I N D U S T R I A L A N D ENGINEERING CHEMISTRY
March, 1923
amount, of gas obtained in the first fraction with a low vacuum in the case of raspberries is d u e t o trapped air. The processes used in the canning industry lend themselves conveniently to the exclusive use of boiled water. I n many factories it has been the custom to boil the water used for canning. This should be adopted in all factories.
RESPIRATION OF FRUITS AND VEGETABLES The active respiration which takes place in fruits and vegetables tends to keep down the amount of dissolved oxygen in them, and also to leave the nitrogen, which is less soluble than oxygen, t o fill the interstices. We have made determinations on certain fruits and found them practically free from oxygen, while in others we have found the gases to have practically as high oxygen content as the atmosphere and the total gas to be over one-fourth the volume of the fruit. We have found that green lima beans and peas (unbroken seeds), green corn cut from the cob (broken seeds),
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carrots (tubers) scraped and cut into disks, and cabbage (leaves) cut into slaw, if covered with an equal weight of water saturated with atmospheric oxygen, will, a t room temperature, not only contain no oxygen themselves, but will have extracted all the oxygen from the water also a t the end of 2 hrs. No examination was made for shorter periods. The possibility should not be overlooked, however, t h a t such active respiration might result in a more destructive medium, perhaps by an increased oxidation potential or similar condition. If this does prove to be the case, it suggests the possibility of preparing a more favorable condition for the protection of vitamin C, by allowing respiration for a time in an atmosphere of nitrogen. A study of this question and its application to canning is contemplated. The gases in fruits and vegetables can readily be replaced b y another gas by subjecting them to a vacuum and releasing the vacuum with the desired gas, but diffusion is quite rapid in some cases and subsequent exposure to the atmosphere must be avoided.
Estirnation of Caramel in Sugar Products-Criticism
of the Ehrlich Method’
By George P. Meade CUBAX-AMERICAN SUGARCo., CARDENAS, CUBA
HRLICH’S method for the colorimetric estimation of caramel in sugar products is described by Brownet as follows : Saccharan, one of the component parts of caramel, is made by heating sucrose to 200 O C. in an oil bath under vacuum, and then extracting with hot methanol. The residue is then dissolved in hot water, evaporated, and ground to an amorphous powder, the powder representing about 20 per cent of the original sucrose. Ehrlich says that saccharan is not precipitated by lead subacetate; therefore, the coloring matter remaining in any lead-clarified filtrate is due to saccharan, which can be estimated by color comparison with a standard saccharan solution. The amount of sucrose that has been destroyed by heat will be approximately five times the amount of saccharan determined. All attempts to use this method on solutions containing known amounts of caramel or saccharan proved it to be valueless. A typical case follows: Five grams of saccharan, made according to Ehrlich’s directions, were dissolved in one liter of water, and a part of this strong solution was diluted 1:50 as a standard for color comparison. Two and one-half normal weights of a dark molasses were dissolved and made to 500 c ~ . and , 100-cc. portions were pipetted into each of three 200-cc. flasks. To the first no saccharan was added, to the second 20 cc. of the strong solution (0.1 g. saccharan), and to the third, 60 cc. (0.3 g. saccharan). To each were added 20 cc. of 54“ Brix subacetate of lead solution-an excess of lead being purposely used-after which all were made to the mark and filtered. Quantitative color determinations were made on each of the three filtrates by comparison with the standard saccharan (dilute) which contained 0.0001 g. per cc. The amount of saccharan contained in each filtrate was as follows:
E
PREPARATION OP M O L A S SSOLUTION ~S 100 cc. molasses plus 20 cc. lead t o 200 CC.. 100 cc. molasses plus 20 cc. saccharan solution plus 20 CC. lead to 200 cc 100 cc. molasses plus 60 cc. saccharan solution plus 20 cc. lead to 200 CC... .
. ... . . . . . ..... . ..
-
1 Presented
Saccharan in Total Filtrate by Comparison with Standard Saccharan (Ehrlich’s Added before Method) Lead G. G.
Per cent Added Saccharan Precipitated by Lead
0.0175
None
....
0.0220
0.1
95.5
0.0375
0.3
93.7
before the Division of Sugar Chemistry at the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. 8 “Handbook of Sugar Analysis,” p. 467.
When 5 cc. more of lead were added to the three filtrates, the color of all three after filtration was practically the same, showing that all the saccharan is precipitated if sufficient lead is added. Caramel was prepared in three different ways-by heating sucrose to constant weight at 180’ C., by heating to 190” C., and by heating to 200’ C. in a vacuum,2 and all behaved the same as the saccharan when added in known amount to molasses solutions and then clarified with lead. In every instance the lead removed a part or all of the color, depending on the amount of lead used. Saccharan behaved identically like the various caramels made in different ways, so hereafter caramel only will be referred to, with the understanding that saccharan is included. The following work with caramel shows why the Ehrlich method is of no use: Caramel dissolved in recently boiled, distilled water is not precipitated by lead subacetate. However, when any of the common deleading agents are added t o the caramel solution before clarifying with lead, the resulting precipitate carries down with it all, or nearly all, of the color. Sodium carbonate also acts in this way if not present in t o o great excess. With hydrochloric, sulfuric, or phosphoric acids, the lead removes little, if any, of the color. Caramel dissolved in a tap water high in solids was almost completely removed by the addition of lead. Apparently, anything that will set up a voluminous precipitate with lead will remove part or all of the caramel from the solution, provided the reaction of the filtrate is not too strongly acid or alkaline. A series of experiments using normal lead acetate instead of lead subacetate proved that the normal lead acts in the same way as the basic lead-i. e., caramel is removed from the solution by the normal lead, provided material is present which sets up a precipitate with the lead. Ehrlich evidently assumed that the caramel in a sugar solution would not be removed by lead, because he found that the lead did not precipitate saccharan in pure solution. The work here reported proves that the ordinary impurities which are found in molasses and dark-colored sugar products, when precipitated by lead subacetate or normal lead acetate, carry down with them all or nearly all of the caramel in the solution, and that therefore the method of Ehrlich is valueless.
