Biopreservation of Meats and Meat Products - Food Biopreservation - page 28

1,000 IU/g, which showed a bactericidal effect against the pathogen. The inhibitory
effects were higher in samples stored at 10 °C compared to 4 °C. This could be a
draw-back for cold-stored meats, but at the same time could be an advantage under
episodes of cold chain break and temperature abuse. Regarding the effects of other
bacteriocins in minced meats, addition of a partially-purifi ed plantaricin preparation
from Lactobacillus plantarum UG1 rapidly reduced the population of L. monocyto-
genes below detectable levels in minced meat stored at 8 °C, (Enan et al. 2002 ), and
the addition of a freeze-dried whey fermentate from C. piscicola (containing pisci-
cocin CS526) to a ground mixture of beef and pork meat reduced the population of
L. monocytogenes below detectable levels for at least 4 days at 12 °C and for up to
25 days at 4 °C (Azuma et al. 2007 ). Furthermore, in minced pork treated with a
preparation of enterocins A and B (1,600 AU/g) from E. faecium CTC492, the levels
of listeria were reduced below 3 MNP/g after 6 days of incubation at 7 °C while the
untreated control increased from 5 MNP/g to 48 CFU/g (Aymerich et al. 2000 ).

4.1.2 Semi-processed and Cooked Meats

Cooked meat products are widely consumed ready-to-eat (RTE) foods. They may
consist of whole primary meat pieces, but usually they are made by grinding and
mixing secondary meats, fat, animal organs, or blood with other ingredients, fol-
lowed by stuffi ng/molding and cooking. The cooking process inactivates natural
microbiota, paving the way for growth of post-process contaminants. The pH values
of most cooked meat products are compatible with growth of pathogenic and spoil-
age bacteria, which can proliferate at refrigeration temperatures during the product
shelf life. Some of these meats may also undergo further processing such as slicing,
peeling, and packaging, which increase the risks for cross-contamination (Murphy
et al. 2005 ). For these reasons, there has been a great interest in the application of
bacteriocins (mainly pediocin and nisin) as hurdles against spoilage bacteria and
pathogens (mainly L. monocytogenes ). The main approaches tested are based on
addition of bacteriocin preparations to the meat slurries before the heating process,
surface application of the bacteriocins before packaging, or application of fi lms or
coatings dosed with bacteriocins. The possibility of adding bacteriocins in the meat
before the cooking process due to their thermotolerance is of great interest.
Strains of LAB (mainly Lactobacillus and Leuconostoc ) are the major group of
spoilage bacteria developing on various types of vacuum-packed meats, where they
produce typical sensory changes such as souring, gas, SH 2 and slime (Korkeala
et al. 1988 ; Björkroth and Korkeala 1997 ). In one study using sakacin K, nisin and
enterocins, the results obtained clearly depended on the bacteriocin and the target
bacteria (Aymerich et al. 2002 ). Sakacin K and nisin were unable to prevent ropi-
ness caused by Lactobacillus sakei CTC746 strain, but nisin was able to prevented
ropiness caused by Leuconostoc carnosum CTC747 (Aymerich et al. 2002 ). Nisin
was also the most effective bacteriocin on staphylococci, but did not prevent
regrowth of L. monocytogenes (while enterocins, sakacin and pediocin did).