Biomedical Engineering Reference
In-Depth Information
5.1.2
Processed Milk Products
Nisin is widely used in the dairy industry for inhibition of gas blowing defect in
cheeses caused by
Clostridium tyrobutyricum
, but also in processed cheeses and
cheese products to inhibit
Clostridium botulinum
, and to prevent growth of post-
process contaminating bacteria such as
L. monocytogenes
(Davies and Delves-
Broughton
1999
; Thomas et al.
2000
; Thomas and Delves-Broughton
2001
; Deegan
et al.
2006
; Sobrino-López and Martín-Belloso
2008
) (Table
5.1
). It is also used in
many other pasteurised dairy products, such as chilled desserts, fl avoured milk,
clotted cream, or canned evaporated milks (Thomas et al.
2000
). For example, the
addition of nisin powder to milk in the production of cheese made without a starter
culture can control microbial contamination (Sobrino-López and Martín-Belloso
2008
). Addition of nisin at 100 or 500 mg/kg suppressed total plate and anaerobic
spore counts in processed cheese during 3 months of storage at 5 or 21 °C, and even
the growth of
G. stearothermophilus
,
B. cereus
and
Bacillus subtilis
were inhibited
by 5 mg/kg nisin (Plockova et al.
1996
). In Ricotta-type cheese, addition of nisin
(2.5 mg/l) inhibited the growth of
L. monocytogenes
for more than 8 weeks, while
cheese made without nisin contained unsafe levels of the bacteria within 1-2 weeks.
In addition, there was a high level of retention of nisin activity in the cheese after 10
weeks of incubation at 6-8 °C, with only 10-32 % loss of antibacterial activity
(Davies et al.
1997
).
Nisin addition in combination with HHP could be useful for inactivation of endo-
spores and mesophilic bacteria in cheese (Capellas et al.
2000
; López-Pedemonte
et al.
2003
; Arqués et al.
2005a
). For example, the combination of nisin with HHP
strongly reduced the counts of
B. cereus
spores in a traditional cheese curd. Since
bacterial endospores are pressure-resistant, two HHP cycles were applied, the fi rst
one to induce endospore germination and the second one to destroy the vegetative
cells (López-Pedemonte et al.
2003
). The authors of this study concluded that the
combined treatment could improve the microbial stability and safety of cheeses,
especially those made from unpasteurised milk, such as many traditional cheeses,
decreasing the restrictions that are currently imposed on the commercialisation of
such cheeses.
Due to its non-specifi c inhibitory activity against Gram-positive bacteria, nisin
may interfere with growth of starter cultures cheese fermentation and have detri-
mental effects on acidifi cation and/or aroma formation. In order to solve this limita-
tion and also to enhance nisin stability, nisin Z was encapsulated in liposomes
(Benech et al.
2002a
,
b
). Addition of liposome preparations was shown to inhibit
listeria in Cheddar cheese (Benech et al.
2002a
,
b
). In another study, nisin encapsu-
lated in soybean phosphatidylcholine nanovesicles provided best results compared
to added free nisin in the control of
L.monocytogenes
in Minas frescal cheese stored
at 7 °C, keeping the concentrations of listeriae lower than the untreated controls for
at least 21 days (Malheiros et al.
2012
). Some growth inhibition was also obtained
with an encapsulated BLIS P34 (derived from
Bacillus
sp. P34) in parallel experiments.
