Natural antimicrobials as additives and ingredients for the preservation of foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 145

essential oils of cinnamon, eugenol and cinnamic aldehyde, were more effective
inhibitors of A. niger growth and toxin production than the parent spices. Azzouz
and Bullerman (1982) evaluated 16 ground herbs and spices at 2% against
nine mycotoxin-producing Aspergillus and Penicillium spp . The most effective
antifungal spice evaluated was clove, which inhibited growth at 25°C by all
species for over 21 days. Other studies reporting antimicrobial effects include
those of Al-Khayat and Blank (1985), Ting and Deibel (1992), Bahk et al. (1990),
Smith-Palmer et al. (1998), Stecchini et al. (1993) and Deans et al. (1995).

6.5.6 Vanillin
Vanillin (4-hydroxyl-3-methoxybenzaldehyde) is a major constituent of vanilla
beans, the fruit of an orchid. It has been shown to possess antimicrobial activity
(Beuchat and Golden 1989). Jay and Rivers (1984) reported that vanillin was
most effective against moulds and non-lactic Gram-positive bacteria. López-Malo
et al. (1995) demonstrated in various fruit-based agars good inhibition of fi ve
species of Aspergillus . Cerutti and Alzamora (1996) demonstrated complete
inhibition for growth of three yeast species in both laboratory media and apple
purée by 2000 μg/ml vanillin. In contrast it was not effective in banana purée,
thought to be due to binding to banana protein or lipid.

6.5.7 Linalool and carvacrol
Sweet basil essential oil has some antimicrobial activity due to the presence of
linalool and methyl carvacrol (Wan et al. 1998). Lachowicz et al. (1998) evaluated
essential oils of sweet basil ( Ocinum basilicum L.) extracted by distillation against
33 bacteria, yeasts, and moulds in an agar well assay. The essential oils were
active against certain fungi including Mucor and Penicillium species but
demonstrated no or little activity in the assay system. Pattnaik et al. (1997) tested
antimicrobial activity of fi ve aromatic constituents of essential oils (cineole, citral,
geraniol, linalool and menthol) against a wide range of bacteria and fungi species.
Linalool was most effective against bacteria followed by, in descending order of
effectiveness, cineole, geraniol and menthol.

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6.5.8 Terpenes
Tea tree oil (an essential oil of the Australian native tree Melaleuca altenrifolia )
has long been regarded as a useful topical antiseptic agent in Australia and
its antimicrobial activity has been demonstrated (Gustafason et al. 1998). The
major active ingredients of tea tree oil include terpinen-4-ol, γ -terpinene,
α -terpinene, α -pinene, 1,8 cineole and linalool (Gustafson et al. 1998; Hammer
et al. 1999). Bactericidal effects are apparent against E. coli (Gustafason et al.
1998). Hammer et al. (1999) reported both cidal and static effects against bacteria
and yeasts.