Steam pasteurization. In September 2007, the USDA began requiring that all almonds grown in California and sold as raw in the United States be sanitized via pasteurization. Currently there are two main methods being used to pasteurize the almonds. One uses steam to sanitize the nuts, while the other uses the chemical, propylene oxide, aka PPO, which is considered a possible carcinogen. Most conventional almond growers pasteurize their almonds using PPO. We choose to take extra care and source almond that are pasteurized using steam, which is a much safer alternative to the PPO both protecting you and the nutrients of the almonds themselves.