Characterization of Aloe vera-banana starch composite films reinforced with curcumin-loaded starch nanoparticles

Journal Pre-proof Characterization of Aloe Vera-Banana Starch Composite Films Reinforced with Curcumin-Loaded Starch Nanoparticles Leonardo Nieto-Suaza, Leonardo Acevedo-Guevara, Leidy T. ´ ´ Cristian C. Villa Sanchez, Magda I. Pinzon,

PII:

S2213-3291(19)30102-9

DOI:

https://doi.org/10.1016/j.foostr.2019.100131

Reference:

FOOSTR 100131

To appear in:

Food Structure

Received Date:

26 September 2018

Revised Date:

24 March 2019

Accepted Date:

15 October 2019

´ ´ MI, Villa Please cite this article as: Nieto-Suaza L, Acevedo-Guevara L, Sanchez LT, Pinzon CC, Characterization of Aloe Vera-Banana Starch Composite Films Reinforced with Curcumin-Loaded Starch Nanoparticles, Food Structure (2019), doi: https://doi.org/10.1016/j.foostr.2019.100131

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Characterization of Aloe Vera-Banana Starch Composite Films Reinforced with CurcuminLoaded Starch Nanoparticles

Leonardo Nieto-Suaza1†, Leonardo Acevedo-Guevara1†, Leidy T. Sánchez2, Magda I.

Programa de Química, Facultad de Ciencias Básicas y Tecnologías, Universidad del

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1.

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Pinzón2, Cristian C. Villa1*

Quindío. Armenia, Quindío, Colombia.

Programa de Ingeniería de Alimentos, Facultad de Ciencias Agroindustriales,

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2.

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Both authors contributed equally to this study

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†

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Universidad del Quindío. Armenia, Quindío, Colombia.

* Corresponding author: Carrera 15 Calle 12 Norte, Universidad del Quindío. Armenia, Quindío, Colombia.

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Cristian C. Villa: [email protected]

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Graphical abstract

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Films made from starch, Aloe Vera and curcumin loaded starch nanoparticles were studied Inclusion of curcumin loaded starch nanoparticles reduces water vapor permeability Curcumin release from the composite films is favored in non-polar solvents

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Highlights

Abstract

Interest in developing biodegradable composite films that can incorporate bioactive

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substances and have and active role in food packaging, has been growing in the last decades. Curcumin, known for its antimicrobial and antioxidant activity has been proposed as an active molecule that can be incorporated into biodegradable films. This work proposes the development and characterization of composite films made from banana starch and Aloe Vera gel incorporated with curcumin-loaded native and acetylated starch nanoparticles. The effect of the curcumin-loaded nanovehicles in the mechanical, barrier, and thermal properties

of the composite films was studied. In this sense, the study noted that inclusion of highly hydrophobic curcumin leads to a reduction of the film’s water vapor permeability while enhancing the film’s tensile strength. Finally, this paper reports the release profiles of curcumin from the composite film in different food simulants, observing that it is possible to control curcumin release in different foodstuffs by changing the characteristics of the

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nanovehicles incorporated.

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Keywords: Composite films, Curcumin, Starch nanoparticles, Aloe Vera

1. Introduction One of the most interesting trends in both food and materials sciences has been the development of new packaging materials by using biodegradable sources. Composite biodegradable films are defined as thin layers made of edible materials first molded as solid sheets and then applied as a wrapping on the food product (Falguera, Quintero, Jiménez,

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Muñoz, & Ibarz, 2011; McHugh, 2000). Edible films can be made from a vast array of materials, which include proteins, lipids, gums, and other carbohydrate polymers, like starch,

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chitosan, and alginate. Starch films have shown great potential applications, given that they

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are odorless, tasteless, colorless, nontoxic, as well as semipermeable to moisture, gases (carbon dioxide and oxygen), and flavor components (Jiménez, Fabra, Talens, & Chiralt,

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2012).

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One way to improve the barrier properties of starch films is through chemical modifications or the formation of composites with more hydrophobic compounds, like chitosan or lipid compounds (Ashori & Bahrami, 2014; Lopez et al., 2014; Silva-Pereira,

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Teixeira, Pereira-Júnior, & Stefani, 2015; Xu, Kim, Hanna, & Nag, 2005). Additionally, several authors have proposed using different nanosystems, like cellulose nanocrystals (Pereira et al., 2017; Slavutsky & Bertuzzi, 2014) and metallic and oxide nanoparticles (Ji,

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Liu, Zhang, Xiong, & Sun, 2016; Ortega, Giannuzzi, Arce, & García, 2017; Sun, Xi, Li, & Xiong, 2014; Yoksan & Chirachanchai, 2010). Recently, development of starch-based nanomaterials (nanoparticles and nanocrystals) has opened new possibilities in reinforcing biodegradable films due to their biodegradability, biocompatibility, and relative easy formation (Collazo-Bigliardi, Ortega-Toro, & Chiralt, 2018; Le Corre, Bras, & Dufresne, 2010; Rodríguez et al., 2018; Santana et al., 2018), as for example, corn starch nanocrystals

have been used to improve both mechanical and barrier properties of pea starch films (X. Li et al., 2015); and both corn and taro starch nanoparticles have been used to reinforce corn starch films (Dai, Qiu, Xiong, & Sun, 2015; Liu et al., 2016); among others (Jiang, Liu, Wang, Xiong, & Sun, 2016; X. Ma, Jian, Chang, & Yu, 2008). In all cases, the use of starch nanoparticles has shown to improve either mechanical or barrier properties of the starch-

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based edible films. Another interesting aspect of starch-based nanosystems is their capability to

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encapsulate different bioactive substances, like caffeine, 5-fluorouracil, testosterone,

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ciprofloxacin, and curcumin (Athira & Jyothi, 2015; Chin, Mohd Yazid, & Pang, 2014; Mahmoudi Najafi, Baghaie, & Ashori, 2016; Santander-Ortega et al., 2010; Xiao et al.,

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2012). We recently reported that native and acetylated banana starch nanoparticles can be used in the encapsulation and controlled gastric release of curcumin because banana is known

Villa, 2018)

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for its resistance to acid hydrolysis.(Acevedo-Guevara, Nieto-Suaza, Sanchez, Pinzon, &

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In recent years, the addition of Aloe Vera (AV) gel to edible films has been studied as a potential way of extending the shelf life of different fruits and vegetables (Benítez, Achaerandio, Pujolà, & Sepulcre, 2015; Gutiérrez & Álvarez, 2016; Gutiérrez & González,

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2017; Ortega-Toro, Collazo-Bigliardi, Roselló, Santamarina, & Chiralt, 2017; Pinzon, Garcia, & Villa; M. Serrano et al., 2017). The results of these studies indicate that including AV gel in the edible films or coatings reduces respiration rates, ethylene productions, weight loss, and softening, while maintaining other parameters, like color and firmness, and reducing fungal growth (Benítez et al., 2015; Chauhan et al., 2015; Chen, Wang, & Weng, 2010; Guillén et al., 2013; Hassanpour, 2015; Khoshgozaran-Abras, Azizi, Hamidy, &

Bagheripoor-Fallah, 2012; Martínez-Romero et al., 2013; Mohebbi, Hasanpour, Ansarifar, & Amiryousefi, 2014; Ortega-Toro et al., 2017; María Serrano et al., 2006; Sogvar, Koushesh Saba, & Emamifar, 2016; Valverde et al., 2005; Vieira et al., 2016). It has been reported that AV gel comprises approximately 99.5% water and 0.5% solids, including polysaccharides (mainly cellulose, hemicellulose, glucomannan, and mannose derivate), vitamins, minerals, enzymes, organic acids, and phenolic compounds (Benítez et al., 2015; Boudreau & Beland,

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2006; Hamman, 2008). For years, AV has been used for medicinal purposes as an anti-

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inflammatory agent and in the treatment of skin burns, frostbite, and psoriasis, among others (Khoshgozaran-Abras et al., 2012; Wani, Hasan, & Malik, 2010). While many of its

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components, such as glycoproteins, barbaloin, emodin, acemannan, aloesin and β-sitosterol

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or diethylhexylphthalate. On the other hand, the antimicrobial and anti-inflammatory effect of AV gel has been well established (Nejatzadeh-Barandozi, 2013; Ortega-Toro et al., 2017).

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This work studied the effect of curcumin-loaded native and acetylated banana starch nanoparticles on the mechanical, optical, and barrier properties of AV gel-banana starch

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composite films and the curcumin release profiles in several food simulants media, in order to fully understand their potential application in active food packaging. 2. Materials and Methods

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2.1 Materials

Green bananas (Musa paradisiaca L.), known in Colombian as ‘platano guayabo’,

were provided by FEDEPLATANO from their crop in La Tebaida, Colombia. Curcumin (analytical grade) was purchased from Sigma. Food-grade glycerol was purchased from (Tecnas, Colombia) and AV gel was obtained from AV leaves purchased at local markets in

Armenia, Colombia. All other reagents used in this study were analytical grade and purchased from Sigma. 2.2 Banana starch and AV gel isolation Green banana starch was isolated according to the procedure described by (EspinosaSolis, Jane, & Bello-Perez, 2009) with some modifications. In brief, samples were peeled

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and cut into small slices (around 2 cm) and washed with a citric acid solution (2% w/v) in a

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2:1 mass rate, then, they were blended for 2 min. The resulting solid was then sieved, washed through screens (20, 40, and 60 US mesh) until wash water was free from solutes and

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suspended solids. The solution was left to decant during 8 h. After decantation, the starch sediments were dried in a Digitronic J.P. Selecta hot air oven at 40 °C during 48 h. The solids

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were ground with a pestle and passed through a sieve (100 US mesh) and placed into a sealed

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container and stored at room temperature until required. Acetylated banana starch was synthetized according to our previous report (Acevedo-Guevara et al., 2018) and the degree of substitution was determined according to previously reported methods (Mahmoudi Najafi

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et al., 2016) and calculated at 0.33.

Aloe Vera leaves were carefully washed with water and dried with a paper towel. Thereafter, the outer green skin layer was removed with a knife. The resulting AV

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parenchyma (AV gel) were washed with distilled water (40 °C), dried by using paper towels, and blended during 3 min; thereafter, it was filtered by using a cheesecloth in a vacuum. The resulting AV gel was refrigerated at 4°C until further uses. 2.3 Preparation of native and acetylated banana starch nanoparticles

Native green banana starch (NSNp) and acetylated banana starch (ASNp) nanoparticles were synthetized according to previous reports (Tan et al., 2009) with some modifications (Acevedo-Guevara et al., 2018). 5 g of either native or acetylated banana starch were mixed with 100 mL of acetone during 15 min by using a magnetic stirrer at 600 rpm. 250 mL of water were added drop by drop (~1 mL/mim) with constant stirring. The resulting suspension was stirred at room temperature until the acetone was completely vaporized. All experiments

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were carried out at 25 °C. Finally, nanoparticles were separated by centrifugation at 4000

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rpm during 40 min and dried in a Digitronic J.P. Selecta hot air oven at 30 °C during 48 h.

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A similar approach was used to prepare curcumin-loaded native (cur-NSNp) and acetylated (cur-ASNp) banana starch nanoparticles. 5 g of starch were dispersed in 100 mL

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a curcumin-acetone solution (0.2 mg/mL) with magnetic stirring (600 rpm) during 30 minutes. Then 250 mL of water were added drop by drop (~1 mL/mim) with constant stirring

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(600 rpm). The resulting suspension was stirred at room temperature until the acetone was completely vaporized. Nanoparticles were separated by centrifugation at 4000 rpm during 40

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min; samples were washed several times with ethanol to remove any excess of curcumin in the Cur-NSNp and Cur-ASNp surface. Finally, the curcumin-loaded nanoparticles were dried in hot air oven at 30 °C during 48 h.

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2.3 Preparation of composite films Appropriate amounts of banana starch and glycerol were mixed with the AV gel

solution. This suspension was heated on a hot plate at 80 °C with constant stirring during 45 min to accomplish complete gelatinization. When needed, an appropriate amount of curNSNp or cur-ASNp was added. The filmogenic solution was homogenized with magnetic stirring (1200 rpm) during 30 min. Finally, approximately 20 g of the suspension was cast

onto Petri dishes (diameter 8.1 cm); dried in a hot air oven at 25 °C until constant weight (approx. 19 h). Films were removed from the Petri dishes and stored at controlled temperature (25 °C) and humidity (60%). All films had a final composition of 50% (w/w) AV Gel, 3% (w/w) banana starch, 1.5% (w/w) glycerol. Three different concentrations of cur-NSNp and cur-ASNp were used: 0.01%, 0.05%, and 0.1% (w/w).

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2.3 Characterization of the native and acetylated starch nanoparticles

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Mean particle size and polydispersity index (PdI) of the native and acetylated banana starch nanoparticles in aqueous solution were measured by dynamic light scattering using a

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Mastersizer 2000 (Malvern) system. Both loading efficiency (%LE) and loading capacity (LC) of curcumin in both NSNp and ASNp were calculated as previously reported by

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐸𝑛𝑐𝑎𝑝𝑠𝑢𝑙𝑎𝑡𝑒𝑑 𝐶𝑢𝑟 𝑇𝑜𝑡𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐶𝑢𝑟

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%LE =

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Acevedo-Guevara et al. (2018) by using equations 1 and 2

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐸𝑛𝑐𝑎𝑝𝑠𝑢𝑙𝑎𝑡𝑒𝑑 𝐶𝑢𝑟 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑁𝑎𝑛𝑜𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠

Eq. 2

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𝐿𝐶 =

x 100 Eq. 1

2.4 Characterization of composite films Film thickness was measured by using a Fowler electronic micrometer (0 - 25.4 mm)

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with 0.2 µm precision. In order to assure a representative value of the composite films thickness, ten measurements were taken in random locations of each film and the mean value was reported. All measurements were made in triplicate. Water vapor permeability (WVP) analyses were performed according to the ASTM E96-05 method. Film solubility (FS) in water was measured by using the method described by R. Shi et al. (2007) with some modifications. Portions of 2 x 2 cm of each film were kept

in a desiccator containing concentrated sulfuric acid until constant weight, and then submerged in water with constant stirring at 25 and 95 °C. After 6 h, the film portions were taken out and dried at 105 °C until constant weight. Mechanical properties of the composite films were measured by using a TA-XT Plus Stable Microsytems Texturometer (Stable Microsystems, Surrey, United Kingdom) with a

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tension grip system A/TG. Film samples were cut (2 x 7 cm). Tensile Strength (TS; MPa) and elongation at break (% E) values were obtained. A 50-mm initial grip and a test speed of

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5 mm/s were used. Ten measurements were carried out for each composite film composition.

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Structural analyses of the composite films were performed using X-ray diffraction and FTIR. X-ray diffraction patterns were obtained using a Bruker D8 Advance diffractometer

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(Bruker, Billerica, United States) with a Cu source, operating at room temperature.

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Rectangular samples were analyzed from 2 = 5° to 2 = 60°, with a 0.01°/s step velocity. Optical and color properties of the composite films were studied by measuring film

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transparency and film color. Color was measured by using a HunterLab ColorQuest XE colorimeter (Hunterlab, Virginia, United States) with D65 illuminant and 10° observer angle. CIE L*, a* and b* parameters were obtained. Total color difference was calculated by using

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equation 3:

∆𝐸 = √(∆𝐿∗ )2 + (∆𝑎∗ )2 + (∆𝑏 ∗ )2

Eq. 3

Film opacity (FO) was measured by using a UV-vis spectrophotometer Hewlett

Packard, HP-8453, (Agilent, Santa Clara, United States). Films were cut into rectangular shape (2 x 7 cm) and attached to the spectrophotometer cuvette and absorbance at 600 nm

was recorded; an empty cuvette was used as reference. Film opacity was calculated by using Equation 4, as reported by Han and Floros (1997). 𝐹𝑂 = 𝐴600 ⁄𝑋

Eq. 4

Where A600 is absorbance at 600 nm and X is film thickness (mm). Thermogravimetric analysis (TGA) and first derivate TGA (DTGA) were performed

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in a TG 209 Iris-Netzsch equipment (Netzsch, Brasilia, Brazil). Samples (2-5 mg) were

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heated from 25 to 600 °C at a 10 °C/min rate under a N2 atmosphere (20 mL/min). 2.5 Curcumin release studies

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Curcumin release from the composite films to different food simulants was studied

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according to the method proposed by Cano, Cháfer, Chiralt, and González-Martínez (2016) and adapted from the current European regulation ("Commission Regulation No 10/2011 of

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14 January 2011 on plastic materials and articles intended to come into contact with food.," 2011). Four food simulants were used; simulant A (ethanol 10% v/v); simulant B (acetic acid

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(3% w/v); simulant D1 (ethanol 50% v/v); simulant D2 (oleic acid as a vegetable oil). Rectangular samples of 6 cm2 were immersed in a glass tube with 20 mL of the food simulant and kept at 20 °C during 7 days. Simulant samples were removed at different times and the curcumin released was quantified using a UV-vis spectrophotometer (Hewlett Packard, HP-

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8453). Samples were diluted using ethanol and quantification was used with a curcumin calibration curve. Curcumin release was expressed as percentage of released curcumin (% R Cur).

2.7 Statistical analysis

All experiments were carried out in triplicate and results were analyzed by multifactor analysis of variance (ANOVA) with 95% significance level using Statgraphics®Plus 5.1. Multiple comparisons were performed through 95% least significant difference (LSD) intervals. 3. Results and Discussion

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3.1 Native and acetylated nanoparticles characterization

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The mean particle size and dispersity index of all the nanoparticles systems studied are shown in Table 1. ASNps showed a bigger mean particle size than their native counterpart

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with diameters of 198  14 nm and 141  12 nm respectably. It has been reported that starch

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acetylation leads to bigger granule sizes due the increase in intermolecular hydrogen bonds between starch particles and even some water molecules, leading to a slight aggregation of

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the particles.(Colussi et al., 2014; González & Pérez, 2002; Sha et al., 2012; Singh, Chawla, & Singh, 2004) A similar trend was observed for the curcumin loaded nanoparticles.

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Furthermore, dispersity index for all nanosystems correspond with a narrow particle distribution. Finally, Table 1 shows that ASNps have a higher loading efficiency and loading capacity than their native counterpart, a behavior that has been previously attributed to the lower polarity of the acetylated starch nanoparticles and more presence of the oxygen atoms

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allowing a stronger hydrogen bond interaction between curcumin and the acetylated starch nanoparticles. This behavior has also been observed in the encapsulation of β-carotene into acetylated β-glucans, showing that increasing hydrophobicity of the carrier can increase encapsulation efficiency of hydrophobic molecules. (Y. Ma, Liu, Ye, & Zhao, 2016) 3.1 Mechanical, barrier, and solubility properties

Table 2 shows the effect of cur-NSNp and cur-ASNp concentration in the mechanical (Elongation at break, %E, and tensile strength, TS) of the banana starch films. As shown in that table, as nanoparticle concentration increased, TS values also increased from 3.74±0.21 MPa in films without nanoparticles to 5.01 ± 0.12 MPa and 4.80 ± 0.21 MPa at the highest concentration of cur-NSNp and cur-ASNp, respectively. Enhancement of TS values of starch films by the inclusion of nanosystems has been explained as an effect of the stronger filler-

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matrix interaction caused by the high specific surface area of the nanoparticles (Dai et al.,

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2015). Due to their small size, starch nanoparticles have high presence of hydroxyl groups in their surface, allowing the formation of more hydrogen bonds with the polymeric matrix. The

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strong interaction between the nanoparticles and the polymeric matrix allows the transfer of

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stress from the matrix to the nanoparticles that carries the load and enhances the film´s strength (Dai et al., 2015; Wetzel, Haupert, & Qiu Zhang, 2003). On the other hand, lower

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TS values observed in the films reinforced with cur-ASNp can be attributed to the starch´s acetylation as it reduces the presence of hydroxyl groups on the nanoparticle surface, leading

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to the formation of fewer hydrogen bonds, thus, a weaker interaction with the polymeric matrix was expected. Table 2 also shows that as the nanoparticles concentration was increased, %E values decreased from 56.3 ± 1.1 in the films without added nanoparticles to 45.4 ± 1.2 and 46.1 ± 1.3 at the highest concentration of cur-NSNp and cur-ASNp,

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respectively. It is known that inclusion of nanoparticles in polymeric matrices increases the films´ TS values and reduces their %E (Dai et al., 2015). This behavior has been attributed to the rigid nature of the nanoparticles that limits the deformation of the composite films. It is important to note that %E values for cur-NSNp and cur-ASNp did not show a significant difference (p <0.05), indicating that acetylation does not affect the rigidity of the starch nanoparticle.

As mentioned, starch films have high permeability to moisture, restricting their application in the food industry, thus, most research focuses on achieving lower water permeability values (WPV). Table 2 shows the WPV of the banana starch composite films as cur-NSNp and cur-ASNp concentrations increased. Several aspects can be used to explain those results. Firstly, it has been reported that the strong interaction between the nanosystems and the polymeric matrix increases the film compactness, making it difficult for water

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molecules to cross through the polymeric matrix. (A.-m. Shi, Wang, Li, & Adhikari, 2013).

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Furthermore, it is known that inclusion of nanoparticles in composite films can lead to a more difficult path for water to go through, reducing WVP considerably (Cui, Kundalwal, &

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Kumar, 2016; Sinha Ray & Okamoto, 2003). Finally, inclusion of highly hydrophobic

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curcumin molecules limits water interaction with the polymeric matrix.(Jing Li, Ye, Lei, & Zhao, 2018) Table 2 shows that at any concentration of curcumin-loaded nanoparticles the

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cur-ASNp films have lower WVP values than the cur-NSNp films. We reported that curASNp have a larger loading capacity than cur-NSNp, indicating that even though

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nanoparticle concentration is the same, films with cur-ASNp have a higher curcumin concentration, making them more hydrophobic, thereby, reducing their WVP with their curNSNp counterpart. The hydrophobic nature of curcumin is also reflected in the films’ water solubility (WS). As shown in Table 2, WS decreased as the curcumin-loaded nanoparticle

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concentration increased, both at 25 and 90 °C. Due to their low WS, curcumin molecules would remain serving as a bridge for the starch molecules, hindering their release into a water medium.

3.2 Color and transparency The effect of inclusion of curcumin-loaded starch nanoparticles on CIE L* a* b* parameters of the edible composites is shown in Table 3. Both edible composites with cur-

NSNp and cur-ASNp displayed the same behavior, increasing L* and b* values as nanoparticle concentration increased. In addition, a* values decreased with the inclusion of more curcumin-loaded nanoparticles. Curcumin has a natural yellow-orange color that would have a high positive b* value with low negative a* value. Inclusion of curcumin-loaded nanoparticles leads to composites with a more intense orange color. Composites with curASNp had higher b* and lower a* values than their cur-NSNp counterparts, indicating a more

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intense orange color. Table 3 also shows the total color difference (E) of the composite

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films as the curcumin-loaded nanoparticle concentration increased. As shown in Table 3, E values increased considerably as curcumin concentration increased, a behavior that can be

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attributed to changes of the L*, a*, and b* parameters, explained previously. Finally, Table

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3 shows that film opacity (FO) values increased as the curcumin-loaded nanoparticle concentration increased, indicating that inclusion of nanoparticles reduces film transparency

3.3 Structural analysis

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due to the increasing solid content in the filmogenic solution.

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Figure 1 shows the XRD patterns of curcumin, cur-NSNp, cur-ASNp, and composite films at whit and without nanoparticles addition. As explained in a previous work (AcevedoGuevara et al., 2018), the curcumin XRD diffraction pattern (Figure 1a) shows peaks at 8.84, 12.10, 14.39, 17.20, 23.33, 24.50, 25.52, and 28.87°, attributed to its highly crystalline

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structure (Gómez-Mascaraque, Lagarón, & López-Rubio, 2015; Jinglei Li, Shin, Lee, Chen, & Park, 2016; Teng, Luo, & Wang, 2012). The XRD patterns for cur-ASNp and cur-NSNp (Figures 1b and 1c) showed none of the curcumin characteristic peaks, indicating that once encapsulated, curcumin exists in an amorphous rather than a crystalline state. Regarding the composite films, Figure 1d shows the XRD pattern for films without addition of curcumin-

loaded nanoparticles, while Figures 1e and 1f show the XRD pattern for composite films with 0.1% of cur-NSNp and cur-ASNp, respectively. All the films studied showed an intense peak at 16° and a smaller peak at 15°. Neither of these two peaks can be attributed to curcumin crystals, indicating that curcumin-loaded nanoparticles are fully dispersed in the film and curcumin molecules continue in an amorphous state. It has been reported that starch films obtained through the casting method show higher crystallinity than films formed by other

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methods due to longer drying times that lead to amylose crystallization (Ortega-Toro,

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Jiménez, Talens, & Chiralt, 2014; Ortega-Toro et al., 2016). Ortega-Toro et al. (2017) reported that inclusion of AV gel has no significant effect on the starch film’s crystallinity,

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3.4 Thermal analysis

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Given that composite films have a wide range of applications in the food, cosmetic, and pharmaceutical industries, it is important to study their thermal stability across extensive

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temperature ranges. Figure 2A shows the TGA curves of the banana starch-AV gel composite films with different curcumin-loaded nanoparticles. All composite films displayed three

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decomposition stages; the first was around 105 °C and can be attributed to water evaporation from the composite films. The second decomposition stage was between 180 and 250 °C and the third was above 250 °C, resulting from the complex degradation of the amylose and amylopectin, including dehydration of saccharide rings. To fully understand the thermal

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behavior of the different composite films studied, first derivate TGA curves were calculated and are shown in Figure 2B. All the composite films showed three peaks at 70, 201, and 300 °C, corresponding to the thermal decomposition stages mentioned. Nevertheless, it is important to notice that in composite films including cur-ASNp the second peak is more intense than in the other films. These results may be attributed to the depolymerization and

decomposition process of the acetylated and deacetylated groups in the modified starch nanoparticles. 3.5 Curcumin release in food simulants One of the most important aspects in developing composite films incorporated with bioactive molecules is to understand the migration of the molecules from the film to the different kinds of foodstuffs. Two kinds of simulants were used, according to European

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Union regulations. Simulants A and B are meant to simulate highly hydrophilic foods with

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the capability to extract hydrophilic substances. Simulants D1 and D2 are meant to simulate highly lipophilic foods. Figures 3A and 3B show the curcumin release (% R Cur) profiles

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from composite films with cur-NSNp and cur-ASNp, respectively. Curcumin molecules were

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released from the composite films in all four simulant media; nevertheless, there were different % R Cur values (Table 4). Curcumin is a highly hydrophobic molecule; thus, as

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expected, % R Cur values in simulants A and B were very low, reaching values under 9% after 168 h without significant difference between both types of curcumin-loaded

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nanoparticles. A different situation occurs in simulants D1 and D2 in which the lipophilic nature of curcumin molecules allowed higher release values, as for example after 168 h, % R Cur values reached 38.2% and 32.2% for films incorporated with cur-NSNp and cur-ASNp in simulant D1 and 57.1% and 47.2% in simulant D2, respectively. The difference in % R

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Cur values for cur-NSNp and cur-ASNp composite films in both simulants can be explained as follows: in our previous work (Acevedo-Guevara et al., 2018) we demonstrated that curcumin molecules sensed a lower polarity environment when encapsulated in acetylated banana starch nanoparticles than in native banana starch nanoparticles due to the replacement of hydroxyl groups with the less polar hydrogen bond donor acetyl groups, allowing higher encapsulation values and lower release values in simulated gastric fluids. Given the higher

lipophilic environment of the ASNp, it is more difficult for simulants D1 and D2 to extract curcumin molecules from the composite films than from the films incorporated with the more hydrophilic NSNp. It is important to notice, that to the best of our knowledge, there is no regulation on the amount of curcumin that can migrate from a packaging material to the foodstuff. 4. Conclusion

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This paper reports the formation and characterization of composite films from banana

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starch, AV gel, and curcumin-loaded native and acetylated starch nanoparticles. Several properties of the composite films can be enhanced by adding curcumin-loaded nanoparticles,

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like reducing their WVP due to the hydrophobic nature of the curcumin molecules. The

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mechanical properties of the composite films are also affected by inclusion of nanoparticles, reducing their elongation at break values while enhancing their tensile strength due to the

lP

force distribution between the composite films and the nanoparticles. Finally, we observed that the curcumin released from the composite films in different food simulants is favored in

ur na

lipophilic substances and can be controlled by reducing the polarity of the starch nanovehicle by acetylation.

5. Acknowledgments

The authors want to thank the Vicerrectoria de Investigaciones, Facultad de Ciencias

Jo

Básicas y Tecnologías, Facultad de Ciencias Agropecuarias, Programa de Química, Programa de Ingeniería de Alimentos and FEDEPLATANO for their support.

6. Conflict of Interest None.

References

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of

ro

-p

re

lP

ur na

Jo

f)

e)

-p

ro

c)

of

Intensity (U.A)

d)

5

lP

re

b)

10

15

20

25

30

a)

35

40

ur na

2

Figure 1. X-Ray diffraction patterns (XRD) of a) curcumin; b) cur-ASNps; c) cur-NSNps; d) banana starch-AV gel film; e) cur-ASNps (0.1%)-banana starch-AV gel edible film; f)

Jo

cur-NSNps (0.1%)-banana starch-AV gel edible film.

of 0,0

100

DTG (mg/°C)

-0,2

-p

60

40

re

Weight loss (%)

80

ro

Film whitout SNps cur-NSNps 0,01% cur-NSNps 0,1% cur-ASNps 0,01 cur-ASNps 0,1%

20

0 100

200

300

lP

A 400

500

600

ur na

Temperature (°C)

-0,4

-0,6 Films whitout SNPs cur-NSNPs 0,01% cur-NSNPs 0,1% cur-ASNps 0,01% cur-ASNps 0,1%

-0,8

B -1,0

100

200

300

400

500

Temperature (°C)

Jo

Figure 2. TGA (A) and DTGA (B) curves of banana starch-AV gel and curcumin-loaded native (cur-NSNps) and acetylated (cur-ASNPs) composite films.

70

A

60

% R Cur

50

40

30

of

20

0 0

20

40

60

80

100

120

160

re

70

B

lP

60

50

40

ur na

% R Cur

140

-p

Time (h)

ro

10

30

20

10

0

Jo

0

20

40

60

80

100

120

140

160

Time (h)

Figure 3. Curcumin release from composite films incorporated with A) cur-NSNps and B) cur-ASNps in different food simulants: (■) A; (▲) B; () D1, and (▼) D2.

27

PdI

LE (%)

141  12a

0.311  0.012ª

ASNp

198  14b

0.216  0.025c

Cur-NSNp

168 12a

0.356  0.014a

Cur-ASNp

210  11b

-

-

-

-

82.23  2.1ª

2.12  0.03a

92.12  2.3b

3.41  0.02b

lP

re

NSNp

-p

(nm)

ur na

0.235  0.033c

LC (mg/mg)

ro

Mean particle size

of

Table 1. Mean particle size, dispersity index (DI), loading efficiency and loading capacity of the different nanoparticles systems.

Jo

Means with different superscripts are significantly different in their respective column (p <0.05)

28

of

ro

Table 2. Mechanical, barrier, and water solubility properties of the composite films at different curcumin-loaded nanoparticle concentrations. Thickness (µm)

E (%)

56.3 ± 1.1a

3.74 ± 0.21a

lP

96.2 ± 2.2a

re

Nanoparticles 0

WVP x 109

TS (MPa)

-p

%

53.2 ± 1.4b

4.55 ± 0.33b

0.05

136.1 ± 2.4b

49.6 ± 1.2c

4.92 ± 0.32cd

140.2 ± 1.2c

45.4 ± 1.2d

5.01 ± 0.12e

ur na

130.3 ± 4.3b

112.3 ± 3.1d

Jo

0.01

(g Pa-1 s-1 m-1)

25 °C

95 °C

4.59 ± 0.51a

32.9 ± 1.2a

53.8 ± 1.3a

26.5 ± 0.5b

43.8 ± 0.4b

20.2 ± 1.3c

41.2 ± 1.1b

15.9 ± 0.5d

34.6 ± 0.2c

cur-NSNps

0.01

0.1

WS (%)

3.98 ± 0.32b 3.72 ± 0.23b 3.12 ± 0.12c

cur-ASNps

51.7 ± 1.1c

4.07 ± 0.51bc

3.15 ± 0.12c

20.1 ± 0.2c

38.9 ± 1.2d

0.05

135.5 ± 2.3b

48.7 ± 1.2c

4.48 ± 0.33f

2.89 ± 0.23c

18.4 ± 0.3e

33.2 ± 0.2c

0.1

140.4 ± 1.1c

46.1 ± 1.3d

4.80 ± 0.21e

2.12 ± 0.32d

11.8 ± 1.1f

29.1 ± 0.8e

Means with different superscripts are significantly different in their respective column (p <0.05)

29

Table 3. CIE L* a* b* parameters and film opacity (FO) of the composite films at different curcumin-loaded nanoparticle concentrations. L*

a*

b*

E

FO

37.7 ± 0.2a

0.08 ± 0.02a

-0.70 ± 0.11a

-

13.42± 0.12a

% Nanoparticles 0

of

cur-NSNps -0.24 ± 0.12b

0.91 ± 0.12a

10.82 ± 0.09a

18.47 ± 0.1b

0.05

48.9 ± 0.2b

-1.07 ± 0.21c

2.75 ± 0.22b

11.77 ± 0.23a

19.02 ± 0.13c

0.1

50.1 ± 0.3c

-1.17 ± 0.18c

3.93 ± 0.11c

13.29 ± 0.12b

23.46 ± 0.14d

2.02 ± 0.11d

10.59 ± 0.12a

12.45 ± 0.12e

5.42 ± 0.22e

12.61 ± 0.15c

17.23 ± 0.15f

9.18 ± 0.31f

15.39 ± 0.21d

21.39 ± 0.12g

-p

ro

48.4 ± 0.5b

re

0.01

cur-ASNps 47.9 ± 0.1b

-0.79 ± 0.21d

0.05

48.5 ± 0.4b

-2.17 ± 0.17e

0.1

49.1 ± 0.1bc

-2.93 ± 0.11f

lP

0.01

Jo

ur na

Means with different superscripts are significantly different in their respective column (p <0.05)

30