Chemical Constituents of Sugar-Containing Sap and Brown Sugar from Palm in Indonesia

Jpn. J. Trop. Agr. 40(4): 175-181, 1996

Atsunobu TOMOMATSU,Takatoshi ITOH*, C. Hanny WIJAYA*2, Zein NASUTION*2, John KUMENDONG*2,and Aklra MATSUYAMA*3

Faculty of International Studies, Utsunomiya University, Mine-Machi 350 * Faculty of Agriculture , Utsunomiya, 321 Japan , Tohoku University, Sendai, 981 Japan *2Faculty of Agricultural Engineering and Technology , Bogor Agricultural University, Bogor, Indonesia *3NODAI Research Institute , Tokyo University of Agriculture, Sakuragaoka 1, Setagaya-ku, Tokyo, 156 Japan

Abstract Sugar-containing sap obtained from Indonesian palm trees by traditional methods and brown sugar

produced from it were analyzed for general, sugar and organic acid compositions. Fresh sap collected from sugar

palm (Arenga pinnata Merr.; aren/enau in Indonesian), palmyra palm (Borassus flabellifer L.; siwalan/lontar), nipa palm (Nypa fruticans Wurmb.; nipah), and coconut palm (Cocos nucifera L.; kelapa) contained 10 to 13% of sugars which consisted mainly of sucrose. When fresh sap from sugar, palmyra and nipa palms was incubated , significant amounts of glucose and fructose and some amounts of oligosaccharides were generated by the action of micro-

organisms. The sap from palmyra, nipa and coconut palms contained succinic acid as a dominant organic acid while sugar palm contained malic acid. Incubation of the fresh sap from sugar and nipa palms for one day resulted

in the increase in the content of lactic acid. The ratio of reducing sugar to total sugar in fresh sugar palm sap

increased remarkably from 12.5 to 90.1% by incubation at 30•Ž for 16 hrs . Higher ratios ranging from 36.1 to 43.

0% were recorded for brown sugar from sugar, palmyra and coconut palms . Key words Brown sugar, Indonesia, Organic acid, Palm sap, Reducing sugar , Sucrose

インドネシアのヤシの樹液と黒糖の化学的組成友松篤信・*伊藤敞敏・*2ハニーウィジャヤ・*2ゼインナスティオン・*2ジョンクメンドン・*3松山晃宇都宮大学国際学部〒321宇都宮市峰町350*東北大学農学部〒981仙台市青葉区堤通雨宮町1*2ボゴール農科大学農業工学・技術学部ボゴール市インドネシア*3東京農業大学総合研究所〒156東京都世田谷区桜ヶ丘1

要約インドネシアのヤシ花茎から伝統的手法により採取した樹液と,それから作られる黒糖の一般分析および糖・有機酸の定量分析を行った.砂糖ヤシ(Arenga pinnata Merr.),パルミラヤシ(Borassus flabellifer L.),ニッパヤシ(Nypa fruticans Wurmb .) およびココヤシ(Cocos nucifeya L.)からの樹液は10～13%の糖を含み,その大部分はショ糖であった.樹液をインキュベートするとショ糖は微生物の作用により加水分解され,大量のブドウ糖および果糖と若干のオリゴ糖が生じた.パルミラヤシ,ニッパヤシ及びココヤシはコハク酸,砂糖ヤシはリンゴ酸の含量が最も高かった.砂糖ヤシとニッパヤシの樹液をインキュベートすると乳酸が顕著に増加した.樹液の糖全体に占める還元糖の比率はインキュベートによって12.5%から90.1%に顕著に増加した.黒糖における還元糖比は36.1～43.0%であり,通常法によりサトウキビ搾汁から製造された黒糖の還元糖比より著しく大きかった. キーワードインドネシア,還元糖,黒糖,ショ糖,ヤシ樹液,有機酸

Introduction ever, are not available. Sap is usually collected with a bamboo Several species of palms are used as sugar tube from the stalk of the male flower. The sources in the tropical regions of the world. methods of treatment of the flower prior to The product which is generally called palm harvesting steps seem to be similar in India1) sugar is an important sweetener for the peo- and in Indonesia. The unopened flower spathe ple in palm-growing areas. In Indonesia, is prepared by tight binding to prevent it from sugar-containing sap is obtained from four opening; gentle tapping with a mallet; gradual kinds of palms: sugar, palmyra, nipa and bending; and final cutting1). Sap starts to coconut palms. Sugar palm has the highest exude from the opening of the cut stalk. capacity of sap production per day (Table 1). The sap is prone to be spoiled easily by The data on annual production per tree, how- contamination with microorganisms. Sponta- neously semi-fermented non-alcoholic bever- Received Mar. 5, 1996 age (nira) is popular as a traditional beverage Accepted Aug. 26, 1996 in palm-growing areas of Indonesia. The sap 176 Jpn. J. Trop. Agr. 40(4) 1996

Table 1. Palm used as sugar resources in Indonesia and the yield of sap.

Table 2. Brown sugar production and resource plant in Indonesia in 1982.

: Resource plant Source : Central Bureau of Statistics

in a bamboo tube is sold by glass at local substance. Brown sugar called gula merah in markets in Java and Sulawesi. Palm wine, Indonesia is used as a sweetener with special tuak, is also obtained from the sap by sponta- flavor for a variety of Indonesian foods as neous fermentation naturally. well as for the preparation of soy sauce The sap is condensed in a pan by direct (kecap) and soybean paste (tauco). heating until the crystalline form begins to The production of brown sugar from palm appear in a thick syrup. The viscous mass is sap is an important village industry. West poured into such a mold as a hemispherical and Central Java, and South Sulawesi are the coconut shell to form solid cakes of the sweet three major production areas which account

•› TOMOMATSUet al.: Chemical Constituents of Palm Sap 177 for 86.4% of the total national production in furnace. Indonesia. Sugar palm is the most widely Paper chromatograthv (PC) of suisars used palm for brown sugar production (Table PC of sugars was performed on Toyo No. 2). There are no sugar palm plantations in 51 filter paper using a solvent system of n- Indonesia and sugar palm is a component of butanol-pyridine-water (6:4:3, v/v). After the natural vegetation in highland or moun- development with the solvent system was tainous regions. repeated three times at room temperature, the The purpose of this study was to examine filter paper was stained with a silver nitrate the chemical composition of sap as raw mate- solution according to the methods of ROBYT rial for palm sugar and the chemical charac- and FRENCH9). teristics of palm sugar. Analysis of sugars and organic acids using a high pressure liquid chromatograph (HPLC) Materials and Methods Sugars in sap and palm sugar were ana- Materials lyzed using a HPLC (Hitachi 635S) with an The fresh sap from sugar and coconut 834-50 integrator. The sap and palm sugar palm trees was collected in Cianjur, West dissolved in water were applied to the equip- Java. The sap was also obtained from pal- ment and eluted through a column packed myra and nipa palms in Jeneponto, South with Hitachi custom ion exchange resin # 2618

Sulawesi and Manokwari, Irian Jaya (West (0.4•~50cm) with water at a flow rate of 0.2 New Guinea), respectively. A sample of sap ml/min at 40•Ž. The elution was monitored was taken within one hr after fixing a con- using a Shodex refractive index monitor tainer to a stalk of the inflorescence or flower model SE-11. spathe of palm trees. Samples were cooled To analyze the organic acids in the sap, 10 immediately after collection and kept frozen g of sample was acidified to below pH 2 by 3 until they were analyzed. Commercial sap N HCI, then extracted with ethyl ether for 30 was purchased at a local market in Bogor, hr in a Soxhlet apparatus. The extract was West Java. alkalized with 2N NH4OH, then ether was Analysis of general composition evaporated off. The remaining water layer Three ml of a sample was taken in a flat was collected in a 10ml volumetric flask and -bottom glass dish 3cm in diameter and filled with water after acidification with 2 N accurately weighed, then heated on a steam phosphoric acid to about pH 2. The extract bath until moisture was almost evaporated. was applied to a HPLC equipped with the The dried sample was then heated in an air same column and eluted with 0.05% phos- oven at 110•Ž for 5 hr. After cooling in a phoric acid at a flow rate of 0.3ml/min at desiccator for 30 min, the sample was weighed 50•Ž . The elution was monitored by optical for estimating the amount of total dry matter. absorbance at 210nm. Nitrogen content was determined by the semi-micro KJELDAHL method. About one g of Results sample was digested by heating with sulfuric General analysis of sap acid containing CuSO4 and K2SO4 as a cata- The general analysis of the sap from four lyzer. A factor of 6.25 was used for conver- kinds of palm trees indicated that sugar was a sion to protein content. major component accounting for 10 to 13% of Sugar content was measured by the phenol the sap components. The sample from nipa -sulfuric acid method2) . Five ml of concen- palm showed the highest percentage of sugars trated sulfuric acid was added to 2ml of a (13.3%). Ash and protein were minor compo- diluted sample mixed with 0.1ml of 80 nents in all the samples (Table 3). phenol solution. Optical density of the reac- Analysis of sugars in fresh and incubated sap tion mixture was measured at 490nm. using PC Ash content was determined by heating a The composition of the sugars in the sap sample in an electric furnace at 600•Ž for 3 hr. was analyzed using PC (Fig. 1). Fresh sam- The sample was well carbonated in a crucible ples from sugar, palmyra and coconut palms on a small gas flame before it was put into a contained only sucrose on the chromatogram. 178 Jpn. J. Trop. Agr. 40(4) 1996

Table 3. General composition of the sap from oligosaccharides such as fructooligosacca- palm trees in Indonesia. rides produced from two reducing sugars. In the fermented saps from palmyra and nipa palms the number of spots in a higher molecular weight region was reduced to only two (sample no. 9 and 10). Comparative analysis of sugars in sugar palm sap and sugarcane juice using a HPLC Chromatograms of sugar palm sap using a HPLC equipped with a refractive index moni- *Other trace components such as lipids, acids, etc. may be tor showed that the fresh sap from sugar palm contained. contained a higher concentration of sucrose than freshly prepared sugarcane juice (Fig. 2).

Fig. 1. Paper chromatogram of sugars in the fresh and fermented saps from palm trees. S: standard; 1: sugar palm, fresh; 2: palmyra palm, fresh; 3: coconut palm, fresh; 4: nipa palm, fresh; 5, 6, 7, and 8: sugar Fig. 2. HPLC chromatogram of sugars in the palm, kept at ambient temperature for fresh, incubated and commercial saps 12hr,1 day, 2 days, and 3 days, respective- from sugar palm and in sugarcane juice. ly; 9: palmyra palm, fermented; 10: nipa Incubation was conducted at 30•Ž for 16 palm, fermented. a: fructose; b: glucose; hr. The same volume of the fresh and c: sucrose; d: maltose. Spot intensity incubated saps and four times volume of indicates difference of staining. the commercial sap were applied to HPLC.

Three minor components were detected in addition to sucrose in the fresh sap from nipa The sap from sugar palm, commercial or

palm. A part of sucrose in the sugar palm sap incubated at 30•Ž for 18 hr, contained a larger kept at ambient temperature (25-30•Ž) was amount of glucose and fructose, and unknown hydrolyzed 12 hr after collection (sample no. higher and lower molecular weight sub- 5). One day after collection sugars with a stances. The chromatograms indicated that higher molecular weight than sucrose were the hydrolysis of sucrose took place and that detected (sample no. 6). At three days after unknown substances were synthesized in a collection, sucrose was hydrolyzed almost sample contaminated with microorganisms at completely to generate glucose, fructose and and after sample collection. These results TOMOMATSVet al.: Chemical Constituents of Palm Sap 179 demonstrate that the commercial palm sap Ratio of reducing sugar to total sugar was in a partially fermented state. The composition of sugars in the fresh and Analysis of organic acids in fresh and in- semi fermented sugar palm saps, and brown cubated sap using a HPLC sugar was examined using a HPLC (Fig. 3). Seven species of organic acids were The ratio of reducing sugar (glucose and identified by comparing the retention time fructose) to total sugar (sucrose, glucose and with standard materials in both saps collected fructose) was calculated from the data freshly and kept at ambient temperature (25 obtained by quantitative analysis using a -30•Ž) for one day (Table 4) . The fresh sap HPLC (Fig. 3). The ratio for fresh sugar palm from sugar palm contained the largest sap (12.5%) was almost equivalent to that of amount of malic acid on a weight basis, while sugarcane juice (15.2%). The ratio increased the saps from palmyra, nipa and coconut remarkably to a value of 76.9% (commercial palms contained succinic acid. When the saps sap) and 90.1% (incubated sap) by spontane- from the sugar and nipa palms were kept at ous fermentation in the sap. The ratio for ambient temperature, the content of lactic brown sugar of different origins ranged from acid increased markedly. 36.1% (coconut palm no. 1) to 43.0% (palmyra

Table 4. Composition of organic acids in the sap from palm trees in Indonesia.

* Kept at ambient temperature (25-32•Ž) for one day .

Fig. 3. Weight composition of sugars in sugarcane juice, sugar palm sap and palm brown sugar .

• glucose •¬fructose •¡ sucrose 180 Jpn. J. Trop. Agr. 40(4) 1996 palm). comparable to that of sugar cane juice (Fig. 2). However, the yields of sugar per ha of Discussion sugar palm is obviously lower than that of What is the origin of the sap which exudes sugarcane. Advantages in the cultivation of from the cut stalk of a male inflorescence of sugar-producing palm involve the continuous palm trees? Phloem sap contained 15.4% (w/ supply to the village sugar industry. The v) of sucrose as the highest content among flavor of brown sugar from sugar, palmyra other solid materials; while sucrose was not and coconut palms is not appreciably differ- detected in the xylem sap10). The component ent from that of non-centrifugal sugar from of the sap obtained from palm trees by tradi- sugarcane with identified 38 substances7). tional methods was very similar to the phloem However, palm brown sugar is preferred in sap judging from the content of sucrose. It is such traditional Indonesian cooking as sate highly plausible that the sap obtained from ayam, chicken barbecued with Indonesian soy palm trees originates mainly from the phloem sauce (kecap). Several hundred tons of palm sap. brown sugar are exported annually to such The oligosaccharides such as neighboring countries as Thailand and fructooligosaccarides in incubated or com- Malaysia. Palm sugar has been and will mercial sap may be produced from glucose, remain a unique Indonesian product in the fructose and sucrose by the transglycosyla- same way as maple sugar in North America. tion activities of sucrose ƒ¿-glucosidase (su- Acknowledgments crase) from microorganisms. Other hydrolases such as a-amylase3) could also The authors wish to thank all the mem- take part in transglycosylation reactions. It bers of the Faculty of Agricultural Engineer- is still unclear whether the minor oligosac- ing and Technology, Bogor Agricultural Uni- charides in the fresh sap (Fig. 2) were synthe- versity for their cooperation and assistance. sized by such a reaction. It is also possible The authors also wish to mention that this that oligosaccharides are original components study was conducted under The Agricultural of the sap collected from palm trees because Products Processing Pilot Plant Project raf f inose (trisaccharide), stachyose (tetrasac- which was implemented as technical coopera- charide) and other oligosaccharides were tion by the Japan International Cooperation found in the phloem saps of woody plant Agency from 1977 to 1984 at Bogor Agricul- families10) tural University. Palm sap is sold on the street or at the References market as a popular beverage called nira. A large part of the sweet taste is mainly derived 1. CHILD, R. 1964 Coconuts. Longman, Green & from fructose and glucose (Fig. 3). The spe- Co. Ltd. (London) pp.216. cial sour taste may be due to the variety of 2. DUBOIS,M., K.A. GILLES, J.K. HAMILTON,P.A. ROBERS and F. SMITH 1956 Colorimetric organic acids which are generated by sponta- method for determination of sugars and neous fermentation (Table 4). Palm sap is related substances. Anal. Chem. 28: 350-356. used for the production of brown sugar (gula 3. HEHRE, E.J., G. OKADA and D.S. GENGHOF 1969 merah) as well as the traditional beverage. Configurational specificity: unappreciated Brown sugar from palm sap has a much key to understanding enzymic reversions and higher content of reducing sugars compared de novo glycosidic bond synthesis 1. Reversal to non-centrifugal sugar from sugarcane of hydrolysis by ƒ¿-, ƒÀ- and glucoamylases with donors of correct anomeric form. Arch. which contains 1.75 to 5.57% of reducing Biochem. Biophys. 135: 75-89. sugar in total solid matter8). The sap is 4. JATMIKO,A., M.A. HAMZAHand D. SIAHAAN concentrated in a pan by direct heating and 1990 Methods for alternative products from then solidified by cooling after pouring into a the sap from coconut palm (in Indonesian). mold. The time between the collection and Manggar 3: 47-57. 5. KINDANGEN,J.G., N.M. MOKODONGANand M. processing (heating) seems to be a determin- DAJAR 1989 Income of palm sugar farmers in ing factor of the composition of palm sugar. seashore transmigration areas in Riau prov- The sugar content of the palm sap was TOMOMATSUet al.: Chemical Constituents of Palm Sap 181

ince (in Indonesian). Buletin Balitka 9: 68-73. quality and constituents of non-centrifugal 6. MAHMUD,Z., D. ALLORERUNGand AmRIZAL 1991 sugar (Kokuto) processed by mills in Okin- Prospect of sugar production by coconut, awa. Bull. Coll. Agr. Univ. Ryukyus 36: 67-72. sugar, palmyra and gewang palms (in In- 9. ROBYT,J. and D. FRENCH1963 Action pattern donesian). Ibid. 14: 90-105. and specificity of an amylase from Bacillus 7. MATSUYAMA,A. 1994 Traditional dietary cul- subtilis. Arch. Biochem. Biophys. 100: 451 tures in Java (in Japanese). Aminosan Kyou- -467 . kai Gizyutsubukaihou 233: 1-54. 10. SALISBURY,F.B. and C.W. Ross 1992 Plant 8. NAKASONE, Y., M. SIMO, N. TAMASHIRO and Y. Physiology (4th edition). Wadsworth Publish- HOSOYAMADA 1989 Relationships between the ing Co. (California) pp.682.