Agriculture Reference
In-Depth Information
(Shima et al. 1984). The safety of ε -poly- L -lysine as a food additive has been
demonstrated by trials with rats (Hiraki 1995, 2000; Neda et al. 1999). No toxic
effects were detected in reproduction, neurological and immunological functions,
embryonic and foetal development, growth of offspring and development of
embryos for two generations.
ε -Poly- L -lysine is an approved food preservative in Japan (Hiraki 2000).
Common usage includes spraying or dipping sliced fi sh or fi sh sushi at levels of 1-5
g/l and the preservation of boiled rice, noodles, cooked vegetables and soups at
levels of 10-500 mg/kg (Hiraki 2000; Otsuka et al. 1992). ε -Poly- L -lysine has also
been used in potato salad, steamed cakes and custard cream (Hiraki et al. 2003). It
was given GRAS status by the US Food and Drug Administration (FDA) in 2004
(FDA 2004) when it approved use in cooked or sushi rice at levels up to 50 mg/kg.
6.2.7 Protective cultures
Use of protective cultures to preserve fermented foods such as yoghurt, cheeses,
sour cream and fermented sausages is attracting considerable attention as a novel
natural means of food preservation, as their use is extremely label friendly.
Protective cultures are typically lactic acid bacteria and must fulfi l the following
properties to be effective:
ability to grow in the food;
ability to inhibit/limit growth of the spoilage fl ora;
not create unwanted changes to the product;
not to produce substances which may be harmful to humans.
Protective cultures have been described that are effective against yeast and mould
spoilage. They can either consist of a single strain or a mixture of strains belonging
to the same or different genera. Suomalainen and Mäyrä-Mäkinen (1999) and
Schwenninger and Meile (2004) describe the development of protective cultures
consisting of a mixture of lactic acid bacteria and propionic acid bacteria. In both
cases the lactic acid bacteria showed only weak inhibitory action when used alone
whereas in combination revealed high antagonistic properties against yeasts and
moulds in dairy products. Although the exact mode of action is not identifi ed it is
recognised that lactic acid bacteria can produce compounds with anti-yeast
activity such as proteins, phenylacetic acid and cyclic peptides and hydoxylated
acids. Bacteriocin-like substances and other compounds of low and medium
molecular weight have been reported as having activity against yeasts. Furthermore
yeasts can also be sensitive to organic acids such as lactic and acetic acid produced
by lactic acid bacteria.
Use of Pediococcus acidilactici as protective cultures inhibiting L.
monocytogenes has been demonstrated in various meats such as fermented
sausages and vacuum-packaged products as well as in vegetable type foods
(Holzapfel et al. 2003). As well as production of the bacteriocin, pediocin and the
other inhibitory substances mentioned above, competitive exclusion and quorum
sensing may play signifi cant roles.
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