Cleanthe beef stomach.Though it's more troublesome, thorough cleaning results in better taste and texture after braising. The stomach should be divided first because it is large and contains several sections. Each section should be turned inside out from the opening and washed with clean water to remove impurities and some gastric juice.Addcornstarchto a clean bowl.Mix in salt or baking soda and vinegar, then rub the beef stomach thoroughly to remove all gastric juices and other impurities. Rinse well after.Finally, rinse until clean.