402 BACTERIA IN DAIRY PRODUCTS 



Abnormal fermentations of cheese are caused by a great variety of bacteria 

 among which the colon-aerogenes group is perhaps the most troublesome. These 

 bacteria develop while a supply of lactose is still available and cause gassy fermenta- 

 tions while the curd is in the vat in the case of Cheddar or in the press in Swiss cheese. 

 Gassy fermentations which come later are likely to be caused by the welchii group. 

 A very disagreeable defect of Swiss cheese is caused by the putrificus bacilli. Pig- 

 ment-forming bacteria sometimes cause red or "rusty" spots in cheese/ and bitter 

 flavors have been traced to activities of torula yeasts.^ 



■ Connell, W. T.: Canada Commr. Agric. &° Dairying Rep., iSgj, Part i6, p. 3. 1898. 



'Harrison, F. C: Rev. gtn. du laii, i, 457, 485. 1902. 



