Making Walnut Drying More Energy Efficient
Packed with protein, antioxidants, essential vitamins, and minerals, walnuts are a powerhouse component of a heathy diet.
However, before these nuts even reach the grocery store, they must be harvested, washed, dried, and dehulled—all of which uses lots of energy. One of the most energy-hungry steps involves hot-air drying.
In Albany, CA, ARS researchers teamed with University of California-Davis scientists to devise a thriftier approach using infrared heat. Drying walnuts with hot air takes more than 24 hours and uses significant amounts of natural gas and electricity.
In commercial-scale trials, pre-drying the walnuts with infrared heat before regular hot-air drying shortened the total time by 35 percent and saved up to 25 percent of the energy normally used. That’s no small feat considering California produces 99 percent of U.S. walnuts—or about 570,000 tons annually. Infrared drying may also work with other types of nuts like pistachios.