Nut storage

HGA recently received enquiries on best practice for storing hazelnuts. Bryan Thomas offered the following advice.

By Bryan Thomas

HGA newsletter October 2010

There can be no doubt that hazelnuts will keep best in-shell provided that the moisture level is reasonably low (4-5%) and the temperature is moderate. Once out of the shell there is potential for contamination from handling, from containers and from airborne material, any of which can initiate deterioration. Such deterioration will proceed more rapidly at higher temperatures and in the presence of moisture.

If un-contaminated, the proteins and oils in the kernel will break down only slowly provided the temperature is low. Therefore the key is to ensure nuts are correctly dried, crack them in a clean environment, using clean utensils and use clean moisture-proof containers, and store at low temperatures (eg fridge). It is also worthwhile washing nuts prior to cracking if there is contamination on the outside of the shells that may get onto the kernel.

A light roasting prior to storage will de­activate fungal or bacterial contamination, BUT it also initiates the deterioration of the oils which, once started, does not stop even at low temperatures, so roasting prior to long term storage is not advised. For the same reason, do not let the nuts get excessively hot prior to cracking.

It is unlikely that anyone would wish to store kernel for longer than one year, and if the above points are followed then there should be no storage losses over that time. While they will still be acceptable after 12 months, many people will detect a change in flavour over that period. Where possible, freshly cracked is better.