Aquaculture Research

Evaluating Farmed Fish Meat (Quantifying Meat Quality)

Using sensory evaluation and machine analysis, we study how to quantify the quality of farmed fish meat to provide an overall evaluation.

We conduct research to develop technologies for raising brood stock, producing fingerlings and making feed.
In particular, we are focusing on meat quality, in order to evaluate the meat quality of the farmed fish we rear.

Measuring physical characteristics with a rheometer

Using sensory evaluation to objectively evaluate attributes like fish color, meat texture and smell

Evaluating the quality of farmed fish meat involves a number of factors. It is not easy to objectively appraise meat quality, but one important method for doing so is sensory evaluation.

In sensory evaluation, judges on a panel actually eat and taste the fish to objectively evaluate attributes like color, meat texture and smell. For example, when the panel is presented with two sashimi samples, rather than subjective information like color or firmness, they need to put the information into quantitative form in order to provide an impartial evaluation.

Here are the results of a study on meat quality when two samples of yellowtail sashimi were judged using sensory evaluation.

Sensory evaluation of yellowtail sashimi A and yellowtail sashimi B

Comparing yellowtail sashimi A to yellowtail sashimi B for each item evaluated reveals that yellowtail sashimi A scores higher for the dark meat* color tone and for the firmness of the meat. On the other hand, yellowtail sashimi B gets higher scores for fishy smell and sourness.

Machine Analysis Yields A Similar Result

Next, machine analysis is carried out to establish a link with the sensory evaluation results.

Results of measuring yellowtail sashimi dark meat color value a* value (*2)

For the color tone, a color difference meter (*3) is used to quantify chromaticity.
Redness is important for evaluating the dark meat, so the red color value is measured.
For the a* value, the higher the +value, the stronger the red color is. The stronger the -value is, the strong the green color is.

When the a* value of the yellowtail dark meat is measured, as shown above, yellowtail sashimi B has a lower a* value.
This demonstrates that the result obtained by this measurement is the same as for the sensory evaluation of the color tone value of the sashimi.

Firmness, smell, fatty acid composition and amino acids are also measured.

The sashimi's firmness is measured using a rheometer (*4). Smell, particularly a fishy smell and feed smell, is also an important determinant of quality.
Smell components are measured using GC-MS (*5), with smell characteristics of each sample being measured.

Fatty acid composition (*6) in muscle tissue, which is related to tastiness, is measured using GC, and amino acids (*7) are measured using HPLC (*8), to test the quality of the meat.

Using GC-MS to analyze odor components

Contribution to Fish Farming Business

The Central Research Laboratory leads research into overall evaluation by conducting sensory evaluation and machine analysis and quantifying the meat quality of farmed fish. This research has contributed to the successful development of the Marbless feed for yellowtail.

Having this kind of system in place for evaluating meat quality allows us to monitor and check the quality of our products regularly.

Other elements which have an impact on meat quality, like growth monitoring technology and technology of slaughtering for keeping the freshness, are also important in the aquaculture business.

Evaluating meat quality is not only about evaluating the fish but is also vital for evaluating fish farming technology.

  1. *1:Dark meat
    Fish have white and red muscle tissue. Dark meat is the red muscle tissue. Compared to the white muscle tissue (regular muscle), dark meat is richer in mitochondria and also contains plentiful hemoprotein, which helps carry oxygen.
  2. *2:a* value
    Chromaticity quantifying color measured using a color difference meter. The L*a*b*color system is used to show meat quality, with L* representing brightness and a* and b* representing chromaticity. For a*, a + value represents the strength of red and a - value the strength of green.
  3. *3:Color difference meter Measuring device displaying numbers for colors so that colors can be accurately identified. Used to show the color of objects.
  4. *4:Rheometer Apparatus for flexibly measuring the characteristics (physical properties) of objects. Used for quantifying the firmness of sashimi.
  5. *5:GC-MS
    Gas chromatography mass spectrograph. A combination of a chromatograph to separate molecules in gaseous form and a spectrograph to measure the mass of the separated molecules. GC-MS is used to analyze odor components and GC is used to analyze fatty acid composition.
  6. *6:Fatty acid composition
    Composition of fatty acids in the edible part of the fish. Lipids are extracted from the edible part and simultaneous analysis of the fatty acids is carried out using GC after creating a derivative of the fatty acids.
  7. *7:Amino acids
    Amino acids are organic compounds that contain amine and carboxyl radicals. Amino acids have a taste and are thought to contribute to the tastiness of foods.
  8. *8:HPLC
    High-speed liquid chromatography apparatus. Using a separation column and pressurized liquid, this apparatus separates compounds to provide simultaneous analysis of amino acids.