Hi Fiona. To give you a straightforward answer: strictly speaking from a food safety standpoint, you do not have to sear beef before braising, but culinarily speaking, it makes a tremendous difference in the final quality and depth of your stew.
There is a common myth that searing meat locks in moisture, which science has shown is not actually true. The real reason to brown meat is the Maillard reaction. This is the chemical reaction that occurs between amino acids and sugars at high heat, creating hundreds of rich, complex flavor compounds and giving the meat a deep, savory profile. In addition, searing creates browned bits stuck to the bottom of the pan, known as fond. When you deglaze that pan with broth, wine, or water, that fond dissolves into the liquid, forming the foundation of a flavorful, cohesive sauce rather than a watery, pale broth.
Without searing, the meat essentially boils in the liquid. While it will still get tender over time, the meat can look pale and gray, and the stew as a whole will lack that rich, roasted flavor.
Since you are prepping huge batches for the freezer, searing small batches in a skillet can definitely be tedious and messy. A practical shortcut for large quantities is to use your oven. Simply toss your beef cubes in a tiny bit of oil, spread them in a single layer across a couple of rimmed baking sheets, and roast them at 450 degrees Fahrenheit or under the broiler for 10 to 15 minutes until they achieve a deep brown color. You get the benefits of the Maillard reaction across the entire batch all at once with minimal cleanup. Just be sure to scrape any pan drippings into your stew pot as well.
I hope this explanation helps make your prep day easier, and I wish you great success with your batch cooking!
