Post-harvest 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.
Post-harvest of pistachio

Sun Drying Method

Sun Drying Method
Sun or drying is still used in hot climates for the production of dried fruits or nuts. This may be done in direct sunlight or in shaded areas where the drying is accomplished by the hot dry air.

It should be apparent that sun dried, fruit is produced only in areas where the climate provides periods of relatively high temperatures, relatively low humidities, and little or no rain fall.

Prunes, grape, apricot, peaches and pears are dried in this manner. Some of these fruit are also dried in tunnel or cabinet dehydrators.

In sun drying, small fruits are prepared and spread on trays to dry in the sun for several days, then stacked to complete the drying cycle in shaded areas.

Larger fruits such as apricots, peaches and pears are halved and pitted and apples are peeled, cored and sliced prior to drying. Such fruit are sulfured to prevent enzymatic browning.

Sun drying times vary between 4 and 25 days, depending on the size of the product, the type of pretreatment, and so on. During sun drying, precautions must be taken to prevent contamination from wind blown dust and dirt.

Moisture contents in the sun dried products vary between 10% and 35% depending on the tendency on the dried product to absorb moisture. After drying, some fruit may require moisture-vapor-proof container.
Sun Drying Method