Tree nuts such as almonds, walnuts and pistachios have high nutrient contents including natural antioxidants and unsaturated fatty acids and are recognized as healthy snacks. California is one of the main production area of tree nuts in the world with larges bearing acreage, production volume and economical revenues. Post-harvest processing of tree nuts is very important for ensured product quality and safety. Our research works on tree nuts processing include drying, roasting and pasteurization.