Functional Ingredients from Dairy Fermentations 371In 1959 nisin was permitted as a pre-
servative in the United Kingdom. Initially,
it was used to prevent clostridia - induced
blowing of high moisture cheese. Also in
1959, nisin was accepted as a food addi-
tive by the Joint Food and Agriculture
Organization and World Health Organization
of United Nations. It is currently accepted
as a legal food additive worldwide. Applica-
tion studies in the use of nisin as a preserva-
tive in various dairy foods have been reported
in the literature. Vandenberg (1993) has pro-
vided a concise summary of the use of nisin
in dairy foods and its regulatory status in
various countries.
Nisin is currently marketed under the
trade name Nisaplin ® by Danisco for applica-
tion in dairy foods. For more information, see
the trade bulletin by Danisco (2005c).Bioactive Peptides and Nutraceuticals
The term functional foods has gained wide-
spread currency in food scientifi c literature.
Functional foods contain health - promoting
components beyond traditional nutrients,
referred to as nutraceuticals. Among the
nutraceuticals, bioactive peptides have gar-
nered great interest in therapeutic and pre-
ventive nutrition.
Casein and whey proteins are rich in bio-
active peptides. These peptides are physio-
logically inactive in the native milk proteins,
but bioactive peptides are released when the
proteins are hydrolyzed. These peptides
display biological activity ranging from anti-
hypertensive effects to immunostimulation
and opioid agonistic effects. Casokinins, β -
lactorphins, α - lactorphins, and lactkinins are
bioactive peptides from casein and whey pro-
teins that exhibit inhibitory activity against
angiotension - I and - II - converting enzymes,
which are involved in causing hypertension.
The angiotension - I - converting enzyme is
referred to as ACE, and the bioactive pep-
tides counteracting the activity of ACE are
called ACE inhibitors.Lactococcus lactis subsp. lactis strains. The
active protein with a mass of 3,500 Da exists
in multimeric form. This bacteriocin is ribo-
somally synthesized as a prepeptide (57
amino acid peptide) and posttranslationally
processed into a mature peptide (34 amino
acid peptide). The genetic determinants for
nisin production are encoded on a transposon
called Tn5301. Nisin contains three unusual
amino acids: dehydroalanine, lanthionine,
and β - methyl lanthionine; thus, nisin is called
a lantibiotic.
Genes associated with nisin synthesis
are nisA, nisB, nisT, and nisC. nisA is the
structural gene for the prepeptide,; nisB
codes for a membrane - associated protein,
nisT is considered to be involved in the
transport of nisin, and nisB has been found
to bear homology to proteins involved in
the biosynthesis of a closely related bacterio-
cin called subtilin (also a lantibiotic) pro-
duced by certain strains of Bacillus subtilis
(Vandenbergh, 1993 ).
Nisin interacts with cytoplasmic mem-
branes of susceptible bacteria and forms
potential dependent pores that cause the
destruction of proton - motive force, thus per-
mitting the effl ux of ions, small molecules,
and cytoplasmic components. Although the
binding of nisin to the cell walls of sensitive
cells is known, the exact mechanism by
which it destabilizes the cytoplasmic mem-
branes is not yet understood (Vandenbergh,
1993 ).
As mentioned earlier, nisin has a broad
inhibitory spectrum. It is active against
species belonging to the following genera:
Lactococcus, Streptococcus, Micrococcus ,
Staphylococcus, Pediococcus, Lactobacillus,
Listeria, Mycobacterium, and Bacillus,
including their spores, and Clostridium and
their spores. It is inactive against Gram -
negative bacteria, but in the presence of che-
lating agents such as EDTA, nisin has been
shown to be active against Salmonella,
Escherichia coli, Pseudomonas aeruginosa,
and certain other Gram - negative species.