November, 1929
INDUSTRIAL A N D ENGINEERING CHEMISTRY
of the diffused spray type. Cold-storage Stayman-Winesap apples were used in all the tests. These had received five cover sprays of lead arsenate, 2.4 grams per liter (2 pounds to 100 gallons). Unfortunately, a spreader had been used in the last three sprays. This protected the lead arsenate particles somewhat from the action of the solvent. It also caused excessive deposits of the arsenical to collect in the stem end of part of the fruit and made it difficult to select evenly sprayed samples. Consequently, a small area around the stem was cut away and discarded before analysis. Especial care was taken, however, to pick fruit for the tests that appeared evenly sprayed. All tests were carried on a t 8" C. Table I11 shows the amount of residue on the fruit after the various treatments indicated. T a b l e 111-Cleaning Effectiveness of Different C o m b i n a t i o n s of S o l v e n t s W h e n Used in a C o m m e r c i a l W a s h i n g M a c h i n e CONCEN- Asz03 RESIDUEO N FRUIT TRATION AFTER T R E A T M E N T
SERIES
Per cent Gram per kg. Grains per Ib.
3 (a) (b) (c)
4 (a) (b) (c)
5 (a) (b)
Hydrochloric acid Hydrochloric acid Sodium sulfate Hydrochloric acid Sodium sulfate Hydrochloric acid Hydrochloric acid Ferrous sulfate Hydrochloric acid Ferrous sulfate Hydrochloric acid Hydrochloric acid Sodium chloride Hydrochloric acid Sodium chloride Hydrochloric acid Hydrochloric acid Copper sulfate Hydrochloric acid C o.. m e r sulfate Unwashed check Unwashed check
0.16 0.16
1.201 0.33 1.201 0.1s 0.18 1.301 0.37
0,0024 0.0015
0.017
0.0011
0.008
0,0027 0.0017
0.019 0.012
0.011
1.301
0,0014
0.010
0.40 0.40
0.0034 0.0026
0,024 0.018
i:::]
0.0013
0,009
0.18 0.18 l,oof
0.0026 0.0023
0.018 0.016
0.35
0.0020
0,014
.. ..
0.0093
0.065 0.041
0.0068
1135
All of the different combinations showed more effective cleaning of the fruit than was obtained with hydrochloric acid alone. General Considerations Before definite recommendations can be made regarding the commercial use of any of the combined solvents, sufficient commercial tests must be carried out to confirm these studies and to ascertain what proportions of the different compounds will be most effective. From the laboratory studies the combination of sodium sulfate and hydrochloric acid appears most promising. Sodium sulfate is a neutral salt and should not cause injury to the fruit. It can be washed off easily in the water wash. I n combination with hydrochloric acid the concentration of the latter may be reduced materially. This would reduce danger of injury to fruit. This combination would also decrease costs. In the Pacific Northwest 38 decaliters (100 gallons) of 1.0 per cent hydrochloric acid costs about 78 cents. If 0.5 per cent hydrochloric acid with about 4.5 kg. (10 pounds) of sodium sulfate could be substituted for the 1.0 per cent acid, 38 decaliters (100 gallons) would cost 51 cents. From the laboratory studies it may be concluded that sodium chloride, copper sulfate, ammonium chloride, and certain other salts when combined with hydrochloric acid may be found practical under certain conditions. None of the combinations probably would cause injury to the fruit. Their costs, however, would be higher. On the other hand, combinations of iron salts with hydrochloric acid could not be used. Hartman ( 1 ) has observed that this mixture will cause discoloration and other injury to the fruit, which would preclude its use. Literature Cited ( 1 ) Hartman, Unpublished data of the Oregon Agricultural Experiment
Although the washing tests were made under very unsatisfactory conditions, the results confirm the laboratory studies.
Station. (2) Robinson and Hartman, Oregon Expt. Sta., Bull. 226. (3) Robinson and Hartman, I b i d . , 234.
Effect of Temperature and Time of Heating on Extraction of Color from Red-Juice Grapes' M . A. Joslyn, H. B. Farley, a n d H. M. Reed FRUITPRODVCTS LABOSATORY, UNIVERSITY
I
K T H E preparation of red grape juice the crushed and
stemmed grapes are heated before pressing to extract the color, which is located principally in and near the skins. The anthocyan pigments responsible for the color are present in such a condition that they are only slightly soluble in the cold juice although they readily and quickly dissolve in the heated juice. The temperature and time of heating also influence the quality of color in the resulting juice. Long heating a t high temperatures not only imparts an objectionable cooked flavor to the juice, but also renders it astringent by extracting an excessive amount of tannin from the seeds and skins. Although the effect of time and temperature on the extraction of color from the red-juice grapes was early realized, an extensive study of these factors was not made. At any rate such a study is not reported in the literature. The qualitative effect of these factors was studied by Hartmann and Tolman ( 4 ) and Cruess (3). Hartmann and Tolman point out that 1
Received June 4, 1929.
OF
CALIFORNIA, BERKELEY, CALIF.
for Labrusca varieties 150" F. (65.5" C.) should not be exceeded in heating the crushed and stemmed grapes because of extraction of an excessive amount of tannin from the seeds a t higher temperatures. I n experiments with Vinifera varieties in California, Cruess found that the color will dissolve in the juice slowly a t 105" to 130" F. (40.5" to 48.9" C.) and almost instantly a t 160" t o 170" F. (71.1" to 76.7" C.). Best results were obtained by heating the crushed grapes to 120-130" F. (48.9-54.4" C.) for 8 to 12 hours, although good results were obtained by heating t o 160 O F. (71.1" C.) for 5 minutes only. I n the writers' investigation a preliminary study was made on the effect of time and temperature of heating on the intensity of color and tannin content of red grape juice extracted from the Petite Sirah, a Vinifera variety of red grapes grown in California. Experimental The grapes were crushed in an apple grater and the stems removed by hand. Three-hundred-gram portions in dupli-
INDIISTRIAL A S D ESGI*VEERISG CHE-VISTRY
1136
cate of the crushed grapes well mixed with the extracted juice were placed in Pyrex beakers and heated for exactly 2 minutes a t 40", SO", BO", 70", 80", go", and 100" C. To decrease the time necessary for bringing the crushed grapes from 20" C. t o the desired temperature, the samples were rapidly brought t o temperature in a water bath held a t 90" C. and then transferred to another water bath held at the desired temperature. The 90" and 100" C. samples were brought to
Yol. 21,
xo. 11
used a Hess-Ives tint photometer. The color of the sample\ placed in h i m . cells was determined by this instrument using transmitted light. The instrument is accurate to one degree. As it was very difficult to match the blue field and the scale reading for that field mas in most cases so low that the error in reading wab very large, the use of the blue screen wab abandoned. The red, green, and blue-green screens werr used. Of these the red gave the more reproducible and mor? easily matched field. The permanganate reducing matter present in the juice. was determined by a slight modification of the official method ( 1 ) and was expressed as tannin and coloring matter or simply as grams tannin per 100 cc. of the juice. The method used was t h a t for tannin and coloring matter in wine. As no alcohol was present in the juice, dealcoholization hy evaporiition was not resorted to. Discussion of Results
Figure 1-Effect
of Color Screens Used on Intensity of Color
temperature by heating with a shielded gas flame. The total time of heating \vas but slightly over 4 minutes. To insure uniformity of temperature during preheating the crushed grapes were stirred very rapidly. During this heating there was a slight but comparatively negligible concentration of color due t o evaporation. After removal from the bath the samples were chilled in ice water and the juice mas expressed by hand through several layers of cheesecloth. I n another series large portions of the crushed grape* were heated in an aluminum kettle held in a water bath a t 40", SO", BO", and 70" C., respectively. The entire mass of grapes was brought to temperature as above. Samples of crushed grape; and juice were withdrawn a t various time intervals. chilled, and the juice expressed as above.
The heated samples contained, in addition to a red pigment, a violet t o dark purple pigment whose concentration increased much more rapidly than that of the red pigment. This effect is evident from an examination of Figure 1, in which thc change in color intensity, expressed as units of color after the manlier of Jleade and Harris (.?). is shown as a function of hoth temperature or time and the color screen used. The initial color of the unheated juice is shown as the ordinates on the extreme left-hand side and is joined to the other readingby a dotted line. As the values for the red screen were more reproducible and accurate and the color of the red juice is due in great part t u the red pigments, in subsequent graphs the effect of time and temperature on the extraction of red pigments only ishowl.
a
Figure 3-Effect
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o
z
o
m
I
I
ClNUTEJ
~
l
(
i
b
o
m
m
w
r
m
Figure 2-Effect of Time and Temperature of Heating on Extraction of Red Color
.
Before examination, the expressed juice was clarified by filtration through filter paper to remove suspended material. Owing t o the change in both concentration and nature of the color in the heated juice, an ordinary color comparator such as the Klett could not be used satisfactorily in comparing the intensity of color in the samples, and it was necessary to use an instrument provided with color filters. The writers
0
NlNUIES
5
l
/PO
of Time and Temperature of Heating on Tannin Content
Figure 2 shows the effect of time and temperature of heating on the extraction of red color. The numbers 40, 50, 60, and 70 refer to the temperatures a t which the grapes were heated for the time shown. The graph marked temperature is a reproductioii of that shown in Figure 1 replotted here for comparison. For this graph the abscissas are taken as temperatures in degrees Centigrade arid not time in minuter. The initial color concentration of the unheated juice is show11 as the ordinate a t 20" C. There is but a slight increase in color in raising the temperature from 40" to 50" C., a more rapid increase from 50" to 70" C., verylarge from 70" to 90" C., and from 90" t o 100" C. there is apparently no appreciable change. However, since the scale reading a t the higher temperatures is comparatively cmall, an appreciable error in reading enters. For this reason not much significance should be attached to the constancy of
Sovember. 1929
11YDUSTRIAL A 9 D ESGIn'EERlNG CHEMISTRY
color readings for 90" and 100" C. It is evident that a point of inflection occurs a t about 70" C., the temperature a t which the color was found "to flow" by Cruess ( 3 ) . At 40" and 50" C. the color increases but slowly with time during the first hour of heating; a t 60" and 70" C. there is :t more rapid increase in color with time, but this increase begins to fall off after 20 and 25 minutes, respectively. The color obtained by heating a t 70" C. for 5 minutes corresponds to that obtained for 18 minutes a t 60" C., about 40 iniiiutes a t 50" C., aiid 60 minutes a t 40" C., and about 80" C. for 2 minutes. The curves shown in Figure 3 for the tannin content of thc juice are somewhat Gnilar in shape to those for intensity of color. DifTerences occur in the plot for the change in tarinin content x i t h time IJf heating a t 60" C., and for change 111 tannin content with temperature of heating. These are not directly comparable with those for color intensity. The tannin coiiteiit of the lot of Petite Sirah grape< used in these tests is c o n d e r a b l y lower than the t a m I I content ot grape juice rqmrtecl in the literature (?, 61.
1137
Conclusions (1) Heat,iiig to extract color from red-juice grapes affects both the concentration and the nature of color. (2) The color intensity increases slowly as the temperature is raised from 20" to 70" C., and rapidly from i o " to 90" C. (3) The color intensity increases more rapidly wit'li time at' 70" and 60" C. than a t 40" or 50" C. (4) The tannin content of the juice varies somewhat similarly with time and t,emperature of lieat,ing, as does the color intensity.
Literature Cited fl) Assocti. Oficial Agr. Chem., Methods, p. 3 6 i (1925). f2) Caldwell, J . ilgr. Research, 30, 1133 (1928). (3) Cruess, University of Caliiornia Expt. Sta., Bull. 331 (1920), "Commercial Fruit and Vegetable Products," p. 321, McGra\v-Hill Book CO .
1024. (4) Hartmann and Tolman, U. S . Dept. A g . , Bull. 656. ( 5 ) Meade and Harris, J. IND.ESG. CHEM.,12, 686 (1920). (6) Soyes, King, and Martsolf, J . .tssocn. O 3 r i a Z :Igv. C h e ? 6, ~ 1 9 i (14221.
Fatty Acids of Filter-Press Cake from Spent Soap Lye' B. W. Howk and C. S. Marvel
I
N T H E purification of spent soap lye fur the recovery of
glycerol ( 2 ) some American manufacturers use the Gerber process. This method consists in neutralizing the spent lye with hydrochloric acid and treating with ferric chloride t o precipitate as the iron salts the fatt? acids who.e sodium salts have remained in solution in the lye liquors. I n the present practice these iron salts are filtered off on a filter press and discarded. The exact composition of this filter-press cahe aiid the nature of the fatty acids that are present do not beem to have been carefully investigated. I t is obvious from the source of this material that i t should contain the salts of some of the lower fatty acids. Since there is some interest in the salts of these acids, an investigation of this crude filter-press cake was undertaken in order to determine whether or not i t would -ewe as a source for them. Preliminary Analyses and Tests
The filter-press cake2 was analyzed for moisture by drying in a vacuum oven at, 100" C., for total ash by ignition, and total nitrogen by the Kjeldahl method. These results are as follows: moisture 55.5, ash (dry basis) 43.1, and nitrogen (dry basis) 0.19 per cent. This indicated that the filter-press cake cont'ained very little protein material. Treatment of the filter-press cake with either hydrochloric or sulfuric acids liberated water-insoluble fatty acids, which were partly volatile with steam. From 500 gmms of crude filter-press cake by treating with excess 10 per cent sulfuric acid there were obtained 35 grams of mixed water-insoluble ncids. Separation of the acids was not satisfactory, so direct esterification of the product followed by fractionation of the mixed esters was next tried. Received June 7, 1929. T h e filter cake was furnished b y the Armour Soap Works. Victor Cofman had reported that he was able t o isolate esters of the lower fatty acids from this material hut that he had not made a thorough investigation of the material.
Esterification and Fractionation of Esters
Two kg. of the undried filter-press cake and 1.5 liters of ethyl alcohol wcre placed in a 5-liter, round-bottom flask attached to a good reflux coiideiiser and fitted with an efficient mechanical stirrer. To this suspension about 300 graills of concentrated sulfuric acid were added, and the mixture was then boiled under reflux for ahout 7 hours. The material in the flask became semi-solid. About 2 liters of benzene mere added and the mixture wa3 filtered in a basket centrifuge to remove the suspended matter. This solution was distilled under ordinary pressure to remove the water, benzene, and alcohol. The r e d u a l black liquid weighed about 120 grams. This material was then carefully fractionated three times under reduced pressure, in order t o separate the various fractions. A considerable amount of black tarry residue was obtained in the first didillation. The final fractions collected are listed in Table I. Table I-Fractions
from Mixed Ethyl Esters of Filter-Press Cake Acids
FRACTION 1 2 3 4
130ILIXG P O l N T A T 4-6 M M
c.
71-73 73-93 93-98
9x-I 14
5 6
Grams 11.4 0.8
5.3
1 3 8.8
0.7
7
6.5
0.5 15.7
8 9
10 11 12
WEIGHT
2.0 28.0 Rebidue
Fractions 1, 5, 7 , 9, and 11 seemed to be reasonably pure compounds. The boiling points agree very closely with those of the ethyl esters of caprylic, capric, lauric, myristic, and palmitic acids, respectively.
1 9
Identification of Esters
The ester fractions Tvere identified by comparison of their boiling points, refractive indices, and densities with those
