Inhibitory effects of safflower and bitter melon extracts on biogenic amine formation by fish spoilage bacteria and food borne pathogens

Abstract

The impact of safflower (Carthamus tinctorius) and bitter melon (Momordica charantia L.) extracts on growth of fish spoilage bacteria (Acinetobacter lwoffii, Pseudomonas oryzihabitans, Enterobacter cloacae, Shigella spp., Morganella psychrotolerans, Photobacterium phosphoreum) and food-borne pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Enterococcus faecalis, Salmonella Paratyphi A) and their biogenic amine formation were investigated in mackerel infusion decarboxylase broth (MIDB). The broth microdilution method was used to test antimicrobial activity of extracts. Ent. faecalis was the most susceptible microorganism with minimum inhibitory concentrations (MIC) of 6.25 mg/mL against safflower extract, whilst bitter melon had the highest inhibitory effect against growth of Ent. cloacae, Shigella spp. and Ent. faecalis with MIC of 12.5 mg/mL. Differences in ammonia (AMN) and biogenic amine (BA) production among groups were statistically significant (p < 0.05). Ent. faecalis (2810 mg/L) was the main tyramine producer in MIDB. Although the effect of extracts varied depending on the bacterial strain and specific amine, both extracts generally decreased AMN and BA accumulation by bacteria. Histamine production by Phot. phosphoreum was considerably suppressed in the presence of extracts (p < 0.05). As a result, safflower and bitter melon extracts could be used as antimicrobial agents to inhibit bacterial growth and their BA formation in food.