Coliform detection in Indonesian Ragi Tapai as an indicator of unhygienic processes using chromogenic media

Abstract

Coliform bacteria can be used as an indicator for unhygienic conditions related to food processes. Detection of coliform bacteria in Indonesian ragi tapai has been performed using chromogenic media. The chromogenic media were chosen because the reaction is faster and more reliable compared to the conventional media. Fifteen samples of ragi tapai from West Java, Central Java and outside Java region in Indonesia were analyzed for the presence of coliform. The analysis was carried out in Readycult Coliforms (RC) medium using the Presence/Absence test. Incubation temperature was 37 °C for total coliform and 44.5 °C for faecal coliform. The presence of Escherichia coli was confirmed by indole ring formation, fluorescence of medium when exposed to UV light and formation of blue to violet colonies on Chromocult Coliform Agar Enhanced Selectivity (CCA-ES) medium. The positive results showed that from 15 samples, 12 samples (80 %) tested positive for coliform and 3 samples (20 %) tested negative in RC medium. One of 12 samples tested positive for faecal coliform.