Mother and Bulk Starter Culture Manufacture

Mother Starter Culture:
The mother starter is a concentrated, pure culture used to inoculate bulk starter. High-quality skim milk is selected and heat-treated (90–95°C for 30–60 minutes) to eliminate microorganisms, denature proteins, and drive off gases. After rapid cooling to the optimal temperature (20–22°C for mesophilic or 42–45°C for thermophilic), the milk is aseptically inoculated with a small amount of pure, lyophilized, or frozen commercial culture. It is incubated at the precise temperature for 12–16 hours until a firm coagulum and desired acidity are achieved. The culture is then cooled to 4°C and stored for 1–2 days under aseptic conditions.

Bulk Starter Culture:
Bulk starter is prepared daily from mother starter to inoculate production milk. Skim milk is heat-treated (85–90°C for 30 minutes), cooled, and inoculated with 0.5–2% mother starter. It is incubated for 3–5 hours until the required acidity develops, then cooled to 4°C, gently agitated, and used immediately or stored for up to 24 hours.

Defects and Prevention:

• Sluggish/Inactive Starter: Caused by bacteriophage attack, antibiotics, poor handling, or temperature errors. Prevent by phage rotation, testing milk, aseptic handling, and precise incubation.
   
• Off-Flavors/Abnormal Acidity: Due to contamination, wrong parameters, or unbalanced cultures. Prevent with strict hygiene, proper inoculation, and time-temperature control.
   
• Poor Texture: Arises from low solids, over-agitation, or unsuitable culture mix. Prevent with optimal solids, gentle handling, and balanced culture.

Phage Contamination: Caused by airborne phages or poor sanitation. Prevent with closed vats, filtered air, positive pressure, stringent cleaning, and culture rotation.