The Ultimate Guide to Packaging Frozen Foods for Delivery

Understanding the Delivery Environment: Humidity is Your Hidden Enemy

Here’s something most people don’t think about: humidity inside the delivery truck.

Why Humidity Builds Up

Our delivery model involves multiple stops throughout the day – just like when the supermarket delivers your groceries. Every time we open the truck doors:

1. Warm, humid outside air rushes in (especially in South African summer)
2. This warm air meets the cold -12°C environment
3. Moisture in the air immediately condenses (turns to water droplets)
4. We close the doors and move to the next stop
5. Repeat this 10, 20, 30 times per route

The result? High humidity levels inside the load box, even though the temperature stays at -12°C.

How Humidity Affects Your Packaging

This is critical to understand:

Cardboard + Humidity = Weakened Protection

When cardboard absorbs moisture from humid air:

• The cardboard becomes soggy and weak
• Structural integrity collapses – boxes can literally fall apart
• The thermal barrier properties dramatically decrease
• Wet cardboard conducts heat much faster than dry cardboard
• Boxes can collapse under stacking weight
• The bottom of your box might literally disintegrate

This is why virgin double-walled cardboard is so important – it has the structural strength to withstand moisture exposure better than thin, recycled cardboard. But even virgin cardboard has limits.

Condensation Forms on Cold Surfaces

When humid air contacts your frozen goods:

• Water droplets form on the packaging
• This moisture can seep through to your goods
• Ice crystals form on the outside of products
• Labels can peel off
• Packaging can stick together

How to Protect Against Humidity Damage

1. Use Virgin Double-Walled Cardboard The extra thickness and quality gives you a buffer against moisture absorption. Thin, recycled cardboard will fail much faster in humid conditions.

2. Consider a Plastic Outer Bag For cardboard boxes:

• Place your sealed cardboard box inside a large plastic bag
• Seal it (but allow some air circulation)
• This creates a moisture barrier
• The plastic protects the cardboard from direct humidity exposure

3. Polystyrene Boxes Have an Advantage Here One major benefit of polystyrene: it doesn’t absorb moisture. This is why commercial frozen food companies often use polystyrene. It maintains its insulating properties even in humid conditions.

4. Seal Everything Properly

• Tape all seams thoroughly
• Don’t leave gaps where humid air can penetrate
• Think of your packaging as a sealed system

5. Inner Plastic Wrapping Consider wrapping your actual food items in plastic wrap or vacuum-sealed bags before boxing. This provides:

• Protection from any moisture that does get in
• An additional barrier
• Better food safety

Why This Matters for Long Routes

The longer the route, the more door openings, the more humidity builds up. This is especially true:

• In summer (warm humid air outside)
• In coastal areas (naturally higher humidity)
• On busy days (more stops = more door openings)
• In afternoons (humidity accumulates throughout the route)

If your delivery is scheduled for late in the day, your packaging is sitting in a more humid environment for longer. This is another reason why quality packaging is essential.

The Humidity + Heat Double Threat

Here’s what makes it worse: humidity and heat work together against you.

Imagine a thin recycled cardboard box:

1. Humid air makes the cardboard damp
2. Damp cardboard loses insulation properties
3. Heat transfers through the weakened cardboard faster
4. Your goods warm up quicker
5. As they warm, they may release moisture themselves
6. This creates even more humidity around the package
7. The cycle accelerates

Good quality packaging breaks this cycle by maintaining its integrity even in humid conditions.

Cardboard Boxes: Not All Boxes Are Created Equal

Virgin Double-Walled Cardboard: The Gold Standard ⭐

What it is: Brand new cardboard with two layers of thick, corrugated material.

Why it works:

• Thick, solid walls provide excellent insulation
• Strong structure means boxes don’t collapse during stacking
• Air pockets in the corrugation trap cold air
• Minimal heat transfer through the walls
• Much better resistance to humidity damage – the double walls and quality material maintain integrity even when exposed to moisture from frequent door openings

When to use it: Always, if possible. Especially for:

• Long-distance deliveries
• Hot summer days
• Humid conditions (coastal areas, summer afternoons)
• Valuable products
• Routes with multiple stops (more door openings = more humidity)
• When you want peace of mind

Cost vs. benefit: Yes, it costs more than recycled boxes, but the protection is worth it. Think of it as insurance for your frozen goods – especially against the humidity that builds up in delivery trucks.

Recycled or Single-Walled Cardboard: The Risk ⚠️

What it is: Used cardboard or thin single-layer boxes.

Why it’s risky:

• Thinner walls = less insulation
• Recycled material has air gaps and inconsistencies
• Weaker structure can collapse under weight
• Heat penetrates much faster
• Cold escapes much quicker
• Highly vulnerable to humidity damage – thin or recycled cardboard absorbs moisture quickly and loses strength fast. In the humid environment of a delivery truck with frequent door openings, these boxes can literally fall apart or become soggy and useless.

The reality check: On a hot summer day in South Africa, the temperature difference between the outside air (30°C+) and your frozen goods (-12°C) is over 40 degrees. Thin cardboard simply can’t maintain that barrier effectively. Add in the humidity from multiple door openings throughout the day, and you’re asking for trouble.

When it might be okay:

• Very short distances (same-day local delivery with few stops)
• Mild, dry weather
• Non-critical items
• When used WITH additional protection (plastic outer bag, newspaper, bubble wrap)

When to avoid:

• Long-distance (inter-city) deliveries
• Hot weather
• Humid conditions or summer afternoons
• Routes with many stops (more humidity exposure)
• High-value products
• Items sensitive to partial thawing

✅ THE RIGHT WAY

1. Always Include Ice Packs or Gel Packs

This is non-negotiable. Here’s why:

Polystyrene is passive insulation – it slows down temperature change, but it doesn’t actively keep things cold. Think of it like a thermos: if you pour hot coffee into a thermos, it stays hot. If you pour cold water into a thermos, it stays cold. But an empty thermos at room temperature doesn’t make things cold.

How many ice packs?

• Small box (lunch box size): 2-3 ice packs
• Medium box (6-pack size): 4-6 ice packs
• Large box: 8+ ice packs

Pack them around the sides and on top for best results.

Pro tip: Freeze your ice packs solid the night before. Not frozen solid = not effective enough.

2. Pack It Full – No Air Gaps

This is where people make their biggest mistake. Here’s what happens when you half-fill a polystyrene box:

1. You place frozen items in the bottom
2. The top half is empty air space
3. That air space is at room temperature (let’s say 20°C)
4. You close the lid, trapping that warm air inside
5. That warm air slowly thaws your frozen goods from above
6. Even with ice packs, you’re fighting a losing battle

The solution: Fill every gap!

• Use extra ice packs
• Add crumpled newspaper
• Add bubble wrap
• Add cardboard dividers
• Add more frozen goods

The box should be so full that the lid presses down snugly.

3. Seal It Immediately in a Cold Environment

Imagine this scenario (this happens all the time):

1. You pack your polystyrene box in a warm kitchen
2. You leave the lid open while you find tape
3. You take a phone call
4. 10 minutes pass
5. The box is sitting there, open, at room temperature
6. You finally close it and tape it shut

What just happened? You trapped warm air inside. That warm air is now sealed in with your frozen goods. It’s like packaging a heating element alongside your ice cream.

The right way:

• Pack in a cold room if possible (walk-in fridge/freezer)
• Work quickly
• Close and seal the lid immediately
• Don’t let packed boxes sit open at room temperature

❌ THE WRONG WAY (Don’t Do This!)

Polystyrene box alone without ice packs: “But polystyrene is insulated!” Yes, but passive insulation only slows down temperature change. Without a cold source (ice packs), it’s just delaying the inevitable.

Half-packed boxes with air gaps: You’ve just created a warm air pocket that will slowly thaw your goods. This is the #1 cause of thawed deliveries.

Leaving boxes open at room temperature: Every minute that lid is open or loose at room temperature means more warm air getting trapped inside when you finally seal it.

Using wet or damp polystyrene: Water conducts heat much better than air. Wet polystyrene has lost most of its insulating properties.

✅ SUCCESS STORY: The Biltong Business

The situation: A customer ships 15kg of frozen biltong from Johannesburg to Cape Town every week.

What they do right:

• Virgin double-walled cardboard boxes
• Each box wrapped in a plastic outer bag (humidity protection)
• Goods frozen solid for 24 hours before packing
• Packed in their cold room
• Boxes sealed immediately
• Additional newspaper as filler
• Clear labeling
• Uses waterproof packing tape

Result: 12 months of deliveries, zero temperature complaints, zero humidity damage issues, happy customers. When asked about the plastic outer bags, they said: “We learned the hard way that Cape Town deliveries in summer meant soggy boxes. The plastic bags solved it completely.”

✅ SUCCESS STORY: The Ice Cream Entrepreneur

The situation: Small business shipping artisan ice cream to customers.

What they do right:

• Polystyrene boxes packed FULL of ice packs (sometimes more ice packs than ice cream!)
• Boxes filled to the absolute top
• Sealed immediately in their walk-in freezer
• Cardboard outer box for additional protection
• Pre-frozen gel packs that are much colder than their product

Result: Ice cream arrives perfectly frozen, even in 35°C summer weather. Their secret? “More ice packs than you think you need.”

❌ PROBLEM STORY: The Family Food Parcel

The situation: A family wanted to send frozen meals to their daughter in another city.

What went wrong:

• Used recycled moving boxes (single-walled, damaged)
• Packed in a warm kitchen
• Polystyrene inner box but no ice packs (“I thought the delivery truck would keep it cold”)
• Half-filled with air gaps
• Left sitting for an hour before collection
• No protection against humidity

Result: Goods arrived partially thawed, and the cardboard box was soggy and falling apart at the bottom. Temperature data from our truck showed perfect -12°C throughout the journey. The issues were:

1. Poor packaging trapped warm air inside
2. Thin recycled cardboard absorbed moisture from humidity and weakened
3. No ice packs in the polystyrene meant no cold source
4. Multiple failures combined to create the problem

Lesson learned: The family now uses virgin double-walled boxes with plastic outer bags and follows all packaging guidelines. No more problems.