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Development of bioactive edible film from turmeric dye solvent extraction residue
LWT - Food Science and Technology 56 (2014) 269e277
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Development of bioactive edible film from turmeric dye solvent extraction residue B.C. Maniglia, J.R. Domingos, R.L. de Paula, D.R. Tapia-Blácido* Departamento de Química, Faculdade de Filosofia, Ciências e Letras, Universidade de São Paulo, Av. Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 July 2013 Received in revised form 25 November 2013 Accepted 9 December 2013
We developed and characterized turmeric flour films using the turmeric dye solvent extraction residue. We evaluated how the heating temperature and pH affected film properties using a 22 central composite design. Multi-response analysis furnished the film formulation that offered larger resistance to break, as well as lower water solubility, WVP, and opacity. The heating temperature and pH affected the mechanical properties, solubility, moisture content, WVP, and opacity of the resulting film. High heating temperature promoted more interactions between the polymers present in the turmeric flour (starch, protein, lipid, and fiber), affording a more resistant polymeric structure with lower WVP, moisture content, and opacity. Higher pH values also favored a more mechanically resistant and dense matrix with lower water solubility and WVP. The optimized conditions were: T ¼ 86.7 C and pH ¼ 8.5. The films produced under these conditions displayed high mechanical strength (18 MPa), low solubility (36%), and low WVP (0.167 g mm h1 m2 kPa1). However, because these films contained lignocellulosic fibers, they presented low elongation at break (1.8%), which elicited a non-continuous structure. HPLC and DPPH assays showed that the turmeric dye solvent extraction residue can be a promising source to develop films with antioxidant activity. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Curcumin Turmeric Bioactive film Antioxidant Mechanical properties
1. Introduction It is possible to make edible films from biopolymers such as polysaccharides and proteins extracted from plant or animal raw material. In general, these biopolymers constitute a poor barrier to water vapor; moreover, compared with synthetic packaging, they have unsatisfactory mechanical strength and elongation. To make protein and starch films mechanically stronger, some authors have incorporated fibers of different plant origins (hemp, jute, flax, bagasse, cotton, sisal, wheat fibers, etc.) into biocomposites, to reinforce agromaterials (Montaño-Leyva et al., 2013; Satyanarayana, Arizaga, & Wypych, 2009). The results are not always favorable: the polymers may be thermodynamically incompatible, culminating in phase separation (Grinberg & Tolstoguzov, 1997). To overcome this problem, researchers have prepared biodegradable films from natural mixtures (carbohydrates, proteins, lipids, and fibers) obtained in the flour form from raw materials of plant origin such as cereals, tubers, and rhizomes (Andrade-Mahecha, Tapia-Blácido, & Menegalli, 2012; Dias, Muller,
* Corresponding author. Tel.: þ55 16 36020580; fax: þ55 16 36332660. E-mail addresses: [email protected], [email protected] (D.R. Tapia-Blácido). 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.12.011
Larotonda, & Laurindo, 2010; Gontard, Guilbert, & Cuq, 1993; TapiaBlácido, Mauri, Menegalli, Sobral, & Añón, 2007; Tapia-Blácido, Sobral, & Menegalli, 2005, 2011). A recent trend is to use industrial residue to obtain natural mixtures of biopolymers as flour, which may provide the packaging market with a competitive product. Curcuma longa L. belongs to the family Zingiberaceae, commonly known as turmeric. It consists of a rhizomatus perennial herb with primary and secondary rhizomes; and its shape varies from spherical to slightly conical, hemispherical, or cylindrical (Jyothi, Moorthy, & Vimla, 2003). This herb is bright yellow because it contains Curcumin, a diphenolic compound, that exerts antiinflammatory action and is a potential candidate to treat cystic fibrosis, Alzheimer’s, malarial diseases, and cancer (Maheshwari, Singh, Gaddipati, & Srimal, 2006; Yallapu, Jaggi, & Chauhan, 2012). Turmeric also contains the curcuminoids demethoxycurcumin and bisdemethoxycurcumin (Joshi, Jain, & Sharma, 2009). One can extract the turmeric oleoresin from dried rhizomes by Soxhlet extraction, sonication, and liquideliquid extraction using acetone, methanol, ethanol, and isopropanol as organic solvents. It is also possible to obtain this resin by supercritical fluid extraction with CO2 (Braga, Leal, Carvalho, & Meireles, 2003; Braga, Moreschi, & Meireles, 2006; Euterpio, Cavaliere, Capriotti, & Crescenzi, 2011;
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Joshi et al., 2009). The turmeric oleoresin usually contains 30e45 g/ 100 g curcuminoids and 15e20 g/100 g volatile oil. Because this extraction generates a residue that consists predominantly of starch and fibers and may present residual levels of curcuminoids with antioxidant properties (Braga et al., 2003, 2006; Kuttigounder, Rao, & Bhattacharya, 2011), we propose that this residue be used to develop a biodegradable film. The resulting turmeric film could be an active packaging material the presence of curcuminoids confers the film an antioxidant character. Therefore, this study aimed to develop turmeric films from turmeric dye solvent extraction residue using the response surface methodology and multi-response analysis, to obtain the formulation that would afford the turmeric flour film with optimal mechanical properties and low water vapor permeability, and to evaluate the antioxidant property of these films. 2. Material and methods 2.1. Materials The turmeric powder (Curcuma longa L) was furnished by the industry “Flores e Ervas” (Campinas, Brazil). The turmeric flour was obtained by milling and sieving (0.075 mm) the turmeric dye soxhlet extraction residue. The extraction followed the method proposed by Braga and Meireles (2007), using ethanol/isopropanol (1:1) (Synth - São Paulo, Brazil). Sorbitol, used as plasticizer, was purchased from SigmaeAldrich (São Paulo, Brazil). 2.2. Turmeric flour chemical analyses The turmeric flour moisture, crude protein, and ash contents were analyzed according to standard AOAC methods (AOAC, 1997). The starch amylose content was determined using the colorimetric method of Juliano (1971). The lipids content was calculated by the method of Bligh and Dyer (1959). The cellulose, hemicellulose, and lignin content were determined according to the methodology described by Gouveia, Do Nascimento, & Soto-Maior (2009). The material was submitted to hydrolysis with H2SO4 at 720 mL/L, to quantify carbohydrates, organic acid, furfural, and hydroxymethylfurfural by HPLC. The concentrations of cellulose and hemicellulose were calculated using the following conversion factors: cellulose (0.90 glucose mass, 0.95 cellobiose mass, 1.20 HMF mass, 3.09 formic acid mass); hemicellulose (0.88 xylose mass, 0.88 arabinose mass, 0.72 acetic acid mass, 1.37 furfural mass). Insoluble lignin was determined by the Klasson method, and soluble lignin was determined by measuring the absorbance at 280 nm. All the analyses were performed in triplicate. 2.3. Film preparation The turmeric flour films were prepared by casting. Initially, a 5 g/ 100 g suspension was prepared in deionized water and homogenized for 30 min in a magnetic stirrer (IKA MAGÒ C-HS7-Marconi, Piracicaba - Brazil). The pH of the solution was adjusted to 6.59, 7.0, 8.0, 9.0, or 9.41 using HCl 1 mol/L and NaOH 1 mol/L solution. Then, the suspension was heated at 78, 80, 85, 90, or 92 C for 4 h while applying homogenization cycles at 12,000 rpm for 2 min at every hour using an ultra-turrax homogenizer (Ultracleaner 1400, Unique, Indaiatuba, Brazil). The plasticizer (30 g sorbitol/100 g flour) was added, and the mixture was heated for 20 min. In a preliminary test was determined that as the optimal concentration of sorbitol for turmeric flour film production with low solubility and high mechanical resistance. Then, the solution was sonicated
for 20 min, to remove bubbles. Subsequently, the solution was poured onto acrylic plates maintaining a weight of 0.15 g m2 and dried for 7 h in an oven with forced circulation (MA Q314M, Quimis, Piracicaba-Brazil), at 35 C. Prior to characterization, all the films were preconditioned for at least 48 h in desiccators containing a saturated NaBr solution (58% RH). 2.4. Films properties The mechanical tests were performed using a texture analyzer TA TX Plus (TA Instrument, England). The tensile strength (TS) and elongation at break (E) were obtained according to the ASTM D882- 95 method (ASTM., 1995), taking an average of five determinations in each case. Sample films were cut into 2.54 cm wide strips with a length of at least 10 cm. The initial grip separation and the crosshead speed were set at 80 mm and 1.0 mm s1, respectively. Young’s modulus (YM) was calculated as the inclination of the initial linear portion of the stress versus strain curve using the software Texture Expert V.1.22 (SMS). The opacity was determined according to the Hunterlab method (1997), using a portable colorimeter MiniScan XE (Hunterlab). The solubility in water was calculated as the percentage of dry matter of the solubilized film after immersion for 24 h in water at 25 2 C (Gontard, Guilbert, & Cuq, 1992) as described by Tapia-Blácido et al. (2011). The moisture content in the films was also determined by drying the materials in an oven at 105 C until constant weight (w24 h). The water vapor permeability (WVP) test was performed using a modified E96-95 ASTM Standard method (ASTM, 1995) at 25 2 C. Film samples were sealed over the circular opening of a permeation cell containing silica gel, and the cells were then placed in desiccators containing distilled water. After the samples had reached steady-state conditions (w20 h), the cell was weighed every 1 h, for 9 h, using an analytical scale. The WVP was calculated as WVP ¼ w$x/t$ADP,where x was the average thickness of the films, A was the permeation area (0.00196 m2), DP was the difference between the partial pressure of the atmosphere over silica gel and over pure water (3.168 kPa, at 25 C), and the term w/t was calculated by linear regression using data of weight gain as a function of time. Solubility, WVP, moisture content, and opacity were analyzed in triplicate. 2.5. Scanning electron microscopy (SEM) Film samples were maintained in a desiccator with silica gel for seven days and then fractured with liquid nitrogen, to investigate the samples cross-section. The samples were placed in aluminum holders and coated with gold by sputtering (Sputter Coater, model SCD050). A Microscope Scanning Electron model ZEISS EVO-50 under an accelerating voltage of 20 kV was used to analyze samples. 2.6. Optimal turmeric flour films antioxidant activity The turmeric flour films antioxidant property was determined using two techniques: DPPH and HPLC. The curcuminoids present in the film were extracted using 2 mL of methanol for every 100 mg of the film, and the mixture was incubated for 3 h at room temperature. Next, 500 mL of the mixture supernatant (film/methanol) was added to 2 mL of the methanolic DPPH solution (0.06 mmol/L), and the resulting mixture was stirred for 30 min, at room temperature, and protected from light. The remaining DPPH was determined by absorbance at 517 nm using an HP Hewlett Packard 8453 spectrophotometer coupled to a microcomputer HP Vectra XA 51166. The control consisted of 500 mL of DPPH solution
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Table 1 Mechanical properties, solubility in water, moisture content, water vapor permeability, and opacity of turmeric flour film plasticized with sorbitol according to the full-factorial design 22 central composite designs. >). Test
Ta (X1b)
pH (X2b)
TSc (MPa)
1 2 3 4 5 6 7 8 9 10 11
80 80 90 90 78 92 85 85 85 85 85
7 (1) 9 (þ1) 7 (1) 9 (þ1) 8 (0) 8 (0) 6.59 (1.414) 9.41 (þ1.414) 8 (0) 8 (0) 8 (0)
5.7 15.5 11.5 19.5 6.3 13.7 2.8 13.4 17.4 18.0 16.9
a b c
(1) (1) (þ1) (þ1) (1.414) (þ1.414) (0) (0) (0) (0) (0)
1.4 0.5 2.9 2.8 2.4 2.6 0.3 3.1 4.8 3.7 1.4
E (%) 0.7 0.8 0.7 1.2 1.2 2.0 0.6 0.6 1.7 1.6 1.6
YM (MPa) 0.3 0.1 0.2 0.1 0.1 0.4 0.1 0.2 0.2 0.2 0.2
527.1 1811.6 1362.4 1857.1 601.5 973.0 462.1 2053.0 1367.0 1511.0 1491.1
15.2 39.6 15.6 99.8 92 94.8 27.2 284 121 133 201
WVP (g mm h1 m2 kPa1)
S (%) 39.3 42.4 45.5 38.9 44.7 45.7 44.7 37.8 36.9 35.5 37.7
1.9 9.4 0.5 1.9 2.8 0.8 5.4 5.4 0.2 0.1 0.2
0.178 0.400 0.186 0.220 0.594 0.304 0.100 0.190 0.214 0.216 0.216
0.004 0.07 0.20 0.03 0.02 0.06 0.04 0.10 0.11 0.05 0.007
MC (g/100 g) 9.1 8.9 8.9 8.7 11.0 10.8 8.5 7.6 9.0 9.0 9.0
0.4 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.1 0.1
OP (%) 20.9 15.0 11.4 14.4 21.3 6.9 22.5 15.3 11.8 11.8 12.1
0.1 0.2 0.5 3.0 1.1 0.2 0.1 0.4 1.1 0.2 0.1
T ( C). Independent variables values (the values between brackets are the coded variables). Tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility (S), water vapor permeability (WVP), moisture content (M), opacity (OP).
(0.06 mmol/L). The antioxidant activity of the films was calculated according to Equation (1) and expressed as percentage of antioxidant activity (%AA) (Marins, Cerqueira, & Vicente, 2012).
Asample AA% ¼ 100 1 Acontrol
(1)
where: AA ¼ antioxidant activity; Asample ¼ absorbance of the solution containing the sample; Acontrol ¼ absorbance of the DPPH solution without addition of the film. To analyze the antioxidant activity by HPLC (Model: CTO10ASVP, Shimadzu), 20 mL of the supernatant (film/methanol) was used in the following conditions: C-18 column (4.6 mm 250 mm, 5 mm), oven temperature ¼ 40 C, detector ¼ arrangement LED (420 nm), loop ¼ 20 L, flow ¼ 1.0 mL.min1. The mobile phase consisted of 450 mL/L acetonitrile in 550 mL/L aqueous solution of 10 mL/L acetic acid. The gradient program was as follows: 0e 12 min, 45 mL/L acetonitrile; 12e32 min, 450e1000 mL/L acetonitrile; 32e40 min, 1000 mL/L acetonitrile. The standard curcumin, demethoxycurcumin, and bisdemethoxycurcumin were obtained from Fluka Analytical, Switzerland (98%). All the other chemicals and reagents were purchased from E-Merck and were analytical grade. The curcuminoids standard methanol solutions were freshly prepared, to construct the calibration curve. To obtain this curve, five solutions of each type of curcuminoid were prepared at different concentrations (curcumin: from 0.002 to 0.035 g L1; bisdemethoxycurcumin: from 0.0002 to 0.035 g L1; and demethoxycurcumin: from 0.008 to 0.242 g L1) and analyzed in triplicate. The calibration curves were established by plotting the peak areas versus the concentration of each analyte.
water uptakeð%Þ ¼
Mt Mo 100 Mo
(2)
where Mt is the weight at time t and Mo corresponds to the weight of dry solid, determined after drying overnight at 105 C (before exposure to 95% RH). 2.8. Experimental design The surface-response methodology was used to study how the heating temperature (T) and the pH of the solution affected the dependent variables (mechanical properties, solubility, moisture content, water vapor permeability (WVP), and opacity). The levels of the independent variables were defined according to a 22 full factorial central composite design (star configuration) (Tables 1and 2). An analysis of variance (ANOVA), a multiple comparison test, and all statistical analyses were performed using the Statistica 6.0 software. The data were fitted to a second order equation (equation (3)) as a function of the independent variables.
Yi ¼ b0 þ b1 X1 þ b2 X2 þ b12 X1 X2 þ b11 X12 þ b22 X22 ;
(3)
where bn were constant regression coefficients, Yi were the dependent variables (tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility (S), moisture content (MC), WVP, and opacity (OP); and X1 and X2 were the coded independent variables (heating temperature and pH, respectively). After the surface-response results were obtained, the process conditions were optimized by multi-response analysis (Derringer & Suich, 1980). This method transformed response variables (Yi) into an individual function of dimensionless desirability (gi) (equation (4)), ranging from 0 (undesirable response) to 1 (desired response). The overall desirability function (G) (equation (5)) was obtained
2.7. Water uptake The film water sorption capacity was determined using the method of Dufresne, Dupeyre, and Vignon (2000). The dried sample films (20 mm 20 mm) were conditioned at 25 C in a desiccator containing sodium sulfate (RH 95%). Conditioning the samples in high-moisture atmosphere was preferred to the classical technique involving immersion in water because the film containing starch can partially dissolve in water after long exposure. During the first 12 h, the samples were weighed every hour; then they were weighed every 12 h until equilibrium was reached. This assay was performed in triplicate. The water uptake was calculated as follows:
Table 2 Predicted and experimental values of responses at optimum conditions. Propertiesa
Predicted
Experimental
RDb (%)
TS (MPa) E (%) WVP (g mm h1 m2 kPa1) S (%)
19.11 1.449 0.2030 38.13
17.99 1.758 0.166 36.32
6.23 17.58 17.73 4.75
0.76 0.530 0.03 0.75
a Tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and solubility in water (S) of turmeric flour films. b Relative deviation (RD): [(experimental value predicted value)/experimental value]/100.
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from the geometric means of individual desires. G was later maximized using the software Mathematic 5.0.
1=K G ¼ g1n1 þ g2n2 þ .. þ g1nK ;
WVP ¼ 0:215 0:0727X1 þ 0:103X1 2
Yi Ymin ; Ymax Ymin
(5)
where Ymin was the response minimum value and Ymax was the response maximum value, k was the number of considered responses, and n was the weight of each response. In the case of solubility, equation (4) had to be redesigned, to obtain the minimum values for these responses (equation (6)).
Gi ¼
Ymax Yi Ymax Ymin
(6)
Finally, turmeric flour films were prepared in the optimal conditions, to validate the optimized process conditions obtained by the multi-response analysis. The validation experiments were performed in triplicate, and the resulting films were characterized with respect to their mechanical properties, solubility, WVP, microstructure, and antioxidant activity. 3. Results and discussion 3.1. Chemical composition of the turmeric flour The turmeric flour contains 7.73 0.42 g/100 g moisture, 5.80 0.26 g/100 g ash, 0.88 0.02 g/100 g lipids, 9.25 0.11 g/ 100 g proteins, 2.94 0.54 g/100 g hemicellulose, 49.39 4.06 g/ 100 g cellulose, 5.3 0.4 g/100 g insoluble lignin, 1.6 0.3 g/100 g soluble lignin, and 24.84 g/100 g starch (38.51 0.01 g/100 g amylose and 61.5 g/100 g amylopectin). The results are expressed on dry basis. 3.2. Full experimental design Table 1 summarizes the results of the 22 full-factorial central composite design (star configuration). According to the analysis of variance (ANOVA), the models calculated for the tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility in water (S), moisture content (MC), water vapor permeability (WVP), and opacity of turmeric flour films (equations (7)e(13)) were statistically significant and predictive at a confidence level of 95% (p < 0.05), with F values greater than the critical values.
TS ¼ 17:44 þ 2:52X1 þ 4:11X2 2:72X1 2 3:67X2 2
R2 ¼ 0:90
(7) E ¼ 1:528 þ 0:203X1 0:533X2 2
(11)
(4)
where:
Gi ¼
MC ¼ 9:03 0:092X1 0:201X2 þ 0:78X1 2 R2 ¼ 0:92 0:62X2 2
R2 ¼ 0:90
YM ¼ 1449:18 þ 175:78X1 þ 503:67X2 240:55X1 2 R2 ¼ 0:90 197:45X1 X2 S ¼ 36:69 1:67X2 þ 3:84X1 2 þ 1:86X2 2 R2 ¼ 0:90 2:41X1 X2
(8)
(9)
(10)
R2 ¼ 0:80
OP ¼ 11:93 3:805X1 1:61X2 þ 0:825X1 2 þ 3:22X2 2 R2 ¼ 0:91 þ 2:22X1 X2
(12)
(13)
We used these models to generate the response surface (Figs. 1e4). Fig. 1(aec) depicts the response surfaces for TS, E, and YM of turmeric flour films plasticized with sorbitol. The response surface for TS displayed a maximum region between 85 and 92 C and pH 7.5 to 9.4 (Fig. 1a). Therefore, higher heating temperature and pH values produced a denser and mechanical stronger polymer matrix. Our team had observed this same behavior in the case of achira and amaranth flour films (Andrade-Mahecha et al., 2012; Tapia-Blácido et al., 2005, 2011). On the other hand, a similar temperature range and pH between 7.5 and 8.5 furnished higher elongation at break (Fig. 1b). Andrade-Mahecha et al. (2012) had also reported maximum values of tensile strength and elongation at break in similar temperature and pH ranges. Higher pH values (pH > 8.5) afforded the maximum values of YM, regardless of the heating temperature (Fig. 1c). At high pH (alkaline medium), the turmeric proteins may have reached maximum dissolution and undergone certain conformation changes, which affected the films mechanical properties. It was possible to associate the heating temperature effect on the mechanical properties of the turmeric flour film with starch gelatinization and protein denaturation. Thermal analysis of Curcuma longa Linneu starch by DSC showed that the gelatinization onset temperature (To), peak temperature (Tp), and conclusion temperature (Tc) were 70.8, 81.0 and 97.0 C, respectively (Braga et al., 2006). Therefore, high heating temperature (>85 C) promoted complete gelatinization of the starch present in the turmeric flour, due to amylose leaching. This culminated in increased interactions between the starch and other components of the polymeric matrix components (proteins, lipids, and fibers). Denaturation of the proteins present in the flour may also have increased the number of interactions among the several biopolymers, such as the polyphenol/protein interactions, due to the presence of lignin, a polyphenolic compound (Montaño-Leyva et al., 2013). Some authors reported that the high temperature of the prepared films should be understood in terms of a closely packed state where extensive intermolecular bonding occurs, inhibiting further orientation and better protein and starch chains alignment (Arvanitoyannis, Nakayama, & Aiba, 1998). Fig. 2a demonstrates that the solubility response surface reached a minimum between 80 and 88 C, at pH > 7.5. Hence, in intermediate heating temperatures and higher pH values yield less soluble films. Fig. 2b revealed that temperatures ranging from 82 to 90 C and higher pH values (9e9.4) defined a region of minimum moisture content. Higher pH values afforded films with lower moisture content (see Table 1). A temperature of 85 C and pH 9.4 (run 8) furnished the minimum moisture content (7.6 g/ 100 g). Therefore, high temperatures and pH values provided a network that displayed fewer hydrophilic groups to interact with the -OH groups of water molecules. More hydrophobic interactions should occur in these conditions because, apart from proteineprotein and starchestarch interactions, lipids should
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Fig. 1. Tensile strength (a), elongation at break (b), and Young’s modulus (c) of turmeric flour films as a function of heating temperature and pH.
interact with proteins, culminating in a turmeric flour film with lower solubility and moisture content. The presence of cellulose, hemicelluloses, and lignin in the turmeric flour also contributed to the lower affinity of the film with water. Lignin probably localized on the turmeric fibers surface, increasing the number of hydrophobic sites in the film matrix (Montaño-Leyva et al., 2013). On other hand, other authors reported that the addition of cellulose nanocrystals from kenaf fibers reduced water uptake, because a cellulose nanoparticle network originated, preventing starch swelling as well as water absorption well (Zainuddin, Ahmad, & Kargarzadeh, 2013). The lower hydrophilicity of
turmeric flour films could explain the lower E values (0.7e2%) obtained for these films as compared with amaranth flour (12.9 5.2%) (Tapia-Blácido et al., 2005), and achira flour (14.6%) (Andrade-Mahecha et al., 2012). Fig. 3 evidenced that high heating temperature (above 80 C) yielded films with lower WVP in all the studied pH range. According to Table 1, films produced at 85 C and pH 6.59 were less permeable to water vapor (run 7). Thus, the heating temperature affected solubility and WVP in a similar way. Maybe, rising heating temperature favored interactions among the biopolymers (starch, protein, lipid, and fiber) as well as homogenous distribution of
Fig. 2. Solubility in water (a) and moisture content (b) of turmeric flour films as a function of heating temperature and pH.
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these interactions within the film matrix, which may have resulted in lower WVP. Fig. 4 showed that lower heating temperature (78e82 C) and pH values (6.6e7.5) provided a more opaque turmeric flour film. The opacity of the turmeric flour films diminished with increasing heating temperature in the whole pH range tested here.
deviation values revealed that the predicted and experimental correlated well (Table 2). The turmeric flour films prepared with the optimal formulation were more resistant (17.99 MPa) than achira flour films (7.0 MPa) (Andrade-Mahecha et al., 2012) and amaranth flour films of caudatus and cruentus species (1.5e5.4 MPa) (Tapia-Blácido et al., 2007, 2011). However, the elongation was lower (1.78%) than that of films consisting of rice flour and cellulose fibers (4.0%) (Dias, Muller, Larotonda, & Laurindo, 2011), amaranth flour film (Tápia-Blácido et al., 2005, 2011), and achira flour films (22%) (AndradeMahecha et al., 2012). The turmeric flour films had WVP of 0.415 1010 g m1 s1 Pa1. This value is low compared with those of films made from amaranth flour of caudatus and cruentus species (0.8e 3.8 1010 g m1 s1 Pa1) (Tapia-Blácido et al., 2007, 2011), rice flour (0.8e1.1 1010 g m1 s1 Pa1) (Dias et al., 2010, 2011), and achira flour (5.3 1010 g m1 s1 Pa1) (Andrade-Mahecha et al., 2012). In the turmeric flour film, the fibers influence the film properties that depend on the fiberematrix interface; only good fibermatrix adhesion allows the fibers to act as reinforcement agents, increasing film stiffness (Andrade-Mahecha et al., 2012). The length
3.3. Determination of the optimum conditions and experimental validation The models calculated for the tensile strength (TS), solubility (S), water vapor permeability (WVP), and opacity (OP) of the turmeric flour films (Equations ((7), (10), (12) and (13)) furnished the desirability function (G). The minimum and maximum values of each response variable derived from the experimental results obtained in the experimental design (Table 1) gave the gi function by considering these minimum and maximum values. Optimized conditions afforded films with higher resistance to break, low solubility, moderate opacity, and good water vapor barrier property. In other words, optimization culminated in minimized solubility, WVP, and opacity and maximized TS.
2
14:64 þ 2:52X1 2:716X1 2 þ 4:113X2 3:764X2 2 G¼4 16:71 0:3786 þ 0:0727X1 0:1029X1 2 * 0:474
!3
!9
8:99 3:837X1 2 þ 1:667X2 1:857X2 2 þ 2:407X1 X2 * 10:19
10:54 3:805X1 0:825X1 2 þ 1:61X2 3:223X2 2 2:222X1 X2 * 15:55
!9
!3 31=4 5
(14)
The optimized G function furnished T ¼ 86.7 C and pH ¼ 8.5. Turmeric flour films prepared under these process conditions, helped to validate the optimization methodology. We measured and compared the TS, E, S, and WVP of the turmeric flour films with values predicted by Eqs. (7), (8), (10) and (12). The relative
and diameter of the fibers as well as their orientation and distribution in the polymeric matrix can affect the extent to which the fiber and the matrix adhere (Wollerdorfer & Bader, 1998). The solubility of the prepared turmeric flour film was lower (36.32%) as compared with amaranth flour films (42.2%) (Tapia-
Fig. 3. WVP of the turmeric flour films as a function of heating temperature and pH.
Fig. 4. Opacity of turmeric flour films as a function of heating temperature and pH.
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Blacido et al., 2007, 2005, 2011), potato peel films (41.2%) (Kang & Min, 2010), and achira flour films (38.3%) (Andrade-Mahecha et al., 2012). The fibers present in the turmeric flour must have incorporated into the matrix more easily suggesting a good degree of fiber-matrix interactions. Indeed, these fibers were spontaneously distributed in the turmeric flour. Such strong interaction between the matrix and the fibers (w65%) meant that the matrix and water interacted less, leading to lower water solubility. The incorporation of cellulose nanocrystals (CNCs) in the plasticized matrix of cassava starch biocomposites decreased water solubility (Zainuddin et al., 2013). Müller, Laurindo, and Yamashita (2009) also found that solubility decreased in cassava starch films with increasing amount of fibers (cellulose). 3.4. Optimized turmeric flour films microstruture
Fig. 5. SEM micrographs of turmeric flour films obtained in the optimized process conditions. (a) 500 (b) 1500 magnification.
Fig. 5(a, b) depict the turmeric flour films microstructure as analyzed by SEM at 500 and 1500 magnification. The micrographs show the surface and cross-sectional area of the films; the surface area corresponds to surface drying. The turmeric flour film had rougher surface, with waves, which affected film thickness (Fig. 5a). The micrograph of the cross-section area revealed a non- homogeneous structure with some denser regions and other regions containing cracks (Fig. 5b). This type of structure resulted from the different interactions taking place in the filmogenic matrix (starchestarch, starch-protein, proteine protein, lipidelipid, proteinelipid, and fiberefiber); the presence of lignocellulosic fiber also accounted for this structure. Together these characteristics could explain the low elongation at break achieved for the optimized films as compared with reported starch, protein, or flour films. Therefore, the poor elongation at break obtained in the present study probably stemmed from
Fig. 6. HPLC profile for (A) curcuminoids, (B) the extract from the turmeric pie, and (C) turmeric flour film prepared in the optimized conditions. Peaks relative to bisdemethoxycurcumin (a), demethoxycurcumin (b), and curcumin (c).
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hydrophobic lignin, which prevented strong linkages from forming between the cellulose fibers and starch (Gilfillan, Nguyen, Sopade, & Doherty, 2012). Lignin is a highly reactive thermoplastic polymer it essentially localizes on the fiber surface and covalently binds to cellulose molecules (Kunanopparat, Menut, Morel, & Guilbert, 2008). Meanwhile, the cellulose fibers were well cemented in the continuous phase, because they strongly interacted with the plasticized starch matrix (Avérous, Fringant, & Moro, 2001). 3.5. Antioxidant activity of optimized turmeric flour films Fig. 6(a) illustrates the chromatogram patterns of curcumin, demethoxycurcumin, and bisdesmethoxycurcumin. The peak at approximately 20, 18.5, and 17 min of retention corresponded to curcumin, demethoxycurcumin, and bisdesmethoxycurcumin, respectively. Peaks with similar retention times in the chromatogram of the dye extracted from the turmeric rhizomes (Fig. 6b), confirmed the presence of these specific curcuminoids in the extract. The chromatogram of the turmeric film displayed the same peaks at the same retention times, attesting to the presence of the three curcuminoids (Fig. 6c). Only the intensities of the peaks in the chromatograms were different, a result of the different concentrations of curcuminoids in the samples. The turmeric rhizomes extract contained larger curcumin concentrations (3.741 g L1) as compared with demethoxycurcumin (3.515 g L1) and bisdemethoxycurcumin (3.520 g L1). The bisdemethoxycurcumin, demethoxycurcumin, and curcumin concentrations in the turmeric flour film were 0.0037, 0.0008, and 0.0001 mg.mL1, respectively. Therefore, the process used to extract the dye from turmeric pie removed greater amount curcumin. The turmeric films presented larger bisdemethoxycurcumin and demethoxycurcumin amounts. DPPH analysis of the optimal film plasticized with sorbitol gave 50.8% AA. This value was lower than that obtained for some antioxidants used in the industry, such as butylated hydroxyl anisole (BHA) (94%AA) and ascorbic acid (92%AA) (Yu-Ling, Yang, & Mau, 2008), but it was important considering that the raw material used to prepare the films was a residue. Because turmeric flour films displayed effective antioxidant property, they could be used as active packaging.
50
Water uptake (%)
40 30 20 10 0 0
20
40
60
80
100
120
140
160
180
Time (h) Fig. 7. Behavior of film swelling during conditioning at 95% RH versus time.
3.6. Optimized film water sorption behavior Fig. 7 shows the sorption kinetics of the optimized turmeric flour film. Before 20 h, water uptake was fast, at longer times (>20 h), water absorption slowed down and reached a plateau, where the film achieved equilibrium, with water uptake of 45.4% 4.05. This value was similar to that reported for starchcellulose microfibril composites (Dufresne et al., 2000), but was lower than that reported for wheat starch film (Lu, Weng, & Cao, 2005). Hence, the presence of fibers, protein, and lipids decreased the turmeric flour film water absorption capacity. 4. Conclusion The turmeric dye solvent extraction residue constitutes a promising source to develop active biodegradable films: the turmeric flour film contains residual curcuminoids with effective antioxidant property. The process parameters (heating temperature and pH) used during film formation affect the mechanical properties, solubility, moisture content, water vapor permeability, and opacity of the resulting film. High heating temperature promotes more interactions between the polymers present in the turmeric flour (starchestarch, proteineprotein, proteinelipid, and fiberefiber), furnishing a more resistant polymeric structure with low WVP, moisture content, and opacity. Higher pH values also favor a more mechanically resistant, denser matrix with lower water solubility and water vapor permeability. The presence of lignocellulosic material contributes to enhanced hydrophobicity culminating in less homogenous and less flexible turmeric flour films. The optimal conditions to produce turmeric flour films with good tensile strength, low solubility, low WVP, and low opacity are T ¼ 86.7 C and pH ¼ 8.5. Acknowledgment The authors wish to thank Fundação de Amparo à Pesquisa do Estado de São Paulo (São Paulo Research Support Foundatione FAPESP) and CAPES (Coordenacão de Aperfeicionamento de Pessoal de Nível Superior) for financial support. References Andrade-Mahecha, M. M., Tapia-Blácido, D. R., & Menegalli, F. C. (2012). Development and optimization of biodegradable films based on achira flour. Carbohydrate Polymers, 88(2), 449e458. AOAC. (1997). Official methods of analysis of AOAC International (16th ed.). Washington: Association of Official Analytical Chemists. Arvanitoyannis, I., Nakayama, A., & Aiba, S. (1998). Edible films made from hydroxypropyl starch and gelatin and plasticized by polyols and water. Carbohydrate Polymers, 36(2/3), 105e119. ASTM. (1995). Standard test method for tensile properties of thin plastic sheeting (D882e95) and standard method for water vapor transmission of materials (E 96-95). In Annual book of ASTM standards. Philadelphia: American Society for Testing and Materials. Avérous, L., Fringant, C., & Moro, L. (2001). Plasticized starchecellulose interactions in polysaccharides composites. Polymer, 42(15), 6565e6572. Bligh, E. G., & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, 37, 911e917. Braga, M. E., Leal, P. F., Carvalho, J. E., & Meireles, M. A. (2003). Comparison of yield, composition, and antioxidant activity of turmeric (Curcuma longa L.) extracts obtained using various techniques. Journal of Agriculture Food Chemistry, 51, 6604e6611. Braga, M. E. M., & Meireles, M. A. A. (2007). Accelerated solvent extraction and Fractioned extraction to obtain the Curcuma longa volatile oil and oleoresin. Journal of Food Process Engineering, 30, 501e521. Braga, M. E. M., Moreschi, S. R. M., & Meireles, M. A. A. (2006). Effects of supercritical fluid extraction on Curcuma longa L. and Zingiberofficinale R. starches. Carbohydrate Polymers, 63, 340e346. Derringer, G., & Suich, R. (1980). Simultaneous optimization of several response variable. Journal of Quality Technology, 12(4), 214e219. Dias, A. B., Muller, C. M. O., Larotonda, F. D. S., & Laurindo, J. (2010). Biodegradable films based on rice starch and rice flour. Journal of Cereal Science, 51, 213e219.
B.C. Maniglia et al. / LWT - Food Science and Technology 56 (2014) 269e277 Dias, A. B., Muller, C. M. O., Larotonda, F. D. S., & Laurindo, J. (2011). Mechanical and barrier properties of composite films based on rice flour and cellulose fibers. LWT e Food Science and Technology, 44, 535e542. Dufresne, A., Dupeyre, D., & Vignon, M. R. (2000). Cellulose microfibrils from potato tuber cells: processing and characterization of starchecellulose microfibril composites. Journal of Applied Polymer Science, 76, 2080e2092. Euterpio, M. A., Cavaliere, C., Capriotti, A. L., & Crescenzi, C. (2011). Extending the applicability of pressurized hot water extraction to compounds exhibiting limited water solubility by pH control: curcumin from the turmeric rhizome. Analytical and Bioanalytical Chemistry, 401(9), 2977e2985. Gilfillan, W. N., Nguyen, D. M. T., Sopade, P. A., & Doherty, W. O. S. (2012). Preparation and characterization of composites from starch and sugar cane fiber. Industrial Crops and Products, 40, 45e54. Gontard, N., Guilbert, S., & Cuq, J. L. (1992). Edible wheat gluten films: influence of the main process variables on film properties using response surface methodology. Journal of Food Science, 57(1), 190e195. Gontard, N., Guilbert, S., & Cuq, J. L. (1993). Water and glycerol as plasticizers affect mechanical and water vapor barrier properties of an edible wheat gluten film. Journal of Food Science, 58(1), 206e211. Gouveia, E. R., Do Nascimento, R. T., & Souto-Maior, A. M. (2009). Validação de metodologia para a caracterização química de bagaço de cana-de-açúcar. Química Nova, 32(6), 1500e1503. Grinberg, V. Y., & Tolstoguzov, V. B. (1997). Thermodynamic incompatibility of proteins and polysaccharides in solutions. Food Hydrocolloids, 11, 145e158. Hunterlab. (1997). Universal Software Versions 3.2 and above. User’s Manual. Manual Version 1.5. Reston, Virginia: Hunter Associates Laboratory. Joshi, P., Jain, S., & Sharma, V. (2009). Turmeric a natural source of edible yellow colour. International Journal of Food Science & Technology, 44, 2402e2406. Juliano, B. O. (1971). A simplified assay for milled-rice amylose. Cereal Science Today, 16, 334e340. Jyothi, A. N., Moorthy, S. N., & Vimla, B. (2003). Physicochemical and functional properties of starch extracted from two species of Curcuma. International Journal of Food Properties, 6, 135e145. Kang, H. J., & Min, S. C. (2010). Potato peel-based biopolymer film development using high-pressure homogenization, irradiation, and ultrasound. LWT e Food Science and Technology, 43, 903e909. Kunanopparat, T., Menut, P., Morel, M. H., & Guilbert, S. (2008). Reinforcement of plasticized wheat gluten with natural fibers: from mechanical improvement to deplasticizing effect. Composites Part A: Applied Science and Manufacturing, 39, 777e785.
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Kuttigounder, D., Rao, L., & Bhattacharya, S. (2011). Turmeric powder and starch: selected physical, physicochemical, and microstructural properties. Journal of Food Science, 76, C1284eC1291. Lu, Y. S., Weng, L. H., & Cao, X. D. (2005). Biocomposites of plasticized starch reinforced with cellulose crystallites from cottonseed linter. Macromolecular Bioscience, 5, 1101e1107. Maheshwari, R. K., Singh, A. K., Gaddipati, J., & Srimal, R. C. (2006). Multiple biological activities of curcumin: a short review. Life Sciences, 78, 2081e2087. Marins, J. T., Cerqueira, M. A., & Vicente, A. A. (2012). Influence of -tocopherol on physicochemical properties of chitosan e based films. Food Hydrocolloids, 27, 220e227. Montaño-Leyva, B., da Silva, G. G., Gastaldi, E., Torres-Chávez, P., Gontard, N., & Angellier-Coussya, H. (2013). Biocomposites from wheat proteins and fibers: structure/mechanical properties relationships. Industrial Crops and Products, 43, 545e555. Müller, C. M. O., Laurindo, J. B., & Yamashita, F. (2009). Effect of cellulose fibers addition on the mechanical properties and water vapor barrier of starch-based films. Food Hydrocolloids, 23(5), 1328e1333. Satyanarayana, K. G., Arizaga, G. G. C., & Wypych, F. (2009). Biodegradable composites based on lignocellulosic fibersdan overview. Progress in Polymer Science, 34, 982e1021. Tapia-Blácido, D., Mauri, A. N., Menegalli, F. C., Sobral, P. J. A., & Añón, M. C. (2007). Contribution of the starch, protein, and lipid fractions to the physical, thermal, and structural properties of Amaranth (Amaranthus caudatus) flour films. Journal of Food Science, 72, E293eE300. Tapia-Blácido, D., Sobral, P. J., & Menegalli, F. C. (2005). Development and characterization of biofilms based on Amaranth flour (Amaranthus caudatus). Journal of Food Engineering, 67, 215e223. Tapia-Blácido, D., Sobral, P. J. A., & Menegalli, F. C. (2011). Optimization of amaranth flour films plasticized with glycerol and sorbitol by multi-response analysis. LWT e Food Science and Technology, 44(8), 1731e1738. Wollerdorfer, M., & Bader, H. (1998). Influence of natural fibers on the mechanical properties of biodegradable polymers. Industrial Crops and Products, 8, 105e112. Yallapu, M. M., Jaggi, M., & Chauhan, S. C. (2012). Curcumin nanoformulations: a future nanomedicine for cancer. Drug Discovery Today, 17, 71e80. Yu-Ling, L., Yang, J. H., & Mau, J. L. (2008). Antioxidant properties of water extracts from Monascus fermented soybeans. Food Chemistry, 106, 1128e1137. Zainuddin, S. Y. Z., Ahmad, I., & Kargarzadeh, H. (2013). Cassava starch biocomposites reinforced with cellulose nanocrystals from kenaf fibers. Composite Interfaces, 20(3), 189e199.
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LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Development of bioactive edible film from turmeric dye solvent extraction residue B.C. Maniglia, J.R. Domingos, R.L. de Paula, D.R. Tapia-Blácido* Departamento de Química, Faculdade de Filosofia, Ciências e Letras, Universidade de São Paulo, Av. Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 July 2013 Received in revised form 25 November 2013 Accepted 9 December 2013
We developed and characterized turmeric flour films using the turmeric dye solvent extraction residue. We evaluated how the heating temperature and pH affected film properties using a 22 central composite design. Multi-response analysis furnished the film formulation that offered larger resistance to break, as well as lower water solubility, WVP, and opacity. The heating temperature and pH affected the mechanical properties, solubility, moisture content, WVP, and opacity of the resulting film. High heating temperature promoted more interactions between the polymers present in the turmeric flour (starch, protein, lipid, and fiber), affording a more resistant polymeric structure with lower WVP, moisture content, and opacity. Higher pH values also favored a more mechanically resistant and dense matrix with lower water solubility and WVP. The optimized conditions were: T ¼ 86.7 C and pH ¼ 8.5. The films produced under these conditions displayed high mechanical strength (18 MPa), low solubility (36%), and low WVP (0.167 g mm h1 m2 kPa1). However, because these films contained lignocellulosic fibers, they presented low elongation at break (1.8%), which elicited a non-continuous structure. HPLC and DPPH assays showed that the turmeric dye solvent extraction residue can be a promising source to develop films with antioxidant activity. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Curcumin Turmeric Bioactive film Antioxidant Mechanical properties
1. Introduction It is possible to make edible films from biopolymers such as polysaccharides and proteins extracted from plant or animal raw material. In general, these biopolymers constitute a poor barrier to water vapor; moreover, compared with synthetic packaging, they have unsatisfactory mechanical strength and elongation. To make protein and starch films mechanically stronger, some authors have incorporated fibers of different plant origins (hemp, jute, flax, bagasse, cotton, sisal, wheat fibers, etc.) into biocomposites, to reinforce agromaterials (Montaño-Leyva et al., 2013; Satyanarayana, Arizaga, & Wypych, 2009). The results are not always favorable: the polymers may be thermodynamically incompatible, culminating in phase separation (Grinberg & Tolstoguzov, 1997). To overcome this problem, researchers have prepared biodegradable films from natural mixtures (carbohydrates, proteins, lipids, and fibers) obtained in the flour form from raw materials of plant origin such as cereals, tubers, and rhizomes (Andrade-Mahecha, Tapia-Blácido, & Menegalli, 2012; Dias, Muller,
* Corresponding author. Tel.: þ55 16 36020580; fax: þ55 16 36332660. E-mail addresses: [email protected], [email protected] (D.R. Tapia-Blácido). 0023-6438/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.lwt.2013.12.011
Larotonda, & Laurindo, 2010; Gontard, Guilbert, & Cuq, 1993; TapiaBlácido, Mauri, Menegalli, Sobral, & Añón, 2007; Tapia-Blácido, Sobral, & Menegalli, 2005, 2011). A recent trend is to use industrial residue to obtain natural mixtures of biopolymers as flour, which may provide the packaging market with a competitive product. Curcuma longa L. belongs to the family Zingiberaceae, commonly known as turmeric. It consists of a rhizomatus perennial herb with primary and secondary rhizomes; and its shape varies from spherical to slightly conical, hemispherical, or cylindrical (Jyothi, Moorthy, & Vimla, 2003). This herb is bright yellow because it contains Curcumin, a diphenolic compound, that exerts antiinflammatory action and is a potential candidate to treat cystic fibrosis, Alzheimer’s, malarial diseases, and cancer (Maheshwari, Singh, Gaddipati, & Srimal, 2006; Yallapu, Jaggi, & Chauhan, 2012). Turmeric also contains the curcuminoids demethoxycurcumin and bisdemethoxycurcumin (Joshi, Jain, & Sharma, 2009). One can extract the turmeric oleoresin from dried rhizomes by Soxhlet extraction, sonication, and liquideliquid extraction using acetone, methanol, ethanol, and isopropanol as organic solvents. It is also possible to obtain this resin by supercritical fluid extraction with CO2 (Braga, Leal, Carvalho, & Meireles, 2003; Braga, Moreschi, & Meireles, 2006; Euterpio, Cavaliere, Capriotti, & Crescenzi, 2011;
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Joshi et al., 2009). The turmeric oleoresin usually contains 30e45 g/ 100 g curcuminoids and 15e20 g/100 g volatile oil. Because this extraction generates a residue that consists predominantly of starch and fibers and may present residual levels of curcuminoids with antioxidant properties (Braga et al., 2003, 2006; Kuttigounder, Rao, & Bhattacharya, 2011), we propose that this residue be used to develop a biodegradable film. The resulting turmeric film could be an active packaging material the presence of curcuminoids confers the film an antioxidant character. Therefore, this study aimed to develop turmeric films from turmeric dye solvent extraction residue using the response surface methodology and multi-response analysis, to obtain the formulation that would afford the turmeric flour film with optimal mechanical properties and low water vapor permeability, and to evaluate the antioxidant property of these films. 2. Material and methods 2.1. Materials The turmeric powder (Curcuma longa L) was furnished by the industry “Flores e Ervas” (Campinas, Brazil). The turmeric flour was obtained by milling and sieving (0.075 mm) the turmeric dye soxhlet extraction residue. The extraction followed the method proposed by Braga and Meireles (2007), using ethanol/isopropanol (1:1) (Synth - São Paulo, Brazil). Sorbitol, used as plasticizer, was purchased from SigmaeAldrich (São Paulo, Brazil). 2.2. Turmeric flour chemical analyses The turmeric flour moisture, crude protein, and ash contents were analyzed according to standard AOAC methods (AOAC, 1997). The starch amylose content was determined using the colorimetric method of Juliano (1971). The lipids content was calculated by the method of Bligh and Dyer (1959). The cellulose, hemicellulose, and lignin content were determined according to the methodology described by Gouveia, Do Nascimento, & Soto-Maior (2009). The material was submitted to hydrolysis with H2SO4 at 720 mL/L, to quantify carbohydrates, organic acid, furfural, and hydroxymethylfurfural by HPLC. The concentrations of cellulose and hemicellulose were calculated using the following conversion factors: cellulose (0.90 glucose mass, 0.95 cellobiose mass, 1.20 HMF mass, 3.09 formic acid mass); hemicellulose (0.88 xylose mass, 0.88 arabinose mass, 0.72 acetic acid mass, 1.37 furfural mass). Insoluble lignin was determined by the Klasson method, and soluble lignin was determined by measuring the absorbance at 280 nm. All the analyses were performed in triplicate. 2.3. Film preparation The turmeric flour films were prepared by casting. Initially, a 5 g/ 100 g suspension was prepared in deionized water and homogenized for 30 min in a magnetic stirrer (IKA MAGÒ C-HS7-Marconi, Piracicaba - Brazil). The pH of the solution was adjusted to 6.59, 7.0, 8.0, 9.0, or 9.41 using HCl 1 mol/L and NaOH 1 mol/L solution. Then, the suspension was heated at 78, 80, 85, 90, or 92 C for 4 h while applying homogenization cycles at 12,000 rpm for 2 min at every hour using an ultra-turrax homogenizer (Ultracleaner 1400, Unique, Indaiatuba, Brazil). The plasticizer (30 g sorbitol/100 g flour) was added, and the mixture was heated for 20 min. In a preliminary test was determined that as the optimal concentration of sorbitol for turmeric flour film production with low solubility and high mechanical resistance. Then, the solution was sonicated
for 20 min, to remove bubbles. Subsequently, the solution was poured onto acrylic plates maintaining a weight of 0.15 g m2 and dried for 7 h in an oven with forced circulation (MA Q314M, Quimis, Piracicaba-Brazil), at 35 C. Prior to characterization, all the films were preconditioned for at least 48 h in desiccators containing a saturated NaBr solution (58% RH). 2.4. Films properties The mechanical tests were performed using a texture analyzer TA TX Plus (TA Instrument, England). The tensile strength (TS) and elongation at break (E) were obtained according to the ASTM D882- 95 method (ASTM., 1995), taking an average of five determinations in each case. Sample films were cut into 2.54 cm wide strips with a length of at least 10 cm. The initial grip separation and the crosshead speed were set at 80 mm and 1.0 mm s1, respectively. Young’s modulus (YM) was calculated as the inclination of the initial linear portion of the stress versus strain curve using the software Texture Expert V.1.22 (SMS). The opacity was determined according to the Hunterlab method (1997), using a portable colorimeter MiniScan XE (Hunterlab). The solubility in water was calculated as the percentage of dry matter of the solubilized film after immersion for 24 h in water at 25 2 C (Gontard, Guilbert, & Cuq, 1992) as described by Tapia-Blácido et al. (2011). The moisture content in the films was also determined by drying the materials in an oven at 105 C until constant weight (w24 h). The water vapor permeability (WVP) test was performed using a modified E96-95 ASTM Standard method (ASTM, 1995) at 25 2 C. Film samples were sealed over the circular opening of a permeation cell containing silica gel, and the cells were then placed in desiccators containing distilled water. After the samples had reached steady-state conditions (w20 h), the cell was weighed every 1 h, for 9 h, using an analytical scale. The WVP was calculated as WVP ¼ w$x/t$ADP,where x was the average thickness of the films, A was the permeation area (0.00196 m2), DP was the difference between the partial pressure of the atmosphere over silica gel and over pure water (3.168 kPa, at 25 C), and the term w/t was calculated by linear regression using data of weight gain as a function of time. Solubility, WVP, moisture content, and opacity were analyzed in triplicate. 2.5. Scanning electron microscopy (SEM) Film samples were maintained in a desiccator with silica gel for seven days and then fractured with liquid nitrogen, to investigate the samples cross-section. The samples were placed in aluminum holders and coated with gold by sputtering (Sputter Coater, model SCD050). A Microscope Scanning Electron model ZEISS EVO-50 under an accelerating voltage of 20 kV was used to analyze samples. 2.6. Optimal turmeric flour films antioxidant activity The turmeric flour films antioxidant property was determined using two techniques: DPPH and HPLC. The curcuminoids present in the film were extracted using 2 mL of methanol for every 100 mg of the film, and the mixture was incubated for 3 h at room temperature. Next, 500 mL of the mixture supernatant (film/methanol) was added to 2 mL of the methanolic DPPH solution (0.06 mmol/L), and the resulting mixture was stirred for 30 min, at room temperature, and protected from light. The remaining DPPH was determined by absorbance at 517 nm using an HP Hewlett Packard 8453 spectrophotometer coupled to a microcomputer HP Vectra XA 51166. The control consisted of 500 mL of DPPH solution
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271
Table 1 Mechanical properties, solubility in water, moisture content, water vapor permeability, and opacity of turmeric flour film plasticized with sorbitol according to the full-factorial design 22 central composite designs. >). Test
Ta (X1b)
pH (X2b)
TSc (MPa)
1 2 3 4 5 6 7 8 9 10 11
80 80 90 90 78 92 85 85 85 85 85
7 (1) 9 (þ1) 7 (1) 9 (þ1) 8 (0) 8 (0) 6.59 (1.414) 9.41 (þ1.414) 8 (0) 8 (0) 8 (0)
5.7 15.5 11.5 19.5 6.3 13.7 2.8 13.4 17.4 18.0 16.9
a b c
(1) (1) (þ1) (þ1) (1.414) (þ1.414) (0) (0) (0) (0) (0)
1.4 0.5 2.9 2.8 2.4 2.6 0.3 3.1 4.8 3.7 1.4
E (%) 0.7 0.8 0.7 1.2 1.2 2.0 0.6 0.6 1.7 1.6 1.6
YM (MPa) 0.3 0.1 0.2 0.1 0.1 0.4 0.1 0.2 0.2 0.2 0.2
527.1 1811.6 1362.4 1857.1 601.5 973.0 462.1 2053.0 1367.0 1511.0 1491.1
15.2 39.6 15.6 99.8 92 94.8 27.2 284 121 133 201
WVP (g mm h1 m2 kPa1)
S (%) 39.3 42.4 45.5 38.9 44.7 45.7 44.7 37.8 36.9 35.5 37.7
1.9 9.4 0.5 1.9 2.8 0.8 5.4 5.4 0.2 0.1 0.2
0.178 0.400 0.186 0.220 0.594 0.304 0.100 0.190 0.214 0.216 0.216
0.004 0.07 0.20 0.03 0.02 0.06 0.04 0.10 0.11 0.05 0.007
MC (g/100 g) 9.1 8.9 8.9 8.7 11.0 10.8 8.5 7.6 9.0 9.0 9.0
0.4 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.1 0.1
OP (%) 20.9 15.0 11.4 14.4 21.3 6.9 22.5 15.3 11.8 11.8 12.1
0.1 0.2 0.5 3.0 1.1 0.2 0.1 0.4 1.1 0.2 0.1
T ( C). Independent variables values (the values between brackets are the coded variables). Tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility (S), water vapor permeability (WVP), moisture content (M), opacity (OP).
(0.06 mmol/L). The antioxidant activity of the films was calculated according to Equation (1) and expressed as percentage of antioxidant activity (%AA) (Marins, Cerqueira, & Vicente, 2012).
Asample AA% ¼ 100 1 Acontrol
(1)
where: AA ¼ antioxidant activity; Asample ¼ absorbance of the solution containing the sample; Acontrol ¼ absorbance of the DPPH solution without addition of the film. To analyze the antioxidant activity by HPLC (Model: CTO10ASVP, Shimadzu), 20 mL of the supernatant (film/methanol) was used in the following conditions: C-18 column (4.6 mm 250 mm, 5 mm), oven temperature ¼ 40 C, detector ¼ arrangement LED (420 nm), loop ¼ 20 L, flow ¼ 1.0 mL.min1. The mobile phase consisted of 450 mL/L acetonitrile in 550 mL/L aqueous solution of 10 mL/L acetic acid. The gradient program was as follows: 0e 12 min, 45 mL/L acetonitrile; 12e32 min, 450e1000 mL/L acetonitrile; 32e40 min, 1000 mL/L acetonitrile. The standard curcumin, demethoxycurcumin, and bisdemethoxycurcumin were obtained from Fluka Analytical, Switzerland (98%). All the other chemicals and reagents were purchased from E-Merck and were analytical grade. The curcuminoids standard methanol solutions were freshly prepared, to construct the calibration curve. To obtain this curve, five solutions of each type of curcuminoid were prepared at different concentrations (curcumin: from 0.002 to 0.035 g L1; bisdemethoxycurcumin: from 0.0002 to 0.035 g L1; and demethoxycurcumin: from 0.008 to 0.242 g L1) and analyzed in triplicate. The calibration curves were established by plotting the peak areas versus the concentration of each analyte.
water uptakeð%Þ ¼
Mt Mo 100 Mo
(2)
where Mt is the weight at time t and Mo corresponds to the weight of dry solid, determined after drying overnight at 105 C (before exposure to 95% RH). 2.8. Experimental design The surface-response methodology was used to study how the heating temperature (T) and the pH of the solution affected the dependent variables (mechanical properties, solubility, moisture content, water vapor permeability (WVP), and opacity). The levels of the independent variables were defined according to a 22 full factorial central composite design (star configuration) (Tables 1and 2). An analysis of variance (ANOVA), a multiple comparison test, and all statistical analyses were performed using the Statistica 6.0 software. The data were fitted to a second order equation (equation (3)) as a function of the independent variables.
Yi ¼ b0 þ b1 X1 þ b2 X2 þ b12 X1 X2 þ b11 X12 þ b22 X22 ;
(3)
where bn were constant regression coefficients, Yi were the dependent variables (tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility (S), moisture content (MC), WVP, and opacity (OP); and X1 and X2 were the coded independent variables (heating temperature and pH, respectively). After the surface-response results were obtained, the process conditions were optimized by multi-response analysis (Derringer & Suich, 1980). This method transformed response variables (Yi) into an individual function of dimensionless desirability (gi) (equation (4)), ranging from 0 (undesirable response) to 1 (desired response). The overall desirability function (G) (equation (5)) was obtained
2.7. Water uptake The film water sorption capacity was determined using the method of Dufresne, Dupeyre, and Vignon (2000). The dried sample films (20 mm 20 mm) were conditioned at 25 C in a desiccator containing sodium sulfate (RH 95%). Conditioning the samples in high-moisture atmosphere was preferred to the classical technique involving immersion in water because the film containing starch can partially dissolve in water after long exposure. During the first 12 h, the samples were weighed every hour; then they were weighed every 12 h until equilibrium was reached. This assay was performed in triplicate. The water uptake was calculated as follows:
Table 2 Predicted and experimental values of responses at optimum conditions. Propertiesa
Predicted
Experimental
RDb (%)
TS (MPa) E (%) WVP (g mm h1 m2 kPa1) S (%)
19.11 1.449 0.2030 38.13
17.99 1.758 0.166 36.32
6.23 17.58 17.73 4.75
0.76 0.530 0.03 0.75
a Tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and solubility in water (S) of turmeric flour films. b Relative deviation (RD): [(experimental value predicted value)/experimental value]/100.
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from the geometric means of individual desires. G was later maximized using the software Mathematic 5.0.
1=K G ¼ g1n1 þ g2n2 þ .. þ g1nK ;
WVP ¼ 0:215 0:0727X1 þ 0:103X1 2
Yi Ymin ; Ymax Ymin
(5)
where Ymin was the response minimum value and Ymax was the response maximum value, k was the number of considered responses, and n was the weight of each response. In the case of solubility, equation (4) had to be redesigned, to obtain the minimum values for these responses (equation (6)).
Gi ¼
Ymax Yi Ymax Ymin
(6)
Finally, turmeric flour films were prepared in the optimal conditions, to validate the optimized process conditions obtained by the multi-response analysis. The validation experiments were performed in triplicate, and the resulting films were characterized with respect to their mechanical properties, solubility, WVP, microstructure, and antioxidant activity. 3. Results and discussion 3.1. Chemical composition of the turmeric flour The turmeric flour contains 7.73 0.42 g/100 g moisture, 5.80 0.26 g/100 g ash, 0.88 0.02 g/100 g lipids, 9.25 0.11 g/ 100 g proteins, 2.94 0.54 g/100 g hemicellulose, 49.39 4.06 g/ 100 g cellulose, 5.3 0.4 g/100 g insoluble lignin, 1.6 0.3 g/100 g soluble lignin, and 24.84 g/100 g starch (38.51 0.01 g/100 g amylose and 61.5 g/100 g amylopectin). The results are expressed on dry basis. 3.2. Full experimental design Table 1 summarizes the results of the 22 full-factorial central composite design (star configuration). According to the analysis of variance (ANOVA), the models calculated for the tensile strength (TS), elongation at break (E), Young’s modulus (YM), solubility in water (S), moisture content (MC), water vapor permeability (WVP), and opacity of turmeric flour films (equations (7)e(13)) were statistically significant and predictive at a confidence level of 95% (p < 0.05), with F values greater than the critical values.
TS ¼ 17:44 þ 2:52X1 þ 4:11X2 2:72X1 2 3:67X2 2
R2 ¼ 0:90
(7) E ¼ 1:528 þ 0:203X1 0:533X2 2
(11)
(4)
where:
Gi ¼
MC ¼ 9:03 0:092X1 0:201X2 þ 0:78X1 2 R2 ¼ 0:92 0:62X2 2
R2 ¼ 0:90
YM ¼ 1449:18 þ 175:78X1 þ 503:67X2 240:55X1 2 R2 ¼ 0:90 197:45X1 X2 S ¼ 36:69 1:67X2 þ 3:84X1 2 þ 1:86X2 2 R2 ¼ 0:90 2:41X1 X2
(8)
(9)
(10)
R2 ¼ 0:80
OP ¼ 11:93 3:805X1 1:61X2 þ 0:825X1 2 þ 3:22X2 2 R2 ¼ 0:91 þ 2:22X1 X2
(12)
(13)
We used these models to generate the response surface (Figs. 1e4). Fig. 1(aec) depicts the response surfaces for TS, E, and YM of turmeric flour films plasticized with sorbitol. The response surface for TS displayed a maximum region between 85 and 92 C and pH 7.5 to 9.4 (Fig. 1a). Therefore, higher heating temperature and pH values produced a denser and mechanical stronger polymer matrix. Our team had observed this same behavior in the case of achira and amaranth flour films (Andrade-Mahecha et al., 2012; Tapia-Blácido et al., 2005, 2011). On the other hand, a similar temperature range and pH between 7.5 and 8.5 furnished higher elongation at break (Fig. 1b). Andrade-Mahecha et al. (2012) had also reported maximum values of tensile strength and elongation at break in similar temperature and pH ranges. Higher pH values (pH > 8.5) afforded the maximum values of YM, regardless of the heating temperature (Fig. 1c). At high pH (alkaline medium), the turmeric proteins may have reached maximum dissolution and undergone certain conformation changes, which affected the films mechanical properties. It was possible to associate the heating temperature effect on the mechanical properties of the turmeric flour film with starch gelatinization and protein denaturation. Thermal analysis of Curcuma longa Linneu starch by DSC showed that the gelatinization onset temperature (To), peak temperature (Tp), and conclusion temperature (Tc) were 70.8, 81.0 and 97.0 C, respectively (Braga et al., 2006). Therefore, high heating temperature (>85 C) promoted complete gelatinization of the starch present in the turmeric flour, due to amylose leaching. This culminated in increased interactions between the starch and other components of the polymeric matrix components (proteins, lipids, and fibers). Denaturation of the proteins present in the flour may also have increased the number of interactions among the several biopolymers, such as the polyphenol/protein interactions, due to the presence of lignin, a polyphenolic compound (Montaño-Leyva et al., 2013). Some authors reported that the high temperature of the prepared films should be understood in terms of a closely packed state where extensive intermolecular bonding occurs, inhibiting further orientation and better protein and starch chains alignment (Arvanitoyannis, Nakayama, & Aiba, 1998). Fig. 2a demonstrates that the solubility response surface reached a minimum between 80 and 88 C, at pH > 7.5. Hence, in intermediate heating temperatures and higher pH values yield less soluble films. Fig. 2b revealed that temperatures ranging from 82 to 90 C and higher pH values (9e9.4) defined a region of minimum moisture content. Higher pH values afforded films with lower moisture content (see Table 1). A temperature of 85 C and pH 9.4 (run 8) furnished the minimum moisture content (7.6 g/ 100 g). Therefore, high temperatures and pH values provided a network that displayed fewer hydrophilic groups to interact with the -OH groups of water molecules. More hydrophobic interactions should occur in these conditions because, apart from proteineprotein and starchestarch interactions, lipids should
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273
Fig. 1. Tensile strength (a), elongation at break (b), and Young’s modulus (c) of turmeric flour films as a function of heating temperature and pH.
interact with proteins, culminating in a turmeric flour film with lower solubility and moisture content. The presence of cellulose, hemicelluloses, and lignin in the turmeric flour also contributed to the lower affinity of the film with water. Lignin probably localized on the turmeric fibers surface, increasing the number of hydrophobic sites in the film matrix (Montaño-Leyva et al., 2013). On other hand, other authors reported that the addition of cellulose nanocrystals from kenaf fibers reduced water uptake, because a cellulose nanoparticle network originated, preventing starch swelling as well as water absorption well (Zainuddin, Ahmad, & Kargarzadeh, 2013). The lower hydrophilicity of
turmeric flour films could explain the lower E values (0.7e2%) obtained for these films as compared with amaranth flour (12.9 5.2%) (Tapia-Blácido et al., 2005), and achira flour (14.6%) (Andrade-Mahecha et al., 2012). Fig. 3 evidenced that high heating temperature (above 80 C) yielded films with lower WVP in all the studied pH range. According to Table 1, films produced at 85 C and pH 6.59 were less permeable to water vapor (run 7). Thus, the heating temperature affected solubility and WVP in a similar way. Maybe, rising heating temperature favored interactions among the biopolymers (starch, protein, lipid, and fiber) as well as homogenous distribution of
Fig. 2. Solubility in water (a) and moisture content (b) of turmeric flour films as a function of heating temperature and pH.
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these interactions within the film matrix, which may have resulted in lower WVP. Fig. 4 showed that lower heating temperature (78e82 C) and pH values (6.6e7.5) provided a more opaque turmeric flour film. The opacity of the turmeric flour films diminished with increasing heating temperature in the whole pH range tested here.
deviation values revealed that the predicted and experimental correlated well (Table 2). The turmeric flour films prepared with the optimal formulation were more resistant (17.99 MPa) than achira flour films (7.0 MPa) (Andrade-Mahecha et al., 2012) and amaranth flour films of caudatus and cruentus species (1.5e5.4 MPa) (Tapia-Blácido et al., 2007, 2011). However, the elongation was lower (1.78%) than that of films consisting of rice flour and cellulose fibers (4.0%) (Dias, Muller, Larotonda, & Laurindo, 2011), amaranth flour film (Tápia-Blácido et al., 2005, 2011), and achira flour films (22%) (AndradeMahecha et al., 2012). The turmeric flour films had WVP of 0.415 1010 g m1 s1 Pa1. This value is low compared with those of films made from amaranth flour of caudatus and cruentus species (0.8e 3.8 1010 g m1 s1 Pa1) (Tapia-Blácido et al., 2007, 2011), rice flour (0.8e1.1 1010 g m1 s1 Pa1) (Dias et al., 2010, 2011), and achira flour (5.3 1010 g m1 s1 Pa1) (Andrade-Mahecha et al., 2012). In the turmeric flour film, the fibers influence the film properties that depend on the fiberematrix interface; only good fibermatrix adhesion allows the fibers to act as reinforcement agents, increasing film stiffness (Andrade-Mahecha et al., 2012). The length
3.3. Determination of the optimum conditions and experimental validation The models calculated for the tensile strength (TS), solubility (S), water vapor permeability (WVP), and opacity (OP) of the turmeric flour films (Equations ((7), (10), (12) and (13)) furnished the desirability function (G). The minimum and maximum values of each response variable derived from the experimental results obtained in the experimental design (Table 1) gave the gi function by considering these minimum and maximum values. Optimized conditions afforded films with higher resistance to break, low solubility, moderate opacity, and good water vapor barrier property. In other words, optimization culminated in minimized solubility, WVP, and opacity and maximized TS.
2
14:64 þ 2:52X1 2:716X1 2 þ 4:113X2 3:764X2 2 G¼4 16:71 0:3786 þ 0:0727X1 0:1029X1 2 * 0:474
!3
!9
8:99 3:837X1 2 þ 1:667X2 1:857X2 2 þ 2:407X1 X2 * 10:19
10:54 3:805X1 0:825X1 2 þ 1:61X2 3:223X2 2 2:222X1 X2 * 15:55
!9
!3 31=4 5
(14)
The optimized G function furnished T ¼ 86.7 C and pH ¼ 8.5. Turmeric flour films prepared under these process conditions, helped to validate the optimization methodology. We measured and compared the TS, E, S, and WVP of the turmeric flour films with values predicted by Eqs. (7), (8), (10) and (12). The relative
and diameter of the fibers as well as their orientation and distribution in the polymeric matrix can affect the extent to which the fiber and the matrix adhere (Wollerdorfer & Bader, 1998). The solubility of the prepared turmeric flour film was lower (36.32%) as compared with amaranth flour films (42.2%) (Tapia-
Fig. 3. WVP of the turmeric flour films as a function of heating temperature and pH.
Fig. 4. Opacity of turmeric flour films as a function of heating temperature and pH.
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275
Blacido et al., 2007, 2005, 2011), potato peel films (41.2%) (Kang & Min, 2010), and achira flour films (38.3%) (Andrade-Mahecha et al., 2012). The fibers present in the turmeric flour must have incorporated into the matrix more easily suggesting a good degree of fiber-matrix interactions. Indeed, these fibers were spontaneously distributed in the turmeric flour. Such strong interaction between the matrix and the fibers (w65%) meant that the matrix and water interacted less, leading to lower water solubility. The incorporation of cellulose nanocrystals (CNCs) in the plasticized matrix of cassava starch biocomposites decreased water solubility (Zainuddin et al., 2013). Müller, Laurindo, and Yamashita (2009) also found that solubility decreased in cassava starch films with increasing amount of fibers (cellulose). 3.4. Optimized turmeric flour films microstruture
Fig. 5. SEM micrographs of turmeric flour films obtained in the optimized process conditions. (a) 500 (b) 1500 magnification.
Fig. 5(a, b) depict the turmeric flour films microstructure as analyzed by SEM at 500 and 1500 magnification. The micrographs show the surface and cross-sectional area of the films; the surface area corresponds to surface drying. The turmeric flour film had rougher surface, with waves, which affected film thickness (Fig. 5a). The micrograph of the cross-section area revealed a non- homogeneous structure with some denser regions and other regions containing cracks (Fig. 5b). This type of structure resulted from the different interactions taking place in the filmogenic matrix (starchestarch, starch-protein, proteine protein, lipidelipid, proteinelipid, and fiberefiber); the presence of lignocellulosic fiber also accounted for this structure. Together these characteristics could explain the low elongation at break achieved for the optimized films as compared with reported starch, protein, or flour films. Therefore, the poor elongation at break obtained in the present study probably stemmed from
Fig. 6. HPLC profile for (A) curcuminoids, (B) the extract from the turmeric pie, and (C) turmeric flour film prepared in the optimized conditions. Peaks relative to bisdemethoxycurcumin (a), demethoxycurcumin (b), and curcumin (c).
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hydrophobic lignin, which prevented strong linkages from forming between the cellulose fibers and starch (Gilfillan, Nguyen, Sopade, & Doherty, 2012). Lignin is a highly reactive thermoplastic polymer it essentially localizes on the fiber surface and covalently binds to cellulose molecules (Kunanopparat, Menut, Morel, & Guilbert, 2008). Meanwhile, the cellulose fibers were well cemented in the continuous phase, because they strongly interacted with the plasticized starch matrix (Avérous, Fringant, & Moro, 2001). 3.5. Antioxidant activity of optimized turmeric flour films Fig. 6(a) illustrates the chromatogram patterns of curcumin, demethoxycurcumin, and bisdesmethoxycurcumin. The peak at approximately 20, 18.5, and 17 min of retention corresponded to curcumin, demethoxycurcumin, and bisdesmethoxycurcumin, respectively. Peaks with similar retention times in the chromatogram of the dye extracted from the turmeric rhizomes (Fig. 6b), confirmed the presence of these specific curcuminoids in the extract. The chromatogram of the turmeric film displayed the same peaks at the same retention times, attesting to the presence of the three curcuminoids (Fig. 6c). Only the intensities of the peaks in the chromatograms were different, a result of the different concentrations of curcuminoids in the samples. The turmeric rhizomes extract contained larger curcumin concentrations (3.741 g L1) as compared with demethoxycurcumin (3.515 g L1) and bisdemethoxycurcumin (3.520 g L1). The bisdemethoxycurcumin, demethoxycurcumin, and curcumin concentrations in the turmeric flour film were 0.0037, 0.0008, and 0.0001 mg.mL1, respectively. Therefore, the process used to extract the dye from turmeric pie removed greater amount curcumin. The turmeric films presented larger bisdemethoxycurcumin and demethoxycurcumin amounts. DPPH analysis of the optimal film plasticized with sorbitol gave 50.8% AA. This value was lower than that obtained for some antioxidants used in the industry, such as butylated hydroxyl anisole (BHA) (94%AA) and ascorbic acid (92%AA) (Yu-Ling, Yang, & Mau, 2008), but it was important considering that the raw material used to prepare the films was a residue. Because turmeric flour films displayed effective antioxidant property, they could be used as active packaging.
50
Water uptake (%)
40 30 20 10 0 0
20
40
60
80
100
120
140
160
180
Time (h) Fig. 7. Behavior of film swelling during conditioning at 95% RH versus time.
3.6. Optimized film water sorption behavior Fig. 7 shows the sorption kinetics of the optimized turmeric flour film. Before 20 h, water uptake was fast, at longer times (>20 h), water absorption slowed down and reached a plateau, where the film achieved equilibrium, with water uptake of 45.4% 4.05. This value was similar to that reported for starchcellulose microfibril composites (Dufresne et al., 2000), but was lower than that reported for wheat starch film (Lu, Weng, & Cao, 2005). Hence, the presence of fibers, protein, and lipids decreased the turmeric flour film water absorption capacity. 4. Conclusion The turmeric dye solvent extraction residue constitutes a promising source to develop active biodegradable films: the turmeric flour film contains residual curcuminoids with effective antioxidant property. The process parameters (heating temperature and pH) used during film formation affect the mechanical properties, solubility, moisture content, water vapor permeability, and opacity of the resulting film. High heating temperature promotes more interactions between the polymers present in the turmeric flour (starchestarch, proteineprotein, proteinelipid, and fiberefiber), furnishing a more resistant polymeric structure with low WVP, moisture content, and opacity. Higher pH values also favor a more mechanically resistant, denser matrix with lower water solubility and water vapor permeability. The presence of lignocellulosic material contributes to enhanced hydrophobicity culminating in less homogenous and less flexible turmeric flour films. The optimal conditions to produce turmeric flour films with good tensile strength, low solubility, low WVP, and low opacity are T ¼ 86.7 C and pH ¼ 8.5. Acknowledgment The authors wish to thank Fundação de Amparo à Pesquisa do Estado de São Paulo (São Paulo Research Support Foundatione FAPESP) and CAPES (Coordenacão de Aperfeicionamento de Pessoal de Nível Superior) for financial support. References Andrade-Mahecha, M. M., Tapia-Blácido, D. R., & Menegalli, F. C. (2012). Development and optimization of biodegradable films based on achira flour. Carbohydrate Polymers, 88(2), 449e458. AOAC. (1997). Official methods of analysis of AOAC International (16th ed.). Washington: Association of Official Analytical Chemists. Arvanitoyannis, I., Nakayama, A., & Aiba, S. (1998). Edible films made from hydroxypropyl starch and gelatin and plasticized by polyols and water. Carbohydrate Polymers, 36(2/3), 105e119. ASTM. (1995). Standard test method for tensile properties of thin plastic sheeting (D882e95) and standard method for water vapor transmission of materials (E 96-95). In Annual book of ASTM standards. Philadelphia: American Society for Testing and Materials. Avérous, L., Fringant, C., & Moro, L. (2001). Plasticized starchecellulose interactions in polysaccharides composites. Polymer, 42(15), 6565e6572. Bligh, E. G., & Dyer, W. J. (1959). A rapid method of total lipid extraction and purification. Canadian Journal of Biochemistry and Physiology, 37, 911e917. Braga, M. E., Leal, P. F., Carvalho, J. E., & Meireles, M. A. (2003). Comparison of yield, composition, and antioxidant activity of turmeric (Curcuma longa L.) extracts obtained using various techniques. Journal of Agriculture Food Chemistry, 51, 6604e6611. Braga, M. E. M., & Meireles, M. A. A. (2007). Accelerated solvent extraction and Fractioned extraction to obtain the Curcuma longa volatile oil and oleoresin. Journal of Food Process Engineering, 30, 501e521. Braga, M. E. M., Moreschi, S. R. M., & Meireles, M. A. A. (2006). Effects of supercritical fluid extraction on Curcuma longa L. and Zingiberofficinale R. starches. Carbohydrate Polymers, 63, 340e346. Derringer, G., & Suich, R. (1980). Simultaneous optimization of several response variable. Journal of Quality Technology, 12(4), 214e219. Dias, A. B., Muller, C. M. O., Larotonda, F. D. S., & Laurindo, J. (2010). Biodegradable films based on rice starch and rice flour. Journal of Cereal Science, 51, 213e219.
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