Trawling Seafrozen Horse Mackerel

Horse mackerel is a moderately fatty fish (7‑24% fat seasonally). During frozen storage at -18°C, the unsaturated fats undergo gradual oxidation (rancidity), which causes off‑flavors and a stale smell after 12‑15 months. Trawling does not accelerate oxidation compared to light catch; the main factor is storage temperature stability. To maximize shelf life for human consumption, use within 12 months; for fishmeal or pet food, 24 months is acceptable. Vacuum‑packing or BQF blocks (less surface exposure) slow oxidation better than IQF.

Horse mackerel (Trachurus spp.) is classified as a histamine‑forming (scombrotoxin) species. The EU regulation (EC) 2073/2005 sets a nine‑sample plan with a mean limit of 100 mg/kg and a maximum of 200 mg/kg. The US FDA recently lowered its action level to 35 ppm. Histamine is heat‑stable and not destroyed by cooking or freezing – it must be controlled upstream via rapid chilling post‑catch. Trawling can cause stress and higher initial bacterial load, making rapid on‑board chilling and freezing critical. Buyers should require batch‑specific histamine test reports from accredited labs.

Choose BQF (block quick frozen) if you process large batches at once, e.g., canning, surimi, or fishmeal – you can thaw entire blocks in a tempering room or directly saw frozen blocks into portions. BQF lowers freight cost by 10‑15% due to higher container packing density. Choose IQF if you need portion control (e.g., restaurants, retail packs, or small‑batch frying) – you can take only the needed fish without thawing the whole carton. IQF costs more per kg but reduces waste. For a mixed‑use plant, buying both formats may be optimal.