Trialling dry hulling of raw pistachios to improve pistachio processing (PS13000)

What was it all about?

The current method of pistachio hulling, wet hulling and drying, is both capital- and processing-cost-intensive, especially as it is only required for a four to six week period each season. Furthermore, the Australian pistachio variety Sirora has uneven maturity and unripe nuts must be separated from the rest with a loss of value to the grower.

This project, which ran from 2014 to 2016, sought to determine the methods and equipment needed to effectively replace or supplement the current wet hulling methods with a dry hulling method.

Specifically, it investigated…

• The feasibility of dry hulling of pistachios prior to wet hulling
• Methods of separating inadequately hulled pistachios, allowing them to be returned for hulling
• The optimal drying processes to maximise pistachios with the desirable wide splits. 


The major outcomes from the project included…

• An unacceptable level of nut damage during the hulling process was found from tests of three dry hullers
• In hull nut separator machinery made in Iran proved very successful at recovering unhulled nuts, and, in 2015, was installed in the major Australian pistachio processing plant, along with pre-dryers.
• Data on drying pistachios through various techniques improved understanding of how to maximise wide nut splits in stored pistachios
• Adding pre-dryers to provide moisture control prior to use of the in hull nut separator increased the higher value wide splits, as well as increasing drying capacity at the processing plant
• Gaining a better understanding of the operating cost of each element of the drying process will assist with future capital expansion and drying improvements.