Natural antimicrobials from plants

Abstract

Food preservation is becoming more complex. New food products are being introduced onto the market. Generally these require longer shelf-lives and greater assurance of freedom from foodborne pathogenic organisms. The search for new substances to be used in food preservation is hampered by regulatory restrictions. Consequently a great deal of time and money may be required to develop a new chemical preservative and to get it approved especially in view of the public pressure against chemical additives in general. Such obstacles provide new opportunities for those seeking alternative routes in the search for new food preservatives. The excessive use of chemical preservatives, some of which are suspect because of their supposed or potential toxicity, has resulted in increasing pressure on food manufacturers to either completely remove chemical preservatives from their food products or to adopt more ‘natural’ alternatives for the maintenance or extension of a product’s shelf life. There is considerable interest in the possible use of such natural alternatives as food additives either to prevent the growth of foodborne pathogens or to delay the onset of food spoilage. Many naturally occurring compounds, such as phenols (phenolic acid, polyphenols, tannins), and organic acids (acetic, lactic, citric) have been considered in this context. Many spices and herbs and extracts possess antimicrobial activity, almost invariably due to the essential oil fraction (Deans and Ritchie, 1987). Thus the essential oils of citrus fruits exhibit antibacterial activity to foodborne bacteria (Dabbah et al., 1970) and moulds (Akgul and Kivanc, 1989) so too have the essential oils of many other plants such as oregano, thyme (Salmeron et al., 1990;Paster et al., 1990), sage, rosemary, clove, coriander etc. (Farag et al., 1989; Aureli et al., 1992; Stecchini et al., 1993). The antibacterial and antimycotic effects of garlic and onion have been well documented also (Mantis et al., 1978; Sharma et al., 1979; Saleem and Al-Delaimy, 1982; Conner and Beuchat, 1984a,b).