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Refrigerated storage of raw milk is used to limit the growth of microorganisms in milk prior to processing. It has been known for some time that the quality and yield of cheese produced from bulk cooled milk may be adversely affected by this procedure (Weatherup et al., 1988; Weatherup and Mullan, 1993). The reduced yield and poor quality may be due to physico-chemical changes in the state of several milk components e.g. dissociation of micellar casein, mainly Κ-casein into a soluble phase, occurs during the first 48 h of storage at 4° and 7° C. This results in losses of fat and curd fines, weaker curd, more moist curd and a slightly lower yield. Partial reversal of dissociation occurs after further storage. The reduced yield and quality can also be due to the activity of proteases and lipases produced by psychrotrophic bacteria.
Despite the work that has been done over many years milk is still being stored for extended periods (1-3+ days on some farms) and cheesemakers are again (2019) reporting problems with the yield and quality of cheese produced using this milk.
Following several queries related to milk quality and cheese manufacture I am providing a report written by Wilf Weatherup and me some years ago that may be helpful.
A simple calculator has been provided using the total viable count of milk prior to pasteurisation and a regression equation to predict the grade value of Cheddar cheese.
As more pressure is applied to reducing production costs, attention is increasingly being given to maximising the yield of high moisture cheeses including Cottage cheese. While yield is important, cheese quality must also be considered whenever attempts are being made to improve or optimise yield.