Super random, but if you like almonds, you might find it useful.
In 2001 and 2004 there were a couple salmonella outbreaks involving huge California almond farms. In 2001, an almond related salmonella outbreak infected 168 people, tracing the origin to large California almond farms. The 2004 outbreak infected 29 known consumers and hospitalized seven people with no fatalities. This incident spurred the recall of 13 million pounds of almonds world wide, and instigated new legislation making pasteurization mandatory for all commercially grown/sold almonds in the United States. Pasteurization is now carried out in three different ways, propylene oxide fumigation, high heat, and steam pasteurization. This ramble will look at those three methods.
Lets start with a quote from the USDA. Source
It’s generally thought that almonds are not naturally contaminated with high levels of this pathogen. Nevertheless, all almonds processed for sale in the United States today have to be pasteurized in order to zap Salmonella.
So, under federal law, your almonds are typically pasteurized with propylene oxide or steam.Under Federal Law and through the Almond Board of California (ABC), almond handlers shall subject their almonds to a treatment process or processes that achieve, in total, a minimum 4-log reduction of Salmonella bacteria prior to shipment in North America (U.S., Canada, and Mexico). The ABC acknowledges that only treatment processes that have demonstrated a 5-log reduction of Salmonella bacteria, as acknowledged by a letter of determination issued by the Food and Drug Administration, meet the definition of “pasteurization.” However, to ease reading of this content when referring to a treatment process that achieves a minimum 4-log reduction of Salmonella bacteria, the word “pasteurization” is used as a generic term.Source
Propylene Oxide fumigation. What is propylene oxide? Check out what the EPA says about it, then tell me if you want this crap used in your food processing? What's worse, the minute risk of salmonella, or the guaranteed exposure to what the EPA classifies as a Group B2, probable human carcinogen? It seems other countries are a bit more intelligent, with propylene oxide being banned in the European Union, Canada, Mexico and many other countries. Almonds with the organic designation are not subject to this processing.
A quote from the USDA website about propylene oxide residues in humans and soil. Bear in mind, that this link is from Balchem, who's front page slogan is "ARC Specialty Products is a leader in packaging and distributing of hazardous chemicals." It's author, Tom Griffith, is the vice president of Balchem. The co-author, Morris Warren, is the founder of the company, who has been the sole registrant for propylene oxide since 1984. (Source)Acute exposure of humans and animals to propylene oxide has caused eye and respiratory tract irritation. As a respiratory irritant, coughing, dyspnea (difficulty in breathing), and pulmonary edema may result from inhalation exposure and possibly lead to pneumonia. Dermal contact, even with dilute solutions, has caused skin irritation and necrosis. Propylene oxide is a mild CNS depressant. Acute exposure to high concentrations may cause headache, motor weakness, incoordination, ataxia, and coma in humans. Tests involving acute exposure of rats, mice, guinea pigs, and rabbits have demonstrated propylene oxide to have moderate acute toxicity from inhalation, high acute toxicity from dermal exposure, and moderate to high acute toxicity from ingestion.
Some slides from a study looking an Propylene Oxide sorption in various nuts. It looks like it does dissipate pretty well in Almonds over a few days. (Source) I guess the question to be asked is, would you rather take your chances with the rare salmonella occurrence, or some known carcinogen?The allowable residue tolerance for propylene oxide is 300 ppm. However, these residues are not persistent as they will evaporate rapidly from the substrate due to the relatively high vapor pressure of propylene oxide. Furthermore, propylene oxide will react in the human stomach to form (GRAS) propylene glycol. A research program was established utilizing radio labeled propylene oxide for 100% accuracy and irrefutability.
The test was conducted in two parts: 1) Using simulated stomach juice at pH 1.0, the PPO half life was 63 seconds. 2) Using human stomach juice at pH 1.5, the PPO half life was 111 seconds.
Notes: All PPO converted to (GRAS) propylene glycol. No propylene chlorohydrin, a suspected by-product, was found. These facts indicate that propylene oxide is not likely to be carcinogenic or harmful.
The conversion of propylene oxide to propylene glycol is catalyzed by both acid and base and the rate of reaction is determined by the concentration of the catalyst. This is also why propylene oxide will hydrolyze to propylene glycol in the soil. Both propylene oxide and propylene glycol are biodegradable.
These are the steps in propylene oxide pasteurization. They aerate to PPO levels <300, then discontinue. I wonder what the average propylene oxide levels are when nuts are packaged and distributed?
Chamber temperatures in the above described pasteurization are between 140-145 degrees, similar to almond roasting temperatures without propylene oxide. This study roasted almonds at similar temperatures, and found increases in oxidized lipids and furan compounds from sugar degradation. I don't have full access to this article, but here is the abstract. And here is a nice summary of dietary and environmental furan exposure.
This study took a look at the effects of the various pasteurization and roasting methods on the anti-oxidant properties found in almond skins. The study was funded by the USDA and a grant from the California Almond Board.
PPO=propylene oxide S1 and S2 are high temperature steam Clearly, raw is superior to PPO or steam pasteurization, but not by as much as I expected, given the hysteria over the pasteurization.
This same study found that storing these same nuts for periods of up to 15 months increased anti-oxidant capacity, but consequently lost over 85% of their vitamin E content. A 20 fold increase was seen in pHBA, a compound that can mimic estrogen to some degree. Quercetin-3-galactoside, a compound linked with all sorts of interesting things, increased 310% at 15 months
With the aging process also came lipid oxidation, with 35-40% increase in lipoxygenase activity and malondialdehyde. (Bad stuff)
Lessons? Draw your own conclusions. But it would seem that nature, once again, is far smarter than man. And......almond flour is retarded.