My doubts are on the timing of the curd formation and how the timing is dependent on various parameters like temperature or the volume of the ‘starter’ curd (Where did I read about measuring curdling time with one teaspoon of starter curd and one tablespoon?).
Real-Time Monitoring of Yogurt Fermentation Process … by scientists at Biomeasurement Technology Laboratory, Graduate School of Agricultural Science, Kobe University shows that the fermentation process follows a S-curve with rapid change between 3.3 hours and 4.6 hours after start of curdling. As the Biomeasurements Technology Lab wanted to propose a non-invasive Near Infrared Spectroscopy to measure the curdling, they did not vary the temperature nor the quantity of starter yogurt nor its different types (only Bulgarian, no Japanese, nor Indian etc).
At CUBE we can try a Reflectometer to measure the timing of curd formation. Reflectometer costing around Rs 1000 are available in India. Then we can find the ideal temperature for fastest curd formation.
I feel that there is something like 50 % Growth time (like half-life for radio-activity) for the lactobacillus, say to grow from 8000 to 12000 in 1 cc. As it is easier to measure the number of bacillus after 2 hours, 4 hours, 6 hours etc most measurements are timed this way and the 50% growth time can be estimated. I think that the 50% Growth time for lactobacillus LAB is about 10 minutes. Then about 112 cc of milk will be curded in 70 minutes using 5 cc of starter curd. If 10 cc of starter curd is used, it will take 60 minutes to form 112 cc of curd.
The temperature of the milk is very important. The starter curd for non-sour curd is around 43 degree centigrade. But I have learned that it is more important to shake the milk after adding the starter curd. The Operating Procedure I apply is:
- Add 15 cc of the starter curd to the 900 cc of milk at around 40 degree C in a 1000 cc vessel.
- Shake the 1000 cc container with a spoon for 10 seconds in one direction.
- Stop shaking the spoon for 10 secs.
- Shake the container for 10 secs with the spoon in a direction +120 degrees to the first.
- Stop shaking for 10 secs.
- Shake the container for 10 secs with the spoon in a direction -120 degrees to the first.
- Close the container.
- After around 3 hours the container will be seen to contain well formed curd.
Maybe the churning, non-churning steps make the LAB to spread throughout the milk to form a solid looking curd.