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 ENGINEERlNG C H E M I S T R Y
TABLE111-SOLUBILITY O F DIAMMONIUM PHO3PHATE -Grams Diammonium Phosphate--100 G. of Saturated Solution100 G. Water Temp. C. (1) (2) (3) (4) (5) ... 30.0 30.3 29.7 0 10 20 30 40 50
(in .. 70
38.3 40.7 42.2 44.4 47.0 48.8
5i.o
38.4 40.8 42.8 45.6 47.2 49.9
51.8
38.4 40.5 42.5 45.0 47.1 49.4
51.4
3k:6 40.8 42.9 45.0 47.2 49.3 51.4
62.8 69.0 75.2 81.8 89.2 97.3 106.0
SUMMARY
Solubility determinations made on the two commercially important phosphates of ammonia permit t h e derivation of the following solubility equations, representing the grams of the salt dissolved in I O O g. of the saturated solution between the temperature limits given: Solubility Monoammonium Phosphate 18.0 $- 0.455t. Solubility Diammonium 36.5 0.213t.
+
Phosphate
so goo
c. c.
IO0
c.
70’
C.
-
PEARL BARLEY: ITS MANUFACTURE AND COMPOSITION By J. A. LeClerc and C. D. Garby PLANTCHEMICAL LABORATORY, BUREAU OP CHEMISTRY, WASHINGTON, D . C. Received November 8, 1919
The barley crop of the United States approximates 200,000,000 bu. yearly, most of it being grown in North Dakota, California, Minnesota, South Dakota, Wisconsin, Kansas, and Iowa. The average annual yield per acre is about 2 5 bu. Heretofore fully onethird of the crop, or somewhat over 60,000,000 bu., has gone into malt for brewing and distilling, and a large amount is still malted for utilization in the manufacture of malt extract. About one-half of the crop is used directly as feed for animals, and from 2 t o 3 per cent, or approximately 4,000,000 or 5,000,ooo bu., is kept by the farmers for seed. This leaves a relatively small proportion of the entire crop (normally about 3,000,000 bu.) t o go directly into human food as barley flour or pot and pearl barley. Except during t h e war, when a large portion of the crop was milled into a flour which was mixed with wheat flour and used for baking, barley has for the most part been consumed b y man in the form of pearl or pot barley. I n this form i t has, of course, been used for many decades in Europe, particularly in Scotland where pot barley has met with special favor. About a score of manufacturers in this country are now engaged in making pearl barley, t h e total output of which before the war was ~ o o , o o o loo-lb. sacks. The present paper contains the results of a study of the method of manufacture of pearl barley and of the chemical composition of the various products of the pearling operations carried out by the Plant Chemical Laboratory. P E A R L A N D POT B A R L E Y
According t o McGill,‘ the reduction in weight in producing pot barleys is 46 per cent. Such barley contains from 0.89 t o 2.44 per cent of ash. The loss in making pearl barley is greater, as is evident from the 1
Lab. Inland Rev. Dept., Ottawa, Canada, Bulletin 329.
451
fact t h a t McGill finds t h a t pearl barley contains from 0.58 t o 1.27 per cent ash. Tibbles’ states t h a t Scotch barley is not decorticated as extensively as pearl barley. Church2 states t h a t from I O O lbs. of barley only 63 lbs. of pot barley, or about 32 lbs. of pearl barley, are obtained. Doubtless this pearl barley is the product resembling the fifth pearl barley of commerce. Gill3 states t h a t when the integuments of the barley are removed and the product rounded and polished the result is pearl barley. Sometimes in the process of manufacturing pearl barley, sulfur dioxide is used t o whiten the final product, and talc or similar substances are added t o brighten and give i t a “pearl-like” appearance. The amount of insoluble ash in normal pearl barley, which has not been subjected t o the treatment with talc or other mineral spbstances, is less t h a n 0.10 per cent. According t o Liverage and Hawley4 any sample of pearl barley containing a greater quantity of insoluble ash should be regarded as adulterated with mineral facing. Pluecker and Flebbs5 have shown t h a t the use of sulfur or talc is not for the purpose of preventing the growth of microorganisms, as has been claimed by some manufacturers, but is simply a commercial practice. MANUFACTURE
The various steps t o which barley is subjected in the pearling process are indicated in Fig. I. The barley as first received is passed into storage bins from which i t travels t o automatic scales. The weighed grain is sent t o the separator where i t is partially cleaned by screens. From the separator i t goes t o the reel,
Grader
FIG. DIAGRAM SHOWING BARLEY PEARLING PROCESS
which cleans i t more thoroughly. The cleaning is completed b y sieves and aspirators, after which the barley is ready for the pearling process. The grain “Poods, Their Origin and Manufacture,” p. 471. 2 “Food,” p. 74. s “Bread Maker,” p. 75. 4 J. SOC.Chem. Ind., 34 (1915). 203. 6 Z . N a h r . Genussm.;28 (19141, 28 1
is carried from the cleaning dcviccs, which iliffer in various mills, to the small bin over the first penrler. The pearling machine used in the preparzition of pearl barley generally consists of a large, vertical, cylindrical abrasive stone surrounded by a metal sieve, and resembles an ortlinary grindstone in shape and position. The whole is enclosed in a dustproof metal jacket. The stone, usually oi corundum, carhorundum, or emery, may be as much as 4 Et. in diameter, and is made to revolve from 300 to 400 times per minute. The sieve surrounding this stone revolves about one-tenth as fast in the opposite direction. The barlcy, introduced automatically from a small bin or hopper, is subjected to a scouring action between the stone and the sieve. This abrasion continues fur about z min., and the finer dust particles produced are removed from the enclosing jacket by means of dust collectors. The partly pearled barley and offal are then ejected, and a new charge of clean barley introduced. The entire process is automatic and practically continuous.
particles. The pearling is gcnerally repeated irom 4 t o 6 times in order to rcniove by attrition all the outer coats of the barley grain.
After passing through the third process the partly pearled barley is oEten sent to a grader where it i s assorted (Fig. I ) . The large kernels are subjected t o further attrition, thus producing a pearl barley of special type, the grain of which is rather large and we11 rounded. The smaller broken particles are collected and ordinarily used for feed. If the pearling process is stopped a t the stage where only the outer cuticle is removed a “pot” barley (French, Orbe Mondd) results. This is sonietimes called Scotch barley, and is also known by various trade names. When the attrition is carried on stili further a smaller type of pearl barley, which is generally separated into grades according to size, is produced. The different pot and pearl barleys and oRal are shown in Fig. 2 . EXPERIMENTAL WORK
SAMPLES-Two Sets of samples were obtained from a ’ large cereal factory, one in 1916 and the othe I n each case samples of the original bar1 as of the products resulting from each cess, were collected. That is, the s the original barley, the pearled or part and the offal from each of the 6 pearling operations. METHODS OF AXALYSIS-After grinding the saniples so that they would pass through at least a I-mm. sieve, they were analyzed for moisture, ash, protein, fat, and
v
9G Fie 2
From the first pearler the mixture of offal and barley is sent t o a reel which removes the offal or husk. From the reel the barley enters an sspirator where the remaining fine particles are removed. After cooling, the barley is ready for the second pearling. The second opcration, which is identical in process with the first, remoses the ncst remaining layer of the grain, and the product thus obtained is lilcewise sent to a reel for the separation of the offal and the dust
BF
e
k
.E
E 8
May,
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
1920
fiber, according t o the methods of the Association of Official Agricultural Chemists. The constituents of the ash were determined as follows: P205 and KzO according t o the official methods of the Association of
453
TABLE 111-PERCENTAGECOMPOSITION O N DRY BASIS OF PEARLBARLEY AND
OFFAL(6 Operations) CONSTITUENTS Protein (N X Ash 6.25) F a t Fiber PzOs KzO 2.82 13.19 2.09 5.08 1.02 0.66 6.89 10.56 2.77 23.74 0.97 1.12 2.17 12.94 2.02 2.36 1.07 0.59 5.13 19.56 6.48 9.25 1.92 1.15 1.80 12.56 1.47 1.37 0.94 0.50 3.93 16.38 4.92 4.81 1 . 8 1 1 . 0 3 1.45 10.25 1.19 0.91 0.81 0.41 2.68 14.38 2.58 2.06 1.37 0 . 7 0 1.20 10.50 0.91 0.73 0.68 0.34 2.13 13.45 2.04 1.35 1.14 0.58 1.06 10.37 0.94 0.58 0.62 0.32 1.67 12.50 1.67 1.22 1 . 0 0 0.47 0.98 9.44 0.89 0.44 0.56 0.30
W t per 1000 P C. KerDESCRIPTION No. nels. G. Original barley.. 17575 42.50 1st offal.. 17577 17576 39.66 1st pearling., 2nd offal.. . . . . . 17579 2nd pearling.. 17578 34.10 3rd offal........ 17581 3rd pearling.. 17580 30.40 4th offal ........ 17583 4th pearling., 17582 24.52 5th offal . . . . . . . . 17585 17584 20.13 5th pearling.. 17585-Y 6th offal.. .. 17585-x14.25 6th pearling.
......
... .. .. . ..
9
CaO 0.062 0.095 0.048 0.097 0.043 0.076 0.035 0.052 0.033 0.047 0.030 0.038 0.035
through 5 operations. Tables I11 and I V (P. C. 1 7 j 7 j and 17585) give similar results on products obtained from 6 pearling operations. These results are also graphically represented by the curves shown in Figs. 3, 4, and 5 .
FIG.
5--PERCENTAGE LOSS O F CONSTITUENTS DURING PEARLlNG PROCESS
Official Agricultural Chemists; the silica also by the official method, except t h a t it was not separated from carbon and sand, the amounts of which were so small as t o be negligible. The calcium and magnesium were determined according t o the McCrudden method,l with slight change in t h a t it was not found necessary t o boil the calcium solution during any part of the determination. TABLE I-PERCENTAGE COMPOSITION ON DRY BASIS OF PEARL BARLEY AND
wt.
Original barley 1st offal 1st pearling 2nd offal 2nd pearling 3rd offal 3rd pearling 4th offal 4th pearling 5th offal 5th pearling
OFFAL (5 Operations) Constituents-
=; N
.....
..... .....
CaO 24.2 45.1 58.0 69.3 77.4 80.6
DISCUSSION O F RESULTS-From t h e chemical and physical study of t h e products of pearling, i t is obvious t h a t the offal resulting from the first pearling process (P. C. 18410 and 17577) is composed almost entirely of the hulls of the barley (Fig. 2 ) . This offal has relatively little food value for man, both because of its extremely high content of fibrous material and of silica (23.6 per cent on a n average for fiber and 4.1 per cent for t h e silica), and because of its physical
TABLE V-PERCENTAGE OF MINERALCONSTITUENTS IN ASH 18408 28.32 2.81 12.06 2.22 5.89 0.962 0.654 0.074 0.265 0.785 0.284 4.080 18410 7.25 10.37 3.45 0.221 0.257 18411 24.37 2.15 12.56 2.07 0 438 1.470 18413 5.05 18.00 6.43 0.173 0.138 18414 21.44 1.80 11.69 1.73 0.448 0.259 3.73 17.12 4.98 18416 0.146 0.069 18417 18 72 1.44 10.75 1.26 0.282 0,210 18419 2.42 13.81 2.43 0.108 0.038 16.18 1.15 10.13 1.16 1.86 12.31 1.90 1 15 0 9 2 3 0 4 9 6 0 0 6 3 0.186 0.098 13.20 0.96 9.69 1.02 0 6 5 0 5 0 6 0 2760039 0,102 0.029
ANALYSIS-AShas been stated already, from 4 t o 6 pearling operations are necessary t o secure a well-rounded, white, pearl barley. Tables I and I1 RESULTS OF
TABLE 11-Losses DUE TO PEARLING (5 Operations) Calculated from Weights T a k e n at the iMill1 Wt. per 1000 Ker- * Constituents (Per cent) DESCRIP- P. C. nels ProTION No. G. Ash tein F a t Fiber PzOd Kz0 CaO Mg.0 Si02 1st pearling 18411 11.5 30.0 8.0 17.6 58.6 9 . 4 25.2 29.7 26.0 71.1 2ndpearling18414 22.1 49.2 25.0 39.7 77.9 28.7 40.4 45.8 49.0 86.3 3rdpearling 18417 30.9 63.6 38.5 60.1 8 7 . 8 46.4 5 7 . 6 50.0 61.9 93.9 4thpearling 18420 38.1 74.5 48.3 67.8 92.1 60.9 67.9 56.7 78.5 97.0 5thpearling 18421 48.1 81.7 58.7 76.1 9 4 . 3 72.6 78.1 73.0 8 0 . 0 98.3 Calculated from Weight per 1000 Kernels 1st pearling 13.7 34.1 1 0 . 3 19.8 59.8 12.0 27.2 3 1 . 1 28.3 71.8 Zndpearling 24.3 50.6 26.8 40.9 78.6 30.7 42.0 45.0 5 0 . 5 86.7 3rdpearling 34.2 6 5 . 3 41.2 62.4 88.3 48.7 5 9 . 5 5 2 . 7 63.4 92.8 4thpearling 42.8 7 6 . 4 51.9 70.0 92.7 64.9 70.2 59.4 76.6 97.2 5thpearling 53.0 83.5 62.7 78.2 94.8 75.3 80.2 75.7 81.9 98.2 1 A complete charge from one of the pearling machines, consisting of from 50 t o 100 lbs. of mixed barley and offal, was secured from each pearling operation. The pearl barley was separated from the offal, and the percentage loss calculated.
... ...
... ... ...
(P. C. 18408 and 18422) show the results of the analysis of pearl barley and the products of pearling obtained 1
TABLEIV-LOSSES DUE TO PEARLING (6 Operations) Calculated from Weight - -be7 1000 Kernels W t . per , Constituents (Per cent)--1000 Protein Kernels (N X DESCRIPTION G. Ash 6.25) F a t Fiber PzOa KaO 2.2 1 7 . 0 1st pearling.. 6.7 28.0 8.5 9 . 6 56.7 48.9 23.7 43.5 78.4 26.2 39.8 2nd pearling.. ..... 1 9 . 8 55.3 87.2 43.4 63.1 4 4 . 6 5 9 . 3 3rd ~ e a r l i n z . .. . . . . 28.4 75.5 54.1 74.9 91.7 61.7 7 0 . 3 4th pearling.. 42.3 71.4 77.2 94.6 78.7 82.2 62.7 5th pearling.. . . . . . 52.7 88.4 74.4 85.7 97.1 81.8 85.1 6th pearling.. 66.5
J . B i d . Chem., 7 (1909), 98; 10 (1911), 187.
DESCRIPTION Original barley.. 1st offal..
Total Ash
.... 2.82 2.81
.... ........
1st pearling. 2nd offal
........... ......
2nd pearling..
6.89 7.25 2.17 2.15 5.13 5.05 1.80 1.80 3.93 3.73 1.45 1.44 2.68 2.42 1.20 1.15 2.13 1.86 1.06 0.96 1.67
.......... ...... 4th offal.. .......... 4th pearling., ...... 5th offal.. .......... 5th pearling.. ...... 6th offal.. .......... ... 6th pearling., ...... 0.98 ...
3rd offal..
3rd pearling.,
PzOb 36.2 34.2 14.1 11.6 49.3 45.8 37.4 32.3 52.2 49.2 46.1 45.3 56.0 51.6 51.1 48.8 56.6 53.6 53.5 49.6 58.5 52.7 59.9
...
57.1
...
Constituents KzO CaO MgO 23.4 2.2 23.3 2.6 9.4 16.2 1.4 ... 16.1 1.6 3.9 ... 27.2 2.2 25.7 2.8 10.3 22.4 1.9 23.4 2.3 8.7 27.8 2.4 2.9 9.6 27.8 26.2 1.9 ... 26.2 2.5 12.0 28.4 2.4 27.7 3.7 10.1 26.1 1.9 ... 25.2 2.9 11.6 28.3 2.7 ... 29.6 4.6 9.4 2.2 27.2 26.7 3.3 10.0 30.2 2.8 ... 28.7 4.0 10.6 28.1 2.3
...
... ...
...
...
b..
30.6
...
..
3.6
*.
... ...
... ...
Si02
... ...
27.9 56.3
... ... 29.1 11.8
... ... 6.9 7.7
...
4.8
...
8.7
...
3.4
... ...
5.2
3.0
... ... ... ..
characteristics. There is no doubt, however, b u t t h a t there is some value as animal feed in the offal, even from t h e first pearling, because i t contains a n average of approximately 10.50 per cent of protein ( N X 6.25) and an average of 3.11 per cent fat. The offal from the second-pearling (P. C. 18413 and 17579) contains over 18.75 per cent protein, 6.45 per cent fat, 9.70 per cent of fiber, and less than 1 . j per cent
454
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
SiOz. The high content of P& (over 3 2 per cent of the ash (Table V)), together with the high percentage of fat and protein, indicates t h a t this offal is made up t o a marked degree of the aleurone layer, or the socalled protein layer, a substance rich in protein, fat, and mineral ingredients. The second offal contains less than half as much fiber and about one-third as much SiOz as does the first offal. I n addition, i t contains twice as much fat and almost twice as much protein. A significant fact is the difference in ash constituents. The second-pearling off a1 contains less ash t h a n does the first offal, but a t the same time i t contains twice as much Pz05, besides being much poorerinsilica. All this shows t h a t while a t least two processes of pearling are essential for the production of an edible product, even this second pearling operation removes an appreciable amount of food constituents. The third offal is also rich in protein, fat, ash, and Pz05,as well as in fiber. T h a t this fiber is composed chiefly of the bran coating, however, and not of t h e hulls may be assumed from the relatively low silica content, and from the high Pzo5 content of t h e ash of this Droduct. The edible product obtained from the third pearling operation, or the pot barley, is almost entirely free from the aleurone layer, as is evident from the low percentageoffat,fiber, andash(Nos. 18417 and 17580in Tables I and 111). The fourth and fifth pot barleys are not only whiter, but are practically free from all bran material. They are still poorer in fat, fiber, and minerals than the pot barley from the third operation. The fifth pearl barley contains about one per cent each of ash and fat, and 0.6 per cent fiber. The ash contains a very high amount of Pz06 and a aery low amount of S O z . the fourth offal contains about 2.5 per cent each of ash and fat, about 2.35 per cent nitrogen, and 2 per cent fiber, while the fifth offal still has about 2 per cent ash, nitrogen, and fat, and about 1 . 2 5 per cent fiber. From Table V i t is evident t h a t the amount of Si02 in the ash in the first offal is over 56 per cent, and t h a t i t decreases rapidly, the off a1 after the second operation containing but a small amount of silica. The ash of the third offal is composed of only about 8 per cent SiOz, while t h a t of the fifth contains only 5 per cent. gradually On the other hand, the percentage of P z O ~ increases from 11 per cent in the first offal t o over 50 per cent in the fifth. The high Pzo5 content and the low percentage of Si02 may well be considered a criterion of the quality of the product. Tables I and 111 also show t h a t the second-process pot barley (P. C. 18414 and 17578))which is practically free from hulls and constitutes the first product of t h e pearling process fit for human consumption, has, on the water-free basis, the following average percentage composition :
......................... .................... ......................... ........................
Ash, Nitrogen. Fat. Fiber P206. KzO CaO. ........................ MgO ........................ Si02 .........................
........................ .........................
1.80 1.94 1.60 1.52 0.91
0.50 0.048 0.17
0.138
1701.
12,
NO. j
This is essentially the same as the composition of hull-less barley. With each process of pearling the percentage of nitrogen, fat, fiber, and the ash constituents gradually decreases. The fifth-pearling barley contains in per cent approximately:
.......................... 1.00 ................... 1 . 6 0 .......................... 1 . 0 0 ........................ 0.60 ......................... 0 . 5 6 ......................... ....................... 00 .. 30 03 5 ........................ 0 . 1 0
Ash Nitrogen.. Fat Fiber PzOs KzO CaO.. MgO SlOz
.........................
0.03
Table VI shows how regularly the weights of the barley and of the food constituents are distributed as the result of the successive operations in the making of pearl barley. TABLE VI-APPROXIMATE LOSSES D U E
TO T H E VARIOUS PEARLING OPERATIONS ~~
PERCENT Loss IN 1st 2nd Weightper 1OOOkernels.. 10 22 31 50 Mineral ingredients Nitrogen 9 25 Fat 15 41 57 78 Fiber 7 28 PsO5 22 40 Kz0 27 45 CaO 28 50 MgO 72 86 SiOz
...... ............... .................... .................. ................... ...................
................... .................. ...................
PEARLING3rd 4th 5th 31 42 53 64 76 83 43 53 62 60 72 78 88 91 94 45 62 73 57 70 78 55 64 76 63 76 82 93 97 98
6th 66 88 74 85 97 83 85 80
.. ..
Difference between 2nd and 6th Pearlings 44 38 49 44 19 55 45 35 32 12
Assuming t h a t 5,000,000 bu. of barley are now being yearly converted into pearl barley, the figures given in Table VI1 represent the weight of barley material and of the food constituents removed as the results of the two essential pearling operations and of the four subsequent processes. These figures mean t h a t if all these 5 , 0 0 0 , 0 0 0 bu. of barley were passed through the 6 operations of the pearl barley process, as against the 2 operations necessary t o make pot barley, 52,000 tons of barley material, containing over 6 , 7 0 0 tons of protein, over 1,000 tons of fat, and 1,100 tons of mineral ingredients, would be removed. TABLE VII-APPROXIMATEAMOUNT01”BARLEY AND OF BARLEYCONSTITUENTS REMOVED BY PEARLING (IN TONS) Diff in ~~~. Weight between 2nd and 6th Weight in Original -----Weight in Pearlings---PearlBarley 1st 2nd 3rd 4th 5th 6th ings 120,000 12,000 26,400 37,200 50,400 63,600 79,200 52,800 ~~~
LOSSIN
’
......
Weight Mineral ingredients Protein.. . . . Fat Fiber P20a . . . . . . . . KeO ........ CaO MgO SIOE
......... .......
........ ....... ........
3,000 13,650 2,330 5,920 1,068 702 74 288 847
930 1 5 0 0 1 920 1,229 3:412 5:896 955 1374 350 3,374 4,620 5:215 299 481 75 281 400 154 41 20 33 80 144 181 593 707 765
2 280 2 490 2 640 7:234 8,’463 10,’159 1677 1817 1979 5:385 5:563 5:740 886 662 780 597 491 547 59 56 47 220 236 798 806
... ...
1,140 6,747 1,025 1,124 587 316 26 92 100
The figures in Table V show, moreover, t h a t the first 2 pearlings are sufficient t o remove practically all of the hull- and silica-containing portions of the barley, or the portions of the barley which are recognized as being unfit for human food. This is evident from the fact t h a t 78 per cent of the fiber and over 8 5 per cent of the silica are removed in the course of these first 2 pearling operations. It is interesting t o observe t h a t the offal from the sixth pearling has essentially the same composition as the pot barley resulting from the second pearling process (Table 111, P. C. Nos. 17585-y and 17578). This indicates t h a t the offal from the sixth pearling might properly be used as a barley flour.
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 E N G I N E E R I N G 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
