Hints and Suggestions

Preparation of Samples

Always ensure that the sample for measurement is slightly wider than the sensor and that it has a minimum thickness of 25mm. Note – this ensures that there are no reflections from the underlying surface, which could result in spurious readings.

Ensure that the product for measurement is fully defrosted, and prepared in accordance with instructions.

Operation of Fatmeter

The Operator should check the stability of the calibration settings of the Fatmeter each day on the check pad supplied before general use.

The Fatmeter should be switched on 10 minutes prior to use (this allows the meter to warm up and stabilise). Ensure that you have chosen the correct calibration setting for the product to be measured.

Ensure that measurements are taken in a consistent and repeatable manner.

Ensure that the sensor head is firmly in contact with the product. We suggest that the meter is held in a vertical position (moving the sensor from the vertical… back and forth… means that you are reading different sectors of the product, and this can affect repeatability of your measurements).

After pressing the ‘READ’ button, always allow reading to stabilise before releasing the button. Note – the reading is only stored by the meter upon release of the button.

When the displayed reading takes a long time to settle, this is a good indication that there are pockets of air in the sample. Simply press the meter further into the product (depending on thickness), thus expelling any air.

When the meter displays ‘BAD’, possible causes could be –

• You have chosen the wrong calibration setting.
• The fat specification of the product is outwith the ‘range of experience’ set for this product
• There are large air pockets or cavities located in the product directly beneath the sensor.
• The product thickness is insufficient.

When ‘LOW BATTERY’ is indicated on display or the display becomes very faint, means that the battery needs recharging.

Cleaning and General Care

The FATMETER is a sealed unit and is waterproofed to IP 67 prior to leaving the factory. However, we do not recommend that the unit be immersed in water or any other fluid. Tampering with the unit, opening the seals, etc., will immediately invalidate the warranty.

Your FATMETER is encased in impact resistant plastic, with the sensor head made from stainless steel and PTFE. Take care not to pierce the PTFE film – ie. avoid placing the sensor head on abrasive or rough surfaces. The unit may be cleaned with a damp cloth, using a mild solution of detergent. Be aware that some household cleaners may contain chemicals which could seriously damage the plastic enclosure. Avoid the use of any petroleum based solvent cleaners.

The unit should be charged regularly. Where the unit is in constant use, we recommend that the power supply be connected to the meter when at all possible. This will ensure that you have a fully charged battery available when necessary.

Your DISTELL FATMETER is a precision instrument. Ensure that the unit is stored securely in transit. Do not drop or otherwise misuse the equipment, as this may invalidate the warranty.

Before Calling for Service

Should you have reason to believe that a fault has occurred, please first of all check the obvious…

• Is the unit switched on?
• Has the batteries been charged?

Should any fault persist, please telephone our Help Desk for advice and/or to report the fault.

Warranty and Repair

Your DISTELL FATMETER is fully warranted against manufacturing defect for a period of 12 months. Please refer to Warranty Terms and Conditions.

Should you have occasion to return the unit for repair, please telephone our Help Desk, report the fault and ask for advice.

Please quote date of purchase and give a full description of the fault.

Factors Affecting Results

The results obtained with the Fish Fatmeter can be affected by various factors:-

Operator

The operator of the equipment must use the instrument in a consistent manner and follow the guidelines set out in this handbook and appendices. Take care that:-

• The sensor head is fully in contact with the sample or specimen prior to taking a reading and not at an angle to the surface. Should the sensor head NOT be fully in contact with the fish, the Fatmeter may display a high, erroneous reading.
• The sensor head is clean and no excess oil or water is present.
• The sensor head is not removed from the fish before releasing the ‘Read’ measurement button.

Samples/Specimens

Where possible, follow diligently the guidelines within the handbook and appendices. It is possible to use the Fatmeter on fish species other than those for which the instrument is calibrated, and in different ways, however, the results obtained will not necessarily be accurate. They should allow, however, reproducible results which may be used as a basis for calibration or measurement.

Where wholly consistent results are required, then the procedures as laid down in the Measurement Charts supplied, must be adhered to, or, in the case of a different fish species, a specific calibration obtained from Distell.

Please ensure that:

• The specimen/sample has been prepared as per guide lines.
• Any excess surface slime, water or oil on the skin of the fish should be lightly removed by wiping off the excess by hand. There is no need to completely dry the specimen/sample.
• The specimen / sample is NOT dehydrated. As the Fatmeter is actually measuring the water content as part of the measurement of oil content, it is important that the specimen has not been allowed to dry out.

Fatmeter Measurements vs Foss-Let Chemical Method

If you wish to the accuracy of the Fatmeter Measurements, and compare the results with Foss-Let Laboratory Analysis Method for an accurate appraisal of its performance, it is essential that the techniques employed are the same as those from which the original calibration data were derived.

When checking the calibration of the Fatmeter against the Foss-Let Method a key element in the process is the preparation of fish samples for these determinations. The purpose of this note is to describe the procedures to be used in the preparation of these samples. For detailed instructions please refer to the User Manual and calibration charts supplied with the meter.

Background

In attempting a calibration check of the Fatmeter, there are THREE points which must be understood. These are:

• The Fatmeter is primarily intended as a tool for the Processor, Fish Farmer, or Researcher. It provides a non-destructive estimate of the fat content of the fish, or fish section. Please refer to measurement instructions for the product.
• The Fatmeter is an averaging instrument and except in clearly defined circumstances will not make accurate measurements of the fat content of smaller, single fish eg. Herring and Mackerel, which require readings to be averaged from each of EIGHT fish randomly selected from a batch, before the specified accuracy of the instrument can be achieved. On the other hand, the fat content of a single large fish such as Salmon, can be assessed accurately if FOUR readings are taken from EACH side of the fish. These are then averaged by the instrument to provide an estimate of the fat content representing the trimmed fillets of the fish.
• All fat content measurements used in the preparation of the calibration data for the Fatmeter were obtained using a Foss-Let Oil Meter. This requires 22g sample of fish flesh to be used. To allow for losses in mincing, sample of fish muscle with a minimum weight of 60g are required. It is advisable to prepare enough minced material in case a duplicate Foss-Let measurement is required, so that a sample of at least a 100g in weight is desirable. It is also good practice to carry out triplicate Foss-Let measurements on each filtrate. Any contamination of the filtrate or of the Foss-Let itself will then be immediately apparent.

Preparation & Measurement of Fish Samples

Sprat, Sardines, Pilchards & Anchovy

Because of the small size of sprats, the sampling procedure is different to that of other fish, such as herring or mackerel. It is necessary to calibrate using larger numbers of fish, and interpret the results as a batch average (batch mean).

Before taking Fatmeter readings, the fish should first be lightly cleaned of any slime or excess water. We recommend that Fatmeter readings are taken utilising a SINGLE READING on EACH of a large number of fish. The Fatmeter measuring head is then applied to the skin of the intact fish at the recommended position as indicated in the RECOMMENDED MEASUREMENT SITES section of this manual. Groups of fish are selected using the Fatmeter, to lie within the following indicated range of fat/oil content:

The increasing size of these ranges is due to the logarithmic nature of the instrument’s response. Sufficient numbers of fish are taken, in each range, to fill a 600 ml beaker. This is normally between 20 and 30 fish, depending on size. The mean Fatmeter reading is then taken for each batch.

The fish then have head and tail removed, are split and gutted, and the ’butterfly’ fillets so formed in each batch, are minced together in a blender (eg Magimix). Thorough mixing is mandatory if a truly homogeneous sample is to be presented to the Foss-Let. This is especially true if the samples are to be stored, since, in high oil content fish, some separation of oil will occur.

After completion of Foss-Let analysis, the average of the results should be directly comparable with the average of the results achieved using the Fatmeter.

Eels

Select FOUR eels of similar size and weight at random from a batch. Wipe of any excess slime or water from the skin, then take one reading on each side of the fish. The instrument sensor head is placed on the skin of the intact fish just behind the vent (anal outlet) along the middle line. Please ensure that the sensor head is in good contact with the body of the fish (not easy with small eels).

Take the eight readings with the Fatmeter. The resultant average should accurately reflect the overall fat/oil content of the FOUR eels used for the test.

To accurately compare the Fatmeter results to Foss-Let laboratory analysis requires that you carefully follow our procedures in the preparation of the fish samples.

Firstly, cut off the head, and remove the gut. Then remove the skin. ALL of the remainder of the fish, including bones, fins, flesh, etc. are utilised for the Chemical Analysis. All FOUR prepared carcasses are minced in the blender for approximately two minutes. This procedure normally produces more mince than is required for the Foss-Let determination.

If the mince has been stored for any length of time, it should be thoroughly mixed before extracting the sample for the Foss-Let. This is particularly important with fish of known high fat/oil content, since the oil will tend to separate from the solid material of the mince.

The mean value of the fat content of the mince of the four fish is then compared to the mean value of the fat content derived from the Fatmeter readings.

Salmon & Trout

Adult Salmon and Trout are relatively large fish. Before taking Fatmeter readings, the fish should first be wiped to remove any slime or excess water. The Fatmeter sensor head is then applied to the skin of the intact fish on each side, just above, and parallel to the lateral line, at the positions indicated in your measurement chart.

Where the fish is between 100-500gms FOUR fish should be chosen at random from a batch. Fatmeter readings are then taken from BOTH sides of each of the four fish. The Fatmeter will then display the average fat content of the fish tested.

Where the fish size is in excess of 500 gms each fish should be measured individually, with EIGHT READINGS taken (four per side of the fish). The measurement sites should be carefully selected as per instructions in this manual.

The fish are then filleted, the belly walls removed and the excess dorsal fat deposit also removed. The skin is peeled off, care being taken that no flesh is removed with the skin. The remaining fillets of the fish are then minced together in a blender for approximately two minutes. If the mince has been stored for any length of time, it should be thoroughly mixed before extracting the sample for the Foss-Let. This is particularly important with fish of known high fat/oil content, since the oil will tend to separate from the solid material of the mince.

The mean value of the fat content of the mince of the four/one fish is then compared to the mean value of the fat content derived from the Fatmeter readings.

Herring

Eight fish are selected at random from a batch of fish. Remove excess water from the skin of the fish and Fatmeter readings obtained from one side of each fish. The instrument sensor head is placed on the skin of the intact fish just under the dorsal fin and above the lateral line, parallel to the backbone on the thickest part of the fish, as per measurement chart.

Please take care to keep the central conductor of the sensor head away from the belly cavity and above the strip of brown flesh which runs from head to tail just under the skin in the middle of the fish.

However, where larger Herring need to be measured….eg. above 500 gms, then use only FOUR similar sized fish for the test. A measurement should be taken from BOTH SIDES of these larger herring samples. After taking the eight readings with the Fatmeter, the resultant average should accurately reflect the overall fat/oil content of the FOUR herring used for the test.

The fish are then filleted and the belly walls and fins removed. The fillet skins are lightly cut into approximately 10 mm squares to allow proper mixing in the Blender. (It is difficult to strip the skin from a herring without removing at least some of the underlying flesh). All sixteen fillets are minced in the blender for approximately two minutes. This procedure normally produces more mince than is required for the Foss-Let determination. If the mince is to be stored, it should be thoroughly mixed before extracting the sample for the Foss-Let. This is particularly important with fish of known high fat content, since the oil will tend to separate from the solid material of the mince.

The mean value of the fat content of the eight/four fish is then compared to the mean value of the fat content derived from the Fatmeter readings.

Mackerel

The recommended sampling procedure is similar to that for herring, with the sensor head being placed approximately in the positions shown in measurement charts provided…ie. directly under the dorsal fin.

However, where larger mackerel…..eg. above 500 gms, are being measured and assessed with the Fatmeter, it is necessary to utilise only FOUR fish of equal size for the test. A measurement should be taken from BOTH SIDES of these larger mackerel samples. We have found that there can be up to 8% difference from one side to the other of a large mackerel. Having taken the eight readings with the Fatmeter, the resultant average should accurately reflect the overall fat/oil content of the FOUR mackerel used for the test.

With mackerel, it has been found necessary to remove the skin prior to blending. This can be done more easily than with herring, although care is still required to make certain that all the flesh is retained on the fillet. The problem of oil separating from the mince is more acute than is the case with herring because of the higher values of oil content commonly encountered.

Thorough mixing is mandatory if a truly homogeneous Foss-Let sample is to be presented. As with herring, the mean value of fat content obtained from the eight fish using the Foss-Let is compared to the mean value of fat content derived from the Fatmeter readings taken on the same eight fish.

Measurement Recommendations