-- 1923 June,
INDUSTRIAL AND ENGINEERING CHEMISTRY
Hydrogen-Ion Determination as a Methio Control’
623
f Refinery
By H. Z. E. Perkins 132 N.
P E T E R S ST.,
N E W ORLEANS, L A .
H I L E the condicondition prevents inverTechnical applications of the principles of hydrogen-ion detertion of the matesion from excess acid, and mination are not as yet extensive in sugar making. Pioneer work rial worked in a also prevents darkening of has been done by Brewster and Raines,e lo whom the author is color which is liable to occur sugar refinery may be tested indebted for suggestions. a t many points and its in alkaline solution. After The present paper records the result of studies recently begun, variation may be obfiltration through bone and is not in any sense complete. It is to be considered as in the black containing free calserved a t all stages, real nature of a preliminary report in establishing refining limits. control of aciditv and alkacium carbonate, the oH linity is exercised a t a few figure may sometimes rise points only. The important ones may be mentioned as follows: to 7.0. XJnder normal working conditions successive boilings and filtration do not reduce i t appreciably below Washilzg Plant. All raw sugar is washed here and the first 6.4. Whatever inversion takes place is produced by heat. separation is made between high and low products. Treating or Blowup Tanks. Here the washed sugar and the A sugar liquor above 90 per cent purity, showing a p H figure sirup washings are treated with phosphoric acid, lime, and dia- less than 6.2, is abnormal and requires investigation. tomaceous earth, preparatory to clarification. All this applies to sugar in process, where the material‘ Sweet- Water Reduction. The immense volume of washings in hand is not kept standing untouched more than 72 hrs. from the filter bags and presses and from the char filters makes a body of thin sugar solution always acid and extremely liable Tests of standing liquors and sirups have been made to see when deterioration begins to set in. First liquors and sirups to further souring. which had been boiled and refiltered, having a purity of 93 WASHINGPLANT to 98 per cent and showing a p H figure of 6.8, after 6 days’ standing showed little change-in no case being below 6.4. I n .the washing plant the raw sugar is mixed with water Sirups for soft sugars, from 90 to 93 per cent, showed some to the proper consistency. A portion of the mixing water tendency to sour, the p H value falling below 6.0 in some is sweet water. Milk of lime is also added. The magma cases. The color indicators found most useful were those is thus a composite of several elements-sugar, water, sweet of Clark and Lubs, several of them having overlapping ranges water, and lime. This produces a mixture whose condition which can be used to check one another. of acidity bears no simple relation to that of the original sugar. After separation in centrifugals, the sugar and sirup TREATING OR BLOWUP TANKS travel different ways. Sugar in process may be divided into two groups of maThe first of the secondary products is the green sirup from terials : the washing of the raw sugar. It is of all refinery materials the most unstable, consisting of all the most fermentable MAIN PRODUCTS-These include all highly crystallizable substances occurring in the cane, and is invariably in a state solutions light in color, of purity above 80 per cent, from which of more or less active fermentation. This sirup is sent to are obtained sugars for consumption. They can be tested both with the potentiometer and with chemical indicators. As a defecating tanks where it is treated with phosphoric acid, rule they act more quickly with indicators, and are often slug- lime, and diatomaceous earth. Here there is a direct relagish with the potentiometer, since neutral organic substances tion to the preceding state. The only change in the consisof high purity do not ionize to any extent and so do not supply a powerful electrolyte. These high-grade sugar liquors, having tency of the sirup is that produced by the defecating agents, one of which is acid and one alkaline. A part of the lime been neutralized with lime a t the beginning of the process and treated from time to time with a neutral defecant like diatoma- neutralizes the phosphoric acid, and the remainder combines ceous earth, hold their neutrality throughout. with the organic acids of the sirup, as well as with the gums SECONDARY PRODUCTS-These are the washings or centrifu- and other organic matters. Since the lime is not added to gal separations containing the less crystallizable substances excess it does not show ionization. It is considered good darker in color and of a purity below 80 per cent. They are too dark in color t o give satisfactory color reactions, but, being practice to keep the treated sirup on the acid side, showing better electrolytes, they are quite active when tested with the a pH figure of 5.0 to 6.0. potentiometer. They are less stable in composition, being a Zerban3 has shown that the neutralization of lime and acid composite of many organic substances, and are peculiarly liable with formation of insoluble compounds produces its clarifyto fermentation, with formation of organic acids and consequent ing effects by mechanical rather than by chemical means, ionization. since it matters little whether the lime compounds are formed A survey of the main products would begin with the melted by adding lime first or acid first. A neutral, insoluble comwashed sugar, or first liquor, and would observe the phe- pound is not to be regarded as ionized, so that chemical nomena of ionization which attend it thenceforth. Washed effects are here less important than physical effects. Pracsugar in solution of a density of 55” to 60’ Brix is quite stable tical sugar making, it is to be remembered, is only incidentally during the period of refining. The condition of safety is a chemical process. The main process is physical and mea p H limit of 6.4 to 6.8-just within the acid range. This chanical, and is only chemical in its testing and in its aberrations. 1 Presented before the Division of Sugar Chemistry at the 64th Meeting of the American Chemical Society, Pittsburgh, Pa,, September 4 t o 8, 1922. It is in this washed sugar sirup that we find the most con2 Trirs JOURNAL, 13 (1921), 1043; “Control of Reaction in Sugar-House tradictory phenomena. After treatment with phosphoric Liquors,” presented before the Division of Sugar Chemistry qt the 63rd
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Meeting of the American Chemical Society, Birmingham, A l a , April 3 to 7, 1922.
a “Clarification of Cane Juice without Chemical Treatment,” Louisiana State University, Bull 173.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
acid and final lime neutralization, we commonly have a good clarification with a PH of 5.0, or slightly Over* But sometimes a persistent cloudiness manifests itself, which is unresponsive to changes in application of the clarifying agents, even to the point Of neutrality. we have here an effect produced by colloidal matters which Seem to have a different electrical condition, preventing precipitation a t the ionization figure usually workable-that is, 5.0 to 6.0-and contiming in dispersion until a PH figure of 6.5 is passed. In what manner these colloids may be influenced by the state of ionization of the sugar solution, or what may be the witical point of precipitation expressed in these terms, is yet to be determined. Color indicators are impracticable in mixtures as dark colored as these. The average pH values of its reactions at various stages may be stated as follows: Green wash sirup After defecation and clarification (Upon 3 days' standing this may fall t o 4.0 or below) After bone-black filtration
3 . 6 to 4 . 0 5 . 0 to 5 . 6 5 . 6 to 6 . 0
Henceforth, through successive boilings and filtrations this sirup from washed sugar becomes as stable as the high-grade products-in fact, even more so as the final molasses stage is reached.
Vol. 15, KO. 6
SWEET-WATER REDUCTION The chief remaining by-product in the refining process is water, the immense volume of washings from the presses, and the bag and char filters. This in the thin state is as fermentable as washed sugar sirup. Upon concentration it shows many of the same characteristics, containing all the gummy and nitrogenoussubstances deposited by the raw sugar during clarification and deco~orization~Ad& tion of lime afterconcentration reduces acidity to a point within the acid range. vi^^ been subjected to repeated heating, it is partially sterilized and so sholvs a tendency to fermentationupon standing, A sweetwater concentrate in its several stages would show pH figures of the following range: After concentration After liming and defecation After bone-black filtration
4 . 8 to 5 . 0 5 . 0 to 5 . 8 5 . 4 to 6 . 0
The best sugar-refining practice tends to make active ionization a residual phenomenon. A working range throughout would be safe between p H 4.0 to 6.8, and need not exceed these figures. Color indicators will be found highly useful in testing high-grade sugar solutions, while the potentiometer will be best for secondary products.
The March of Hydrogen-Ion Concentration in .Bread Doughs'" By C. H. Bailey and R. C. Sherwood DIVISIONOF AGRICULTURAL BTOCNEMISTRY, MINNESOTA AGRICULTURAL EXPERIMENT STATION, ST. PAUL,MINX.
It is evident from the data accumulated that the hydrogen-ion concentration increases at a fairly uniform rate in bread doughs fermented underfixed conditions. I n terms of p H this increase appears graphically as an approximately straight line, within the time limits studied. I n a 4-hr. period the change in p H of laboratory straight doughs averages about 0.4I unit, and in commercial straight doughs about 0.47 unit. Increasing the temperature of the dough, as in the "proof" when the dough is finally molded info loaves and raised in the pan, accelerates the rate of increase in hydrogen-ion concentration. I n large straight doughs weighing about IO00 Ibs., the rate of change in p H is apparently somewhat more rapid than in the I-16. laboratory doughs. When phosphoric acid and acid phosphates are added to the dough, the hydrogen-ion concentration is increased thereby, and remains at a uniformly higher level throughout the fermentation period. Arkady does not appreciably agect the initial hydrogen-ion concentration of the dough, but causes it to increase
during fermentation at a much more rapid rate than when Arhady is not included in the dough. "Sponge" doughs, made with more than the proportion of water usual for straight doughs, increase in hydrogen-ion concentration at a somewhat more rapid rate than do the straight doughs. The higher hydrogen-ion concentration acquired by such sponge doughs when fermentedjor a fairly extended period is reduced on mixing the sponge with raw flour. The grade of flour bears an important relation to rate of change in p H of doughs, the high-grade or patent-flour doughs changing more rapidly in p H than low-grade or clear-flour doughs. It accordingly appears that in estimating the probable rate of change in hydrogen-ion concentration of bread doughs a number of variables must be consideredincluding grade of flour, consistency of the dough as determined by the relative proportion of water added, temperature of the dough, size or weight of the dough batch, and whether or not certain ingredients, such as Ark-ady, are included in the dough.
NUMBER of significant biochemical changes undoubtedly occur during the fermentation of bread doughs. There appears to be justification for listing at least the following:
(3) Alcoholic fermentation effected by the zymase of yeast. Zymase, while active in the juice of disintegrated yeast cells, is much more active in the living organisms. Hence, many substances which stimulate reproduction of the yeast cells or other processes of growth and life of the living yeast cell, simultaneously accelerate fermentation. The type of fermentation is controlled in a measure by the environment of the yeast cells, the oxygen supply being particularly significant in this connection. Chemical reactions involved in the conversion of glucose into carbon dioxide and ethyl alcohol are exothermic, thus releasing an appreciable amount of heat energy which serves to raise the temperature of the dough. This yield of heat energy is only about 3 per cent of the potential yield if the oxidation proceeds to completion, with carbon dioxide and water as the end-products. (4)Proteolysis, or hydrolysis of the gluten proteins. Frequent reference to such changes has been made in the literature, but no adequate data have yet been published t o indicate the extent of proteolysis in actual doughs or the conditions controlling the rate of change. The source of active proteases has
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(1) Diastatic activity of the flour and of active diastatic preparations such as malt extracts converting starch into maltose, which is indirectly available for fermentation. ( 2 ) Hydrolysis of the disaccharide sugars, sucrose and maltose, by the enzymes sucrase or invertase, and maltase into the fermentable monosaccharides glucose and fructose. Disaccharides are present either in the flour, in other dough ingredients, or, in the case of maltose, as a result of the activities of diastatic enzymes. Sucrase and maltase are contributed by the yeast, and their action is rapid when in contact with the appropriate sugars in solution. 1 Received September 11, 1922. 2 Published with the approval of the Director as Paper No. 342, Journal Series, Minnesota Agricultural Experiment Station.
