Chemistry: analytical and immunological testing – Food or dairy products
Reexamination Certificate
2002-05-03
2003-11-18
Snay, Jeffrey (Department: 1743)
Chemistry: analytical and immunological testing
Food or dairy products
C436S020000, C436S060000, C436S164000, C422S082090
Reexamination Certificate
active
06649412
ABSTRACT:
This invention relates to a method and an apparatus for determining quality properties of fish on the basis of light reflection. A fish and a reflection measurement device (
5
) with a light emitter and a light receiver (
6
) are positioned in relation to each other, with the light emitter and light receiver of the device directed towards the fish's inner abdominal wall with peritoneum, so that the light emitter illuminates an area of the fish through the peritoneum and the light receiver captures the light reflected from the fish. The intensity of the reflected light as registered in three or more different wavelength bands in the visible and near-infrared range. The measurement results registered are, after any processing, entered into an algorithm in a calculation unit, where the algorithm express a quality property of the fish on the basis of the reflection of its inner abdominal wall with peritoneum and three or more different wavelength bands in the visible and near-infrared range. The calculation unit automatically calculates the quality property by means of the algorithm and measurement results. The intensities of reflected light are registered in both the visible range, especially between 400 nm and 600 nm and in the near-infrared range, especially between 850 nm and 1050 nm. By means of the method it is possible to measure quality properties of individual fish in a short time in a non-destructive manner, especially the color, Astaxanthin content, and/or fat content of Salmon.
The present invention relates to a method and an apparatus for determining quality properties of fish.
Before farmed salmon is slaughtered in a processing factory, a primary check of meat colour is made. For this purpose ten or so fish are taken from each pond and a piece of fillet cut from behind the vent. An operator compares the colour of the cut fillet in an area near the middle of the fish with the colours on a discrete colour chart containing different colour classes. The results of these test samples are assumed to be representative of the whole pond stock.
Both in production and sales, colour is the most important quality parameter for salmon. Salmon buyers can request information on the colour of a delivered lot in the form of a number corresponding to a colour number or a colour step on the Roche scale, a colour table. Another salmon colour reference is the colour number on the Salmofan scale.
To meet consumer requirements, farmed salmon production is adjusted to give the finished fish the most sought-after colour. The producer can use the content of astaxanthin in the feed to control the colour, as there is a correlation between the administration of this substance and the meat colour of the slaughtered salmon.
The fat content of salmon is another important quality parameter. Buyers dislike fish with too high a fat content. Chemical analysis of fat content is part of production control, but it too has to be carried out by random sampling.
The means currently available for controlling production and supplying customers with salmon of the desired quality are thus relatively crude and labour-intensive.
In EP 0 221 642 (Westinghouse Canada Inc.) a hand-held apparatus is described for grading fish fillets, i.e. cleaned fish cuts. The apparatus illuminates the fillet and measures the strength of the reflected light at defined wavelengths at which haemoglobin exhibits special absorption properties. The apparatus compares the values at different wavelengths with values in a stored data set and assigns to the fillet the colour class with the best match between the values and the data set. Haemoglobin is undesirable in fish fillets as it may lead to more rapid deterioration of the fillets. A quality measure for whitefish fillets measured with this device is that the meat is white.
The above-mentioned methods for measurement of colour require a cutting of the fish to produce a meat surface which can be used for the measurement. As a consequence, the measurement is either destructive or is performed at a relatively late stage of the slaughter process providing few opportunities for controlling the process according to colour of fish meat. Furthermore, currently used methods for determination of salmon quality can only provide one quality parameter each, necessitating several analysis procedures for determining both colour and fat content.
The purpose of the present invention is to provide an objective method for determining quality properties of fish wherein the above mentioned disadvantages are avoided, enabling the quality properties of individual fish to be measured in a short time in a non-destructive method, in particular a method enabling measurement of colour, astaxanthin content and/or fat content of salmon. It is in particular the purpose of the invention to provide a method for determining quality properties of freshly slaughtered fish on a slaughter line or in a grading machine so that each individual fish can at an early stage of processing be graded as to quality properties and subsequently be processed or sold for further processing in accordance with its properties.
The invention is based on the observation that it is possible to determine quality properties of fish, especially meat colour of salmon, by means of light reflectivity of their inner abdominal wall with peritoneum using wavelength bands in the visible and near-infrared range. This is a surprise because the peritoneum of e.g. salmon is mainly opaque to the eye and prevents a subjective evaluation of the colour of the meat lying behind the peritoneum. The ability of the invention to measure meat colour may to a great extend be based on the fact that measurement is performed also in the near-infrared range and that the reflection data thus abtained are used in the algorithm to calculate the properties.
The method of the invention is characterised in that,
a fish and a reflection measurement device with a light emitter and a light receiver are positioned in relation to each other with the light emitter and light receiver of the device directed towards the fish's inner abdominal wall with peritoneum, so that the light emitter illuminates an area of the fish through the peritoneum and the light receiver captures light reflected from the fish,
the intensity of reflected light is registered in three or more different wavelength bands in the visible and near-infrared range, and
the measurement results registered are, after any processing, entered automatically into an algorithm in a calculation unit, which algorithm expresses a quality property of fish on the basis of the light reflection from the inner abdominal wall with peritoneum, after which the calculation unit automatically calculates the quality property by means of the algorithm and the measurement results.
It is possible to use the method according to the invention for on-line measurement on a slaughter line or in a grading machine for freshly slaughtered fish by using a fully automated equipment and for random sample check at ponds or in processing factories by use of a hand-held instrument.
Advantageous embodiments of the method according to the invention are as follows:
To avoid repeated stoppages on an automated slaughter line or in a grading machine it is an advantage if the measurement can be carried out without interruption, so that the fish continue their movement during the measuring process. One embodiment of the method according to the invention is therefore characterised in that the fish and the light emitter and light receiver of the device are moved in relation to each other in the lengthways direction of the fish during registration of measurement results.
Preferably, a reflection measurement device is used wherein the light receiver is designed to receive light reflected from an area of the fish with a cross dimension of at least 5 mm and at most 25 mm, and the device and the fish is moved in relation to each other so that measurement results are obtained from areas which together form a stripe in the lengthways direction of the fish, with a
Borggaard Claus
Christensen Lars Bager
Gulbrandsen Knut Erik
Rasmussen Allan J.
Marine Harvest Norway AS
Snay Jeffrey
Vidas Arrett & Steinkraus P.A.
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