Procedia Food Science 1 (2011) 893 – 899

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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.2011.09.135

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Procedia – Food Science 00 (2011) 000–000

ProcediaFood Science

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11th International Congress on Engineering & Food (ICEF11)

Adsorption of polyphenols from ginger rhizomes on an anion exchange resin Amberlite IR-400 – Study on effect of pH and

temperature

Chandreyee Datta, Asmita Dutta, Debjani Dutta, Surabhi Chaudhuri*a

Department of Biotechnology, National Institute of Technology, Durgapur 713209, India

Abstract

Adsorption of ginger (Zingiber officinale) polyphenol on an anion exchange resin, Amberlite IR-400 was studied for purification of polyphenols from the crude extract. The work was carried out to understand how the processing parameters can be manipulated to optimize the purification of ginger phenolics for its further use in nutraceuticals and functional foods. In this work the effect of pH and temperature on ginger polyphenol adsorption on anion exchange resin was studied. Adsorption was studied by mixing 10 gm (dry weight basis) of pretreated resin (Amberlite IR-400) with dilute hydro alcoholic (50:50) ginger extract at temperature varying from 25-40ºC and pH values ranging from 4.0 to 6.5. The total polyphenol content was determined by Folin-Ciocalteau method. Within the pH range studied, pH 4.5 and 5.5 gave the best results reaching 91% and 92% adsorption of total polyphenol. At 25°C highest adsorption was obtained (92%). With the increase of temperature, adsorption percentage showed a gradual decrease, with only 70% adsorption of total polyphenols at 40°C. Statistical analysis of pH and temperature variation was done to obtain their influence on the efficiency of adsorption. For pH, we found that the calculated value of F at 5% level of significance at degrees of freedom (2, 15) [Fcalculated=13.738] is much greater than the given value of F=3.68. In case of temperature as a variable, the calculated value of F at 5% level of significance at degrees of freedom (2,9) [FCalculated=28.66] is also much greater than the given value of F=4.26. The Null hypothesis at 5% level was rejected and it was concluded that the difference in adsorption percentage of total polyphenols under different pH and temperature range is significant. This result will help in designing experiments for optimization of physical parameters for purification of polyphenols from ginger.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of ICEF11 Executive Committee Member

Keywords: Adsorption; Polyphenol; Ginger; Amberlite IR-400; Purification

* Corresponding author. Tel.: +913432754031; fax: +913432547375. E-mail address: surabhi_c@yahoo.com.

© 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.

894 Chandreyee Datta et al. / Procedia Food Science 1 (2011) 893 – 8992 Author name / Procedia – Food Science 00 (2011) 000–000

1. Introduction

Many plant secondary metabolites possess antimicrobial, antiviral, antioxidative and anti-inflammatory properties. Polyphenolic antioxidants are helpful in protecting the plant from oxidative damage resulting from biotic or abiotic stress factor. Apart from these, antibiotic, anti-diarrheal, anti-inflammatory, antithrombotic, hypo-cholesteloromic effect and anti-carcinogenic property have been ascribed to polyphenols. Neuroprotective and anti tumorogenic properties have also been reported [2, 6]. It has been found that phenolics are capable of exerting more powerful antioxidative effect than vitamin E in vitro and prevent lipid peroxidation by chain breaking and peroxyl-radical scavenging. In addition, they can also directly scavenge reactive oxygen species (ROS), such as hydroxyl, superoxide and peroxynitrile radicals [16]. Antioxidant rich diet helps reducing the risk of oxidative stress related diseases like cancer, cardiovascular and neurodegenerative diseases. As a result, there is an increasing demand in food industry for these plant metabolites as additives in functional food or nutraceuticals.

Ginger (Zingiber officinale) has been used as a spice for over 2000 years. Its roots contain polyphenolic compounds (6-gingerol and its derivatives) which have high antioxidant activity [11, 15]. Further purification of ginger polyphenols is required in order to obtain desired components from crude extracts. Since adsorption is a low cost separation technique, its use for selective recovery of desired metabolites from crude extract needs to be explored.

Adsorption technology using non polar copolymer or slightly hydrophilic copolymer is widely used in industrial process due to high adsorption capacity, easy recovery of adsorbed molecules, relatively low cost, easy regeneration etc. Moreover, recovery of polyphenols using polymeric resins is approved for food processing by Food and Drug Administration and the Council of Europe [12]. The adsorption behavior of flavonoids and phenolic acids on Amberlite XAD 16 HP was studied using D-optimal design [2]. Adsorptive recovery of polyphenol from Inga edulis leaves with Amberlite XAD 7, XAD 16, EXA 90 and EXA 118 has been reported [13].

In our study, adsorption of ginger polyphenol on an anion exchange resin, Amberlite IR-400 was used for purification of polyphenols from the crude extract. The work was carried out to understand how the process parameters can be manipulated to optimize the purification of ginger phenolics for further use in nutraceuticals and functional foods.

2. Materials and Methods

2.1. Materials

Fresh ginger rhizomes (Zingiber officinale) were collected from local market. Ethanol, sodium carbonate, gallic acid and Folin-Ciocalteu phenol reagent were of analytical grade commercially available in India and were used for preparation of ginger extract and determination of total polyphenol content. Amberlite IR 400 resin was purchased from Sigma–Aldrich (India). Sodium Hydroxide pellets, Hydrochloric acid, Citric acid, Tri-sodium citrate, Sodium di-hydrogen phosphate, di-sodium hydrogen phosphate were purchased from Merck (India) and were used for pretreatment of resins and preparation of buffer solution.

2.2. Preparation of Ginger powder

Fresh, washed ginger rhizomes were cut into small pieces with a cutter, the small pieces were ground in a grinder to form a fine paste. The paste was then lyophilized for 3 hours at -50°C.

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2.3. Preparation of ginger extract

1 gm of finely ground lyophilized sample was mixed with 40 ml of dilute aqueous-ethanolic solution (50:50). The solution was subjected to microwave treatment at 350 W. At first, power was on for 45 sec. Then power was switched off for 10 sec for cooling of the mixture. After that again power was switched on for 3 sec for heating. The above process was repeated for pre-set extraction time of 9 minutes [9]. After the extraction procedure, the extracts were filtered by Whatman filter paper (No 4) and the clear extracts were used for the experiment.

2.3.1. Pretreatment of adsorbent

10 gm of anion exchange resin Amberlite IR 400 was weighed and taken in a 250 ml conical flask. The adsorbent was washed with distilled water, then with 15 times w/v 0.5 (N) HCl and 0.5 (N) NaOH, and finally again with distilled water till neutral pH was obtained.

2.3.2. Batch adsorption studies

10 g of pretreated resin suspended in buffer was kept in a 250 ml of conical flask. 50 ml of ginger extract (in 50% aqueous-ethanolic solution) with known polyphenol concentration was added to each flask. The flasks were kept in a shaking incubator maintained at 120 rpm and 25°C until adsorption equilibrium was reached. The concentration of total polyphenol in liquid phase was analyzed by Folin-Ciocalteu method [3]. The temperature range was varied from 25-40°C, and pH of the buffer solution was varied from 4-6.5. The buffer pH of 4-5.5 were obtained using citrate buffer (an equimolar (0.1 M) mixture of citric acid and tri-sodium citrate). For pH 6-6.5, phosphate buffer (an equimolar (0.2 M) mixture of sodium di-hydrogen phosphate and di-sodium hydrogen phosphate) were used. The adsorptive capacity of the resin is represented by the following expression [7]:

(1)

Q= adsorptive capacity in mg/L, C1 is the concentration of the solution before adsorption in mg/ml, C0

is the concentration of the solution after adsorption in mg/ml, Vs is the volume of the solution in ml, Vr is the volume of the resin.

Percentage of adsorption (%) was calculated from the following expression [10]:

(2)

where qi is the initial polyphenol concentration (mg GAE/gm dry wt), qt is the polyphenol concentration after time t (min).

3. Results and Discussion

3.1. Effect of pH on the adsorptive capacity

The pH value of the aqueous solution is an important controlling parameter in any adsorption process. The pH value can affect the process by affecting the surface charge of adsorbent, the degree of ionization and speciation of adsorbate during adsorption. Thus, the effect of pH in the solution on the adsorption percentage of polyphenol on amberlite IR 400 resin was studied at a pH range of 4.0-6.5. The experiment

896 Chandreyee Datta et al. / Procedia Food Science 1 (2011) 893 – 8994 Author name / Procedia – Food Science 00 (2011) 000–000

was performed with an initial polyphenol concentration of 3.99 mg/ml, at 25°C with a contact time of 180 minutes.

It was observed that, about half the phenolics were absorbed by the resin during the first hour of adsorption. It was also observed that, pH of the solution has a significant effect on biosorption process. At pH 4, with 10 g of resin after 180 min of contact, adsorption of total polyphenols was only 79.7%. It gradually increased to 91.66% at pH 4.5 and 92.90% at pH 5.5. At pH 6 and 6.5 comparatively lower percentage of adsorption was observed (70.32% and 66.49% respectively). So, the adsorption capacity was low at moderately acidic medium (pH 4.0) and gradually increased with increasing pH values up to pH 5.5 and again started decreasing at pH 6.0 [Fig. 1, 2].

This phenomenon can be explained on the basis of decrease in competition between the charged ions for the same functional group of the resin. A change of the H3O

+ concentration in the solution results in the change in the ratio of protonated/unprotonated polyphenolic compounds. Protonation of these polyphenolic compounds significantly changes their charges as well as the affinity to negatively charged adsorption resin Amberlite IR 400 [6].

It may be mentioned here that the use of same resin for adsorption of polyphenolic extracts from other plant sources may yield different results. This is due to the fact that phenolic profile changes among different species and phenolics vary in their molecular size and form which influences their solubility and adsorption [1].

Fig. 1. Kinetic curve of adsorptive capacity of ginger polyphenol on amberlite IR-400 resin in the pH range of 4-6.5

Fig. 2. Effect of pH on adsorption percentage (%) of ginger polyphenol on amberlite IR-400

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Statistical analysis of variables was done to obtain their influence on the efficiency of adsorption. The calculated value of F at 5% level of significance at degrees of freedom (2, 15) [Fcalculated=13.738] was much greater than the given value of Fcritical=3.68. Hence, the Null hypothesis at 5% level was rejected and it was concluded that the difference in adsorption percentage of total polyphenol at different pH range is significant.

3.2. Effect of Temperature

Temperature is also one of the major factors affecting the biosorption process. In this study, 50 ml of polyphenol solution with initial polyphenol concentration of 3.99 mg/ml was treated with the 10 g of resin for 180 minutes at temperature ranging from 25°C to 40°C.

It was found that there is a gradual decrease on the total percentage of polyphenol adsorption with increasing temperature. At 25°C, where the adsorption was 92.90%, which gradually decreased to 81.65% at 30°C, 76.71% at 35°C and 67.04% at 40°C [Fig. 3, 4]. It can be mentioned here that the same experiment at 20°C did not show any improvement in the adsorptive capacity of the resins. For better economic feasibility, we performed the experiment in the temperature range of 25-40°C.

The gradual decreases in total polyphenol adsorption percentage indicate the exothermic nature of the adsorption process. To avoid compound loss, plant extracts prepared at elevated temperature should be cooled before applying to adsorption columns [6].

Fig. 3. Kinetic curve on adsorptive capacity of ginger polyphenol on amberlite IR-400 resin in the temperature range of 25-40°C

Fig. 4. Effect of temperature on adsorption percentage (%) of ginger polyphenol on amberlite IR-400

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In case of temperature as a variable, the calculated value of F at 5% level of significance at degrees of freedom (2,9) [FCalculated=28.66] was also much greater than the given value of Fcritical=4.26. Hence, the Null hypothesis at 5% level was rejected and it was concluded that the difference in adsorption percentage of total polyphenol at different temperature range is significant.

4. Conclusion

The above work was carried out to get a better understanding on how the processing parameters can be manipulated for optimization of adsorption based purification of ginger phenolics. The present study of biosorption of ginger polyphenol on an ion exchange resin shows that the adsorption process is dependent on the temperature and pH of the solution. The adsorption capacity was low at slightly acidic medium (pH 4.0) and gradually increased with increasing pH values up to pH 5.5. On the other hand, adsorption percentage of total polyphenol decreases with increasing temperature. Adsorption capacity was highest at 25°C and gradually decreased with increase in temperature indicating the exothermic nature of adsorption. It was found that at pH 5.5 and 25°C temperature, the adsorption of total polyphenol by Amberlite IR-400 was maximum (92.90%). The statistical analysis also showed that the difference in adsorption percentage of total polyphenol with the change of temperature and pH of the solution are significant.

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Presented at ICEF11 (May 22-26, 2011- Athens, Greece) as paper NFP211.