What does “sashimi-grade” actually mean?
Unlike regulated food safety grades, “sashimi-grade” is not a formally defined or legally protected standard in the UK or EU. In commercial practice, it describes tuna that meets a combination of criteria that make it suitable for consumption raw — specifically:
- Freshness: Caught, handled and processed under strict time-temperature conditions to ensure maximum freshness at point of consumption
- Colour: Deep, bright red loin muscle with no browning, oxidation bands or grey discolouration
- Texture: Firm, moist flesh with intact muscle fibres — no mushiness or softening indicative of autolysis
- Parasites: Appropriate inspection and handling procedures to minimise parasitic risk (relevant primarily for warm-water species)
- Cold-chain integrity: Unbroken chilled handling from point of catch through to the end buyer
In practice, buyers should define their sashimi-grade specification in writing when placing orders — including colour grade (e.g. AKAMI grade 1 or 2), fat content and tolerance thresholds for any visible defects. Verbal assurances of “sashimi-grade” without a written specification leave significant room for disagreement.
Tuna grading systems: what buyers should know
Japanese tuna buyers use a detailed visual grading system based on loin colour, fat content (toro vs akami) and overall flesh quality. For UK buyers, a simplified practical framework covers most wholesale requirements:
| Grade | Colour | Fat | Typical Use |
|---|---|---|---|
| A+ / #1 | Deep vivid red | Medium–high | Sashimi, sushi, tartare |
| A / #2 | Bright red | Low–medium | Sashimi, sushi, premium poke |
| B / #3 | Red-pink | Low | Poke, cooked, steak |
| C / #4 | Pink-grey | Low | Cooked only, processing |
Saku blocks: what they are and how they're produced
A saku block (from Japanese saku, meaning “cut”) is a rectangular portion-cut block of tuna loin — typically a standardised rectangle approximately 5–8 cm wide, 3–5 cm tall and 12–20 cm long — trimmed of sinew, bloodline and any skin or bone. Saku blocks are produced primarily for:
- Sushi restaurant supply (sliced directly for nigiri or sashimi service)
- Food-service portioning (cut into steaks or cubed for poke)
- Retail sashimi packs (vacuum-packed for fishmonger or supermarket display)
The production process starts with the whole tuna being butchered into the four main loins (two dorsal and two ventral). After skinning and sinew removal, the loins are cut into sections and further trimmed into uniform saku block dimensions. The blocks are then individually vacuum-packed and packed under continuous chilled conditions.
Saku blocks are classified into two primary muscle types:
- Akami saku — the lean, bright red dorsal loin muscle. The most common sashimi product and the default when “saku block” is ordered without further specification.
- Toro saku — the belly (ventral) loin muscle with higher fat content. Commands a significant premium. Further classified as chutoro (medium fatty) or otoro (very fatty) depending on position.
Cold-chain requirements for sashimi-grade supply
Cold-chain integrity is the single most important factor in maintaining sashimi-grade quality from source to consumer. For Indian Ocean tuna exported from Sri Lanka:
- Fish should be chilled to 0–2°C at point of processing and maintained at this temperature throughout the supply chain
- Air freight is standard for fresh chilled tuna destined for the UK market; transit times of 24–36 hours from processing facility to UK distribution are achievable
- Any break in the cold chain — even brief temperature excursions above 4°C — will accelerate colour degradation and increase bacterial activity
- Buyers should request time-temperature records as part of their documentation package where quality guarantees are required
Specifying sashimi-grade tuna for your programme
When working with a sashimi-grade tuna supplier, buyers should define the following in their product specification:
- Species (yellowfin, bigeye, or both)
- Format (whole G&G, loin, saku block — akami or toro)
- Size/weight range (e.g. saku blocks 200–400 g each)
- Colour grade (A+ / A or equivalent description)
- Bloodline specification (present or trimmed)
- Packaging (individual vacuum pack, master carton weight)
- Maximum transit time from processing to delivery
- Shelf-life minimum at point of delivery
Sourcing sashimi-grade tuna from Brookstone Trade
Brookstone Trade supplies chilled sashimi-grade tuna to UK buyers from Indian Ocean sources. We work with processing partners in Sri Lanka who produce saku blocks, loins and whole G&G fish to buyer specification. Contact us to discuss your sashimi tuna supply requirements, volume, and the QA standards relevant to your programme.