A method of and apparatus (18) are described for assessing fat in whey in the making of a dairy product in accordance with a dairy product recipe. The method comprises the steps of: a. using one or more optical sensors (61, 62, 63, 64) to sense at least one stream (22, 24, 27, 29) of whey separated from curd in dairy product making apparatus (18) and generate one or more signals indicative of the degree of occlusion of the stream (22, 24, 27, 29) of whey; b. converting or processing one or more said signals as a measure of the specific mass of fat lost from curd in a dairy product making plant (18) in the stream of whey; c. assessing whether the value of specific mass of fat lost obtained in Step b lies within or outside a predetermined fat loss range; and d. if the said value of specific mass of fat lost is outside the predetermined range, adjusting the recipe so that the value of specific mass of fat lost lies within the predetermined range.
