A fish is defined as fresh when it has just been fished and has not undergone processing or chemical-physical treatments to prolong its conservation (evisceration separately); it follows that, the defrosted fish is not duly INDICATED as such, if passed off as fresh (in order to distinguish it from the preserved one), it constitutes a potential commercial fraud.
METHODS to recognize fresh fish from the spoiled one
Sensory method: applicable without the use of chemical equipment or reagents; in summary:
| ASSESSMENT OF THE FISH FRESHNESS STATE | ||
Part of the fish | Positive characteristics | Negative characteristics |
General appearance | Brilliant, metallic, iridescent | Dull, opaque |
Body | The purchase must have a certain rigidity ( rigor - mortis ), which remains for at least 6-7 hours | Soft, flaccid |
Leather and scales | It must be moist, shiny, bright and tight, with very adherent scales and rich in transparent mucus | Color, lacerable, pigmented with milky and opaque mucus, scales that are easily removed |
Meats | They must be bright, firm, elastic (subjected to pressure with the finger, they must immediately return to shape) | Flaccid, with yellowish edges, grainy and opaque surface, easily flaked |
Eye | It must be very alive, bright, rounded, turgid and not sunken | Risen, opaque, sunken with gray pupil |
Gills | They must be well closed, with red or pink gills, moist with transparent mucus | Raised, yellowish, greyish or brick red, with milky or dry mucus |
Vertebral column | It must be clear, free of color and resistant, difficult to break; moreover it must be very close to the meat | Not adherent to meat, red in color |
Ventre | Elastic, spotless, compact | Swollen, flaccid |
Viscera | Smooth, clean and shiny | Mollicce, swollen and rotting odor even without piercing the intestines |
Anus | Closed | Lasso and protruding |
Smell | Inviting, tenuous and pleasant; if it is saltwater fish, brackish and seaweed | Acre, ammoniacal and tending to acid |
METHODS to recognize intact and healthy (even if thawed) fish from the spoiled one
In theory, a fish duly treated with cold, therefore reduced in temperature and frozen, preserves most of the organoleptic characteristics of fresh fish (but not all! Blue fish for example suffers more than others). A defrosted fish, compared to a fresh fish, loses muscular tonicity, shine of the skin and redness of the gills ... but it does not remain compromised in terms of healthiness; far from it! The abatement of temperature is therefore an ESSENTIAL procedure for the consumption of raw fish, since it destroys pests such as anisakis (even if it does not reduce its bacterial load); on the other hand, by subjecting a fish to cooking, the biological and microbiological risk is reduced regardless of killing; this means that, being able to choose between a "fresh" and a defrosted fish, from an organoleptic point of view, when cooked the first will certainly be more pleasant than the second. However, fresh fish cannot and should not be eaten raw; the raw food maker should therefore move towards thermally broken down fish according to the laws in force (temperatures of -20 ° C for at least 24 hours).
Given the limited availability of fresh fish from the short chain, global consumption is increasingly converging towards frozen and frozen products, to be defrosted or already defrosted; for this reason the control bodies have techniques and means capable of assessing the integrity of the fish, but with a minimum of attention and experience even retail consumers can avoid the spoiled or simply in precarious state of conservation.
For consumers, the precautions are essentially the same as those listed for fresh fish (with the treatment of what was mentioned in the previous paragraph), while the control bodies are able to use other standardized and safer methods, based on scientific parameters :
Physical method: determination of the electrical conductivity of the tissues: as the fresh product deteriorates, the electrical conductivity increases. Special instrumentation needed.
Chemical method: determination of trimethylamine, volatile basic nitrogen, formaldehyde, histamine, peroxides and thiobarbituric acid. Special instrumentation needed.
Biochemical method: search for specific enzymes that escape from cells during thawing; if they are present it means that the fish has been frozen and refrozen. Special instrumentation needed.
Microbiological method: it is based on the development of cultures of microorganisms, but they are too long to be applied to the instant evaluation of fish. Special instrumentation needed.
Tuna carpaccio
X Problems with video playback? Reload from YouTube Go to Video Page Go to Video Recipes Section Watch the video on youtubeIndications to consumers of fresh or thawed fish
Fresh: we remind buyers of fresh fish that food "chemistry" works wonders! Some substances, improperly applied to the almost rotten fish, can deceive the senses of an unscrupulous or simply unlucky consumer. Certain "unprofessional" suppliers sprinkle nitrate and nitrites on stalks and tuna in blue tuna, in order to preserve the ruby color (as in the butcher's shop), although sometimes the result can be counterproductive; it will have happened to everyone to notice on the stalls slices of tuna that from red-brownish (natural color and also dependent on the process of bleeding the animal) take on a fuchsia-bright and decidedly not very natural color. In other cases the fish arrives in large packs full of ice, which, while deceiving the sight, do not hide the smell of ammonia (crustaceans, having a carapace, lend themselves particularly well to scams because they retain the smell of raw and relentlessly release it inexorably during cooking).
Frozen or frozen: when buying frozen fish it is necessary to remember that the cold chain must be kept undamaged and therefore uninterrupted; to this end, it is advisable to place the frozen fish in the trolley only AT THE ULTIMATED SPENDING TIME and to preserve its temperature by means of refrigerated bags or thermal bags purposely integrated with iced eutectic plates (siberine). Then, after having monitored the temperature indicated in the refrigerator counter thermostats and having reached the choice of the package, the priority will be given to the frozen / frozen food present on the bottom of the freezer as they are less subjected to temperature changes caused by the opening of the door.
NB . The seriousness of a supermarket is also evaluated based on the location of the frozen food counter, which must be close to the cash registers and on the opposite side from the entrance.
NB . The EEC has established a classification, n. 2455/70, art. 6, which provides for the subdivision of the fish based on the state of conservation; see the dedicated article: Pisces - classification and structure.
