Dairy Ingredients for Food Processing

Microbiological Aspects of Dairy Ingredients 71

Conventional Buttermilk

Conventional buttermilk is a by - product of

butter making. Depending on the processing

conditions, which may involve heating the

cream before ripening at 90 ° C to 95 ° C for 15

seconds or 105 ° C – 110 ° C with no holding,

sour cream or sweet cream buttermilk may

be produced. Sweet cream buttermilk can be

further fermented by mesophillic lactic acid

bacteria.

Cultured Buttermilk

Cultured buttermilk is made from skim milk

that is heated to 95 ° C for 5 minutes and

cooled to 22 ° C. It is then inoculated with a

mixture of Lactococcus spp. ( Lc. lactis subsp.

lactis and Lc. lactis subsp. cremoris ), which

are the main acid producers, and Lc. lactis

subsp. lactis biovar diacetylactis and Leu.

mesenteriodes, the latter of which is respon-

sible for aroma and fl avor production. The

milk may be enriched with sodium citrate

(0.1% to 0.15%). This aids production of

diacetyl as well as other fl avor compounds

such as acetoin and ethanol because the level

of intrinsic citrate in milk varies, and during

the summer is closely correlated with micro-

biological quality, particularly the number of

Enterobacter spp. and Pseudomonas spp.

Some strains of Leu. mesenteroides can

produce exopolysaccharides, which enhance

the functional properties of buttermilk and

bacteriocins that are active against Listeria

spp. After fermentation (14 to 16 hours at

22 ° C) the product is warmed to 40 ° C, homog-

enized, cooled, and packaged.

Food poisoning cases implicating butter-

milk are rare and usually occur when it is

used as an ingredient to make a product such

as mayonnaise, which requires raw egg that

may be contaminated with Salmonella spp.

Spoilage usually manifests as loss of

texture arising from excessive agitation,

improper cooling, or use of unsuitable pumps.

In some instances disruption of the gel can

occur through the production of carbon

of butter fat through lipolysis. Putridity
and surface taints result from the proteo-
lytic activities of molds and bacteria grow-
ing on the butter surface, for example, Ps.
putrefaciens. Surface growth may become
apparent within 7 to 10 days with a
concomitant odor resulting from organic
acids. Bacteria may also cause other less
common spoilage conditions in butter: malty
fl avor due to Lc. lactis var. maltigenes ,
skunk - like odor due to Ps. mephitica , and
black discoloration due to Penicillium nigri-
faciens (Jay, 2000 ). Some members of the
genera Cladosporium, Aspergillus, Penicil-
lium , and Mucor may be responsible for
discoloration on the surface of butter,
although with improved sanitation and air
fi ltering in many dairy plants, this is not a
major issue.

Buttermilk

Buttermilk has two main variants: conven-
tional buttermilk, which is an aqueous phase
harvested as a consequence of churning
cream during normal butter making, or cul-
tured buttermilk, which is the result of the
fermentation of skim or low - fat milk using
lactic co - cultures.
According to the International Dairy
Federation Standard 163 : 1992, the require-
ments for buttermilk are acidity of not less
than 0.60% (w/w) expressed as lactic acid,
fermented by Lc. lactis or its subspecies and
biovariants and/or Leuconostoc mesenteroi-
des and its subspecies. Minimum counts of
specifi c microorganisms should be 10^7 cfu/g
at the time of sale. Normally buttermilk is
either used directly as a refreshing drink or
by the food industry as an ingredient in bread,
biscuits, cakes, ice cream, or processed
cheese products. The high level of membrane -
specifi c proteins and phospholipids give but-
termilk its unique characteristics. Buttermilk
can be tolerated by lactase defi cient individu-
als who are unable to consume milk or ice
cream.