492
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
as before, t h e other treated with I cc. of I : I HC1 (this being approximately the amount of acid necessary t o neutralize the alkalinity due to basic lead ace, tate) before heating. It is quite evident t h a t a serious loss occurs if solutions of molasses clarified with excess of basic lead acetate are heated before adding acid, while if the alkalinity be neutralized prior t o heating all irregularities seem t o disappear. Further tests were made t o determine the permissible limit of initial temperature. I n all the following experiments the solutions to be inverted were first neutralized with I cc. of I : I HC1. EXPERIMENTS 8 A N D g showed initial temperatures between 70 a n d 60’ t o yield satisfactory results on 30 min. standing. EXPERIMENT A O -I final test was made t o cover the above range with a n inversion period of only 15 min. T h e safe limit of initial temperatures for waste molasses thus appears t o lie between 7 0 and 63’ for a I 5-min. inversion period. MODIFIED INVERSION METKOD
The modified inversion method proposed, based on t h e above experimental evidence, is as follows: Place 50 cc. or 7 5 cc. of the solution used for direct polarization in a 100-cc. flask (in case 50 cc. are used a d d 2 5 cc. water) and heat in a water bath t o 65’ C. Remove from bath, add I O cc. of a mixture of equal volumes HC1 (sp. gr. 1.188) and water, allow t o cool down spontaneously in air for 1 5 min. or as much longer as may be convenient, then cool in water t o room temperature, make up to IOO cc. and polarize as usual. In the case of low-grade products which have been clarified with a large excess of basic lead acetate, i t is imperative t h a t t h e excess alkalinity be neutralized before heating, this being best accomplished by the addition of I cc. (or z cc. in exceptional cases where a large excess of dry lead acetate has been used) of t h e dilute acid used for inversion. When a considerable number of determinations are t o be made a t the same time, the writer uses for a water b a t h a flat bottomed iron pan accommodating a dozen or more flasks and containing only enough water t o be above t h e surface of t h e liquid in t h e flasks. T h e whole is heated t o about 7 0 ° , the flame turned out and when a thermometer in one of t h e flasks indicates 67’ t h e flasks are taken out one a t a time, acid added and set aside for inversion. From a scientific standpoint this inversion process may be criticized on account of the fact that, due to variations in laboratory temperature and in thickness of flasks, marked variations in the rate of cooling, a n d hence in the speed of inversion, may occur. Practically no difference outside the experimental error could be detected, even when the temperatures a t which acid was added varied as much as IO’. It may be also t h a t t h e constant required for this method will be found on careful investigation t o vary slightly from t h a t now used in the Herzfeld method, which is itself under suspicion. I n the above work no attempt has been made a t much greater accuracy t h a n what
Vol. 9, No. 5
might be expected in a well equipped factory laboratory, and within these limits the method has been found fully as accurate as t h a t of Herzfeld, and much more convenient, DEPARTMENT OF SUGAR TECHNOLOGY COLLEGE OB HAWAII.HONOLULU
THE CHEMICAL CHANGES WHICH ARE CAUSED BY DEFECATION OF SORGHUM JUICE FOR SYRUP MANUFACTURE By ARTHURK. ANDERSON Received November 4, 1916
The manufacture of sorghum syrup consists of three distinct processes: ( I ) The extraction of the juice from the cane; ( 2 ) the purification of the crude juice, which is the process commonly called defecation; a n d (3) evaporation. T h e quality of syrup produced depends t o a large extent on the purity of the juice which is evaporated, which in turn is dependent upon the efficiency of the method used in defecation. Since defecation is the most important process in sorghum syrup manufacture, it was found desirable, in connection with the work on sorghum which is being done a t the Minnesota Experiment Station, to undertake the study reported in this paper. I n the past there have been many different methods used in defecation.’ Those which have survived a n d which are found in use a t the present time in Minnesota are of two types. A t the larger factories what is known as the lime process is employed, while a t the smaller mills heat alone is used. The factory method may be briefly described as follows: The juice from the press is pumped t o a “defecator,” which is a square tank of about joo gallons capacity. Near the bottom of the t a n k are steam coils which are used t o heat the juice during defecation. When the defecator is full, if lime is t o be added, i t is added as milk of lime and stirred in well. The heat is then turned on and t h e juice heated t o the ‘(cracking point.” T h e heat is then turned off a n d the juice allowed to subside for about I 5 min. During the defecation the impurities either rise t o the top, forming a scum, or settle t o the bottom of the defecator. After subsiding, the clear juice is drawn off and evaporated. I n some of the smaller mills the processes of defecation and evaporation are carried on together. I n these places open pan evaporators are employed a n d the green juice is run directly into t h e evaporator. The impurities are skimmed off as they rise. AS a rule no lime is used a t such mills. A third method, known as the “phosphate” method, has been proposed, and while not yet in actual use in Minnesota mills, it seemed so promising t h a t it was decided t o include it among those t o be investigated. I n this method the filled defecator is heated for 30 min. with calcium acid phosphate and then treated with lime. T h e tri-calcium phosphate which precipitates out has a clearing effect on the juice. The purpose of t h e preliminary heating with the calcium 1
Harvey W. Wiley, “Record of Experiments with Sorghum in 1892,”
U. S. Dept. Agr., Bur. of Chern., Bull. 87 (1893). 8C-95.
May,
1917
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
acid phosphate is t o produce a n inversion of sucrose, thus preventing its crystallization during t h e process, PURPOSE O F THE INVESTIGATION
The purpose of t h e investigations which were undertaken was t o make a study of t h e defecation of sorghum juice for syrup in order: ( I ) t o determine t h e changes in chemical composition which t h e juice undergoes during defecation and evaporation; ( 2 ) t o study t h e composition of syrups made by different methods; (3) t o study t h e quality (color, taste, clarity, etc.) of syrups made by the different methods; (4) t o make a special study of t h e lime method, as practiced in t h e larger mills with particular reference t o t h e proper amount of lime t o use, and a simple means of factory control; and ( j ) t o investigate t h e feasibility of t h e proposed phosphate method. METHODS O F PROCEDURE
I n studying t h e chemical changes which take place during defecation most of t h e work was done under actual factory conditions. Lots were run with no lime, with lime added t o alkalinity, with lime t o apparent neutrality, a n d with t h e calculated theoretical amount of lime required t o neutralize t h e acidity of t h e juice. Samples for analysis were taken of original juices, of t h e juices after defecation, and of syrups made from these juices. When juices had t o be kept for any length of time before being analyzed they were preserved with a I per cent solution of mercuric iodide, using I O cc. t o 250 cc. of juice. Where this was used corrections were made in t h e subsequent calculations. I n addition t o these factory experiments a series of laboratory defecations was run in which juice taken from cane produced on University Farm was used. These experiments were carried on i n Erlenmeyer flasks using j o o cc. of juice for each experiment. I n studying t h e lime method, with special reference t o t h e amount of lime t o use, the acidity of t h e juice was determined b y titration. T h e theoretical amount of lime t o neutralize this acidity was added. Also other amounts were added t o serve as a comparison. Where this was carried out in t h e factory t h e opinion of t h e owner was obtained as t o t h e desirability of t h e product. A careful study of this was made in the laboratory on a small scale where the conditions could be carefully controlled. The phosphate method was studied both i n t h e laboratory and under factory conditions. Calcium acid phosphate was added a t t h e rate of 5 lbs. per 1000 gallons and after boiling for 30 min. t h e juice was neutralized with milk of lime. The study of t h e syrup was made on 40 samples collected from various parts of t h e State. They were made under various conditions and for study were classified according t o t h e method of defecation. T h e quality of t h e syrups was considered from t h e standpoint of color, clarity and taste, market value being t h e criterion upon which the standards of judging were selected. A K A L Y T I C A L MET H 0D S
The usual analytical methods were employed with the following modifications of procedure t o make them applicable t o t h e materials which were being studied.
493
Acidity was determined with standard N / I O potassium hydroxide, using phenolphthalein as a n indicator. Some difficulty was experienced in determining t h e endpoint b u t with sufficient dilution the method is accurate t o within 0 . j of a cc. Results are expressed as the number of cc. of N/IO acid in I O grams of dry matter. Dry matter in the juices was determined by drying in a hot water oven for 8 hrs., t h e bulk of t h e water having first been removed o n t h e steam bath. A new methodl for determining dry matter in the syruPs was used i n which the amount of moisture present was found by measuring the acetylene generated when a weighed sample of t h e syrup was treated with calcium carbide in a special apparatus. Ash was determined on t h e same sample in which t h e dry matter was determined in the case of juices. With syrups a separate sample was used and in this case t h e soluble a n d insoluble ash were determined, together with t h e alkalinity of t h e soluble ash. I n all cases calcium o x i d e was determined on t h e ash. The calcium was precipitated as calcium oxalate and determined volumetrically with standard potassium permanganate solution. I n a few cases phosplzorus pentoxide was determined. The lead subacetate precipitate was determined as follows: I n t h e case of juices t h e Official Method2 was carried out exactly, but with syrups, i t was found t h a t if j cc. were used the volume of t h e precipitate was too large t o be measured in the tube and t h a t t h e recommended amount of lead subacetate was insufficient for complete precipitation. It was found t h a t by using 1’/2 cc. of syrup t h e volume of the precipitate could be read and t h a t there was sufficient excess of lead. The results were afterwards calculated t o t h e 5 cc. basis. Sugars were determined as “Sucrose” and “Reducing Sugars.” The sucrose was determined b y t h e polariscope, and t h e reducing sugars, which are reported as dextrose, b y means of a modification of Low’s volumetric method,a t h e modification consisting of t h e determination of t h e unprecipitated copper in a standard Fehling’s solution. CHEMICAL CHANGES DURING DEFECATION F A C T O R Y EXPERIMENTS-Table 1 shows t h e analyses of 6 series of defecations showing t h e composition of the original juice, of the juice after defecation and of t h e syrup resulting from t h e juice. I n t h e case of one phosphate defecation a n analysis is given of the juice after adding the acid phosphate and boiling for 30 min. I n the phosphate method calcium acid phosphate was added, 137 g. t o 80 gallons of juice. This was equivalent t o t h a t found in the advocated amount of a commercial phosphate sold for this purpose. After boiling for 30 min., lime was added until the juice was neutral t o litmus. I n the experiments where the theoretical amount of 1 R. M West, “ T h e Determination of Moisture in Syrups b y the Calcium Carbide Method,” THISJOURNAI,, 8 (1916). 31-35. 2 Harvey W. Wiley, “Official and Provisional Methods of Analysis,” E. S. Dept. A g r , Bur. of Chem., Bull. 107 (1912), 72-3, 241-242. 8 I b i d . . 1912, 241-242.
494
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
lime was added, 50 cc. of the juice were titrated with N/IO potassium hydroxide using phenolphthalein as a n indicator. From t h e amount of potassium hydroxide used the amount of calcium oxide necessary t o neutralize t h e acidity in t h e volume of juice in the defecator was obtained and this amount was added. I n the last cases, lime was added until the juice was considered b y t h e factory operator t o be neutral t o litmus. It was still slightly acid, however. I n Series 2 and 3 the lime had been calculated as calcium oxide instead of calcium hydroxide due t o a misunderstanding of the analysis which came with the lime. Hence, only 7 5 per cent of the theoretical amount was actually added. This accounts for the high acidity after defecation. I n t h e other sample the true theoretical amount was added. A closer study of the acidity as related t o lime added will be made later. At this point it is of interest t o note t h a t the acidity of the syrup is in all cases higher t h a n t h a t of the defecated juice, but lower t h a n in t h e original juice. Some of the possible explanations for these phenomena are as follows: According t o Maxwell’ the material precipitated from sorghum juice by alcohol is composed largely of mucilaginous materials. We may consider t h a t in ordinary defecation with heat a n d lime much of this material remains in solution. According t o O’Sullivan12 t h e gums are complex compounds which on hydrolysis give rise t o sugars and complex acids of high molecular weight. This being the case, the increase in acidity could be accounted for by the supposition t h a t during the high temperature of evaporation t h e gums are hydrolyzed, liberating the free acid. This theory would also account for some of the increase in dextrose after evaporation. Lamy3 gives the following figures for the amounts of calcium oxide dissolved by 1000 g. of a I O per cent sugar solution a t various temperatures: At Grams CaO in solution
..........
OD
25.0
15O 21.5
30° 50’ 12.0 5 . 3
70’ 2.3
100’ C. 1.55
If this calcium oxide is not simply in physical solution but partly in chemical combination in the form of saccharates i t may be t h a t with the high temperature of evaporation some of the calcium is split off from the sugar and deposits on the bottom of the evaporator. It is a known fact t h a t a t this stage of the process there is actually a deposition of lime. The decrease in lime content of the syrup as compared with the juice also confirms this theory, since as long as the lime is present in solution i t will react alkaline t o the indicator, a n d upon its removal the acidity of the syrup will rise. The darkening of the syrup during evaporation indicates a n oxidation. The oxidation of glucose produces acids. This would also contribute t o the increase in acidity. 1 H. W. Wiley and Walter Maxwell. “The Composition of Bodies Precipitated by Alcohol from Sorghum Syrups,” U. S. Dept. Agr., Div. of Chem., Bull. 29 (1890), 14-23. 2 Paul Haas and T . G. Hill, “The Chemistry of Plant Products,” 1912, 120, London, New York. a John E. Mackenzie, “Sugars and Their Simple Derivatives,” 1913, 3 1-42. London.
Vol. 9 , No. 5
The volume of the lead subacetate precipitate was determined with the hope t h a t it wpuld serve as a n indication as t o the completeness of defecation. The results, however, are not as consistent as was expected. The high value in the case of syrups is undoubtedly due in part t o the high acidity of the syrup. T h e a s h content increases after lime is added. This would indicate t h a t some of the lime added remains in solution in the juice and syrup. The decrease in ash after defecation in Series I may be explained by the fact t h a t insoluble phosphates were formed which removed some of the iron and calcium. In all cases the c a l c i u m oxide content increases after defecation and decreases again in the syrup. T h e increase in the defecated juice would seem perfectly natural. The decrease in the syrup would be accounted for b y the lower solubility of calcium salts in sugar solution a t a high temperature.’ Calcium citrate, which would be present, is more soluble in cold t h a n hot water. Another possible explanation is t h a t in the juice the calcium is present as acid salts which are soluble and which a t the high temperature of evaporation and the higher concentration change over t o the normal salts and are precipitated. I n studying the sugar content, it will be noted t h a t in all cases the percentage of sucrose increases after defecation. According t o Maxwell2 solutions clarified by lead contain levogyrous nitrogenous compounds. If this is t h e case the percentages of sucrose on original juices are too low. The increase in sucrose in defecated juices would be accounted for by the removal of these levogyrous bodies by the heat and lime during defecation. Maxwell’s work shows the following results on a syrup clarified with lead, with phosphotungstic acid, and with alcohol. The following are the polariscope readings :
.......................
Solution Clarified by Lead.. After treatment with HnPWinOas.. After treatment with HuPWioOas and alcohol..
64.99‘
................. 67.37’ ...... 72.93’
He accounts for the increase in reading after adding alcohol as due t o the reduction of t h e levorotatory power of levulose in alcoholic solution. He says, “the body, precipitated by alcohol, is in appearance dextrinoid, and t h e logical supposition would be t h a t the dextrogyrous property of the solution would be diminished, which in fact is not the case.” From the uniform decrease in reducing sugar aftei defecation it appears t h a t some reducing substance must be removed. Maxwell’s alcohol precipitate may contain some of the simpler dextrins which reduce Fehling’s solution. The decrease in dextrose after defecation may be explained as due t o t h e removal of dextrin-like bodies which reduce Fehling’s solution. T h e increase in dextrose after evaporation may be explained as being due t o the hydrolysis of sucrose or of mucilaginous materials. The increase in percentage of total sugar is of course I John E. Mackenzie, “Sugars and Their Simple Derivatives,” 1913, 3 1 4 2 , London. 3 LOC. cit.
N a y , 1917
T H E J O U R N A L O F I N D U S T R I A L A X D E A’GI
due t o removal of impurities during defecation a n d evaporation. I n all cases the percentage of nitrogen decreases after defecation. This is especially noticeable in the phosphate method. This seems natural in t h a t if the nitrogen is present as albuminous bodies it would be coagulated and thus removed during defecation. T h e marked decrease in t h e case of the phosphate method is due t o the clearing effect of the phosphate precipitate. The increased percentage of nitrogen in t h e syrup, as compared with t h a t in the juice, in some cases, is probably due t o fermentative changes in the juice before it was evaporated which changed the nitrogenous compounds into non-coagulable forms. This phenomenon has been observed also in t h e case of juices from canes which have been stacked for some time after cutting and before pressing in t h e factory. It is obvious t h a t only fresh canes can be used, if it is desired t h a t t h e nitrogenous bodies shall be as completely removed as possible in defecation. As would be expected, the per cent of solids-not-sugar TABLEI-SHOWINGCOMPOSITION OB
JUICE
~~
was found to be much less in t h e syrups t h a n in the juices. I n all cases the per cent of nitrogen in the solidsnot-sugar increases in the syrup over t h a t in the defecated juices. During defecation, the nitrogen which is in the form of protein coagulated by heat will be a t once removed. At this point, there is not a very marked decrease of solids-not-sugar. During evaporation, t h e solids-not-sugar which disappear are mainly non-nitrogenous bodies, thus bringing the per cent of nitrogen relatively higher in the syrup. I n all cases t h e p e r cent of solids-not-sugar and not-ash decreases after defecation and after evaporation. This shows t h a t a decrease in organic matter-not-sugar takes place mainly during evaporation. LABORATORY EXPERIMENTS-Table 11 shows t h e results of a series of laboratory defecations. Juice was obtained from cane which was cut and stored for a few weeks before pressing. Several methods of defecation were tried out as indicated in the table. I n each experiment 500 cc. of juice were used. I n the phosphate method, calcium acid phosphate was added in proportion t o the amount recommended
E E R I N G CH E M I S T R Y
49 5
for factory practice. In this case, the theoretical amount of lime required t o neutralize both the acid phosphate and the juice was added. I n the heat method, the juice was boiled for 30 min. t o observe the results on the inversion of sucrose. I n the rest of the experiments different amounts of lime were added a n d a t different times. Lime t o onehalf theory, t o theory, and t o neutrality was added. I n these experiments the theoretical amount of lime was computed on the basis of a n analysis made of t h e lime. This analysis was a determination of t h e alkalinity of t h e lime b y dissolving in standard acid and titrating t h e excess with standard potassium hydroxide. I n the case of adding lime t o neutrality, lime was added until the juice gave a slight alkaline reaction. The amount of lime required t o produce alkalinity was determined by making a n aqueous suspension of a known amount of lime, and then adding small amounts of this to the juice until it was alkaline. The excess was then evaporated to dryness and weighed, the difference in weight indicating the amount used DEFECATIONA N D OF SYRUP Nitfogen PERCENTAGE COMPOSITION O F THE DRYMATTER 111 SuDex- Total SolidsLime Nitro- SolidsAsh crose trose Sugars not-Sugar (CaO) gen not-Sugar .. . 0.364 0.18 5.38 5.14 40:2l 5j:53 9j:?4 6.26 0.335 0.11 1.78 4.87 41.72 52.55 94.27 5.73 0.525 0.06 1.79 4.77 41.92 53.02 94.94 5.06 0.436 0.16 3.19 18.93 0.449 0.29 3.91 58.95 22.12 81.07 1.65 0,539 0.05 0.26 3.99 62.39 19.64 82.03 17.97 2.06 4.33 65.81 24.73 90.54 9.46 0,281 0.20 3.91 58.95 22.12 81.07 18.93 0.449 0.29 1.65 3.97 64.23 19.35 83.58 16.42 0 20 1.25 4.48 66.82 23.66 90.48 9.52 O:ii7 0:20 2.06 0.280 0.28 3.65 3.24 57.38 34.57 91.95 8.05 3.43 59.38 33.31 92.69 0.414 0.06 0.79 7.31 7.88 0.403 0.23 2.88 3.56 57.57 34.55 92.12 3.91 58.95 22.12 81.07 18.93 0.440 0.29 1.65 3.91 63.06 18.63 81.69 18.31 0.530 0.20 1.00 4.47 66.40 24.35 90.75 0.332 0.16 1.75 9.25 3.91 58.95 22.12 81.07 18.93 0.449 0.29 1.65 4.11 64.28 18.79 83.07 16.93 0.672 0.23 1.42 4.9068.5024.6893.18 6.82 0.5920.23 3.36
BEFORE A N D AFTER
Lead Dry Precipi- Matter Series Lab. Acidity tate (Per NO. TREATMENT No. DESCRIPTION (a) (b) cent) 1 Phosphate 3085 Original juice 17.4 6.9 17.42 Method 3086 After addingphosphate 17.0 9.0 18.83 3087 After neutralizing 10.3 18.84 Syrup 8.1 8.5 66.50 3352 2 Phosphate 3174 Original juice 21.6 9.4 16.03 Method 3175 8.5 17.56 After phosphate def. 7.4 3314 14.4 72.70 SVrUD 21.0 ~. 3 Three-fourths 3174 Original juice 21.6 9.4 16.03 Theoretical 3176 After defecation 11.7 11.8 16.17 Syrup 17.0 13.8 72.50 Lime 3315 4 Theoretical Original juice 17.4 11.4 18.80 3200 3201 6.2 18.46 Lime Defecated juice 4.6 3319 75.60 13.8 12.6 Syrup 3174 Original juice 21.6 9.4 16.03 5 Lime t o 3177 Neutral (c) After defecation 8.6 10.7 16.32 77.20 3316 SvruD 15.9 13.9 3174 6 Lime t o Original juice 21.6 9.4 16.03 3178 Neutral ( d ) 7.2 15.95 After defecation 3.0 3317 17.8 64.70 9 . 1 Syrup ( a ) Expressed as cc. N/10 acid per 10 g. dry matter in sample. ( b ) Expressed as cc. lead subacetate precipitate from 5 cc. sample, divided b y the ( c ) Neutral t o litmus. ( d ) Lime t o neutral added after heating. Neutral t o litmus.
....
17
....
per cent of dry matter, t o bring results t o uniform dry matter basis.
by t h e juice. The following typical results show t h e amount of lime required according t o a theoretical calculation as compared with the amount actually required t o produce a slight alkalinity t o phenolphthalein: Sample I-Calculated theoretical amount of lime to neutralize acidity, 0.73 g.; actual amount required, 1.60 g. Sample 2-Calculated theoretical amount of lime t o neutralize acidity, 0.88 g.; actual amount required, 1.99 g. I n both cases the actual amount i s about 2.2 times t h e theoretical amount. Notes were taken on the color of the juices after defecation. Where no lime was added the color was, of course, very light. Where lime was added to alkalinity the juice was a very dark brown color. I n cases where lime was added t o one-half theory the juice remained light colored. With lime added t o theory the juice seemed t o be just a t the point where it had started t o t u r n dark. Where lime was added after heating t o boiling t h e scum usually sank instead of rising. This shows the undesirability of adding lime after the separation of the scum has takenplace. A study of the acidity in Table I1 shows just what would be expected except t h a t the juice should b e
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
496
neutral after adding the theoretical amount of lime. The increase in acidity in No. 3 2 0 6 is due to the acid phosphate. Nos. 3 2 0 7 and 3 2 1 2 correspond. No. 3209 is higher t h a n No. 3 2 1 2 because the lime was added after heating. The same thing is noticed in 3 2 1 0 as compared with 3211. This would indicate a higher efficiency for t h e lime added before heat is
Vol. 9, No. 5
The nitrogen content shows what was pointed out in connection with Table I, namely, t h a t where cane is kept for some time a change in the character of t h e nitrogen takes place putting it in a form which is not removed by the process of defecation. DEFECATOR RESIDUE-In the factory study, it Was noticed t h a t there was a large amount of residue after
TABLE11-SHOWING RESULTSOF LABORATORY DEFECATION Lead Dry Precipitate Matter Per cent (b) Original juice. 23.0 12.9 15.56 Phosphate. After boiling 30 min. with phosphate 26.9 14.2 20.05 Phosphate. After adding lime t o theory.. 7.2 12.1 19.07 Heat. Boiled for 30 min.. 22.6 14.0 17.50 Lime t o theory. Heated first.. 7.7 16.02 8.7 Lime t o half theory. Heated first. 15.7 10.8 15.73 Lime t o half theory 14.5 11.4 14.81 Lime t o theory 7.2 10.7 14.91 Lime t o neutral.. Neutral 8.8 15.34 Expressed as CC. N/10 acid per 10 grams dry matter in sample. Expressed as CC. lead subacetate precipitate from 5 cc. sample divided by the per cent of
Lab. No. 3205 3206 3207 3208 3209 3210 3211 3212 3213
TREATMENT
Acidity
................................ ....... ..................... ................ ............. ........................... ............................... .............................
(a)
applied t o a defecator. The neutralizing effect of the lime added is almost directly proportional to t h e amount of lime added u p t o the theoretical amount. The necessity for using nearly double the amount of TABLE111-PERCENTAGE
COMPOSITION OF DEFECATOR RESIDUES Laboratory No. 54 Laboratory No. 3204 Used Factory Method Theoretical Lime Dry M a t t e r . . 28.74 25.02 Composition of Dry Matter: 5.62 13.84 Ash.. 20.86 Sucrose. Dextrose.. 4.76 25.62 Total Sugars.. 3.14 Nitrogen.. 2.46 0.61 Lime (CaO). 2.63 10.91 CaO in Ash.. 19.00 0.81 PeOs 2.03 14.33 P10a in Ash.. .............. 14.65
...............
..................... ..................... ................... ................
................ .............. .............. ......................
SYRUPS
Sucrose 31.43 33.44 34.40 31.52 32.03 32.20 33.02 31.93 32.21
Dextrose 51.99 49.55 40.49 50.06 48.57 51.05 52.81 51.45 48.83
O F THE
Total Sugars 83.42 83.26 73.50 81.78 80.59 80.11 85.83 83.37 81.03
DRY MATTER Lime (CaO) N 0.587 0.44 0.464 0.44 0.616 0.42 0.344 0.44 0.596 0.45 0.607 0.44 0.585 0.44 0.594 0.40 1.068 0.41
dry matter, t o bring results t o uniform dry matter basis.
the juice was removed from the defecator. An analysis of this residue from two defecators was made t o serve as a basis for considering the advisability of using a filter press t o recover the juice which is a t present lost. Table I11 shows the composition of defecator residues. This shows t h a t there is a t present a considerable loss of sugar, a great part of which could be saved by the use of a filter press. Whether t h e increase in yield of syrup would justify the added expense can be determined only b y further experiments under factory conditions. ANALYSES O F COMMERCIAL SYRUPS
lime t o neutralize about one-third the original acidity is difficult t o understand. It is probable t h a t a t this concentration the lime is combining with the sugar or some other substance. A change of some kind is indicated in the darkening of the juice before alkalinity is reached. The lead subacetate precipitate shows a decrease as the amount of lime used increases, the maximum being reached where lime has been added t o theory. The a s h determinations show very little except in the case of 3 2 1 3 where an increase of ash would be TARLE~ ~ - ~ O M P O S I T l O NOF
PERCENTAGE COMPOSITION Ash 5.80 5.75 5.52 5.59 5.65 5.78 5.74 5.83 6.52
Table I V shows the averages of analyses of syrups made by the indicated method of defecation. The first column gives the number of samples from which the averages are taken. Under the head of “Lime Used” are included all of the samples where lime was used in defecation excepting those wherespecial amounts of lime were used. These are given under special heads. I n one sample, bicarbonate of soda was used as a neutralizing agent in defecation. Under t h e head of “Crystallized” are included all samples which showed crystallization regardless of the method used in defeca-
FROM VARIOUS METHODSO F DEFECATION
COMPOSITION OF THE ASH Ratio of Lead PERCENTAGECOMPOSITION OF THE DRYMATTER Nitrogen AlkaAlkalinity Ratio No. PreInin linity -to-of In- Lime of Dry Acid- cipiSol- solSolids- Ni- Solids- of Solu- soluble (CaO) Sam- Matity tate uble uble Lime Su- Dex- Total not- tronot- Ash Tot a1 ble t o Total in DESCRIPTION ples ter (u) (b) Ash Ash Ash (CaO) crose trdse SugarsSugar gen Sugar (6) Ash Ash Ash Ash 5.35 Nolime 17 76.2 18.8 13.3 3.90 3.02 0.881 0.202 51.01 40.69 91.70 8.30 0.161 1.94 8.91 2.290 2.98 22.44 6 33 Limeused 11 76 7 13 6 12 4 4 25 3 38 0 998 0.265 55.50 35.98 91 48 8 52 0.173 2.05 9.65 2.190 2 84 22 98 Limetotheory 2 74:O 15:4 13:2 4:02 3101 1:008 0.365 62.20 29.10 91:30 8:70 0.214 2.46 8.92 2.193 2198 24:96 10:70 9 . 4 13.7 4.72 2.89 1.206 0.491 51.39 41.12 92.51 7.49 0.190 2.67 9 . 8 7 2.083 3.44 26.54 10.85 L i m e t o n e u tral 4 72.9 9 . 1 12.9 4.65 3.10 1.549 0.643 52.43 39.98 92.41 7.59 0.181 2.39 8.50 1.812 2.71 32.98 13.55 Limeinexcess 3 74.9 9.39 3 68 6 12 7 13 0 4 58 3 39 1 193 0.395 49.60 43 87 93 47 6 53 0.095 1.45 8.87 1.932 2.61 26 09 Phosphate 3.35 Bicarbonateofsoda 1 70’0 17‘6 15‘7 2190 1:97 01932 0.097 50.48 44:09 94:57 5:43 0.201’ 3.70 5.82 2.020 2.95 32:12 6.94 Crystallized 12 78:7 13:9 12:7 4.33 3 . 1 5 0.963 0.290 58.12 33.29 91.41 8.59 0.199 2.32 9.52 2.234 3.08 22.60 4.65 Verybadlycrystallized 1 82.5 11.4 10.9 2.24 1.79 0.453 0.104 67.26 30.28 97.54 2.46 0.147 5.97 7.61 3.394 4.24 20.21 ( a Expressed as CC. N/10 acids per 10 grams dry matter. Expressed as cc. lead subacetate. precipitate from 5 cc. syrup c) Expressed as cc. N/10 acid requlred t o neutralize the ash from 5 grams of dry matter.
.................... .................. ............. ............. .............. .................. ......... ................ ......
r]
expected. T h e c a l c i u m oxide content shows results similar t o those reported in Table I. With regard t o t h e sugars there are t h e same general results as in Table I. The results here would indicate t h a t there is no inversion of sucrose on boiling with acid phosphate. Sample 3208, where t h e juice is boiled for thirty minutes alone, shows the lowest percentage of sucrose of any defecated sample. This indicates some inversion.
tion. The last sample is one made in 1 9 1 2 and is very badly crystallized. It seems abnormal in many respects, probably from t h e fact t h a t much of the uncrystallized portion of the original syrup has been used, leaving t h e remaining portion abnormal. There is nothing exceptional with regard t o the d r y matter content of the different classes of syrup except t h a t t h e crystallized samples contain a higher percentage t h a n the others. This is especially true of
May, 1917
T H E JOURNAL OF I N D U S T R I A L A N D EXGINEERING CHEMISTRY
the badly crystallized sample. It is evident t h a t crystallization is dependent t o a large extent .on the concentration. The lead subacetate precipitate is smaller in the samples where lime was used t h a n in those where it was not. T h e sample where sodium bicarbonate was used shows the largest precipitate. This is due t o the presence of acids left in a soluble form by the sodium bicarbonate. The acidity decreases with the amount of lime used. The high acidity of t h e “lime t o theory” syrups is due in part t o the fact t h a t this series includes t h e sample mentioned above as having only three-fourths of the theoretical amount. A juice neutral t o litmus gives a n acidity equal t o about one cc. N / I O acid per gram of dry matter. T h e a s h content increases as lime is added. T h e sodium bicarbonate sample is very low in ash as is also t h e one which is badly crystallized. The increase in soluble a s h where lime was used is due t o the increase in total ash. T h e ratio of the soluble ash t o total ash shows a definite relation t o the amount of lime added. T h e ratio decreases with t h e addition of lime. There is a direct relation between t h e percentage of insoluble a s h and t h e a m o u n t of l i m e added, the former increasing as the latter is added. T h e same relationship holds in the case of the insoluble ash calculated on the basis of the total ash and with t h e calcium oxide calculated on t h e total ash basis and on the total dry matter basis. T h e percentage of calcium oxide is very low where sodium bicarbonate is used. I n a study of t h e a s h i t was thought t h a t a relationship would be found between i t and the crystallization. I n speaking of molasses, Mackenzie states t h a t formerly “the presence of invert sugar was supposed t o prevent the formation of crystals, b u t , on the contrary, it is now known t h a t i t has no such effect. Gunning has shown t h a t while concentrated alcohol does not dissolve sugar, a n alcoholic solution of organic salts of potassium does dissolve sugar, forming a thick uncrystallizable syrup, which is very easily soluble in alcohol, methyl alcohol or water, but from which sugar is not again directly obtainable. This syrup consists of compounds of potassium saccharate with potassium salts of organic acids found in molasses.” Applying this theory t o the crystallization of sorghum syrup it would be expected t h a t the percentage of soluble ash would be small. This, however, is not the case. I n studying the sugar content of t h e syrups it is a t once seen t h a t the sucrose content is less where no lime is used a n d the dextrose is higher. This, of course, is due t o inversion with the stronger acidity. I n most of the samples where no lime was used open pan evaporation and slow boiling were practiced, which would also favor inversion. The syrup from the phosphate method shows t h e lowest amount of sucrose. This is due very likely t o boiling with t h e acid phosphate. The high percentage of sucrose and low amount of dextrose in t h e
497
crystallized samples of course seems normal. This explains in part why these samples crystallized. The lesser percentage of solids-not-sugar when no lime was added can be accounted for by the fact t h a t in most of these cases slow open pan evaporation, with much skimming, was practiced. The long boiling would naturally remove more impurities than rapid evaporation. The phosphate method shows a higher purity than the samples where lime was used. The percentage of nitrogen was less where no lime was used, which can be explained on the slow evaporation basis. I n the other samples the nitrogen decreases’ with the amount of lime. I n the phosphate method the nitrogen content is less t h a n in any of the others. QUALITY OF SYRUPS
I n studying the quality of the ‘syrups they were judged on the basis of color, clarity, a n d taste. Table V gives t h e number of each sample with a description of how i t was defecated. I n judging color the samples were arranged in order of their color b y reflected light, the lightest being placed first. Two of the samples in which the phosphate was used are the darkest. The lightest samples were made without lime. A study of t h e acidity shows t h a t those samples in which lime was used and which appear a t the head of the list are still highly acid while those a t the foot of the list are not as acid. The darkness of some TABLE \‘-QUALITY
OB
SYRUPS
SYRUPSARRANGEDIN ORDSR OF No. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Description Phosphate Lime to theory Lime to neutral Lime to neutral Lime Lime to theory Lime Nolime Nolime N o lime Nolime Nolime Nolime Nolime Nolime Nolime Nolime N o lime Nolime Lime Nolime Lime t o neutral Nolime Nolime Nolime Nolime Lime Lime in excess Bicarbonate of soda Lime Lime Lime Lime Lime in excess Lime in excess Lime Lime to neutral
Color 37 24 20(a) 44(a) 43(a) 34 16(a) 5l(a) 22 38 31 29 32 40(a) 33(0) 14(b) 15(a) 49(0) 28 36 19(a) 54 21 27
Clarity CrystalLight Dark lization 49(a) 34 37 36 18(a) 38 24 54 32
.. .. .. .. .. .. .. .... ... . .. .. .. 50(a) . . 18(a) .. 35(0) . . ‘p .... 30 .. 17(a) , . 25 .. 53(a) . . 39 .. 45(a) . . 47(a) . . 48(a) . . 26 ..
... ... . . (a) Lime used in defecation.
... .
Ta
50(a)
... .
Best
39 25 30 27
22
.. ... . X) :: 17(a) . .
42
.. . .. .. . ... ...
.. . .. . . . ... ...
... . ... . . .
. . . ..
. .
.. . ... . . . . .. .. . . . . . . ... ... ... ...
Good
Medium
. . . . . . . .
. . .
. . ..
. . ..
Poor
. .
. . . .. .. .. . . .
3ad
(b) Phosphate method in defecation.
samples, for example, No. 23 and No. 26, where lime was not used, is due t o slow evaporation. The darkness of the phosphate samples is due to lime being
498
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C E E M I S T R Y
added t o neutrality a n d t o boiling one-half hour in t h e defecator bef,ore evaporation. Sample 14, made b y t h e same method, excepting t h a t lime was added t o three-fourths the theoretical amount, is lighter in color. It can then be concluded t h a t a dark syrup is d u e t o much lime a n d to slow, long continued evaporation. I n determining the clarity of the syrup test tubes were filled with syrup and the transparency noted. There were two distinct types of syrups, t h e light a n d the dark. These two were not comparable so each group was arranged separately according t o clarity. I n t h e light syrups those in which lime was used are t h e clearest. The relationship is not the same in the case of the dark syrups as two of t h e phosphate samples are well toward the top of this list. Sample 14, t h e other phosphate sample, was not made neutral with lime but lime was added t o three-fourths theory. It appears t h a t clarity varies directly with t h e amount of lime. Under t h e head of “Crystallized” are given all samples which show crystallization. Those which show the least amount are placed first. It is noticeable t h a t most of t h e m were made with lime defecation. From this it appears t h a t lime defecation removes 4L gummy materials’’ which if present prevent crystallization. The presence of lime would also prevent inversion of sucrose. The relatively higher percentage of sucrose would favor crystallization. T o prevent crystallization well defecated juices should not be evaporated t o too great a concentration. I n judging taste two persons worked independently. T h e y came t o practically the same decisions as t o which were the ten best samples. I n studying the taste, t h e syrups were tasted four times. Each time t h e poorest were eliminated. Those remaining a t the end were considered the best. Among t h e best only 2 samples were made without lime. All of the phosphate samples remained in this group. No lime samples were found in the last group. From this it appears t h a t the phosphate and lime methods produce the best tasting syrups. T H E PHOSPHATE METHOD
From t h e high rating which has been given the samples of syrup made by phosphate defecation it would appear t h a t this is t h e most desirable method. If the quality alone were t o be considered it undoubtedly would be, But one of the big factors is the extra cost of production, both in time and in extra materials a n d equipment. Recently a method in which a phosphate is used has been recommended, This method advocates t h e addition of lime t o alkalinity and allowing the juice t o settle, After settling, the clear juice is run off into another defecator and made slightly acid with a n acid phosphate. The juice is then heated and allowed t o settle for a second time. T h e clear juice is then drawn off and evaporated. This method is said t o give a very clear and bright product. The chief objection t o this method is the time required t o complete the process of defecation. It would take
Vol. 9, KO.j
2 or 3 hrs. while the method in use a t present requires only 30 t o 45 min. T o use the phosphate method a n d handle the same volume of juice as is now handled would necessitate the installation of four to six times as many defecators. The added expense for lime and phosphate would be a minor objection to this method. AS was pointed out, it requires 2 . 2 times the theoretical amount of lime t o give the juice an alkaline reaction. T h e phosphate used can be obtained a t five cents per pound. This would be used a t the rate of j lbs. per 1000 gals. of juice. The added expense for lime and phosphate would not be serious, although on a large scale it would amount t o considerable in a season’s run.
LIME bIETHOD-FACTORY
CONTROL
A syrup and molasses dealer,’ who has handled large quantities of sorghum syrup,says t h a t the best quality of syrup is light in color and mild in flavor. With this in mind a special study of the lime method was made to determine the correct amount of lime t o add t o produce this result. Since one of the main objects in adding lime is t o neutralize acidity it was thought t h a t the theoretical amount was the proper amount to add. T 6 confirm this, experiments were conducted at two factories where a 50-cc. sample of the juice from each defecator was titrated with N/IO potassium hydroxide and the amount of lime t o correspond to this titration was added. Very satisfactory results were obtained. At one factory the system was put into actual operation and has now been used for two seasons. The manufacturers expect t o use this method in the future. Table VI shows the results of two samples defecated with the theoretical amount of lime. The uniformity of acidity of the defecated juice is striking. The last part of the table shows the lack of uniformity where the lime was added by t h e manufacturer in amounts TABLEVI-RELATION
OF LEAD SUBACETATE PRECIPITATE Description Lead subacetate Lime added to theoretical amount precipitate(a) Original juice.. .................... 11.4 6.2 Defecated juice., Original juice.. 11.6 6.7 Defecated juice.. . . . . . . . . . . . . . . . . . . Lime added according to factory method 3103 Defecated juice.. .................. 6.8 3198 Defecated juice.. . . . . . . . . . . . . . . . . . . 12.8 3199 Defecated juice.. .................. lo.? 10. I 3177 Defecated juice.. 7.2 3178 Defecated juice.. ( a ) Expressed as cc. recipitate from 5 cc. sample. ( b ) Expressed as cc. 5 / 1 0 acid per 10 grams dry matter.
Lab. No. 3200 3201 3202 3203
.................. ....................
..................
..................
TO
ACIDITY
Acidity@) 17.4 4.6 17.7 4.2 10.2 5.9 12.0 8.6 3.0
determined by his judgment or by using litmus as an indicator. This shows t h e need for factory control. Table VI1 shows the proper amount of quicklime t o add t o known quantities of juice where a jo cc. sample requires the indicated number of cc. of N / I O TABLEVII-SHOWING THE AMOUNTSO F QUICKLIME(CaO)
IN OUNCES REQUIREDFOR DIFFERENT VOLUMES OF JUICE HAVING THE GIVEN A cI D I T Y Gals. Acidity in Cc. N/10 KOH Required to Neutralize 50 Cc. of Juice Juice (10) (12) (14) (16) (18) (20) (22) (24) (26) (28) (30) 2 1 . 0 22.5 7.5 9 .0 .. . 10.5 1 2 . 0 13.5 1 5 . 0 16.5 18.0 19.5 1,oo 15.0 18.0 20.5 2 4 . 0 2 7 . 0 3 0 . 0 3 3 . 0 3 6 . 0 3 9 . 0 4 2 . 0 4 5 . 0 2.20 58.5 6 3 . 0 67.5 4 9 . 5 5 4 . 0 3 6 . 0 4 0 . 5 4 5 . 0 22.5 2 7 . 0 3 1 . 0 3.00 30.0 36.0 41.0 48.0 54.0 60.0 66.0 72.0 78.0 84.0 90.0 4.00 112.5 97.5 105.0 82.5 9 0 . 0 6 0 . 0 66.5 7 5 . 0 51.5 37.5 6 1 . 0 5.00
potassium hydroxide to neutralize it, using phenolphthalein as a n indicator. Where calcium hydroxide 1 A. A. Denton, “The Manufacture of Sorghum Syrup,” U. S. Dept. Agr.. Farmers’ Bull. 90 (1899), 31.
May, 1917
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
is used approximately one-third should be added t o the indicated quantities. Or, t o use the same table, the titration can be considered as one-third more and t h e figures read direct from t h e table. For example, if t h e defecator contained 400 gallons of juice and if the titration showed 18 cc. of N / I O potassium hydroxide solution used, instead of reading the lime as 42 OZ., it would be very simple t o run over t o t h e column headed 24 cc. a n d read t h e lime required as 7 2 OZ. T h e indicated amount of lime should be weighed out, slaked and added as milk of lime. SUMMARY
I-The acidity of the juice of sorghum cane decreases during defecation and increases during evaporation, with the lime a n d phosphate methods. T h e acidity varies inversely with the amount of lime used. 2-The volume of the lead subacetate precipitate is not a good indication of the efficiency of defecation. With high acidity there is a large precipitate. 3-The ash content increases after lime has been added. I n the phosphate method there is a decrease in the amount of ash. 4-Calcium oxide increases during defecation and decreases during evaporation. j-During defecation there is a n apparent increase in sucrose a n d decrease in reducing sugars. &The nitrogen content decreases during defecation. I n cane which has stood after being cut t h e nitrogen is changed t o a non-precipitable form which is not removed by defecation. 7-Solids-not-sugar decrease during defecation and evaporation, the larger decrease being during the latter process. 8-The color of the juice is not darkened materially until more than the theoretical amount of lime has been added. The amount of lime t o produce alkalinity is 2 . 2 times t h e theoretical amount. 9-Acidity in syrups varies inversely with the amount of lime used. I o - I n syrups the total ash, insoluble ash and calcium oxide increase with the amount of lime added. I I-Sucrose increases a n d dextrose decreases with the amount of lime used. I a-Crystallization is due t o a high percentage of dry matter, a relatively high sucrose content and a juice relatively free from “gummy materials.” It occurs most frequently in samples where lime was used in defecation. 13-The darkness of color of a syrup varies directly with the amount of lime used in defecation and with the time required for evaporation, 14-The phosphate a n d lime methods give the best tasting syrups. For economic reasons the lime method is considered the better t o use. I 5-The theoretical amount of lime gives proper defecation with the minimum darkening of t h e juice. The titration of the juice is a n efficient method of factory control. DIVISIONOF AGRICULTURAL BIOCHSMISTRY AGRICULTURAL EXPERIMBNTSTATIOX ST. PAUL, MINNESOTA
499
THE CORRECTION REQUIRED IN APPLYING THE BABCOCK FORMULA TO THE ESTIMATLON OF TOTAL SOLIDS IN EVAPORATED MILK1 B y 0. L. EVENSON Received March 13, 1917
The Babcock formula,*
T
=
L -
4
+
1.2
X Per cent F a t ,
where T = total solids and L = Quevenne Lactometer reading: or 1000 X sp. gr.3 - 1000, might not be expected to yield as accurate results when applied t o evaporated milk as when applied to whole, fresh milk because when milk is concentrated t h e specific gravity a n d total solids do not increase a t the same rate. Babcock’s2 complete formula
where s = specific gravity and f = per cent fat, gives still less satisfactory results than the short formula. While Richmond’s4 formula, G T = 0 . 2 6 2 5 -I . 2 X Per cent F a t , D where T = total solids, G = 1000 X sp. gre8- 1000 and D = specific gravity3, will give more accurate results t h a n either, it is not as simple as the short formula of Babcock and is not directly applicable without a small correction. Bigelow and Fitzgerald‘ showed t h a t more accurate results could be obtained with the Babcock formula on the original evaporated milk t h a n on the same milk diluted with a n equal weight of water. N o mention, however, is made of t h e temperature a t which t h e specific gravity was determined or a t which the evaporated milk had been kept preceding the determination of the specific gravity. T h a t the specific gravity of freshly drawn milk,
+
when measured at a definite temperature, ~~~
15.
so
3; or 15
C., gradually increases on standing was, accord-
ing t o Fleischmann,6 first observed b y Quevenne, but is generally known as Recknagel’s’ phenomenon. It has been shown by Fleischmanns t o be due t o a solidification or change in t h e physical state of t h e fat. When milk is cooled below the solidification point of butter-fat, the latter begins to solidify and in this way increases the specific gravity. Conversely when milk which has been cooled t o its maximum specific gravity, is heated, its specific gravity decreases until the fat is again melted, when no further change takes place. The same phenomenon has been observed with a n emulsion of butter-fat and water. This change in the specific gravity increases with the percentage of f a t , skimmed milk showing little or no change. 1 Read at the 53rd Meeting of the American Chemical Society in New York City, September 25-30, 1916. Published by permission of the Secretary of Agriculture. * Twelfth Ann. Report, Wis. Agr. Expt. Sta.. 1896, 120-126, Madison,Wis. 8 At 15.56’ C. (60° F.). Richmond’s “Dairy Chemistry,” 2nd Edition, p. 69 (1914). 6 Bull. 6 (1915), Research Laboratory, Nat’l Canners‘ Assn. 6 J. Landw., 1918, 282. Milchscifung., 12 (1883). 419. LOC.cif.; also 1901, 33.
*
