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Infrared-based approach explored for keeping almonds safe to eat.

In brief: giving almonds a burst of infrared heat, followed by a stint of hot-air roasting, helps make sure the tasty, healthful nuts remain safe to eat. that's according to studies by USDA engineer and ASABE member Zhongli Pan, above right, and his colleague, microbiologist Maria Brandl, who have dubbed this almond pasteurizing technique SIRHA, short for "sequential infrared and hot air."

Findings from laboratory experiments show that a chemical-free process offers a simple, safe, energy-efficient, and environmentally friendly way to reduce Salmonella enterica to levels generally recognized as safe.

All almonds processed for sale in the United States today are treated with some kind of pasteurization process in order to zap Salmonella, even though it's generally thought that almonds are only rarely contaminated with this pathogen.

Nearly a half-dozen almond pasteurization methods already have federal approval, but many almond processors remain eager to learn about new options, including SIRHA and its promise of fast, reliable, and relatively economical pasteurization.

According to results from dozens of volunteer taste-testers who participated in the studies, infrared heating doesn't detestably alter the mild taste, smooth texture, attractive appearance, or other characteristics that make almonds one of the most popular tree nuts.


With further work, SIRHA should be easy to scale up for use at packinghouses, Zhongli Pan reports. Most packing-houses are located in California, where all of America's commercial almonds -- and 80 percent of the world's supply -- are grown.

Some almond packinghouses already use infrared heating, but not for pasteurizing, Pan notes.

The idea of using infrared heating to kill germs isn't new. But studies that Pan and Brandl reported in peer-reviewed articles in the Journal of Food Engineering in 2010 and 2011 and in the Journal of Food Protection in 2008 are likely the most comprehensive investigations of the use of infrared heating to pasteurize almonds and knock down Salmonella.

Infrared technology seems to pose few if any drawbacks. Of course, packinghouses would have to invest in infrared equipment and deal with the learning curve. But no license to own or use the equipment is needed, and extensive training is not required.

Before this pasteurization process makes its way into the packinghouse, pilot-scale and in-the-packinghouse testing will be needed to gather the data necessary for federal review and approval. That might take anywhere from one to two years or more, Pan estimates.

Once that happens, perhaps infrared heating will become tomorrow's top-choice technology for pasteurizing America's almonds.

For more information, contact Marcia Wood, USDA-ARS, Public Affairs Specialist, Marcia,
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Title Annotation:update
Publication:Resource: Engineering & Technology for a Sustainable World
Date:May 1, 2012
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