4.—(1) Without prejudice to the compositional requirements set out in the table in this Schedule, the protein content of milk may be adjusted to a minimum content of 34% by weight (expressed on fat-free dry matter) by the addition or withdrawal (or both) of milk constituents in such a way as not to alter the ratio of whey protein to casein in the milk being adjusted.
(2) Authorised raw materials for protein adjustment purposes referred to in paragraph (1) are as follows—
(a)milk retentate, which is the product obtained by concentrating milk protein by ultrafiltration of milk, partly skimmed milk or skimmed milk;
(b)milk permeate, which is the product obtained by removing milk proteins and milk fat from milk, partly skimmed milk or skimmed milk by ultrafiltration; and
(c)lactose, which is a natural constituent of milk normally obtained from whey with an anhydrous lactose content of not less than 99.0% m/m (mass over mass) on a dry basis, and which may be anhydrous or contain one molecule of water of crystallisation or be a mixture of both forms.