Butter

Butter

	Butter - Butter is made by churning pasteurized sweet or sour cream, to separate fat globules from the other constituents. The liquid portion, buttermilk, drained off, and the granules are further processed. Butter consists of about 80 percent fat, small percentages of lactose and protein, and often 2 percent salt. The remainder is water in the form of minute droplets dispersed throughout the butterfat. The, salt is dissolved in this water.
The cream from which the butter is churned may be soured naturally or by the addition of a culture of organisms known as starter to improve the flavour. The advantages of first souring the cream are: (l) the yield of butter is increased, owing to a better separation of fat, and (2) the aroma and flavour may be greatly improved. Before a starter is added, the cream is pasteurized at 71° C for 30 minutes.
These eliminate undesirable organisms and destroy milk lipase that would otherwise cause rancidity during storage of butter. The starter consists of two types of organism; 1. Those producing a high acidity e. g. Streptococcus lactis and S. cremoris and 2. Those imparting characteristic aroma and flavour e. g. Leuconostoc citrovorum and L. dextramicum. The keeping quality of well made butter is good. Although it has retained some of the bacteria of the cream, it is low in sugar and protein. Since the salt is all dissolved in aqueous fraction the water present contains a high percentage of salt.
This prevents the growth of bacteria. Also, water droplets are so evenly distributed and so minute that bacteria which are in these droplets, cannot multiply because of space limitation. Another factor which restricts microbial growth is anaerobic condition except at the surface, where aerobic microorganisms may develop. Undesirable changes which take place after butter has been manufactured are produced largely by the growth of microorganisms. These are mainly aerobic microorganisms which grow on the surface of the butter after its manufacture. The microorganisms which cause rancidity, discoloration and off flavours are as follows:
	1. Moulds of the genera Asrpergilhl8, Mucor, Rhizopus, Clados porium, Alternaria. 2. Yeasts of the genus Torula. 3. Bacteria of the genera Pseudomonas and Achromobacter. Microbiological tests carried out on butter are very limited. Total bacterial count is not considered significant because they are actually added as starter. Yeast and moulds, when numerous, are objectionable in butter.

Their presences indicate either improper pasteurization of cream or recontamination after pasteurization. Samples with less than 10 yeasts and moulds per gram are classified as good. The number of proteolytic bacteria is an indication of keeping quality and the count should be less than 50 per gram.

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