Scholarly article on topic 'Novel source of pectin from young sugar palm by microwave assisted extraction'

Novel source of pectin from young sugar palm by microwave assisted extraction Academic research paper on "Agriculture, forestry, and fisheries"

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{"Sugar palm" / "Palmyra palm" / pectin / extraction / "microwave assisted extraction"}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Supitcha Rungrodnimitchai

Abstract In this work, pectin extraction was performed using ripened sugar palm meat and young sugar palm meat as raw materials. The effect of extraction temperature and pH on the yield of pectin was investigated. It was found that the degree of esterification and galacturonic acid content decreased at high pH condition. The ripened sugar palm could give pectin as high as 20% yield at extraction condition of pH 2, 80°C, while the young sugar palm gave only 8.1% yield at pH 3. It was found that the adjustment of pH before and after extraction largely affected the yield of extraction. On the other hand, the extraction of young sugar palm meat at microwave power 800W at pH 2 with 3minutes of duration yielded as high as 23.5% of pectin. The results suggested that sugar palm meat had high potential as a new pectin source.

Academic research paper on topic "Novel source of pectin from young sugar palm by microwave assisted extraction"

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Procedía FoodSciencel (2011) 1553-1559

Procedía

Food Science

11th International Congress on Engineering and Food (ICEF11)

Novel source of pectin from young sugar palm by microwave

assisted extraction

Supitcha Rungrodnimitchai *

Department of Chemical Engineering, Faculty of Engineering, Thammasat University, Phatumthani 12120 Thailand

Abstract

In this work, pectin extraction was performed using ripened sugar palm meat and young sugar palm meat as raw materials. The effect of extraction temperature and pH on the yield of pectin was investigated. It was found that the degree of esterification and galacturonic acid content decreased at high pH condition. The ripened sugar palm could give pectin as high as 20% yield at extraction condition of pH 2, 80oC, while the young sugar palm gave only 8.1% yield at pH 3. It was found that the adjustment of pH before and after extraction largely affected the yield of extraction. On the other hand, the extraction of young sugar palm meat at microwave power 800 W at pH 2 with 3 minutes of duration yielded as high as 23.5% of pectin. The results suggested that sugar palm meat had high potential as a new pectin source.

©2011PublishedbyElsevierB.V.Selection and/or peer-review underresponsibilityof11thInternationalCongress onEngineeringandFood(ICEF 11)Executive Committee.

Keywords: Sugar palm; Palmyra palm; pectin; extraction; microwave assisted extraction

1. Introduction

Pectin is a polysaccharide, also known as a water-soluble fibre. It is employed in both food and pharmaceutical industry as a gelling agent and a functional food. Pectin is commercially extracted from citrus peels and apple pomace. Recently, dielectric heating or microwave heating becomes attractive technique for improving extraction yield and quality of pectin from various sources. Application of microwave assisted extraction on orange peels was reported by several research groups [1-4]. Pre-treatment of orange peels raw by microwave was found to improve extraction yield and quality of pectin [2]. Zhongdong and co-workers showed by the image study that 10 minutes of microwave irradiation

* Corresponding author. Tel. & fax: +66-2564-3007. E-mail address: supitcha@engr.tu.ac.th.

2211-601X © 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of 11th International Congress on Engineering

and Food (ICEF 11) Executive Committee.

doi:10.1016/j.profoo.2011.09.231

disintegrate the orange skin tissue than 18 hours of traditional heating. Recently, microwave assisted extraction of lime pectin and apple pomace were also intensively studied [5,6].

Fig. 1. (Left) Sugar palm trees, (Right) Sugar palm fruits

Sugar palm or Asian Palmyra palm is found in south-east Asian and south Asian countries. Palm sugar can be obtained from the young inflorescence. Its jelly seed is served as fruit. The ripened outer layer of the palm fruits can also be eaten raw, boiled, or roasted, while the young sugar palm is a waste in large scale from canning industry. In our previous work, we found that the ripened sugar palm meat yielded obtained pectin as high as 20% of dry weight [7]. In this work, we performed pectin extraction on both ripened and young sugar palm and applied the microwave heating on the extraction of young sugar palm.

2. Materials & Methods

2.2. Materials & Apparatus

Ripened sugar palm meat and young sugar palm meat were obtained from Saraburi province and Petchaburee province, Thailand. Sodium hydroxide (Ajax Fine Chem), Hydrochloric acid (37% , Carlo Erba), Ethyl alcohol (95%), Carbazole (96%, Fluka), D-(+)-Galacturonic acid (97%, Fluka), and sulfuric acid (96%, Carlo Erba Reagents) were reagent grade or analytical grade and used as received.

The microwave oven was Electrolux EMM 2005, which can adjust its power within the range of 300800 W. The reaction temperature was adjusted constantly by a temperature controller. The conventional heater was from Grant instrument (W28) with a power of 1500 W.

2.2. Matha/s

10 g of a sugar palm meat was blended with 300 mL of distilled water by a mixer. The pH of the mixture was adjusted using 0.25 M NaOH solution or 0.25 M HCl solution. Then the mixture was heated by water bath or microwave oven. The solid residue was removed by filtration. The obtained solution was concentrated to 50 mL using vacuum evaporator. If necessary, pH of the solution was adjusted before addition of 150 ml of ethanol lead to the formation of pectin precipitation. The solution was kept at room temperature for 2 hours before filtration. The solid was dried in an oven at 80oC for 8 hours. The color of pectin from ripened sugar palm was yellow. On the other hand, the color of pectin from young sugar palm was white.

2.3. Determination of degree of esterification (DE)

50 mL of de-ionized water was added to dried pectin (0.1 g) in a 100 mL beaker, and the solution was stirred at room temperature for 12 hrs. 0.1 M NaOH solution was dropped to the solution until the change of phenolphthalein color. Then 25 mL of 0.25 M NaOH solution was added to the sample and stirred for 30 min. Next, 25mL of 0.25 M HCl solution was added to the sample. Excess HCl was titrated by 0.1 M NaOH solution with the presence of methyl red as an indicator. The number of esterified carboxy group was calculated from the volume of 0.1 M NaOH used in the titration.

2.4. Determination of galaturonic acid (GA) unit content

5 mL of sulfuric acid (98%) was added to 5 mL of 100 ppm of pectin solution. Then 200 |L of 0.1%v/v carbazol solution was added to the sample. The sample was heated at 58-60oC for 1 hour and cooled down to room temperature. The absorbance was measured at 527 nm against a reagent blank. The total galaturonic acid unit content in sample was derived from the calibration curve using standard solution of galaturonic acid at the same condition.

3. Results & Discussion

3.1. Effect of extraction temperature, raw material and pH

The extraction conditions for investigation of the effect of raw materials, temperature and pH are listed in Table 1. In this work, ripened palm meat or young palm meat was used as raw materials. Firstly, the extraction was performed at pH 2 for 1 hour with 30 or 20 times of water as extraction solvent. The temperature for extraction was varied to 60, 80 and 100oC, respectively.

Table 1. Extraction conditions for investigation of the effect of raw materials, temperature and pH

Ratio of water to

Samples palm meat by Temperature (oC) pH Time (hrs)

weight

Ripened T60 pH2 60

Ripened T80 pH2 30 80 2 1

Ripened T100 pH2 100

Ripened T80 pH2 2

Ripened T80 pH3 3

RipenedT80 pH4 4

Ripened T80 pH5 30 80 5 1

Ripened T80 pH6 6

Ripened T80 pH8 8

Ripened T80 pH9 9

YoungT60 pH3 60

YoungT80 pH3 20 80 3 1

YoungT100pH3 100

YoungT80 pH3 3

YoungT80 pH4 20 80 4 2

YoungT80 pH5 5

YoungT80 pH6 6

According to the result in Figure 2, it was found that 80oC was the optimum temperature for both ripened and young palm meat. However, the yield from young palm meat was quite lower than those of ripened palm meat. Since the meat of young palm is quite harder than the meat of ripened palm, the meat of ripened palm could be dispersed in water more easily than the young palm meat. This may cause the difference of dissolution of pectin into the extraction solvent.

Similar results were observed in Figure 3. For ripened palm, yield of extraction increased as an increase of pH. On the other hand, GA and DE decreased as an increase of pH. Although the alkaline condition gave high yield as in acidic condition, it was reported that alkaline conditions usually caused decomposition of pectin molecules [8]. Consequently, the optimum pH for extraction of ripened palm was 4. In the case of young palm, it was found that low pH condition yield higher extraction yield, GA and DE. This result is supported from another experiment, which is listed in Table 2. Sample Young-pH 2, which was obtained from extraction at pH 2 gave the highest extraction yield at 13.3%. So that pH 2 was used for further extraction of young palm.

Supitcha Rungrodnimitchaia / Procedia Food Science 1 (2011) 1553 -Table 2. Conditions for extraction and precipitation pectin from young sugar palm meat

Samples

Ratio of water to palm meat( wt)

Temperature

Time (hrs) Extraction pH Precipitation pH Yield (%)

Young pH2 Young pH3 Young pH4

13.3 10.0 4.0

method 1 method 2 method 3 method 4

N.A. N.A. 4.6 12.1

The effect of precipitation conditions was examined in Table 2. The results showed that method 1 and method 2, which had no pH adjustment during extraction yielded little amount of pectin. On the other hand, when pH of the system was kept at 3 during extraction and precipitation (addition of ethanol), the yield was only 4.6%. Surprisingly, Method 4 which its extraction pH was 3, and precipitation pH was 7 yielded as high as 12.1%. Considering the effect of pH on molecular structure of pectin, it may be explained as in Figure 4. In acidic condition, the unit of pectin molecules are in form of galacturonic acid or methyl ester, which is non-ionic compound. When the galacturonic acid is neutralized by NaOH, the unit of galacturonic acid is converted into galacturonate sodium salt, which is ionic compound. This leads to difference in solubility in ethanol (precipitation solvent). Since ionic compound of the sodium salt form is less soluble in organic solvent, more pectin molecules could be precipitated by ethanol at pH 7 than at pH 3.

In acid solution

oh H \ " /1 -O H

COO Na

In neutralized solution

OH H \ H / -O H

Fig. 4. Concept for precipitation in neutralized condition

3.2 Effect of microwave heating

Microwave heating was applied for pectin extraction from young palm. The effect of microwave power and extraction temperature on extraction yield was investigated. The extraction was performed using method 4 by fixing extraction pH at 2 and precipitation pH at 7. The extraction conditions are summarized in Table 3.

Table 3. Conditions for microwave assisted extraction of young sugar palm at 3 minutes

samples Water (times) pH MW Power (W) Temperature (°C )

Young MW600T70 30 2 600 70

Young MW600T80 30 2 600 80

Young MW600T90 30 2 600 90

Young MW700T70 30 2 700 70

Young MW700T80 30 2 700 80

Young MW700T90 30 2 700 90

Young MW800T70 30 2 800 70

Young MW800T80 30 2 800 80

Young MW800T90 30 2 800 90

25 23.5

Fig. 5. Effect of microwave power and temperature on extraction yield from young palm

According to Figure 5, microwave power at 800 W for 3minutes gave as high as 19.6-23.5% of extraction yield. Even the extraction at microwave power at 600 W for 3minutes yielded about 10-13%, which were comparable to 2 hours of extraction by conventional heating. To shorten the extraction time is known as one of great advantage for microwave assisted extraction. In this case, microwave is considered to have a large contribution on disintegration of hard young sugar palm meat.

It was found that 90oC was the optimum temperature for extraction for all microwave power. The attempt on 2, 3, 4 minutes of extraction at 90oC confirmed that the 3 minutes of extraction time yielded the highest extraction efficiency. The information for GA and DE of pectin from young palm from microwave assisted extraction is the next step for our research.

4. Conclusions

Pectin extraction was performed using ripened sugar palm meat and young sugar palm meat as raw materials. By conventional heating method, the ripened sugar palm could give pectin as high as 20% yield at extraction condition of pH 2, 80oC, while the young sugar palm gave only 8.1% yield at pH 3. It was found that galacturonic acid content and the degree of esterification decreased at alkaline conditions. The adjustment of pH to be 7-8 precipitation drastically increased the yield of extraction. On the other hand, the extraction of young sugar palm meat at microwave power 800 W at pH 2 for 3 minutes yielded as high as 23.5% of pectin. The result suggested that sugar palm meat had high potential as a new pectin source.

Acknowledgement

This research is supported by Thammasat University research fund.

References

[1] Fishman ML, Chau HK, Hoagland P, Ayyad K. Characterization of pectin, flash-extracted from orange albedo by microwave heating under pressure. Carbohydrate Research 2000; 323:126-138.

[2] Kratchanova M, Pavlova E, Panchev I. The effect of microwave heating of fresh orange peels on the fruit tissue and quality of extracted pectin. Carbohydrate Polymers 2004; 56: 181-185.

[3] Zhongdong L, Guohua W, Yunchang G, Kennedy JF. Image study of pectin extraction from orange skin assisted by microwave. Carbohydrate Polymers 2006; 64: 548-552.

[4] Yeoh S, Shi J, Langrish TAG. Comparisons between different techniques for water-based extraction of pectin from orange peels. Desalination 2008; 218: 229-237.

[5] Fishman ML, Chau HK, Hoagland PD, Hotchkiss AT. Microwave-assisted extraction of lime pectin. Food Hy/rdcdlldi/s 2006; 20: 1170-1177.

[6] Wang S, Chen F, Wu J, Wang Z, Liao X, Hu X. Optimization of pectin extraction assisted by microwave from apple pomace using response surface methodology. Journal of Food Engineering 2007; 78: 693-700.

[7] Yujaroen P, Subjaroenkul U and Rungrodnimitchai S. Extraction of Pectin from Sugar Palm Meat. Thammasat International of Science and Technology 2008; 13: 44-47.

[8] Albersheim P, Neukom H and Deuel H. Splitting of pectin chain molecules in neutral solution. Archives of Biochemistry and Biophysics 1960; 90: 46-51.

Presented at ICEF11 (May 22-26, 2011 - Athens, Greece) as paper FPE642.