Thermal Food Jars

Thermal food jars are small, insulated, stainless-steel vessels that promise to keep food hot or cold on the go. We wondered if any could keep their contents not only palatably hot or cold but also food-safe for several hours since the U.S. Department of Agriculture discourages leaving cooked food between 40 and 140 degrees for more than 2 hours. So we filled six models (priced from $19.95 to $41.99) with a variety of prepared foods—200-degree tomato soup, 150-degree macaroni and cheese, and 38-degree tuna salad—and monitored the temperatures of the foods for 4 hours.

Discouragingly, only three vessels held the soup above 140 degrees for the duration of testing, and no jar kept the macaroni and cheese or tuna salad food-safe for even 2 hours, since the windows between their starting and food-safe temperatures were narrower. Some jars also lost points for durability, spilling when we shook them for 30 seconds and denting when we dropped them while they were in a backpack. Odors clung to the model with an internal plastic container.

If hot soup is all you transport, there was one model that will get the job done. It also cleans up in the dishwasher. But don’t expect any model to maintain food-safe temperatures for very long if its contents don’t start out very hot or very cold.