Recipe
- 1 Gallon Milk
- 1 Spoonful Greek Yogurt Starter Culture
Heat milk to 180 F while stirring (to prevent burning). Cool to 110 F. Add starter culture. Leave overnight. Strain trough cheese cloth or special strainer.
Science
Milk contains the natural sugar lactose; however because lactose is a disaccharide, it is unusable for glycolosis. Luckily, the lactobateria naturally present in milk can break the lactose molecules at their glycosidic bond, resulting in glucose and galactose. The reason for heating the milk is two fold: first, increasing the temperature of milk increases the acidity, which induces curling, and second, greek yogurt contains lactobacilli – a thermophilic lactobacteria. Unfortunately, pasturization kills most of the lactobacteria, hence the need for an additional starter culture. As the lactobacteria eat the sugars, they make the milk more acidic, which induces curtling and results in yogurt.
Sources
Provost. The Science of Cooking. Wiley, 2016. Pages 170-173