Why you should wash peanuts before roasting
 

Washing peanuts before roasting plays an important role in improving their flavor, aroma, and texture. It removes dust and impurities, reduces any undesirable earthy taste, and ensures the peanuts cook evenly, helping them remain crisp. Peanuts are rich in protein and fat, and roasting triggers chemical reactions that give them their signature golden-brown color and nutty aroma.

Roasting dry peanuts can cause uneven cooking, as the exterior heats quickly while the interior remains undercooked. Adding moisture through washing slows down heat transfer, allowing the nuts to roast evenly. In Hanoi, traditional hung liu (basil) peanuts are always washed first, and some recipes even call for rinsing with boiling water before roasting. Proper drainage is essential: excess water slows roasting, darkens the skins, and leaves the interiors moist, while steam can make cooled peanuts absorb water and lose crispness.

After washing, peanuts should be dried thoroughly—either under the sun or using a fan. Traditional hung liu peanuts are sun-dried for several hours to remove earthy flavors and ensure crispness after roasting. If sunlight is unavailable, an oven or air fryer can be used. The roasting process itself greatly affects the final texture. Start with medium heat to avoid burning or cooking too slowly. Once dry, roast the peanuts on low heat while stirring constantly until they crackle. Historically, Vietnamese households used clean yellow sand on low heat to help cook peanuts evenly.

For modern ovens or air fryers, preheat to 150°C and roast the peanuts for 10 minutes, then reduce the heat to 90–100°C for 30–45 minutes, stirring occasionally. After roasting, wrap the peanuts in clean paper or cloth to absorb any residual moisture and maintain crispness. Leaving them in the pan too long can result in bitterness. Allow peanuts to cool completely in a ventilated area before storing them in glass jars or airtight containers; storing them while still warm traps moisture and causes softening.

Washing peanuts before roasting can yield more aromatic and longer-lasting crunchy peanuts compared with dry roasting, provided the nuts are properly dried and roasted. In industrial processing, peanuts are sometimes soaked in a mild salt solution before roasting. This ensures even cooking, makes it easier to remove skins, and enhances flavor. In the U.S., patented nut brining methods involve soaking peanuts in a solution containing at least 10% salt for several hours, which produces crispier, tastier nuts than dry roasting alone.

Environmental factors such as weather and storage conditions also influence peanut crispness. In humid climates, roasted peanuts can absorb moisture and soften quickly. To maintain crunch, store peanuts in dry, airtight containers, optionally with food-grade desiccants. Traditionally, Vietnamese households have sealed roasted peanuts in small jars lined with dried banana leaves to preserve their texture and aroma.

Properly washed, dried, and roasted peanuts will stay crisp and flavorful longer; washing does not cause them to soften prematurely. The key lies in balancing washing, drying, roasting over medium heat while stirring, cooling in a ventilated area, and storing in airtight containers. Following these steps determines whether peanuts remain crunchy for up to a week or quickly lose their crispness.