1. Lactic Acid Fermentation
Making yogurt
Lactic Acid Fermentation

2. Introduction
Yogurt production demonstrates fermentation by Streptococcus thermophilus and Lactobaacillus bulgaricus
Heated milk is inoculated and maintained at a given temperature causing bacteria to grow and ferment lactose, the suger in milk
The bacteria produce lactic acid which causes the milk to coagulate

3. Materiales Food grade containers, washed Food grade thermometer
Hotplate
Beaker tongs
2 cup of milk
1/3 cup nonfat dry milk
2 table spoons yogurt
pH meter

4. Procedure
Combine milk with nonfat dry milk and heat in water bath to 87ºC
Hold at that temperature for 10 to 20 minutes
Cool to 46ºC and record the pH of the mixture
Place the plain yogurt in jar and gradually blend in the warm milk
Cover and place in oven or incubator at 45ºC

5. Procedure
Allow to stand undisturbed until the mixture is firm when the jar is gently wiggled
This may take as long as 6 to 8 houres