Ziplock bag open so that air can get out?

Our corporate chef has  received the following question : “I recently read on a webpage that when cooking a sous vide steak, you should leave the top of the ziplock bag open so that air can get out. I haven’t read or heard of this elsewhere in cooking sous vide. Do you mind to let me know your thoughts on this?”

We share Enrique Fleischmann’s thoughts on this:

It is true that the pressure of the water on the bag makes air get out if the bag is open. From an amateur point of view, this could be useful to cook by immersion, as this would prevent the bag from floating in the waterbath.

From a professional point of view, this method is not an applicable resource. One one hand, we don’t know the obtained and necessary vacuum percentages. On the other hand, we don’t have the seal that would guarantee product safety during the cooking process.

To sum up, the use of ziplock bags would be a valid alternative for domestic use but never for commercial use. This method cannot replace sous-vide cooking with all its advantages.

The possibility to measure the real vacuum values of our recipes is one of the pillars of the success of quality sous-vide cooking. This can only be guaranteed when working with validated commercial equipment.