CALIBRATION AND SHELLING NUTS

months*

The shelling of the hazelnuts aims to eliminate the shell while keeping the kernel intact; for this reason, the hazelnuts are previously divided into homogeneous sizes. The sorting is carried out using a nut calibration machine (calibration sieves) that uses standard diameter of rotating perforated cylinders with holes of increasing diameter (eg 17-18-19-20 mm, Fig. 5.1). Once batches of homogeneous caliber have been obtained (Fig. 5.1), they are sent to shelling machines equipped with rotating and fixed grooved rollers, at an adjustable distance according to the size of the hazelnuts.

After shelling, kernels are cleaned by means of ventilation systems, screens and acoustic resonance machines that separate whole seeds from the broken ones, from pieces of shell and from any other solid impurities. The acoustic resonance sorting machines are equipped with a foreign body detection device, which works by recognizing the resonance frequency produced by whole seeds, which is different from that of shells, unshelled or partially shelled hazelnuts, stones and fragments of glass and metal.

*Fondazione Edmund Mach-IASMA: weight loss of 0,1 % after 14 months of storage

Another effective method to preserve quality characteristics is the storage in refrigerated, vacuum-packed environments. Placed inside envelopes or big-bags after flushing with nitrogen and subsequent heat sealing of the packages, hazelnuts can be kept under vacuum for 9 months at 3-4 °C, and for 7 months if stored at room temperature.