (gel packs or dry ice) will become a projectile constantly exercising force against the product and damaging it. (In addition coolant will lose its cooling effectiveness quickly)

We also strongly recommend to secure the covers of containers with any fish, fillets, scallops, bisque and basically anything that can open or spill out with heavy plastic banding or tape, and then place (whenever possible) the container inside a zip lock bag.

Some factors that can contribute to a package failure are:

  • Void space in the box
  • Initial temperature of the product
  • Mass of the product
  • Insulation of the packages
  • Proper conditioning of products and packaging materials used
  • Time, location and temperature during handling and staging prior to pick up

Pre-chilling of shipping containers before packing will prevent products from absorbing heat from the packaging. Containers used for shipping should never be kept on loading docks or storage rooms where the temperature is very high.

Condition gel-packs for at least three to seven days at -10 degrees and temperature retention capabilities and effectiveness will increase dramatically.

Coolant should be placed on-top and whenever possible on the side and bottom of the products to absorb heat from the outside. Poor placement of coolant will reduce its effectiveness. In addition, net to gross ratio is very important. The amount of coolant needed to ensure an optimal temperature on arrival can only be determined after specific packaging test; however there are some general guidelines that have been proven effective but such guidelines are subject to weather condition, products shipped, service used, and temperatures on pick up and delivery that the shipper needs to constantly monitor.

Winter time 20% coolant- If you ship 30 pounds of product at least 6 pounds of gel packs is required for a total gross weight of 36 pounds.

Summer time 30% coolant-If you ship 30 pounds of product at least 9 pounds of gel packs is required

Extreme heat condition or anticipated/possible delays in transit increase coolant by 5 to 10%

(Please note that the above coolant ratio does not apply for dry ice shipments)

Clearly when you are determining your shipping weight you must take in consideration the net/gross of your package as it will greatly affect the shipping cost. 

Many factors contribute to the cost of overnight shipping. These common challenges are faced by any shipper regardless of the freight carrier.

Cost control begins by coordinating the sales process with the fulfillment and shipment of orders. Determining the exact freight cost of an express shipment must take into consideration several factors:


  1. The size of the box used.
  2. The net-to-gross ratio: that's the amount of net product vs. the weight of the coolant and box.
  3. Any minimum weight requirements.
  4. The per-pound rate to ship to a specific location
  5. Any surcharges that might apply
  6. Packaging protocols


Whenever possible and depending on products shipped, it best to place as much of an order into a single large box. This not only gets the most favorable per-pound rate but also increases the overall mass of the shipment and decreases void space. The larger the mass, the longer it will hold temperature. In addition the cost of shipping one box will be less than shipping two or three smaller one.

We understand that at times consolidation is not always possible for many reasons:



  • Different products may not fit properly in one box
  • Some products cannot be co-packed with other products
  • Production cycles make it impossible to put up different products at the same time
  • Packing space may be limited and staging half-filled boxes may prove impossible
  • Choices of available packaging may be limited

The container used to ship perishables must be strong enough to withstand the express shipping environment. We strongly recommend that shippers use solid core containers with walls at least 1.5 inches thick that are enclosed in a sturdy outer corrugated box.

A two mm or thicker plastic liner should be placed in the inner container to prevent leaking. In addition, an absorbent pad, consistent with the size of the inner container, must be used to absorb possible leaks.

It is also important that containers and the perishable products inside are properly "pre-conditioned" by storing them in refrigeration as long as possible before the FedEx pick up

Gel packs should be frozen for at least 48 to 72 hours at a consistent temperature of (-10)°F. If a freezer is opened and closed often, ensure that the gel packs are placed away from the entrance door. Ideally gel packs should be taken out of the box and spread on a flat surface to insure complete freezing. This is not necessary, however, if the gel packs are placed in the freezer more than 48 hours prior to use.

The ratio of coolant to product depends on many conditions, including the type of product, the anticipated ambient temperature, weather and other factors. Because of these considerations, it may be necessary to increase the amount of coolant used for each shipment. Recommended coolant ratios range from 15% to 40% depending on expected weather conditions, refrigerant method (dry ice or gel packs) and product shipped.

It is important to ensure that you pack your products with enough coolant to provide a "temperature friendly" environment throughout the transit time. In the process of managing transit related events, we do utilize refrigeration on an exception basis, when a package is delayed. Not all delayed packages can be placed in refrigeration due to logistical limitations or accessibility. PeriShip does not provide temperature-controlled transportation, which is why it is so important that you properly package your products, especially when shipping to warmer climates. Please feel free to contact your Supply Chain Coordinator for more information on consultation on which best practices methods work best for your product.

We strongly suggest that you communicate these recommendations to the processor or packaging establishment you intend to use, and make sure that they understand the importance of such recommendations. PeriShip reserves the right to suspend any shipping originating from customers and/or processing plant locations that are found to be out of compliance with the general recognized guidelines to ship perishables in an express environment.

As a general rule, it is best not to exceed 65/70 lbs per box. 70 pounds and above could be sorted under different parameters that occasionally can result in a transit delay.

In addition, shipments, which contain dry ice, cannot be expedited, and all shipments regarding their weight are subject to security restrictions imposed by Homeland Security (TSA Known Shipper Program).

Note - These are only general guidelines intended to point you in the right direction. The best way to find out what box, coolant and product configuration will best work for you is to conduct test shipments. PeriShip and Home Grown Cow can work with you to conduct these tests.