Biomedical Engineering Reference
In-Depth Information
1998
) or strains of
L. lactis
ESI 153 and
L. lactis
ESI 515, isolated from hand-made
raw milk cheese and transformed into pediocin producers (Reviriego et al.
2005
).
The pediocin-producing transformants reduced viable counts of
L. monocytogenes
in cheese below 50 or 25 CFU/g at the end of the ripening period.
Bacteriocin-producing lactobacilli have also been suggested for preservation of
dairy foods.
Lactobacillus plantarum
WHE 92 is a spontaneous pediocin producer
that grows well and produces satisfactory pediocin concentrations in Munster
cheese (Ennahar et al.
1996
).
L. plantarum
LMG P-26358 isolated from a soft
French artisanal cheese produces plantaricin 423, which has strong anti-
Listeria
activity. This relatively narrow spectrum bacteriocin also exhibited antimicrobial
activity against species of enterococci, but did not inhibit dairy starters including
lactococci and lactobacilli. A strong listericidal effect was detected in cheeses made
with
L. plantarum
LMG P-26358 as an adjunct culture in combination with a nisin
producer, and the single inoculation with LMG P-26358 performed even better than
the single nisin producer. Combination of strain LMG P-26358 as adjunct culture
with nisin-producing cultures may be an effective strategy to improve the safety and
quality of dairy products (Mills et al.
2011
). Another interesting example is the
human isolate probiotic strain
Lactobacillus gasseri
K7, producer of bacteriocins
with wide range of inhibition (
et al.
2003
). Application of
bacteriocin-producing probiotic strains could be exploited with the purpose of
improving food safety and quality and at the same time providing health benefi ts.
Č
anžek Majheni
č
5.2.2
Inhibition of Bacteria Producing Gas-Blowing
Defects in Cheeses
Gas production is an undesirable defect in most cheeses, and may be caused by
outgrowth of
C. tyrobutyricum
(and other clostridia such as
Clostridium sporogenes,
Clostridium beijerinckii
or
Clostridium butyricum
) spores surviving heat treatments
applied to milk before processing (Cocolin et al.
2004
; Le Bourhis et al.
2007
), and
also by some heterofermentative LAB. Species of
Clostridium
can ferment lactic
acid with production of butyric acid, acetic acid, carbon dioxide and hydrogen.
Butyric acid fermentation (also known as late blowing defect) is one of the major
causes of spoilage in semi-hard and hard ripened cheeses. This fermentation
originates texture and fl avor defects in the cheeses, causing important economic
losses in the cheese industry (McSweeney and Fox
2004
). Bactofugation, milk
ultrafi ltration, and addition of nitrite or lysozyme are often applied to prevent butyric
acid fermentation in cheeses, but also the inoculation of milk with bacteriocino-
genic lactic acid bacteria (LAB) in cheese manufacture can provide satisfactory
results (Table
5.1
). Application of nisin-producing starter cultures to prevent gas-
blowing defects in cheese was proposed as early as 1951. Nisin-producing strains
have been used for developing a starter culture system for manufacture of Cheddar
cheese (Roberts et al.
1992
) and Gouda cheese (Bouksaim et al.
2000
), among oth-
ers. Strains producing the natural variant nisin Z have also shown to reduce the
