Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Label_Title

Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Label_Title

Dear Label_Name,

Greetings! I hope you are well.

I am writing on behalf of an international publishing house, Science and Education Publishing, USA (http://www.sciepub.com).

Science and Education Publishing (SciEP) is a multidisciplinary open access publisher of Journals covering the fields of Science, Technology and Medicine. All SciEP publications are subject to high-quality peer review, editorial and production processes and are freely available online.

Welcome to the April, 2013 edition of SciEP newsletter, providing monthly summaries of articles on science & education related topics of interest to scientist and professionals. The mission of our journals is to provide an open access forum for publishing new findings on issues pertinent to scientific and academic field. We also invite you to submit original research papers, review articles, short reports, or case studies are considered for publication in our Multidisciplinary Journals.

American Journal of Public Health Research
DOI: 10.12691/ajphr-1-1-3

The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

American Journal of Medical and Biological Research
DOI: 10.12691/ajmbr-1-1-2

The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
Lelevich Sergey Vladimirovich, Khrustalev Vladislav Victorovich, Barkovsky Eugene Victorovich, Shedogubova Tatyana Aleksandrovna

American Journal of Medical Sciences and Medicine
DOI: 10.12691/ajmsm-1-1-1

Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
DOI: 10.12691/ajidm-1-1-2

The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

We have released issues of some journals on February 2013.
American Journal of Public Health Research
American Journal of Medical Sciences and Medicine
American Journal of Medical and Biological Research
American Journal of Pharmacological Sciences
American Journal of Clinical Medicine Research
American Journal of Nursing Research
American Journal of Cancer Prevention
American Journal of Medicine Studies
American Journal of Infectious Diseases and Microbiology
American Journal of Cardiovascular Disease Research
American Journal of Biomedical Research
American Journal of Mechanical Engineering
American Journal of Microbiological Research
Journal of Preventive Medicine
American Journal of Food and Nutrition
American Journal of Hypertension Research
American Journal of Sports Science and Medicine
Journal of Cancer Research and Treatment
American Journal of Zoological Research
Journal of Biomedical Engineering and Technology
American Journal of Microbiological Research
Biomedical Science and Engineering

We are pleased to announce that submissions are now being accepted for peer review for all the journals across all our subject areas in SciEP.

Please submit your manuscript via our online submission system:
http://www.sciepub.com/author/signin

To unsubscribe from our mailing list, please click on the following link: unsubscribe

I am looking forward to hearing from you.

Kind regards,

David Rain
Email:join@sciepub.com
Science and Education Publishing (http://www.sciepub.com)

Influence of Preparation Methods on the Properties of Emulsified Films Based on Cassava Starch

ADJOUMAN Yao Désiré*, GNAGNE Hadiowe Eliane, KOUASSI Kouadio Benal, NINDJIN Charlemagne, TETCHI Fabrice Achille, AMANI N’Guessan Georges

Food Science and Technology department, Université Nangui ABROGOUA, Abidjan, Côte d’Ivoire

Abstract: Composite films in which a lipid compound is incorporated are generally referred to as emulsified films. Since starch, mainly cassava starch, is abundantly available, this study compared two methods for producing emulsified films based on cassava starch, to see which one produces films with interesting barrier and mechanical properties. Both methods involved firstly mixing the base matrix with oil to create the emulsion (Met 2) and secondly separating the two phases by emulsifying the oil in water before mixing with the base matrix (Met 1). The results of this study showed a significant difference between the thickness, water content and solubility of the films obtained according to the preparation method. Thickness values were 81.09 µm and 94.68 µm for Met 1 and Met 2 respectively. For the water content of the films, the values were 18.71% and 24.53% for Met 1 and Met 2 respectively. For water solubility, the values were 14.32% and 53.24% for Met 1 and Met 2 respectively. Statistical analysis showed a significant difference between the water vapor permeability of the films obtained according to the preparation methods (Met 1 and Met 2). The values were 3.93.10⁻¹¹ g. Pa⁻¹s⁻¹m⁻¹ and 5.44.10⁻¹¹ g. Pa⁻¹s⁻¹m⁻¹ for Met 1 and Met 2 respectively. The analysis also showed a significant difference between the tensile stress at break and the elongation at break of the films obtained according to the preparation methods (Met 1 and Met 2). Tensile stress at break values were 6.68 MPa and 4.77 MPa respectively for Met 1 and Met 2. Elongation at break values were 65.21% and 56.12% for Met 1 and Met 2 respectively. All the results obtained in this study lead to the conclusion that the preparation method for starch-based emulsified films exerts a significant influence on the properties of the films obtained.

Keywords: cassava starch, emulsified film, film-forming properties, homogenization techniques, edible films

Received August 05, 2024; Revised September 07, 2024; Accepted September 13, 2024

Citation: ADJOUMAN Yao Désiré, GNAGNE Hadiowe Eliane, KOUASSI Kouadio Benal, NINDJIN Charlemagne, TETCHI Fabrice Achille, AMANI N’Guessan Georges, Influence of Preparation Methods on the Properties of Emulsified Films Based on Cassava Starch. Journal of Polymer and Biopolymer Physics Chemistry, 12 (2). 15-21. January 2024. doi:10.12691/jpbpc-12-2-1

1. Introduction

Edible films are thin layers of polymers that can be consumed [1]. They can be heterogeneous in nature, consisting of a mixture of polysaccharides, proteins and/or lipids. This approach makes it possible to use one of the distinct functional characteristics of each category of film-forming agent [2]. The combination of polymers to form films can be between proteins and carbohydrates, proteins and lipids, carbohydrates and lipids, or synthetic polymers and natural polymers. The main aim of composite film production is to improve permeability or mechanical properties, as required by a specific application. These heterogeneous films are applied either as an emulsion, suspension, or dispersion of immiscible constituents, or in successive coating layers (or multilayer films), or as a solution in a common solvent. As mentioned above, composite films contain both lipids and hydrocolloid components (proteins or polysaccharides) to exploit the advantages of both lipids and hydrocolloid components. When a barrier to water vapor is required, the lipid component fulfils this function, while the hydrocolloid component provides the necessary mechanical strength [3]. Several studies have been carried out into the possible improvement of the properties of films based on starch, which is a hydrocolloid, by incorporating lipid or protein compounds [4] [5] [6] [7] [8] [9] [10] [11]. Composite films in which a lipid compound is incorporated are generally referred to as emulsified films. Emulsified films and coatings are in fact films in which lipids are dispersed within a macromolecular network that has a hydrophilic character [12] [13]. Emulsified materials are obtained in a single film-forming casting and drying process. Their properties generally depend on preparation techniques, the type and quantity of components (hydrocolloids and lipids) and their compatibility, as well as microstructural heterogeneity [14]. Previous studies have shown that smaller particle sizes and more homogeneous distributions of lipid globules in emulsion-based films lead to lower water vapor permeability values [15] [16] [17] [18] [19]. Thus, the homogeneity and integrity of the oil-containing polysaccharide film depend closely on the miscibility of the hydrophobic molecules in the hydrophilic matrix, leading to a laminate structure or emulsified mixture [20]. The process of emulsifying the lipid phase in the aqueous phase is necessary before casting to form a film or apply a coating. Droplet size is a key factor in emulsion stability and affects viscosity and other important properties [13].

Various homogenization techniques are used to prepare film-forming emulsions. Rotor-stator homogenizers are often used and can achieve a particle size of 1 µm [21] [22]. Particle size can be further reduced by applying high-pressure homogenizers to the system [23]. Microfluidization can provide emulsions with narrower particle size distributions due to the shear force of ultra-high-pressure homogenization and the severe constraints of head-on collision [24]. Microfluidization and sonication can produce nanoemulsions in the size range 150 to 700 nm. Intensifying the homogenization conditions of the film-forming emulsion affects the size of lipid structures in dried films, promoting mechanical strength, gloss, and film transparency [13]. These different homogenization techniques are essentially applied to improve the barrier and mechanical properties of emulsified films. The findings of the study by [25] on the influence of hydrocolloid nature on the structure and functional properties of emulsified edible films, indicated that the mechanical properties of emulsified films of cassava starch and a hydrogenated vegetable fat were relatively poor. In their methodology for preparing emulsified films of cassava starch and a hydrogenated vegetable fat, the mixture was pre-dispersed under magnetic stirring for 5 min at 600 rpm before being homogenized using an Ultra-Turrax T25 homogenizer for 2 min at 24,000 rpm. However, the characteristics of biopolymer-based films are highly dependent on their composition and preparation method [26]. Such a method applied to starch would undoubtedly lead to a reduction in viscosity and a loss of rigidity in the resulting film. Moreover, cassava starch films prepared by extrusion processes do not have good properties, due to the high shear rates applied [27]. Thus, the use of cassava starch in the production of emulsified films would be limited. Since starch, mainly cassava starch, is abundant and available, this study compares two methods for producing emulsified films from cassava starch and identifies the one that produces films with interesting barrier and mechanical properties.

2. Materials and Methods

2.1. Materials

Native cassava starch was cold extracted from the improved TMS cassava variety harvested at maturity after 12 months of planting in an experimental field at the National Center for Agronomic Research in Côte d'Ivoire (CNRA). After harvesting, the tubers were transported to the chemical laboratory of the Swiss Center for Scientific Research in Adioppodoumé (Yopougon, Abidjan). The following morning, using the method described in [28], the native starch was extracted. Bidistilled glycerol (C3H8O3) with a purity of 99.5% was used as plasticizer and soy lecithin ((C40H80ON8P) n) was used as emulsifier. To determine the water vapor permeability of the films, anhydrous calcium chloride (CaCl2) (6-14 mm) was used. VWR prolabo Chemicals (Leuven/Belgium) supplied all the chemicals used in this study. The peanut oil used in this study, CORA brand (Gembloux/Belgium), was purchased from a supermarket in Belgium.

2.2. Methods

2.2.1. Preparation of Emulsified Films Based on Improved Cassava Starch

Two methods of preparing emulsified films were used in this study. The first method (Met 1) was based on that described by [29] [30]. The emulsified films were prepared in two stages. In the first step, 4 g (w/w, starch) of cassava starch were mixed with glycerol (1.2 g based on starch mass) and 2/3 distilled water in the final mixture. The mixture was heated for 20 minutes from 30 to 75°C with constant stirring at 750 rpm. Next, peanut oil (w/w, based on starch mass) and soy lecithin (w/w, based on the amount of oil added) with 1/3 distilled water were added to the total mixture, which was also heated for 20 minutes from 30 to 75°C with constant stirring at 750 rpm. The solution of peanut oil, soy lecithin and distilled water was homogenized at 24,000 rpm for 2 minutes using the Ultra Turrax T 25 (IKA-WERKE/ from Germany). In the second stage, the homogenized solution was mixed with starch and glycerol, then heated from 75 to 95°C for 25 minutes at 750 rpm. The second method (Met 2) of the study was based on that described by [25], considering pre-dispersion (600 rpm for 5 min) and homogenization (24,000 rpm for 2 min) with Ultra-Turrax. On the surface of a Petri dish, 20 g of the final solution obtained from both methods is poured and dried in a ventilated oven model Memmert UF-110 (from Germany) at 35°C for 24 hours. Oven-dried films are removed and stored at 62% humidity (ammonium nitrate, NH4NO3) for 48 hours in a desiccator at 25°C prior to testing.

2.2.2. Thickness of Emulsified Films

The thickness of all films was determined using an NSK (Japan) manual micrometer. Measurements were taken at 10 random points on the films, in triplicate for each film.

2.2.3. Moisture Content of Emulsified ﬁlms

The water content of the ﬁlms was determined gravimetrically by oven-drying at 105°C to a constant weight (dry sample weight) [31]. The results were expressed as a percentage of the initial ﬁlm weight according to the following expression ((equation (1)):

[picture] | (1)

With H, humidity; P0, initial weight; Pf, ﬁnal weight. At least triplicate analyses were performed per variety and formulation.

2.2.4. Water Solubility of Emulsified ﬁlms

Determination of the water solubility of the films was carried out according to the method described by [32]. 2 x 3 cm pieces of each ﬁlm were cut and stored for seven days in a desiccator containing silicate gel. After the seven days, samples were weighed (to the nearest 0.0001 g) g) (initial dry weight) using a precision balance (Mettler-Toledo AE-200, Precisa Instruments Ltd, Greifensee/Switzerland) and placed in beakers containing 80 mL deionized water. Samples were kept under constant stirring at 200 rpm in a stirring chamber (Heidolph promax 1020 mechanical stirrer, Schwabach/Germany) for one hour at laboratory temperature (~25°C). The ﬁlm pieces were then collected by ﬁltration and re-dried in an oven at 60°C to constant weight. The percentage of total solid matter (or percentage solubility) was calculated as follows ((Equation (2)):

[picture] | (2)

With S, solubility; P0, initial dry weight; Pf, ﬁnal dry weight. The measurements were made in triplicate for each ﬁlm.

2.2.5. Water Vapor Permeability (WVP) of Emulsified ﬁlms

The water vapour permeability of the ﬁlms was carried out using the method [33] with a few modiﬁcations. Samples of 9 cm-diameter ﬁlms were mounted and sealed on the opening of a cylindrical jar containing 50 g of anhydrous calcium chloride to maintain a relative humidity of 0%. The assembly was placed in a desiccator at 25°C containing a saturated solution of sodium chloride (75% RH). Once equilibrium conditions had been reached (2 h), eight weight measurements were taken over 8 h. Changes in cup weight were recorded to the nearest 0.0001 g and plotted against time. The slope of each line was calculated using linear regression (r² > 0.99) and water vapour transmission (WVTR) was calculated as the ratio of the slope of the straight line (g/s) to the transfer surface (m²). The exposed surface (the cylindrical pot surface of 5.6 cm in diameter) was 0.00246 m² and WVP (g. Pa⁻¹ s⁻¹ m⁻¹) calculated according to the following expression (Equation (3)):

[picture] | (3)

With S, vapor pressure at saturation of the water (Pa) at the test temperature (25°C) = 3170 Pa; R₁, relative humidity in the desiccator; R₂, relative humidity in the pot; d, thickness of the ﬁlm (m). All tests were conducted in triplicate.

2.2.6. Mechanical Properties of Emulsified ﬁlms

Tensile tests were performed using a TA.XT2 texture analysis (Stable Micro Systems, Godalming/England) according to [34] using an A/TG traction handle system. The parameters determined were tensile strength and deformation at break (elongation at break) for emulsified ﬁlms. The tested ﬁlms trips (8 x 2.5 cm) were cut with a scalpel for each preconditioned sample (62 % relative humidity, 25°C) and placed between the machine jaws. The thickness of each sample was measured at four points along its length with a Mitutoyo micrometer (NSK/Tokyo, Japan Micrometer). The initial separation between the handles was set at 50 mm. The upper part of the probe gradually rises by stretching the ﬁlm at a constant speed of 10 mm/min until it ruptures. The force-elongation curves were recorded. Force and elongation were measured at the point of failure. For each formulation, eight samples were tested. The measurements were made in triplicate for each ﬁlm.

2.2.7. Color of Emulsified ﬁlms

The colour of the ﬁlms was determined by the method described by [35] and by [36]. This determination was made using an international Datacolor spectrophotometer D65/10 (Miniscan XE Virginia, USA). L* represents the luminance (from white to black), (a*) the chromatic index from green to red and (b*) that from yellow to blue. From this data, equation (4) was used to calculate the colour difference (ΔE* ab) of emulsified starch-based ﬁlms compared to the colour of a white reference surface:

[picture] | (4)

2.2.8. Statistical Analysis

Single-factor ANOVA variance analysis was performed on the mechanical, optical and barrier properties of starch-based emulsified ﬁlms, prepared by two different methods, using STATISTICA 7.1 software. The DUNCAN test at a 5 % threshold was applied to detect differences between sample sets.

3. Results

3.1. Film Thickness, Water Content and Water Solubility

Table 1 shows the values for film thickness, water content and water solubility, depending on the method used to prepare the emulsified films. Thickness values were 81.09 µm and 94.68 µm respectively for the different methods of preparing Met 1 and Met 2 emulsified films. Film water content values were 18.71% and 24.53% for Met 1 and Met 2 respectively. For water solubility, the values were 14.32% and 53.24% for Met 1 and Met 2 respectively. Statistical analysis of variance ANOVA showed a significant difference (p< 0.05) between the thickness, water content and solubility of films obtained according to the preparation method (Table 1).

Table 1. Film thickness, water content, solubility and water vapor permeability by preparation method

3.2. Water Vapor Permeability (WVP)

Water vapor permeability values are shown in Table 1. Statistical analysis of variance ANOVA showed a significant difference (p< 0.05) between the water vapor permeability of the films obtained according to the preparation methods (Met 1 and Met 2). The values were 3.93.10-11 g. Pa-1s-1m-1 and 5.44.10-11 g. Pa-1s-1m-1 for Met 1 and Met 2 respectively.

3.3. Film Mechanical Properties

The values for stress at break (TS) and elongation at break (EB) are shown in Table 2. Statistical analysis of variance (ANOVA) showed a significant difference (p < 0.05) between the tensile stress at break and the elongation at break of films obtained according to the preparation methods (Met 1 and Met 2). The values for tensile strength at break were 6.68 MPa and 4.77 MPa for Met 1 and Met 2 respectively. Elongation at break values were 65.21% and 56.12% for Met 1 and Met 2 respectively (Table 2).

Table 2. Mechanical properties of films by preparation method

3.4. Film Color Parameters

The values of the colour parameters, except for a* (Table 3), varied significantly (p< 0.05) according to the statistical analysis of variance ANOVA. L* parameter values were 91.17 and 91.42 for Met 1 and Met 2 respectively. Values for a* were -0.38 and -0.43 for Met 1 and Met 2 respectively. For b*, the values were 2.02 and 1.93 respectively for Met 1 and Met 2. For ΔE*, the values were 3.01 ± 0.001 and 2.76 ± 0.014 for Met 1 and Met 2 respectively (Table 3).

Table 3. Film color parameter values by preparation method

4. Discussion

Statistical analysis of variance ANOVA showed a significant difference (p < 0.05) between the thickness, water content and solubility of films obtained according to the preparation method. Film thickness is an important characteristic that needs to be evaluated. It can affect the film's mechanical, optical and water vapor barrier properties [37] [38] [39]. The difference observed between film thicknesses depending on the preparation method could be due to the total solids content of the films. Indeed, according to [40], ﬁlm thickness is inﬂuenced by the solids content of the ﬁlm-forming solution and the processing parameter. In addition, [41] reported that films with essentially the same total solids content did not differ significantly in thickness, and that increasing total solids content increased film thickness. Also, film thickness depends on the reorganization of molecular chains to form a more compact matrix in composite starch films [11]. In this study, the films obtained with the Met 1 preparation method were less thick than those obtained with the Met 2 preparation method, despite the same film composition (starch, glycerol, oil, lecithin in the same proportions). The technique employed in Methodology 1 (Met 1) certainly enabled a reduction in the size of oil droplets in the starch matrix [42] [43] [44].

About the water content of the films, a significant difference was observed between those obtained using the Met 1 preparation method and those obtained using the Met 2 method. This difference could be linked to the difference in film preparation technique.

Water solubility is an important property for food packaging materials and water-insoluble or water-resistant packaging materials for food are generally desired, and ﬁlms with high water solubility may also be desired for encapsulation of drugs, foods or additives [44]. The water solubility of the emulsified films prepared in this study was significantly different. This difference could be explained by the fact that high-pressure treatment in Met 2 would have degraded the intermolecular bonds of the starch molecules and formed new inter- and intramolecular bonds with polar glycerol groups. On the other hand, soluble starch increased after high-pressure treatment, thus increasing the likelihood of amylose leaching from starch granules, contributing to the high solubility observed [45]. Also, the high-pressure process could convert the starch's crystalline regions into semi-crystalline ones.

In this situation, the number of remaining (non-crosslinked) starch functional groups would have increased [45], which would certainly have facilitated the solubility of the films obtained with Met 2.

The Met 1 emulsified film preparation method produced films with significantly lower water vapor permeability values than the Met 2 method. This observed difference is linked to the good distribution and reduction of lipid particle sizes due to the homogenization method and conditions adopted in this study. It has been shown that the water barrier properties of emulsion-based ﬁlms are closely related to the type, concentration, and size of the lipid particles and the emulsifying agent [46]. The particle size distribution of ﬁlm-forming emulsions, which is directly related to the homogenization method and conditions, has a strong eﬀect on water vapor transfer through the ﬁlms [44]. The reduction and homogeneous size distribution of lipid particles or globules signiﬁcantly reduce the water vapor permeability of edible emulsion-based ﬁlms [15] [16] [17] [18] [19] [47].

Also, several studies have shown that there is a negative correlation between the droplet size of emulsions and the water barrier characteristics of emulsified biopolymers [48]. On the other hand, the formation of an interconnected lipid network in the film matrix creates a tortuous path through the film for water molecules. The Met 1 method enabled good dispersion of oil droplet sizes. It has been shown that the tortuosity parameter is higher as the dispersed phase ratio increases or as the dispersed droplet size decreases [49].

The tensile stress at break of films prepared using the Met 1 method was higher than that of films prepared using the Met 2 method. Similarly, the elongation at break of Met 1 films was higher than that of Met 2 films. This difference in tensile strength at break could be linked to the procedure adopted to prepare the emulsified films. In the Met 2 preparation method, cassava starch, peanut oil, soy lecithin and glycerol were homogenized at 24,000 rpm for 2 minutes. The high shear rate in the starch matrix leads to a decrease in viscosity and a loss of rigidity in the resulting film. [27] have shown that cassava cassava starch films prepared by extrusion processes do not have good properties, due to the high shear rates applied.

Our observations are in line with the findings of the study by [25] on the influence of hydrocolloid nature on the structure and functional properties of emulsified edible films. In this study, the authors reported that the mechanical properties of emulsified films of cassava starch and a hydrogenated vegetable fat were relatively poor. Also, the characteristics of biopolymer-based films are highly dependent on their composition and method of preparation [26]. Furthermore, droplet size is a determining factor for emulsion stability and affects viscosity and other important properties [13]. Certainly, the Met 1 preparation methodology had a greater effect on the size of the lipid structures, thus promoting good mechanical strength. In fact, intensifying the homogenization conditions of the film-forming emulsion affects the size of the lipid structures in the dried films, favoring mechanical strength, gloss, and transparency of the films [13]. These various homogenization techniques are mainly applied to improve the barrier and mechanical properties of emulsified films [25]. Other studies have shown that the emulsification conditions of emulsified films significantly influence the final microstructure of the biopolymer and its mechanical behavior [43] [49] [50]. The difference observed is also due to the high solid lipid content in films obtained using the Met 2 preparation method. Indeed, the higher the solid lipid content, the poorer the mechanical properties of emulsiﬁed ﬁlms [25].

The L* parameter value of the films obtained with the Met 2 method was significantly higher than the L* value of the films obtained with the Met 1 method. The a* parameters of the films were negative. Color parameters are the most important factors aﬀecting consumer acceptance of a food product. The films in this study were made from the same materials in the same proportions (starch, peanut oil, soy lecithin and glycerol). The observed difference in parameters would be linked to changes in the average size of the oil droplets due to the different homogenization methods. [44] made similar observations in their study of the effect of ultrasonic treatment on the properties of nano-emulsion ﬁlms obtained from hazelnut flour proteins and clove essential oil.

5. Conclusion

Composite films in which a lipid compound is incorporated are generally referred to as emulsified films. In this study, two methods of producing emulsified films based on cassava starch were investigated. The results showed a difference between the thickness, water content and solubility, water vapor permeability and mechanical properties of the films obtained according to the preparation method. All the results obtained in this study lead to the conclusion that the preparation method for starch-based emulsified films exerts a significant influence on the properties of the films obtained. The high shear rate in the starch matrix leads to a reduction in viscosity, a loss of stiffness and thus poor film properties. Emulsified starch-based films with interesting film-forming properties can only be obtained if less dense homogenization techniques are employed.

ACKNOWLEDGEMENTS

We would like to thank Thomas BERTRAND and Marjorie SERVAIS and all those who contributed their scientific expertise to this research project.

Author Contribution Statement

Adjouman Yao Désiré: conceived and designed the experiments; performed the experiments; analyzed and interpreted the data; analyzed and interpreted the data; wrote the paper. Gnagne Eliane Hadiowe: contributed reagents, materials, analysis tools or data; wrote the paper. Benal Kouassi Kouadio: conceived and designed the experiments; analyzed and interpreted the data; wrote the paper. Nindjin Charlemagne: contributed reagents, materials, analysis tools or data. Tetchi Fabrice Achille: analyzed and interpreted the data; wrote the paper. Amani N’Guessan Georges: contributed reagents, materials, analysis tools or data.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

List of Abbreviations and Symbols

Met 1: Method 1

Met 2: Method 2

µm: micrometer

g : gram

Pa: pascal

s: second

m: meter

MPa : megapascal

mm : millimeter

rpm : turns per minute

min : minute

mL : milliliter

m² : square metre

cm : centimeter

References

[1]   | Embuscado, M.E. and Huber, K.C., "Edible Films and Coatings for Food Applications", New York, NY, USA: Springer, 9: 169-208. June 2009.
[2]   | Kester, J.J. and Fennema, O.R., "Edible Films and Coatings: A Review", Food Technol (USA). 40: 47-59. 1986.
[3]   | Belibi, P.C., Daou, T.J., Ndjaka, J.M.B., Nsom, B., Michelin, L. and Durand, B., "Une étude comparative de certaines propriétés des films d'amidon de manioc et de manioc arboricole", Physics Procedia. 55: 220-226. January 2014.
[4]   | Arvanitoyannis, I., Kolokuris, I., Nakayama, A., Yamamoto, N. and Aiba, S.I., "Physico-chemical Studies of Chitosan-poly (Vinyl Alcohol) Blends Plasticized with Sorbitol and Sucrose", Carbohydrate Polymers, 34: 9-19, June 1997.
[5]   | Arvanitoyannis, I., Nakayama, A. and Aiba, S., "Edible Films Made From Hydroxypropyl Starch and Gelatin and Plasticized by Polyols and Water", Carbohydrate Polymers, 36: 105-119, January 1998.
[6]   | Rodríguez, M., Osés, J., Ziani, K. and Maté, J.I., "Combined Effect of Plasticizers and Surfactants on the Physical Properties of Starch Based Edible Films", Food Research International, 39: 840-846, April 2006.
[7]   | Acosta, S., Jiménez, A., Chiralt, A., Martinez, A.G. and Chafer, A., "Mechanical, Barrier and Microstructural Properties of Films Based on Cassava Starch Gelatin Blends: Effect of Aging and Lipid Addition", In Inside Food Symposium Leuven Belgium,1-6, 2013.
[8]   | Dias, T.P., Grosso, C.R.F., Andreuccetti, C., De Carvalho, R.A., Galicia-García, T. and Martinez-Bustos, F., Effect of the Addition of Soy Lecithin and Yucca chidigera Extract on the Properties of Gelatin and Glycerol Based Biodegradable Films", Polímeros, 23(3): 339-345, May 2013.
[9]   | Perazzo, K.K.N.C.L., Conceição, A.C.D.V., Santos, J.C.P.D., Assis, D.D.J., Souza, C.O. and Druzian, J.I., "Properties and Antioxidant Action of Actives Cassava Starch Films Incorporated with Green Tea and Palm Oil Extracts", PloS one, 9(9): 105-199, September 2014.
[10]   | Taqi, A., Mutihac, L. and Stamatin, I., "Physical and Barrier Properties of Apple Pectin/Cassava Starch Composite Films Incorporating Laurus nobilis l. Oil and Oleic Acid", Journal of Food Processing and Preservation; 38: 1982-1993, August 2014.
[11]   | Nindjin, C., Beyrer, M. and Amani, G.N., "Effects of Sucrose and Vegetable Oil on Properties of Native Cassava (Manihot esculenta Crantz) Starch-based Edible Films", African Journal of Food, Agriculture, Nutrition and Development, 15(2) : 9905-9921, June 2015.
[12]   | Rawa, M., "Mise au Point et Caractérisation de Films Comestibles à Base de Polysaccharides et de Matières Grasses", Ecole Nationale d’Agronomie et des Industries alimentaires. Lorraine, France. Thèse. 159 p, March 2006.
[13]   | Galus, S. and Kadzińska, J., "Food Applications of Emulsion-based Edible Films and Coatings", Trends in Food Science & Technology, 45: 273-283, July 2015.
[14]   | Fabra, M.J., Pérez-Masiá, R., Talens, P. and Chiralt, A., "Influence of the Homogenization Conditions and Lipid Self-association on Properties of Sodium Caseinate Based Films Containing Oleic and Stearic Acids", Food Hydrocolloids, 25: 1112-1121, October 2011.
[15]   | McHUGH, T.H., Aujard, J.F. and Krochta, J.M., "Plasticized Whey Protein Edible Films: Water Vapor Permeability Properties", Journal of Food Science, 59 (2): 416-419, March 1994.
[16]   | Debeaufort, F. and Voilley, A., "Effect of Surfactants and Drying Rate on Barrier Properties of Emulsified Edible Films", International Journal of Food Science & Technology, 30(2): 183-190, April 1995.
[17]   | Fabra, M.J., Pérez-Masiá, R., Talens, P.and Chiralt, A., "Influence of the Homogenization Conditions and Lipid Self-association on Properties of Sodium Caseinate Based Films Containing Oleic and Stearic Acids", Food Hydrocolloids, 25: 1112-1121, July 2011.
[18]   | Tanaka, M., Ishizaki, S., Suzuki, T. and Takai, R., "Water Vapor Permeability of Edible Films Prepared from Fish Water Soluble Proteins as Affected by Lipid Type*1", Journal of the Tokyo University of Fisheries, 87: 31-38, August 2001.
[19]   | Bourtoom, T. and Chinnan, M.S., "Improvement of Water Barrier Property of Rice Starch-chitosan Composite Film Incorporated with Lipids", Food Science and Technology International, 15(2): 149-158, April 2009.
[20]   | Jiménez, A., Fabra, M.J and Chiralt, A., "Effect of Lipid Self-association on The Microstructure and Physical Properties of Hydroxypropyl-methylcellulose Edible Films Containing Fatty Acids", Carbohydrate Polymers, 82: 585-593, October 2010.
[21]   | Vargas, M., Perdones, Á., Chiralt, A., Cháfer, M. and González-Martínez, C., "Effect of Homogenization Conditions on Physicochemical Properties of Chitosan-based Film-forming Dispersions and Films", Food Hydrocolloids, 25: 1158-1164, July 2011.
[22]   | Ma, W., Tang, C.H., Yin, S.W., Yang, X.Q., Qi, J.R. and Xia, N., "Effect of Homogenization Conditions on Properties of Gelatin–Olive Oil Composite Films", Journal of Food Engineering, 113(1): 136-142, November 2012.
[23]   | Bonilla, J., Atarés, L., Vargas, M. and Chiralt, A., "Effect of Essential Oils and Homogenization Conditions on Properties of Chitosan-based Films", Food Hydrocolloids, 26(1): 9-16, January 2012.
[24]   | Sherwin, C.P., Smith, D.E. and Fulcher, R.G., "Effect of Fatty Acid Type on Dispersed Phase Particle Size Distributions in Emulsion Edible Films", Journal of Agricultural and Food Chemistry, 46(11): 4534-4538, October 1998.
[25]   | Phan, T.D., Debeaufort, F., Voilley, A. and Luu, D., "Influence of Hydrocolloid Nature on the Structure and Functional Properties of Emulsified Edible Films", Food Hydrocolloids, 23(3): 691-699, May 2009.
[26]   | Lafargue, D., Lourdin, D. and Doublier, J.L., "Film-forming Properties of a Modified Starch/κ-carrageenan Mixture in Relation to its Rheological Behaviour", Carbohydrate. Polymers, 70: 101-111, April 2007.
[27]   | Moraes, D.J.O., Scheibe, A.S., Sereno, A. and Laurindo, J.B., "Scale-up of the Production of Cassava Starch-based Films Using Tape-casting", Journal of Food Engineering, 119(4): 800-808, December 2013.
[28]   | Amani, N.G.G., Buléon, A., Kamenan, A. and Colonna, P., "Variability in starch physicochemical and functional properties of yam (Dioscorea sp) cultivated in Ivory Coast", Journal of Agricultural and Food Chemistry, 84(15): 2085-2096, September 2004.
[29]   | Adjouman, Y.D., Nindjin, C., Tetchi, F.A., Dalcq, A.C., Amani, N.G. and Sindic, M., "Water Vapor Permeability of Edible Films Based on Improved Cassava (Manihot esculenta Crantz) Native Starches", Journal of Food Processing & Technology, 8(3): 665, March 2017.

[30]  
Adjouman, Y.D., Nindjin, C., Konan, B.R., Coulibaly, S., Amani, N.G., Sindic, M. and Tetchi, F.A., "Effect of Glycerol, Peanut oil and Soybean lecithin Contents on the Properties of Biodegradable Film of Improved Cassava Starches from Côte d’Ivoire", International Journal of Agriculture Environment and Biotechnology, 3(4): 1432- 1440, July 2018.

[31]   | Versino, F. and García, M.A., "Cassava (Manihot esculenta) Starch Films Reinforced with Natural Fibrous Filler", Industrial Crops and Products, 58: 305-314, April 2014.
[32]   | López, O.V., García, M.A. and Zaritzky, N.E., "Film Forming Capacity of Chemically Modified Corn Starches", Carbohydrate. Polymers, 73: 573-581, December 2008.
[33]   | ASTM. Vapor Transmission of Material. Annual Book of ASTM, American Society for Testing and Materials, Philadelphia. 1995.
[34]   | ASTM D882-02. Standard Test Method for Tensile Properties of Thin Plastic Sheeting. Philadelphia: American Society for Testing and Materials. 2002.
[35]   | Bourtoom, T. and Chinnan, M.S., "Preparation and Properties of Rice Starch–Chitosan Blend Biodegradable Film", LWT - Food Science and Technology, 41: 1633-1641, October 2008.
[36]   | Pires, J.R.A, de Souza, V.G.L. and Fernando, A.L., "Chitosan/Montmorillonite Bionanocomposites Incorporated with Rosemary and Ginger Essential Oil as Packaging for Fresh Poultry Meat", Food Packaging and Shelf Life, 17: 142-149, September 2018.
[37]   | Mali, S., Grossmann, M.V.E., Garcia, M.A., Martino, M.N. and Zaritzky, N.E., "Barrier, Mechanical and Optical Properties of Plasticized Yam Starch Films", Carbohydrate. Polymers, 56: 129-135, March 2004.
[38]   | Mali, S., Sakanaka, L.S., Yamashita, F. and Grossmann, M.V.E., "Water Sorption and Mechanical Properties of Cassava Starch Films and Their Relation to Plasticizing Effect", Carbohydrate. Polymers, 60(3): 283-289, May 2005.
[39]   | Galus, S. and Lenart, A., "Development and Characterization of Composite Edible Films Based on Sodium Alginate and Pectin", Journal of Food Engineering, 115: 459-465, March 2013.
[40]   | Han, J.H. and Krochta, J.M., "Wetting Properties and Water Vapor Permeability of Whey-protein-coated Paper", Transactions of the ASAE (American Society of Agricultural Engineers), 42(5): 4205-1375, July 1999.
[41]   | Garcı́a, M.A., Pinotti, A., Martino, M.N., and Zaritzky, N.E., "Characterization of Composite Hydrocolloid Films", Carbohydrate. Polymers, 56: 339-345, April 2004.
[42]   | Sánchez-González, L., Vargas, M., González-Martínez. C., Chiralt, A. and Chafer M., "Use of Essential Oils in Bioactive Edible Coatings: A Review", Food Engineering Reviews, 3: 1-16, January 2011.
[43]   | Acevedo-Fani, A., Salvia-Trujillo, L., Rojas-Graü, M.A. and Martín-Belloso, O., "Edible Films from Essential-oil-loaded Nanoemulsions: Physicochemical Characterization and Antimicrobial Properties", Food Hydrocolloids, 47: 168-177, May 2015.
[44]   | Gul, O., Saricaoglu, F.T., Besir, A., Atalar, I. and Yazici, F., "Effect of Ultrasound Treatment on the Properties of Nano-emulsion Films Obtained from Hazelnut Meal Protein and Clove Essential Oil", Ultrasonics Sonochemistry, 41: 466-474, March 2018.
[45]   | Shahbazi, M., Majzoobi, M. and Farahnaky, A., "Physical Modification of Starch by High-pressure Homogenization for Improving Functional Properties of κ-carrageenan/starch Blend Film", Food Hydrocolloids, 85: 204-214, December 2018.
[46]   | Otoni, C.G., Avena-Bustillos, R.J., Olsen, C.W., Bilbao-Sáinz, C. and McHugh T.H., "Mechanical and water barrier properties of isolated soy protein composite edible films as affected by carvacrol and cinnamaldehyde micro and nanoemulsions", Food Hydrocolloids, 57: 72-79, June 2016.
[47]   | Galus, S. and Kadzińska, J., "Food applications of emulsion-based edible films and coatings", Trends in Food Science & Technology, 45(2): 273-283, October 2015.
[48]   | Pérez-Gago, M.B. and Krochta, J.M., "Lipid particle size effect on water vapor permeability and mechanical properties of whey protein/beeswax emulsion films", Journal of Agricultural and Food Chemistry, 49(2): 996-1002. February 2001.
[49]   | Fattahi, R. and Seyedain-Ardabili, M., "A comparative study on the effect of homogenization conditions on the properties of the film-forming emulsions and the resultant films", Food chemistry, 352: 129-319. august 2021.

[50]  
Otoni, C.G., Pontes, S.F.O., Medeiros, E.A.A. and de Soares, N.F., "Edible Films from Methylcellulose and Nanoemulsions of Clove Bud (Syzygium aromaticum) and Oregano (Origanum vulgare) Essential Oils as Shelf-life Extenders for Sliced Bread", Journal of Agricultural and Food Chemistry, 62(22): 5214–5219, May 2014.