Microbiology of Fermented Food Production ◾ 189
traditional fermented vegetable products from South Korea. Most are produced by natural fermentation; however, some, such as cucumbers, are currently produced in limited amounts by controlled
fermentation. Production of sauerkraut by natural fermentation is described here as an example.
Microbiology of Sauerkraut 3
Characteristics
Sauerkraut is produced by fermenting shredded cabbage. The product has a sour taste with a clean
acid flavor.
Processing
1. Cabbage cleaned, trimmed, and shredded finely and uniformly.
2. Packaged tight to exclude air in vat and layered with salt (2.25%).
3. Top covered to exclude air, fermented at 18°C (65°F) for 2 months.
Fine shredding helps the sugars (3%–6%) come out of the cabbage cells. Tight packaging helps create an anaerobic condition, thus preventing the growth of aerobes. Salt stimulates growth of some
lactic acid bacteria and discourages the growth of some undesirable bacteria and pectinase (in cabbage) action. The top is covered to exclude air and prevent growth of some aerobes. Fermentation
at 18°C (65°F) discourages the rapid growth of some undesirable bacteria (facultative anaerobic or
anaerobic), but it encourages the growth of desirable lactic acid bacteria. Natural inhibitors in cabbage also discourage the growth of undesirable Gram-negative and Gram-positive bacteria.
Starters (Natural) and Growth
The raw material has a large number of undesirable organisms and a small population of lactic acid
bacteria (<1%). Among the lactic acid bacteria, most are Lactococcus spp. and Leuconostoc spp., and
a small fraction is Lactobacillus spp. and Pediococcus spp. During fermentation, sequential growth
of these lactic acid bacteria occurs. The presence of 2.25% salt, large amounts of fermentable sugars (sucrose, hexoses, pentoses), an absence of oxygen, and a low fermentation temperature facilitate Leuconostoc spp., primarily Leu. mesenteroides, to grow rapidly. When the acidity has reached
approximately 1% (as lactic acid), growth of Leu. mesenteroides slows down. Then Lab. brevis starts
growing rapidly until acid production reaches approximately 1.5%. Then Ped. pentosaceus takes
over and increases the acidity to approximately 1.8%. Finally, Lab. plantarum starts growing and
brings the acid level to approximately 2%.
Biochemistry
Leuconostoc spp. metabolize sucrose, hexoses, and some pentoses in the raw material to lactate,
acetate, ethanol, CO 2 , and diacetyl. Lab. brevis (obligatory heterofermentative, such as Leuconostoc
spp.) ferments sucrose, hexoses, and pentoses to products similar to those by Leuconostoc spp.
Ped. pentosaceus metabolizes hexoses to form mainly lactic acid and some pentoses to lactic acid,
acetate, and ethanol. Lab. plantarum also produces products from sucrose, hexoses, and pentoses
similar to those by Ped. pentosaceus. Leuconostoc spp. produces d(–)-lactate, whereas the other three
species produce dl-lactate.
traditional fermented vegetable products from South Korea. Most are produced by natural fermentation; however, some, such as cucumbers, are currently produced in limited amounts by controlled
fermentation. Production of sauerkraut by natural fermentation is described here as an example.
Microbiology of Sauerkraut 3
Characteristics
Sauerkraut is produced by fermenting shredded cabbage. The product has a sour taste with a clean
acid flavor.
Processing
1. Cabbage cleaned, trimmed, and shredded finely and uniformly.
2. Packaged tight to exclude air in vat and layered with salt (2.25%).
3. Top covered to exclude air, fermented at 18°C (65°F) for 2 months.
Fine shredding helps the sugars (3%–6%) come out of the cabbage cells. Tight packaging helps create an anaerobic condition, thus preventing the growth of aerobes. Salt stimulates growth of some
lactic acid bacteria and discourages the growth of some undesirable bacteria and pectinase (in cabbage) action. The top is covered to exclude air and prevent growth of some aerobes. Fermentation
at 18°C (65°F) discourages the rapid growth of some undesirable bacteria (facultative anaerobic or
anaerobic), but it encourages the growth of desirable lactic acid bacteria. Natural inhibitors in cabbage also discourage the growth of undesirable Gram-negative and Gram-positive bacteria.
Starters (Natural) and Growth
The raw material has a large number of undesirable organisms and a small population of lactic acid
bacteria (<1%). Among the lactic acid bacteria, most are Lactococcus spp. and Leuconostoc spp., and
a small fraction is Lactobacillus spp. and Pediococcus spp. During fermentation, sequential growth
of these lactic acid bacteria occurs. The presence of 2.25% salt, large amounts of fermentable sugars (sucrose, hexoses, pentoses), an absence of oxygen, and a low fermentation temperature facilitate Leuconostoc spp., primarily Leu. mesenteroides, to grow rapidly. When the acidity has reached
approximately 1% (as lactic acid), growth of Leu. mesenteroides slows down. Then Lab. brevis starts
growing rapidly until acid production reaches approximately 1.5%. Then Ped. pentosaceus takes
over and increases the acidity to approximately 1.8%. Finally, Lab. plantarum starts growing and
brings the acid level to approximately 2%.
Biochemistry
Leuconostoc spp. metabolize sucrose, hexoses, and some pentoses in the raw material to lactate,
acetate, ethanol, CO 2 , and diacetyl. Lab. brevis (obligatory heterofermentative, such as Leuconostoc
spp.) ferments sucrose, hexoses, and pentoses to products similar to those by Leuconostoc spp.
Ped. pentosaceus metabolizes hexoses to form mainly lactic acid and some pentoses to lactic acid,
acetate, and ethanol. Lab. plantarum also produces products from sucrose, hexoses, and pentoses
similar to those by Ped. pentosaceus. Leuconostoc spp. produces d(–)-lactate, whereas the other three
species produce dl-lactate.