A freezing strategy with origins in medical science could be the solution to successfully preserving fresh tomatoes and potatoes so they don’t defrost into mush, with the bonus of reducing energy consumption in the food products sector.
Researchers at the Albany, Calif., office of USDA’s Agricultural Research Service picked up on the isochoric chamber freezing method that an engineering team at UC Berkeley designed for transporting organs to transplant recipients. Cristina Bilbao-Sainz, an ARS agricultural engineer, says the process maintains the cellular integrity of food items because the pressure inside the chamber “doesn’t let the ice continue expanding freely.” Instead, the chamber suspends the vacuum-sealed fresh food in water or another solution and only about 10% of the volume of the chamber freezes, even as the whole chamber is placed in a standard freezer.
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After being brought back to room temperature, the chamber is opened and food is removed — preserved, and undamaged by the process. Bilbao-Sainz says the first test products were foods that deteriorate with traditional freezing, such as tomatoes and potatoes. After one month in the chamber, she says “all the quality properties in terms of texture, color and nutritional content were very similar to the fresh tomato.” Without the need to lower large volumes to below the freezing point, the process consumes less energy than traditional freezing.
As public research continues on the “optimal conditions” for various foods, Bilbao-Sainz says, “we are trying to find partners to work with” to bring the technology to industry.
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