Growth Rate and Histamine Production of Citrobacter freundii CK01 in Various Incubation Temperatures

Department of Fisheries, Faculty of Agriculture, Universitas Gadjah Mada

^* Corresponding author: indun_dp@ugm.ac.id

Abstract

Improper handling and temperature fluctuations during postharvest of fish commonly allow the growth of histamine-forming bacteria (HFB) that may cause histamine poisoning. Citrobacter freundii CK01 is one of the HFB isolated from Skipjack landed on Sadeng, Yogyakarta. This study aimed to determine the temperature effect on the growth rate and histamine production by C. freundii CK01. Bacterial growth and histamine production was tested in tuna fish infusion broth (TFIB) at 5, 15, 30 and 40°C. The bacterial growth was tested using Total Plate Count method, while histamine was determined using Thin Layer Chromatography and densitometry method. The primary model for bacterial growth was plotted with incubation time using DMFit referred to Baranyi & Roberts model. The secondary model was converted from growth rate and modeled using Ratkowsky Square Root Model. The equation for growth rate of C. freundii CK01 was μmax=[0.0105 (T + 13.886)]² (Root Mean Square Error <10%). Histamine production reached the highest concentration at 15°C in 96 hours up to 117,13 ppm. This study shows that temperature affected the growth rate and histamine production of C. freundii, indicating the importance of maintaining the low temperature stability during handling of skipjack.