The TSS value is defined as the amount of sugar and soluble minerals present in fruit and vegetables. The method for its determination by means of a hand refractometer is given below:-

Principle:-

A refractometer is based on the principle of total refraction.

The refractometer should be checked for accuracy before use. This is done by placing a few drops of distilled water on the prism in the specimen chamber of the refractometer with the help of a glass rod after folding back the cover. By looking through the eye-piece with the projection inlet facing towards the light the point on the scale is noted when the boundary line of the shaded area intersects with the unshaded area. If necessary, the eyepiece is rotated to either side for clear reading. The distilled water reading should be zero. If it is not so, it should be set zero with the scale correction knob. The specimen chamber is now cleared with a muslin cloth or tissue paper.

Determination:-

For determining the TSS, a drop of the sample (juice, syrup, etc.) is placed on the prism and the percentage of dry substance in it is read directly. If determinations are made at temperatures other than 20^oC, the reading are corrected to the standard temperature of 20^oC using the correction table.

Q.1 Determinate TSS of the given sample through a Refractometer.

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