Calculating Total Soluble Solids (TSS) in food is typically done by measuring the percentage of dissolved solids using a refractometer. The measurement is usually expressed as degrees Brix (°Brix), which is equivalent to the percentage of TSS.
TSS includes all the sugars, acids, proteins, and other substances that are dissolved in the water content of the food. It's a crucial quality parameter for many food products like fruits, juices, jams, and syrups.
Measuring Total Soluble Solids (TSS)
The most common method for determining TSS in food involves using an instrument called a refractometer. This instrument measures the refractive index of a liquid sample, which is influenced by the amount of dissolved solids present.
Here’s a simple breakdown of the process, based on the principle described:
- Prepare the Sample: Ensure the sample is a liquid or can produce liquid. If the sample is thick, like jam or pulp, you may need to squeeze a small amount of liquid from it, perhaps through a fine cloth or cotton, as mentioned in the reference.
- Apply Sample to Refractometer: Place a few drops of the prepared sample directly onto the prism surface of the refractometer.
- Allow Temperature Equilibration: Give the sample a moment to reach the temperature of the refractometer's prism, as temperature can affect the reading. Some refractometers have automatic temperature compensation (ATC).
- Read the Brix Value: Look through the eyepiece (for manual refractometers) or read the display (for digital refractometers). You will see a line separating light and dark areas, which corresponds to a scale. The point where this line intersects the scale gives you the Brix reading.
- Note the TSS: The Brix reading obtained directly represents the Total Soluble Solids content of the sample.
As stated in the reference:
Place a few drops of the sample in between the prisms and allow the temperature to equilibrate and note the Brix reading, which gives per cent of sucrose sugar or TSS. If sample is thick, squeeze it through cotton and place the drop in between the prisms. The readings are expressed as total soluble solids (TSS) = %.
What is Brix and Why is it Used for TSS?
- Brix (°Brix) is a scale used to measure the amount of dissolved solids in a liquid. One degree Brix is equal to 1 gram of sucrose in 100 grams of solution.
- While Brix is defined based on sucrose, it is widely used as a standard for measuring TSS in foods because sugars (like sucrose, fructose, and glucose) are often the primary soluble solids present.
- For most practical purposes in the food industry, the Brix reading from a refractometer is taken as the TSS percentage.
Factors Affecting TSS Readings
- Temperature: Refractometer readings are temperature-dependent. Using an instrument with ATC or ensuring the sample is at a standard temperature (often 20°C) is important for accuracy.
- Particle Size: The sample should ideally contain only dissolved solids. Suspended solids can interfere with the reading. This is why filtering thick samples might be necessary.
- Type of Solutes: While Brix is based on sucrose, different types of sugars and other soluble compounds (like acids or salts) have slightly different refractive indices. For highly precise measurements of non-sucrose solutions, correction factors might be needed, but generally, Brix is a reliable indicator of overall TSS.
Practical Applications
TSS measurement is vital for quality control and consistency in various food products:
- Fruit Juices: Indicates ripeness and sweetness.
- Jams, Jellies, Preserves: Ensures proper gel formation and shelf-life.
- Syrups & Concentrates: Verifies concentration levels.
- Tomatoes & Tomato Paste: Used to assess quality and yield.
By measuring TSS using a refractometer, food producers can ensure their products meet specific standards for taste, texture, and composition.
