Both vinegar and lemon juice contain acidic ingredients that can effectively remove black film from tripe. Mix the right amount of vinegar and lemon juice, then dip a brush or cloth into the mixture and gently rub the black film area on the surface of the tripe. The acidic component dissolves the grease and dirt in the black film, making it easy to clean. Once cleaned, rinse with water and dry with a clean cloth. This method is simple and easy to use, and does not require the use of strong acids or corrosive chemicals, which will not cause damage to the tripe.