The reasons are very simple. Specifically, repeatedly reheated or left-standing warm food loses vitamins and nutrients. For this reason, jarred food is also referred to as “dead food,” as it is typically heated at least 2-3 times before reaching the store shelves. A baby doesn’t get as many beneficial nutrients from such food as from freshly warmed puree.
The second reason is food safety. If bacteria have contaminated the food (for example, from utensils or the air; bacteria are everywhere around us), they happily start multiplying in warm puree. If the temperature range of 7-70 degrees is suitable for bacterial growth, room temperature accelerates the proliferation even more. Eating such food can cause health problems.
Additionally, the taste, smell, and texture of the food deteriorate over time, and the baby may no longer want it.
This also applies generally to reheating our everyday food, so eat wisely! And instill good eating habits early on for the little citizens of the world. If you’re short on reheated puree, thawing and reheating BabyCool puree cubes is so quick that making a large quantity in advance isn’t really necessary!
Come read more about baby nutrition on the nutrition blog and about baby nutrition.