IsoGard : A natural anti-microbial agent derived from white mustard seed

A natural preservative from white mustard (Sinapis alba) has been developed under the brand name IsoGard . The essential oil is extracted from moistened, ground white mustard seeds by supercritical fluid extraction. Grinding the wet seeds activates the enzyme myrosinase, which hydrolyzes the glucosinolate (sinalbin) naturally present in white mustard seeds, to yield the active anti-microbial agent, 4-hydroxybenzyl isothiocyanate (4HBITC). The essential oil contains ∼25-35% by weight of 4HBITC. Microbial challenge studies have demonstrated that IsoGard is an effective anti-microbial agent at relatively low usage levels. Challenge tests in an acidified fruit drink against gram-negative, acid-tolerant bacteria (Gluconobacter species) and preservative-resistant yeast (Zygosaccharomyces bailii) showed that a 4HBITC concentration of 25 mg L -1 was sufficient to stabilize the product for 28 days against microbial growth at ambient temperature. A bactericidal study in neutral pH peptone broth under refrigerated conditions (6.5°C), demonstrated that IsoGard acts against various pathogenic and spoilage bacteria, including Escherichia coli, Staphylococcus aureus, Campylobacter jejuni, Pseudomonas aeruginosa, Salmonella enteritidis, Listeria monocytogenes, Shigella boydii, and Clostridium perfringens. 4HBITC concentrations of 60-120 mg L -1 produced a 2-4 log reduction in microbial counts while 360 mg L -1 gave a > 6 log reduction. When injected into beef steaks as part of a brine, an initial 4HBITC concentration of 46 mg L yielded a one log reduction in aerobic plate count (28 days, 5-10°C). To dispense low levels of the anti-microbial into foods and to stabilize the 4HBITC, which is unstable in the presence of water, different IsoGard formulations have been developed. The active compound contributes a mild heat sensation to food products that are tasted fresh. The heat dissipates during storage or cooking of the product as the 4HBITC is hydrolyzed in the presence of moisture. IsoGard has future potential as an all-natural preservative.