4. There could be obtained from the fermented melon juice a n acetic acid solution that was about I . 7 5 per cent. pure acid. 5 . The reducing sugars, by the Fehling titration method, were found t o run near 5 . 5 per cent. of the juice. By the polariscope they were found in a smaller quantity usually. We are unable to explain the fact t h a t the two methods do not run closer together. I t would seem that the lead acetate defecation did not take out all the substances in the juice that might reduce Fehling's solution. 6. Usually more than 1.00 per cent. of the juice was sucrose. DEPARTMENT OF CHEMISTRY,INDIANA VNIVERSITY, BLOOMINGTON.'
THE DETERMINATION OF BENZALDEHYDE IN MARASCHINO CHERRIES AND MARASCHINO LIQUEUR. B y A. G. WOODMAN AND LEWISDAVIS. Received April 9 , 1912.
Comparatively recent investigations by food authorities into the composition of Maraschino cherries, and the possibility of distinguishing the genuine product from artificial imitations, have made desirable a method for the determination of small amounts of benzaldehyde, a common ingredient of food products of this nature. For this purpose the method of determining benzaldehyde as the phenylhydrazone, originally proposed by Fischerr and adapted t o the examination of almond extracts by Denis and Dunbar,' suggested itself. I t was evident almost from the beginning, however, t h a t this method, although satisfactory for the comparatively large amounts (0.I gram) of benzaldehyde present in almond extracts, is not suitable for quantities as small as five milligrams, as found in Maraschino cherries. This is clearly shown in Table I, which gives the results obtained by the Denis and Dunbar method on known amounts of redistilled benzaldehyde dissolved in 95 per cent. alcohol. Blank determinations to correct for the effect of the reagent were made a t the same time. The precipitate obtained in each case in the blank determination was of a gummy, resinous character, as was true also of the determinations involving the smaller amounts of benzaldehyde. TABLEI.-RESULTS OBTAINEDBY .Mg. benzaldehyde taken. 29.3 4.965 4.965 4.740 9.480
Mg. PPt. obtained. 53.7 9.7 8.8 9.1 16.3
THE
DENISABD DUNBARMETHOD.
Equivalent mg. benzaldehyde. 27.4 5,248 4.761 4.922 8 818
Per cent. of Mg. ppt. in blanks. theory. 93.61 105.7 95.9 104 . O 93.09
3.1 3.0 3.0 3.9 3.9
As shown in the table, the lowest value for the blanks was three milligrams, or almost 30 per cent. of the total weight of precipitate when five milligrams of benzaldehyde were present. The results differ quite widely, some being above and some below the theoretical value. Z.anal. Chem., 26, 230 (1885). THISJOURNAL, 1909, 2 5 6 . .
Further study of the method as applied to small amounts of benzaldehyde showed that the precipitation was markedly affected by several distinct factors. A high percentage of alcohol retarded or even prevented the precipitation, while too little alcohol tended to make the precipitates gummy instead of crystalline. The best results were obtained when the alcohol amounted t o about ten per cent. b y volume. I t was found also that the weight obtained in the blank determinations was proportional to the length of time t h a t the solutions stood after adding the reagent and before filtering, being reduced from 3 .o milligrams to 0 . 3 milligram for half a n hour's standing. The character of the precipitate varied also with the length of time that the solution stood, being much lighter in color for the shorter time. The results obtained with known amounts of benzaldehyde by precipitating and allowing the solution t o stand for half an hour were, however, too low, showing incomplete precipitation. I t was found possible, however, t o secure complete precipitation in ten minutes by shaking the solution in a stoppered flask after the addition of the reagent. About 95 t o 97 per cent. of the theoretical values were obtained with five milligrams of benzaldehyde, while the weight of the blank did not exceed 0 . 5 milligram for I O cc. of reagent. Some of the results obtained under these varying conditions are shown in Table 11. TABLEII.-EFFECT
OF
VARYINGCONDITIONSON BENZALDEHYDE.
THE
PRECIPITATION OF
-4 s Eu w8 k 3 k
7.097 7.097 7.097 7.097 5.359 5.359 6.780
12.10 12.00 12.00 11.70 11.70 11.40 11.80
6.546 6.492 6.492 6.330 6.330 6.167 6.384
6.780
11.60
6.276
5,707
9.70
5.248
5.707 6.690 6.690 6.700 6.700
9.20 10.60 10.80 10.80 10.80
4.977 5.735 5.842 5.842 5.842
per cent. alcohol. per cent. alcohol. per cent. alcohol. per cent. alcohol. 1 per cent. alcohol. 1 per cent. alcohol. 10 per cent. alcohol and 3 0 mg. acetaldehyde. 9 2 . 4 3 10 per cent. alcohol and 3 0 mg. acetaldehyde. 9 1 . 9 6 10 .per cent. alcohol shaken 5 minutes with reagent. 8 7 . 2 2 10 per cent. alcohol stood over night before adding reagent. 85.72 8 7 . 3 4 10 per cent. alcohol, total volume 200 cc. 87.20
92.26 91.49 91.49 89.21 118.1 115.1 94.17
20 20 30 30
87.20
To summarize these results briefly: The amount of alcohol present during the precipitation should be between 8 and 1 2 per cent. by volume. With 2 0 per cent. or more, the precipitation is incomplete, as might be predicted from considerations of solubility, no precipitation taking place a t all with 5 0 per cent. of alcohol present. Too small a n amount of alcohol tends to cause decomposition of the reagent, with consequent too high values for both the blanks and the benzaldehyde determinations. The presence of acetaldehyde has practically no effect on the precipitation, which is borne out by the fact that when acetaldehyde was present the blank determinations gave an increase of only 0.1 milligram over the 0 . 5 milligram usually obtained. Since the other alde-
Aug., 1912
THE JOURSAL O F I N D U S T R I A L A N D E.VGIA-EERING C H E i V I S T R Y .
hydes of this series are closely related to acetaldehyde in their chemical properties, it may fairly be assumed that the presence of aliphatic aldehydes, which are the ones most likely t o be present in liqueurs like Maraschino, exercises no deleterious effect. On account of the relative solubility of benzaldehydephenylhydrazone, the volume of solution for precipitation should not exceed I I O cc. From the above considerations and based on the experience gained in more than one hundred determinations on known amounts of benzaldehyde, the following procedure is recommended for its determination in Maraschino cherries and Maraschino liqueur. Dilute I O O cc. of the liquor from Maraschino cherries, or 50 cc. of Maraschino liqueur t o 140 cc. in a 500 cc. flask and distil I I O cc. Determine approximately the alcohol in the distillate, filtered if necessary, by the pycnometer or immersion refractometer. Transfer I O O cc. of the distillate to a 300 cc. Erlenmeyer flask and add alcohol or water, as may be necessary, so t h a t the solution shall contain approximately ten per cent. Of by Add I O O cc. of the reagent prepared as directed below, stopper tightly with a rubber stopper, and shake vigorously for ten minutes. Remove any precipitate adhering to the stopper, and filter on a tared Gooch crucible, washing with cold water, and finally with about ten cc. of ten per cent. alcohol. Dry in a vacuum desiccator for 2 0 - 2 4 hours a t about 2 0 cm. pressure, or, if preferred, in a vacuum oben a t 7oo-8o0 C. for three hours. The precipitate should be kept from strong light as far as possible. A blank determination must be run a t the same time, deducting the weight obtained from t h a t of the precipitate. With our reagent this blank has been usually o . o o o j gram. The corrected weight of the precipitate, multiplied by 0.5411, gives the weight of benzaldehyde. Reagent.-Mix 3 cc. of glacial acetic acid with 40 cc. of water, add 2 cc. of phenylhydrazine, shake thoroughly, and filter the emulsion through several thicknesses of filter paper. The clear filtrate should be used immediately, as standing over five minutes gives a turbid reagent.
The be chemically free as far as possible from dark “lor and turbidity’ Frequent agitation O f the precipitate during ‘ltrathrough a rotary motion Of the flask prevents TABLEIII.-BENZALDEHYDE IN 10 PER CENT. ALCOHOL. Mg. . benzaldehyde taken. 5.359 6.363 6.595 48.30 81 .80 5.408 8.230 9.930 81.12 81.12
Mg. ppt. obtained (corrected). 9.5 11.5 11.7 86.8 146.7 9 5 14.6 17.6 144.8 145 .O
Equivalent benzaldehyde. 5.140 6.212 6.330 46.96 79.38 5.140 7.900 9.521 78.34 78.45
Per cent. of theory 95.90 97.77 95.98 97.23 97.03 94.99 95.98 95.90 96.58 96.72
it from sticking t o the sides. The determination of the benzaldehyde in the distillate should be carried out n-ithout delay to prevent loss by oxidation.
589
The method can be applied to the determination of benzaldehyde in almond extracts, using I O cc. of the extract diluted to I O O cc. with water, and I j cc. of the reagent. ’ Typical results on known amounts of benzaldehyde by this method are shown in Table 111. The first six of the results in the table were obtained by direct determination on solutions of pure benzaldehyde. The remaining ones were distilled as directed in the procedure. Experimental evidence has shown t h a t these dilute solutions of benzaldehyde can be distilled without material oxidation. Distilling in a current of carbon dioxide was tried b u t found to offer no advantage. The presence of considerable amounts of reducing sugars and sulphurous acid did not appreciably affect the distillation or determination. The benzaldehyde content of some of the “Maraschino Cherries” and “Maraschino” liqueur on the market is shown in the following table: TABLEIV.-BENZALDEHYDE CONTENT
OF
COXMERCIAL
S.4XPLES O F
CHERRIES.
Brand.
Alcohol by volume.
“Rosebuds”. . . . . . . . . . . . . . . “Touraine”. . . . . . . . . . . . . . . . . “Magnolia” . . . . . . . . . . . . . . . . Dandicolle & Gaudin. . . . . . . . “Regina”. . . . . . . . . . . . . . . . . . “Dupont” . . . . . . . . . . . . . . . . . “Bigarreaux” . . . . . . . . . . . . . . . Dalidet & C o . . . . . . . . . . . . . . . Ginter C o . , . . . . . . . . . . . . . . . . “Percer” . . . . . . . . . . . . . . . . . . Middleby C o . . . . . . . . . . . . . . . .
0,O
0.0 0.0
2.09 1.73 4.97 4.27 7.96 0.0
6.19 0.0
Corrected Benzaldehyde. wt. of Mg. precipitate. in 100 cc. 8.70’ 5.177 53 ,001 31.54 76.54 128.60’ 38.30 22.79 31.70 18.87 53.90 32.07 20.40 14.29 14.30 8.509 10.58 16.00 60,60 36.07 6.900 4.106
MARASCHINO.
G. Luxardo . . . . . . . . . . . . . . . 32.60 ... 3.57 Richelieux . . . . . . . . . . . . . . . 25.94 ... 17.02 Mane Brizard & Roger. . . . . . 28.97 ... 0.0 Cusenier (cherry liqueur) . . . . 32.63 ... 12.01 Cusenier (Maraschino). . . . . . . 19.00 ... 0.0 Nuyens et Cie. . . . . . . . . . . . . 24.78 ... 1.78 H.Shufeldt & Co., Peoria, Ill. 30.60 ... 41.3 In the case of some samples which contained extract of syringa, the precipitate was colored orange-red, but was calculated as benzaldehyde.
’
Genuine Maraschino, apparently, has a very low content of benzaldehyde. Consequently, Maraschino cherries, which show a relatively large amount of benzaldehyde, are in all probability artificially flavored. Determinations of benzaldehyde on unflavored cherries have shown that more benzaldehyde would come from the cherries, themselves, than from genuine Maraschino added as a flavoring agent. HoweQer, the former does not exceed 3-4 milligrams per I O O grams of cherries. I n general, then, it might be said t h a t in a sample of cherries flavored with genuine Maraschino liqueur, the benzaldehyde, expressed in milligrams per I O O cc. of the liqueur, should not be more than two or three times the alcohol content, expressed in per cent. of volume. Samples containing practically no alcohol and above 20 mg. of benzaldehyde are evidently entirely artificial. MASSACHUSETTSINSTITUTE O F TECHNOLOGY, BOSTON.
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