INDUSTRIAL AND ENGINEERING CHEMISTRY
1256
Vol. 38, No. 12:
ACKNOWLEDGMENT
TABLE111. EFFECTOF TEMPERATURE ON PRECIPITATION OF PARTLY
Pectinic Acid No.
DE-ESTERIFIED P E C T I K I C ACID FROM 1 y o SOLUTION Temp., Pptn., Ill1 c. PH % O
The authors are indebted to the following members of thie laboratory: W. H. Ward for determination of the diffusion constant and H. A. Swenson for some of the analyses. LITERATURE CITED
(1) Baker, G. L., and Goodwin, M.W., Del. 4gr. Expt. Sta., Bull.. 234, Tech. KO.28 (1941); Bull. 246, Tech. No. 31 (1944). (2) Eastern Regional Research Lab., private communication, 1948. (3) Hills, C. H., White, J. W.,Jr., and Baker, G. L., Proc. Inst. Food Tech., 1942, 47. (4) Hinton, C. L., “Fruit Pectins”, 1st Am. ed., p. 33, New York,.
Chemical Pub. Co., 1940.
TABLE IV. EFFECT OF INTRISSIC VISCOSITY ON PRECIPITATION(5) Jansen, E. F., and hracDonnel1, L. R., -4ich. Biochem., 8 , (1946). O F PARTLY DE-ESTERIFIED PECTINIC ACID3.3B FROM 1% SOLUTION AT
Minutes Heated a t 97‘ C. and pH 3.3
Iril
Pptn., %
pH 1.3 Minutes Heated at 97O C. and pH 3.3
[VI
Pptn.. %
Calculations for the refluxed sample gave a molecular weight of
7 X lo3. All of these results have the same order of magnitude and suggest that samples with molecular weights much below 7 X l o 3 cannot be handled by this technique. The data indicate that precipitation of low-methoxyl pectins by acid is favored by pH values below 2, temperatures below 25’ C., and a methoxyl content below 4. Considering these data, many samples both of pectin in extracts and in solutions prepared from isolated pectin have been de-esterified and precipitated by the following procedure:
{j?
(6) Jansen, E. F., TT:aisbrot, S. Fa, and Rietz, E., IND. ESG. CHEM., ANAL.ED.,16, 523 (1944). (7) Kaufman, C. JT‘., Fehlberg, E. R., and Olsen, A. G., Food I n d m ’ tries, 14 (12), 57-8, 109 (1942); 15 ( l ) , 58-60 (1943). (8) McCready, R. M., Owens, H. S., and llaclay, W. D., Ibid., 16, 794, 906 (1944). (9) Owens, H. S., Lotakar, H., Merrill, R. M.,and Peterson, .I., J. Am. Chem. SOC.,66, 1178 (1944). (10) Owens, H. S., Lotakar, H., Schultz, T. H., and Maclay, W. D , , Ibid., 68, 1628 (1946). (11) Owens, H. S., McCready, R. M., and Maclay, W.D., IND.ENO CHEM.,36, 936 (1944). (12) Owens, H. S., and Maclay, W. D., J . Colloid Sci., 1, No. 4, 313, (1946). (13) Paul, R., and Grandseigne, R. H., French Patent 695,204 (Aug. 24, 1929). (14) Pauling, L. C., “Nature of Chemical Bond”, p. 307, Ithaca,. Cornell Univ. Press, 1940. (15) Pollari, V. E., Murray, 1%’. G., and Baker, G. L., F m i t Products J., 25 ( l ) , 6-8 (1945). (16) Siiverborn, S., dissertation, Uppsala, 1945. (17) Schultz, T. H., Lotakar, H., Owens, H. S., and Maclay, W. I).. J . Phys. Chem., 49, 564 (1945). (18) Simha, R., Ibid.,44, 25 (1940). (19) Svedberg, T., and Pederson, K. O., “The bltraoentrifuge”, pp349-53, New York, Oxford Univ. Press, 1940.
Fifteen hundred grams of commercial citrus pectin (moisture
7.07,, methoxy19.0yo, uronic anhydride 83y0 corrected for moisture and ash) were dissolved in 30 liters of water a t 25’ C. The solution was cooled to 13” C., followed by the addition of 1200 ml. of ammonia hydroxide (28y0“8) solution. The temperature rose to 15” C., where it was maintained for 3 hours and 20 minutes. The ammoniacal solution was poured into 20 liters of solution containing 800 ml. of concentrated sulfuric acid. The mixture was stirred slowly to break up lumps and ensure complete precipitation of the pectinic acid. The resulting pH was about 1.3. The free liquid was drained from the acid gel by screening in a cloth-lined reel. The drained gel was freed of more solution by pressing in cloth bags in a hydraulic press to a solids content of 307,. Excess acid and ammonium salts were washed from the gel by suspending it in 40 liters of water. After thorough stirring, the wash water was again drained from the gel followed by hydraulic pressing. The procedure was repeated. The press cake was then disintegrated, spread on trays, and dried at 66” C. in vacuo. The dried flakes of pectinic acid were ground in a hammer mill to pass a 100mesh screen, Drying in vacuo is not essential to the process, since tray drying in air up to 80” C. has been used successfully. A yield of dried poffdered pectinic acid of 1275 grams or 95% (corrected for moistureand loss of methoxyl) was obtained. To increase its dispersibility, the material was stirred in an atmosphere of ammonia until a 1% solution gave a pH of about 4.5, This required only about 10 minutes.
Free Evaporation into Air of Water from a Free Horizontal Quiet SurfaceCorrection Attention is called to an error in Equation 11 of the paper by AND Boelter, Gordon, and Griffin, appearing in INDUSTRIAL ENGINEERIXG CHEMISTRY, 38, 596 (1946). In the original paper by Hinchley and Himus [Trans. Inst. Chem. Engrs. (London), 2, 57 (1924)l their equation is given as:
where W = rate of evaporation, kg./sq. m./hr p = pressure, mm. Hg In the notation and units employed by Boelter, Gordon, and Griffin this becomes
e
(Puw- Pvm)1.2
and is in better agreement with the results of Boelter, Gordon, and Griffin’s investigations given in Equation 13 as:
SUMMARY
Low-methoxyl pectins de-esterifird by alkali 01 acid can be precipitated in yields greater than 90% by use of acid below pH 2 a t temperatures below 2.5” C., when the methoxyl content of the pectin is below 4 and the intrinsic viscosity is greater than 2. Enzymatically de-esterified materials can be obtained in 80% yields or above a t methoxyl contents less than 7%. The isolated material can be pressed to a solids content of 30% or more, saving alcohol or heat to that extent This press cake can be iedissolved a t pH values between 4 and 5 to yield a usable concentrate, or it can be dried, ground, and partly neutralized.
= 0.091
e
=
0.067
- P,,)l.z
than Equation 11 as shown. The mistake may have arisen from a printer’s error in a later aper by Himus [Trans. Inst. Chem. Engrs. (London), 7, 166 1929)], where the correction is incorrectly stated as
P
w = 0.02 (P‘
- PJ1.2
which becomes e
=
0.20 (Psw- Py,)1,2
in Boelter, Gordon, and Griffin’s units,
