Standard Error of Prediction

What is the accuracy of NIR measuring brix?

The accuracy of this type of equipment is often described in term of the Standard Error of Prediction or SEP. A SEP of 0.5 means that 67% of the fruit will be within +/- 0.5 brix of the estimated value and 95% will be within +/- 1.0 brix.

The accuracy of this equipment depends on the type of fruit with a SEP of 0.5 being typical. By comparison, brix measured by a digital refractometer from a juice sample may typically have a SEP of 0.2.

The SEP for hand held refractometers are much more variable due to the individual interpretation of the scale of measurement in hand held refractometers.