BACTERIA IN FOODS 21/ 



long way on the road towards a good cream-ripening. Re- 

 cently, however, anew method has been introduced, largely 

 through the work and influence of Professor Storch in Den- 

 mark, which is based upon our new knowledge respecting 

 bacterial action in cream-ripening. We refer to the artificial 

 processes of ripening set up by the addition oi pure cultures 

 of favourable germs .^ If a culture of organisms possessing 

 the faculty of producing in cream a good flavour be added 

 to the sweet cream, it is clear that advantage will accrue. 

 This simple plan of starting any special or desired flavour 

 by introducing the specific micro-organism of that flavour 

 may be adopted in two or three different ways. If cream 

 be inoculated with a large, pure culture of some particular 

 kind of bacteria, this species will frequently grow so well 

 and so rapidly that it will check the growth of the other 

 bacteria which were present in the cream at the commence- 

 ment and before the starter was added. That is, per- 

 haps, the simplest method of adding an artificial culture. 

 But secondly, it will be apparent to those who have followed 

 us thus far, that if the cream is previously pasteurised at 70° 

 C. these competing bacteria will have been mostly or entirely 

 destroyed, and the pure culture, or starter, will have the 

 field to itself. There is a third modification, which is some- 

 times termed ripening by natural starters. A natural 

 starter is a certain ^mall quantity of cream taken from a 

 favourable ripening — from a clean dairy or a good herd — 

 and placed aside to sour for two days until it is heavily im- 

 pregnated with the specific organism which was present in 

 the whole favourable stock of which the natural starter is 

 but a part. It is then added to the new cream the favour- 

 able ripening of which is desired. Of the species which 

 produce good flavours in butter the majority are found to 



^ Such pure cultures for such purposes are in the United States termed 

 *' starters," because they start the process of special ripening. For the sake of 

 convenience the term will be used here. 



