Handbook of Meat Processing

270 Chapter 14

acidilactici. Another approach for biopreser-

vation might be use of lactic acid - producing

bacteria that also produce bacteriocins as

direct protective cultures on meats (Hugas

1998 ) due to the fact that lactic acid bacteria

do not induce signifi cant spoilage until large

population numbers are reached (Nychas et

al. 2007 ). Bloukas et al. (1997) extended

shelf life of vacuum - packaged frankfurters

stored at 4 ° C by one week using com-

mercially available protective culture of

Lactobacillus alimentarius.

Government approval is needed in order

to take advantage of the variety of bacterio-

cins present in nature. To date, nisin is the

only approved bacteriocin. Nisin can be used

to control Gram - positive bacteria, such as the

pathogen L. monocytogenes and the spoiler

B. thermosphacta. Although methods of sen-

sitizing Gram - negatives are well known, the

major drawback of nisin is its loss of activity

in meat products, such that large concentra-

tions are needed. This increases application

costs.

Lactic Acid, Sodium Lactate,

Diacetate, and Acetate

The U.S. government allows the use of lactic

acid, sodium lactate (4.8%), sodium diacetate

(0.25%), and sodium acetate (0.25%) on

meat products as extensive research has

shown their safety for human consumption

(FDA 2000 ). Whether produced by lactic

acid bacteria or chemically derived, the listed

compounds are antagonists to food - borne

pathogens and to general spoilage microfl ora

of the foodborne pathogen L. monocytogenes
(Scannell et al. 1997 ; Murray and Richards
1998 ; Pawar et al. 2000 ). In addition, nisin is
currently used in the United States as an anti-
botulinum agent for pasteurized cheese prod-
ucts and pasteurized liquid eggs.
A drawback of bacteriocin usage is that
effectiveness is only against closely related
bacteria, which usually excludes Gram -
negative bacteria. For example, nisin was
effective against L. monocytogenes on cooked
pork under MAP, but not against Pseudomonas
fragi (Fang and Lin 1994 ). In order to sensi-
tize Gram - negatives to nisin, chelators or
bacterial membrane disruptors, such as
EDTA, Tween - 80, or high hydrostatic pres-
sure (HHP), might be required (Natrajan and
Sheldon 2000b ; Galvez et al. 2007 ).
Application of nisin in meat products is
somewhat challenging due to its binding
ability to meat components, low solubility
(hydrophobic nature), and loss of effi cacy at
pH > 5 (Scannell et al. 1997 ; Murray and
Richards 1998 ). For example, Rose et al.
(1999) showed that glutathione, which is
present in raw ground beef, can inactivate
nisin. Scott and Taylor (1981) showed the
need for greater nisin concentration to inac-
tivate Clostridium botulinum in cooked
meat compared to microbiological medium.
Finally, Chung et al. (1989) showed a 70%
loss in nisin activity in raw meat during
storage at 5 ° C for 4 days.
Hugas (1998) mentioned that pediocin
might be more effective than nisin in meat
applications, since it is derived from the
meat - fermentation bacterium Pediococcus

Table 14.4. Summary of bacteriocins and their producing bacteria

Bacteriocin Producer Bacteriocin Producer

Nisin, lacticin Lactococcus lactis Sakacin Lactobacillus sakei

Lactocin Lactobacillus sakei Curvacin Lactobacillus curvatus

Pediocin Pediococcus acidilactici Curvacitin Leuconostoc curvatus

Enterocin Enterococcus faecium Bavaricin Lactobacillus bavaricus

Brevicin Lactobacillus brevis Leucocin Leuconostoc gelidum

Divergicin Carnobacterium divergens Carnobacteriocin/Piscicolin Carnobacterium piscicola

Adapted from Hugas 1998