Extraction of Hemicelluloses from Plant Materials QUANTITATIVE STUDY E. YANOVSKY Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Washington, D. C.
On the basis of the results cited here, the explanation advanced that the break in the extraction curve for beet pulp is due to pectin present is apparently valid as far as the acid extraction is concerned. After pectin has been removed from the beet pulp with ammonium oxalate, a smooth acid extraction curve is obtained. This idea was further corroborated (though not conclusively) by the smooth acid extraction curve for sweet potato pulp. The above explanation does not hold in case of alkaline extraction of hemicelluloses. The
break is present in alkaline extraction curves for both treated beet and treated sweet potato pulps. For alkaline extraction the alternative explanation given in the previous article (3)-i. e., that the break in the extraction curve is due to gelatinization of cellulose in the pretreated and preheated material-still holds.
N THE first article (3) attention was called to the irregularity of the hemicellulose extraction curves, and a tentative explanation was advanced that this irregularity might be due to the Dresence of Dectin in the sugar beet pulp. Thi's assumption has now been put to an experimental test and found to be apparently valid in cases of acid extraction of plant material. OF BEETPULP TABLE I. EXTRACTION The experimental procedure was the Same Pentosans in as in the previous article. All experiments Residue Pentosans Extd. described here were conducted a t 80" C.; the Calcd. Pentosans to %,of % of i n Extd. duration of the extraction was 3 hours. Normality Loss on Loss, Detd., original original total Material, To test the validity of the assumption that of Acid Extn. material pentosans % % % wt., % the break in the curve is due to presence of Extraction of Pulp with HCla pectin in the beet pulp, the latter was ex0.08 0.856 12.3 47.2 6.5 20.0 75.5 42.4 0.957 10.2 0.16 52.8 4.8 21.7 81.9 41.1 tracted with hot 0.5 per cent solution of 0.32 1.043 8.6 57.5 3.7 22.8 86.0 39.7 ammonium oxalate, filtered, washed with hot 1.045 8.3 0.61 57.6 23.0 3.5 86.8 39.9 0.996 0.93 9.7 54.9 22.1 4.4 83.4 40.3 water, and dried. Pulp thus treated is free 1.64 0.971 53.5 10.2 21.8 4.7 82.3 40.7 2.18 1.008 55.6 9.3 4.1 22.4 84.5 40.3 from pectin. It was then extracted in the 3.24 1.074 8.2 59.2 23.2 3.3 87.5 39.2 usual way with acid and alkali and compared Extraction of Treated Pulp with HClb with the original pulp. Table I and the two 0 0.063 3.3 23.4 22.5 ... ... ... corresponding curves of Figure 1 show the 14.1 0.03 29.3 10.3 0.560 12.0 53.8 41.0 0.08 37.4 11.2 0.715 7.0 15.3 68.6 40.9 results of total and pentosan extraction of the 44.1 0.844 0.16 8.3 4.6 17.7 79.4 40.1 original beet pulp with hydrochloric acid. 0.32 0.954 49.9 7.3 3.7 18.6 83.4 37.3 0.61 52.1 0.996 6.9 3.3 19.0 85.2 36.5 The typical maxima and minima of the 0.93 1.004 52.5 6.5 3.1 19.2 86.1 36.6 1.64 1.024 6.4 53.5 3.0 19.3 86.5 36.1 curves appear plainly. The results of extrac2.18 1.048 54.8 6.2 2.8 19.5 87.4 35.6 tion of the treated beet pulp with hydrochloric 3.24 2.2 1.103 5.1 57.7 20.1 90.1 34.8 acid are given in Table I and the two correExtraction of Treated Pulp with NaOHb sponding curves of Figure 1. Examination of 0 0.059 3.1 23.3 22.6 ... ... . . . 0.035 0.615 32.2 18.0 12.2 10.1 45.0 31.4 the data shows that the break in the curves 0.085 14.1 0.915 47.8 7.4 14.9 66.8 31.2 disappeared, and smooth extraction curves 0.18 13.3 0.992 51.9 6.4 15.9 71.3 30.6 0.34 1.056 55.2 11.8 5.3 17.0 76.2 30.8 (for both total and pentosan extraction) 0.73 1.048 54.8 8.8 4.0 18.3 82.1 33.4 1.14 1.177 61.5 6.9 2.7 19.6 87.9 were obtained. No difficulty in filtering was 31.9 1.82 1.215 63.5 4.4 1.6 20.7 32.6 92.8 encountered as was the case when the pulp 2.92 1.265 66.1 2.6 0.9 21.4 96.0 32.4 3.40 1.279 66.9 2.6 0.9 21.4 96.0 32.0 was not subjected to preliminary treatment with ammonium oxalate. When, however, a Two grams pulp 1.814 grams dry material; pentosans in original material, 26.5% on dry basis. the same treated beet pulp was extracted with b Two grams pulp a 1.913 grams dry material: pentosans in treated material, 22.3% on dry basis. sodium hydroxide (Table I, Figure 1) curves were obtained similar to those obtained by
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alkaline extraction of the original beet pulp (Figure 5 of the previous paper, 3). The extraction of pectin had no effect on the subsequent alkaline ext r a c t i o n of b e e t p u l p . Although water under the same conditions extracted 16-17 per cent pentosans from the original beet pulp (Tables IV and VI11 of the previous paper), none was extracted from the treated beet pulp.
Extraction of Sweet Potato
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VOL. 31, NO. 10
TABLE11. EXTRACTION OF SWEIET POTATO PULP"
Normality Loss on of Acid Extraction
0 0.03 0.08 0.17 0.32 0.66 0.99 1.64 2.44 3.24
0.329 0.491 0.587 0.634 0.686 0.726 0.757 0.806 0.861 0.931 1.046
0 0.03 0.06 0.18 0.34 0.70 1.14 1.82 2.86 3.40 5.40 7.13 10.6 17.3
0.339 0.480 0.577 0.684 0.658 0.617 1.020 1.022 1.119 1.135 1.260
2:1
Loss,
%
Pentosana i n Residue Calcd. to Detd., original % wt., %
Extraction of Pulp with HCI 19.1 15.7 3.0 13.6 18.5 5.1 12.5 18.3 6.2 11.4 17.3 7.3 11.2 17.8 7.5 10.2 16.9 8.5 16.0 9.4 9.3 15.5 8.7 10.0
...
...
...
4.7 9.5 14.0 56.7 6.4 2.8 15.9 Extraction of Pulp with NaOH 18.4 19.3 15.7 3.0 26.0 17.4 12.9 5.8 31.3 12.7 10.0 8.7 47.9 5.9 9.4 12.8 4.9 46.5 9.1 13.8 44.3 5.0 13.7 9.0 58.3 2.3 16.4 5.2 55.4 17.0 3.7 1.7 1.2 60.7 3.0 17.5 61.6 2.0 17.9 0.8 2.2
1.295
Pentosarm Extd. Pentosans % of % of in Extd. original total Material, material pentosan8 %
0.7
18.0
16.0 27.3 33.2 39.0 40.1 45.5 49.7 54.6
16.9 19.2 19.5 21.3 20.2 21.5 22.6 22.9
74.9 85.0
27.5 28.0
16.0 31.0 53.5 68.4 73.8 73.3 87.7 90.9 93.6 95.7
16.3 22.3 31.9 26.7 29.7 30.9 29.7 30.7 28.8 29.1
96.3
26.0
...
...
pulp from 32.8 to 2.1 per c e n t . It i s claimed (1, 2 ) that some diastase preparations contain enzymes causing decomposition or inactivation of pect i n s . It would follow, t h e r e f o r e , from the above description of sweet potato pulp that the treated pulp would behave on extraction somewhat similarly to the treated b e e t pulp. T h e data given in Table I1 a n d F i g u r e 2 show this to be the case. R e s u l t s of acid extraction yield a smooth curve, while a distinct break in the curve is observed in case of alkaline extraction.
4 Two grams pulp e 1.844 grams dry material; pentosans in original material, 18.7% Sweet potato pulp on dry basis. is a by-product of b Average, 1.278. sweet potato starch manufacture. The product used in this Acknowledgment investigation was furnished by the Laurel Starch Plant, Laurel, Miss, Like beet pulp, the sweet potato pulp had The starch analyses were made by R. T. Balch of this been subjected to a series of physical and chemical treatdivision. ments and was dried a t an elevated temperature before the Literature Cited final product was obtained. Like beet pulp, sweet potato pulp is known to contain pectin. Unlike beet pulp, from (1) Bourquelot and Herissey, Compt. rend., 127, 191 (1898). which practically all the sugar had been removed, sweet (2) Ehrlich, Biochem. Z.,250, 525: 251, 204 (1932). 31,95 (1939). (3) Yanovsky, IND.ENQ.CHEIM., potato pulp still contains a great deal of starch. It was, therefore, treated with a commercial diastase preparation CONTRIBUTION No. 145 from t h e Carbohydrate Researoh Division, Bureau (amylase). This treatment reduced the starch content of the of Agricultural Chemistry and Engineering.
