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Extraction and characterization of pectins from agricultural byproducts;conventional chemical versus eco-friendly physical/enzymatic treatments

Jongbin Lima, Bockki Mina, Yu Jeong Kima, Sanghoon Koa, Choon Gil Kangb, and Suyong Leea

aDepartment of Food Science and Technology, Carbohydrate Bioproduct Research Center, Sejong

University, Seoul 143-747, Republic of Korea (suyonglee@sejong.ac.kr)bResearch Center, Ottogi corporation, Kyeonggi-Do 431-070, Republic of Korea

ABSTRACT

Pectin from Yuza pomace which is the main waste of fruit juice industry was extracted in an environmentally

friendly way and their structural and physicochemical properties were then compared with those of

chemically-extracted pectin. The combined physical/enzymatic treatments produced pectin with 55%

galaturonic acid content and 7.3% yield which were lower than those of the chemically-extracted pectin. The

pectin sample gained by the physical/enzymatic treatments showed higher degree of esterification (46.30%)

than the chemically-extracted pectin (40.93%) which was also confirmed by FT-IR analysis. When subjected

to steady-shear rheological condition, both pectin solutions were shown to have shear-thinning properties.

Thus, the use of green-labelled pectin can allow the food industry to move toward environmentally friendly

technology and sustainable production.

Keywords: Yuza; Pectin; Eco-friendly; Agricultural by products; Rheology

INTRODUCTION

Yuza (Citrus junos) pomace that accounts for about 10 ~ 15% of Yuza fruit is generated from Yuza juice

extraction[1]and approximately 1,800 tons of the pomace per year are wasted[2]. However, Yuza pomace

with unique flavor contains a variety of useful components. Especially, pectin has become highly valued as a

soluble dietary fiber. Therefore, various efforts to utilize pectin from Yuza pomace have been made. As a

natural and complex polysaccharide, pectin is found primarily in the cell walls where they play an essential

role in cell to cell adhesion[3]. Also, from a food industrial point of view, pectin has been extensively used in

a number of food products such as ice creams, beverages, jellies, and sources due to its typical gelling,

thickening, and stabilizing properties. Pectin has been industrially obtained in a chemical way with strong

acids such as oxalic[4], hydrochloric[5], and sulfuric acid[6]. Thereby, the use of the chemicals may probably

impair the functionality of pectin and cause environmental problems. Therefore, the eco-friendly treatments

have been taken into account for minimizing the use of detrimental chemicals. For examples, natural

catalysis with hemicellulose, protease[7], and microbial enzymes[8]has been applied. Also, several studies

on thermo-mechanical technology such as ultrasound[9], autoclaving[10], and extrusion[11], have been

reported. However, the previous research focused primarily on the yield and chemical composition of the

extracted pectin. Moreover, combined physical/enzymatic treatments have not been carried out yet for

extracting pectin from agricultural byproducts. The aims of this study were to establish the eco-friendly

extraction process by combined physical/enzymatic treatments and to investigate the chemical, structural, andrheological properties of the extracted pectin.

MATERIALS & METHODS

Materials

Yuza pomace provided by Hansung Food Co. (Jeollanam-do, Korea) was dried in an oven at 80 for 24 h

and ground to pass through a 100 mesh sieve.

Pectin extraction

Extraction of pectin from Yuza pomace was performed in two different ways, which were chemical and

combined physical/enzymatic methods. In case of the conventional chemical method[4], the dried Yuza

pomace powder was treated with 85% ethanol at 70for 20 min and filtered with miracloth (Merck KGaA,

Darmstadt, Germany). The residue (10 g) was stirred with oxalic acid/ammonium oxalate (0.25%, pH 4.6,

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400 mL) at 85 for 1 h. The compound was filtered with miracloth, and the filtrate was mixed with three

volumes of 96% ethanol. After centrifugation at 14,500 xg for 10 min, the precipitation was washed with a

series of 70%/96% ethanol and then oven-dried at 50 for 24 h. The combined physical/enzymatic

treatments were also applied to obtain the eco-friendly extracted pectin. The suspension of Yuza powder in

distilled water (5%, w/v) was filtered with miracloth and the residue was mixed with distilled water (5%,

w/v). After autoclaving at 121 for 5 min, the ViscozymeL (Novozymes, Bagsvaerd, Denmark) with 1.210

-4fungal -glucanase unit was added into the suspension, which was kept at 40 for 1 h. Finally, the

suspension was dialyzed (MW 8,000 cutoff, Spectrum Laboratories Inc., CA, USA) and freeze-dried.

Chemical and structural analysis

The degree of esterification of the extracted pectins was measured according to the method of Klavons et

al[12]. The content of galacturonic acid was also determined based on the method of Cozzy and Carpita [13].

The structure of the pectins extracted by two different methods was performed by using a FT-IR spectrometer

(Nicolet Instrument Co., Madison, WI, USA).

Rheological measurements

Rheological measurements were made by using a controlled-stress rheometer (AR1500ex, TA Instruments,

USA) with a 40 mm parallel plate. Shear rates (0.1 - 200/s) were applied for steady-shear viscosity at 25 which were then fitted into the Cross equation.

RESULTS & DISCUSSION

Fig. 1 shows the extraction procedures of pectin from Yuza pomace by two different ways.

Figure 1. Schematic of pectin extraction from Yuza pomace in (a) chemical and (b) eco-friendly ways.

As presented in Table 1, the degree of esterification of the pectins extracted by chemical and combined

physical/enzymatic treatments was determined to be 40.93% and 46.30%, respectively. The previous study

reported that the degree of esterification of Yuza pectin extracted by citrate, tartrate, and HCl was less than

50%, which was in a good agreement with our study. Thus, the pectins extracted by combined

physical/enzymatic treatments could be classified as low methoxyl pectin. Also, the yield of the eco-friendly

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extracted pectin was 7.33%, which was quite similar to that of chemical-extracted pectin. It was reported that

the yield of the pectin from Yuza was typically 4 19%, depending on the extraction methods[14].

The galacturonic acid content of the chemically-extracted pectin was 72.33% while that of the pectin

obtained by combined physical/enzymatic method was 55%. It would be probably due to the increased

solubility of non-pectinous polysaccharides by the combined physical/enzymatic treatments[15].

Table 1. Degree of esterification, yield, and galacturonic acid content of Yuza pectin extracted by chemical and

physical/enzymatic treatments.

Characteristics Chemical extraction Physical/enzymatic extraction

Degree of esterification (%) 40.93 46.30

Yield (%) 8.00 7.33

Galcturonic acid content (%) 72.33 55.00

Fig. 2 exhibits the FT-IR spectra of the pectins which were extracted by two different methods. A band at

3350 cm-1

was observed, which corresponded to hydroxyl groups (OH). In addition, O-CH 3bond stretching

from methyl esters of galacturonic acids was detected at 2930 cm

-1

. It was interesting to note that two bandsassociated with ester carbonyl group and free carbonyl group exhibited at 1740 cm-1

and 1610 cm-1

,

respectively.

Figure 2.FT-IR spectra of Yuza pectin which were extracted by chemical and physical/enzymatic treatments.

The flow behaviors of the pectins extracted by two different methods were investigated under steady-shear

conditions. The apparent viscosity of pectins was increased with an increase in pectin concentration.

Furthermore, the apparent viscosity decreased with increasing shear rates for all samples, showing their

shear-thinning features. Especially, these shear-thinning features became more apparent with increasing

concentrations. The pectin which was extracted by chemical treatment showed Newtonian plateau at low

shear rates and then exhibited shear-thinning features with increasing shear rates. While the pectin obtained

by combined physical/enzymatic treatments appeared shear-thinning features in the range of shear rates

tested in this study which were characterized by the Cross equation as follows;

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Figure 3.Flow behaviour of Yuza pomace pectin extracted by chemical and physical/enzymatic treatments.

CONCLUSION

The combined physical/enzymatic treatments were applied to extract pectin from Yuza pomace in an eco-

friendly way. Hydrothermal treatments with enzymatic assistance produced low methoxyl (46.3%) Yuza

pectins with 55% galacturonic acid. The pectins extracted by the combined physical/enzymatic treatments

showed shearing-thinning properties which were fitted well into the Cross equation. The eco-friendly pectin

would be utilized to control the rheology and texture of food products as much as chemically-extracted pectin

and furthermore provide positive benefits with possible natural green-labeling.

REFERENCES

[1] Lee H.Y., Kim Y.M., Shin D.H. & Sun B.K. 1987. Aroma Components in Korean citron (Citrus medica). Korean

Journal of Food Science and Technology. 19(4), 361-365.

[2] Kim D.S., Kim D.H., Oh M.J., Lee K.G., Kook M.C. & Park C.S. 2010. Antiaging and Whitening Activities of

Ethanol Extract of Yuza (Citrus junos SIEB ex TANAKA) By-product. Journal of the Society of Cosmetic Scientists

of Korea. 36(2), 137-143.

[3] Mcneil M., Darvill A.G., Fry S.C. & Albersheim P. 1984. Structure and Function of the Primary Cell Walls of Plants.

Annual Review of Biochemistry. 53, 625-663.

[4] Koubala B.B., Kansci G., Mbome L.I., Crepeau M.J., Thibault J.F. & Ralet M.C. 2008. Effect of Extraction

Conditions on some Physicochemical Characteristics of Pectins from Amliore and Mango Mango Peels. Food

Hydrocolloids. 22(7), 1345-1351.

[5] Hwang J.K., Kim C.J. & Kim C.T. 1998. Extrusion of Apple Pomace Facilitates Pectin Extraction. Journal of Food

Science. 63(5), 841-844.

[6] Garna H., Mabon N., Robert C., Cornet C., Nott K., Legros H., Wathelet B. & Paquot M. 2007. Effect of Extraction

Conditions on the Yield and Purity of Apple Pomace Pectin Precipitated but Not Washed by Alcohol. Journal of Food

Science. 72(1), C001-C009.

[7] Zykwinska A., Boiffard M.-H.l.n., Kontkanen H., Buchert J., Thibault J.-F.o. & Bonnin E. 2008. Extraction of Green

Labeled Pectins and Pectic Oligosaccharides from Plant Byproducts. Journal of Agricultural and Food Chemistry.

56(19), 8926-8935.

[8] Ptichkina N.M., Markina O.A. & Rumyantseva G.N. 2008. Pectin Extraction from Pumpkin with the Aid of Microbial

Enzymes. Food Hydrocolloids. 22(1), 192-195.

[9] Panchev I., Kirchev N. & Kratchanov C. 1988. Improving Pectin Technology. International Journal of Food Science

& Technology. 23(4), 337-341.

[10] Oosterveld A., Beldman G., Schols H.A. & Voragen A.G.J. 2000. Characterization of Arabinose and Ferulic Acid

Rich Pectic Polysaccharides and Hemicelluloses from Sugar Beet Pulp. Carbohydrate Research. 328(2), 185-197.

8/12/2019 FEW266

5/5

[11] Shin H.H., Kim C.T., Cho Y.J. & Hwang J.K. 2005. Analysis of Extruded Pectin Extraction from Apple Pomace by

Response Surface Methodology. Food Science and Biotechnology. 14(1), 28-31.

[12] Klavons J.A. & Bennett R.D. 1986. Determination of Methanol using Alcohol Oxidase and Its Application to

Methyl Ester Content of Pectins. Journal of Agricultural and Food Chemistry. 34(4), 597-599.

[13] Filisetti-Cozzi T.M.C.C. & Carpita N.C. 1991. Measurement of uronic acids without interference from neutral sugars.

Analytical Biochemistry. 197(1), 157-162.

[14] Park S.M., Lee H.H., Chang H.C. & Kim I.C. 2001. Extraction and Physicochemical Properties of the Pectin in

Citron Peel. Journal of the Korean Society of Food Science and Nutrition. 30(4), 569-573.

[15] Min B., Lim J., Ko S., Lee K.G., Lee S.H. & Lee S. 2011. Environmentally Friendly Preparation of Pectins from

Agricultural Byproducts and their Structural/rheological Characterization. Bioresource Technology. 102(4), 3855-

3860.