F13.The intervention agencies shall check the quality of skimmed-milk powder using the analytical methods set out in Part IV of this Annex on the basis of samples taken in accordance with the rules set out in Part VI of this Annex. The checks must establish that, except authorised raw materials used for protein adjustment as referred to in Annex I(4)(b) to Council Directive 2001/114/EC the skimmed milk powder does not contain other products, in particular buttermilk and whey, as defined in Part IV of this Annex.