3. a lab technician is preparing urea broth. it should be sterilized by filtration, he autoclaves it instead, just like he does for any other media. the high temperature of the autoclave causes the urea to break down. what color is the sterile urea b

The sterile urea broth when it comes out of the autoclave will generally be yellow to orange in color. This is because urea decomposes upon heating in the autoclave, which affects the color of the medium. Normally, untreated urea broth is clear and orange-red, and sterilization by filtration is recommended to avoid heat breakdown. The autoclaving process, which involves high temperature and pressure, causes the breakdown of urea and thus changes the color. More specifically, the prepared urea broth before inoculation and without heat damage has a yellow-orange or pale yellow color. After autoclaving, because of the breakdown of urea, it loses its original color characteristics and the medium may exhibit a yellowish coloration rather than the normal orange-red color seen with filtered sterile broth. Urea broth is usually sterile-filtered to avoid such changes and maintain its color and medium integrity. Therefore, the sterile urea broth after autoclaving would typically be yellow or pale yellow instead of the recommended orange-red color it would have if sterilized by filtration.