The impact of milk composition on cheddar cheese manufacture

Cow's milk is principally made up of lactose, fat and protein together with minerals and vitamins. However, the prima compositional factor determining the processing quality of milk for the manufacture of cheese is the protein content. Milk with a high protein concentration, particularly casein content, gives a high yield of cheese, has good processability and produces good quality cheese. The higher the ratio of casein to whey proteins the more suitable is the milk for cheddar cheese. Fat content is also important but should be in the appropriate ratio to casein; the casein:fat ratio is generally between 0.64 and 0.72. The protein level in milk and its suitability for cheddar cheesemaking are affected by production factors such as stage of lactation, feed quality, herd health and environmental conditions. High-quality feed is the most important determinant of high protein milk. However, mastitis and environmental factors such as heat stress have negative effects. The effect of season appears to be small after the quality and availability of feed and climatic effects are taken into account. There is conflicting evidence of the relationship between the content of individual caseins and the suitability of milk for cheddar cheesemaking. However, evidence seems to be reasonably strong for a positive effect of kappa-casein on micellar casein stability and superior cheesemaking properties. There is also a strong evidence for the effects of some genetic variants of milk proteins on cheddar cheesemaking. Milks containing the variants beta-lactoglobulin BB and kappa-casein BB, alone or in combination, have been shown to be superior to milks containing the corresponding AA or AB variants. The reason for this is not clear, but it is thought to be related to the differences in protein structure, increased ratio of kappa-casein to other caseins and increased casein:whey protein ratio in these milks. Both positive and negative correlations between the contents of various minerals and salts, and the processability of milk for cheddar cheesemaking have also been reported. However, the only one which stands out is ionic or free calcium; milks with high Ca++ have better cheesemaking properties than milks with low Ca++ concentrations.