orange oil antimicrobial emulsion films

Journal Pre-proof Characterization of curcumin incorporated guar gum/orange oil antimicrobial emulsion films

Ayca Aydogdu, Clayton J. Radke, Semih Bezci, Emrah Kirtil PII:

S0141-8130(19)38306-0

DOI:

https://doi.org/10.1016/j.ijbiomac.2019.12.255

Reference:

BIOMAC 14283

To appear in:

International Journal of Biological Macromolecules

Received date:

15 October 2019

Revised date:

23 December 2019

Accepted date:

28 December 2019

Please cite this article as: A. Aydogdu, C.J. Radke, S. Bezci, et al., Characterization of curcumin incorporated guar gum/orange oil antimicrobial emulsion films, International Journal of Biological Macromolecules(2018), https://doi.org/10.1016/ j.ijbiomac.2019.12.255

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2018 Published by Elsevier.

Journal Pre-proof

Characterization of Curcumin Incorporated Guar Gum/Orange Oil Antimicrobial Emulsion Films Ayca Aydogdua,b, Clayton J. Radkea*, Semih Bezcic, Emrah Kirtila,b*

a

Mechanical Engineering Department, University of California Berkeley, 6141 Etcheverry Hall, Berkeley, CA 94720-1462, USA

b

Department of Food Engineering, Middle East Technical University, 06800, Ankara, Turkey

of

Chemical and Biomolecular Engineering Department, University of California Berkeley, 101E Gilman Hall, Berkeley, CA 94720-1462,

na

lP

re

-p

ro

USA

Jo ur

c

*Corresponding Author: Emrah KIRTIL

Phone: +90 312 210 5637

Fax:

+90 312 210 2767

e-mail: [email protected] 1

Journal Pre-proof

Abstract Edible films are manufactured from natural, renewable, nontoxic, and biodegradable polymers and are safe alternatives to plastic food packaging. Despite ongoing research, biopolymer-based edible films still are not at a quality to ensure total commercial replacement of synthetic packaging materials. The study aims to compare the effectiveness of some novel methods employed to improve edible film properties. These include dispersion of orange oil (1% & 2% v/v) and/or curcumin into guar gum (GG), glycerol and lecithin-based edible films that are further reinforced with Sodium

of

trimetaphosphate (STMP) crosslinking with the aim enhancing films physical properties. The films

ro

were characterized by measurement of film thickness, density, moisture content, water dissolvability,

-p

FTIR Spectroscopy, opacity, water vapor permeability, tensile properties, and antimicrobial activity. Orange oil and curcumin preserved their antimicrobial activity inside the films, which bestowed the

re

films with an active packaging function. Control GG films had acceptable tensile and barrier

lP

properties that were further improved. All other film properties, such as opacity, dissolvability, and moisture content, that should be designed for specific application, were successfully modified with the

na

methods used. Our results confirm successful application of STMP crosslinking, emulsion film

Jo ur

formation, and active agent addition to edible films in manufacturing GG films for packaging.

Keywords: Guar gum, biodegradable film, lecithin, antimicrobial film, emulsion film, crosslinking, STMP

2

Journal Pre-proof

1. Introduction Because of rising consumer awareness of possible health and environmental concerns for using plastic food packaging, there is a growing trend in research and development of biopolymer-based edible packages (Gomaa, Hifney, Fawzy, & Abdel-gawad, 2018; Kowalczyk et al., 2016). Edible films are manufactured from natural, renewable, nontoxic, and biodegradable polymers such as proteins, carbohydrates, and lipids (Gomaa et al., 2018). The edible biopolymer-based packages, in addition to possessing all environmentally friendly properties of biodegradable packages, also serve

of

supplementary functions related to their edible nature. These can range between providing increased

ro

convenience during consumption to serving as carriers of active compounds such as antimicrobials,

-p

antioxidants, and texture enhancers, among others (Acevedo-Fani, Salvia-Trujillo, Rojas-Graü, & Martín-Belloso, 2015; Wu et al., 2019). Casings, food wrappers, superficial coatings, layers separating

re

various components in complex food products, water-soluble bags for pre-portioned foods that are not

lP

removed for cooking, microcapsules, and controlled-release systems for food additives and drugs are some of the many specific applications of edible packaging (Aydogdu, Yildiz, Aydogdu, et al., 2019;

na

Kowalczyk et al., 2016).

Jo ur

Despite introducing unique functions to food packaging, edible films lack in some of the basic functions of packaging such as mechanical strength and water barrier properties (Aydogdu, Yildiz, Ayhan, et al., 2019; Azeredo et al., 2017). There are methods to overcome these shortcomings. For example, increasing film hydrophobicity via addition of essential oils into the film matrix retards moisture transfer (Galus, 2018). Typically, essential oils (EOs) are volatile compounds that possess antioxidant and antimicrobial properties (Ghani, Barzegar, Noshad, & Hojjati, 2018; Lee, Kim, & Park, 2018). Incorporation of EOs into the films requires a water-soluble surfactant and energy input to achieve a homogenous distribution of oil particles.We use soy lecithin for emulsion stabilization. Soy lecithin is composed of various amphiphilic phospholipids (≥70% phosphatidylcholine) that quickly adsorb on the oil-water interface. It is a cheap, natural, and widely accepted emulsifier in the food industry (Cha et al., 2019; Okuro, Gomes, Costa, Adame, & Cunha, 2019).

3

Journal Pre-proof Orange oil is chosen here as the EO. It is extracted from citrus/orange peels and is rich in monoterpene hydrocarbons, with the main component being d-limonene (up to 97.3 g in 100 g orange oil). Dlimonene has been shown to possess antimicrobial properties (Aboagye, Banadda, Kiggundu, & Kabenge, 2017; Kotsampasi et al., 2018). By inclusion of essential oils, such as orange oil, into the film matrix, it is possible to use the films as a carrier of oil-soluble functional agents, which would normally not be added into aqueous-based foods as a food ingredient. Consumptions of such edible films, or release of oil-soluble components into the mobile lipid phase of fatty foods can contribute

of

additional nutritional benefits as well as providing the food with protection against oxidative rancidity and microbial spoilage (Acevedo-Fani et al., 2015; Ghani et al., 2018; Q. R. Liu, Wang, Qi, Huang, &

-p

ro

Xiao, 2019).

Curcumin is the product obtained by solvent extraction from turmeric and is widely used as a spice

re

and coloring agent in food due to its yellowish-orange color and pleasant aroma (Khamrai, Banerjee,

lP

Paul, Samanta, & Kundu, 2019; Musso, Salgado, & Mauri, 2017). It has gained increasing recognition related to its unusual biological activities such as antiviral, anti-inflammatory, antimicrobial,

na

antioxidant, anti-HIV, anti-Parkinson, anti-Alzheimer’s, anticancer, and free radical-scavenging activity (Musso et al., 2017; Wang et al., 2019). Hence, curcumin addition to edible films potentially

Jo ur

improves film’s functional properties and nutritional profile.

Guar gum (GG) is a natural, nonionic, hydrophilic carbohydrate polymer, that is extensively used in the food industry as a thickener and stabilizer (Moreira et al., 2012). Guar gum was shown to form homogenous edible films that are almost completely water soluble owing to the large number of hydroxyl groups it carries (Borges, Banegas, Porto, Zornio, & Soldi, 2013). Edible films can be used for different purposes depending on their water solubility. For instance in films used as candy wrappers, high water solubility is preferable, since they easily dissolve and melt in the mouth (Gutiérrez, Guzmán, Medina Jaramillo, & Famá, 2016). Low water soluble films have a wider range of applications. Phosphate crosslinking of GG has been confirmed to decrease its solubility (Borges et al., 2013; Yıldırım-Yalçın, Şeker, & Sadıkoğlu, 2019). Sodium trimetaphosphate (STMP) is a safe, non-toxic, and FDA approved crosslinking agent commonly employed for crosslinking starch in the 4

Journal Pre-proof food industry (Gliko-Kabir, Penhasi, & Rubinstein, 1999; Huang et al., 2019). From GG and STMP, a complex of di-polymer phosphate ester is formed at basic pH. The hydroxyl groups in guar gum molecules attach to the phosphate through a phosphorylation reaction. Crosslinking with STMP has also been shown to increase film hydrophobicity, which results in enhanced functional properties (Huang et al., 2019; Sgorla et al., 2016; Yıldırım-Yalçın et al., 2019).

As in synthetic polymers, addition of property modifiers is essential to achieve desired physical and mechanical characteristics (Choi & Han, 2001). For this purpose, plasticizers are incorporated into the

of

films. Most edible films become too brittle and fragile to stress in absence of plasticizers (Choi & Han,

ro

2001). Plasticizers are low molecular weight and non-volatile substances that reduce cohesive forces

-p

between polymer molecules and increase the mobility of polymer chains which enhances film flexibility (Pelissari, Andrade-Mahecha, Sobral, & Menegalli, 2013b; Zhang & Han, 2006). Glycerol

re

is the most frequently used plasticizer in edible films; and it is employed here as the plasticizer for this

lP

study (Dick et al., 2015).

na

The objective of this research is to prepare non-toxic, edible, biopolymer-based, and active films that can safely be used as a primary or secondary food packaging material and also act as a carrier for oil-

Jo ur

soluble functional food additives. For this purpose, emulsion films were prepared by dispersal of varying amounts of orange oil into guar gum/glycerol film matrices and stabilized with lecithin. Guar gum films were crosslinked with STMP with the objective of improving film physical properties. With orange oil and curcumin integration into the films, edible films with increased health benefits and antimicrobial properties were acquired.

5

Journal Pre-proof

2. Material & Methods 2.1. Materials Guar Gum, glycerol (≥%99), orange oil (natural, cold-compressed, Brazil origin), Curcumin (≥65%, from Curcuma longa (Turmeric), powder form), Sodium trimetaphosphate (STMP, ≥95) was purchased from Sigma-Aldrich Chemie Gmbh (Darmstadt, Germany). Soy lecithin (70% phosphatidylcholine) with the commercial name Lipoid S75 was generously provided by Lipoid

of

GmbH (Ludwigshafen, Germany). NaOH and HCl, purchased from Sigma-Aldrich Chemie Gmbh

ro

(Darmstadt, Germany) were used to adjust the pH of film-forming solutions when necessary.

-p

2.2. Film preparation

re

Aqueous film-forming solutions were prepared by dispersing soy lecithin (1% w/v), guar gum (1.5% w/v) and glycerol (0.6% w/v) in Millipore water by overnight mixing with a magnetic stirrer. For

lP

curcumin containing film solutions, curcumin (0.4% w/v) was dissolved in orange oil by mixing with a magnetic stirrer. Orange oil (1% v/v) was added to the aqueous solutions and mixed with a high-

na

speed mixer (Ultraturrax T25, IKA Co. Ltd., Staufen, Germany) at 5000 rpm. To ensure fine

Jo ur

dispersion of the oil particles, the mechanically mixed dispersions were further homogenized via a probe-type ultrasonic homogenizer (750 W) working at 70% power for 10 min (Branson Digital Sonifier 450, Emersen Electric Co., Missouri, USA) with the sample placed inside an ice bath. The resulting solutions were degassed under vacuum for 20 min to remove bubbles formed during homogenization. 25 ml of film-forming solutions was poured onto disposable Petri dishes and dried for 96 h under ambient conditions. Films were peeled off the Petri dishes and placed inside desiccators adjusted to 50% RH (with saturated NaBr solution). Because the physical properties of the films were strongly affected by moisture content, they were kept inside desiccators until analyzed.

2.3. Experimental Design Upon preliminary trials, optimum guar gum and glycerol concentrations were chosen as 1.5% and 0.6% w/v, respectively. Final film formulations are listed in Table 1. Control films contained only

6

Journal Pre-proof guar gum and glycerol. L1, L2, LC2, and P-L2 films were all emulsion films, prepared by dispersion of orange oil into the film forming solutions and stabilized with lecithin (1% w/v) as emulsifier. L1 and L2 films contained 1 and 2% v/v orange oil. LC2 was prepared with curcumin added orange oil (2% oil v/v with %0.1 w/v curcumin dissolved). P-L2 films (containing 2% orange oil) were phosphate crosslinked via Trisodium trimetaphosphate (STMP).

2.4. Phosphate Crosslinking Phosphate crosslinking of guar gum was performed according to the method identified by Gliko-Kabir

of

et al. (2000). Trisodium trimetaphosphate (STMP) dispersion (30% w/v) was prepared by adding

ro

STMP to Millipore water and mildly stirring for 2 h. Subsequently, STMP dispersions were

-p

homogenized by ultrasonic homogenization for 5 min at 70% power. To decide on the optimum STMP amount for crosslinking, the crosslinking procedure was carried out with increasing amounts of

re

STMP. 1 ml, 5 ml, 8 ml, 10 ml, 20 ml, and 30 ml of aqueous 30% STMP dispersions were added to

lP

five 100 ml guar gum dispersions (previously adjusted to pH 12 by addition of NaOH), giving 0.1, 0.5, 0.8, 1, 2, and 3 equivalents of STMP, respectively, under the assumption that each mole of STMP

na

reacts with three pairs of hydroxyls groups. The reaction mixtures were stirred for an additional 2 h at a maintained pH of 12. Ideal STMP concentration was chosen as as 0.5 equivalent of STMP, which

Jo ur

was the highest concentration that provided fine dispersions with no signs of visible STMP particles. The same procedure was applied to film-forming dispersions containing glycerol, lecithin, and curcumin with the same STMP concentration to obtain films entitled P-L2 (Table 1).

2.5. Film Thickness Thicknesses of the films were measured with a hand-held micrometer (Dial thickness gauge No. 7301, Mitutoyo Co. Ltd., Tokyo, Japan) with 0.01 mm in precision. Measurements were performed on five different locations on each film. Mean thicknesses reported are the average measurement of at least 10 different films.

7

Journal Pre-proof 2.6. Density Square pieces (30x30 mm2) were cut from the films, and the average thickness was determined from three random measurements. The samples were dried in an oven (Isotemp, Fischer Scientific, Pennsylvania, USA) at 50oC for 24 h and subsequently weighed with a precision scale (Mettler AT261 Deltarange, Ohio, USA) with 0.1 mg accuracy. The density was determined as the ratio of the weight to volume (thickness × area) of the films.

of

2.7. Moisture Content Films were dried for 24 h by placing them inside an oven set to 80oC. Moisture content (%, wet basis)

-p

are the initial and final weights of the films, respectively.

2.8. Dissolution in Water

re

and

lP

where

ro

was found from the equation;

na

Square pieces (30x30 mm) were cut from the films and dried in a vacuum oven at 50 oC for 24 h. The weight of the dried pieces was recorded as the initial dry weight (

). The pieces were then

Jo ur

immersed into 30 mL of Millipore water at 25 oC and kept there for 24 h. Then, the undissolved remnants were filtered with Whatman paper #1 and dried at 80oC for 24 h. The weight of dried material was recorded as the final dry weight ( from the equation;

2.9.

). Percentage of the film dissolved was computed

Film Transparency

Light transmittance of the films was measured with a UV–visible spectrophotometer (UV-1700, Shimadzu, Kyoto, Japan). Opacity values were calculated from the method described by Dick et al (2015);

8

Journal Pre-proof where

is the absorbance at 600 nm and

is the film thickness (mm). Greater opacity values

represent lower transparencies of the films. Three pieces were taken from each film for measurement; six replicates were measured for each formulation.

2.10.

Fourier-Transform Infrared (FTIR) Analysis

For the acquisition of FTIR Spectra, square pieces of film samples (20x20 mm2) were dried and measured using an FTIR spectrophotometer (IR-Affinity1, Shimadzu, Kyoto, Japan) in attenuated total reflectance (ATR) mode using a diamond ATR crystal. Infrared spectra were recorded with 32 scans

ro

2.11.

of

over the wavenumber range of 600–4000 cm−1.

Contact Angle

-p

To estimate the wettability of the films, 10-15 μL droplets of Millipore water were deposited on the

re

film surface. Using a contact-angle apparatus (DSA100, KRÜSS GmbH, Hamburg, Germany) a

lP

magnified image of the drop profile was captured and anlyzed for the time-dependent changes in droplet shape. The static water contact angle in the advancing direction was measured between the

na

baseline of the drop and the tangent at the drop boundary. Image processing and curve fitting for contact angle measurement was executed from a theoretical meridian drop profile. Since the films

Jo ur

were highly water-soluble, measurements were performed within the first 10 s of droplet deposition during which contact angles were unchanged.

2.12.

Antimicrobial Activity

Antimicrobial activity was examined using an inhibition zone assay in agar medium as described by Meira et al. (2017). 1-cm diameter pieces were cut and placed on Lysogeny broth (LB) agar plates. Then, 10 ml LB soft agar (7.5 g/l) inoculated with Escherichia coli (indicator for Gr-) or Bacillus subtilis (indicator for Gr+) (107 CFU/ml) was poured onto the agar plates placed on petri dishes and incubated at 37 oC for 24 h to promote microorganism growth. Antimicrobial activity was evidenced by clear zones (no microorganism growth or survival) surrounding film pieces. The diameter of the inhibition zone was measured and reported in mm.

9

Journal Pre-proof To investigate the effect of the films on preserving food quality, fresh strawberries purchased from a local grocery store were placed on films and kept at ambient conditions (25 oC and 40% RH). The berries were photographed every day and visually analyzed for deterioration of fruit quality and possible mold growth.

2.13.

Water vapor permeability (WVP)

To determine the WVP of films, a modified version of ASTM E-96 method was used (Bertuzzi, Castro Vidaurre, Armada, & Gottifredi, 2007). Cylindrical polyacetal (Delrin) custom-built test cups with an

of

internal diameter of 40 mm were filled with 30 ml of distilled water. Films were positioned over the

ro

cups and fixed in place with screws. There was a rubber joint between the film and the open cap to

-p

ensure there was no water vapor leakage around the films. Test cups were placed in pre-equilibrated 15-20% RH desiccator cabinets. RH inside the cups was assumed to be 100% , while the outside %RH

re

and temperature recorded with an digital hydrometer (ThermoPro TP50, USA). A schematic of the

lP

evaporation cups is given in Figure 1. Cups were weighed at least 10 times with at least 2 h breaks between each measurement. Water vapor transmission rates (WVTRs; g m-2 s-1) were established from

where

Jo ur

na

the slope of the weight loss versus time. WVP was calculated from the equation below;

is the partial pressure of water vapor at the inner surface of the film inside the cup (Pa) and

is the partial pressure of the water vapor at the outer surface of the film outside the cup (Pa). Measurements were performed in triplicates.

2.14.

Tensile Properties

Mechanical properties were assessed with a Universal Testing Machine (Z250, Zwick/Roell, Ulm, Germany) at an extension rate of 25 mm/min with a cell load of 1 kN. The film samples were mounted in the film-extension grips with a grip-to-grip separation of 25 mm. The tensile strength at break (TS) and percentage elongation at break (EAB) were computed as follows;

10

Journal Pre-proof ( ) where

is the maximum load for film rupture (N),

is the cross-sectional area of the sample.

represents the initial gage length (25 mm) of the sample and

is the final length of the film before it

breaks (Acevedo-Fani et al., 2015). Young’s modulus is the slope of the initial linear section of the stress-strain curve (J. Liu et al., 2018) and was calculated as;

is a strain of 0.15,

(Mpa) is the stress at

. Five replicates were taken from each film.

(Mpa) is the stress

Statistical Analysis

-p

2.15.

, and

ro

at

is a strain of 0.1,

of

where

re

Statistical analyses were performed using statistical analysis software (Minitab v16.0, Pennsylvania, USA). To compare the means and identify the statistical significance of the variation between different

lP

groups, analysis of variance (ANOVA) with Tukey's multiple comparison test was used. Differences were considered significant for p < 0.05. All data are presented as the mean (of at least three

Jo ur

na

measurements) ± standard deviation.

11

Journal Pre-proof

3. Results & Discussion 3.1. Density and Thickness All film samples exhibited homogenous surfaces with no visible bubbles or cracks. They also had good handling attributes, demonstrated by intact removal from the plates without tearing. This means all formulations were successful in forming films that were not too sticky or brittle. Photos of films are given in Figure 2. Film densities ranged between 0.66±0.02 and 1.05±0.02 g/cm3. The fact that films

of

displayed densities lower than the density of water (despite being aqueous-based) indicates the presence of air-filled pores inside the films. These values lie within the range of other biopolymer

ro

films. Moore et al. (2006) Reported density values between 0.92-1.10 g/cm3 for keratin films, Pelissari

-p

et al. (2013) reported densities between 0.94-1.25 g/cm3 for banana flour films and Singh et al. (2015)

re

found the densities of chitosan films to be around 1.31 g cm-3.

lP

Oil concentration had a strong impact on film densities. 2% oil addition increased the density of films by 48% compared to the control. Density is influenced by internal film structure and is shaped by the

na

composition, molecular weight, and interactions between the components present in the films (Pelissari, Andrade-Mahecha, Sobral, & Menegalli, 2013a). The films were stabilized by soy lecithin.

Jo ur

As oil is incorporated during the homogenization step, amphiphilic phospholipids in lecithin adsorb to the oil/water the interface with phosphate heads lying inside the polymer matrix and hydrophobic fatty acids elongated towards the oil phase (Gibis, Vogt, & Weiss, 2012). This possibly increases the interactions between the polymer chains giving rise to a tighter molecular packing which is reflected as increased densities. Curcumin addition and crosslinking had no significant effect on film densities. The change of polymer chain interactions induced by crosslinking, were not reflected in densities. This suggests that a more extensively bonded network did not necessarily result in a tighter molecular packing in GG films.

Film thicknesses ranged from 0.117 to 0.183 mm (Table 2). This is close to what other researchers report with biopolymer films. Gomaa et al. (2018) found thickness between 0.107 and 0.143

12

Journal Pre-proof mm(Gomaa et al., 2018)(Gomaa et al., 2018)(Gomaa et al., 2018)(Gomaa et al., 2018). Meira et al. (2017) found thicknesses ranging from 0.162 to 0.223 mm in antimicrobial added corn starch films. Lee et al. (2018) found thicknesses between 0.162 and 0.223 mm for clove oil containing chitosanbased films. Dispersion of orange oil into the film matrix and an increase in its concentration, increased film thicknesses, which is in agreement with other emulsion film studies (Lee et al., 2018; Meira et al., 2017). Curcumin addition or crosslinking did not alter film thickness significantly (p>0.05).

of

3.2. Moisture Content & Dissolvability

ro

Packaging films are typically in contact with foods of high moisture content. Therefore, identifying

-p

moisture content and total soluble matter is of extreme importance (Singh, Chatli, & Sahoo, 2015). Moisture contents lied in the range of 15.5-18.6 % by wt (Table 2). The moisture contents displayed

re

slight variances but the differences were not substantial. Nevertheless, moisture retention of films

lP

displayed a decreasing trend with an increase in orange oil content. Phenols inside the essential oils might have bonded to guar gum hydroxyl groups which decreases the number of available –OH

na

groups in guar gum to interact with water. Crosslinking or curcumin addition did not seem to have a

Jo ur

substantial impact on moisture content.

Water dissolution of control films containing only 1.5% guar gum and 0.6% glycerol, was quite high (around 84%). Guar gum is a branched galactomannan polymer. It consists of a long linear β(1-4) mannose backbone (of 1000-1500 units) to which α(1-6) galactopyranoside subunits are attached (Gliko-Kabir et al., 1999). Since it is a polymer of 6-carbon sugars, it possesses an abundance of hydroxyl groups, which explains the high dissolvability of guar gum films. Film water dissolvability is vital in determining its possible commercial application. In the case of edible films, highly water soluble films are used as food coatings and food encapsulation, where the food and the film are consumed simultaneously. Whereas films with low dissolvability are valuable as food packaging materials (Gomaa et al., 2018). Dissolvability decreased up to 25% with oil inclusion and a further 17% with curcumin addition. Addition of hydrophobic materials, such as curcumin and orange oil,

13

Journal Pre-proof into the film matrix increased the film hydrophobicity. Crosslinking with STMP, decreased the film dissolvability down to 32%, which means by crosslinking, film dissolvability was reduced by one half (% dissolution of 63.02 for L-2, 32.01 for P-L2 films). This indicates that crosslinking is successful in making films more water resistant, possibly providing a broader application range for guar gum emulsion films. The decrease in dissolvability with increased crosslinking is attributed to the reduction in the number of free –OH groups after phosphorylation with STMP (Gliko-Kabir et al., 2000), as depicted by the FTIR curves (Figure 3). By providing a dissolvability range from 85% down to 32%,

of

lecithin stabilized guar gum/orange oil emulsion films demonstrated potential for use in a number of

ro

different applications by presenting the possibility of tailoring for specific use.

-p

3.3. Film Opacity

Optical properties of the films are directly shaped by surface and internal heterogeneity of its structure.

re

Hence, they are strong indicators of film microstructure (Cano et al., 2015). Additionally, since

lP

packages are usually the only way of presenting the products to consumers, transparency is a crucial parameter for consumer acceptance (Pelissari et al., 2013b). Opacity values and images of films are

na

given in Table 2 and Figure 2, respectively. Opacities ranged between 3.97±0.09 and 8.23±0.09 mm-1. Opacity of the control films, containing only guar gum (1.5% w/v) and glycerol (0.6% w/v), was

Jo ur

similar to polyethylene films (4.26 mm−1), which is the commercially applicable standard in food packaging films (Galus, 2018).

Opacity increases significantly with orange oil incorporation and increases further as the oil content increases from 1% to 2% v/v. These increases are most likely associated with increased light scattering by the dispersed oil droplets. As a result, diffuse reflection increases which, in turn, lowers film transparency (Ke et al., 2019). Other researchers have also observed similar results with emulsion films (Azeredo et al., 2017; Galus, 2018; Ke et al., 2019; Lee et al., 2018). Curcumin addition and crosslinking significantly reduced opacity. Transparency is related to film bulk homogeneity and surface roughness. A more homogenous film with a smoother surface results in better light transparency (Azeredo et al., 2017; Galus, 2018; Kowalczyk et al., 2016). The presence of curcumin might have contributed to formation of a finer dispersion of oil inside the films. Guar gum contains 14

Journal Pre-proof 5% of proteins by weight. Hydrophobic interactions between the surface adsorbed proteins and smaller curcumin molecules dissolved inside oil might have synergistically promoted further reductions in interfacial tension, which in result promotes the formation of smaller oil droplets. Smaller droplets are known to scatter light more weakly than do larger ones, which causes dispersions with smaller droplets to exhibit higher transparencies (Azeredo et al., 2017; Berg, 2010).

3.4.Fourier-Transform Infrared (FTIR) Spectroscopy FTIR analyses permit the investigation of particular interactions between functional groups of the

of

chains and can be recognized as shifts in the chain’s IR bands (Aydogdu, Kirtil, Sumnu, Oztop, &

ro

Aydogdu, 2018). FTIR spectra of the films are given in Figure 3. Two prominent peaks observed in

-p

control film FTIR spectra can be summarized as follows; at the region from 3650-3000 cm-1 which is normally associated with the stretching vibration of O-H bond (Borges et al., 2013; Lei et al., 2019)

re

and in the region 3000-2800 cm-1 that is assigned to C-H bond stretching (Cano et al., 2015; Gutiérrez

lP

et al., 2016). Another absorption band was centered around 1645 cm-1 which is related to bending vibration of O-H (Borges et al., 2013; Meira et al., 2017). Absorption bands centered around 1370 cmrefer to the stretching of Amide III band originating from the protein in the gum (Pelissari et al.,

na

1

2013a). Peaks spanning between 1200-900 cm-1 centered around 1053 cm-1 correspond to stretching

Jo ur

vibration of C-O-H bonds which the film has in excess due to guar gum being a galactomannan polymer (Cano et al., 2015; Meira et al., 2017; Pelissari et al., 2013a).

Orange oil or curcumin addition yielded no substantial changes in FTIR spectra, possibly related to the low concentrations employed (1%-2%). The fact that no new peak formation occurred demonstrates that no covalent bonds were formed between orange oil, curcumin, and GG/glycerol matrix. Phosphate crosslinking of films, on the contrary, generated considerably different FTIR spectra. All bands associated with the presence of O-H groups (bands centered at 1034 cm-1 for C-O-H stretching and in the region of 3500-3000 cm-1 for O-H bond stretching) exhibited sharp drops in peak intensities. There was also the formation of a new band at 1271 cm-1 that is commonly associated with phosphate

15

Journal Pre-proof vibration (P=O) (Yıldırım-Yalçın et al., 2019). This distinct decrease in –OH bond intensity coupled with phosphate bond formation proves the effectiveness of crosslinking of GG with STMP.

3.5. Wettability Information about surface water wettability is essential in investigating the adhesive and cohesive properties of films for better spreading of the coating on the solid surface and evaluating food-coating compatibility. Contact angle (CA) is the most basic method to evaluate wettability and can be defined

of

as a measure of affinity between the liquid and the solid surface (Aphibanthammakit, Nigen, Gaucel, Sanchez, & Chalier, 2018). When the liquid is water, the contact angle becomes a measure of

ro

hydrophilicity of the film surface.

-p

CA data are listed in Table 2. Control films were highly dissolvable in water (85% dissolution in

re

water, see Table 2). The high dissolvability caused the films to disintegrate within seconds upon water

lP

deposition. Despite considerable efforts, reliable data could not be gathered. Within a few seconds, either a hole opened in the spot where the droplet was deposited, or the droplet was almost completely

na

absorbed by the film. A video demonstrating this behavior is presented as supplementary material (Figure S.1). All remaining measurements were taken during the initial 10 s after droplet deposition.

Jo ur

Within that time, there was a minimal deviation in the data with respect to time. Contact angles ranged between 32o-41o. This is smaller than 90° and is indicative of a hydrophilic surface (Lei et al., 2019). Many other studies have reported contact angles < 90o for films prepared from hydrocolloids (Aphibanthammakit et al., 2018; Galus, 2018; Kowalczyk et al., 2016; Lee et al., 2018). Oil inclusion, along with decreasing film dissolvability, also made film surface more resistant to water wetting; which enabled reliable measurement of contact angles. An increase in orange oil content from 1% to 2%, expectedly, led to improved film surface hydrophobicity as observed by an increase in CA. A decrease in surface wettability with the addition of hydrophobic materials such as essential oils has been reported in a number of studies (Atef, Rezaei, & Behrooz, 2015; Bahram et al., 2014; Lee et al., 2018; Ojagh, Rezaei, Razavi, & Hosseini, 2010). This result also explains the increase in contact angle with curcumin addition. Crosslinking, on the other hand, caused an increase 16

Journal Pre-proof in surface hydrophilicity (P-L2 from Table 2). Phosphorylation occurring between guar gum hydroxyl groups and phosphate molecules presumably resulted in the formation of a denser solid matrix where oil droplets were entrapped. The decreased mobility of the aqueous film matrix might have acted as a barrier against oil flow and subsequent deposition of oil particles across the film surface. Additionally, this could also be attributed to emulsion stabilization coming from phosphate groups bonded to proteins in guar gum which can promote hydrophobic interactions among the proteins at the oil-water interface. This phenomenon was observed by other researchers (Huang et al., 2019; Li, Enomoto,

of

Hayashi, Zhao, & Aoki, 2010; Xiong, Zhang, & Ma, 2016)

ro

3.6. Antimicrobial Properties

-p

To evaluate the antimicrobial capacity of orange oil and curcumin in the studied films, samples from four films (Control, L1, L2, and LC2) were placed onto Petri dishes with Gr- (E. Coli) and Gr+ (B.

re

Subtilis) bacteria. Inhibition zone diameters were measured and images were taken (Figure 4). In

lP

addition to inhibition zone analysis, strawberries were deposited on the films and kept at ambient

images are given in Figure 5.

na

conditions for 7 days to estimate film effectiveness in extending the shelf life of real foods. These

Jo ur

Control films exhibited no antimicrobial activity, as expected. Orange oil-containing films (L1 and L2) displayed a concentration-dependent antimicrobial activity against Gr- bacteria, as observed by the visible inhibition zones in Figure 4. Inhibition zone diameters were measured as 1.84±0.03 and 2.06±0.09 cm for L1 and L2, respectively. The inhibition zone was quite irregular in shape, as well as the circular disks of films. This indicates that films dissolved to a minor degree in the agar solutions. The high water dissolvability of films (Table 2) is in accordance with this assumption. The fact that curcumin-containing films (LC2) that display lower water dissolvability have much more regular shaped disks and inhibition zones also support this. Orange oil showed a weaker antimicrobial activity towards Gr+ positive bacteria, as depicted by the images. 1% orange oil was not enough to inhibit B.Subtilis growth, yet the 2% orange oil containing film showed some inhibition though smaller in size compared to Gr- bacteria (1.77±0.02 cm). Essential oil containing films showed antimicrobial

17

Journal Pre-proof properties previously in a number of studies (Acevedo-Fani et al., 2015; Ke et al., 2019; Lei et al., 2019; Meira et al., 2017; Wu et al., 2019). This effect is associated with the damage that essential oils cause to cell membranes. In a major portion of the studies with essential oils, researchers have reported higher antimicrobial activity against Gr+ bacteria compared to Gr- ones. Our findings, on the contrary, showed quite the opposite. Ke et al. (2019), who also observed a higher antimicrobial activity towards Gr- bacteria using cinnamon oil, explained this behavior by more effective transport of essential oils into the Gr- bacteria via outer membrane transporters present on the Gr- cell

of

membranes.

ro

Curcumin-added films interestingly displayed smaller inhibition zones compared to L2 films. Both

-p

films had the same orange oil content (2% v/v), whereas curcumin films (LC2) additionally contained 1% by wt. curcumin. The only reason that curcumin films have a smaller inhibition zone is because of

re

their lower solubility in the agar. L2 films had higher water dissolvability which might have caused

lP

the films to disintegrate by water imbibition from the agar. The fact that curcumin inhibition zones looked sharper and more regularly shaped supports this view. Unlike films with orange oil as the only

na

antimicrobial agent, LC2 films showed higher antimicrobial activity against Gr+ bacteria. Curcumin is known to possess higher bacteriostatic properties against Gr+ bacteria (Lüer, Troller, & Aebi, 2012;

Jo ur

Tyagi, Singh, Kumari, Kumari, & Mukhopadhyay, 2015). These results suggest that curcumin is the dominant antimicrobial agent in LC2 films.

Strawberry images are given in Figure 5. The strawberries placed on top of antimicrobial-containing films were better in preserving their initial quality as demonstrated by less shrinkage due to water loss, and by displaying no mold growth. Up until Day 5, films showed no visible signs of mold formation, yet on Day 6, mold growth was observed on one of the strawberries deposited on the control film. Within 7 days of observation, there was no mold growth for strawberries on L1, L2 and LC2 films. Because essential oils are volatile, they not only show antimicrobial activity in direct contact but also have the power to spread their antimicrobial activities over the whole fruit. If the berry was placed within a secondary package, the antimicrobial effect would even last longer as the volatile orange oil can be entrapped in the package headspace. Yet, even the experimental setup in Figure 5 gives us an 18

Journal Pre-proof indication of possible potential of orange oil containing films in prolonging the shelf life of foods. Encapsulation of antimicrobial agents, such as orange oil and curcumin, into the polymer matrix also provides the controlled release of these agents to the food and/or the food environment. Many studies have previously employed edible films for this purpose (Gomaa et al., 2018; Ke et al., 2019; Kowalczyk et al., 2016). LC2 films showed similar protection by orange oil only films against microbial spoilage of strawberries. Curcumin, being non-volatile, presumably only provides antimicrobial activity to the regions of the fruit that is in direct contact with the films.

of

3.7. Water Vapor Permeability (WVP)

ro

Control of moisture transfer between the food and its environment or separate portions of a multi-

-p

component food is one of the primary functions of food packaging, particularly owing to the dominant role of water on the rate of deteriorative reactions (Ahmadi, Kalbasi-Ashtari, Oromiehie, Yarmand, &

re

Jahandideh, 2012; Gontard, Guilbert, & Cuq, 1992). Consequently, water vapor permeability (WVP)

lP

constitutes one of the most widely studied properties of edible films. (Singh et al., 2015). Relative humidity (RH) of the film environment directly affects the WVP of films. WVPs increase as films are

na

stored at higher RH’s (Chang & Nickerson, 2015). WVPs of GG films lied within the relatively

Jo ur

narrow range of 1.972±0,019 – 2.886±0.062 ng m-1 s-1 Pa-1. Out of the methods employed, only orange oil dispersal was effective in decreasing the WVP of films. For most edible film applications, low WVPs are preferred. The fact that the most commonly used films in food packaging, low-density polyethylene (LDPE) films, have very low WVPs (0.036 ∙ 10-2 ng m-1 s-1 Pa-1 ) is an indication of this (Mali, Grossmann, Garcia, Martino, & Zaritzky, 2004). Nevertheless, the WVP of GG films were superior to most other similar biopolymer films composed of a single type of hydrocolloid, such as films out of potato starch (2.99-5.6 ng m-1 s-1 Pa-1) (Kang & Min, 2010) or whey protein isolate (5.16 ng m-1 s-1 Pa-1) (McHugh, Avenabustillos, & Krochta, 1993). Yet, films composed of multiple biopolymers, such as flour films, had much lower WVPs which is related to most flour’s lower intrinsic hydrophilicity (Aydogdu et al., 2018; Pelissari et al., 2013a).

19

Journal Pre-proof Dispersion of 2% v/v orange oil decreased the WVP of films by 20%. 1% orange oil, on the other hand, was not enough to lower WVPs significantly (p>0.05). An even higher orange oil content could have benefited film barrier properties even more, yet to disperse a higher amount of oil in the films, and to preserve its stability, higher lecithin concentration is required which could substantially change film physical properties. Water transfer occurs through the hydrophilic portions of the films. This explains why permeability strongly depends on the hydrophilic-lipophilic ratio of the films (Hernandez, 1994). The rate of water transfer declines due to an increased tortuosity that raises the

of

resistance against water transfer through the film. Tortuosity of the films is enhanced when the amount of oil phase is increased or oil droplet sizes are reduced (Acevedo-Fani et al., 2015). Crosslinking GG

ro

with STMP did not improve water barrier properties. This could be related to the chosen STMP

-p

concentration (0.5 equivalent) not being sufficient for complete crosslinking. Curcumin addition

re

significantly increased film WVPs. Curcumin in the film matrix might have disrupted the cohesiveness

3.8. Mechanical Properties

lP

of the polymer network, which resulted in a higher water vapor permeability.

na

A good packaging material should be able to withstand external stress and preserve both its own and

Jo ur

the food’s structural integrity during packaging, transportation, and storage (Yin et al., 2015). To assess the mechanical properties of packaging materials, the most common parameters used are tensile strength (TS), elongation at break (EAB), and Young’s modulus (YM) (Acevedo-Fani et al., 2015). TS is defined as the maximum stress that a material can withstand during stretching before it ruptures. EAB is the percent elongation of the material with respect to its initial length, YM is a measure of material rigidity (Acevedo-Fani et al., 2015; Variyar et al., 2015). TS, EAB, and YM data are listed in Table 3. TS of films ranged from 2.89±0.21 to 11.73±0.52 MPa, whereas EAB’s ranged from 39.6% to 68.3%. TS of Control, L1 and P-L2 films were higher than 4 Mpa which make them mechanically sufficient to be used as a food packaging film (Tajeddin, Rahman, & Abdulah, 2010). The films displayed especially high EAB’s relative to the characteristic range of EAB’s for typical edible films (Acevedo-Fani et al., 2015; Azeredo et al., 2017; Galus, 2018; Ke et al., 2019; Lee et al., 2018; Meira et al., 2017; Musso et al., 2017; Yin et al., 2015). The observed high elasticity provides increased 20

Journal Pre-proof resistance towards rupture by irregularities in food shape which could make GG based edible films more preferable in wrapping of irregularly shaped foods. Orange oil concentration had a negative influence on film mechanical strength and reduced film TS’s by as large as 73% (Table 3). This decline was accompanied by a rise in EAB’s and a loss in film rigidity as depicted by decreasing YM’s. This behavior is typical for a plasticizing effect (Yin et al., 2015). The hydrogen bonds established between the –OH groups in orange oil and water molecules could have increased the mobility of polymer chains leading to increased flexibility. The greater

of

degree of disruption of the polymer matrix with oil introduction supports this behavior. The oil acts as

ro

a lubricant and eases the movement of stacked polymer chains on one another. The plasticizing role

-p

that oil plays in a hydrocolloid matrix has been widely described in the literature (Binsi, Ravishankar, & Srinivasa Gopal, 2013; Carpiné, Dagostin, Bertan, & Mafra, 2015; Galus, 2018; Galus &

re

Kadzińska, 2016; Pereda, Amica, & Marcovich, 2012). Curcumin addition did not show a significant

lP

effect on film mechanical properties. Crosslinking with STMP, significantly reduced films’ EAB’s (p<0.05), and produced films with slightly higher TS values. Yet the increase in TS was not

na

statistically significant (p>0.05). Crosslinking agents, tend to have a reverse plasticizing effect in the sense that they are known to restrict polymer chain mobility (Borges et al., 2013). Similarly, Yalcin et

reduced EAB’s.

Jo ur

al. (2019) with STMP crosslinking of their GG films, also reported increased TS accompanied by

21

Journal Pre-proof

4. Conclusions The purpose of the study was to investigate the effectiveness of regularly practiced methods to enhance edible film physical properties that currently lag much behind synthetic alternatives. Dispersion of orange oil into films, curcumin addition and/or crosslinking with STMP was shown to be promising approaches in that regard. Different film specimens had largely distinct visual properties, with widely diverse transparencies (ranging between 3.97±0.09 and 8.23±0.09 mm-1). The distinct variance between different samples was also reflected in other film properties such as water solubility

of

and surface wettability (providing a dissolvability range from 32% to 85% and water contact angles

ro

between 31o-42o). Increase in orange oil concentration, crosslinking, or curcumin addition, expectedly,

-p

increased film hydrophobicity as observed by decreased water dissolvability and surface water wettability. Orange oil, accompanied by curcumin addition, bestowed antimicrobial activity to GG

re

films, depicted by visible inhibition zones on both Gr- and Gr+ bacterial cultures and by slowing down

lP

of strawberry spoilage. With the methods employed, it was also possible to improve film water barrier properties. At this point, it is important to underline the substantially high range of results measured

na

with orange oil addition and STMP crosslinking of GG films. Dissolution of films in water, for instance, ranged between 30-85%. This result emphasizes the potential of producing films that can be

Jo ur

tailored for specific applications they are going to be used for and our study could guide other researchers to manufacture films with a particular application in mind.

22

Journal Pre-proof

5. Acknowledgements Aydogdu A. has received financial support from The Scientific and Technological Research Council

Jo ur

na

lP

re

-p

ro

of

of Turkey (TUBITAK).

23

Journal Pre-proof

6. References Aboagye, D., Banadda, N., Kiggundu, N., & Kabenge, I. (2017). Assessment of orange peel waste availability in ghana and potential bio-oil yield using fast pyrolysis. Renewable and Sustainable Energy Reviews. https://doi.org/10.1016/j.rser.2016.11.262 Acevedo-Fani, A., Salvia-Trujillo, L., Rojas-Graü, M. A., & Martín-Belloso, O. (2015). Edible films from essential-oil-loaded nanoemulsions: Physicochemical characterization and antimicrobial properties. Food Hydrocolloids, 47, 168–177. https://doi.org/10.1016/j.foodhyd.2015.01.032

of

Ahmadi, R., Kalbasi-Ashtari, A., Oromiehie, A., Yarmand, M.-S., & Jahandideh, F. (2012).

(Plantago

ovata

Forsk).

Journal

of

Food

Engineering,

109(4),

745–751.

-p

seed

ro

Development and characterization of a novel biodegradable edible film obtained from psyllium

https://doi.org/10.1016/j.jfoodeng.2011.11.010

re

Aphibanthammakit, C., Nigen, M., Gaucel, S., Sanchez, C., & Chalier, P. (2018). Surface properties of

lP

Acacia senegal vs Acacia seyal films and impact on specific functionalities. Food Hydrocolloids, 82, 519–533. https://doi.org/10.1016/j.foodhyd.2018.04.032

na

Atef, M., Rezaei, M., & Behrooz, R. (2015). Characterization of physical, mechanical, and antibacterial properties of agar-cellulose bionanocomposite films incorporated with savory

Jo ur

essential oil. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2014.09.037 Aydogdu, A., Kirtil, E., Sumnu, G., Oztop, M. H., & Aydogdu, Y. (2018). Utilization of lentil flour as a biopolymer source for the development of edible films. Journal of Applied Polymer Science. https://doi.org/10.1002/app.46356

Aydogdu, A., Yildiz, E., Aydogdu, Y., Sumnu, G., Sahin, S., & Ayhan, Z. (2019). Enhancing oxidative stability of walnuts by using gallic acid loaded lentil flour based electrospun nanofibers as active packaging material. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2019.04.020 Aydogdu, A., Yildiz, E., Ayhan, Z., Aydogdu, Y., Sumnu, G., & Sahin, S. (2019). Nanostructured poly(lactic acid)/soy protein/HPMC films by electrospinning for potential applications in food industry. European Polymer Journal. https://doi.org/10.1016/j.eurpolymj.2019.01.006 Azeredo, H. M. C., Rodrigues, T. H. S., Rodrigues, D. C., Cunha, A. P., Silva, L. M. A., & Gallão, M.

24

Journal Pre-proof I. (2017). Emulsion films from tamarind kernel xyloglucan and sesame seed oil by different emulsification

techniques.

Food

Hydrocolloids,

77,

270–276.

https://doi.org/10.1016/j.foodhyd.2017.10.003 Bahram, S., Rezaei, M., Soltani, M., Kamali, A., Ojagh, S. M., & Abdollahi, M. (2014). Whey protein concentrate edible film activated with cinnamon essential oil. Journal of Food Processing and Preservation. https://doi.org/10.1111/jfpp.12086 Berg, J. C. (2010). An Introduction to Interfaces & Colloids: The Bridge to Nanoscience. Retrieved

of

from https://books.google.com/books?id=x-XZBJngdM4C Bertuzzi, M. A., Castro Vidaurre, E. F., Armada, M., & Gottifredi, J. C. (2007). Water vapor

-p

https://doi.org/10.1016/j.jfoodeng.2006.07.016

ro

permeability of edible starch based films. Journal of Food Engineering, 80(3), 972–978.

re

Binsi, P. K., Ravishankar, C. N., & Srinivasa Gopal, T. K. (2013). Development and Characterization of an Edible Composite Film Based on Chitosan and Virgin Coconut Oil with Improved

lP

Moisture Sorption Properties. Journal of Food Science. https://doi.org/10.1111/1750-3841.12084

na

Borges, A. de M. G., Banegas, R. S., Porto, L. C., Zornio, C. F., & Soldi, V. (2013). Preparation, Characterization and Properties of Films Obtained from Cross-linked Guar Gum. Polímeros

Jo ur

Ciência e Tecnologia, 23(2), 182–188. https://doi.org/10.4322/polimeros.2013.082 Cano, A., Fortunati, E., Cháfer, M., Kenny, J. M., Chiralt, A., & González-Martínez, C. (2015). Properties and ageing behaviour of pea starch films as affected by blend with poly(vinyl alcohol). Food Hydrocolloids, 48, 84–93. https://doi.org/10.1016/j.foodhyd.2015.01.008 Carpiné, D., Dagostin, J. L. A., Bertan, L. C., & Mafra, M. R. (2015). Development and Characterization of Soy Protein Isolate Emulsion-Based Edible Films with Added Coconut Oil for Olive Oil Packaging: Barrier, Mechanical, and Thermal Properties. Food and Bioprocess Technology. https://doi.org/10.1007/s11947-015-1538-4 Cha, Y., Shi, X., Wu, F., Zou, H., Chang, C., Guo, Y., … Yu, C. (2019). Improving the stability of oilin-water emulsions by using mussel myofibrillar proteins and lecithin as emulsifiers and highpressure

homogenization.

In

Journal

of

Food

Engineering.

https://doi.org/10.1016/j.jfoodeng.2019.04.009 25

Journal Pre-proof Chang, C., & Nickerson, M. T. (2015). Effect of protein and glycerol concentration on the mechanical, optical, and water vapor barrier properties of canola protein isolate-based edible films. Food Science and Technology International, 21(1), 33–44. https://doi.org/10.1177/1082013213503645 Choi, W.-S., & Han, J. H. (2001). Physical and Mechanical Properties of Pea-Protein-based Edible Films.

Journal

of

Food

Science,

66(2),

319–322.

https://doi.org/10.1111/j.1365-

2621.2001.tb11339.x Dick, M., Costa, T. M. H., Gomaa, A., Subirade, M., Rios, A. D. O., & Flôres, S. H. (2015). Edible

and

mechanical

properties.

Carbohydrate

Polymers,

130,

198–205.

ro

https://doi.org/10.1016/j.carbpol.2015.05.040

of

film production from chia seed mucilage: Effect of glycerol concentration on its physicochemical

Food

Hydrocolloids,

85(July),

233–241.

re

concentration.

-p

Galus, S. (2018). Functional properties of soy protein isolate edible films as affected by rapeseed oil

https://doi.org/10.1016/j.foodhyd.2018.07.026

lP

Galus, S., & Kadzińska, J. (2016). Whey protein edible films modified with almond and walnut oils.

na

Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2015.06.013 Ghani, S., Barzegar, H., Noshad, M., & Hojjati, M. (2018). The preparation, characterization and in

Jo ur

vitro application evaluation of soluble soybean polysaccharide films incorporated with cinnamon essential oil nanoemulsions. International Journal of Biological Macromolecules, 112, 197–202. https://doi.org/10.1016/j.ijbiomac.2018.01.145 Gibis, M., Vogt, E., & Weiss, J. (2012). Encapsulation of polyphenolic grape seed extract in polymercoated liposomes. Food & Function, 3, 246. https://doi.org/10.1039/c1fo10181a Gliko-Kabir, I., Penhasi, A., & Rubinstein, A. (1999). Characterization of crosslinked guar by thermal analysis.

Carbohydrate

Research,

316(1–4),

6–13.

https://doi.org/10.1016/S0008-

6215(99)00025-7 Gliko-Kabir, I., Yagen, B., Penhasi, A., & Rubinstein, A. (2000). Phosphated crosslinked guar for colon-specific drug delivery - I. Preparation and physicochemical characterization. Journal of Controlled Release, 63(1–2), 121–127. https://doi.org/10.1016/S0168-3659(99)00179-0 Gomaa, M., Hifney, A. F., Fawzy, M. A., & Abdel-gawad, K. M. (2018). Use of seaweed and fi 26

Journal Pre-proof lamentous fungus derived polysaccharides in the development of alginate-chitosan edible fi lms containing fucoidan : Study of moisture sorption , polyphenol release and antioxidant properties. Food Hydrocolloids, 82, 239–247. https://doi.org/10.1016/j.foodhyd.2018.03.056 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), 190–195. https://doi.org/10.1111/j.1365-2621.1992.tb05453.x Gutiérrez, T. J., Guzmán, R., Medina Jaramillo, C., & Famá, L. (2016). Effect of beet flour on films

of

made from biological macromolecules: Native and modified plantain flour. International Journal of Biological Macromolecules, 82, 395–403. https://doi.org/10.1016/j.ijbiomac.2015.10.020

ro

Hernandez, R. J. (1994). Effect of water vapor on the transport properties of oxygen through

-p

polyamide packaging materials. Journal of Food Engineering. https://doi.org/10.1016/0260-

re

8774(94)90050-7

Huang, T., Tu, Z. cai, Shangguan, X., Sha, X., Wang, H., Zhang, L., & Bansal, N. (2019). Fish gelatin

lP

modifications: A comprehensive review. Trends in Food Science and Technology, 86(February),

na

260–269. https://doi.org/10.1016/j.tifs.2019.02.048 Kang, H. J., & Min, S. C. (2010). Potato peel-based biopolymer film development using high-pressure

Jo ur

homogenization, irradiation, and ultrasound. LWT - Food Science and Technology. https://doi.org/10.1016/j.lwt.2010.01.025 Ke, J., Xiao, L., Yu, G., Wu, H., Shen, G., & Zhang, Z. (2019). The study of diffusion kinetics of cinnamaldehyde from corn starch-based fi lm into food simulant and physical properties of antibacterial polymer fi lm. International Journal of Biological Macromolecules, 125, 642–650. https://doi.org/10.1016/j.ijbiomac.2018.12.094 Khamrai, M., Banerjee, S. L., Paul, S., Samanta, S., & Kundu, P. P. (2019). Curcumin entrapped gelatin/ionically modified bacterial cellulose based self-healable hydrogel film: An eco-friendly sustainable synthesis method of wound healing patch. International Journal of Biological Macromolecules. https://doi.org/10.1016/j.ijbiomac.2018.10.196 Kotsampasi, B., Tsiplakou, E., Christodoulou, C., Mavrommatis, A., Mitsiopoulou, C., Karaiskou, C., … Zervas, G. (2018). Effects of dietary orange peel essential oil supplementation on milk yield 27

Journal Pre-proof and composition, and blood and milk antioxidant status of dairy ewes. Animal Feed Science and Technology. https://doi.org/10.1016/j.anifeedsci.2018.08.007 Kowalczyk, D., Gustaw, W., Zieba, E., Lisiecki, S., Stadnik, J., & Baraniak, B. (2016). Microstructure and functional properties of sorbitol-plasticized pea protein isolate emulsion films: Effect of lipid type

and

concentration.

Food

Hydrocolloids,

60,

353–363.

https://doi.org/10.1016/j.foodhyd.2016.04.006 Lee, M. H., Kim, S. Y., & Park, H. J. (2018). Effect of halloysite nanoclay on the physical,

of

mechanical, and antioxidant properties of chitosan films incorporated with clove essential oil. Food Hydrocolloids, 84(May), 58–67. https://doi.org/10.1016/j.foodhyd.2018.05.048

ro

Lei, Y., Wu, H., Jiao, C., Jiang, Y., Liu, R., Xiao, D., … Li, S. (2019). Investigation of the structural

-p

and physical properties, antioxidant and antimicrobial activity of pectin-konjac glucomannan

re

composite edible films incorporated with tea polyphenol. Food Hydrocolloids, 94(December 2018), 128–135. https://doi.org/10.1016/j.foodhyd.2019.03.011

food

proteins:

A

review.

LWT

-

Food

Science

and

Technology.

na

of

lP

Li, C. P., Enomoto, H., Hayashi, Y., Zhao, H., & Aoki, T. (2010). Recent advances in phosphorylation

https://doi.org/10.1016/j.lwt.2010.03.016

Jo ur

Liu, J., Wang, H., Wang, P., Guo, M., Jiang, S., Li, X., & Jiang, S. (2018). Films based on κcarrageenan incorporated with curcumin for freshness monitoring. Food Hydrocolloids, 83, 134– 142. https://doi.org/10.1016/j.foodhyd.2018.05.012 Liu, Q. R., Wang, W., Qi, J., Huang, Q., & Xiao, J. (2019). Oregano essential oil loaded soybean polysaccharide films: Effect of Pickering type immobilization on physical and antimicrobial properties.

Food

Hydrocolloids,

87(August

2018),

165–172.

https://doi.org/10.1016/j.foodhyd.2018.08.011 Lüer, S., Troller, R., & Aebi, C. (2012). Antibacterial and antiinflammatory kinetics of curcumin as a potential

antimucositis

agent

in

cancer

patients.

Nutrition

and

Cancer.

https://doi.org/10.1080/01635581.2012.713161 Mali, S., Grossmann, M. V. E., Garcia, M. A., Martino, M. N., & Zaritzky, N. E. (2004). Barrier, mechanical and optical properties of plasticized yam starch films. Carbohydrate Polymers, 56(2), 28

Journal Pre-proof 129–135. https://doi.org/10.1016/j.carbpol.2004.01.004 McHugh, T. H., Avenabustillos, R., & Krochta, J. M. (1993). Hydrophilic Edible Films - Modified Procedure for Water-Vapor Permeability and Explanation of Thickness Effects. J Food Sci, 58(4), 899–903. https://doi.org/10.1111/j.1365-2621.1993.tb09387.x Meira, S. M. M., Zehetmeyer, G., Werner, J. O., & Brandelli, A. (2017). A novel active packaging material based on starch-halloysite nanocomposites incorporating antimicrobial peptides. Food Hydrocolloids, 63, 561–570. https://doi.org/10.1016/j.foodhyd.2016.10.013

of

Moreira, R., Chenlo, F., Silva, C., Torres, M. D., Díaz-Varela, D., Hilliou, L., & Argence, H. (2012). Surface tension and refractive index of guar and tragacanth gums aqueous dispersions at different

-p

https://doi.org/10.1016/j.foodhyd.2012.01.007

ro

polymer concentrations, polymer ratios and temperatures. Food Hydrocolloids, 28(2), 284–290.

re

Musso, Y. S., Salgado, P. R., & Mauri, A. N. (2017). Smart edible films based on gelatin and curcumin. Food Hydrocolloids, 66, 8–15. https://doi.org/10.1016/j.foodhyd.2016.11.007

lP

Ojagh, S. M., Rezaei, M., Razavi, S. H., & Hosseini, S. M. H. (2010). Development and evaluation of

na

a novel biodegradable film made from chitosan and cinnamon essential oil with low affinity toward water. Food Chemistry. https://doi.org/10.1016/j.foodchem.2010.02.033

Jo ur

Okuro, P. K., Gomes, A., Costa, A. L. R., Adame, M. A., & Cunha, R. L. (2019). Formation and stability of W/O-high internal phase emulsions (HIPEs) and derived O/W emulsions stabilized by PGPR and lecithin. Food Research International. https://doi.org/10.1016/j.foodres.2019.04.028 Pelissari, F. M., Andrade-Mahecha, M. M., Sobral, P. J. do A., & Menegalli, F. C. (2013a). Comparative study on the properties of flour and starch films of plantain bananas (Musa paradisiaca).

Food

Hydrocolloids,

30(2),

681–690.

https://doi.org/10.1016/j.foodhyd.2012.08.007 Pelissari, F. M., Andrade-Mahecha, M. M., Sobral, P. J. do A., & Menegalli, F. C. (2013b). Optimization of process conditions for the production of films based on the flour from plantain bananas (Musa paradisiaca). LWT - Food Science and Technology, 52(1), 1–11. https://doi.org/10.1016/j.lwt.2013.01.011 Pereda, M., Amica, G., & Marcovich, N. E. (2012). Development and characterization of edible 29

Journal Pre-proof chitosan/olive

oil

emulsion

films.

Carbohydrate

Polymers.

https://doi.org/10.1016/j.carbpol.2011.09.019 Sgorla, D., Almeida, A., Azevedo, C., Bunhak, É. J., Sarmento, B., & Cavalcanti, O. A. (2016). Development and characterization of crosslinked hyaluronic acid polymeric films for use in coating

processes.

International

Journal

of

Pharmaceutics,

511(1),

380–389.

https://doi.org/10.1016/j.ijpharm.2016.07.033 Singh, T. P., Chatli, M. K., & Sahoo, J. (2015). Development of chitosan based edible films: process

of

optimization using response surface methodology. Journal of Food Science and Technology, 52(5), 2530–2543. https://doi.org/10.1007/s13197-014-1318-6

ro

Tajeddin, B., Rahman, R. A., & Abdulah, L. C. (2010). The effect of polyethylene glycol on the

-p

characteristics of kenaf cellulose/low-density polyethylene biocomposites. International Journal

re

of Biological Macromolecules. https://doi.org/10.1016/j.ijbiomac.2010.04.004 Tyagi, P., Singh, M., Kumari, H., Kumari, A., & Mukhopadhyay, K. (2015). Bactericidal activity of I

is

associated

with

damaging

lP

curcumin

of

bacterial

membrane.

PLoS

ONE.

na

https://doi.org/10.1371/journal.pone.0121313

Variyar, P. S., Bahadur, J., Gupta, S., Sharma, A., Mazumder, S., & Saurabh, C. K. (2015).

Jo ur

Mechanical and barrier properties of guar gum based nano-composite films. Carbohydrate Polymers, 124, 77–84. https://doi.org/10.1016/j.carbpol.2015.02.004 Wang, L., Mu, R. J., Li, Y., Lin, L., Lin, Z., & Pang, J. (2019). Characterization and antibacterial activity evaluation of curcumin loaded konjac glucomannan and zein nanofibril films. LWT. https://doi.org/10.1016/j.lwt.2019.108293 Wu, H., Lei, Y., Zhu, R., Zhao, M., Lu, J., Xiao, D., … Li, S. (2019). Preparation and characterization of bioactive edible packaging films based on pomelo peel flours incorporating tea polyphenol. Food Hydrocolloids, 90(December 2018), 41–49. https://doi.org/10.1016/j.foodhyd.2018.12.016 Xiong, Z., Zhang, M., & Ma, M. (2016). Emulsifying properties of ovalbumin: Improvement and mechanism by phosphorylation in the presence of sodium tripolyphosphate. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2016.03.007 Yin, S.-W., Zhao, Z.-G., Yin, Y., Yang, X.-Q., Shi, W.-J., Tang, C.-H., & Wu, L.-Y. (2015). 30

Journal Pre-proof Development and characterization of novel chitosan emulsion films via pickering emulsions incorporation

approach.

Food

Hydrocolloids,

52,

253–264.

https://doi.org/10.1016/j.foodhyd.2015.07.008 Yıldırım-Yalçın, M., Şeker, M., & Sadıkoğlu, H. (2019). Development and characterization of edible films based on modified corn starch and grape juice. Food Chemistry, 292, 6–13. https://doi.org/10.1016/J.FOODCHEM.2019.04.006 Zhang, Y., & Han, J. H. (2006). Mechanical and Thermal Characteristics of Pea Starch Films

Jo ur

na

lP

re

-p

ro

https://doi.org/10.1111/j.1365-2621.2006.tb08891.x

of

Plasticized with Monosaccharides and Polyols. Journal of Food Science, 71(2), E109–E118.

31

Journal Pre-proof

Tables Table 1. Film Formulations Sample Code

Guar Gum Glycerol (% w/v) (% w/v)

Orange Lecithin Oil (% v/v) (% w/v)

Curcumin (% w/v)

Control L1 L2 LC2 P-L2

1.5 1.5 1.5 1.5 1.5

0 1 2 2 2

0 0 0 1 0

0 1 1 1 1

Jo ur

na

lP

re

-p

ro

of

0.6 0.6 0.6 0.6 0.6

Crosslink with STMP +

32

Journal Pre-proof Table 2. Physical characteristics of GG film specimen Density (g/cm3)

Moisture Content (%)

Dissolution in Water (%)

Opacity

WVP x10-9 (g m−1 s−1 Pa−1)

Contact angle (°)

Control

0.66±0.02c

17.00±0.45b

84.15±0.93a

3.97±0.09d

2.495±0.058b

Not applicable 0.117±0.002c

L1

0.81±0.02b

16.04±0.39bc

64.21±1.44b

6.94±0.08b

2.397±0.084bc

34.39±0.30c

0.157±0.002b

L2

0.98±0.01a

15.53±0.22c

63.02±1.50b

8.23±0.09a

1.972±0.019d

38.83±0.29b

0.178±0.001a

2.886±0.062a

40.89±0.37a

0.183±0.002a

32.03±0.23d

0.178±0.002a

LC2

0.97±0.01a

18.59±0.19a

52.34±2.54c

5.63±0.14c

P-L2

1.05±0.02a

16.90±0.15abc

32.01±1.53d

7.05±0.17b

ro

p e

r P

f o

2.124±0.083cd

Thickness (mm)

Different letter superscripts in the same line indicate a statistically significant difference (p≤0.05). WVP: water vapor permeability.

l a

n r u

o J

33

Journal Pre-proof Table 3. Tensile properties of films Tensile Strength (MPa)

Young's Modulus (MPa) a c 11.73±0.52 39.65±2.06 28.92±3.64a Control L b c 6.26±0.23 40.50±1.74 17.1±3.54b L1 3.08±0.21c 54.48±4.85ab 5.88±0.55c L2 c a 2.89±0.21 68.27±1.14 5.11±0.35c LC2 c bc 4.19±0.26 49.09±1.99 7.44±1.55c P-L2 Different letter superscripts in the same line indicate a statistically significant difference (p≤0.05). WVP: water vapor permeability.

Jo ur

na

lP

re

-p

ro

of

Elongation at break (%)

34

Journal Pre-proof Figure Captions

Figure 1. Images of film specimen Figure 2. FTIR spectra of GG films. Figure 3. Images of bacterial culture plates incubated with GG films. (Top) E. Coli cultures (Bottom) B. Subtilis cultures Figure 4. Images of strawberries deposited on GG films taken over the course of 7 days. From left to right, the film samples are Control, L1, L2 and LC2, respectively. Figure 5.

Jo ur

na

lP

re

-p

ro

of

Author statement Ayca Aydogdu: Conceptualization, Methodology, Investigation Emrah Kirtil: Investigation, Writing - Original Draft, Writing - Review & Editing, Visualization Semih Bezci: Investigation Clayton Radke: Supervision

35

Journal Pre-proof Highlights 1. Orange oil/curcumin addition or crosslinking improved physical properties of films 2. Orange oil and curcumin addition increased film hydrophobicity. 3. All films other than control displayed antimicrobial activity.

Jo ur

na

lP

re

-p

ro

of

4. Methods applied yielded distinctly different solubilities and visual appearances.

36

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6