AMYLASE 91 



Peroxidases. The detection of this ferment may be carried 

 out by any of the following methods, all of which are reliable. 



Rothenfusser's Method. Two solutions are required: (1) 

 a 6 per cent solution of pure para phenylenediamine hydro- 

 chloride, and (2) a 1.8 per cent solution of crystallised guiacol 

 in 96 per cent alcohol. 15 c.cms. of No. 1 are added to 135 

 c.cms. of No. 2 and the mixture preserved in an amber-coloured 

 bottle. To 10 c.cms. of milk add 0.5 c.cm. of the reagent and 

 3 drops of hydrogen peroxide (3 per cent). A blue violet colour- 

 ation indicates a positive peroxidase reaction. 



Wilkinson and Peter's Method. To 10 c.cms. of milk add 

 1 c.cm. of a 10 per cent solution of benzidine in 96 per cent alco- 

 hol, 3 drops of 30 per cent acetic acid and finally 2 c.cms. of 

 3 per cent hydrogen peroxide. Peroxidases produce a blue 

 colouration which is usually localised in the precipitated casein- 

 ogen. 



Bellei's Method. To 10 c.cms. of milk, add three drops of a 

 1.5 per cent aqueous solution of ortol and two drops of a 3 

 per cent hydrogen peroxide solution. A red colouration indi- 

 cates the presence of peroxidases. 



Peroxidases, like reductase, are more concentrated in the 

 cream layer of milk though it is impossible to establish any 

 definite parallelism between the butter fat content and the 

 density of the peroxidase reaction. 



Catalase. The activity of this ferment is estimated by 

 mixing 15 c.cms. of milk and 5 c.cms. of 2 per cent hydrogen 

 peroxide in a special tube devised for this purpose by Lobeck. 

 In this apparatus the oxygen liberated is collected and measured 

 in a graduated tube previously filled with water. The libera- 

 tion of the oxygen is accelerated by incubation at blood heat 

 for two hours. Fresh milk usually evolves one to three cubic 

 centimetres of oxygen and results materially higher than these 

 are usually indicative either of excessive bacterial contamina- 

 tion or of excessive amounts of cellular elements produced by 

 physiological or pathological irritations of the udder. 



Amylase. Into each of 10 test tubes, 10 c.cms. of milk are 



