734 ’
Vol. 16, No. 7
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Corn sta1k Sir u p I n vest i gat i on
s1I2
By J. J. Willaman, G. 0.Burr, and F. R. Davison DIVISION O F AGRICULTURAL BIOCHEMISTRY, UNIVERSITY O F MINNESOTA, ST. PAUL, MI“.
ROM the time of the accomplished in a plateThe possibility of manufacturing sirup from sweet cornstalks as Aztecs up to the presand-frame filter press, with a cannery by-product has been inoestigated for two seasons under ent many attempts leaves 16 inches square. Minnesota conditions. Fiue varieties of sweet corn and two of field have been made to develop Usually only five leaves corn were used. The density of the juice at the canning stage of the a sugar industry with cornwere used. The press was ears is from 9 to 11 Brix: if the stalks are allowed to stand in the stalks as the raw material. fed either by a small rotary fieldfrom I O to 20 days after remooal of the ears, the density increases An interesting review of the pump or by a centrifugal. to a maximum, which may be 13”. l e o , or eoen 17“ Brix-these trade in corn sugar in coloDuring the first season an facts corroborating the claims in Stewart’s patent covering this field nial days is given by Collier open evaporator was used, treatment. The proper stage for sirup-making is at this period of in his book on sorghum consisting of a trough 1foot maximum density, both because of yield and of quality of juice. A sugar.3 H e c o n s i d e r e d wide and 8 feet long, lined new purity quotient, solids-ouer-Brix in thejuice, has been used as an maize stalks to be a very with tinned copper, and index of juice quality. promising material for sugar provided with steam pipes A one-line cannery has auailable about 500 acres of stalks, or manufacture, but inferior to on the bottom. Fresh juice 4000 tons a year, which would gioe about 1100 gallons of sirup per sorghum. During the last was admitted a t one end, day, or 38,000 per season. thirty years reports from and the finished sirup was Cornstalk sirup should be manufactured by essentially the same various parts of the world con t i n u ousl y withdrawn process as sorghum sirup, using controlled defecation, filtration, and have been published on the from the other end, a thervacuum euaporation. A careful use of the by-products, bagasse and crystallized sugar obtainmometer being used to inleaoes, would be necessary in commercial practice. Cornstalk sirup able from cornstalk^.^ The dicate the density of the is clear, reddish amber in color, with a pleasant flaoor. I t is not a g e n e r a 1 conclusion from sirup. Appropriate pumps table sirup, but is an excellent coolphg sirup, rivaling the best grades these reports is that sugar and storage tanks and a of sorghum and of molasses. can be obtained, but that it l a b o r a t o r y f o r making varies considerably from day chemical a n a l y s e s comto day and from one period of maturity to another, and that pleted the outfit. I n 1922 a glass-lined vacuum evaporator, the yield is low, due to low purity of the juice. As a source of with an evaporating capacity of 7 gallons of water per hour, sirup, however, the cornstalk has been given very little atten- was used. Density was measured by Brix hydrometers, and tion. The writers have met several people who made sirup in a total solids by an Abbe refractometer. The purity yuotient used here is the total solids, as detersmall way some years ago, but they have been unable to find any published reports of sirup investigations except a casual one mined by the Abbe refractometer, divided by the degrees in a report of the National Academy of Science.6 In 1921 the Brix. The former instrument has frequently been shown to Minnesota State Canners’ Association6 induced the writers give an accurate estimation of the total solids in plant ex, ~ ~ the ~ Brix reading usually gives results that are to undertake a study of the sirup-making possibilifies of sweet t r a c t ~while cornstalks as a cannery by-product. This paper constitutes a too high. This difference is due to the fact that the index of brief report of these investigations, including only the study refraction averages about the same for sugars, minerals, and of the manufacture of the sirup.7 organic acids, especially such of those substances as are found in plant juices, while the specific gravity is much higher EQUIPMENT AND METHODS for each unit of mineral substances in solution than for the The stalks were pressed in a 3-roll mill, the rolls of which sugars. Thus, as the ratio of sugars to nonsugars increases, were 12 by 15 inches, and the capacity about 1 ton of cane the index of refraction does not change appreciably, but the per hour. Two 100-gallon galvanized-iron tanks with steam specific gravity becomes relatively lower. Therefore, the coils in the bottom served as defecators. Filtration was less the difference between the Brix reading and the refractometer total solids, the greater is the total sugar purity. 1 Presented before the Division of Sugar Chemistry a t the 66th Meeting The color values are comparable only among themselves, of the American Chemical Society, Milwaukee, Wis., September 10 t o 14, all the samples being segregated into six groups, No. 1 being 1923. the lightest, and being equivalent to about No. 6 on the scale 2 Published with the approval of the Director as Paper No. 413, Journal used for sirups.”J Series, Minnesota Agricultural Experiment Station. 8 “Sorghum: Its Culture and Manufacture,” Cincinnati, 1884. The flavor ratings were established by placing the samples 4 Stewart, U.S. Patents 811,523 (January 30,1906), 1,018,994 (February in three groups, No. 1 being the best. Three judges agreed 27, 1912); Doby, Chem. Z t g . , 34, 1330 (1910); Vilmorin and Levallois, on the classifications. Bull SOC. chim., 13, 294 (1912); Prinsen-Geerligs, 8th Intern. Cong. A p p l . Chem.,“, 60 (1912); Strohmer.Ibid., 27,60 (1912); Marx, Arch. Suikerind.. PROCESS FOR MAKING EXPERIMENTAL LOTSOF SIRUP a0, 1131 (1912); Blackshaw, S. African J . S c i . , 8 , 269 (1912); 9, 42 (1912); Clark, U. S. Debt. A g v . , Bur. Plant Ind., Circ. i l l A (1913): Bohle, Deut The clean stalks, with ears, leaves, and tassels removed, Zuckerznd., 39, 538 (1914); Boyer, Sucre ind. colon., 49, 226, 252, 209, 343, were milled once. It was found that enough juice could not 392 (1914); Vieillard, Bull. ugr. inst. scz. Saignon, 2 , 106 (1920); Semichon, be obtained by a second milling to pay for the trouble, and A n n . s a . agron., 37, 173 (1920). 6 Report on Sorghum Sugar Industry, Washington, 1883, p. 152. any difference in quality of juice due to heavier pressing in 6 Frank Rabak, of the Bureau of Plant Industry, first called the attention commercial mills was taken care of in the analytical samples of C . D. Geidel, of the Minnesota State Canners’ Laboratory, to the sirup of juice, which were milled twice.’ From 15 to 30 gallons of possibilities of sweet cornstalks, and the latter then brought the proposition
F
O
O
to the present writers. 1 A complete record of the investigations will appear as Bulletin 207 of the Minnesota Agricultural Experiment Station.
Browne, “Handbook of Sugar Analysis,” New York, 1912.
* Gortner and Hoffman, Bot. Gas., 74, 308 (1922). 10
Wiley,
U.S.Degt. Agr., Bur. Chem., Bull. 93 (1905).
INDUSTRIAL A N D ENGINEERING CHE14fISTRY
July,r 1924
juice were used for a single lot of sirup. Frequently a larger batch was milled, and then aliquoted for different treatments. The juice was heated to boiling, the scum allowed to form, and the latter removed by skimming. The juice was treated, if desired, with lime, kieselguhr, and carbon, and filtered. +Sometimes the carbon was added after filtration, and a second filtration made. The clarified juice was then ready for evaporation. Only the data for 1922 are shown, when the vacuum evaporator was used, since the data for these samples are much more complete, and since they represent commercial practice better than those obtained by open evaporation. The
finishing point of the sirups was judged by the refractometer, from 73 to 76 per cent of solids being desired.
DISCUSSION OF RESULTS Many modifications of this outline of the process were followed. The results are given in Table I. The data include the condition and treatment of the cane before milling; the extraction of the clean cane in per cent; the polarization of a normal solution of the juice; the degrees Brix, the refractometer total solids, and the acidity (cc. 0.1 N alkali per 100 cc.) of the juice; the treatment with kieselguhr and
TABLE I-ANALYSES OF S I R U P S , Days since Canning Ears On Stage or Off when when Samcut Dale c u t ple
0
8-15 8-23 8-28
8 13
Off Off
39 26
8-3 1 8-17
16b 0
On
8-18
27
0
Milled fresh 34" Milled fresh 37 Milled fresh 31
On
24 32 37
EX-
trac-
FIELD tion TREATMENT %
Milled fresh 50 Stacked without leaves 30 2 days Stacked without leaves 28 3 days
On
On
On Off Off
Milled fresh 43 Milled fresh 48 Milled fresh 42
146 1
On
8-21
1
On
30
8-2L
3
Off
31
8-22
2
Off
Milled fresh Stacked without leaves 2 days Stacked without leaves 4 days Shocked with leaves 2 days Shocked with leaves 4 days
25 33 34
8-17 8-24 &2S
0
38 28
8-30 8-19
29
8-26
35
8-2fi
36
41
9-1 8-3 R 9-5
40 46
8 9
1 2
8 0 6
On
I .
.. .. ,. 2.7
35
18.5
12.0
..
15.0
13.8
..
20.0
0.5 0.5 0.5
' Brix
yo
=S
BRIX
Color Flavor Juice
85.0 73.4 70.6 74.8 74.4
6 6 4 6 6
1 1 9a:o 1 100.0 1 1 95.0
loo Sirup
1
0.5
7i:3 71.1 75.5 76.6
7.5
1
0.5
75.5
73.4
4
1
..
97.2
11.0
1
0.5
81.1 7 8 . 5
4
1
..
97.0
Crosby, Plol 1 11.1 15.0 6.0 12.3 l2:l 31.6 8.0 13.3 13.0 ( a ) 15.0 (b) 6 . 0 11.5 1 1 . 4 20.5 12.5
1 1 1 1 1
0.5 1.0 0.5 0.5 0.5
74.9 74.3 74.0 72.8 76.2
73.2 73.1 73.0 71.5 73.2
6
5 2 4 4
1 1 1 1 2
98:3 97.8
1 1
0 0.5
73.8 77.7
72.5 75.9
3 6
2 1
0 0.5
76.1 74.6
74.3 72.7
3 5
2 2
0
..
12.9
..
14.0
{;I
7'':
99.0
.. ..
98:s 99.3 99.1 97.2
97.8 98.5 98.6 98.2 96.0 98.2 97.7
35
..
11.7
..
15.0
(a) 14.0 ( b ) 10.0
1 1
32
..
12.8
..
16.4
(a) 14.5 (b) 9 . 0
1
0
74.7 76.2
73.5 74.8
3 5
2
..
13.7
13.8
20.0
( a ) 12.0
1 1
0 0 1.0
75.4 75.3 76.5
74.4 74.3 75.1
3 4 4
2 2 2
100.0
(c)
98.7 98.7 98.2
1 1
0.5 0.5
8 2 . 8 78.4 7 7 . 2 73.2
5 4
2 2
94.7
94.7 94.7
50
( b ) 11.5 7.4 Crosby, Plot 2 10.6 18.5 ( a ) 5 . 0 (b) 7.5
1
2
2
..
97.7 97.3 98.6 98.3
11.7
21.5
6.0
1
0.5
75.3
72.0
4
2
95.8
95.6
7.6
1 3 . 8 13.4
21.5
7.0
1
0.5
76.3
74.8
4
97.0
98.1
4.5 7.2
Stowell's Euernreen 11.4 10.2 19.5 8.0 14.3 13.3 25.5 ( a ) 21.0
1
1 1 1 1
0.5 0.5 0.5 0.5
78.4 7 2 . 0 74.4 69.8 79.0 7 4 . 4 8 0 . 7 75.8
1 1 2 1
3 3
89.6 93.0 98.7
91.9 93.8 94.0 94.0
Off
Milled fresh 38 Milled fresh 42
On Off
9-4
0
On
47
9-6
0
On
42
9-2
0
On
45
9-4
0
On
48
9-6
0
On
Milled fresh Stacked without leaves 2 days Stacked without leaves 4 days Stacked without leaves 6 days Shocked with leaves 3 days Shocked with leaves 5 days Shocked with leaves 7 days
...
On
off
.
11.2
12.2
39
8.6
14.3
13.4
27.5
(b) 6 . 0 6.5
39
5.4
12.6
11.4
23.5
8.0
1
0.5
80.6
73.8
1
3
90.5
91.5
39
5.5
15.2
12.0
22.0
6.3
1
0.5
79.4
72.9
1
3
91.0
92.0
41
6.1
13.8
12.4
21.5
8.0
1
0.5
79.2
73.0
1
3
90.0
92.2
42
5.7
12.6
11.3
24.0
8.5
1
0.5
79.4
72.0
1
3
89.6
90.8
39
6.7
13.3
11.6
26.0
10.5
1
0.5
78.5
71.2
1
3
97.3
90.6
30
7.8.
16.7
15.8
49.0
..
..
..
..
94.6
..
13.4 13.3
Country Gentlemen 15.0 10.5 13.2 12.7 18.0 5.5
1 1
0.5 0.5
74.5 75.6
72.0 72.3
2 5
2 2
98.6 95.6
96.6 95.6
14.5
13.3
1
0.5
77.8
73.4
5
2
91.8
94.5
5.6 Milled fresh 34 5.5 Milled fresh 32 Stacked On without 5.3 leaves 22 3 days b Mill rolls set too far apart for high extraction. 0 4 0
11.3
2 1 1
%
Refractometer Solids
Off
44
9-7 9-8 9-8
11.9
31:O 29.0
%
Carbon
..
Off On
(I
3.7
Minnesota 19 0
13:8 17.0
Kiesel guhr
Stacked without leaves 50 2 days Milled fresh 40
10 0
51
8:4
Final cc. No. 13 7.0 19.5 (a) 20.0 (b) 9 . 0 7.0
9.4 14.1 17.0
1922
TREATMENT -----SIRUP--
Milled fresh 45
9-9 9-2
50
RefracPotometer larizaSolids Initial tion O Brix % Cc.
..
CROP OF
-ACIDITY-
Off
52 43
49
32
-JUICE--
735
24.5
Ears in hard dent stage.
6.5
..
3 3
736
I N D CSTRIAL AND Eh-GINEERING CHEMISTRY
with decolorizing carbon; the density, color, and flavor of the sirup; and the purity quotient of both juice and sirup, obtained by dividing the total solids by the degrees Brix. Each factor will be discussed separately. VARIETYOF CORK-A~I the varieties examined develop a fairly satisfactory sugar content in the juice, especially when allowed to remain in the field after removing the ears (the so-, called Stewart process1‘). The usual density of juice was from 12” to 14” Brix. The Evergreen showed consistently a rather high density, but the flavor of the sirups from this variety was always very disagreeable. I n fact, these sirups were in a class by themselves, having a disgusting, nauseating taste. It will be noted that the purity quotients shown in the last two columns of Table I are much lower for the samples from this variety than for those from any other. This would indicate a rather high content of nonsugar solids in the juice and sirup. When the sirups were examined after standing several weeks, it was found that the Evergreen samples contained considerable amounts of a crystalline deposit, which proved to be potassium nitrate. It was undoubtedly the cause of the bad flavor, and also of the lorn purity coefficient, since solutions of this salt have a higher density and a lower index of refraction than other salts in plant juices.
Vol. 16, No. 7
of low quotients. It was suggested above that the high mineral and nitrate content of these samples was due to the soil on which they were grown, and that thus any variety might show this phenomenon. If this is so, it would behoove any manufacturer of cornstalk sirup to ascertain the condition of the juice before makingitinto sirup. It is believed that the refractometer and the Brix scale furnish the simplest means for this purpose, and it is tentatively suggested that any juice with a quotient of 94 or less be regarded as unsuitable for sirup-making. It is further suggested that this method might be found of advantage with other plant materials as an index of their quality for a particular purpose. FIELDTRE4TMENT-The principal items to be observed under this heading were the effect of shocking in the field several days, of stacking without the leaves, and of removing the ears. I n some work not presented here it was shown that when the ears are removed at the canning stage and the stalks are left standing in the field, there is a more or less rapid rise in the density of the juice for the next 10 to 20 days, and that there is some tendency for the purity to increase during this period. This verifies Stewart’s claims.ll The data in Table I show that the flavor of the sirup is not appreciably affected by the removal of the ears. Of course, the yield of sirup becomes greater as the density of the juice increases, but the purity is not affected sufficiently to make TABLF 11-RELATION BETWEEN P U R I T Y QUOTIENT (SOLIDS-OVER-BRIX) AND FLAVOR OF CORNSTALK SIRUPS any improvement in the flavor. Furthermore, stacking the (Numbers are those of the qamples in Table I) stripped stalks for 2 to 4 days does not affect the sirup_ _ _ _ _ _ _ _ _ _ S ? x 100 ________ -----. FlavorRatings making qualities, although it does in most cases increase the Brix 99 98 97 96 95 94 93 92 91 acidity and the density of the juice, chiefly because of loss of 1 32 31b 39 moisture from the stalks. 33 25 26 37a 28b P O L A R I Z A T I O N - T ~ ~ polarizations show nothing of signif37b 41 34a icance as regards sirup quality. 2 31a 31: 296 50 35a EXTRACTIONS-The low extractions shown in Table I 31b 28a 49 38 35b 30a 29a 36 51 are misleading. That the low extractions are due to the mill 30b 3 46a 43 40 42 and not to the character of the cornstalks was shown by the 46b 44 45 fact that a good sample of stripped sorghum cane yielded 52 47 only 35 per cent of its weight as juice, whereas with a large The question naturally arises as to whether Evergreen commercial mill the extraction would have been a t least 60 always produces a juice high in potassium nitrate. It per cent. The stalks of all varieties of corn were remarkably probably does not, for in 1921 the sirups from this variety juicy, considering the fact that they are generally known to be were quite as good as the others. Furthermore, the ash merely pithy in character. content (not shown here) of the Evergreen samples in 1922 ACIDITY-It was found by experience that an acidity of was far higher than that of any other variety, but in 1921 6 t o 8 degrees (cc. of 0.1 N alkali per 100 cc. of juice) in the this was not true. The writers believe the explanation of clarified juice was the most desirable. A higher acidity gave the whole matter lies in the nature of the plot of ground on a sharp tasting sirup, while a lower acidity gave a dark sirup which the Evergreen was grown in 1922. I t had been in pas- because of the nearness to an alkaline reaction. Lime in the ture for 3 years, and the accumulated manure caused a very form of the hydroxide was used for neutralizing. At first the heavy, rank growth of the Evergreen, most of it being over titer of the raw juice was taken, and the calculated amount of 7 feet high. Nitrification, no doubt, took place veryrapidly, lime added. It was soon found, however, that the neutralizwhich resulted in loading up the sap of the corn with nitrates. ing effect of a unit of lime was not always the same. TherePURITYCOEFFICIENT-The quotient solids-over-Brix for fore, the juice was first defecated by heat, then the titer taken both juice and resultant sirup is given in the last two columns and lime added. Even then irregular results followed, SO of Table I. Since the clarification process removes non- it was decided to make a more detailed study of the acidity sugar material primarily, it is of interest to examine the quo- changes that take place during the various steps of the tients to see whether there is any apparent purification. clarification process. The results are incorporated into Out of 21 samples where values for both juice and sirup are Table 111,although in Table I also the initial and final acidities available, 13 show an increased quotient, 6 show a decreased, are given. and 2 do not change. Thus, in two-thirds of the cases there is I n Columns E, F , G, and H , “raw” juice is that which is an increase in purity shown by this test. In most cases the fresh from the mill, before heating; “defecated” juice is that difference is only one or two points. which has been brought to the boiling point and the scum There appears to be some relation between the flavor of removed from the surface; “treated” means defecated juice the sirup and the purity quotient. Those sirups having which has been treated with kieselguhr and carbon and then flavor values of 2 and 3 have lower quotients than those filtered; “limed” means after the addition of lime and a having a value of 1. This is brought out rather strikingly by second filtering. All these stages were not followed in each arranging the purity quotients of the sirups against their case. flavor ratings, as has been done in Table 11. It will be noted I n Column I are assembled the differences in titer between especially that all the Evergreen samples fall in the columns the raw and the defecated juice, and those figures show the changes in acidity brought about in the juices by heat alone. 11 U. S. Patent 811,533 (January 30, 1906)
Juiy, 1924 Days since Canning Sfage SamEars On when or-Off cut $1 e B L 24 32 37 39 26
I N D UXTRIAL A N D ENGINEERING CHEMISTRY TABLE111-CHANGES
IN
ACIDITYI N CORNSTALK
JUICE
.
27 25 33 34 38 28 29 30 31
35 36 41 40 46 52 43 44 47 42 45 49 50 51
DUE
TO
----Acidity of Juice--Cc. 0.1 A' per 100 Cc. of Juice --CHANGES DeieF I E L D TREATWENTRaw cated Treated Limed 3-F F-G E D F G H I J Minnesota N o . 13 0 On Milled fresh 19.0 1.5 8 Off 25: 0 Milled fresh 31.0 19.5 19:5 6:O 5: 5 Off 22.5 Milled fresh 29.5 13 2 0 . 0 (a) 20.0 7 . 0 2.5 (b) 9.0 16.7 16a On Milled fresh 18 5 12.0 7.0 1.8 4.7 Stacked without 0 On leaves 2 days 15.0 .. 7.5 7.5 .. Stacked without On 0 20.0 .. 11.0 .. .. leaves 3 days .. Crosby, Plot 1 0 Milled fresh 15.0 On 6.0 6.0 Milled fresh 31.5 8 Off 2310 8.0 8 . 0 d:b 1.i:0 Milled fresh Off .. 19.5 9 1 5 . 0 (a) 1 5 . 0 .. 4.5 (b) 6 . 0 14a On Milled fresh 16.0 20.5 12.5 12.5 4 . 5 3.5 Stacked without 1 On 14.0 leaves 2 days .. (a) 7.0 7.0 .. (b) 6.0 6.0 Stacked without 1 On .. (a) 14.0 14 0 .. 15.0 .. leaves 4 days Cb) 1 0 . 0 10.0 Shocked with 3 Off 16.4 14.0 1 4 . 0 ( a ) 14.0 2 . 4 leaves 2 days 0 (b) 9.0 Shocked with Off 2 1 6 . 5 (a) 12.0 12.0 3 . 5 leaves 4 days 20.0 4.5 ( b ) 11.5 11.5 5.0 (6) 7.4 7.4 9.1 Crosby, Plot 2 1 Off Milled fresh 18.5 16.5 14.0 5.0 2 . 0 2.5 Off 2 Stacked without 21.5 20.5 leaves 2 days 15.0 6.0 1 . 0 5.5 Off 16.7 Milled fresh 14.0 7.0 4 . 8 21.5 8 2.7 Stowcll's Esevaveen 16.7 0 On Milled fresh 13.5 8.0 2.8 19.5 3.2 On Milled fresh 21.0 (a) 21.0 2 . 0 6 25.5 23.5 2.5 (b) 6.0 Off 10 27.5 26.0 Milled fresh 21.5 6.5 1.5 4.5 On Slacked without 0 18.5 15.0 leaves 2 days 8,.0 5 . 0 23.5 3.5 On Stacked without 0 15.5 6.3 1 . 5 22.0 20.5 leaves 4 days 5.0 0 On Stacked without 16.2 8.0 2.0 21.5 19.5 leaves 6 days 3.3 On Shocked with 0 16.7 8 . 5 3.0 24.0 21.0 leaves 3 days 4.3 On 0 Shocked with 20.0 10.5 2 . 5 23.5 leaves 5 days 26.0 3.5 Countrv Gentleman 10.5 14.0 10.5 1 . 0 0 On Milled fresh 15.0 3.5 13.0 5 . 5 1.3 16.7 4 Off Milled fresh 18.0 3.7 0 Stacked without On 23.5 20.5 6 . 5 1.0 24.5 leaves 3 days 3.0 a Ears in hard dent stage. I
..
The changes are considerable, ranging from 1.0 to 8.5 degrees. Column J shows that the addition of kieselguhr and of carbon reduces the acidity, and that these reductions are even greater than those shown in the preceding column, ranging from 0 Lo 15. Column K gives the total change from raw to treated juice. That both carbon and kieselguhr alone affect the acidity is shown by a closer examination of the data. In Samples 28a and b, and 3 l a and c, where the carbon was omitted from one pair, it is shown that the carbon has considerable effect in reducing the acidity. Samples 31a, b, and c show that the kieselguhr alone has the same effect. These facts explain the irregular action of lime on the raw juice. When the lime effect is segregated from the others, it is found to be rather consistent in its neutralizing power. This is shown in the last two columns of Table 11. The ratio of the :tctual to the theoretical amount of lime is close to 1. This is quite contrary to the findings of Anderson12 with sorghum juice, in which 2.2 times the theoretical amount of lime is necessary to produce neutrality. In order to see whether the acidity of sorghum juice behaves like that of corn juice under the action of heat and of kieselguhr, some experiments were run a t a sorghum sirup factory after the close of the corn sirup season. No change in the titer occurred, either during the heating of the juice or by the addition of kieselguhr. Furthermore, kieselguhr in any concentration had no appreciable effect on the acidity of solutions of tartaric, citric, and hydrochloric acids, showing that it is not a question of a contained alkali. It is there12
Anderson, THIS JOURNAL, 9, 492 (1917).
737
VARIOUS FACTORS
IN
ACIDITY.CC.E-G
K
17.5 11.5 9.5 6.5
G-H
L
0' 0
11.0 5.0
Grams
Kieselguhr Carhon
56
70
2 1 1 1 1
0 5 0.5 0.5
M
N
0.5
0.5
Lbs.
Juice 0
CaiOHln
Theo-
retical P
..
0 0 16.1 7.3
0.88 0.89
7.5
0
1
0.5
0
9 0
..
1
0.5
0
1 1 1 1 1
0.5 1.0 0.5 0 ,5 0.5
0
8.0
0 0 0 9 0
7.0 8.0
0 0
1 1
0 0.5
0
1.0 5.0
0 0
1 1
0 0.5
0 0
2.4
0 5
1 1
0 0
0 7.3
0 0 0
1 2 1
0 0 1.0
0 0 0
4.5
9.0
1
0.5
13.0
0.89
6.5 7.5
9.0 7.0
1 1
0.5 0.5
14.5 9.4
0.98 0.82
6.0 4.5
8.0
5.5 0 15.0 15.0
1 1 1 1
0.5 0.5 0.5 0.5
9.1 0 21.5 22.4
0:87 0.91
8.5
7.0
1
0.5
12.0
1.04
6.5
9.2
1
0.5
13.2
0.87
9.0 23.5
..
8.0 8.5 12.6
0
0 18.9 0
1.28
0.89
1.01
5.3
8.2
1
0.5
14.7
1.09
7.3
8.2
1
0.5
14.4
1.09
6.0
9.5
1
0.5
19.2
1.23
4.5 5.0
0 7.5
1 1
0.5 0.5
0 9.3
0.76
4.0
14.0
1
0.5
19.4
0.85
fore believed that the foregoing acidity changes in cornstalk juices are due to particular colloid adsorption phenomena. Whatever the explanation, these changes must be watched in making cornstalk sirup if the proper acidityis to be obtained. EFFECT OF KIESELGUHRAND O F CARBON-Besides the neutralizing effect of the kieselguhr, it has very valuable filtering properties, as has been repeatedly shown for other products. Juice containing 1 per cent of its weight of kieselguhr filters very readily, builds a thick cake, and produces a brilliant filtrate. Although in most of the present experiments the scum was removed from the juice prior to filtering, there is no doubt that this amount of kieselguhr would be ample for good filtration without the removal of the scum. Cornstalk juice filters much more easily than does sorghum, owing no doubt to the lack of starch in the former. Two brands of decolorizing carbon13 were used during the investigations, although in the experiments listed in Tables I and I1 but one kind was used. As regards the decolorizing action of the carbons on cornstalk juice, the results were very disappointing. It will be noted in the table that as often as not the use of carbon resulted in a sirup of a darker color. Many combinations of acidity and quantity of carbon were tried, but no satisfactory decolorizing action could be obtained. Color is of less importance than flavor, however, since all these sirups have satisfactory color for cooking sirups, and since flavor is the deciding factor in sirup quality. The carbons did not affect the flavor to any appreciable extent. If, 18 T h e writers' thanks are due the Carbrox Co., Inc., and the General Norit Co., Ltd , for generous samples of Carbrox and of Norit, respectively
738
Vol. 16, No. 7
INDUSTRIAL A N D ENGINEERING CHEMISTRY
as the evidence above seems to indicate, the flavor in these sirups is largely dependent on the ratio of sugars to mineral matter, perhaps no great effect on the part of the carbon should be expected. SUGGESTED PROCESS OF MAWFACTURE There must now be considered the question of the processes and machinery that should be employed for the successful manufacture of cornstalk sirup on a commercial scale. The general process outlined above for the experimental lots of sirup is essentially the same as would be used on a large scale and is practically the same as the best accepted process of making sorghum sirup.l4 H.4RVESTING-After picking the ears for canning, the stalks should be allowed to stand in the field for from 10 to 20 days, in order to develop the maximum sugar content in the juice, thus following essentially the Stewart process.ll It will be found highly desirable to test samples from each field with a Brix hydrometer from time to time, in order to ascertain the period of greatest density. If a refractometer is available, the solids-over-Brix quotient should be determined, since this gives a good idea of the quality of the juice. Any juice with a quotient of 94 or lower is probably unfit for sirup-making. When the stalks are ready for harvesting, they should be cut with a corn binder and either brought to the factory immediately and there shocked for a few days, or allowed to dry on the ground for 1 or 2 days and then brought to the factory for immediate milling. The object of the partial dryingof the leaves is to facilitate handling in the cleaning machine. The calculations in Tables I and I1 are based on the freshly cut, stalks. If they are allowed to dry for a day or two before weighing a t the factory, the price per ton should be increased about 20 per cent to allow for the shrinkage. CLEANING AND MILLIN@-The leaves must not be milled with the stalks, because they absorb juice and contribute impurities. Since removal of the leaves and tassels by hand in the field is out of the question for economic reasons, a cleaning machine a t the factory is necessary. A 6-1-011mill, preferably with crusher attached, should be used. . DEFECATION AND FILTRATION-The juice from the mills is heated by steam in defecatQrs, just to the boilingpoint. The juice is then titrated and lime added so as to reduce the acidity to about 12 degrees, counting on the kieselguhr treatment to reduce it further to about 7 to 4 degrees, which is the desired acidity. After liming, kieselguhr to the amount of about 1 per cent of the weight of the juice is added and the juice is thoroughly stirred and pumped immediately through a filter press, the cloths of which have been precoated with kieselguhr. The juice filters readily and becomes sparklingly clear. The use of decolorizing carbon is not recommended, as the writers’ results with it were not satisfactory. EvAPoRATIoN-Evaporation of the juice should be done in a vacuum evaporator, both because of the better quality of sirup produced and because of the economy in fuel. A density of 75” to 78” Brix is desirable in cornstalk sirup. From the evaporator the sirup should be pumped through a cooler to the storage tank. BY-PRODUCTS-The bagasse can best be used for fuel. If good milling is accomplished, it will have a moisture content of about 50 per cent, and will burn directly if the proper kind of grate and furnace is used, or a t least with a small amount of coal in addition. The leaves from the cleaner can be ensiled with the husks and cobs from the cannery, or they can be dried and baled. I n some cases it might be profitable to dry both bagasse and leaves and bale them together for feed. Conservation of all possible useful products is quite necessary 14 Willaman, Sugar, 24,83 (1922); Willaman, West, and Bull, Minnesota Agr. E x p t . Sta., Bull. 187 (1919).
for the economical operation of a combined cannery and sirup factory. The Stewart patent1*for removing the ears at approximately the canning stage in order to increase the sucrose content of the juice may be involved in the process outlined above. Although this patent is entitled, “Method of making maizesugar,” the writer apparently had sirup in mind also, for in all his claims in connection with the clarified juice he speaks of ‘(reducing it to sugar or sirup.” A prospective manufacturer of cornstalk sirup would have to give consideration to the above. The patent expires January 30, 1926. TAELP~ IV-AVERAGE
YIELDS OF VARIOUS VARIBTIES OR C O R N
Yield of Whole Stalks per Acre Ponnds Stowell’s Evergreen, 1921,ears off Stowell’s .Evergreen, 1922,ears off Country Gentleman, 1921,ears off Country Gentleman, 1922. ears off Narrow Evergreen, 1921 ears off Crosb; 1922 earsoff Golden’Banthn, 1921. ears off Silver King, 1921.ears on to hard dent stage Silver King, 1921,ears Off
Minnesota No. 13 1922 ears on to hard dent stage Minnesota No. 1922,ears off 13’
Extraction
.-
41,
Yield of Sirup per Acre Calcd. Sirup per for 60 yo Ton of Extrac- Cane 60% Found tion Extraction ’Brix Gallons Gallons Gallons
19,000
48 13.7
86
109
11.5
16,160
47
13.6
73
92
11.4
..
14.5
12.1
49
.,
138
10.660 . 15,000 6,000
13.6
47
61
11.4
48 12.6 44 13.2
64 25
79 33
10.5 11.0
6,830
48 14.4
33
41
12.0
22,500
12,160
43
10.2
37
52
8.5
17,330
43 14.2
74
103
11.9
12,500
50
9.9
42
51
8.3
15,660
46
14.9
74
97
12.5
COSTOF MANUFACTURE Since the primary object of the present investigation was to discover a more valuable use for the sweet cornstalks around canneries than that of forage, it becomes necessary to examine data concerning the probable cost of making sirup from the stalks. The greater proportion of the stalks in Minnesota is fed standing; a little is ensiled, and some is not used a t all. Thus the cannery would have to compete against these other needs for the raw material for sirup manufacture. Since corn is not usually considered to have a saccharine juice in the ordinary sense, it becomes of special interest to examine the data concerning the yield of sirup obtainable from the various varieties of corn tested. Although only a few hundred pounds were obtained at each sampling, it is believed that the tonnage figures are fairly accurate, since in most cases several lots of each variety were obtained, representing different stages of maturity after removal of the ears. The data are given in Table IV. The samples presented were selected from a large number. They include snly the “ears off” samples of the sweet corns and mostly the “ears on” samples of the field corns, since these are the ones of interest from the commercial standpoint. The yields of stalks are given in terms of the fresh stalks, with the ears removed but with leaves and tassels on. The clean cane represents about 60 per cent of this weight. The extraction figures given are those actually obtained from the clear cane, and not from the whole stalks. The calculated extraction of 60 per cent is on the same basis, and was made in order to give a more accurate comparison with what could be expected in larger multiple mills. The sirup figures are in terms of sirup weighing 11.5 pounds to the gallon and containing 75 per cent of solids. It will be noted that the tonnage varies from about 3 in the case of Crosby and Golden Bantam to about 9 in the case of Evergreen and the field corns; that about 11 to 12 gallons of sirup are obtainable per ton of cane as purchased; and that about 100 gallons of sirup may be expected per acre. For comparison, it might be mentioned that sweet sorghum in
July, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Minnesota yields from 10 to 20 tons of whole cane per acre, and about 16 gallons of sirup per ton.
DESCRIPTION AND USES OF
THE
SIRUP
The sirups made during the present investigations were usually clear; only in a few cases did they become cloudy during evaporation. In color they ranged from a light amber, similar to a good grade of maple sirup, to a dark brown, similar to molasses. The viscosity of the sirups was about that of maple sirup of the same density. The flavor, of course, is difficult to describe. Many people pronounced it very similar to that of sorghum, although in the writers' opinion they were not a t all alike. Most of the samples made had a mild, agreeable flavor; less pleasing than that of high-grade sorghum, but more so than that of molasses. Some of the samples made from corn grown in soil unusually rich in nitrates and other minerals had a very disagreeable flavor as was discussed above. Such sirups are unfit €or food, but their occurrence would probably be unusual and could be predicted by watching the purity quotient of the juices, as suggested. The cornstalk sirups so far produced are not suitable for table use, but are well adapted for cooking purposes. The writers have submitted samples of the sirups to a great many individuals for use in the home; to a class in experimental cookery ; to a cafeteria for use on a large scale; to an experienced buyer of sirups and molasses; and cookies made from these sirups, from sorghum, and from molasses to several groups of people for comparison. The general opinion of these various observers was that the cornstalk sirup is equal to the best grade of sorghum and molasses, and much superior to the lower grades, for all cooking purposes. One objection was that the sirups do not impart so dark a color to the products as molasses does but such an objection probably would not be general, The flavor of the products is not so pronounced as when molasses is used, but this difference seemed to be acceptable to the great majority of the judges. From the foregoing evidence the writers consider cornstalk sirup to be a competitor of high-grade molasses and sorghum. SUMMARY I-The stalks of all varieties of sweet corn, and two varieties of field corn, gave satisfactory sirup, with the exception of Stowell's Evergreen in 1922, which contained an excessive amount of potassium nitrate. 2-The purity coefficient, solids-over-Brix, of the juice and of the sirup proved to be a very useful criterion of quality. It is suggested tentatively that any juice with a quotient of 94 or less be considered unsuitable for sirup-making. 3-Stalks a t all ages after removal of the ears made good quality of sirup. The purity did not appreciably increase as the density of the juice increased with the age of the stalks. 4-Shocking the stalks with the leaves on, or stacking them with the ears removed, for periods up to 4 days, did not affect the sirup-making qualities, although the acidity and density of the juice increased in most cases. 5-Although in the present experiments low percentages of juice were obtained, this was due more to the character of the mill than to the lack of juiciness of the stalks. 6-The titratable acidity of the juice always decreased during defecation by heat. It decreased further by the addition of kieselguhr and of activated carbon. These changes have to be taken into consideration in controlling juice acidity. Calcium hydroxide exerted almost theoretical effect in neutralizing juice acidity. 7-Activated carbons had practically no value in decolorizing cornstalk juices, and very little in removing objectionable flavor.
739
8-Kieselguhr proved to be an excellent filter aid, and the juices filtered very satisfactorily with 1 per cent of their weight of this material. 9-A brief outline of the process of manufacture recommended for commercial practice is given. It differs from the manufacture of sorghum sirup only in the treatment in the field and in the control of the acidity. 10-The smaller varieties of sweet corn yield 3 or 4 tons of stalks to the acre; the larger varieties of sweet corn and field corn, 9 to 10 tons. 11--Most varieties, allowed to stand for 2 or 3 weeks after picking the ears, yield from 11 to 12'gallons of sirup per ton of whole cane. If used a t the time of picking, the yield may be as low as 8 or 9 gallons. 12-Cornstalk sirup is usually clear, of a reddish amber color, and has a mild, agreeable flavor. It is not a table sirup, however, but a cooking sirup, with characteristics and uses very similar to those of sorghum and of molasses.
Fermentation of Natural Fruit Juices' By B. A. Dunbar and C. F. Wells SOUTH
DAKOTA STATSCOLLEGE, BROOEINGS, S. D.
N THE course of a series of calls for evidence in criminal
I
cases involving the enforcement of the liquor laws, the writers have been confronted with a need of more accurate data than they have been able to adduce, relative to Conditions under which the spontaneous fermentation of cider and other common fruit juices may take place most rapidly, of the effect upon such reaction which an addition of sugars such as glucose may produce, of the temperature conditions that accompany maximum or minimum production of alcoholic content, and of the time factors that have to do with such maximum effect. Since the admixture of foreign materials was usually found to be so varied in kind and quantity as to preclude imitation in experimentation during the period wherein freshly expressed juices could be secured, the writers have confined their work to the time rate of fermentation and the increase of alcohol content attendant upon such a fermentation as proceeds when the raw juices are allowedto ferment without addition of ferments and when more or Iess glucose is added, without the presence of yeast or other added catalysts. I n the experiments described in this paper glucose has been used, since this type of sugar has been found to be too much in evidence in unlawful production of alcoholic beverages. However, for comparative purposes, cane sugar will be used in some future experimentation.
EXPERIMENTAL Apples of the Jonathan variety and Concord grapes were thoroughly pulped and this pulp was pressed through a hand press of the screw type, whereby a juice of the concentration naturally met in such processes was obtained. These juices were a t once transferred to sterile beakers, loosely covered with cheesecloth to prevent contamination by foreign materials, and placed in electrically heated compartments having free access to the air, and maintained a t a constant temperature of 21' C. (70"F.) (withno variation greater than a fractionof 1degree) throughout theexperiment. At the end of each 24 hours the contents of each beaker were thoroughly stirred and two samples were taken for analysis-one of 50 cc. to determine alcoholic content, and one of 10 cc. which was titrated against 0.2 N sodium hydroxide to de1 Received
February 29, 1924.
