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Department of Food Technology
SLGTI. Sri Lanka.5/4/2018 Y.BAVANEETHAN. 1
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TOTAL SOLUBLE SOLID (TSS)
• Total soluble solid mean, Amount of total soluble solid present in
the unit volume of solution.
• Measure the sugar content of sugar solutions (honey, juices,syrup)
which the sugar is the major component using refractometer.
-Total soluble solids content of a solution is determined by the
index of refraction.
- This is measured using a refractometer, and is referred to as the
• Sugar concentration is expressed in degrees Brix. At 20°C,
• The Brix is usually consider equivalent to the percentage of
sucrose (sugar) in the solution
• (60° Brix is equivalent to a sugar content of 60%).
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Development of the flesh of a fruit, in many species,
• Nutrients are deposited as starch,
• During the ripening process is transformed into sugars.
• The progression of the ripening process leads to increasing sugar
The method is especially suitable for ripe and juicy fruit, with
significant sugar content,
As the determination of TSS is based on the capacity of sugars in a
juice to deviate light.
with scale for temperature correction
LCD DIGITAL BENCH MODEL
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A refractometer measures TSS as °Brix in 0.1% graduations.
There are hand-held refractometers as well as digital operated
All models apply similar principles.
• Some refractometers automatically compensate for changes in
• whereas others may be calibrated to read accurately at a fixed
temperature (usually 20°C).
To obtain accurate readings at temperatures other than 20°C it is
necessary to refer to the International Temperature Correction
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Use of the refractometer
• Depending on the purpose of the analysis, several drops of
distilled water, sucrose solution or juice are placed on the prism
• The liquid on the prism plate should be free from bubbles or
floating particles of pulp or other matter.
- Hand-held model:
• The prism lid is closed. To get proper readings, the instrument is
turned towards the light.
• If necessary the eye piece is focused until a clear image appears.
• The position at which the demarcation line between the light and
dark regions crosses the vertical scale gives the percentage
soluble solids reading.
- LCD Digital model:
• Push the button to get the soluble solids reading in percent.
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Checking and Calibration
- A bottle of distilled water.
- A small bottle of 6 % sucrose solution (TSS Known solution).
- The solution should be stored in a bottle, kept away from daylight
and used within 48 hrs of preparation.
Several drops of distilled water are placed on the prism surface.
Distilled water should give a reading of zero. If not and where possible,
the refractometer must be adjusted
to read zero.
The prism plate is wiped dry with a soft tissue free from fluffs.
Several drops of 6% sucrose solution are placed onto the clean and dry
The refractometer should give a reading of 6%. If the reading is not
a) A new fresh solution of accurate 6% sucrose may be required.
b) The refractometer may need to be repaired or replaced.
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Checking and Calibration
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HOW TO CALCULATE THE BRIX
1. Collect a refractometer (these should be handled carefully
as they are expensive!)
2. Ensure the refractometer prism surface is clean and dry
3. Place a small amount of fresh juice (a couple of drops is
sufficient) onto the prism of the refractometer.
4. Look through the eyepiece while pointing the prism in the
direction of good light (not directly at the sun).
5. Focus and take the reading of where the base of the blue
colour sits on the scale and record the % percentage sugar
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Digital handheld refractometer – Brix meter
Digital handheld refractometer with 5-digi.
Measurement of liquid media from low to high viscosity.
Handy design, simple operation, reliable, automatic
temperature compensated brix value within +5 to 70 °C.
Various models are available, e.g. for applications like honey,
wine, saline, glycol.
• Perfect refractometer for field analysis
• Application specific scales
• 5-digit, full view LCD screen
• Results displayed in 2 seconds
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Visual handheld refractometer
Handheld refractometers are classic, visual refractometers
and are used for the determination of the refractive index of
liquid media of low or high viscosity.
They are mainly used for quick on-the-spot-control of
process streams and the field analysis in fruit and vegetable
Different models of handheld refractometers for special
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Designed for the determination of the refractive index of
liquid media with high or low viscosity.
It is used in the fast control of liquids and the “in-field
The ABBE refractometer AR12 is equipped with hose
connections at the prism unit for the thermostatisation of the
The temperature is measured with a digital thermometer.
The measuring principle is based on the law of Snellius (law
of refractive index) and is able to measure with transmitted
or totally reflected light.
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Applications in food industries
1. Refractometers are used to assess the ripeness of fruits, vegetables,
sugar cane and beet before harvesting.
• To find the maturity index.
• It measures the sugar content of the fruit in Brix .
• One degree Brix (1% Brix) mean, 1g sucrose in 100g of sucrose water
2. They are used to check the alcohol content of wine and beer during
fermentation in breweries.
• Special refractometers with scales calibrated to give the alcohol content
directly are available.
3. Quality of honey can be checked using special refractometers which
directly give the amount of water in honey.
• If the % of water is high (>20%) then it leads to fermentation by wild
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4. Refractometers are used to monitor and control the quality of,
• yoghurt, jam, fruit extract, syrup, coffee extract, chocolate, milk,
baby food etc.
• by measuring the total solids in them during processing.
5. The refractive index is an indicator of purity in products such as
vegetable oils and animal fats.
• By comparing the values with the standard the purity of the
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