Whey

Liquid left after milk is curdled to make cheese or strained yogurt.

Characteristics

Contains about 93 % water, 5 % lactose and 0.8 % protein.
Sweet whey has a pH of 5.6 or above; acid whey 5.1 or below.
Supplies sugars and minerals that feed lactic acid bacteria.
Approved in the EU as a basic substance (Implementing Regulation (EU) 2016/560).

Role in the preparation: It serves as a source of lactose and lactic acid bacteria in ferments such as biol and microbial inoculants.

Caution: It spoils quickly: use it fresh, keep it cold, and never pour it into watercourses because of its high organic load.

Sources: Whey - Wikipedia · Commission Implementing Regulation (EU) 2016/560 approving the basic substance whey - EUR-Lex

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.