Lactococcus lactis subsp. cremoris
This is a combination of two common forms of mesophilic and homofermentative cultures. These microorganisms are lactic acid bacteria, Gram-positive, and acid-resistant. They produce lactic acid during fermentation. They grow best in microaerophilic conditions (2-10% oxygen).
Lactococcus delbrueckii subsp. lactis
Lactococci are fermenters that derive their energy from phosphorylation. Under natural conditions, lactococci cannot metabolize citrate. Their metabolic activities play a crucial role in the flavor development of soft cheeses.
Lactococcus lactis subsp. lactis biovar diacetylactis
– Ferments citrate and produces carbon dioxide and diacetyl.
– Can be combined with homofermentative lactococci to produce cheese with small holes.
Streptococcus lactis subsp. lactis
Used for many types of low-temperature cheeses, fresh cheeses, cheddar, and various American cheeses.
Leuconostoc lactis
Used in cheeses with small holes or for soft cheeses because their activity results in less gas production and a diacetyl flavor. Leuconostocs are more acid-tolerant than lactococci and have enzymatic systems for citrate fermentation.
Leuconostoc mesenteroides subsp. cremoris
Often used in the production of butter and buttermilk as it contributes to diacetyl flavor development and produces less carbon dioxide compared to Lactococcus lactis subsp. lactis citrate.
Thermophilic Starter Cultures
Streptococcus thermophilus
This bacterium is responsible for primary acid production. A cocci/rod mixture is commonly used to produce high-temperature cheeses such as Swiss and Italian cheeses. Most thermophilic species have proteolytic activity and use milk proteins. When paired with Lactobacillus bulgaricus, the proteolytic properties of S. thermophilus are less pronounced, as L. bulgaricus provides peptides and amino acids for S. thermophilus growth. S. thermophilus is heat-sensitive and does not grow well at high acid concentrations. Using pure S. thermophilus culture in milk results in a small amount of acid production, forming a weak curd.
Lactobacillus delbrueckii subsp. bulgaricus
Sometimes used as a substitute for Lactobacillus helveticus in high-temperature cheeses. This microorganism cannot use galactose.
Lactobacillus helveticus
Unlike L. delbrueckii subsp. bulgaricus, L. helveticus can consume galactose, making it suitable for reducing browning in mozzarella and increasing proteolysis in cheddar. Residual galactose can increase browning in baked pizza cheese. Therefore, some manufacturers prefer using L. helveticus instead of L. delbrueckii subsp. bulgaricus. L. helveticus cultures are used in many cheeses, including Gouda, cheddar, and low-fat cheeses, for rapid flavor development.
Lactobacillus delbrueckii subsp. lactis
Commonly found in hard cheeses made with raw milk. This strain grows during cheese ripening and can be added in large concentrations with starter cultures. L. lactis significantly influences proteolysis and volatile compounds during the ripening of hard cheeses. Its role in proteolysis is well-documented, but its role in forming volatile compounds remains unproven. This species is also highly acid-resistant.
Lactobacillus acidophilus
Used as a probiotic, this Gram-positive bacterium can be either anaerobic or facultatively anaerobic. It is homofermentative, converting sugars solely into lactic acid. L. acidophilus has antimicrobial effects due to its production of organic acids (lactic acid, acetic acid), hydrogen peroxide, and antibiotic substances (lactocin, acidophilin, acidolin, lactocin B).
Preparation of Starter Cultures
Commercial producers offer starter cultures in freeze-dried, frozen, or spray-dried forms. Dairy producers need to inoculate these cultures into milk or another suitable substrate. The preparation process includes several steps:
- Commercial culture
- Mother culture (first inoculation) from which all other cultures are derived
- Intermediate culture for preparing a larger volume of starter
- Bulk starter culture for dairy product production
Production, Distribution, and Storage of Cultures
Preparation of Commercial Cultures
Genetic techniques offer many methods to develop cultures with specific technological characteristics. However, the commercial culture preparation process is relatively simple.
– Lactic cultures are grown in buffered environments to promote maximum growth without acid inhibition.
– Cells are concentrated by centrifugation.
– The cell concentrate is either freeze-dried or frozen. Frozen (-40°C) or freeze-dried cultures can be stored for several months without losing primary activity. Freeze-dried cultures usually require a longer lag phase, the time between inoculation and rapid cell growth.
Secondary Cultures
In addition to lactic acid cultures, many special or secondary cultures are used to promote specific properties (texture and flavor) in cheese.
- Large holes: Propionibacterium freudenreichii shermanii
- Blue or green molds: Penicillium glaucum, Penicillium roqueforti
- White molds: Penicillium camemberti, Penicillium caseicolum, Penicillium candidum
Smear:
- Mold and yeast
- Various coryneform bacteria, including Brevibacterium linens, several Micrococcus species, and Staphylococcus
Ripening aid cultures in cheese:
- Yeast or bacterial cultures added in addition to regular lactic acid cultures
- Reduced growth cultures that primarily assist enzymes
- Specific strains of Lactobacillus and Pediococcus intended to grow during cheese ripening and aid enzymes.
For more information about starter cultures and prices, contact our experts.
