I trained with a well known French food scientist while living in Paris who taught me searing meat before cooking in vacuum as one method. At the time, I thought it made sense, but now I feel that pre-searing is not ideal. First off, after you sear, you are obliged to cool down the the meat prior to vacuuming in order that the meat doesn’t boil under the low vacuum pressure. The fact that the meat is cooled helps prevent low temperature boiling from occurring.

I cannot see this method applicable for most cuts of meat, but can be useful when cooking scallops given they are small, compact and re-heat easily. For meats, I cook first, and sear later to finish the meat with a hot exterior crust, and I can flavor the meat whichever way I feel best suits the group.