Digital Refractometer for Measuring Sodium Chloride in Food

This Hanna Instruments digital refractometer measures salt content in brines, sauces and processed food.

Why it is measured

Salt does three jobs at once — flavour, preservation and texture — and a brine that drifts changes all three. It also has to be declared on a label, which makes it a number with legal weight rather than a matter of taste.

Where it is used

• brine and curing operations
• sauce and condiment production
• cheese making
• food quality control

How a refractometer works

Light bends by a different amount depending on how much is dissolved in a liquid. A refractometer measures that bend and converts it to a concentration scale. It needs one or two drops, gives an answer in seconds, and has no reagents and nothing to consume.

A digital instrument compensates for temperature automatically, which is the difference that matters: refractive index shifts with temperature enough that an uncompensated reading in a warm room is simply wrong.

Practical note

The scale assumes salt is what is dissolved; sugar, acid or thickener in the same sample will bias the reading upward.

Supplied as one model.