To investigate the heating sterilization indicator bacteria used in the production of “Hyuganatsu” straight juice stored in paper containers using the aseptic method, we examined the degree of contamination by various bacterial spores in the untreated raw material, “Hyuganatsu” juice. In a total of 11 samples, 51 bacterial strains were isolated by aerobic culture, 12 strains were isolated by anaerobic culture, and thermophilic acidophilic bacteria (TAB) were not detected. Among the isolated strains, Paenibacillus spp. were detected most frequently, followed by Bacillus spp., Paraclostridium spp., and Clostridium spp., but these bacteria could not grow in “Hyuganatsu” straight juice (pH 3.1), so there was no need to evaluate them as sterilization indicator bacteria. TAB was not detected in this experiment, but considering past failures and the characteristics of this species, it is necessary to consider TAB as sterilization indicator bacteria. Therefore, in the future, we will conduct a growth test in “Hyuganatsu” straight juice using TAB, and if growth occurs, we will consider it necessary to evaluate TAB as sterilization indicator bacteria by setting the appropriate heating sterilization conditions.