Functional Ingredients from Dairy Fermentations 369cially available and widely used in the indus-
try (Kerry, 2004e ).
MicroGARD^ ™^ is another product that is
produced by fermentation of whey, milk, or
whey - milk mixtures with Propionibacterum
species. It has been on the market for some
time. This product originally was sold in
liquid form, but now is available in powdered
form. The product has been widely used in the
industry to control Gram - negative spoilage
fl ora, yeasts, and molds in yogurt, cottage
cheese, and other foods. It originated from
research conducted at Oregon State Univer-
sity, which culminated in the issue of a patent
assigned to the state of Oregon (Ayers et al.
1992 ).
The major thrust of this discovery relates to
the unexpected activity of Propionibacte rium
fermentation liquids against Gram - negative
spoilage bacteria and food spoilage yeasts.
Although propionic acid is known to be antag-
onistic to molds at relatively low concentra-
tions, levels as high as 2% are needed to
inhibit yeasts. Such a high level of propionate
introduces undesirable fl avors and taints in
foods. In most Propoinibacterium fermenta-
tions the concentrations of propionic acid and
acetic acid range between 0.8% and 1.3% and
0.35% and 0.6%, respectively. The patent
describes various examples in different dairy
and food products in which the inhibition
exerted by Propionibactrium fermentation
liquids before and after drying could not be
attributed to propionate - acetate alone. Further
analyses of Propionibacterium fermentation
liquids showed that a proteinaceous product
with a molecular weight greater than 300, in
combination with the organic acid compo-
nents, is associated with such unexpected
inhibitory activity against spoilage - inducing
Gram - negative bacteria and yeasts.
MicroGARD^ ™^ is sold by Danisco Corpo-
ration. They market several products under
this label, including MG 100, MG 200, MG
300, MG 400, and MG CS 1 - 50. For further
details on these products, consult the relevant
trade literature (Danisco, 2005a ).culture house, Chr. Hansen Laboratories.
Other companies, including International
Flavors and Fragrances (IFF), also offer a
variety of such fl avor distillates and essences
for dairy and food applications.
Bio - preservatives
Over the past two decades, there has been
intense research interest in bacteriocins pro-
duced by lactic acid and related bacteria for
application as preservatives in foods. Another
area that has attracted equal interest has been
the use of acidic metabolic byproducts of
lactic acid fermentation for preservative
application in foods. The preservative effect
of lactic acid against Gram - negative spoilage
bacteria has been known for a long time.
Therefore, the inhibitory effect of acetic acid
against Pseudomonas and Bacillus species
and the suppressive activity of propionate
against molds and certain yeasts is common
knowledge.
Whey - based fermentation has been used
to produce an acetate - propionate mixture,
which is then dried to yield powders con-
taining high concentrations of the acids. In
this process, lactose in whey is converted
to lactic acid by fermenting with high -
temperature Lactobacillus species or a com-
bination of Streptococcus thermophilus and a
suitable Lactobacillus species (for example,
Lactobacillus delbrueckii or Lactobacillus
acidophilus ). The lactic acid liquor is subse-
quently fermented with selected strains of
Propionibacterium sp. At the end of the fer-
mentation, the entire fermentation liquid is
spray dried to obtain powders containing
acetate and propionate concentrations as high
as 16% acetate and 30% to 32% propionate.
These powders may be used to control Gram -
negative spoilage bacteria as well as molds
and certain yeasts in dairy products such as
cottage cheese, yogurt, sour cream, etc. The
powders also may be used in combination
with anti - caking agents to control molds in
shredded cheese. This product is commer-