58 



On a 6i Rennet" Ferment. [Nov. 22 y 



of the seeds as they swell up. From this mass the fluid part may be 

 readily separated by using a centrifugal machine (such as is used in 

 sugar refining), and it can then be easily filtered through filter-paper • 

 without the centrifugal machine the separation of the fluid from the 

 residue of the seeds is tedious and imperfect, 40 grms. of the seeds 

 treated as above with 150 cub. centims. of 5 per cent, sodic chloride 

 solution gave an extract of which 0*25 cub. centim. clotted 20 cub. 

 centims. of milk in twenty-five minutes, and O'l cub. centim. clotted a 

 similar portion of milk in one hour. When added in these propor- 

 tions the curd formed is quite white. The presence of the colouring- 

 matter is, howeA^er, perhaps on the whole unimportant, since even if a 

 larger quantity of the ferment extract is added in order to obtain a 

 very rapid coagulation the colouring-matter is obtained chiefly in the 

 whey, the curd being white.* 



The question of preparing an extract which should be capable of 

 being kept for a considerable time is perhaps of importance. 

 Ordinary commercial rennet usually contains a large amount of sodic 

 chloride and some alcohol. One specimen I analysed contained 

 19 per cent, of common salt, and 4 per cent, of alcohol. I have, there- 

 fore, added to the 5 per cent, chloride extract mentioned above,, 

 enough salt to raise the percentage of this to 15 per cent., and also 

 alcohol up to 4 per cent. The activity of the extract is not 

 appreciably altered by this, and such a preparation corresponds very 

 closely in activi ty with a commercial solution of animal rennet with 

 which I compared it. The possibility of making extracts which may 

 be expected to keep is thus indicated, but of course time alone will 

 show whether the activity of the ferment is impaired to any important 

 extent by such keeping. 



I may add in conclusion that I have coagulated a considerable 

 volume of milk with a,n extract such as I have described, and prepared 

 a cheese from the curds. I have also given a portion of the extract 

 to a professional cheese-maker who has used it as a substitute for 

 animal rennet in the preparation of a cheese. The product thus 

 obtained, and the statements of the person who has made the 

 experiment for me, lead me to suppose that extracts of the seeds of 

 Withania can be used as an adequate and successful substitute for 

 animal rennet. 



* It is extremely probable that some stage in the growth or ripening of the seeds 

 of Withania might be found at which the development of colouring-matter is slight,, 

 while at the same time the ferment is present in considerable quantity. 



