160 ◾ Fundamental Food Microbiology
History
Initial development of starter cultures resulted from the needs of and changes in the cheese industry. Before the 1950s, small producers were producing limited amounts of cheese to satisfy local
consumers. A plant used to maintain a bottle of mother culture by daily transfer, which it received
from a culture producer or another neighboring processor. From the mother culture, the plant used
to make bulk culture through several transfers to meet the inoculation volume (to meet the need of
1%–2% of the volume of milk to be processed for cheese). These starters were a mixture of undefined
strains of bacteria, and it was difficult to produce a product of consistent quality. There were also
problems with starter failure from bacteriophage attack. To overcome the problem of quality, the
single-strain starter (a desired strain isolated from a mixture) was introduced. Good sanitation and
newly designed processing equipment were introduced to overcome phage problems. 1
Since the 1950s, large cheese operations have replaced the small producers. They needed products of consistent quality and could not afford to have too many starter failures from phage attack.
Starter-culture producers developed single-strain cultures and supplied these in dried form to the
cheese processors, who, in turn, used them to produce mother cultures and bulk cultures. To overcome phage problems, rotation of strains (such as using different strains each day) to prevent the
buildup of a particular phage as well as multiple-strain cultures (if one strain is killed by a specific
phage, another will work) were practiced. Later, defined media to produce bulk cultures that reduced
phage attack were introduced. Even then, daily production of large amounts of bulk cultures (some
cheese processors were handling more than 1,000,000 gal of milk daily and needed more than
10,000 gal of bulk cultures) and maintaining a large number of defined bacterial strains for use in
rotation or multiple-strain cultures (some were keeping 30 or more strains) and using them in proper
combinations (so that they are compatible) demanded defined and large facilities, expert microbiologists, and a large crew for the operation. This was partially overcome with the introduction in the
1960s of frozen concentrate cultures that could be shipped by air from culture producers to cheese
processors in dry ice and could be used directly to produce bulk cultures. This, along with the availability of several types of phage inhibitory media (PIM) to produce bulk cultures, helped cheese
processors overcome the cost and labor necessary to maintain a microbiological laboratory and a
large number of starter strains. These dairy-based media contain a high concentration of phosphate
to chelate calcium in milk and thus make the divalent cation unavailable for the adsorption of phages
to the bacterial cells and cause infection. To obtain high cell density by maintaining a high pH, the
media had either internal or external pH control systems. Subsequently, frozen concentrated cultures, containing 10 11–12 cells/mL were introduced; they could be directly inoculated into milk in the
cheese vat (direct vat set, DVS), eliminating the need to produce bulk starter by a cheese processor.
From the 1970s, the popularity of several types of fermented dairy products (particularly
buttermilk and yogurt), as well as fermented sausages, some fermented ethnic products, and fermented health products, stimulated their production by large commercial processors. To meet
their need, different types of frozen concentrated cultures for direct inoculation into the raw
materials were developed.
Efforts have been made to produce freeze-dried or spray-dried concentrated cultures. 2 Dried
cultures can eliminate the bulk problem in transporting frozen concentrated cultures in dry ice as
well as their accidental thawing, which would thus prevent their use. Dried cultures can also be used
directly for product manufacture or can be used to produce bulk starters. However, many strains do
not survive well in the dried state. Thus, their use as dried cultures in large commercial operations
has been limited. They are available in small packages for use directly by the small processors of fermented foods or for use to produce bulk cultures before inoculation in the raw material.
History
Initial development of starter cultures resulted from the needs of and changes in the cheese industry. Before the 1950s, small producers were producing limited amounts of cheese to satisfy local
consumers. A plant used to maintain a bottle of mother culture by daily transfer, which it received
from a culture producer or another neighboring processor. From the mother culture, the plant used
to make bulk culture through several transfers to meet the inoculation volume (to meet the need of
1%–2% of the volume of milk to be processed for cheese). These starters were a mixture of undefined
strains of bacteria, and it was difficult to produce a product of consistent quality. There were also
problems with starter failure from bacteriophage attack. To overcome the problem of quality, the
single-strain starter (a desired strain isolated from a mixture) was introduced. Good sanitation and
newly designed processing equipment were introduced to overcome phage problems. 1
Since the 1950s, large cheese operations have replaced the small producers. They needed products of consistent quality and could not afford to have too many starter failures from phage attack.
Starter-culture producers developed single-strain cultures and supplied these in dried form to the
cheese processors, who, in turn, used them to produce mother cultures and bulk cultures. To overcome phage problems, rotation of strains (such as using different strains each day) to prevent the
buildup of a particular phage as well as multiple-strain cultures (if one strain is killed by a specific
phage, another will work) were practiced. Later, defined media to produce bulk cultures that reduced
phage attack were introduced. Even then, daily production of large amounts of bulk cultures (some
cheese processors were handling more than 1,000,000 gal of milk daily and needed more than
10,000 gal of bulk cultures) and maintaining a large number of defined bacterial strains for use in
rotation or multiple-strain cultures (some were keeping 30 or more strains) and using them in proper
combinations (so that they are compatible) demanded defined and large facilities, expert microbiologists, and a large crew for the operation. This was partially overcome with the introduction in the
1960s of frozen concentrate cultures that could be shipped by air from culture producers to cheese
processors in dry ice and could be used directly to produce bulk cultures. This, along with the availability of several types of phage inhibitory media (PIM) to produce bulk cultures, helped cheese
processors overcome the cost and labor necessary to maintain a microbiological laboratory and a
large number of starter strains. These dairy-based media contain a high concentration of phosphate
to chelate calcium in milk and thus make the divalent cation unavailable for the adsorption of phages
to the bacterial cells and cause infection. To obtain high cell density by maintaining a high pH, the
media had either internal or external pH control systems. Subsequently, frozen concentrated cultures, containing 10 11–12 cells/mL were introduced; they could be directly inoculated into milk in the
cheese vat (direct vat set, DVS), eliminating the need to produce bulk starter by a cheese processor.
From the 1970s, the popularity of several types of fermented dairy products (particularly
buttermilk and yogurt), as well as fermented sausages, some fermented ethnic products, and fermented health products, stimulated their production by large commercial processors. To meet
their need, different types of frozen concentrated cultures for direct inoculation into the raw
materials were developed.
Efforts have been made to produce freeze-dried or spray-dried concentrated cultures. 2 Dried
cultures can eliminate the bulk problem in transporting frozen concentrated cultures in dry ice as
well as their accidental thawing, which would thus prevent their use. Dried cultures can also be used
directly for product manufacture or can be used to produce bulk starters. However, many strains do
not survive well in the dried state. Thus, their use as dried cultures in large commercial operations
has been limited. They are available in small packages for use directly by the small processors of fermented foods or for use to produce bulk cultures before inoculation in the raw material.