Control of Histamine Formation by Morganilla morganii in Synthetic Media and Mackerel Fish Homogenate Using Blue Green Alga, Spirulina platensis

Histamine, a chemical health hazard, is formed from the amino acid histidine by bacterial histidine decarboxylase.
The effect of Spirulina platensis alga extracts on the population of Morganella morganii and histamine formation
were studied. Among many solvents, diethyl ether extract gave the best inhibition even at the lowest concentration
(1000 ppm) using disc diffusion method. Concentrations of 50-1000 ppm of algal extract were tested against Morganella
morganii in histidine decarboxylase broth (HDB). Significant reduction in the population was noticed at all
the tested concentrations notably at the highest one (1.7 log units). Around 50% reduction in histamine content was
obtained at the concentration of 500 and 1000 ppm algal extract. The highest reduction (>2.5 log units) in M. morganii
count in stored sterilized and raw mackerel (incubated for 48 hrs at 25°C) was noticed at 1000 and 2000 ppm of algal
extract. The dose 2000 ppm significantly controlled histamine formation (>60%) in stored mackerel. These results
open new horizons to control histamine formation at a large scale of fish industry.