Solids-Not-Fat in Milk

The solids-not-fat (SNF) in milk are all its constituents other than water and fat. They consist mainly of proteins, lactose and minerals, together with small quantities of water-soluble vitamins and other non-fat substances.

Constituents included in solids-not-fat

SNF is a collective compositional category, not a single substance. Its principal constituents are:

• Lactose is the principal carbohydrate, or sugar, naturally present in milk.
• Proteins include casein and whey proteins.
• Minerals include calcium, phosphorus, potassium and other mineral constituents present in milk.
• Water-soluble vitamins, including B-group vitamins and vitamin C, occur in small quantities and form part of the non-fat constituents.

Distinction from fat and total solids

Milk can be understood as water plus two groups of solids: milk fat and solids-not-fat. Removing water leaves the total solids; excluding fat from those total solids gives SNF.

• Water and milk fat are excluded when calculating SNF.
• Total solids = milk fat + solids-not-fat, with all components expressed on the same basis.
• SNF is therefore not synonymous with protein content: lactose, minerals and other non-fat constituents also contribute to it.