Biomedical Engineering Reference
In-Depth Information
in cheese ripening (Lortal and Chapot-Chartier
2005
; Peláez and Requena
2005
;
Deegan et al.
2006
).
In one study,
L. lactis
DPC3286 (producing lactococcins A, B, and M) was tested
as an adjunct starter in cheddar cheese manufacture to induce lysis of a sensitive
acidifying starter strain (Morgan et al.
1997
) or in combination with a bacteriocin-
resistant starter. In experimental cheeses with the bacteriocin-resistant starter, the
levels of free amino acids increased together with a greater release of the intracel-
lular enzyme lactate dehydrogenase (LDH), and the cheeses showed lower bitter-
ness compared to controls (Morgan et al.
2002
). Because lactococcins A, B, and M
have a narrow spectrum of activity limited to lactococci, their producer strains could
be applied specifi cally for acceleration of cheese ripening (Ross et al.
1999
).
Another study reported that addition of the nisin Z-producing strain
L. lactis
ssp.
lactis
biovar
diacetylactis
UL719 during cheddar cheese making increased lipolysis
and proteolysis, as well as the formation of hydrophilic and hydrophobic peptides,
and enhanced the sensory characteristics of cheese (Benech et al.
2003
). Strain
UL719 was also tested for acceleration of autolysis of an adjunct
L. delbrueckii
subsp.
bulgaricus
strain, with the result of increasing cheese proteolysis and improv-
ing the cheese texture (Sallami et al.
2004
). An interesting observation was that
bacteriocin production by strain UL719 in cocultures with nisin-sensitive starters
Lactobacillus rhamnosus
RW-9595M and
L. lactis
subsp.
cremoris
was stimulated
by 3.1- to 4.6-fold. This stimulation was attributed to the high proteolytic activity of
L. cremoris
and to the release of intracellular nutrients due to autolysis and nisin
Z-induced lysis (Grattepanche et al.
2007
).
Production of lacticin 481 by
L. lactis
subsp.
lactis
strain DPC5552 induced
release of the intracellular enzymes LDH and postproline dipeptidyl aminopepti-
dase by starter strain
L. lactis
HP without completely inhibiting its growth
(O'Sullivan et al.
2002a
). Bacteriocin production also induced the release of ele-
vated levels of LDH from the starter without severely compromising its acid-
producing capabilities in a cheddar cheese-making trial. Further studies indicated
that lacticin 481 was also able to accelerate starter cell lysis (O'Sullivan et al.
2003
),
and that lacticin 481-producing cultures promoted early lysis of
Lactobacillus hel-
veticus
cells in Hispánico cheese and increased the proteolytic activity (Garde et al.
2006
). During the Hispánico cheese-making process, inoculation of milk with
strain
L. lactis
subsp.
lactis
INIA 415 (harboring the structural genes of lacticin 481
and nisin Z production) promoted early lysis of mesophilic and thermophilic starter
bacteria and increased extracellular aminopeptidase activity (Garde et al.
2002
).
It also lowered the ratio of hydrophobic-to-hydrophilic peptides, increased the free
amino acid content (Avila et al.
2006
), and enhanced the formation of several vola-
tile compounds of relevance to the odor and aroma of the cheese, such as hexanal,
2-methyl-1-propanol, 3-methyl-1-butanol, acetone, 2-pentanone, 2-hexanone, and
2-heptanone, but decreased the formation of acetaldehyde, ethanol, 3-methyl-3-
buten-1-ol, 3-methyl-2-buten-1-ol, ethyl acetate, ethyl butanoate, ethyl hexanoate,
2-butanone, 2,3-butanedione, 2,3-pentanedione, and 3-hydroxy-2-butanone (Garde
et al.
2005
).
