184 ◾ Fundamental Food Microbiology
relatively high concentration of proline produced by propionibacteria). Very little lipolysis occurs
during curing.
Genetics
Rapid production of lactate in large amounts from lactose by lactic acid bacteria and their resistance to phages (some Lab. helveticus strains have temperate phages that are activated at high
processing temperatures, causing starter failure) are important considerations. Propionibacterium
strains should produce CO 2 at proper rates for desirable numbers and sizes of eye formation (uniform distribution of medium-size eyes preferred).
Microbial Problems
Spores of Clostridium tyrobutyricum, present in raw milk or entering as contaminants, can germinate, grow, and cause rancidity and gas blowing in this low-acid cheese. Nisin has been used as a
biopreservative to control this problem (also see Chapter 20).
Microbiology of Blue Cheese 7
Characteristics
Blue cheese is a semihard (46% moisture, 50% fat), mold-ripened cheese made from whole milk
(cow’s milk). It has a crumbly body, mottled blue color, and sharp lipolytic flavor.
Processing
1. Homogenized, pasteurized, starter added, and incubated at 90°F (32.2°C) for acidity to
increase to 0.2%.
2. Rennet added, incubated for firm set, cut, cooked at 100°F (37.8°C), and whey drained.
3. Curd collected in hoop, drained 16 h, and salted in brine for 7 days.
4. Spiked to let air get inside. Mold spores added, stored at 50°F (10°C) in high humidity for
4 weeks.
5. Stored at 40°F (4.4°C) for curing for 3 months.
Starters and Growth (Controlled Fermentation)
Lac. lactis ssp. cremoris or lactis and Leu. cremoris or lactis serve as primary starters. Pen. roquefortii
spores serve as secondary starters. The lactic starters grow until curing, and from lactose, they produce lactate, diacetyl, acetate, CO 2 , and acetaldehyde. Mold spores, during storage at 50°F (10°C)
in high humidity, germinate quickly, produce mycelia, and spread inside to give the mottled green
appearance. Their growth continues during curing. Puncturing the inside of the cheese helps
remove CO 2 and let air in to help the growth of molds.
Biochemistry, Genetics, and Problems
Lactococcus species produce mainly lactic acid from lactose, whereas Leuconostoc species produce
lactic acid, diacetyl, CO 2 , and acetate. Proteolysis is quite limited by the lactic starters. Molds
relatively high concentration of proline produced by propionibacteria). Very little lipolysis occurs
during curing.
Genetics
Rapid production of lactate in large amounts from lactose by lactic acid bacteria and their resistance to phages (some Lab. helveticus strains have temperate phages that are activated at high
processing temperatures, causing starter failure) are important considerations. Propionibacterium
strains should produce CO 2 at proper rates for desirable numbers and sizes of eye formation (uniform distribution of medium-size eyes preferred).
Microbial Problems
Spores of Clostridium tyrobutyricum, present in raw milk or entering as contaminants, can germinate, grow, and cause rancidity and gas blowing in this low-acid cheese. Nisin has been used as a
biopreservative to control this problem (also see Chapter 20).
Microbiology of Blue Cheese 7
Characteristics
Blue cheese is a semihard (46% moisture, 50% fat), mold-ripened cheese made from whole milk
(cow’s milk). It has a crumbly body, mottled blue color, and sharp lipolytic flavor.
Processing
1. Homogenized, pasteurized, starter added, and incubated at 90°F (32.2°C) for acidity to
increase to 0.2%.
2. Rennet added, incubated for firm set, cut, cooked at 100°F (37.8°C), and whey drained.
3. Curd collected in hoop, drained 16 h, and salted in brine for 7 days.
4. Spiked to let air get inside. Mold spores added, stored at 50°F (10°C) in high humidity for
4 weeks.
5. Stored at 40°F (4.4°C) for curing for 3 months.
Starters and Growth (Controlled Fermentation)
Lac. lactis ssp. cremoris or lactis and Leu. cremoris or lactis serve as primary starters. Pen. roquefortii
spores serve as secondary starters. The lactic starters grow until curing, and from lactose, they produce lactate, diacetyl, acetate, CO 2 , and acetaldehyde. Mold spores, during storage at 50°F (10°C)
in high humidity, germinate quickly, produce mycelia, and spread inside to give the mottled green
appearance. Their growth continues during curing. Puncturing the inside of the cheese helps
remove CO 2 and let air in to help the growth of molds.
Biochemistry, Genetics, and Problems
Lactococcus species produce mainly lactic acid from lactose, whereas Leuconostoc species produce
lactic acid, diacetyl, CO 2 , and acetate. Proteolysis is quite limited by the lactic starters. Molds