M a y , 1920
T E E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y SUMMARY
Pot barley results from the gradual elimination of the outer layers of t h e barley (chiefly the husk and bran) which is accomplished in from 2 t o 3 pearlings. From 5 t o 6 pearling operations, in which a certain amount of endosperm, in addition t o the husk and bran, is eliminated, are necessary t o make pearl barley a white pearl-like product. Chemical analyses of all the products obtained in the manufacture show ' t h a t the first two operations of pearling, resulting in pot barley, consist in the removal of most of the husk which carries with i t three-fourths of the fiber and seven-eighths of the silica. These two operations, considered essential in order t o remove the portions which cannot be used as a food, cause a loss of 2 2 per cent of the barley material, 2 5 per cent of the protein, 41 per cent of the fat, and 50 per cent of the mineral constituents. I n continuing the operations t o produce pearl barley the following constituents of the grain are removed: 6 5 per cent of the barley material; 74 per cent of the protein; from 80 t o 8 j per cent of the fat, PzOS, K 2 0 , CaO, and MgO; and from 97 t o 98 per cent of the fiber and SiO2. Assuming t h a t j,ooo,ooo bu. of barley are being pearled yearly, 52,000 tons of barley material, consisting of over 1,000tons each of f a t and mineral ingredients and 6 , 7 0 0 tons of protein, are removed. EFFECT OF VARYING THE AMOUNT OF INOCULUM AND CONCENTRATION ON THE DETERIORATION OF SUGAR BY MOLDS1 By Nicholas Kopeloff DEPARTMENT OF BACTERIOLOGY, LOUISIANA SUGAR EXPERIMENT STATION, NEWORLEANS,LA.
I n a previous paper2 i t was shown t h a t a decrease in concentration of films of known concentration in laboratory-made sugars was responsible for an increase in deterioration when heavily inoculated with mold spores. The industrial application of this conclusion is determined by two important variable factors, namely, the concentration of the films surrounding the sugar crystals, and the degree of infection. Therefore, a further investigation of the influence of these factors was considered necessary. The method of procedure was identical with t h a t outlined in the previous article, except t h a t the incubation period was 5 . 5 mo. instead of one month. A series of sugars with films of known composition was made in the laboratory by coating large crystals of sterilized sugar with sterilized blackstrap molasses and 60" Brix sugar sirup in definite proportions and purging in the centrifugal, a method previously employed with success. Blackstrap molasses, 5 / 6 blackstrap C1/6 sirup, 4 / 6 blackstrap+2/6 sirup, and 3 / 6 blacksirup when arranged in order of increasing strap moisture ratio are designated as Concentrations A, B, C, and D, respectively. These sugars were inoculated with Aspergillus niger, Aspevgillus Sydowi Bainier and Penicillium expansum, a t the rate of 100,
+
Read before the Louisiana Section of the American Chemical Society, November 21, 1919. 2 THISJOURNAL, 12 (1920), 256.
455
1000,and 10,000spores per gram. At the end of 5 . 5 mos. incubation a t room temperature the contents of each flask were analyzed for sucrose by direct polarization and modified Clerget, and for reducing sugars and moisture. It has already been shown1 t h a t the most satisfactory criterion of deterioration of sugar is the gain in per cent of reducing sugars. I n order t o summarize the results as briefly as possible, there is given in Table I the incrkase over check of the averages of closely agreeing triplicate determinations of reducing sugars. The abbreviation M. R. stands for moisture ratio, which value is derived as follows: &I. R. = Moisture-. Asp. n, is the abbreviation for I O O - Polarization) Aspergillus niger, while Asp. S . B. and Pen. represent Aspergillus Sydowi Bainier, and Penicillium expansum.
TABLEI-SUMMARYSHOWING THE INFLUENCE OF AMOUNTOF MOLDIwOCULUM O N THE DETERIORATION OF SUGARS WITH FILMSOF KNOWN CONCENTRATION. INCREASE IN PER CENT REDUCING SUGARS OVER CHECK A M . R . = 0.14 * L _
CONCENTRATIONB C M . R . = 0.16 M.R. 0.18 c _ -
d
100
1000 10,000
- ----
--
7
D M. R. = 0.24 -_7
ci
d
:.
0.09 0.01 0.09 0.07 , . 0.10 0.10 o:oz 0102 1 : 0 . 0 5 0.04 o : i 2 0 . 2 2 0.17 0.04 0.18 0.18 0:04 0.21 0.11 0.03 0.12 0.11 0.27 0 . 3 1 0 . 2 8 0.12 0 . 2 7 0.28
I t will be seen from this table t h a t in every instance b u t one an increase in the number of spores per gram caused an increase in per cent of reducing sugars over check. This held true not only a t every concentration employed, varying in moisture ratio from 0.14 t o 0.24, but likewise for every organism used a t any single concentration. This fact is very significant and indicates conclusively t h a t a n increase in degree of inoculation of mold spores a t any definite concentration is responsible for a n increase in deterioration of sugar. This corroborates our previous work where solutions varying from I O t o 7 0 per cent were employed,2 as well as the results obtained in the experiment just c o n c l ~ d e d where ,~ a n inoculation of I O O , O O O spores per gram a t each of the above-mentioned concentrations was employed. A closer scrutiny of the results presented in Table I reveals the fact t h a t the increase over check of reducing sugars with an inoculation of I O O spores per gram is insignificant a t practically all concentrations. The same is true of an inoculation of 1000spores in the two higher concentrations, namely, A and B. This is of practical importance in defining the limits a t which deterioration occurs, since in plantation granulated sugars the moisture ratio may be said ordinarily t o be below 0.18. I t is generally considered t h a t good Cuban raw sugar likewise should have its moisture ratio below 0.25 t o 0.33. Thus, i t might be inferred from the foregoing d a t a t h a t where the moisture mold infection of less t h a n about ratio is below 0.18, 5 , 0 0 0 spores per gram would cause slight, if any, deterioration. As a rule we have rarely found sugars which had more than 2 5 0 mold spores per gram, alLouisiana Bulletin 166. J . Agr. Res., 18 (1920), 537. a THIS JOURNAL, LOC. cit. 1
2
456
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
though no quantitative survey has been carried out as exhaustively as might have been desirable. When the two lower concentrations C and D are considered, we find t h a t there is evidence of deteriorative activity with I O O spores per gram, while with more t h a n 1000 spores the deterioration is quite appreciable, It would appear, therefore, t h a t for safety (from the standpoint of mold infection) a sugar having a moisture ratio of 0.17 t o 0.18 would have t b contain less t h a n I O O mold spores per gram. On the other hand, a mold infection of more than 10,000spores per gram will cause a deterioration in sugars with moisture ratios varying from 0.14 t o 0.24. It may be noted in this connection t h a t in the previous investigation a n inoculation of I O O , O O O spores per gram was responsible in one month for a deterioration in sugars with moisture ratios varying from 0.08 t o 0 . 2 0 . An interesting fact which corroborates all our previous work with sugars, as well as solutions, is t h a t a t any definite concentration and with a n equal number of spores per gram A s p e r g i l l u s Sydowi Bainier is more effective t h a n P e n i c i l l i u m e x p a m u m , which in t u r n is more effective t h a n A s p e r g i l l u s niger in deteriorative activity. TABLE11-SUMMARY SHOWING THE INFLUENCE OF CONCENTRATION OF FILMON DETGRIORATION OF SUGARS BY MOLDS -Per cent Gain in Reducing Sugars over Check100 Spores 1000 Spores 10,000 Spores per G . per G. per G.
d
........
A 0.14 B . . . . . . . . 0.16
c . . . . . . . . 0.18
D . . . . . . . . 0.24
.. ..
.. ..
0:09 0101 0.09 0.07 0.10 0.10
m
,.
0.02 0.02 0.04 0.05 0 04 0 . 0 3 0.17 0.27 0.04 0.18 0.18 0 . 1 2
o:iz 0.22
0.21 0 12 0:3i 0.27
0.11 0 11 0:28 0.28
I n Table I1 is presented a summary of results so arranged as t o show the influence of concentration of film on the deterioration of sugars by molds. It must be stated a t the outset, however, t h a t where the increasing increments of moisture are so slight as in the present instance, and especially when dealing with the activity of microorganisms over such a long incubation period, i t is hardly t o be expected t h a t the differences will be very sharply defined. However, i t will be observed t h a t as a rule a n increase in moisture ratio (which actually signifies a decrease in concentration) is responsible for a n increase in deterioration with any single inoculation. I t is not necessary t o repeat here what was stated in the discussion of Table I concerning the limiting effects of concentration with any definite inoculum. Suffice it t o say t h a t this work fits in very closely with our preceding investigations and proves quite conclusively t h a t with a high mold infection, deterioration takes place in sugars with moisture ratios below 0.14, or, according t o the previous experiment, a t 0.08. This substantiates the claim previously made t h a t “the factor of safety for sugars well infected with fungi would appear t o be lower t h a n is generally supposed,” and defines more clearly what such limits must be. In other words, knowing the number of molds present in any sugar, i t may be predicted (from the standpoint of mold infection alone) what deterioration may be
Vol.
12,
No. 5
TABLE 111-CONPARISONIN CONTENT OF REDUCING SUGARS OF INOCULATED SUGARS (WITH FILMS OF CONCENTRATION D ) AFTER 1 AND 5.5 Mos. INCUBATION, RESPECTIVELY Gain Gain As9. over As$. over Check n. Check S. B. Check 0.23 0.44 0.21 1.10 0.87 0.23 0.53 0.30 1.46 1.23
Incubation After 1 mo.. After 5,s mo. Gain in reducing sugars, per cent ... 0.00
....... .....
0.09
..
0.36
..
Gain over
Pen. Check 0.77 0.87
0.54 0.64
0.10
..
expected in a storage period of about 5 mo. with a sugar of known moisture ratio. It is t o be assumed t h a t a t the present time sugars are not stored for such a long period of time, but t h e differences obtained upon a long incubation period are not so much greater as t o invalidate the above generalizations, as will be seen from Table 111, which gives a comparison in the reducing sugar content of inoculated sugars with films of Concentration D (moisture ratio = 0.24) after I and 5.5 mo., respectively. It will be readily seen t h a t the differences in incubation as represented by the gain in per cent of reducing sugars are indeed slight when compared with the initial gain over che,ck in one month. Next t o the elimination of deterioration, the most important commercial consideration is prediction of the keeping quality of a sugar. Table I V is a tentative plan based on the results obtained in all our invesiigations which will give some conception of the deterioration t o be expected from a definite number of molds in sugars of known moisture ratio. It must be clearly understood t h a t this plan is advanced with considerable diffidence, and t h a t its value rests on further verification. Furthermore, i t is of importance t o note t h a t in t h e above table mold infection only has been considered. We have data which are concerned with deterioration due t o bacterial infection and unquestionably the bacterial flora would seriously influence the deterioration of sugars as shown in the important researches of previous investigators. However, since individual molds, such as A s p e r g i l l u s Sydowi Bainier, P e n i c i l l i u m e x p a n s u m , and A s p e r g i l l u s niger, are vastly more efficient in their deteriorative activity than any bacteria t h a t have come t o our attention, and since the first-named mold is t o be found in practically all sugars, i t may be t h a t the above table will prove of some value t o those who are ready t o take cognizance of the molds which are undoubtedly causing large TABLE IV-DETERIORATIONTo BE EXPECTED FROM A DEFINITENUMBER OF
MOLDSI N
SUGARS OF
No. of mold spores p e r g . 0.08 0-100 100-1 000. ................. 1000-10,000 .............. 10,000-100,000 . . . . . . . . . . . . . Deterioration - No deterioration f Slight, if any deterioration
.....................
*
KNOWNMOISTURERATIO
0.14
-
+*
0.16
0.18
0.20 0.24
** +++ +++ +++
Over 0.24
+++
+
economic losses in the sugar industry. I n Table IV i t will be seen t h a t the facts previously discussed have been so arranged t h a t one may tell a t a glance what deterioration, if any, might be expected. It was not deemed necessary t o carry out the work in moisture ratios beyond 0.24, because i t is generally conceded t h a t sugars having a moisture ratio above 0.30 are
May, 1920
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
susceptible t o deterioration. Brownell Owen,2 and others have advanced much valuable evidence on this point. This paper may be said t o round out one phase of t h e problem of sugar deterioration, namely, t h a t concerned with the importance of mold infection, which we have carried through t o completion, from a survey of mold species in sugar and their deteriorative activities in sugars and solutions t o a study of t h e effect of varying t h e amount of inoculum and concentration o n deterioration. The writer wishes t o thank Messrs. D. F. Stanfill, Jr., and R. S. Hays for their help with t h e chemical analyses and t h e Station staff for their assistance, and is indebted t o Mr. W. L. Owen for his kindness in reading t h e manuscript. SUMMARY
I-An increase in number of mold spores inoculated into sugars (with films of varying concentration) is responsible for a n increase in deterioration. 2-A decrease in concentration of t h e films surrounding the sugar crystals is responsible for an increase in deterioration. 3-A table is presented showing t h e deterioration which may be expected from a definite number of molds in sugars of known moisture ratio. 4---At moisture ratios of less t h a n 0.18 there is little, if any, deterioration with a mold infection of less t h a n 5,000spores per gram. More than this number of spores induces deterioration. At moisture ratios above 0.18, deterioration occurs with upwards of IOO spores per gram. 5--At any definite concentration and with a n equal number of spores per gram Aspergillus Sydowi Bainier is more effective than Penicillium expansum or As*ergillus niger in its deteriorative activity. ACIDITY AND ACIDIMETRY OF SOILS.3 II-INVESTIGATION OF ACID SOILS BY MEANS OF THE HYDROGEN ELECTRODE By Henry G. Knight OKLAHOMA
AGRICULTURALAND M E C H A N I C A L COLLEGE, OKLAHOMA Received October 14, 1919
STILLWATER,
INTRODUCTION
Although the literature upon the subject of soil acidity is voluminous, t h e use of t h e hydrogen electrode in soil investigations has been rather limited. Gillespie4 made use of the hydrogen electrode for determining t h e hydrogen ion concentration of a mixture of soil with pure water; but, for reasons which will develop in the investigations given herewith, t h e presence of a conducting medium was found t o be desirable. Sharp and Hoagland5 studied t h e hydrogen 1
THISJ O U R N A L , 10 (1918), 178.
2
Louisiana Bulletin 162.
8 This is a thesis submitted t o the faculty of the University of Illinois in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Acknowledgment is made of many helpful suggestions and criticisms received from Prof. C. G. Hopkins and H. A. Noyes. 4 J. Wash. A c a d . Sci., 6 (1916), 7. 6 J . Agy. Res., I (1916), 124.
457
concentrations of suspensions of soils in pure water under various conditions, effects of natural salts and bases upon hydrogen ion concentrations of soil SUSpensions, and made titrations with various bases. The purpose of the present investigation is t o study: ( I ) t h e speed of reactions between neutral salt solutions and soils; ( 2 ) the speed of reactions in t h e presence of a base; (3) t h e change in hydrogen ion concentration with change of amount of base and with time, and the change in conductivity of soil solutions. APPARATUS
Preliminary experiments were conducted with a n apparatus similar t o t h a t described by Hildebrand,' and some experiments described elsewhere with soil solutions were carried out, but for use with solutions in contact with t h e soil i t was found t o be rather unsatisfactory. For all work reported, unless otherwise stated, a high-grade potentiometer (Leeds and Northrup, No. 28952) was used with a gas cell especially designed for t h e work. G A S CELL-Preliminary experiments showed t h a t for uniform results i t was necessary t o have a gas cell which could be agitated continuously, as apparently t h e agitation produced by t h e entering gas was not sufficient. After a number of trials the gas cell shown in Fig. I was designed for this work. It is cylindrical in shape, 3.3 cm. in diameter and 16 cm. in length,
n
lr I
t6 CU FIG. 1
the ends being rounded off. At one end an opening is provided of a size t o carry a No. 4 rubber stopper, through which pass t h e electrical connection a to t h e platinum plate b t o serve as t h e hydrogen electrode, t h e tube c for the ingress of hydrogen gas, and tube d for the outlet. Tubes c and d have capillary tubes sealed into the ends t o regulate t h e flow of hydrogen. To make connections with the calomel half cell a glass tube, g, is provided at the further end of t h e gas cell provided with a stopcock, f, and a constricted tip, h. This tube reaches t o within a few mm. of the bottom of the gas cell and as it did not readily clog with soil was found t o be very satisfactory. The gas cell was designed t o be of I O O cc. capacity and t o be filled half full of liquid, leaving room for 50 cc. of gas. The reason for this arrangement will develop later. The hydrogen electrode b is a rectangular piece of sheet platinum, 1.2 x 2.4 cm., with pieces of platinum wire welded t o each end, and is similar t o t h a t used by 1
J . A m . Chem. SOC.,85 (1913), 847.
