BY-NC-ND 3.0 license Open Access Published by De Gruyter June 28, 2014

Quantification of Inulin Content in Selected Accessions of Jerusalem Artichoke (Helianthus tuberosus L.)

J. Brkljača, M. Bodroža-Solarov, J. Krulj, S. Terzić, A. Mikić and A. Marjanović Jeromela
From the journal Helia

Abstract

Jerusalem artichoke is an excellent source of inulin. Inulin has valuable nutritional and functional attributes, and therefore it is needed to know inulin content in different accessions of Jerusalem artichoke tubers. We used rapid high-performance liquid chromatography (HPLC) method following water extraction to determine inulin content in Jerusalem artichoke tubers. HPLC conditions included Rezex RCM-monosaccharide Ca2+ column, deionized water as mobile phase and light scattering detection. It was found that inulin content of Jerusalem artichoke tubers ranged from 8.16 to 13.46% of fresh weight. The maximum value of inulin content in 12 accessions of Jerusalem artichoke was detected in TUB CG 32.

Introduction

The Jerusalem artichoke (Helianthus tuberosus L.) is a native plant of North America (Kays and Nottingham, 2008) but there are around 14 collections in Europe, of which the largest one is in Serbia, and it is the third largest in the world (Terzić et al., 2012).

The Jerusalem artichoke can be used as feedstock for ethanol production, in food industry due to its very interesting nutritional, functional, health-promoting and technological properties (Luisa Beirão-da-Costa et al., 2005; Lingyun et al., 2007), as a substitute for lipid compounds and a supplement for sugar as high-fructose syrup (Baker et al., 1993; Fleming et al., 1979; Šimonová et al., 2010), in animal feed as flour and dried mash, etc. (Saengthongpinit, 2005). A fresh Jerusalem artichoke tuber contains 80% water, 15% sugars and about 2% protein. Tubers contain inulin instead of starch and sucrose found in most other tubers. Inulin in various plant sources (Jerusalem artichoke and chicory) is of considerable importance in terms of its utilization. Content of inulin in both plants is >15% on a fresh weight basis according to De Leenheer et al. (1996) which indicates that Jerusalem artichoke is economically significant industrial crop within European cropping systems. The aim of plant breeders has been primarily to enhance tuber production and inulin content (Kays and Nottingham, 2008). Inulin, a non-digestible oligosaccharide, consists of fructose molecules (chain length from 2 to 60/70 units) linked by β(2→1) glycosidic bonds, with a terminal unit of D-glucose molecule linked to fructose by an α(1→2) bond, as in sucrose (Suzuki, 1993; Chiavaro et al., 2007). In addition to the high levels of inulin in the tubers, Jerusalem artichoke is also regarded as a good source of soluble and insoluble fiber (Terzić and Atlagić, 2009).

The inulin content of Jerusalem artichoke tubers ranges from 7 to 30% of its fresh weight (Kays and Nottingham, 2008; Saengthongpinit, 2005). Inulin content is very important because inulin has a positive effect on blood glucose attenuation, lipid homeostasis, mineral bioavailability, and it also has the ability to improve rheological characteristics, technological quality and nutritional properties of food products (Niness, 1999; Filipović et al., 2013).

The aims of this study are to:

  1. (1)

    test and adopt a reliable inulin extraction and quantification procedure and

  2. (2)

    determine quantity of inulin in selected accessions of Jerusalem artichoke grown in Serbia.

Materials and methods

The trial was performed in Rimski šančevi, on the field of the Oil Crops Department of the Institute for Field and Vegetable Crops in Novi Sad, Serbia (45°19′40″ N, 19°49′41″ E). The material consisted of 141 accessions of Jerusalem artichoke, but the quantification of the inulin content was investigated in 12 selected accessions. The selection of these accessions was based on the results of the total sugar content and certain phenotypic traits like tuber number and size, obtained in a wide characterization trial (Terzić, 2010).

Selected accessions were grown on dark chernozem soil in 2010 using the randomized complete block design (RCB). Each genotype was sown in four replications. Planting was done during the last decade of March. Accessions were grown in 1.5 by 3.5 m plots with 21 plants per plot (40,000 plants/ha). Plant spacing was 1 m between rows and 0.5 m between plants within rows. Tubers were planted in a nursery given standard locally recommended agronomy for cultivated sunflower. Plants were not irrigated. The nursery was fertilized with 300 kg ha−1 of NPK fertilizer type 15:15:15.

Several methods for inulin extraction from Jerusalem artichoke have been developed (Kays and Nottingham, 2008). The selection of an optimal extraction method is dependent on the desired end product, equipment, volume and other factors. Considering the available resources, inulin was extracted by using a modified method from Laurenzo et al. (1997), using hot deionized water. The Jerusalem artichoke tubers were first washed and the cleaned tubers were ground into small pieces and streamed at atmospheric pressure for about 10 minutes to inactivate the inulin degrading enzymes. The streamed tubers were milled using a Knifetec 1095 Mill (Foss, North America). The ground tubers (20 g) were transferred into boiling water (60 ml water) for inulin extraction, where they were kept for a period of 10–15 minutes.

After that the entire mass was filtered through a muslin cloth. The hot filtered extract was collected and stored refrigerated. The samples were filtered through a 0.2 μm membrane filter before analysis by high-performance liquid chromatography (HPLC) with light scattering detection.

The HPLC system consisted of the Agilent liquid chromatography 1200 Series (Agilent Technologies, Santa Clara, CA, USA), a binary pumped system equipped with light scattering detection. The analytical column was Rezex RCM-monosaccharide Ca+2 (300×7.8 mm) kept at a constant temperature of 50°C. The injection volume was 20 ml. Deionized water mobile phase was used in the isocratic gradient program at a flow rate of 0.6 ml min−1. The acquisition of chromatograms lasted for 17 min.

Statistical analysis

The data were processed statistically using STATISTICA 10 Software (Statsoft Inc., 2010, Tulsa, Oklahoma). The significance of the difference between the mean values was estimated by one-way analysis of variance (ANOVA), and these were compared by the Fisher’s Least Significant Difference (LSD) Test.

Results and discussion

It is assumed that there is a linear relationship between HPLC output and sample concentration. Under these conditions, the concentration of inulin in the injected sample, CSample expressed in mg/ml, and the peak area, ASample are proportional:

CSample=KB×ASample

The response factor KB is defined from the concentration expressed in mg/ml and peak area of the standard solution using the average of values.

KB=CStandard/AStandard

The concentration of inulin in Jerusalem artichoke sample expressed in mg/ml of Jerusalem artichoke is defined as:

Inulin%Jerusalemartichoke=CSample×100/CJerusalemartichoke

where CJerusalemartichoke is the effective concentration of Jerusalem artichoke expressed in mg/ml of analyzed sample solution.

Table 1:

Inulin content in selected accessions of Jerusalem artichoke tubers obtained by HPLC

AccessionInulin concentration (%)
TUB CG 3213.46±0.19a
TUB CG 5812.33±0.08b
CG 2610.77±0.37de
CG 205111.11±0.12d
TUB CG 812.30±0.05b
TUB BP 510.40±0.25e
TUB CG 49.95±0.16e
TUB BP 238.16±0.21g
TUB BP 129.64±0.64f
TUB CG 6111.75±0.23c
TUB BP 109.13±0.04f
TUB BP 1111.01±0.01d

Inulin content presented a maximum value in TUB CG 32, and it was 13.46%, while the lowest concentration was detected in TUB BP 23 (8.16%) (Table 1). The differences between accessions were statistically significant. Our study is in accordance with Van Loo et al. (1995) who considered that typical inulin content is between 8 and 21% of fresh weight. Matias et al. (2011) found inulin content in Jerusalem artichoke tubers between 136.75 and 164.78 (mg/g) of fresh tubers. Our results show relatively low level of inulin in Jerusalem artichoke tubers. It could be influenced by genetic potential and different temperatures during storage (Cabezas et al., 2002), while inulin content also depends on the extracting technical conditions (Lingyun et al., 2007). Inulin content obtained in our samples is similar to inulin content in the chicory root which can contain up to 20% of storage carbohydrates, mainly inulin (Baert et al., 1992). Douglas and Poll (1986) compared 14 chicory varieties and inulin contents varied from 10.6 to 20.5%. In spite of Jerusalem artichoke and chicory, globe artichoke has lower inulin content (2–9%), but higher degree of polymerization (Kays and Nottingham, 2008).

Figure 1: Chromatograms of inulin in TUB CG 32 (a) and inulin in TUB BP 23 (b)

Figure 1:

Chromatograms of inulin in TUB CG 32 (a) and inulin in TUB BP 23 (b)

The comparison of the obtained chromatograms revealed that the distribution profile of peaks did not change significantly. On the other hand, the peak area varied greatly between the lowest found in accession TUB BP 23 and highest in accession TUB CG 32 (Figure 1).

Figure 2: Diagram of cluster analysis considering the content of inulin in tubers of Jerusalem artichoke

Figure 2:

Diagram of cluster analysis considering the content of inulin in tubers of Jerusalem artichoke

A cluster analysis was performed to classify samples on the basis of the content of inulin in tubers. All samples are grouped in high dimensional space and thus a dendrogram was formed. In this study, an average linkage was used and Euclidean distances were calculated. The dendrogram (Figure 2) shows an almost clear separation of accessions originating from Montenegro (CG) which are landraces and cultivars with breeding history (BP). In general, CG accessions have higher inulin content but lower tuber yield, while BP have lower inulin content and higher tuber yield. An optimal accession for a future breeding program should comprise both high inulin and tuber yield besides positive phenotype traits, like smaller number of large tubers produced close to the plant.

Conclusion

The analyzed accessions showed relatively low inulin content that does not necessarily mean that an accession is inferior, because it may have higher total inulin yield per hectare or is more suitable for production. Interaction between yield components and genotype influenced by environment should be investigated if commercial production is expected. The quantification methods applied in this research should be improved. It is necessary to optimize the extracting conditions and in that way improve inulin extraction yields. Further research should also take into account suitable storage temperature and storage duration.

Acknowledgment

This work was supported by the national research project III46005 “New products based on cereals and pseudo cereals from organic production”, and research project TR31025 “Development of new varieties and production technology improvement of oil crops for different purposes”, financed by the Ministry of Education and Science of the Republic of Serbia.

References

Baert,J.R.A., Van Bockstaele,E.J., 1992. Cultivation and breeding of root chicory for inulin production. Industrial Crops and Productsl: 229234. Search in Google Scholar

Baker,L., Henning,J.C., Thomassin,P.J., 1993. Jerusalem artichoke costs of production in Canada: Implications for production of fuel ethanol. In: Fuchs, A. (ed.) Inulin and Inulin Containing Crops, Studies in Plant Science, Vol. 3, Elsevier, Amsterdam, pp. 8592. Search in Google Scholar

Cabezas,M.J., Rabert,C., Bravo,S., Shene,C., 2002. Inulin and sugar contents in Helianthus tuberosus and Cichorium intybus tubers: Effect of postharvest storage temperature. JFS: Food Chemistry and Toxicology67(8): 28602865. Search in Google Scholar

Chiavaro,E., Vittadini,E., Corradini,C., 2007. Physicochemical characterization and stability of inulin gels. European Food Research and Technology225: 8594. Search in Google Scholar

De Leenheer, L., 1996. Production and use of inulin: Industrial reality with a promising future. In: van Bekkum, H., Röper, H., Voragen, A.L.J. (eds.) Carbohydrates as Organic Raw Materials III, Weinheim, Cambridge, UK, pp. 6792. Search in Google Scholar

Douglas, J., Poll, S., 1986. A preliminary assessment of chicory (Cichorium intybus) as an energy crop. New Zealand Journal of Experimental Agriculture14: 223225. Search in Google Scholar

Filipović,J., Miladinović,Z., Pezo,L., Filipović,N., Košutić,M., Brkljača,J., 2013. Identification of inulin HPX in pasta by 13C MAS NMR spectroscopy. Journal on Processing and Energy in Agriculture16(4): 169172. Search in Google Scholar

Fleming, S. E., GrootWassink,J.W.D., Murray,E.D., 1979. Preparation of high‐fructose syrup from the tubers of the Jerusalem artichoke (Helianthus tuberosus L.). Critical Reviews in Food Science and Nutrition12(1): 128. Search in Google Scholar

Kays, S.J., Nottingham, S.F., 2008. Biology and chemistry of Jerusalem artichoke (Helianthus tuberosus L.), CRC Press, Boca Raton, FL, pp. 1478. Search in Google Scholar

Laurenzo, K.S., et al. 1997. Preparation of inulin products. United States Patent, Patent Number: 5, 968, 365. Search in Google Scholar

Lingyun,W., Jianhua,W., Xiaodong, Z., Da,T., Yalin,Y., Chenggang, C., Tianhua,F.Fan,Z., 2007. Studies on the extracting technical conditions of inulin from Jerusalem artichoke tubers. Journal of Food Engineering79: 10871093. Search in Google Scholar

Luisa Beirão-da-Costa,M., Januário,M.I.N., Leitão,A.E.B., Simão,F.M.L.S., 2005. Characterisation of inulin from chicory and salsify cultivated in Portugal. In: 2nd Mercosur Congress on Chemical Engineering, pp. 221225. Search in Google Scholar

Matías,J., González,J., Royano,L., Barrena,A.R., 2011. Analysis of sugars by liquid chromatography-mass spectrometry in Jerusalem artichoke tubers for bioethanol production optimization. Biomass and Bioenergy35: 20062012. Search in Google Scholar

Niness, K.R., 1999. Inulin and oligofructose: What are they?Journal of Nutrition129: 1402S1406S. Search in Google Scholar

Saengthongpinit,W., 2005. Influence of harvest time and storage temperature on characteristics of inulin from Jerusalem artichoke and physicochemical properties of inulin-starch mixed gel. PhD Thesis, Food Science and Technology Department, Kasetsart University, Bangkok, Thailand. Search in Google Scholar

Šimonová, I., Karovičová, J., Mastihuba, V., Kohajdová, Z., 2010. HPLC determination of inulin in plant materials. Acta Chimica Slovaca3(2): 122129. Search in Google Scholar

Suzuki, M., 1993. Fructans in crop production and preservation. In: Suzuki, M., Chatterton, N.J. (eds.) Science and Technology of Fructans, Boca Raton, Florida: CRC Press, pp. 227255. Search in Google Scholar

Terzić,S., 2010. Genetic variability and population usability of а wild sunflower species Helianthus tuberosus L. PhD Thesis, Faculty of Agriculture, University of Novi Sad, Novi Sad. Search in Google Scholar

Terzić,S., Atalagić,J., 2009. Nitrogen and sugar content variability in tubers of Jerusalem artichoke (Helianthus tuberosus). Genetika41(3): 289295. Search in Google Scholar

Terzić, S., Atlagić, J., Maksimović, I., Zeremski, T., Zorić, M., Miklič, V., Balalić, I., 2012. Genetic variability for mineral concentration in tubers and leaves of Jerusalem artichoke. Scientia Horticulturae136: 135144. Search in Google Scholar

Van Loo,J., Coussement,P., De Leenheer,L., Hoebregs, H., Smits,G., 1995. On the presence of inulin and oligofructose as natural ingredients in the Western diet. Critical Reviews in Food Science and Nutrition35: 525552. Search in Google Scholar

Received: 2014-2-5
Accepted: 2014-5-20
Published Online: 2014-6-28
Published in Print: 2014-7-1

©2014 by Walter de Gruyter Berlin / Boston

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