Natural antimicrobials as additives and ingredients for the preservation of foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 144

reported that cavacrol enhanced the antimicrobial activity of nisin against growth
of L. monocytogenes and B. cereus . It should be noted that both thymol and
cavacrol have antioxidant properties (Aeschbach et al. 1994). Other studies
reporting antimicrobial effects include those of Zaika and Kissinger (1981),
Karapinarv and Atkug (1986), Kim et al. (1995), and Firzouzi et al. (1998).

6.5.4 Borneol
The active antimicrobial fraction of sage and rosemary is borneol and other phyto-
phenols of the terpene fraction. At 2% in laboratory media, sage and rosemary
were more active against Gram-positive than Gram-negative bacteria (Shelef
et al. 1980). The inhibitory effect of both spices at 0.3% was bacteriostatic while
at 0.5% it was bactericidal against Gram-positive strains. Pandit and Shelef (1994)
studied the antimicrobial effectiveness of 18 spices against the growth of
L. monocytogenes in culture medium. The most effective compound was 0.5%
rosemary, which was bactericidal. The fraction of rosemary essential oil that was
most inhibitory was α -pinene. Smith-Palmer et al. (1998) reported that rosemary
and sage (0.02-0.05%) were inhibitory to Gram-positive bacteria such as
L. monocytogenes and S. aureus but not to Gram-negative bacteria. Thomas and
Isak (2006) described a strong synergy between nisin and rosemary extract which
enhanced both the bactericidal and bacteriostatic effects against L. monocytogenes
and B. cereus in both bologna and carbonara sauce. This has resulted in the
introduction by Danisco of a commercial preparation, Novagard® NR-100, which
is a patented blend of nisin and rosemary extract. Ponce et al. (2010) studied the
effect of oregano and rosemary extracts on native fl ora on sliced and grated carrots
against E. coli 0157:H7. Inhibitory effects were recorded but only at a high level
that had an adverse taste effect on the carrot.

6.5.5 Eugenol and cinnamic aldehyde
The major antimicrobial components of cinnamon and clove are cinnamic aldehyde
(3-penyl-2-propenal) and eugenol [2-methoxy-4-(2-propenyl) phenol] respectively.
Cinnamon contains 0.5-1.0% volatile oil of which 75% is cinnamic aldehyde and
8% eugenol, while cloves contain 0.5-1.0% volatile oil, 95% of which is eugenol
(Bullerman et al. 1977). Zaika and Kissinger (1979) demonstrated that clove at
0.5% in a bologna culture inhibited growth and acid production by a lactic acid
bacterial starter culture. Cinnamon (0.8%) in the same product moderately
inhibited growth. Ting and Deibel (1992) reported that up to 0.3% cinnamon had
no inhibitory effect against L. monocytogenes at 24°C, whereas Bahk et al. (1990)
found that 0.5% cinnamon was effective against L. monocytogenes in tryptose
broth at 37°C. Antifungal activity against Penicillium, Aspergillus and Fusarium
spp. by measuring colony diameter on agar plates with the eugenol incorporated
was reported by Campaniello et al. (2010).
Bullerman (1974) reported that 1.0% cinnamon in raisin bread inhibited growth
and alfatoxin production by Aspergillus niger . The same group showed that the

￿ ￿ ￿ ￿ ￿