Info tuna quality

Tuna quality and market value With notes on Fresh and Frozen tuna

Generally speaking the higher the quality the higher the market price will be. The most discriminating market being Japan. In January 1995, a longline caught 200 kg bluefin tuna sold in the Tokyo fish auction for US 251,-/kg.

It is important to know that tuna applications vary around the world and thus the associated quality requirements. For instance the most discriminating Japanese Sushi bars look for tuna with a bright red colour, firm texture, translucency and fatty content. These quality is rare (1+) and if found mostly occur with Bluefin and Bigeye tuna. Prices to these buyers are secondary.

However for the lesser tuna quality there are numerous markets. For the Japan and USA market there are 4 basic grade distinctions.

  1. Tuna that has bright red muscle tissue, is firm in texture, has translucent flesh (clarity) and little or not fat.

  2. Tuna with red muscle tissue, are firm in texture, some translucency and no fat.

  3. Tuna with some red and some brown muscle tissue, is firm in texture, no translucency (opaque) and no fat.

  4. Tuna with brown and gray muscle tissue, soft in texture and no translucency.

Generally speaking the #1 grade is used in the higher end sashimi markets (high end Japanese markets). #2 Grades are used in lower end sashimi markets (e.g. Japan, Hawaii) or in better restaurants where tuna is prepared in semi cooked form. # 3 Grades are found in the lower end restaurants (e.g. USA mid west). # 4 grades are either canned or frozen or used in fresh markets in which fresh tuna is very price sensitive and consumption is a rather new phenomena. When frozen they are called landfrozen (contrary to Seafrozen products). The European market mainly use #3 and #2.

The colour of the lower qualities like #4 and even lower qualities ‘chocolates’ can be colour upgraded by the use of Carbon monoxide (CO).

The use of CO is strictly forbidden in the EU, as it is an additive.

It is important to note that:
Maintaining the quality of the tuna is a process that can never be reversed or improved.

The first 30 minutes after capture is the most critical period for treatment of tuna to maintain initial quality.
With good shipboard handling, longline vessels can deliver iced (fresh) tuna of sashimi quality for 14 days or longer.

On the larger freezer vessels on board fish (W/G) is graded (see above). Sashimi, Seafrozen A, Seafrozen B and steaks quality are distinguished.

Although different classification systems the fresh-and frozen systems broadly compare as follows:

For land frozen products -fresh tuna loins frozen on land- the speed of the processing again determines the quality. Again this is a processors determined factor.

Once thawed the structure –firmness- of the tuna next to microbiological and chemical parameters give indications of the quality of frozen loins. In poor quality B or lower the muscle tissue peels like paper.

Tuna is a world commodity for which Japanese and USA markets determine quality and thus price. As said maintaining the quality of the tuna is a process that can never be reversed or improved.

It is believed that struggle (without an opportunity to recover from the exercise) during capture is detrimental to the tuna flesh quality. Long lining is the only technique in which the fish has the opportunity to recover from the initial struggle on the hook.

Just as important to shelf life and quality is proper handling. The shelflife is significantly shortened through poor handling. To achieve top qualities the fish has to be immediately be stabilised. This is done by:

What does a buyer of tuna have to look for:

  1. Catch method, texture and meat structure both in fresh and frozen products give a more relevant indication of the quality.
  2. Microbiological and chemical tests give additional information (TVB, TPC, S. aureus, Faecal coliforms, Histamine, Enterobacteriaceae). It should be noted that irradiation with UV and other forms, is being used on source to reduce the microbiological counts
  3. Fresh Tuna specifics:

    4. Summarising for the Fresh tuna the following can be said of quality and market value (decreasing in value from left to right).
    (Used are USA criteria for fresh tuna, to show quality and market value.)

    Species: Bluefin tuna > Bigeye tuna > Yellowfin tuna > Albacore

    Size: Large >> Small

    Fishing method: Longline > handline (pole/line) > purse seine (net) caught

    Temperature: Immediate board chilling to 0ºC >> chilling several hours later

    Colour: Bright red > red > red brown > brown > gray

    Texture: Firm >>> soft

    Clarity: Translucent >>>> opaque

    Fat content: Visible >>> not apparent.

    The use of CO for fresh tuna gives a false image.

  4. Frozen tuna specifics:

Frozen tuna is either sea frozen or land frozen. With sea frozen the fish is headed, gutted and tailed on board and then shock frozen. Often qualities are sold to the USA and European markets, which are very good, but just could not match the Japanese standards. These DWT frozen products are used by quality reprocesses to make tuna steaks for the USA and European markets.

Land frozen is a remainder of fresh operates. Loins are frozen. Often the muscle texture is soft by the time the product is frozen. Extra care regarding histamine has to be taken in account. Lightly smoked tuna is land processed.

When buying frozen products pay attention to species, Catch method -line caught is better-, Sea or land frozen, Once thawed if the product gapes and its texture, the microbiological counts.

A good quality tuna steak due to processing and raw material characteristics should have a Total plate count of 10000-50000. If abnormal values as 1000 are found raise the red lantern, as there always should be some effect of processing –it is normal to find some bacteria-