Biomedical Engineering Reference
In-Depth Information
(2-4 AU/ml) could also inactivate
G. stearothermophilus
vegetative cells in canned
corn and peas, and it increased the effi cacy of heat treatments on endospores
(Martínez Viedma et al.
2010a
). Enterocin EJ97 immobilized by coating in poly-
thene fi lms in combination with EDTA reduced the concentrations of viable
B.
coagulans
cells canned corn and peas stored at 4 °C (Martínez Viedma et al.
2010b
).
8.1.4
Fermented Vegetables and Beverages
Most vegetable fermentations are spontaneous (that is, no starter cultures being added)
and rely on the selective growth of the microbiota present in the raw materials as well
as microorganisms acquired during handluing a processing, coming from water,
equipments, and the processing environment. Addition of bacteriocins (such as nisin)
has been proposed as a way to direct the microbiota of vegetable fermentations
towards selection of desirable bacteriocin-tolerant or bacteriocin-resistant strains with
desirable effects (which in part may be due which due to their homofermentative or
heterofermentative traits) while at the same time inhibiting strains causing defects
such as overripening (as in the case of kimchi fermentation) or spoilage.
Addition of a nisin preparation to cabbage inoculated with nisin-resistant
Ln.
mesenteroides
improved control of the fermentation and delayed growth of the
homofermentative LAB (Breidt et al.
1995
). In kimchi, nisin was added to control
lactobacilli responsible for over-ripening of the product. Nisin addition showed
higher growth inhibition of
Lactobacillus
spp. than
Leuconostoc
spp. (Choi and
Park
2000
).
Ropiness of bread is mainly caused by
B. subtilis
, but
B. licheniformis
,
Bacillus
megaterium
and
B. cereus
may also be involved. Rope formation may occur in
wheat breads that have not been acidifi ed, or in breads with high concentrations of
sugar, fat, or fruits (Beuchat
1997
). The application of Nisaplin or nisin-producing
lactic acid bacteria in bread production was considered to be ineffective for inhibi-
tion of
B. subtilis
and
B. licheniformis
strains (Rosenquist and Hansen
1998
). The
fermented broth from a
Lactobacillus plantarum
strain producing bacteriocin-like
inhibitors was reported to inhibit rope formation by
B. subtilis
in yeast-leavened
bread (Valerio et al.
2008
). Other bakery products may combine a variety of ingre-
dients (as is the case of refrigerated pizza), making the control of microbial spoilage
more diffi cult. In ham pizza, application of Nisaplin under modifi ed atmosphere
packaging signifi cantly increased the product shelf life, due to inhibition of spoilage
lactic acid bacteria (Cabo et al.
2001
).
In fermented beverages, bacteriocin preparations can be applied against spoilage
LAB. In the beer production process, several applications have been proposed for
nisin (Ogden and Tubb
1985
; Ogden and Waites
1986
; Radler
1990
; Delves-
Broughton et al.
1996
; Jespersen and Jakobsen
1996
; Thomas et al.
2000
): (1)
cleaning of the equipment and fi nal cleansing rinse; (2) addition to fermenters to
control contamination; (3) increasing the shelf life of uncontaminated beers; (4)
reduction of pasteurization regimes, and (5) washing pitching yeasts to eliminate
