Processing of pistachio

Harvesting of pistachio is some regions of the world depend on hand labor. But in California, when most of the nuts are ripe and begin splitting, they are mechanically harvested, cleaned and placed in bins for transport to a processing plant.

Pistachios destined for the fresh market are cooled straight after harvest. All sticks, leaves and other debris and reject nuts are removed before they are graded, hand sorted and packed into polystyrene. The nuts should be stored in a cool room at all times.

Pistachios destined for sale as dried nuts are hulled as soon as possible. Freshly harvested nuts have a moisture content of around 45%. After harvest the nuts are cleaned and dried to around 5% using forced-air drying. Natural air drying can be employed in low humidity and high temperature conditions.

Then hull of the pistachio must be removed within 24 hr of harvest to prevent shell staining. Stained pistachio nuts are less attractive to consumers and have higher incidence of aflatoxin contamination.

After drying, electronic sorters cull out blemished nuts. Good quality splits are graded into four sizes. To achieve the most uniform grades, the size graders operate via a combination of round and slotted holes.  This followed by roasting, salting and packaging. Around 90% of consumer-packed nuts from California are roasted and salted in the shell.

Pistachio is widely used in the pastry, confectionery and ice-cream industries for its pleasing flavor and green color.
Processing of pistachio