ABSTRACT
This research was designed to study the efficiency of non-carbonated soft drink color removal by using granular activated carbon (GAC) for coliform bacteria detection by SI medium. The conditions established in the study were to use 6 color tones of non-carbonated soft drinks (red, green, purple, blue, orange and yellow) which were removed by using 3 GAC amounts (100, 200, 300 mg per soft drink 1 mL) at two contact times of color removal, 30 and 60 minutes. The results showed that a higher amount of GAC and the increasing of contact time significantly increased color removal efficiency at p-value \< 0.05, and that, also, the different color tones of soft drinks significantly affected different color removal efficiencies at p-value \< 0.05. The highest color removal efficiency derived from using 300 mg/mL of GAC amount at 60 minutes, but was not the best suitable for every color tone. The best suitable condition of each color tone was selected from the lowest GAC amount and the shortest contact time for the color removal as well as affected the color of SI medium, which was changed to yellow color for a positive result, but was still purple color for a negative result within 24 hours. Using 200 mg/mL of GAC amount at 30 minutes was the best suitable condition for red-green-purple-orange color tones, using 300 mg/mL of GAC amount at 30 minutes was the best suitable condition for yellow color-tone, and using 300 mg/mL of GAC amount at 60 minutes was the best suitable condition for blue color-tone. The validity of coliform bacteria detection by SI medium for these removed-color soft drinks when compared with the standard MPN method were sensitivity value, specificity value and efficiency of test of more than 80%. Thus, GAC can be used to efficiently remove the colors of soft drinks for coliform bacteria detection by SI medium.