A federal judge in January, has again upheld U.S. Agriculture Department rules requiring treatment of raw almonds. This was in response to two isolated outbreaks of salmonella, in conjunction with conventional almond farms, one in Canada in 2001, and a second in Oregon in 2004. While contamination in almonds is not common, the industry determined that aggressive measures were necessary to prevent any other occurrences.
While there are four main methods of pasteurizing almonds, steam processing, high heat treatment (roasting), blanching and highly toxic fumigation treatment with propylene oxide (PPO), two of them are the primary methods that are used most often.. These two are steam processing and PPO fumigation.
Here is a hazard summary as reported by the EPA:
“Propylene oxide is used in the production of polyethers (the primary component of polyurethane foams) and propylene glycol. Acute (short-term) exposure of humans and animals to propylene oxide has caused eye and respiratory tract irritation. Dermal contact, even with dilute solutions, has caused skin irritation and necrosis in humans. Propylene oxide is also a mild central nervous system (CNS) depressant in humans. Inflammatory lesions of the nasal cavity, trachea, and lungs and neurological effects have been observed in animals chronically (long-term) exposed to propylene oxide by inhalation. Propylene oxide has been observed to cause tumors at or near the site of administration in rodents, causing fore stomach tumors following ingestion via gavage (experimentally placing the chemical in the stomach) and nasal tumors after inhalation exposure. EPA has classified propylene oxide as a Group B2, probable human carcinogen.”
For more info about pasteurization, see our blog