Vol. XIV. X... 352. 



THE AGRICULTURAL NEWS. 



•TIT 



'The milk and water were alw rys measured inti 

 ks and mixed by shaking. The enzyme solution was 



1 ' v 



tat. At > 



n i I to each, and 



t 



app 3 75 c.c. of final volume. The 



was then precipitated by slowly adding 0'5 c.c. of copper 

 sulphate solution (60 grams per litre), followed by 0*5 c.c. 

 ■ acetic acid, the solution being vigorously stirred 



(hi: ! 



'The contents ol the m ished into 



LOOc.c measuring cylinder id to stan 



time to permil the curd to settle, after which they n 

 filtered through 1 1-centimetre ashless papers, which bad b 

 previously numbered, dried al 100°, and weighed. It 

 frequently happens that filtral very slowly, 



in which rase it is not advisable to wait until 

 all the liquid has passed tin ; i, bul is better to 

 proceed with the washing. The curd is washed back into 



the cylinders with distilled water wan 1 to about 60°, and 



is thoroughly disintegrated bj of a rubber-tipped 



stirring rod. The sediment now settles readily, and the 

 solutions filter rapidly. The undigested protein is washed 

 three more times in this manner to remove - [gars and soluble 

 digestion products; gentle suction is applied to remove the 

 .surplus water, and the papers are dried to constant weight at 

 100'. No correction for the amount, of papain used is 

 necessary, as it is not precipitated by copper sulphate and 

 acetic acid. 



'Tlie weight of protein digested by the various amounts 

 of papain may be calculated from the blank in which no 

 enzyme was used. The entire determination with the 

 exception ol drying may be made in from three to four hours, 

 and duplicate analyses agree within about 2 per cent. The 

 curves obtained in this manner show at a glance the relative 

 proteolytic power possessed by samples of papain, as well as 

 the rate at which digestion has proceeded with increasing 

 amounts of enzyme. Xo antiseptic is necessary with such 

 .short periods of incubation.' 



A isiderable number of samples of papain obtained 



locally at .Manila and imported from Ceylon, Mexico and the 

 W est Indies were examined by the foregoing method, and 

 results were obtained which showed the percentage of total 

 protein digi sted by increasing amounts of papain, and which 

 also di iwed the marked differences existing in the proteolytic 

 activity i.' the samples. Thu- the amount of milk protein 

 digested in thirty minutes at to by 1 milligramme of West 

 Indian papain was found to excel that digested under 

 similai conditions by 100 milligrammes of a sample repre- 

 i] liuary ( 'eylon papain. 



1 ration is given next in the paper to various 

 methods of preparing papain. The first experiment in this 

 id for its object the decision as to whether fresh 

 latex is much more active than dried papain. It was found 

 that fresh latex is considerably more active than dried papain 

 from the Antilles, although both preparations are capable of 

 digesting approximately the sami mount ol milk protein 

 with relatively large nuts .it enzj present. In 



another experiment it was found ! dried papain is not 



necessarily less active than the fresh latex; hut in this ca e 

 it must be remembered that considerabl i ire wa given the 

 sample to insure rapid drying, the exclusion of dust, etc. It 

 was also dried promptly after collection. This is very 



important, a [ly in pap 



latex with the p 



drying 

 ll latex is ill I. But i 



r difficull ti 

 .Many e 



material I Icohol. This 



met! [lent 



results provided ll ,hol is limited to 



as short a time i ile. The sample of papain 



lined by this treatment in the 

 very active, 10 milligrammes being capable of digesting as 

 much milk protein as 22 milligrammes ol the PJ sun- 



dried papain or 10 milligrammes ■ 



This probably repre ipain that could 



prepared commercially. Its manufacture by this method 

 would necessitate a still for recovering the waste alcohol. The 



use of ether would hardly he practicable in Hop tries 



but could he employed bj firms using papain, if desirable 

 Papain prepared in this manner is nearly soluble in water, 

 giving a solution with small flocks of white insoluble material. 

 The solution rapidly curdles milk, with the formation of a fine 

 curd that quickly redissolves. This property of papain should 

 make it of great value in preparing milk for infant feeding, as 

 the formation of heavy indigestible curds in the stomach may 

 thus be avoided. 



In regard to the ra if digi stion by papain, it was found 

 that the reaction proceeded rapidly during the first ten mine 

 and practically reached its maximum within an hour. It 

 naturally varies with the surrounding physical conditions. 



The question of digesting under various conditions was 

 dealt with in a further series of experiments, particularly 

 in relation to the papain digestion in acid solution. It was 

 found that amounts of hydrochloric acid up to 0'0(i per cent, 

 have only a slight retarding action on the digestion of the- 

 gum. Increasing amounts from O'0( i to 0T 3 per cent, acid 

 very greatly reduce the activity of the enzyme, although 

 any further increase up to - 20 per cent, causes practically^ 

 no change. A sharply defined range of acidity thus reduces 

 the digestion to one half its former value. In regard to 

 hydrocyanic acid it was found that this increased the 

 percentage of milk protein digested by papain. The presence 

 of 0"02 per cent, acid was sufficient to give the maximum 

 effect, higher concentrations causing no further increase.. 

 These effects of hydrocyanic acid and hydrochloric acid are 

 very remarkable. 



Digestion at various temperatures was the next aspect 

 to receive attention, and it was found that papain shows 

 a remarkable activity at low temperatures. There appears 

 to he very little difference in the rate of digestion in the 

 neighbourhood of Id to 50°. The digestion at 7<»° shows 

 that the activity in the presence of large amounts of enzymes 

 is not greatly weakened, but with decreasing percentages of 



gum the loss In inc., more marked. Papain exhibits 



a rather remarkable n i heat, hut if a solution is 



rapidly warmed to 100 and allowed to boil live sei ■ 

 and is immediately cooled with ice, it no longer shows any 

 proteolytic activity. 



In regard to standard evaluation of papain, it is suggested 



that the average of d tibns carried out in 



a manner previously described in connexion with methods of 

 analysis, using 25 c.c. of milk, •_':; c.c. of distilled water, and 

 2 c.c. of a filtered olution representing 10 milligrammes of 

 papain digested tor thirty minutes £1 In be accepted as the 

 i nd. and that the proteolytic activity of the gum be; 

 designated by the ratio obtained of 1 part of papain to thfe_ 

 d protein. 



