Biomedical Engineering Reference
In-Depth Information
foodstuffs to inhibit endospore outgrowth and also to increase the effi cacy of thermal
treatments against endospores. Incorporation of nisin in canned vegetables can pre-
vent spoilage caused by non-aciduric (
Bacillus stearothermophilus
and
Clostridium
thermosaccharolyticum
) as well as by aciduric (
Clostridium pasteurianum
,
Bacillus
macerans
,
Bacillus coagulans
) spore formers (Thomas et al.
2000
). Nisin has also
been reported to be an effective preservative in fresh pasteurized “home-made”-type
soups (Thomas et al.
2000
) and in the control of
Bacillus
and
Clostridium
in cooked
potato products (Thomas et al.
2002
). For example, in pasteurised, vacuum-packaged
mashed potatoes inoculated with a cocktail of
Clostridium sporogenes
and
Clostridium tyrobutyricum
spores, addition of nisin prevented bacterial growth and
extended the shelf life of the mashed potatoes by at least 30 days (Thomas et al.
2002
). Similar results were reported following nisin addition in trials involving a
cocktail of
B. cereus
and
Bacillus subtilis
strains (Thomas et al.
2002
). Nisin could
be applied singly or in combination with other bacteriocins, as shown in sous vide
mushrooms, in which addition of a nisin-pediocin mixture prevented outgrowth of
B. subtilis
spores (Cabo et al.
2009
).
In cooked vegetables (such as cooked potato products, sous-vide mushrooms,
“home-made”-type soups, purees, or cooked rice foods) and in canned vegetables
(such as canned tomato, peas, corn, etc.), addition of bacteriocins (such as nisin,
nisin-pediocin combination, or enterocin AS-48) has been proposed as a way to
inhibit endospore outgrowth and production of enterotoxins (such as
B. cereus
or
Clostridium botulinum
toxins) during storage and/or to increase the effi cacy of ther-
mal treatments against endospores (Thomas et al.
2000
; Galvez et al.
2008
; Cabo
et al.
2009
; Abriouel et al.
2010
). Incorporation of bacteriocins in canned vegetables
can be an effective hurdle to prevent spoilage caused by non-aciduric as well as by
aciduric spore formers.
In vegetable food products processed by heat such as purees and canned vegeta-
bles, enterocin AS-48 was tested against endospore-forming bacteria. In one study,
by adding AS-48 (10 mg/l),
B. cereus
LWL1 was completely inhibited in six vege-
table products (natural vegetable cream, asparagus cream, traditional soup,
homemade-style traditional soup, vegetable soup, and vichyssoise) for up to 30 days
in samples stored at 6, 15, and 22 °C. Other
Bacillus
and
Paenibacillus
species and
strains isolated from purées showed variable degrees of inactivation by enterocin
AS-48, requiring bacteriocin concentrations up to 50
g /ml (Grande et al.
2007b
).
Antimicrobial activity on a cocktail of bacilli increased considerably in combina-
tion with phenolic compounds (carvacrol, eugenol, geraniol, and hydrocinnamic
acid) (Grande et al.
2007b
). In canned foods such as tomato paste, syrup from
canned peaches, and juice from canned pineapple,
B. coagulans
(responsible for fl at
sour spoilage) was inhibited by added enterocin AS-48 (6 mg /l) for at least 15 days
of storage at 37 °C (Lucas et al.
2006
). Added bacteriocin also increased heat inac-
tivation of
B. coagulans
endospores.
In canned corn and peas, addition of enterocin AS-48 (7
ʼ
g/g) inactivated
G. stearothermophilus
cells for at least 30 days at a temperature of 45 °C simulating
tropical conditions (Martínez Viedma et al.
2010a
). Remarkably, AS-48 strongly
adsorbed to bacterial endospores, inhibiting endospore outgrowth. Enterocin EJ97
ʼ
