430 



BUTTER, CHEESE, ETC. 



globules are solid at low temperatures this view is untenable. 

 Soxhlet holds that churning consists in the rupture of a solid 

 membrane, which he believes exists round the fat globules ; as 

 the existence of such a membrane is disproved, this view cannot 

 be accepted. Storch attributes churning to the gradual rubbing 

 off of a semi-solid membrane of " mucoid substance." and this 

 hypothesis has much to recommend it ; the whole of the evidence 

 points to the existence of a layer, which is not solid, round the 

 fat globules. As previously stated, the author cannot reconcile 

 Storch's theory that this layer consists of " mucoid substance " 

 with known facts ; but it appears very highly probable that there 

 is a layer, the composition of which is for the present purpose 



Fig. 49. Churn. 



immaterial, round each fat globule. As it is improbable that 

 this layer is elastic, the effect of the impact of one fat globule 

 on another will be to squeeze out the layers between them, and 

 bring the globules within the sphere of each other's attraction. 

 In this way nuclei will be formed, which will, on continued 

 churning, increase in size ; as the nuclei get larger and larger, 

 the resistance, owing to fluid friction on their surfaces, will 

 gradually bear a smaller and smaller proportion to the force 

 tending to bring them to the surface, and, at a given moment, 

 the butter will " come." This theorv is in accord with all the 



