Most buyers who come to us for frozen food have already imported dry goods from Vietnam for years. Baskets, textiles, lacquerware, furniture components. The commercial habits transfer; the physical shipment does not. This piece is a plain-language primer on the parts of a cold-chain order that catch first-time frozen food buyers off guard, before the first PO goes out.
Written for buyers adding Vietnamese frozen food to an existing dry-goods programme. Covers what -18°C actually means in practice, core vs air temperature, reefer basics, pre-production samples, how to read a frozen food spec, and the rules on combining species in one reefer.
In this piece
What -18°C actually means
Industry convention sets -18°C as the threshold temperature for frozen food. On a spec sheet the number looks precise, but the convention is a floor, not a target.
In practice, cold storage runs at a working range of -18 to -22°C. The lower end gives a buffer: when a pallet moves from storage room to loading dock, air around the product warms briefly, and the product itself warms more slowly. Running storage at -22°C means the product can afford short exposure during handling without crossing the -18°C threshold.
What matters for the buyer: the spec number is a limit, not a target. The actual temperature should always be colder than that limit by design. A sample reading -17.4°C is a hold; -22°C is normal.
Core temperature vs air temperature
Three different temperatures live inside a reefer, and they are not the same number:
- Set point. The temperature the reefer unit is instructed to maintain, usually configured at -18 to -20°C for standard frozen fish, lower for ice cream and specialty products.
- Air temperature. The air circulating inside the container, logged continuously by the reefer's data logger. Visible to the shipping line and destination customs.
- Core temperature of the product. Measured by pushing a calibrated probe into the thickest part of a fillet or the geometric centre of a block. The number that actually matters for food safety.
Air temperature can read -20°C while a pallet left briefly on the dock has a core temperature of -16°C. Air recovers fast; product does not. Core is the right number to check at loading.
For a longer walk-through of the specific checks on a reefer before the plug goes in, see FROKO18's own note on what to check in a reefer at -18°C.
Reefer container basics (40 ft)
The default container for ocean freight on frozen food out of Vietnam is a 40 ft reefer. The 20 ft reefer exists but is less common on long-haul routes; equipment, slot availability, and freight pricing all favour the 40 ft on export corridors.
| Reefer item | Typical value | What the buyer should know |
|---|---|---|
| Length | 40 ft (also 20 ft; 40 ft is the common default) | Internal volume is lower than a 40 ft HQ dry because the reefer unit and insulation take space. |
| Set point | -18°C or colder (species-dependent) | Confirmed and recorded on the stuffing checklist. |
| Pre-cooling | Several hours before stuffing | Reefer runs empty at set point before pallets go in. Stuffing a warm container ruins the first few metric tonnes of product. |
| Air flow | From floor up through T-bar decking, past the pallets, back through the ceiling | Pallets must leave clearance for air; overstuffing causes hot spots. |
| Data logger | On the unit, running continuously | Logger file is pulled at destination. Reads the voyage history minute by minute. |
| Power | Vessel plug at sea, gen set at port and during trans-shipment | Trans-shipment gap is where cold chain breaks happen; ask the forwarder about plug coverage. |
None of this is a dark art. It is standard practice for every ocean reefer leaving Vietnam. The reason it still gets covered in a primer is that dry-goods importers have never had to think about it before.
Pre-production samples: what to lock
On baskets the pre-production sample locks weave, dimensions, finish, and hangtag. On frozen food it locks four different things.
- Physical cut and size. Fillet weight band (say 170 to 220 g), trimming (deep-skin on pangasius, bloodline removed, belly trimmed), bone-in or boneless, skin-on or skin-off. Different retailers want different combinations; a Nordic buyer's spec can look very different from a Middle Eastern one.
- Glaze percentage. Glazing coats each fillet with a thin layer of ice that protects against freezer burn during long storage. Standard glazes range from a few percent to 20 percent of total weight. Glaze is water, not product, so the kg price depends on it. A quote at "net weight after deglaze" is a different number from a quote at "glazed weight".
- Pack configuration. Primary pack weight (1 kg, 5 kg, 10 kg block), inner bag material, master carton count, carton labelling and best-before format. On surimi, FROKO18's standard is a 10 kg block, two blocks to a 20 kg master carton; 1 kg bags are available for supermarket private label.
- Sensory benchmark. Smell after thaw, texture, colour, cooking yield. The hardest to specify on paper; the easiest to disagree on later. The sample sets the standard; later shipments either hit it or they do not.
FROKO18 ships free samples under 2 kg per request; the customer covers the freight. Pangasius can be blended with other fish species per customer formula, which the sample is also the place to agree.
Lock the sample in writing, with a photograph
Approve the sample on an exchange where the spec and the image are both present. A pack photo on a messaging app is not an approval. A signed PDF with weight, dimensions, glaze percentage, and pack configuration is. On frozen food the gap between "that looks right" and "that is the production standard" is wider than on dry goods, because the sample thaws and the production run does not.
How to read a frozen food spec
A good spec sheet lists more numbers than a basket spec. Here is what to look for:
- Species and scientific name. Pangasius hypophthalmus for the farmed species that most Vietnamese pangasius programmes work with. Scientific name matters because retail-level naming varies by market.
- Form. Fillet (deep-skinned, skinless, skin-on), portion, cube, loin, steak. Whole frozen fish is a different product class.
- Size band. Weight range per fillet or portion, in grams. Narrower bands cost more because they require more sorting.
- Pack weight and format. IQF (individually quick frozen) in bulk master carton, or wrapped primary pack. Retail private label often needs the wrapped primary with a specific labelling format.
- Glaze. As a percentage of total weight, and the method (water glaze, polyphosphate solution, additive-free). Clean-label programmes often want additive-free.
- Microbiological spec. Total plate count, coliforms, specific pathogen limits. The retailer's compliance list sets these.
- Chemical spec. Water content, protein, phosphate levels where applicable.
- Storage temperature. -18°C minimum, with the working range noted.
- Shelf life. From date of production, in months. Typically 18 to 24 months on frozen fish, less on specific products.
Ask for a spec that lists all of these. A spec that only states species and weight is incomplete. For reference material across the frozen fruit and vegetable side, FROKO18 publishes a frozen fruit and vegetables supplier reference alongside the fish programmes.
Combining species in one container
Mixed-species reefer loads are routine, within rules.
- Fish and other seafood combine. Pangasius with surimi, pangasius with another fish species, fish with shrimp. Same temperature window, no cross-odour risk between seafood categories.
- Fish and fruit do not combine. Even in a frozen reefer, fruit and seafood odours migrate. The buyer gets a container of pangasius that smells faintly of mango, or fruit that tastes of fish. Rare, but once is enough.
- Fruit with fruit combines (most of the time). Standard tropical fruit (mango, pineapple, dragon fruit) can share a reefer. The exception is durian, which ships alone because the aroma is strong enough to pass to anything else sharing the box, including other fruit.
- Frozen vegetables combine with frozen fruit. Same temperature window, same handling.
The combining decision is practical, not just technical. A container with four species means four production runs on different days feeding into one stuffing, which takes coordination at the exporter side. FROKO18 handles that coordination; the buyer only sees the single consolidated PO.
What is import-side (ask your customs broker)
This piece covers the Vietnam-side mechanics because that is what we see every day. The destination-side mechanics (import health certificates, food safety authority registration, labelling rules in the destination language, additive declarations) vary by country and change often. We will not pretend to be qualified on the current rules for every corridor.
What to do with that: before the first PO, run a conversation with a destination-market customs broker who handles frozen food in your country. Share the Vietnamese exporter's spec sheet and ask them to list the paperwork they will need at clearance. For reference, FROKO18's frozen food FAQ covers the Vietnam-side documents and the common buyer questions; it does not cover destination-side import rules, which belong to your broker.
Treat your customs broker as the authority on destination rules, and the Vietnamese exporter as the authority on what leaves Vietnam.
That division of labour keeps everyone honest. A Vietnamese exporter who claims deep knowledge of your country's frozen food import rules is overclaiming; a customs broker who tells you how to run your Vietnamese reefer stuffing is doing the same.
Frequently asked questions
What does -18°C actually mean in a frozen food spec?
Threshold, not target. Core temperature below -18°C is the pass; cold storage runs at -18 to -22°C for the buffer.
How do I check the core temperature of frozen fish before accepting a load?
Calibrated probe into the thickest part of a fillet, or into the geometric centre of a surimi block. Below -18°C passes; -15 to -18°C goes back to cold storage.
Why 40 ft reefer and not 20 ft for a first frozen food order?
Better freight economics, better equipment availability, and standard on export corridors. 20 ft reefer is an edge case.
What should I ask for in a pre-production sample?
Physical cut and size, glaze percentage, pack configuration, and sensory benchmark. Approve in writing with a pack photo.
Can I combine fish and frozen fruit in the same reefer container?
No. Fish combines with other seafood; fruit combines with fruit (except durian, which ships alone). Fish and fruit cross-contaminate on odour even frozen.
