The common pawpaw is the largest edible native fruit of North America. It holds many colorful names, such as wild banana, prairie banana, Indiana banana, Hoosier banana, West Virginia banana, Kansas banana, Kentucky banana, Michigan banana, Missouri banana, the poor man’s banana, Ozark banana, and banango. Confounding this is the papaya, which is sometimes called a “pawpaw” in the Southern Hemisphere, but this is not the same fruit as the common pawpaw in the United States.
The pulp of the pawpaw fruit is delicious and can be eaten raw. The flavor is tropical and is best described as a blend of banana, pineapple, and mango. The texture is custardy. Chilled pawpaw fruit was a favorite dessert of George Washington, and Thomas Jefferson planted it at Monticello. The Lewis and Clark Expedition sometimes subsisted on pawpaws during their travels. The skin and seeds contain high levels of acetogenins and are not edible.
A pawpaw tree flowers after 8-10 years and must be pollinated by carrion flies. If successfully pollinated, fruits begin to appear after June. The fruits ripen during September to October, and then fall to the ground. Because of the short ripening period and because the fruits spoil quickly (often a matter of a few days), the common pawpaw does not make an appearance in supermarkets and the commercial food supply chain. Ripe pawpaws are best found in the early Fall at festivals in the midwest, at smaller farms and orchards that grow them, or by simply taking a hike through its natural habitat.
The common pawpaw (Asimina tribola) is a member of the Annonaceae, which also includes the soursop, cherimoya, sweetsop, and custard apples. The common pawpaw is unique however, because it is not a tropical fruit, rather, it thrives in the United States in a temperate region covering 26 states. The region generally extends from Missouri to the Potomac River, not much further south than Natchitoches, Louisiana, and not much further north than PawPaw, Michigan. Here in New York state, the natural habitat is only along the eastern shore of Lake Erie, and this is where we forage most of our pawpaws for Mohawk Spirits.
Simply put, vacuum distillation reduces the amount of heat required to distill a “wash” of fermented material . A mechanical vacuum significantly lowers the vapor pressure of the wash, which also decreases the boiling point. The deeper (lower) the vacuum, the easier it is to boil the water-alcohol mixture at room temperature. Since little to no heat is required to initiate boiling, the volatile compounds in the wash are not denatured by heat.
The exciting process of distillation under deep vacuum poses a few technical challenges:
- Glassware must have thick walls (“heavy wall”) to reduce implosion hazards;
- The mechanical roughing vacuum pump must have a series of traps to prevent pump oil from backstreaming into the wash, and to prevent the distillates from entering the pump oil;
- The pressure requires careful control, as the vacuum level is not static and changes as the wash boils. As volatiles are stripped from the wash, the boiling point also shifts.
- All glass joints have to be sealed with a nonhazardous high-vacuum sealant, but the glass joints must be easily disassembled for cleaning;
- There is a small latent heat of vaporization (enthalpy) that must be overcome before the wash boils, even with a deep vacuum. Cavitation sources and starting with a room temperature wash usually expedites this with no additional heat.
- Condensers must use refrigerated glycol chillers, as tap water is usually not cold enough; and,
- The cost of glassware exponentially increases as the pot capacity increases, with an upper limit around 200 liters.