Plant nutraceuticals as antimicrobial agents in food preservation: terpenoids, polyphenols and thiols

Synthetic food additives generate a negative perception in consumers. Therefore, food manufacturers search for safer natural alternatives such as those involving phytochemicals and plant essential oils. These bioactive compounds have antimicrobial activities widely proven in in vitro tests. Foodborne diseases cause thousands of deaths and millions of infections every year, mainly due to pathogenic bacteria such as Salmonella spp., Campylobacter spp., Escherichia coli, Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus. This review summarises industrially interesting antimicrobial bioactivities as well as their mechanisms of action for three main types of plant nutraceuticals, namely terpenoids (e.g. carnosic acid), polyphenols (e.g. quercetin) and thiols (e.g. allicin), which are important constituents of plant essential oils with a broad range of antimicrobial effects. These phytochemicals are widely distributed in fruits and vegetables and are especially useful in food preservation as microbial growth inhibitors.