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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
SOME DISTINCTIONS BETWEEN PEPSIN AND PEPTASE' B y DR. R. WAEL
The far-reaching influence of peptonizing ferments in t h e brewing industry on t h e stability of t h e product, together with t h e fact t h a t very little has been published on t h e nature and properties of t h e vegetable ferment, has led me t o investigate t h e peptase of barley malt. Although I shall not a t t e m p t t o go into experimental details a n d d a t a to-day, t h e time being short and some of our experiments being still incomplete, I will state in a general way only some of t h e differences between pepsin and peptase, which have become apparent in t h e course of m y work. One of t h e chief differences between these two is t h a t while pepsin (the proteolytic ferment derived from t h e animal organism) is comparatively easy t o obtain in a dry form approximating purity, t h e same does not hold true of t h e vegetable peptase. So far, t o my knowledge, t h e peptase has not been isolated, and our own experiments dealing with the obtaining of dry, stable, peptic preparations of vegetable origin have not been very successful. Although I have devised a process which enables me t o produce malt extracts of high peptic strength, as outlined in my communication t o the Eighth International Congress of Applied Chemistry, September, 1 9 1 2 , which has proven of great practical value t o t h e brewing industry, all attempts t o reduce t h e extract t o a dry form without t h e sacrifice of t h e greater part of t h e peptic strength, have failed. Another interesting difference is t h a t while pepsin acts best in t h e presence of mineral acid-preferably hydrochloric-the peptonizing power of t h e peptase of malt is greatly enhanced b y t h e presence of lactic acid. preferably of a bacterial nature. It seems evident t h a t t h e peptic enzyme contained in malt is locked u p (combined with some base, presumably of albuminous nature) and becomes active through liberation by bacterial acidity The digestive power must be generated, as it were, and I find t h a t bacterial lactic acid is the specific activator, having tried a large number of other acids, both mineral and organic, b u t with comparatively little effect. The remarkable fact is t h a t t h e lactic acid necessary t o activate t h e peptase is provided during t h e growth of t h e malt, having been introduced into t h e steeping water with t h e barley. T h e secretion in t h e animal organism of pepsin and its specific activator, hydrochloric acid, which has even led some authors t o t h e belief t h a t active pepsin is not pepsin in the free state, b u t a compound of pepsin with hydrocliloric acid, is thus seen t o offer quite a close parallel. The optimum temperatures of thesc two proteolytic ferments, t h a t is, t h e temperature a t which t h e proteolytic action proceeds most favorably, also differ. While this temperature lies in t h e vicinity of 50'' C. in t h e case of pepsin, I have found the most favorable temperature for the most thorough digestive action of t h e peptase t o be as low as 3 j - - 4 O 0 c. Xgain, peptase in solution is rapidly destroyed a t 60' c. 1 Presented a t the meeting of the Chicago Section of the American Chemical Society, June 13. 1913.
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while pepsin is not. Furthermore, t h e peptase of t h e barley grain is capable of inverting albumen at t h e low temperature of say 2' C. while t h e proteolytic action of t h e pepsin a t t h a t temperature is practically nil. All of t h e heat-coagulable albumen contained i n a cold water malt extract will be completely peptonized, which means, converted into t h e non-coagulable form, b y permitting this extract t o s t a n d for a few days a t this temperature, uiz., 2' C. Finally, most of t h e :customary tests employed in physiological chemistry t o measure the proteolytic activity of gastric and :similar juices, give no satisfactory results when applied t o t h e peptase of barley grain. I have reference t o such methods as those devised by Jacoby, Volhard, etc., a n d t h e well-known fibrin digestion test. So far t h e gelatin test depending upon t h e liquefaction of gelatine b y proteolytic ferments, suggested b y Schidrowitz, and which I have slightly modified, has proven t h e one most applicable and most reliable in-measuring t h e peptic action of malt extracts . Another almost equally reliable criterion of t h e peptic strength is auto-digestion-the amount of coagulable albumen remaining in a malt extract after t h e same had been subject t o t h e action of t h e peptonizing enzyme for a given period and a t a given temperature being determined b y means of heat coagulation. At t h e beginning of this paper I have mentioned t h e application of these pepticimalt extracts t o practical brewing, and would like t o add t h a t b y means of this principle t h e sensitiveness of t h e bottled product t o low temperatures is minimized. Influences t h a t have such detrimental effects on beer which has not attained stability t o a high degree, are high temperatures, like pasteurization and summer temperatures, !ow temperatures, and light. ,411 these effects are due t o the presence, in unstable beer, of colloidal albumen, i. e . , albumen in a semi-soluble or unstable condition, and this albumen is influenced and gradually broken down b y light or heat vibrations, and reverts t o a n insoluble state, as shown by chilling. By employing t h e digestive principle contained in malt, t h e colloidal albumen remaining i n the beer after proper storage and natural treatment throughout, can be transformed before t h e beer reaches t h e bottle, into albumenoids t h a t are desirable in every way, t h a t is, into t h e permanently soluble and stable forms known as albumose and peptones. At some future time I will-make public t h e experimental d a t a and details of these tests, which I have now been conducting for a number of years. 1135 FULLERTON AVE CHICAGO
DETERMINATION OF TOTAL FORMALDEHYDE IN FUM1GATORS AND COMMERCIAL SOLUTIONS' By JACKJ. HINMAN,JR.
Many methods-have been devised for t h e estimation of formaldehyde, most of which are designed for small amounts or mere traces, although t h e methods for t h e 1
Read before the Indiana Section of the A. C. S., Indianapolis, June
13, 1913.
