INDUSTRIAL AND ENGINEERING CHEMISTRY
80
Vol. 40, No. 1
ISOMERIZATION ACCOMPANYING POLYMERIZATION
PODBIELNIAK DISTILLATION OF TABLE IV. HIGHTEMPERATURE 3-h!!ETHYL-I-BUTENE
P O L Y M E R S FROM
Boiling Fraction Range,
KO. 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 (bottoms)
O
C.
75-142 142-146 146-148 148-148 148-149 149-160 150-150 150-152 152-152 152-154 154-155 155-156 156-158 158-158 158-160 160- 162 162-165 165-168 168-174 174-176 176-184
..
Distillate, Cc./Total Fraction Cc. 40 40 50 90 55 145 52 .~ 197 100 297 357 60 100 457 515 58 615 100 715 100 815 100 913 98 100 1013 100 1113 100 1213 100 1313 7 2 1385 58 1443 25 1468 33 1501 21 1522 73 .
I
Volume, %
Per
.
fraction Total dZo 2 . 5 0.7360 2.5 5 6 3.1 .... 3.5 9 . 1 0.7500 3.2 12.3 .... 1 8 . 6 0,7550 6.3 .... 3 . 8 22.4 28.7 0.7560 6.3 32.3 .... 3.6 6 . 3 38 6 0 . 7 8 7 0 ,... 6 . 3 44.9 5 1 . 2 0.7600 6 3 6.1 57.3 .... 6.3 6 3 . 6 0.7617 69 9 .... 6.3 7 6 . 2 0.7640 6.3 82.5 6.3 8 7 . 0 0 : 7677 4.5 90.6 3.6 1.6 9 2 . 2 0 :7730 94.2 .... 2.0 9 5 . 5 0.7810 1.3 4 . 5 100.0 ....
Bromine ':n 1.4215 1.4275 1.4276 1.4280 1.4309 1.4308 1.4320 1.4320 1.4323 1,4328 1.4340 1.4341 1,4346 1.4349 1.4353 1 4360 1.4368 1,4380 1.4392 1.4400 1,4419 1.4501
No. 121
...
99
, . .
106
io5 ...
106
...
102
...
103
... 102 ... 103 .
.
I
96
.. si
...
TABLE V. ISOMERIZATION O F 3-hIETHYL-1-BUTEXE DURING POLYMERIZATIOX IN PRESENCE OF SOLID PHOSPHORIC ACID CATALYST
Run S o . TemD.. C Gage pressure Kg./sq. om. Lb./sq. in. CaHlo charged, cc./.hr. CsHlo recovered, % by vol. of charge Isomerized CaHio % ' by vol. of recovered CsHio % by vol. of CsHu charged to polymerization
3 84
4 83
7.7 109 224 47
7.7 109 134 40
18 8.4
22 8.0
5 100
8.0 113 125 19 40
7.8
Examination of the pentene recovered from the mixtures of polymers and unpolymerized pentene showed that part of the 3-methyl-1-butene had been isomerized into a pentene with higher boiling point, probably 2-methyl-2-butene. 2-Methyl-lbutene is another possible isomerization product obtainable from 3-methyl-1-butene by shifting of the double bond, but the boiling point of the isomerized pentene (35' to 38" C.) indicates 2-methyl-2-butene to be the more probable product. The results of this study on isomerization of 3-rhethyl-1-butene during polymerization are summarized in Table V. As the depth of polymerization increased, the concentration of isomerized pentene also increased in the pentene which had come into contact with the catalyst but had not polymerized. I n run 5, 40y0 of the recovered pentene boiled above 3-methyl-1-butene. However, in each of the three tests where the percentage of polymerization differed, approximately 8% of the 3-methyl-1-butene charged was recovered as the higher boiling pentene isomerization product. BIBLIOGRAPHY
(1) Ipatieff, V. N. (to Universal Oil Products Co.), U. S. Patents 1,993,512and 1.993.513 (Mar. 5 , 1935); 2,018,065 and 2,018,066 (Oct. 22, 1935); 2,020,649 (Nov. 12, 1935); 2,057,433 (Oct. 13, 1936) ; 2,060,871 (Nov. 17, 1936). (2) Ipatieff, V. N., and Corson, B. B., IWD. ENG.CHEM.,30, 1039 (1938). (3) Ipatieff, V. N. and Schaad, R. E. (to Universal Oil Products Co.), U. S. Patents 2,120,702 (June 14, 1938), 2,157,208 (May 9 , 1939), and 2,275,182(Mar. 3, 1942). (4) Universal Oil Products Co., Brit. Patents 437,188 (Oct. 14, 1935),463,272 (1Mar. 25. 1937),463,861 (Apr. 7, 1937),464,671 and 464,672 (Apr. 19, 1937); French Patent 797,584 (Apr. 29, 1936). RECEIVED November 14, 1946. Presented before the Division of Organic Chemistry a t the 109th Meeting of the AMERICAK CHEMICAL SOCIETY, Atlantic City, N. J
Conversion of Corn Amylopectin by Barley Malt Enzvrnes J
J
J
T . MUNSEY BACK A N D W. H. STARK', Joseph E . Seagram h Sons, Znc., Louisville, K y . C . C . VERNON, University of Louisville, L o u i s d l e , K y .
T
H E conversion of starch to fermentable sugar is of fundamental importance in the production of alcohol from starch products. Under present industrial practices approximately 70a/, of the starch is rapidly converted to maltose b,y barley malt enzymes, the remaining 30% being converted to unfermentable limit dextrins. The conversion of these dextrins, socalled secondary conversion, occurs during fermentation and requires 36 to 60 hours. The necessity for secondary conversion results in the need for a high quantity of barley malt and large fermenter capacity; furthermore, the slow secondary conversion results in a slow production of alcohol and a greater chance for bacterial infection. I n addition, the elimination or reduction of the time reqhired for secondary conversion is highly important, if not essential, for the successful development of the completely continuous process of alcohol production. Conversion of starch is apparently related t o the structure of the starch components. hccording to present concepts, the amylose fraction, made up of unbranched chains of glucose residues connected through alpha 1,4-glucosidic linkages is almost comPresent address, Vickers Vulcan Process Engineering Company, Ltd., Montreal, P. Q..Canada. 1
pletely converted to 'reducing sugar (primarily maltose) by barley malt amylases (9, 1 2 ) , while the amylopectin or branched chain fraction is incompletely converted (8). Apparently the incompleteness of conversion is a consequence of the malt amylases encountering a linkage or structure in the amylopectin molecule that acts as an obstacle to further action (4, 5, 10). The study repprted herein was undertaken to determine experimentally the degree of malt hydrolysis and fermentation behavior of starches containing different proportions of the starch components, and then by further studies to determine the effects of various factors on malt hydrolysis of that fraction of starch that resists hydrolysis. The object was to find optimum conditions for the hydrolytic action of barley malt on starch in order to increase the degree of conversion previous to fermentation, and to reduce, if possible, the quantity of malt required for conversion. CONVERSION AND FERMENTATION OF WHOLE STARCHES CONTAINING VARYING PROPORTIONS OF AMYLOPECTIN
Waxy maize starch (American Maize Products Company), consisting of practically pure amylopectin (8, 14), and corn starch, containing 79% amylopectin (2) were premalted, pressure-
January 1948
INDUSTRIAL AND ENGINEERING CHEMIStRY
Corn starch containing approximately 79% amylopectin was more readily converted to fermentable sugars and gave higher alcohol yields than did waxy maize starch composed of practically pure amylopectin. It was found possible to increase the conversion of corn amylopectin in a short time by supplying optimum conditions for theaction of the malt enzymes, but the highest conversion that could be achieved in 15 minutes was approximately 76%. Under optimum operating conditions rate of conversion beyond the initial 15 minutes was slow. With varying quantities
81
of barley malt and varying times of hydrolysis in excess of 5 minutes, the optimum hydrolysis temperature for corn amylopectin conversion was determined to be in the range 52'-57' C. and the optimum pH in the range 5.35.6. As the barley malt quantity was increased from 0 to 15-20 grams per 100 grams amylopectin (dry weight basis), there was a progressive and substantial increase in the degree of conversion of amylopectin; this was true for 15-, 30-, and 60-minute hydrolysis periods. Higher maltamylopectin ratios gave only slightly higher conversions.
T o show more clearly the difference in the degree of hydrolysis cooked (during the cooking step the concentration of starch was of the two components of starch, amylose and amylopectin, furapproximately 16 grams per 100 ml. of water), and hydrolyzed ther studies on the pure components were necessary. I n order to for 1 hour at 63" C. and p H 5.3 with barley malt (13 grams per prepare pure components from starch, it was first necessary to 100 grams of starch) under identical conditions on a laboratory devise a procedure for preparing pure starch with the structure as scale. (Thirteen grams of barley malt per 100 grams of starch is unaltered as possible and then to fractionate the starch into its equivalent to approximately 8.5 grams of malt to 100 grams of components. corn in a corn mash, which is in the range commonly employed in The preparation of pure starch presented a definite problem, distillery practice.) Distillers' dried solubles (10% based on the since the method of preparation necessarily involved steeping in weight of starch) were added as a yeast nutrient. After adjustwater and grinding; both of these processes must be rigidly conment of the pH to 4.8, each mash was divided into four portions; trolled in order to avoid chemical action on the starch and one of these was saved for analysis, and the other three were inocchanges in the starch structure. The laboratory procedure deulated with the Seagram No. 1Y strain of Saccharomyces cereviveloped is similar to the commercial process, but numerous modisiae and fermented for 66 hours at 28" C. Blanks containing all fications were desirable to avoid chemical or physical change in constituents except starch were also run in an identical manner so the starch. Modifications included the use of the single steep systhat necessary corrections to final data could be made. The data tem, shorter steeping time a t lower temperature, very coarse obtained are presented in Table I. grinding (to break up the softened grain), and the use of only Reducing sugars after conversion, and total sugars before conphysical means thereafter in the.separation of the starch. Methaversion and after fermentation, were determined by the micro nol (85%) wm used to remove fatty impurities. Relatively low method of Shaffer and Hartmann (16) as described by Stiles, temperature drying was employed after the methanol extraction. Peterson, and Fred (16). (Total sugar as glucose was determined after acid hydrolysis. For lack of a rapid, accurate selective method, reducing products are reported in terms of maltose. AcPREPARATION OF P U R E STARCH tually the reducing power is primarily due to maltose, but small Two kilograms of the cleaned corn grain were washed thorquantities of other reducing substances are also produced during oughly and then steeped for 24 hours in approximately twice that malt hydrolysis of starch.) Alcohol determinations were made on volume of distilled water containing 0.2% sulfur dioxide and at a distilled samples by determining the refractive indices of the temperature of 46-50' C. After thorough washing with distilled distillates with a Zeiss immersion refractometer. The degree of water, the softened grain was coarsely ground and distilled water hydrolysis, expressed as apparent per cent conversion, was calcuadded. The mixture was allowed to stand for 1 to 2 hours (with lated as reducing sugar (maltose hydrate) times 100 divided by the frequent agitation) ; the resultant pulpy mass was poured into total sugar derived from acid hydrolysis of the initial starch, as nylon mesh bags, drained, and pressed. The mass in the bag was glucose. further extracted with distilled water until only a negligible Efficiency data were calculated on the basis of one molecule of amount of starch appeared in the wash water. The starch-gluten glucose producing two molecules of alcohol. Plant efficiency was suspension so obtained was filtered through a double layer of nycalculated as actual alcohol produced times 100, divided by the lon mesh, and the solids of the filtrate were allowed to settle. theoretical alcohol based on the total sugar. Fermentation efAfter removal of the supernatant liquid by siphoning, the remainficiency was calculated as the actual alcohol produced times 100, ing thick suspension was centrifuged and the top or gluten layer divided by the theoretical alcohol based on the total sugar. ferremoved by scraping. By repeatedly resuspending the starch, mented. centrifuging, and scraping off the gluten layer, the gluten was Waxy maize starch, probably because of its greater amylopecfinally removed. tin content, was converted to a slightly lesser degree than corn starch. The waxy maize starch also showed a slightly lower production of fermentable sugar and a significantly AND FERMENTATION BEHAVIOR O F CORN STARCH AND WAXY TABLE I. HYDROLYSIS lower fermentation and, plant MAIZESTARCH than corn starch. Final residual total sugar (calculated as glucose) was slightly higher for waxy maize starch. These results indicate that the amylopectin fraction of starch presents obstacles to conversion to fermentable sugars under distillery conditions; it appears, too, that the reducing substance formed is less fermentable than that from the amylose fraction.
Starch Variety Corn starch (79% amylopectin, 21% amylose) Waxy msise starch (amylopectin) 0
Initial Total Sugar Calcd. as Glucosea, G./100 ML
Apparent Conversion a t End of 1 Hr. a t 6 3 O C., %
Final Sugar Calcd. as Glucoma, G./100 M1.
Sugar Fermented,
9.64
82.1
10.52
78.7
0.84 0.82 0.89 0.97 1.08 0.94
91.3 91.5 91.6 90.8 89.7 91.1
Total sugar ns glucose wns determined after acid hydrolysis.
%
Efficiency, % Fermentation Plant 96.7 96.9 97.6 93.8 94.6 94.5
88 2 89.1 89.4 85.1 84.9 86.0
82
IND'USTRIAL AND E N G I N E E R I N G CHEMISTRY
PARTS DRY MALTCEFOE EXTRACTION)
TO I O 0
PARTS AMYLOPECTIN
Figure 1. Effect of Barley Malt Quantity on Hydrolysis of Corn Amylopectin a t Various HydroIysis Temperatures Hydrolysis pH 5.5, t i m e 1 hour
Vol. 40, No. 1
pH 5.5 were hydrolyzed for 1 hour a t 63 ', 55 ', and 40' C. using various quantities of malt. The malt quantity is represented as the dry weight of whole malt extracted per 100 grams of amylopectin treated. The data are shown graphically in Figure 1. The conversion-malt quantity curves were similar in shape for the three hydrolysis temperatures, 63", 55", and 40" C. 'For a given malt quantity up to 15 grams of malt to 100 grams of amylopectin, a greater degree as well as a more rapid rate of hydrolysis was achieved at 55' C. than at the usual conversion temperature of 63" C. With an increase in malt quantity beyond 15% the conversion rate was slow. I n general, the results indicated that, using any given malt quantity, greater degree of hydrolvsis was achieved a t 55 ' than at 63 ' or 40' C. For a general procedure for the conversion studies, however, it was desired to find a fairly wide range of malt quantity where slight increase in quantity or quality of malt would have little or no effect on the degree of hydrolysis. An ideal malt quantitp for the experimental procedure way 20-35 grams of malt to 100 grams of amylopectin. In this range the maximum difference in conversion due to malt quantity was slight (less than 1% conversion per 10% difference in malt quantity for each of the temperatures studied). It was also important to determine the effect of concentration of the starch component on the degree and the rate of hydrolysis. The concentration of amylose that could be used in hydrolysis studies was definitely limited to a dilute concentration (less than I. rO), since more concentrated dispersions retrograded readily. T o determine the effect of amylopectin concentration, a 9% and a 1% amylopectin dispersion, both buffered at pH 5.5, were malthydrolyzed a t 55" C. for various periods. Results are shown in Table 11.
To remove oil and other impurities five extractions of the starch at 60-70" C. with methanol were made according to the method of Schoch ( I S ) . After extraction, the starch was spread on filter paper and dried a t low temperature by heat from an infrared heating light. Corn starch prepared in this manner had an ash content of 0.05% and on acid hydrolysis gave Q8.4yOof the theoretical yield of glucose. The separation of the starch components was accomplished by the method of selective precipitation with butanol as described by Schoch ( 1 4 ) . The malt extract used as a conversion agent in all of the conversions reported was prepared as follows: 100 ml. of distilled water were added to 19 grams of finely ground barley malt; the mixture was shaken frequently during the 2.5-hour extraction period at room temperature and was then centrifuged to remove solids. Fresh malt extract was prepared each day. The same malt, a distillers' barley malt, was used throughout. This malt (dry basis) had a diastatic power of 126" Lintner, an a-amylase activity of 31 a-amylase units, and a P-amylase activity of 15 K. S. units. Diastatic power was determined by the A.A.C.C. method ( I ) ; a-amylase activity was determined by the method of Sandstedt, Kneen, and Blish ( l a ) ; and the P-amylase activity was determined by the method described by Kneen and Sandstedt (7). MALT H Y D R O L Y S I S OF AMYLOSE AND AMYLOPECTIN
I n order to devise a standard hydrolysis procedure, it was necessary first to make preliminary studies to determine the efiect of the quantity of phosphate buffer used, the effect of the quantity of maIt extract used for hydrolysis at various temperatures, and the effect of the concentration of amylose and amylopectin. It was fou?d that, when the amylopectin dispersion contained a molar concentration of phosphate buffer of 0.0025-0.02, the quantity of buffer had no significant effect on the hydrolysis. (Molar concentrations above 0.02 were not tested.) T o determine the effect of the quantity of malt on the degree of hydrolysis, samples of a 1% amylopectin di'spersion buffered a t
A
Q)
-
RUN 2
' I
30
I
I
60
90
HYDROLYSIS T I M E
Figure 2.
-
120
150
180
MINUTES
Rate of Hydrolysis of Corn Starch Components by Barley Malt Hydrolysis pH 5.5, temperature 63' C.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Jannary 1948
amylopectin was only approximately 62% converted at this time. Conversion at the end of 3 hours was only slightly higher for both the amylose and amylopectin. These data are significant in that they show that the degree of conversion at 63" C. was almost as great at 5-10 minutes as a t long conversion times (3 hours). Whereas the initial rate of conversion of amylose was approximately twice that of amylopectin during the early stage of conversion, after the leveling-off period the rates became approximately the same. The conversion before and after the leveling-off period was linear with respect to time. The data clearly indicate that the main constituent of grain starches, amylopectin, was only partially (approximately 64%) converted to fermentable sugar by malt previous to fermentation.
8C
h" 7c I
z
0
j;6C
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IJ
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s z
83
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II:
h
e
FACTORS AFFECTING MALT H Y D R O L Y S I S O F AMY LOPECTIN
a 3c 2c
IO
HYDROLYSIS T I M E
- MINUTES
Figure 3. Rate of Hydrolysis of Corn Amylopectin by Barley Malt a t Various Hydrolysis Temperatures
TABLE IT. EFFECTOF AMYLOPECTIN CONCENTRATION ON ITS DEGREE AND RATE O F HYDROLYSIS BY BARLEYMALT Hydrolysis Time, Min. 1 5 15 30 60
Degree of Conversion, % 9% amylopectin
1% amylopectin 26.5 64.3 70.9 72.7 75.5
35.0 58.1 65.2 68.1 72.0
Conversion of the dilute amylopectin was slightly higher than conversion of the concentrated amylopectin, except for the 1minute hydrolysis time. The difference in conversion between dilute and concentrated amylopectin decreased with an increase in hydrolysis time; this difference may have been due to a greater dispersion of the malt in the dilute amylopectin or to a difference in the malt-amylupectin ratio. Since there was not a great difference in degree of hydrolysis at different concentrations, the remainder of the hydrolysis studies were made at the low amylopectin concentration (1%). The conversion limit of the amylose fraction of starch has been reported at 93% and the amylopectin fraction as Sl-S6% when barley malt is used as the conversion agent ( 6 ) . To determine the conversion of corn amylose a t the temperature and p H commonly used for conversion in distillery practice and with an excess of malt, the following method was used: Purified amylose was dispersed in water at 63" c.,buffered to pH 5.5., and adjusted to a concentration of 0.5 per cent; the amylose was dispersed in water just before use and was not allowed to cool, in order to avoid retrogradation. A 1yo amylopectin dispersion was also hydrolyzed under the same conditions. The data are presented graphically in Figure 2. The rate of conversion of starch components at 63 C. was rapid for the first 5 minutes for amylose and for the first 10 minutes for amylopectin. After 15 minutes there was only a relatively slight increase in conversion. Amylose was almost completely hydrolyzed to reducing sugars a t the end of .30 minutes, whereas the
I n order to determine quantitatively the effect of various factors known to affect enzyme behavior on the action of malt amylases on amylopectin, and to determine optimum conditions for the action of the malt amylases, amylopectin was hydrolyzed under various conditions of temperature, time, hydrogen ion concentration, and ratio of enzyme to amylopectin. EFFECTO F TEMPERATURE ON MALTH Y D R O L Y S I S O F AMYLOPECTIN. The optimum temperature for enzyme action under a particular set of working conditions is the point of balance between the accelerating effect of temperature upon a catalyzed reaction and the destructive effect of heat upon the enzyme. This optimum temperature varies with the time of reaction, pH, and impurities present. The degrees and rates of conversion of amylopectin by malt a t various conversion temperatures ar.e shown in Figure 3. The data plotted in Figure 3 indicate that, at any hydrolysis temperature between 40 O and 63 C., the rate of hydrolysis for the first 3 to 5 minutes was extremely rapid; during this period approximately 55% of the amylopectin was converted to reducing sugar. The reaction after the first 5 minutes was slow. The data plotted to show conversion against temperature for various hydrolysis times are shown in Figure 4. Figure 4 shows that there was a gradual rise in conversion with an increase in temperature until an- apparent optimum range 5357" C. was reached. A significantly higher degree of hydrolysis was attained at a hydrolysis temperature of 55" C. than at the usual tempe?ature, 63" C , used in distillery practice. At the latter temperature heat inactivation of the amylases was definitely in evidence, particularly for hydrolysis periods in excess of 5 minutes. It is shown that if a temperature of approximately 55 O
O
80
I
I
O
40
45 50 55 60 HYDROLYSIS TEMPERATURE-
65
1
I
'C.
Figure 4. Degree of Hydrolysis of Corn Amylopectin vs. Temperature for Various Hydrolysis Periods
INDUSTRIAL AND ENGINEERlNG CHEMISTRY
a4
on amylopectin) on the rate and degree of hydrolysis a t 55’ C. is indicated by the data shown graphically in Figure 6. The results indicate that the greater the hydrolysis time (at 55” C.), the less malt was required to bring about a given degree of conversion. However, an increase in hydrolysis time after the first 15 minutes brought about only slightly higher conversion, provided the malt quantity was in excess of 10 grams of malt per 100 grams of amylopectin.
A 0 RUN I A 0 RUN 2
5w a
Vol. 40, No. 1
COMMERCIAL APPLICATION OD DATA
Figure 5.
Effect of pH on Hydrolysis of ,corn Amylopectin by Barley Malt Hydrolysis time 1 hour, temperature 55’ C.
C. be used during the hydrolysis step, further hydrolysis during fermentation should be easily achieved, particularly since the 55 C. hydrolysis temperature should leave more amylase available to act during fermentation. EFFECT OF HYDROGEN IONCONCENTRATION ON MALT HYTo determine the effect of pH DROLYSIS OF CORNAMYLOPECTIN. on the conversion of corn amylopectin by malt, 1% amylopectin dispersions buffered a t various pH levels with buffer solutions containing varying ratios of citric acid and dibasic potassium phosphate (3)were converted for 1 hour with a small quantity of malt extract in one series and a large excess in another. The results are shown in Figure 5. Conversions conducted at pH values in the range studied (pH 4.6-6.3) were not greatly affected by changes in pH. With a large excess of malt (70 grams per 100 grams of amylopectin) the optimum pH range for the cmveriion was 5.0-5.3; with a relatively low quantity of malt (10 grams per 100 grams of amylopectin) the optimum range was slightly higher, pH 5.3-5.6. EFFECTOF RATIOOF BARLEYMALTTO AMYLOPECTIN ON HYThe effect of malt quantity (based DROLYSIS OF AMYLOPECTIN. O
In distillery practice where it is desired to use as small a quantity of malt and allow as short a conversion time as possible, the ideal combination for malt hydrolysis would seem to be approximately 12-15 grams barley malt (before extraction) per 100 grams amylopectin, a conversion time of 15 minutes, and a conversion temperature in the range 53-57’ C. (Corn contains approximately 50 grams of amylopectin per 100 grams of corn.) Further studies on the action of different barley malts and various types of mashes would be necessary before any general rule could be established. The data presented here are useful in showing in a general way the effectof malt quantity and in showing that the rate of malt conversion of amylopectin is slow after the first 15 minutes. ACKNOWLEDGMENT
The authors wish to express their appreciation to M. C. Brockmann and A. L. Back for contributions t o this work. LITERATURE CITED
Am. Assoc. Cereal Chem., “Cereal Laboratory Methods,” 4th ed., pp. 94-6 (1941). (2) Bates, F. L., French, D., and Rundle, R. E., J . Am. Chem. Soc.,
(1)
65, 142 (1943).
Clark, Mansfield, “Determination of Hydrogen Ions,” p. 214, Baltimore, Williams and Wilkins, 1928. (4) Hanes, C. S., Can. J . Research, B13,185 (1935). (5) Hanes, C. S., New Phytologist, 36, 101 (1937). (6) Xerr, R. W. and Severson, G. M., J . A m . Chem. SOC.,65, 194 (3)
(1943).
ac
(7)
Kneen, E. and Sandstedt, R. &I., Cereal Chem., 18, 237-52 (1941).
7c
Meyer, K. H., “Advances in Colloid Science,” p. 173, New York, Interscience Publishers, Inc., 1942. (9) Meyer, K. H., Wertheim, M., and Bernfeld, P., H e h . Chim.
Z
0 6C
(IO) Myrback, K., Biochein. Z., 297, 160, 172 (1938). (11) Samec, M., and Waldschmidt-Leitz, E., 2. physiol. Chem., 203,
v, c5
(12)
Sandstedt, R. M., Kneen, E., and Blish, M. J., Cereal Chem., 16
(13) (14) (15)
Schoch, T. J., J. Am. Chem. SOC.,64,2954 (1942). Schoch, T. J., Ibid., 64, 2957 (1942). Shaffer, P. A. and Hartmann, A. F., J . B i d . Chem., 45, 379
(8) b\*
Acta, 23, 868 (1940).
I
16 (1931).
W
712-23 (1939).
>
z 5c
u0
(1921).
I-
5U 4
(16) Stiles, H. R., Peterson, W. H., and Fred, E. B., J . Bact., 12,
aQ
RECEIVED May 2, 1946. Presented before the Division of Sugar Chemistry CHEMICAL SOCIETY, and Technology at the 109th Meeting of the AMERICAN Atlantic City, N. J. Condensed from a thesis presented by T. Munsey Back to the faculty of the Graduate School of the University of Louisville in partial fulfillment of the requirements for the degree of master of science, June 1945.
428-35 (1926).
2 3c 2c
Paper Capacitors Containing Chlorinated Impregnants-Correction
IC
0 PARTS DRY MALT (BEFORE E X T R E T I O N j T O 100 PARTS AMYIBPECTIN
Figure 6.
Effect of Barley Malt Quantity on Hydrolysis of Corn Amylopectin Hydrolysis pH 5.5, temperature 5 5 O C .
In the paper entitled “Paper Capacitors Containing ChloriENC.CHEM.,39,1457 nated Impregnants” [McLean, D. A., IND. (1947)j the second sentence in the third paragraph of the second column should read: The shop process was designed to attain moisture contents of less than 0.05%. On page 1461 in Table IV the words “from Table 11” should be omitted from the heading “After Exposure, (from Table 11) ,”
