520 



Pink Discoloration of Cheese. 



[Sept. , 



weeks are interesting. In the eighth week 12§ lb. of wheatl 

 only were consumed. At the end of the week the birds showed 

 an increase in weight of 3 J lb., or 23 per cent. In the ninth; 

 week the food consumed was 61b. of wheat and 7 lb. of maize. 

 This produced an increase of 5 lb., or 29 per cent., in the weight 

 of the birds in spite of the fact that the percentage of increase 

 had been falling since the fourth week. This would seem clearly 

 to point to the value of change of food. 



Not the least important side of the experiment was the 

 interest it aroused in the immediate neighbourhood. 



* * * * * * 



The following note has been communicated to the Ministry 



by Miss Grace Heather Mason, Lecturer in Agricultural 



, . Bacteriology at University College, 



Pink Discoloration _> & * J 



. .Heading : — 



of Cheese. 



An investigation has recently been made 

 in the University College, Reading, with a view to ascertaining 

 the cause of pink discoloration of cheese forwarded for examina- 

 tion from a dairy in Yorkshire. The complaint was that the 

 cheese, although normal in appearance when first cut, developed 

 a pink colour very shortly after cutting, the colour spreading 

 over all the cut surfaces, and shading in tone from a light 

 salmon or rose pink to a violet purple. The cheeses were of 

 small size, weighing from 4 lb. to 7 lb., and were made on the 

 Wensleydale system. 



It appeared that the affected cheeses had been made during 

 a period of ten days in the summer, and that the coloration 

 was first observed when the cheeses were a month old. The 

 dairy maid who made the cheeses was inclined to believe that 

 the pink coloration was due to the rennet used, the supply of 

 which was obtained from a local chemist, and only lasted during 

 the period these particular cheeses were made. It was not, how- 

 ever, possible to obtain a sample of this particular rennet for 

 this view to be confirmed. 



An examination of the affected cheeses showed that freshly 

 cut or broken surfaces were normal in colour at first, but became 

 pink within 12 hours, the colour appearing along the course of 

 fine cracks and veins in the cheese, following the lines of 

 junction of individual pieces of curd. The cheese being of a 

 lightly pressed, spongy texture, this coloration spread rapidly 

 over the surface, leaving the denser portions of curd uncoloured, 

 this giving a marbled or mottled appearance to the cheese. The 

 colour was very marked, and was of a darker pink or violet 



