Calibration is the mechanical or optical sorting of fruit, berries, pulses or nuts into defined size classes by diameter, weight or count, ensuring uniformity of appearance, processing behaviour and pack fill across a production lot.
In trade practice
Grading machines using roller gaps, vibrating meshes or camera-based optical sorters separate product into size fractions; the chosen fraction is then declared in the specification as a diameter range or count per unit weight. Buyers in the frozen and dried fruit sectors specify calibration to ensure even heat transfer during freezing or drying and consistent portion weights in retail packs. A common error is measuring calibration on a small sub-sample that does not represent the full pallet, leading to disputes at goods receipt. For pulses such as chickpeas, calibration is expressed in millimetres and directly affects cooking uniformity and canning yield.
In a specification
A specification should state the accepted size class as a diameter range in millimetres or a count per kilogram, the permitted tolerance for off-size pieces, and the sampling method used to verify compliance at origin and destination.