When you buy meat, it often comes in vacuum-sealed packaging, making it tempting to put it straight into the sous vide bath. While this seems efficient, I do not recommend it for three important reasons.

• The plastic used in retail packaging is often not heat-resistant. This creates a risk of chemicals leaching into your food, or the plastic breaking down, leaking, or even fusing to the meat. The original seals are also prone to failure under heat. Additionally, the adhesives used for labels are rarely heat-stable and can dissolve into the water, which risks clogging your immersion circulator.
• Cooking in the store packaging prevents you from salting the meat beforehand. Proper seasoning is essential for optimal flavor, juiciness, and texture. My own experiments have repeatedly confirmed the importance of pre-salting, and you can read the details of those results here.
• Meat can develop off-odors when kept in retail vacuum packaging. These are caused by harmless bacteria that thrive in oxygen-free environments. You should always remove the meat from the original bag and rinse it before cooking to ensure these unpleasant smells do not end up on your plate.