Many low-temperature cooling processes below 32°F (0°C) traditionally have used ethylene glycol-based water mixtures. These heat transfer fluids have been around for more than four decades, and their performance is understood. However, ethylene glycol is highly toxic if ingested and therefore cannot be used in food processing systems. Because of its toxicity, there has been a general shift away from ethylene glycol and toward less harmful materials.

The most common replacement is propylene glycol, which is nontoxic and is “generally recognized as safe” by the U.S. Food and Drug Administration (FDA) for use in food, cosmetics and medicine. Other heat transfer fluids include hydrocarbon blends, silicone fluids, calcium chloride and other brine solutions.