Abstract: To select a blend of strains not susceptible to the current bacteriophage in the cheesemaking plant the cheesemaker inoculates each of the test tubes in the kit with filtered when obtained from current production. Each tube contains a genetically distinct starter culture strain or a culture blend in a sterile milk medium and contains a dye which will change color in the desired pH range. After incubation for ten hours the cultures resistant to the prevailing phage will exhibit the desired color change and will have developed a firm curd. A starter culture now known to be resistant to the prevailing phage can now be selected. Tests show success closely approaching 100% as opposed to 96% (or less) with the traditional rotation method of selecting culture blends.