Biomedical Engineering Reference
In-Depth Information
listerial effects of fi lm packagings activated with enterocin 416K1 on fresh cheese
surfaces. In the fresh soft cheese samples packed in enterocin-activated fi lm, the
listeria counts were lower than controls by about 1 log unit up to 28 days for sam-
ples stored at 4 °C and for up to 7 days for samples stored at 22 °C. This approach
for application of bacteriocins not only reduces the levels of listeria on cheese sur-
faces but is also an effective barrier against cross-contamination of the cheeses.
Enterocin AS-48 has been suggested for biopreservation of prepared dishes and
desserts containing milk. In boiled rice and in a commercial rice-based infant for-
mula dissolved in whole milk inoculated with vegetative cells or with endospores of
B. cereus,
enterocin AS-48 (20-35
g/g) reduced viable cell counts below detect-
able levels during storage for up to 15 days in a temperature range of 6-37 °C and
prevented enterotoxin production (Grande et al.
2006a
). Bacteriocin activity was
improved by adding sodium lactate, decreasing the effective bacteriocin concentra-
tion to 8-16
ʼ
g/g). Although the bacterial endospores were resistant to this bacterio-
cin, application of AS-48 in combination with heat treatments decreased the thermal
death
D
values for endospores (Grande et al.
2006b
). In desserts and bakery ingre-
dients, the bactericidal effect of AS-48 on
S. aureus, B. cereus
and
L. monocyto-
genes
depended on the food substrate and the target bacteria (Martínez Viedma et al.
2009a
,
b
). The lowest and highest effi cacies were always detected in soy-based
desserts and in gelatin pudding, respectively.
L. monocytogenes
was completely
inactivated by bacteriocin concentrations in the range of 5-25
ʼ
ʼ
g/g, depending on
the substrate, and
B. cereus
was inactivated in a range of 15-50
g/g. Bacteriocin
addition to gelatin pudding prevented the production of proteases by
B. cereus
and
the consequent gelatin liquefaction. Inactivation of
S. aureus
required a higher bac-
teriocin concentration (50
ʼ
g/g) and also a lower population density of staphylo-
cocci, not higher than 5 log CFU/g. The bacteriocin also showed a variable degree
of activity against
S. aureus
in substrates like pumpkin confi ture, diluted almond
cream or liquid caramel, but was ineffective in vanilla or chocolate creams (Martínez
Viedma et al.
2009
). In chocolate cream, where higher bacteriocin concentrations
were required because of interaction of the bacteriocin with the food substrate, anti-
microbial activity increased markedly when AS-48 was tested in combination with
eugenol, 2-nitropropanol or Nisaplin.
Pediocin PA-1/AcH preparations are interesting for application in dairy products
due to the bacteriocin antilisterial activity, stability in aqueous solutions at ambient
temperature and also during freezing and heating, and wide pH range for activity
(Nes et al.
1996
; Rodríguez et al.
2002
). The commercial preparations containing
pediocin in the form of Alta™ products can be used as ingredients in dairy foods.
Several studies have shown that added pediocin PA-1/AcH is effective in reducing
the levels of
L. monocytogenes
in several types of dairy products such as dressed
Cottage cheese, half-and-half cream, and cheese sauce (reviewed by Rodríguez
et al.
2002
).
Other bacteriocins of interest in preservation of dairy foods are the propionicins.
Propionibacteria are used in some dairy fermentations and may produce bacterio-
cins with broad inhibitory spectra (Holo et al.
2002
). Microgard™ is a commercial
preparation containing an antimicrobial peptide produced by
Propionibacterium
ʼ
