Isolation, identification and dyeing studies of betanin on modified acrylic fabrics

Industrial Crops and Products 37 (2012) 342–346

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Isolation, identification and dyeing studies of betanin on modified acrylic fabrics A. Guesmi a,∗ , N. Ladhari a , N. Ben Hamadi b , F. Sakli a a b

Textile Research Unit, Higher Institute of Technological Studies of Ksar Hellal, Tunisia Laboratory of Synthesis Heterocyclic and Natural Substances, Monastir, Tunisia

a r t i c l e

i n f o

Article history: Received 26 October 2011 Received in revised form 18 December 2011 Accepted 25 December 2011 Available online 20 January 2012 Keywords: Opuntia ficus-indica Betanin Natural dye Modified acrylic Mordant Fastness

a b s t r a c t Mature red fruits of Opuntia ficus-indica contain two soluble pigment, betanin and indicaxanthin. The optimal conditions for dye extraction were to mix 50 g of juice from cactus pears with 100 mL of acidified water as solvent for dye extraction. Two main dyes were purified from the pigment extract by chromatography and identified by UV–vis, HPLC and LC–MS techniques as indicaxanthin (15 mg per 100 g) and betanin (280 mg per 100 g). The effect of dye bath pH, salt concentration, dyeing time and temperature was studied. The optimal conditions for dyeing modified acrylic fabrics with betanin dye were carried out at 50 ◦ C for 45 min at pH 5. Un-mordanted samples have good properties of water and washing fastness. Mordant CoSO4 was found to give good light fastness (rating 5). © 2011 Elsevier B.V. All rights reserved.

1. Introduction

2. Experimental

Opuntia ficus-indica belongs to the family Cactaceae, and is originating from Mexico. It is known for rapid growth, good adaptation to poor soils and low requirement for water (Mohamed-Yasseen et al., 1995). Its fruit is a berry, varying in colour, it has been developed green and change colour with its maturity state to orange-yellow and then to reddish purple. Fruit has been used to treat diabetes, hypertension, asthma, oedema and indigestion (Hegwood, 1990). Also, it was also used as a natural food colourant (Moßhammer et al., 2005). Mature red fruits of O. ficus-indica were selected as the topic of the present study because of their higher growth in Tunisia. Betanin is the most prevalent betalain in red fruits, which typically contain large quantities of it. The use of betanin in the food industry seems to have been known (Diego et al., 2008) but it’s not well known in the field of textile (Henry, 1996). The objective of this study was to investigate the dyeing of modified acrylic fabric using betanin as a natural dye. The dyeing conditions such as the concentration of the dye, the dye bath pH, the salt concentration, the dyeing temperature, the dyeing time, and the effect of the mordants and the overall fastness properties were investigated.

2.1. Materials

∗ Corresponding author. Tel.: +216 73 450 907; fax: +216 73 475 163. E-mail address: [email protected] (A. Guesmi). 0926-6690/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2011.12.034

2.1.1. Textile materials Plain 1/1 woven acrylic fiber was used (43 × 38 threads/inch, metric count 16, weft and warp and 562 den). The fabric was soaped with 2 g/L non-ionic detergent at 60 ◦ C for 30 min, thoroughly rinsed and air dried. 2.1.2. Plant materiel Reddish purple fruits of O. ficus-indica were used in this investigation. Mature fruit samples were harvested on August 2010 and taken immediately to the laboratory where they were manually peeled and subjected to the dye extraction. 2.1.3. Chemicals used The chemicals used in this study included hydroxylamine hydrochloride, ammonium acetate, alum (KAl(SO4 )2 ·12H2 O, MW : 342.15, Aldrich), Cobalt sulfate heptahydrate (CoSO4 ·7H2 O, MW : 281.1, Aldrich), manganese sulfate monohydrate (MnSO4 ·H2 O, MW : 169.02, Aldrich), zinc sulfate heptahydrate (ZnSO4 ·7H2 O, MW : 287.54, Aldrich), and iron sulfate heptahydrate (FeSO4 ·7H2 O, MW : 278.03, Aldrich). Thin layer chromatography was performed on silica gel 254 plates (Merck) with UV (254 nm) visualisation whereas chromatographic separations were conducted on C18 Sep-Pak cartridge column.

A. Guesmi et al. / Industrial Crops and Products 37 (2012) 342–346

2.2. Methods 2.2.1. Extraction of colourants 50 g of juice from cactus pears was mix with 100 mL of acidified water [water/HCl, v/v ratio 99:1] as solvent for dye extraction. Indeed, slight acidification of the extraction medium enhances betacyanin stability (Schliemann et al., 1999; Strack et al., 2003). To enhance betalain extraction efficiency, extraction was performed by ultrasound (80 W). The ultrasound bath temperature was maintained at around 45 ◦ C in order to prevent potential heat damage to the plant material (Rosario et al., 2003). The solution was separated from the plant tissue on a Büchner funnel with a filter paper. To achieve complete discolouration of the plant material, the filter residue was rinsed with the extraction solution. 2.2.2. Photometric quantification of betalains All determinations were performed using a Philips model PU UV/visible spectrophotometer. Measurements were performed in triplicate, and the betalain content (BC) was calculated according to (Stintzing et al., 2003) with a slight modification: BC [mg/L] = [(A × DF × MW × 1000/ε × L)] where A is the absorption value at the absorption maximum, DF is the dilution factor and L is the path-length (1 cm) of the cuvette. The molecular weight (MW ) and molar extinction coefficient (ε) of betanin {MW = 550 g/mol; ε = 60,000 L/(mol cm) in H2 O} were applied in order to quantify the betacyanins. Quantitative equivalents of indicaxanthin were determined by applying the mean molar extinction coefficient {MW = 308 g/mol; ε = 48,000 L/(mol cm) in H2 O} (Kugler et al., 2004). 2.2.3. Thermal stability of dyes Thermal stability studies were performed at pH values of 3–7. Thermal stability was assayed at 50 and 90 ◦ C. Samples were withdrawn at different time intervals and spectrophotometrically analysed. Pigment content and colour retention were determined in triplicate for each sample. The thermal stability was expressed in terms of half-life time (t1/2 ) calculated assuming first-order deactivation kinetics vs temperature exposition time. 2.2.4. HPLC analysis The HPLC system (Merck) was equipped with an L-7200 autosampler, a D-7000 interface module, an L-7100 pump, an L7350 column oven with Peltier cooling module, and an L-7450A diode array detector. Reverse phase chromatography was performed with a Kromasil C8 5 ␮m column (150 mm × 4.6 mm). HPLC conditions were as follows: Solvent A was H2 O with 0.05% TFA, and solvent B was composed of methanol with 0.05% TFA. A linear gradient was performed over 21 min from 5 to 35% B. The flow rate was 1 mL/min, operated at 25 ◦ C. The injection volume was 20 ␮L. Elutions were monitored at 475 (indicaxanthin) and 538 nm (betanin). 2.2.5. Mass spectrometry (MS) Positive ion electrospray mass spectra were recorded on ThermoFinnigan LCQ Advantage (electrospray voltage: 4.5 kV; capillary: 200 ◦ C; sheath gas: N2 ). Helium was used to improve trapping efficiency and as the collision gas for CID experiments. 2.2.6. Desalting and separation of betalains Filtrate was evaporated in vacuo at 40 ◦ C. The concentrate was applied to a C18 Sep-Pak cartridge column. The C18 cartridge was activated with 3 volumes of 100% methanol and then rinsed with 3 volumes of acidified water (pH 3). For fractionation, the indicaxanthin part was eluted with 100% ethanol while the betanin

343

part remained adsorbed until eluted with acidified ethanol [95:5, ethanol/acidified water (pH 2), v/v] (Guesmi et al., in press). 2.2.7. Pre-treatment and dyeing 2.2.7.1. Pre-treatment. Following a previously published method (El-Shishtawy and Ahmed, 2005), a known weight of acrylic fibre was pretreated with hydroxylamine hydrochloride (10 g/L) using aqueous solutions of ammonium acetate (20 g/L) at a liquor-togoods ratio of 50:1 at 85 ◦ C for 1 h. The pretreated samples were thoroughly rinsed with water and air dried. 2.2.7.2. Dyeing procedure. In a dye bath containing different amounts of sodium chloride (0–15 g/L) and a dye concentration of 30 mg/L with liquor ratio 40:1, modified acrylic fabric was dyed using conventional heating (CH) at different pH values (1–7) for different durations (30–120 min) and at different temperatures (40–90 ◦ C). The dyed samples were rinsed with cold water and finally dried at ambient temperature. The pH values were recorded with Hanna pH meter, the dye bath was acidic (pH 4.5). To work at pH values superiors at 4.5, the pH values were adjusted with dilute solutions of sodium carbonate and to work at pH values inferiors at 4.5, the pH values were adjusted with dilute solutions of hydrochloric acid. In case of mordanting, pre-mordanting was chosen as the most suitable process. Modified acrylic fabrics were pre-mordanted at 40 ◦ C for 60 min using various aqueous mordant solutions (0.01 M) with liquor ratio 1:100. Then the samples were removed, squeezed, and air dried (Young and Han, 2004). 2.2.8. Colour strength and colour depth measurements The colour yield of samples was evaluated by light reflectance measurements using SF 300 spectrophotometer. Relative colour strengths (K/S values) were determined using the Kubelka–Munk equation (Judd and Wysezcki, 1975): 1 − R2 K = S 2R 2.2.9. Colour fastness test The dyed samples were tested for fastness properties according to standard methods, the specific tests were for colour fastness to washing ISO 105-C02:1989, colour fastness to rubbing ISO 105X12:1987, colour fastness to water ISO 105-E01:1989 and colour fastness to light ISO 105-B02:1988 (carbon arc). 3. Results and discussion 3.1. Extraction and spectroscopic analysis of dyes Fig. 1 shows the visible absorption spectra of the aqueous extract of reddish purple fruits of O. ficus-indica. The spectrum shows two peaks, one at 475 nm corresponding to indicaxanthin and the other at 538 nm corresponding to betanin (José et al., 2001). The presence of a slight peak at 475 nm would indicate that in these fruits indicaxanthin is to be found in a very lower level than betanin which is present in a much higher concentration. The concentration of pigments was estimated about 300 mg of betanin per 100 g of fresh pulp, and about 20 mg of indicaxanthin per 100 g. 3.2. Effect of pH on the thermal stability of reddish purple fruits of O. ficus-indica extracts To ascertain the effect of pH on the colourant capacity of O. ficusindica, aqueous extracts at different pH values (3–7) were obtained. The colourant capacity, expressed as a percentage of the maximum absorbance at 538 nm, is shown in Table 1. The maximum

A. Guesmi et al. / Industrial Crops and Products 37 (2012) 342–346

0,7

30

0,6

25

0,5

20

0,4

K/S

Absorbance

344

0,3

15 10

0,2

5

0,1 0 400

0 450

500

550

600

0

2

4

6

8

pH

Wavelength (nm) Fig. 1. Visible light absorption spectra of reddish purple fruits of Opuntia ficus-indica.

Fig. 4. Effect of dye bath pH on the colour strength of dyed modified acrylic fabrics. Dyeing conditions: Cdye 30 mg/L, 0 g/L salt, 45 min, LR 40:1, and 50 ◦ C.

Table 1 Effect of pH on the colorant capacity at 538 nm of reddish purple fruits of Opuntia ficus-indica extracts.

Von Elbe, 1985, 1987). The half-life (t1/2 ) at pH 5 was 30 min at 90 ◦ C and 14 h at 50 ◦ C.

pH

3

4

5

6

7

Colorant capacity (%)

95.7

98.1

100

98.3

96.3

14

0,8

12 10

0,6

8 0,4

6 4

0,2

2 0

half time (t1/2) at 90°C

half time (t1/2) at 50°C

50°C

1

16

90°C

6

4

As described in the previous part of this work (Guesmi et al., in press), indicaxanthin and betanin do not have the same properties of thermal stability. Therefore, to meet the requirement of reproducibility of dyeing, we resorted to a chromatographic separation. The average amount obtained of betanin after column chromatography was about 280 mg per 100 g of juice and was about 15 mg of indicaxanthin per 100 g of juice. The purified betanin was characterised by analytical methods: UV–vis (max = 538 nm), HPLC (tR = 17.5) and MS ([M+H]+ ion was m/z 551 {1 0 0}) (Fig. 3). 3.4. Dyeing

0 2

3.3. Separation and identification

8

pH Fig. 2. Influence of pH on the thermal stability of betanin of reddish purple fruits of Opuntia ficus-indica.

colour was obtained at pH 5, with a slight decrease being observed at higher and lower values. The thermal stability at different pH values (3–7) was also studied at 50 and 90 ◦ C (Fig. 2). As expected, the extracts were more stable at 50 rather than at 90 ◦ C, and in both cases, the highest stability was observed between pH 4 and pH 5 (Sapers and Hornstein, 1979; Saguy, 1979). The thermal degradation of betanin followed a first-order reaction kinetic and was dependent on pH (Huang and

3.4.1. Effect of dye bath pH Fig. 4 clearly shows that the extent of adsorption of betanin onto modified acrylic fabric increased with increasing application pH over the pH range 1–5. Between pH 4 and 5 a plateau value of K/S was observed and above pH 5 the colour strength decreases with increasing the pH value with a pronounced manner. The explanation is not obvious, but rather a correlation between dye structures, the fibre used and dye stability. Normally, decreasing the pH value would increase the protonation of the amino groups of modified acrylic fibres, which is beneficial to form ion-ion forces with ionised carboxyl groups in betanin. Nevertheless, as shown in Fig. 5, in aqueous solution betanin’s charge depends on the pH value and in strongly acidic environment, the betanin molecule may exist in cationised or on monoanion form

Fig. 3. Mass spectrum of betanin.

A. Guesmi et al. / Industrial Crops and Products 37 (2012) 342–346 Glc O

OH

O

25

N

O

20

OH

N

K/S

HO

30

Glc

O

345

O

15 10 5

HO

OH

N O

H

HO

O

O

H

pH < 2

0

OH

N

5

10

15

Concentration (g/L)

pH = 2

Fig. 6. Effect of salt addition to the dye bath on the colour strength of dyed modified acrylic fabrics. Dyeing conditions: pH 5, Cdye 30 mg/L, 45 min, LR 40:1, and 50 ◦ C. Glc

Glc

O

O

O

0

O

O

OH

30 25

OH

20

N

N

K/S

O

O

15 10 5

HO

O

N O

H

O

2 < pH < 3.5

O

O

N O

H

0 25

35

45

O

3.5 < pH < 7

3.4.2. Effect of salts addition Fig. 6 shows the effect of salt concentration on the colour strength obtained for the dyed fabrics. It is clearly indicated that as the salt concentration increases the colour strength decreases and that dyeing without salt addition is the best condition. 3.4.3. Effect of dyeing temperature The effect of dyeing temperature on the depth of shade (K/S) of dyed modified acrylic fabric is shown in Fig. 7. It was found that the K/S values increased with the dyeing temperature up to 50 ◦ C and then it decreased slowly. As shown in Section 3.2, the result is consistent with the decrease in dye molecule stability at higher temperatures. 3.4.4. Effect of dyeing time As shown in Fig. 8, the colour strength obtained increased as the time increased up to 30, a plateau is attained after 30 up to 45 min and then started to decline slightly with prolongation of the time.

65

75

Fig. 7. Effect of dyeing temperature on the colour strength of dyed modified acrylic fabrics. Dyeing conditions: pH 5, Cdye 30 mg/L, 0 g/L salt, 45 min.

Fig. 5. Charge alteration of betanin in aqueous solution resulting from different pH values.

30 25 20

K/S

(Frank et al., 2005), which explains the low depth of dyeing at pH < 4. Also, the result can be attributed to the losses of betanin stability at low pH. The maximum colour strength was obtained at pH 5, with a slight decrease being observed at pH 4, this result is due to the highest thermal stability of betanin and to the increase of the carboxyl groups in this range. At pH > 5, the ionic interaction between the carboxylate anion of the dye and modified acrylic fibres decreases due to decreasing number of protonated terminal amino groups of fabric and thus lowering its dyeability.

55

Temperature

15 10 5 0

10

30

50

70

90

Time (min) Fig. 8. Effect of dyeing time on the colour strength of dyed modified acrylic fabrics. Dyeing conditions: pH 5, Cdye 30 mg/L, 0 g/L salt, 50 ◦ C.

The decline in the dyeability may be attributed to the desorption of the dye molecules as a consequence of long dyeing time. 3.4.5. Optimisation of mordants with K/S and colour hue changes The effect of mordanting methods on dyeing of modified acrylic fabric with different mordants is shown in Table 2. It was observed that the K/S value increased in the order of dyeing using FeSO4 < KAl(SO4 )2 < MnSO4 < ZnSO4 < none < CoSO4 . The fluctuation of colourimetric data shows that the apparent colour change with varying the kind of mordant, it was found that the colour of premordanted fabrics using CoSO4 was deeper than the colour of un-mordanted fabrics, nevertheless, the apparent colour of premordanted fabrics using FeSO4 and KAl(SO4 )2 were shallowest. Indeed, some metal cations, such as iron, copper, tin and aluminium were reported to accelerate betanin degradation (Pasch and Von

346

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Table 2 The effect of mordant type on the colourimetric data of modified acrylic fabrics dyed with betanin. Pre-mordanting

a*

b*

L*

C*

H

K/S

None Alum Cobalt sulfate Manganese sulfate Zinc sulfate Iron sulfate

35.86 35.99 35.82 40.57 37.5 33.5

−12.41 −16.97 −13.66 −16.88 −12.88 −17.88

24.22 45.74 21.60 30.23 28.30 48.98

37.95 39.50 33.00 41.60 38.80 39.80

340.91 331.07 345.45 336.55 341.2 329.2

26.59 6.32 31.50 17.87 21.00 5.90

Table 3 The fastness of modified acrylic fabrics dyed with betanin dye. Dry rubbing fastness None 5 5 MnSO4 4 FeSO4 5 ZnSO4 KAl(SO4 )2 4 5 CoSO4

Wet rubbing fastness

Washing fastness

Water fastness

Light fastness

5 5 4 5 4 5

4–5 4 3 4–5 3 4–5

4–5 4 3 4–5 3 4–5

3 4 3 4 3 5

Elbe, 1979; Attoe and Von Elbe, 1984; Czapski, 1990; Sobkowska et al., 1991). 3.4.6. Colour fastness Fastness properties of the dyed fabrics are shown in Table 3. It was found that water, washing, and rubbing fastness of unmordanted fabrics showed considerably good. However, the light fastness of unmordanted fabrics was bad. The light fastness of premordanted fabrics was significantly found to increase from rating 3 to rating 4 using MnSO4 and FeSO4 , and from rating 3 to rating 5 using CoSO4 . However, the other mordants among mordants used in this study did not affect the light fastness of pre-mordanted fabrics. 4. Conclusion Betanin dye isolated from Reddish purple fruits of O. ficus-indica could be used for dyeing modified acrylic fabrics with good fastness properties. It was found that the K/S value of dyed fabrics increased in the order of dyeing using FeSO4 < KAl(SO4 )2 < MnSO4 < ZnSO4 < none < CoSO4 . It was found that CoSO4 was the best mordant for the improvements of colour strength (K/S) and light fastness.

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