Modification of the Method for Identifying Histamine-Forming Bacteria Using Niven Agar with the Double Filtration Preparation Method

The decline in the quality of tuna produces histamine compounds. Histamine is formed at temperatures >4°C. One method for identifying histamine-producing bacteria is carried out using Niven method. The purpose of this study is to create a modification of the Niven method by adding the double filtration method. The modified Niven agar method was applied to tuna samples (cube and ground meat) taken randomly from processing stages located in Jakarta. The determination of the number of histamine-producing bacteria was carried out using the pour plate method on modified Niven agar medium. Observations of bacterial colony growth were conducted at 10, 18, and 24 hours. The research results show that the ALT calculation of sterilized tuna samples indicated that no bacteria grew in those samples, meaning that the colonies grown on Niven media using the modified method were purely BPH colonies intentionally added to the product. Then, the growth results of the two bacteria contaminated in the sterilized tuna (M. morganii and E. aerogenes) showed that bacterial growth was observed at the 10-hour observation. Up to the 18-hour observation, the bacteria were still noticeably increasing in number, and by the 24th hour, a decrease in bacterial numbers began to appear, signaling that the bacteria had passed the stationary phase. The modified Niven agar method using the double filtration method at the preparation stage can be used as a step for screening and identifying BPH, both from single colonies grown in liquid media and in tuna products, with more accurate identification results.