Gelato Cold Chain for Delivery: Holding -18 C in Transit
Table of contents
Delivered gelato fails in the box, not in the kitchen. Hold every tub at -18 °C or colder from your freezer to the customer's, with only brief rises of up to 3 °C, because each warm minute grows ice crystals that never shrink back. Below: recipe, packing with dry ice or gel packs, probe points.
Why -18 °C is the number to hold
Most cold chain advice for frozen food comes from one rule. The EU directive on quick-frozen foodstuffs (89/108/EEC) says the product temperature "must be stable and maintained, at all points in the product, at -18 °C or lower, with possibly brief upward fluctuations of no more than 3 °C during transport." The same text explains why: "at -18 °C all microbiological activity likely to impair the quality of a foodstuff is suspended."
Here is the detail most delivery guides miss. The same directive states that "ice-cream and other edible ices shall not be regarded as quick-frozen foodstuffs." Gelato is outside its legal scope. Check your own national rules for the legal side; the -18 °C figure is still the best working target, because it is the setting the US FDA gives for a home freezer, 0 °F (-18 °C), and the one the whole frozen food chain is built around.
For texture, colder is better. H. Douglas Goff, in the University of Guelph ice cream technology text, notes that "below about -25° C, ice cream is stable for indefinite periods without danger of ice crystal growth; however, above this temperature, ice crystal growth is possible." In a delivery bag you are always above that line, so the job is to keep the warming small and short.
The damage is cumulative. Goff describes what happens on the way to the consumer: "If one were to track the temperature history of ice cream during distribution, retailing, and finally consumption, one would find a great number of temperature fluctuations. Each time the temperature changes, the ice to serum content changes, and the smaller ice crystals disappear while the larger ones grow even larger." That is heat shock, and a delivery run is a heat shock test you run on every order. The mechanism is explained in our guide to ice recrystallization.
| Point in the chain | Working target | Where it comes from |
|---|---|---|
| Hardening | -30 to -40 °C blast freezer | Goff, Ice Cream Technology, ch. 8 |
| Long storage | -25 °C or colder | Goff: stable for indefinite periods below about -25 °C |
| Pack-out and transit | -18 °C or colder, brief rises no more than 3 °C | EU 89/108/EEC Art. 5, used as good practice |
| Customer freezer | -18 °C (0 °F) | US FDA home freezer guidance |
Your shop recipe was balanced for the case, not the box
Quick reference. A creamy milk gelato is balanced for one serving temperature, roughly PAC ÷ -20. A display recipe at PAC 249 is designed for about -12.5 °C; delivered at -18 °C it arrives hard. Shift part of the sucrose to dextrose to reach PAC 297 (about -14.8 °C), still inside the 220 to 300 range, and tell the customer to temper it.
Figure 1. The same milk base with two sugar splits, and the gap each leaves to a -18 °C home freezer.
This is the decision a gelatiere makes and a logistics guide never mentions. Your shop recipes are balanced for the display case. Our guide to display case temperature covers why that sits around -11 to -14 °C. A delivered tub lives at -18 °C in the box and then in the customer's freezer, so a scoopable shop recipe arrives firmer than you designed it.
Take a 1,000 g milk base and change only the sugar split. Numbers come from the FGB ingredient table, with dextrose counted as monohydrate (PAC 173, POD 64 per 100 g) and lactose included in PAC.
| 1,000 g milk base | Base A, shop | Base B, delivery |
|---|---|---|
| Whole milk (3.5% fat) | 610 g | 610 g |
| Fresh cream 35% | 160 g | 160 g |
| Skim milk powder | 45 g | 45 g |
| Sucrose | 165 g | 100 g |
| Dextrose monohydrate | 15 g | 80 g |
| Stabilizer | 5 g | 5 g |
| PAC | 249 | 297 |
| POD | 184 | 161 |
| Total solids | 36.9% | 36.3% |
| Sugars (without lactose) | 17.9% | 17.3% |
| Fat | 7.8% | 7.8% |
| MSNF | 10.7% | 10.7% |
| Design serving temperature | about -12.5 °C | about -14.8 °C |
Both bases sit inside the milk gelato range: solids 36 to 42%, sugars 16 to 22%, POD 140 to 200, PAC 220 to 300, fat 6 to 12% and MSNF 8 to 11.5%. Base B is also less sweet (POD 161 against 184), because dextrose lowers the freezing point more than sucrose and tastes less sweet per gram. Our comparison of sucrose vs dextrose covers the trade.
Why not go further and design for -18 °C directly? The same rule would ask for a PAC near 360 in a milk gelato, well above the top of the range. Pushing PAC that far takes the base out of the range and, by the same rule, leaves it very soft at every warmer temperature it meets on the way. The practical answer is to stop at the top of the range, as Base B does, and close the last few degrees at the customer's end: a short rest in the fridge before serving.
Two rules follow. Balance every delivery flavour in the free gelato calculator and write its design temperature on the label. And do not send display pans: harden delivery tubs from the start, in the format you sell.
Packing the box: insulation, dry ice or gel packs
The box does not make cold; it only slows warming. What you put in with the gelato decides how long it holds.
Start cold. Pack tubs straight from storage at -25 °C or below, never from the display case and never straight from the batch freezer. Product at draw temperature still has much of its water unfrozen; it needs the blast freezer first, as our blast chiller guide explains. A colder start buys minutes before the product crosses -18 °C. Pre-chill the box and the coolant packs as well.
Fill the space. Air gaps warm fastest. Pack tubs tightly, put the coolant above and around them (cold air sinks), and fill empty space with crumpled paper rather than leaving it open.
Choose the coolant by the route.
| Coolant | Strength | Watch out for |
|---|---|---|
| Frozen gel or phase-change packs | Reusable, no special handling | Must be frozen colder than the gelato, or they warm it |
| Dry ice | Very cold, sublimes at about -78 °C (-109 °F), no meltwater | Must vent; never in contact with tubs; carrier rules apply |
| Freezer bag only, no coolant | Fine for a few minutes from shop to car | Gives no protection on a longer route |
Dry ice needs respect. NIOSH lists solid carbon dioxide as subliming at -109 °F, so in contact it can freeze a tub far harder than serving temperature; separate it with cardboard. In the US, 49 CFR 173.217 requires dry ice shipped by air or water to be packed in packaging "designed and constructed to permit the release of carbon dioxide gas to prevent a buildup of pressure that could rupture the packagings." By air, a package with no more than 2.5 kg (5.5 pounds) of dry ice used as a refrigerant is excepted from most other rules if it vents and is marked "Dry ice" or "Carbon dioxide, solid", with the name of the contents and the net weight of the dry ice. Never tape a dry ice box airtight, and check your courier's rules before the first shipment.
For local delivery by your own driver, frozen packs in a good insulated box are usually enough. Dry ice earns its cost on long routes and courier shipping, where you do not control the time in transit.
Probe points: a transit log you can trust
A box rated "up to 24 hours" was rated by someone else, with a different load, on a different day. Measure your own route.
- Pack-out. Probe the centre of one tub per box with a calibrated food probe. Record the time and the reading. Anything warmer than -18 °C goes back to the freezer.
- Hand-off. On test runs, send a sacrificial tub and probe it on arrival. Record the minutes in transit and the reading.
- Set your limit. Using the -18 °C target with brief rises of no more than 3 °C as your benchmark, the longest route where the test tub still arrives at -15 °C or colder is your delivery radius for that box and coolant.
- Log it. Write box type, coolant, outside temperature, route time and both readings in your batch log. Summer runs need their own test.
Repeat the test when you change box, coolant or season. If a route fails, cut the radius or upgrade the coolant; do not ask the recipe to fix logistics.
At the door: what the customer needs to know
The cold chain ends in the customer's freezer, and you can still influence it. Put a short card in every bag:
- Freezer first. Straight into the freezer on arrival, not on the counter while they unpack.
- Temper before serving. A delivery base like Base B is designed for about -14.8 °C. Moving the tub to the fridge for a short rest before serving softens it without a full thaw.
- Close the lid tight. In an open tub, moisture moves from the gelato to the freezer air and the surface dries, the start of freezer burn.
- Eat it within your stated window. Our guide to how long homemade gelato keeps covers the same home freezer clock.
- Do not refreeze a melted tub. As Goff explains, melted water refreezes onto the crystals that are left instead of forming new small ones, so the texture turns coarse. Lost volume in storage is a separate defect, covered in why gelato shrinks.
Our page on serving temperature gives the target range in more detail, if you want to link it on your card.
Related Concepts
- Ice crystal size and gelato texture: why bigger crystals read as grainy
- Blast freezing pan depth: why shallow formats harden faster
- Glass transition temperature: why very cold storage slows crystal growth
