Photo taken in our studio.
If you are a small food producer with an online store, you are certainly shipping products. You are probably concerned about the costs of shipping food as well as the issues of food safety, especially for perishables. You could even lose your food license if you don’t ship food safely. But shipping perishables may also seem out of reach in terms of costs for your small business.
Well, we want to bring you some answers. For our Cheese Companions business, we faced those challenges. We had to ship cheese, and we researched for the most affordable yet safe way of shipping it. To answer those questions, we did a literature search. We also did our own time-temperature tests with various packages (insulated materials and gel packs) to learn which one kept the perishables at refrigerated temperatures (below 4°C/40°F) and for how long.
Many articles may leave you feeling puzzled, as the only recommendation they give you is to “test out” the appropriate packaging for your products.
Well, we did the tests and are sharing the results with you.
We are also sharing the best articles we found during our literature review.
This article will answer the questions:
- Which temperature does your package reach during shipping by mail (USPS, UPS, or FedEx)? How hot can it get?
- Which packaging should you use to ship temperature-sensitive products, perishables, and fresh food?
- How will you ensure that your perishables arrive at their destination still fresh and unspoiled?
- What is the best shipping option for perishables? Who is the best shipper?
- What are the costs of shipping perishables?
Understanding Spoilage due to Temperature – the Danger Zone
If you are a food producer, you are aware of the “danger zone,” and you know your food cannot be exposed to temperatures between 5°C and 60°C (40 to 140°F) for more than 2 hours and that you must throw it away after 4 hours in the danger zone (Ref: 2 Hour/4 Hour Rule Explained). Now imagine the fresh food you just shipped across the country. It flew to its destination overnight and probably left for delivery around 7 am this morning. It could be in the delivery truck until 6 pm tonight until it is dropped off at the recipient’s location. We are in Los Angeles in the summer. At which temperature do you believe is the cargo of this delivery truck all day? But more importantly, is your packaging adequate to ensure that your food will remain below 5°C until the end of the day?
Interestingly, we often think of extreme heat, but your perishables can also be spoiled if the temperature is too low and your product freezes. It can happen when shipping during winter, but it can also occur if your fresh food is in contact with those frozen gel packs in your package.
Credit: Wiley online library
Which Temperatures Do Packages Reach During Shipping by Mail?
Let’s look at the literature to answer this first question. Many studies have been done, especially for expensive products such as pharmaceuticals.
Here are two studies of particular interest:
- The effect of temperature exposure during shipment on a commercially available demineralized bone matrix putty. Cell Tissue Bank. 2016; 17(4): 677–687.
In this first study, they shipped 72 packages with temperature-measuring devices to various “warm climate” cities. The graph below shows the temperatures reached during delivery could be as high as 50-60°C (120-140°F). You can imagine that your packaging must be quite “robust” to sustain such temperatures and still maintain your fresh food below 4-5°C (40°F).
- Temperature mapping study of United States distribution systems, 2012 Thesis, Ken Silverman, Rochester Institute of Technology
The 2nd study included 500 shipments of pharmaceutical products to different regions of the United States during spring, summer, fall, and winter. Table 7 shows the minimum and maximum temperatures observed per season and per region. In peak summer conditions temperatures reached could be as high as 60°C (140°F) and in peak winter conditions as low as -20°C (-4°F).
Those numbers are not surprising when you consider that UPS and USPS trucks are not air-conditioned. On the other end, 30,000 FedEx-owned vehicles are air-conditioned, but 2/3 of its trucks are leased rather than owned. This article “In the hot seat: UPS delivery drivers at risk of heat-related illnesses” discussed the fact that temperatures in truck cargo areas could easily reach over 100°F in the summer (possibly as high as 150°F). You should consider those facts when choosing a delivery company.
The Packaging Components for Perishables and Refrigerated Food
Many articles cover this topic. So, we’ll just cover the basics and reference some comprehensive ones.
Let’s remember that packaging is only one of the critical factors to keep the integrity of your shipment. There are three components to temperature control during shipping: proper packaging, delivery duration, and temperature while in transit. The packaging is your first “line of defense.”
Your packaging deals with the two aspects of insulation and refrigeration.
- Insulation is ensured by insulating materials: Styrofoam boxes or insulated bags or lining (silver lining bags), placed in sturdy cardboard boxes. When using Styrofoam, the recommendation to use a minimum thickness of 1.5”.
As a small business, one practical thing to consider is the fact that Styrofoam boxes will take a significant amount of storage space versus the silver linings which come folded. Additionally, customers have a negative perception of Styrofoam: they consider it environmentally unfriendly.
- Refrigerants can be ice packs, gel packs, or dry ice. Ice packs seem to create more condensation than good-quality (“fleece style”) gel packs. Dry ice is a material to keep products frozen rather than refrigerated. There are regulations and restrictions when it comes to shipping products with dry ice (weight used, package markings).
Interestingly and rarely discussed, it’s essential to know that not all insulating linings or gel packs are made equal. As our tests showed (see below), there are significant differences in the ability of various materials to hold the cold, from one brand to another.
For more information on insulating and refrigerant materials, here are two articles with visual examples:
- “Shipping perishables: tips and guidance” shows photos of insulating box liners,
- “Packaging perishable shipments“ shows photos of Styrofoam boxes.
Examples of Received Shipments and Shipping Options Available on Online Stores
One reason we decided to do our own time-temperature tests is that we were surprised and concerned to see how food producers were handling their mail shipments of fresh food.
We used to receive cheese from local cheesemakers, and they were arriving at temperatures above 40°F, even when the outside temperatures were mild. We started questioning how to pack the cheese we shipped to avoid that issue.
Here are some examples of shipments we received:
- Cheesemaker A: We received 2 lbs of cheese in an insulating silver liner with a “fleece” gel bag (medium size). It was shipped overnight from New York City to Vermont. The gel pack was 1/3 to ½ thawed.
- Cheesemaker B: The cheesemaker shipped UPS ground from Vermont to Vermont and used a large “foam” ice pack in a newspaper. The cheese arrived nicely cold.
- Cheesemaker C: The cheesemaker shipped UPS ground (1 day) from Vermont to Vermont, in a Styrofoam box with a Nordic Ice gel pack. The gel pack was half melted. The outside temperature that day was mild (10°C-50°F by 6-7 pm when it arrived).
- Cheesemaker D: The cheesemaker shipped UPS ground (1 day) from Vermont to Vermont, in a Thermal Shield silver insulating bag with a Koolit gel pack. The gel pack was totally melted. The outside temperature that day was mild (10°C-50°F by 6-7 pm when it arrived).
We also researched which shipping options cheesemakers or major cheese retailers offered on their online stores. To our surprise, and as we’ll see later, some options were simply inadequate to ship cheese across the country! One major cheese retailer even offered to ship ground from Vermont to California. We had received an order from that retailer from New York City to Vermont, who was not shipping with any superior insulant or refrigerant. Keeping cheese below 40°F for five days seems inconceivable.
Our Time-Temperature Studies and Conclusions
With that data in hand, it was time to do our tests.
The methods: 48-hour tests in a temperature-controlled oven with thermocouples
In the studies we mentioned above, researchers shipped many packages across the country with temperature-monitoring devices. That gave us some information on the temperatures that parcels could experience. But it was unfeasible to consider testing packages in that manner: you need to make a large number of shipments to get any statistical significance, and that is quite expensive.
We wanted to define practically:
- the best packaging materials (including a choice of brands),
- the ratio of insulant/refrigerant to perishables needed to keep food fresh
- the packaging and shipping costs.
Luckily, I had access to an industrial temperature-controlled oven and the equipment and software to record temperatures over time, with the use of thermocouples placed in the package and food. The thermocouples we used were similar to your meat thermometer: they had a metal probe with a sharp point located in the food or in a specific location in the package to record the temperature.
We compared various brands of insulants and refrigerants:
- Thermal Shield® 3D Box Liners (insulating silver liners)
- Polar-Tech Re-Freez-R-Brix gel packs (sold on Amazon)
- Koolit gel packs
- Nordic Ice gel packs
- Propak gel packs (sold on Amazon)
- Frigid Ice gel packs
We did a series of 3 tests between June and August 2017, as follows:
- Test duration: 24 to 48 hours
- Packages included a given amount of cheese with various gel packs in silver insulating liners
- Outside (oven) package temperature: 24°C (75°F) for the first 24 hours, followed by an increase in temperature to reflect higher temperatures during truck delivery.
- First test – June 2017
The graph below shows the kind of data we gathered. The “control” thermocouple shows that the temperature over the 13 hours was constant around 24°C (75°F).
It also demonstrates that different gel packs hold temperatures very differently over time (with everything else being the same).
In this test, Koolit Long and Frigid Ice held temperatures below 4°C (40°F) for 10 hours. At that time, the temperature of the package with Koolit Small was already around 19°C (66°F)!
- Second test – July 2017
For the second test, we tested Re-Freez-X-Brix (Polar Tech), Koolit, and Propak gel packs.
- The results were pretty similar for the three packs
- They held the temperature to the desired level between 9 and 10 hours.
- The best gel pack was Re-Freez-X-Brix, which lasted 10 hours before it “gave up the frozen ghost” (Propak 9.5 hours, Koolit 9 hours.)
- Re-Freeze also held the temp slightly lower by 1°C while it was frozen.
- However, the test showed that we did not have enough refrigerant to hold the temperature during a transit time of 24 hours.
- Third and final test – August 2017
For our last test, we only tested Re-Freez-X-Brix gel packs in a food/gel pack ratio, which – we believed – should hold the temperature for 24 hours. We had 12 oz. of cheese for one large (RB-30, 30 oz.) and one medium (RB-15, 15 oz.) gel packs. And we used two insulating liners (double bags).
The results confirmed that we could ship 12 oz. of cheese in such package, 1-day ground or overnight, with a delivery temperature of 2-3°C (35-37°F) at 24 hours.
Clearly, our tests showed that we did not want the packages to be in transit beyond 24 hours for refrigerated products (below 40°F), which meant 1-day ground or overnight shipping. Shippers such as UPS do recommend a transit time of fewer than 30 hours.
Estimated costs of packaging (insulant and refrigerant)
We can now estimate the costs of such packaging. The math is easy.
|Components to ship 12 oz of cheese||Costs|
|Insulating box liners (2)*||$6.60 – 9.20|
|Re-Freez-X-Brix gel packs (RB-15 + RB-30)**||$1.85|
|Shipping 1-day ground (details in next section)||$9-11|
|Total packaging and shipping costs||$17.45-22.05|
In the next section, we’ll go into more details about shipping costs, and discuss another packaging option.
In our tests, we were able to find packaging solutions to ensure that we could ship refrigerated food by mail and be confident that it will arrive fresh (3°C/37°F).
We also established that we had to keep shipping transit time to a maximum of 24 hours.
Finally, we estimated costs and understood that the insulant is 80% of the packaging cost, so we should not be shy about adding gel packs to the shipment.
However, to make any profit on the order, we need a large volume of orders and/or expensive food, like some fancy European cheese! (12 oz. artisan cheese at $25 to $40/lb is $18.75 to $30.)
Packaging and Shipping Costs for Perishables
Let’s go deeper into these packaging and shipping costs.
As mentioned, there are two cost components: the packaging costs (insulants and refrigerants) and the shipping costs. Even though we won’t be able to provide comprehensive data on those costs, here are some examples of what to expect.
- In our tests, the packaging cost of shipping 12 oz. of cheese 1-day ground was around $8.50-11.00
- You could also use the “cool” chilling unit (it does seem like a cool concept!), a FedEx product that I just discovered while researching for this article. It will cost you $46 minimum, so it seems prohibitive for food. Cold shipping package provided by FedEx. “The lightweight package includes a one-time-use chilling unit that you activate and place in the box with the contents. The unit continuously evaporates small amounts of water at low pressure, keeping your shipment at 2°C to 8°C for up to 48 or 96 hours.”
Below are examples of costs to ship a 2 lbs box from Burlington, VT to Boston, MA, or Austin, TX. Note that your shipping company will offer you better pricing if you ship many orders, but as a small business with few orders, these are the kind of prices you’ll pay:
| Business address Burlington, VT 05401 to
residential address Boston, MA suburb 01588
|Best price: USPS – Regional Box A* (10″ x 7″ x 4-3/4″)||$7.92|
|USPS – Regional Box B* (12″ x 10-1/4″ x 5″)||$8.51|
|UPS Ground (1 day)||$10.70|
|USPS Priority Mail 1-Day™ Medium Flat Rate Box (11″ x 8-1/2″ x 5-1/2″)||$15.05|
|UPS Next-Day Early||$66.50|
*boxes not available at the post office, only online
| Business address Burlington, VT to
residential address Austin, TX 78702
|Best price: USPS Priority Mail Express 1-Day™ – 3 pm or hold for pickup 10:30 am||$48.70|
|USPS Priority Mail Express 1-Day™ – 10:30 am||$53.70|
|UPS Next-DayAir Saver (1-day end of the day)||$76.43|
|UPS Next-Day 10:30 am||$83.10|
|USPS Priority Mail 1-Day™ Medium Flat Rate Box (11″ x 8-1/2″ x 5-1/2″)||2 days – too long|
|USPS – Priority Mail 2-Day™ Regional Box B (12″ x 10-1/4″ x 5″)||2 days – too long|
|UPS 2nd Day Air||48 hours – too long|
|UPS Ground||4 days – too long|
It gets quickly prohibitive!
So, what can you do, to not scare your online customers away?
You have a few solutions: you could restrict yourself to the regions where you can ship “1-day ground”, or you can offer only an “overnight” shipping option for farther zones. “Overnight” shipping will become prohibitive for customers who live across the country. It will naturally self-regulate, i.e., those customers won’t buy from you.
If you live in a metropolitan area, you could already reach a large population with a “1-day ground” option, and your shipping costs will be significantly lower than shipping “overnight.”
In your online store, you can define various shipping zones and associate different shipping options to each zone. For instance, you can set your state as shipping zone A and offer ground and overnight shipping for this zone, and set all other states as shipping zone B with only overnight shipping.
Additionally, if you sell both perishable and non-perishable products in your online shop, you need to offer different shipping options for that zone B. You offer all shipping options for non-perishable products but only overnight shipping for perishables. On WooCommerce, you can achieve this by using the Conditional Shipping and Payments plugin.
You can also include some of your shipping costs in your product price. And the most valuable your product, e.g., some expensive European cheese, the easier it will be to add a few dollars to the price. However, in our experience, shipping can get so pricy across the country that it is impossible to include those costs in your product price.
Packaging Manufacturers and Shippers’ Tips and Recommendations
To complete this review, we’ve selected the best two articles we’ve read on how to ship perishable food so that it stays fresh.
This first article is from IPC Pack, a packaging company.
Their key recommendations are:
- The critical factors to consider:
- Transit time: don’t ship over weekends
- Temperature to be maintained
- Ambient temperatures
- Size and weight of package: keep it small to minimize the volume to keep cool
- Transportation budget of package
- Packaging and refrigerant pack budget
- Label your package “Perishable” or “Keep refrigerated.”
- The critical factors to consider:
This article’s illustrations are a good summary of what to keep in mind.
The key points to remember are:
- Choose the right shipping materials: insulation and refrigeration
- Avoid holding perishables for longer than 2 hours in the “danger zone” (40 to 140°F)
- Minimize transit time: max 30 hours – think about weekends
- Keep unfrozen food insulated from frozen gel packs
- Keep food in watertight plastic bags
- Use the best refrigerant: gel packs for food between 32 to 60°F; avoid ice which melts and is heavy
- Precool your insulated container
- Understand restrictions on dry ice
- Pack to minimize movement
- Use a sturdy corrugated box
Conclusion: Recommendations on How to Ship Perishables & Fresh Food for Your Online Shop
We shared a lot of practical information in this article. We hope that it helps you, as a small food producer, to make decisions about shipping your products by mail.
In conclusion, it is possible to safely ship perishables and still make some profit on the order, but costs are high and can quickly get out of hand, if you are not careful, especially if your product is a low-priced food.
Please share your comments below. We’d love to hear from you.
Special thanks to Ed Sawyer, my husband at the time, for his dedication and great help on this time-temperature testing project.
- “The effect of temperature exposure during shipment on a commercially available demineralized bone matrix putty“ (study showing 50-60°C during delivery.)
- 2 Hour/4 Hour Rule Explained (the danger zone)
- “How to ship food, so it stays fresh” (UPS)
- Packaging Perishable Shipments
- “Shipping Perishables: Tips and Guidance“
- “How to Ship Food and Perishable Goods“, Feb 2020
- “In the hot seat: UPS delivery drivers at risk of heat-related illnesses“, NBC News
- “How to ship temperature-sensitive goods“
- ThermaShield insulating box liners
- Polar Tech Industries