Microbiology of Fermented Food Production ◾ 187
Starters (Controlled or Natural Fermentation)
In controlled fermentation, frozen or dried concentrates are used directly in a 10 6–7 cells/g mix.
Starters should not be mixed with salt, cure, or spices as they can kill injured cells. Instead,
they should be thawed and immediately put into the meat. Starters vary, depending on the fermentation temperature and final pH of the product desired. For high temperature and low pH,
Pediococcus acidilactici strains are preferred; for low temperature and high pH, Lab. plantarum
strains are preferred. Ped. pentosaceus strains can be used under both conditions. Some starters
can have both Pediococcus and Lactobacillus species. In addition, selected Micrococcus spp. or Sta.
carnosus strains are added as secondary flora for their beneficial effects on desired product color.
In naturally fermented sausages, Lab. sake, Lab. curvatus, and Leuconostoc spp. present in raw
materials are important starter bacteria, especially when fermentation is set at lower temperatures
(60°F–70°F [15.6°C–21.1°C]) for several days and the final pH reached is not below 5.0.
Growth
Because the raw meat used may contain pathogens and spoilage bacteria, it is extremely important
that starter culture grows rapidly and produces acid in large amounts to reduce pH from the initial
5.7 to approximately 5.3 very quickly to retard their growth. This can be achieved by adding large
numbers of active starter cells, adding dextrose to the mix, and setting the temperature of fermentation optimum for the starters used. The optimum growth temperatures for Ped. acidilactici,
Ped. pentosaceus, and Lab. plantarum are approximately 40°C, 35°C, and 30°C (104°F, 95°F, and
86°F), respectively. Micrococcus spp. and Sta. carnosus grow well at approximately 32.2°C (90°F).
Cooking to an internal temperature of 60°C (140°F) kills Lab. plantarum and probably Ped. pentosaceus but probably not Ped. acidilactici, Micrococcus, or Sta. carnosus. However, low pH and low
A W prevent their growth in the finished products.
Biochemistry
Both pediococci are homolactic fermentors and metabolize glucose to mainly lactic acid (DL
forms) with small amounts of acetate and diacetyl. Lab. plantarum, being facultatively heterofermentative, metabolizes glucose to principally lactic acid (DL); however, it can also produce substantial amounts of acetate, ethanol, and diacetyl. Strains of all three species can produce H 2 O 2 ,
which can discolor the product by oxidizing myoglobin during fermentation. Micrococcus spp.
or Sta. carnosus have catalase that can destroy H 2 O 2 . Micrococcus spp. or Sta. carnosus and some
strains of Lab. plantarum can also reduce nitrate to nitrite. If nitrate is used in place of nitrite in
cure, these bacteria can produce nitrite and help develop the agreeable pinkish color of the product. If the products are cured or stored for long periods of time, some of the intracellular enzymes
of the lysed cells of starters are able to cause proteolysis and lipolysis and produce biologically
active amines (such as histamine).
Genetics
Rapid acid-producing lactic acid bacterial strains at temperatures of fermentation and non-H 2 O 2
producers are desired. Strain selection can also be done for nonproducers of biogenic amines.
Strains producing bacteriocins can be used to control pathogens and spoilage bacteria. Ped. acidilactici strains that cannot hydrolyze sucrose (Suc – ) can be used to produce sweet and sour products
Starters (Controlled or Natural Fermentation)
In controlled fermentation, frozen or dried concentrates are used directly in a 10 6–7 cells/g mix.
Starters should not be mixed with salt, cure, or spices as they can kill injured cells. Instead,
they should be thawed and immediately put into the meat. Starters vary, depending on the fermentation temperature and final pH of the product desired. For high temperature and low pH,
Pediococcus acidilactici strains are preferred; for low temperature and high pH, Lab. plantarum
strains are preferred. Ped. pentosaceus strains can be used under both conditions. Some starters
can have both Pediococcus and Lactobacillus species. In addition, selected Micrococcus spp. or Sta.
carnosus strains are added as secondary flora for their beneficial effects on desired product color.
In naturally fermented sausages, Lab. sake, Lab. curvatus, and Leuconostoc spp. present in raw
materials are important starter bacteria, especially when fermentation is set at lower temperatures
(60°F–70°F [15.6°C–21.1°C]) for several days and the final pH reached is not below 5.0.
Growth
Because the raw meat used may contain pathogens and spoilage bacteria, it is extremely important
that starter culture grows rapidly and produces acid in large amounts to reduce pH from the initial
5.7 to approximately 5.3 very quickly to retard their growth. This can be achieved by adding large
numbers of active starter cells, adding dextrose to the mix, and setting the temperature of fermentation optimum for the starters used. The optimum growth temperatures for Ped. acidilactici,
Ped. pentosaceus, and Lab. plantarum are approximately 40°C, 35°C, and 30°C (104°F, 95°F, and
86°F), respectively. Micrococcus spp. and Sta. carnosus grow well at approximately 32.2°C (90°F).
Cooking to an internal temperature of 60°C (140°F) kills Lab. plantarum and probably Ped. pentosaceus but probably not Ped. acidilactici, Micrococcus, or Sta. carnosus. However, low pH and low
A W prevent their growth in the finished products.
Biochemistry
Both pediococci are homolactic fermentors and metabolize glucose to mainly lactic acid (DL
forms) with small amounts of acetate and diacetyl. Lab. plantarum, being facultatively heterofermentative, metabolizes glucose to principally lactic acid (DL); however, it can also produce substantial amounts of acetate, ethanol, and diacetyl. Strains of all three species can produce H 2 O 2 ,
which can discolor the product by oxidizing myoglobin during fermentation. Micrococcus spp.
or Sta. carnosus have catalase that can destroy H 2 O 2 . Micrococcus spp. or Sta. carnosus and some
strains of Lab. plantarum can also reduce nitrate to nitrite. If nitrate is used in place of nitrite in
cure, these bacteria can produce nitrite and help develop the agreeable pinkish color of the product. If the products are cured or stored for long periods of time, some of the intracellular enzymes
of the lysed cells of starters are able to cause proteolysis and lipolysis and produce biologically
active amines (such as histamine).
Genetics
Rapid acid-producing lactic acid bacterial strains at temperatures of fermentation and non-H 2 O 2
producers are desired. Strain selection can also be done for nonproducers of biogenic amines.
Strains producing bacteriocins can be used to control pathogens and spoilage bacteria. Ped. acidilactici strains that cannot hydrolyze sucrose (Suc – ) can be used to produce sweet and sour products