Microbiology of Fermented Food Production ◾ 183
Biological amines (histamine from histidine and tyramine from tyrosine) can form by decarboxylation (by starter decarboxylases) of some amino acids, especially in cheese ripened for a long
time. Allergic reactions can occur from consuming such cheese. Secondary flora may have an
important role in such amine formation.
Microbiology of Swiss Cheese 7
Characteristics
Swiss cheese is made from partially skimmed milk (cow’s milk) and coagulated with acid and
rennin; it is hard and contains approximately 41% moisture and 43% fat. The cheese should have
uniformly distributed medium-sized eyes (openings). It has a sweet taste, resulting from proline,
and a nutty flavor.
Processing
1. Pasteurized, starter added, and incubated at 90°F (32.2°C) for acidity to increase by 0.2%.
2. Rennin added, incubated for firm coagulation, cut in 1/8-in. cubes, and cooked for 1 h at
125°F (51.7°C).
3. Whey removed, curd pressed for 16 h, cut in blocks, and exposed in brine at 55°F (12.8°C)
for 1–3 days.
4. Surface dried, vacuum packaged, stored for 7 days at 55°F (12.8°C), and transferred to 75°F
(23.9°C) for 1–4 weeks.
5. Cured at 37°F (2.8°C) for 3–9 months.
Starters (Controlled Fermentation)
Starters are Str. thermophilus and Lab. helveticus as primary for acid and Propionibacterium sp. as
secondary for eye formation, taste, and flavor.
Growth
Primary starters grow during fermentation, cooking, and processing; growth of Str. thermophilus
is favored. Propionibacteria grow well during storage at 75°F (23.9°C). During curing, none of the
starters grow. The cells slowly die and release intracellular enzymes.
Biochemistry
Lactose is hydrolyzed by β-galactosidase of both lactic acid bacteria and metabolized by the EMP
pathway. Str. thermophilus produces l(+)-lactic acid, and Lab. helveticus produces d(–)-lactic acid.
Some acetate also forms. Production of large amounts of lactate is very important to facilitate
growth of propionibacteria. During storage at 75°F (23.9°C), propionibacteria convert lactate (by
lactate dehydrogenase) to pyruvate, which is then converted to propionic acid, acetate, and CO 2 .
Eye formation occurs from the production of CO 2 , and the size and distribution of eyes depends
on the rate of CO 2 production. Proteins are hydrolyzed by rennin, intracellular proteinases, and
peptidases of starters, especially propionibacteria, resulting in the production of small peptides
and amino acids, which impart the nutty flavor and sweet taste (sweet taste is attributed to a
Biological amines (histamine from histidine and tyramine from tyrosine) can form by decarboxylation (by starter decarboxylases) of some amino acids, especially in cheese ripened for a long
time. Allergic reactions can occur from consuming such cheese. Secondary flora may have an
important role in such amine formation.
Microbiology of Swiss Cheese 7
Characteristics
Swiss cheese is made from partially skimmed milk (cow’s milk) and coagulated with acid and
rennin; it is hard and contains approximately 41% moisture and 43% fat. The cheese should have
uniformly distributed medium-sized eyes (openings). It has a sweet taste, resulting from proline,
and a nutty flavor.
Processing
1. Pasteurized, starter added, and incubated at 90°F (32.2°C) for acidity to increase by 0.2%.
2. Rennin added, incubated for firm coagulation, cut in 1/8-in. cubes, and cooked for 1 h at
125°F (51.7°C).
3. Whey removed, curd pressed for 16 h, cut in blocks, and exposed in brine at 55°F (12.8°C)
for 1–3 days.
4. Surface dried, vacuum packaged, stored for 7 days at 55°F (12.8°C), and transferred to 75°F
(23.9°C) for 1–4 weeks.
5. Cured at 37°F (2.8°C) for 3–9 months.
Starters (Controlled Fermentation)
Starters are Str. thermophilus and Lab. helveticus as primary for acid and Propionibacterium sp. as
secondary for eye formation, taste, and flavor.
Growth
Primary starters grow during fermentation, cooking, and processing; growth of Str. thermophilus
is favored. Propionibacteria grow well during storage at 75°F (23.9°C). During curing, none of the
starters grow. The cells slowly die and release intracellular enzymes.
Biochemistry
Lactose is hydrolyzed by β-galactosidase of both lactic acid bacteria and metabolized by the EMP
pathway. Str. thermophilus produces l(+)-lactic acid, and Lab. helveticus produces d(–)-lactic acid.
Some acetate also forms. Production of large amounts of lactate is very important to facilitate
growth of propionibacteria. During storage at 75°F (23.9°C), propionibacteria convert lactate (by
lactate dehydrogenase) to pyruvate, which is then converted to propionic acid, acetate, and CO 2 .
Eye formation occurs from the production of CO 2 , and the size and distribution of eyes depends
on the rate of CO 2 production. Proteins are hydrolyzed by rennin, intracellular proteinases, and
peptidases of starters, especially propionibacteria, resulting in the production of small peptides
and amino acids, which impart the nutty flavor and sweet taste (sweet taste is attributed to a