OSU study finds that using cold water to make 'sprouted' foods lowers the risk of salmonella growth

Soaked almonds, sunflower seeds and other grains and nuts.

Grains, nuts and seeds are significant ingredients in the healthy snack segment due to their high-quality protein and “healthy” fats, along with abundant antioxidant, fiber, and mineral content. New products including grains, nuts and seeds that are “sprouted,” “awakened,” and “activated” are perceived to provide added value.

Making "sprouted" foods involves soaking raw ingredients in water overnight, often at room temperature. Soaking softens the hulls and leads to swelling that initiates the activation of enzymes and reduction of antinutrients, which are plant compounds that reduce the body's ability to absorb essential nutrients. Following soaking, these ingredients are typically dried under low temperature and low humidity to maintain their “raw” label, then packaged as either single-ingredient snacks, incorporated into a complex snack – such as granola, bars or trail mix – or pureed into nut or seed butters or as a base for fermented non-dairy “cheeses.”

These foods aren’t really “sprouted” – meaning the root doesn’t actually emerge from the seed, explains Joy Waite-Cusic, an associate professor of food safety systems in Oregon State University's College of Agricultural Sciences. And many of the ingredients used in “sprouted” products have been associated with a number of recalls and foodborne illness outbreaks in recent years. In response, Cusic led a research team to conduct a study to demonstrate the potential for salmonella to grow during the soaking period. A secondary objective was to determine easily implementable and cost-effective controls, such as refrigeration or adding salt during the soaking period to prevent salmonella growth.

For their study, the OSU researchers tested 15 minimally processed grains, nuts and seeds that were either purchased from grocery stores or supplied by local food companies. The foods were inoculated with a “cocktail” that included six salmonella strains associated with tree nut and peanut products. The inoculated grains, nuts and seeds were dried at ambient temperature for 24 hours to return them to their original moisture content. Next, they soaked the inoculated grains, nuts and seeds in either distilled water or salt solutions at various concentrations and temperatures for 24 hours. Also soaked was the control group of uninoculated grains, nuts and seeds.

They found that soaking “sprouted” foods in cold water, rather than the more common practice of soaking at ambient temperature, lowers the risk of salmonella growth on these increasingly popular healthy snack foods. Their study, published in 2021 in Food Protection Trends, demonstrates the risk of “sprouting” practices and presents practical strategies to improve safety of these raw foods, The study provides regulators with clear guidance on the risks associated with this new category of ‘sprouted’ products. “The ambient-temperature soaking process creates conditions that are ripe for salmonella growth. A lot of people are making ‘sprouted’ foods at home, so there’s no reason the same risk doesn’t occur there," said Cusic, who is also OSU Extension’s statewide specialist for home food safety and food preservation in the College of Public Health and Human Sciences.