Volatile composition and antimicrobial properties of commercial annatto (Bixa orellana L.) extracts, a natural food colorant

The term “annatto” refers to a series of colorant preparations consisting of carotenoid-type pigments, extracted from seeds of the tropical bush Bixa orellana L. Annatto is extensively used as a colorant in dairy products and as a spice in Latin American cooking. In alternative medicine, annatto is used with other herbal extracts for treatment of bacterial infections and other ailments. Given the anecdotal use of annatto as folk remedy and its wide use in the food industry, there is cause to warrant a thorough investigation of the volatile profile and antimicrobial properties of annatto extracts.; The objectives were: to identify and compare the volatile composition of water- and oil-soluble annatto extracts; to determine the antimicrobial properties of commercial annatto extracts against selected lactic, spoilage and pathogenic bacteria; and to identify the compounds responsible for such activity.; Volatile compounds were recovered using dynamic headspace-solvent desorption sampling and analyzed using GC-MS. Compounds were identified by comparison to a mass spectral database, Kovats indexes, and retention times of known standards. Disk diffusion and tube macro-dilution techniques were used to determine the minimal inhibitory and bactericidal concentrations of water-soluble annatto extracts. Screening for antimicrobial active fractions was accomplished through bioautography followed by LC/PDA/MS analysis of active fractions. Structure confirmation was achieved by 1H-NMR spectroscopy.; Volatile compounds detected in annatto extracts consisted mainly of sesquiterpenes, monoterpenes and arenes. Of the 107 compounds detected, β-Humulene constituted the major volatile present in annatto extracts followed by p-xylene, toluene, α- and β-pinene, γ-elemene and spathulenol. Results on the antimicrobial activity demonstrate that annatto has a strong inhibitory effect on Staphylococcus aureus, Bacillus cereus and Clostridium perfringens. Annatto inhibited to a lesser extent the growth of lactic acid bacteria and other selected Gram positive bacteria. No activity was detected against Lactobacillus plantarum, Bifidobacterium bifidum, selected Gram negative bacteria or yeasts. Experimental results strongly suggest that 9 ′cis-norbixin and trans-norbixin are responsible for annatto's antimicrobial properties.; The results show that commercial annatto extracts not only contribute to the color of foods but they have the potential to influence the aroma and the microbial quality of foods that contain them.