orange essential oil films for application in active antimicrobial packaging

Journal Pre-proof A study of poly (butylene adipate-co-terephthalate)/orange essential oil films for application in active antimicrobial packaging Michelle Felix de Andrade, Ivo Diego de Lima Silva, Gisely Alves da Silva, Paulo Victor David Cavalcante, Fabiana Thayse da Silva, Yeda Medeiros Bastos de Almeida, Gloria Maria Vinhas, Laura Hacker de Carvalho PII:

S0023-6438(20)30136-5

DOI:

https://doi.org/10.1016/j.lwt.2020.109148

Reference:

YFSTL 109148

To appear in:

LWT - Food Science and Technology

Received Date: 8 October 2019 Revised Date:

29 January 2020

Accepted Date: 11 February 2020

Please cite this article as: Felix de Andrade, M., Diego de Lima Silva, I., Alves da Silva, G., David Cavalcante, P.V., Thayse da Silva, F., Bastos de Almeida, Y.M., Vinhas, G.M., Hacker de Carvalho, L., A study of poly (butylene adipate-co-terephthalate)/orange essential oil films for application in active antimicrobial packaging, LWT - Food Science and Technology (2020), doi: https://doi.org/10.1016/ j.lwt.2020.109148. 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. © 2020 Published by Elsevier Ltd.

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A study of poly (butylene adipate-co-terephthalate)/orange essential oil films for application in active antimicrobial packaging

Michelle Felix de Andrade1*, Ivo Diego de Lima Silva2, Gisely Alves da Silva3, Paulo Victor David Cavalcante4, Fabiana Thayse da Silva5, Yeda Medeiros Bastos de Almeida3, Gloria Maria Vinhas3, Laura Hacker de Carvalho1 1

2

Departamento de Engenharia de Materiais, Universidade Federal de Campina Grande, Campina Grande, Brazil. E-mail: [email protected]

Centro de Ciências Exatas e da Natureza, Universidade Federal de Pernambuco, Recife, Brazil 3

Departamento de Engenharia Química, Universidade Federal de Pernambuco, Recife Brazil 4 Departamento de Energia Nuclear, Universidade Federal de Pernambuco, Recife, Brazil 5 Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, Brazil Summary: The development of new packaging for food preservation has been improving every day. The present work aims to evaluate the influence of orange oil on the properties of active films produced from PBAT by solvent casting, in concentrations of 0, 5, 10 and 15 (wt. %) of Orange essential oil. These films were prepared under constant stirring for 45 minutes, using chloroform as the solvent. Limonene was found to be the main component, and the oil addition to the polymeric matrix was proven using PCA (principal component analysis). The thermal stability of the PBAT was not altered with the addition of the oil and there was no change in the melting temperature (Tm), but there was an increase in crystallization temperature (Tc). By using SEM images, it was possible to identify the presence of pores on the films surface. There was a decrease in the mechanical properties of the films, however, the obtained values are still above the threshold for usage as packaging. There was migration of Orange oil to the inoculum, reducing E. coli growth rate, observed through the measurement of absorbance. Therefore, the use of PBAT with orange oil may be a promising alternative for use as an active packaging. Keywords: Active packaging, orange oil, films, PBAT, biodegradable

1. Introduction

36

Poly (butylene adipate-co-terephthalate) (PBAT), commercially known as

37

ECOFLEX® (BASF), is a biodegradable and compostable copolyester, consisting of units

38

of terephthalic acid, adipic acid and 1,4-butanediol (Hutníková & Fričová, 2016), with a

39

life cycle of approximately 1 year (Savadekar, Kadam, & Mhaske, 2015).

40

Due to its excellent film forming properties (Muroi, Tachibana, Kobayashi,

41

Sakurai, & Kasuya, 2016), PBAT can be considered an alternative for usage in the

42

production of active packaging (Wilson, Harte, & Almenar, 2018). With the addition of an

43

antimicrobial active agent, it becomes a class of active packaging: antimicrobial

44

packaging, whose activity may inhibit the growth of microorganisms. 1

45

Essential oils from plants possess active agents in their composition that favor food

46

for a longer period of time and promote control of pathogens and bacteria (Chang, Choi,

47

Cho, & Han, 2017).

48

Orange oil, for example, extracted from the peel and with limonene as its main

49

component (Alparslan et al., 2016) presents antimicrobial activity against the growth of

50

certain bacteria and fungi such as P. chrysogenum, P. verrucosum, A. niger, A. flavus

51

(Martos-Viuda, Ruiz-Navajas, Férnadez-López, & Álvarez-Pérez, 2008).

52

This study evaluated the influence of different concentrations of orange oil in

53

PBAT films made by solvent casting, evaluating the microbial growth, thermal,

54

mechanical and morphological properties for their potential application in active

55

packaging.

56 57

2. Materials and Methods

58 59

PBAT was acquired from BASF (Germany). Orange oil (OO) from Agroterenas

60

(São Paulo) was used in the concentrations of 5, 10 and 15 (wt. % PBAT) in films made

61

by casting, using chloroform as the solvent. The samples were named PBAT, PBAT5,

62

PBAT10 and PBAT15, with 0, 5, 10 and 15% OO, respectively.

63 64

2.1. Film Production

65

For neat PBAT films, 1.4 g of the polymer was dissolved in 50 mL of chloroform

66

under magnetic stirring for 45 minutes. For PBAT and Orange oil films, the polymer

67

(1.33, 1.26, and 1.19 g for 5, 10, and 15% OO respectively) was initially dissolved in 40

68

mL of chloroform under magnetic stirring for 30 minutes. Each oil percentage was

69

weighed (0.07, 0.14, and 0.21 g for 5, 10, and 15% OO respectively) and added to 10 mL

70

of chloroform and then added to the dissolved PBAT, being stirred together for another 15

71

minutes, completing the 45 minute cycle. At the end of the mixing process, all solutions

72

were poured onto 14 cm Petri dishes and were allowed to evaporate for 48 hours. Films

73

were produced in triplicates.

74 75

2.2.Gas chromatography–mass spectrometer (GC-MS)

76

The identification of the constituents of orange oil and their quantification was

77

performed using TRACE 1300 Series gas Thermo Xcalibur Instrument (Massachusetts,

78

USA) equipped with a TGMS-5 (5% phenyl/ polydimethylsiloxane) capillary column. The 2

79

temperature programming was 60 °C/min, heating rate of 6 °C/min until 100 °C, then of

80

14 °C/min until 260 °C, and the analysis lasted a total of 18.10 min (Santana, Sia, Ferreira,

81

& Conceição, 2014).

82 83

2.3. Antimicrobial activity of the oil

84

The Antimicrobial activities against the E. coli, E. aerogenes and S. aureus were

85

tested by the disc diffusion method (NCCLS, 2003). Inocula were prepared by adding

86

microorganisms to sterile water until turbidity matched the 0.5 on the McFarland scale,

87

which corresponds to 1 to 2 x 108 CFU / mL. Plates containing Müeller-Hinton agar were

88

inoculated with 0.1 mL of inoculum and spread with a swab. Antimicrobial discs were

89

immersed in orange oil, and then added over agar. Finally, the plates were incubated in an

90

oven at 35 ° C for 48 hours, and then the diameters of the halos were read as being as

91

sensitive, intermediate, or resistant to the agents tested. Results after microbial growth

92

were compared to plates containing Müeller-Hinton agar without inoculum and the halo

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diameter interpreted according the Standards (NCCLS, 2003)

94 95

2.4. Fourier-transform infrared spectroscopy (FTIR) and Principal component

96

analysis (PCA)

97

FTIR was used at wavelength range of 4000-650 cm-1 in the absorption mode, with

98

16 scans at a resolution of 4 cm-1 making use of the Bruker Tensor 27 spectrometer

99

(United States) (Ramos et al., 2013).

100

From the obtained infrared spectra, a Principal Component Analysis was carried

101

out with the program The Unscrambler 9.7, using three films for each composition and

102

analyzing the region between 3200 and 650 cm-1 of all films. To remove any external

103

interference, a normalization treatment through the average was used.

104 105 106 107

2.5.Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC) The TGA was performed with the Shimadzu DTG 60H (Kyoto, Japan), heating rate from 35 to 550 ºC, heating speed of 20 ºC/min, under a 20 mL/min flow of nitrogen.

108

For the DSC, using a Mettler Toledo equipment, model 1STAR System (Sao

109

Paulo, Brazil) the samples were cut and weighed to approximately 6 mg. Then, they were

110

sealed in aluminum pans. All samples were subjected to three ramps: the first from 0 to

111

200 ºC with a heating rate of 30 ºC/min and lasted approximately 10 minutes to eliminate 3

112

the polymer thermal history; the second ramp from 200 to 0 °C (~17 min) and the third

113

one from 0 a 200 °C (~20 min), both with a rate of 10 °C/min (Chivrac, Kadlecová, Pollet,

114

& Avérous, 2006).

115 116

2.5. Scanning Electronic Microscopy (SEM)

117

The morphology was analyzed in a microscope TESCAN - MIRA 3 (Kohoutovice,

118

Czech Republic), at an accelerating voltage of 10kV. The samples were metallized with

119

80% Au - 20% Pd.

120 121

2.6. Thickness and Mechanical Properties

122

Films thickness was obtained using a micrometer Mitutoyo with a precision of 0,01

123

mm. 3 points in each film sample were measured and a total of 9 samples per formulation

124

were used for obtaining the average.

125

The tensile properties of the films were determined at room temperature using an

126

EMIC/DL-500MF Universal Testing Machine. Test conditions were the following:

127

crosshead speed of 5 mm/min, cell load of 500 N, distance between grips of 4 cm and

128

sample dimensions of 2,5 x 7,5 cm2. According to the methodology of the ASTM D882.

129

The mechanical properties of the films were studied by characterising the tensile strength

130

(TS), elongation at break (EAB) and elastic modulus (E)

131 132

2.7. Statistical Analysis

133

Mechanical properties data were analyzed by analysis of variance (ANOVA) using

134

the Statistica software, version 10.0.228.8. Duncan’s test was used to determine

135

differences at a level of significance of 4% (p ≤ 0,05).

136 137

2.8. Antimicrobial activity of films

138

Films antimicrobial activity test followed the methodology proposed by Dobre et

139

al., (2012) adapted. Luria-Bertani (LB) medium was used for the E. coli inoculum (greater

140

inhibition halo), achieving turbidity of 0,4 in the McFarland scale. Under sterile

141

conditions, neat and additivated 4x4 squares cut from the films were added to 20 mL of

142

LB with 1% (vol.) of E. coli. Films were incubated in an oven with temperature around 30

143

°C. Analysis were performed in 0, 6, 24, 30, 48 hours after incubation and the optical

144

density measured at 600 nm. Tests were performed in triplicates. Absorbance readings

145

were performed in an EDUTEC equipment (Brazil). 4

146 147

3. Results and Discussion

148 149

Neat PBAT films exhibited a smooth, shiny and slightly transparent surface through

150

visual analysis, and were easy to handle without fracturing and presented good

151

malleability. Films added with OO presented the same characteristics as those of the neat

152

film, except that it was slightly Orange, characteristic of the oil, without, however,

153

presenting oily aspect. Films in all conditions studied presented themselves dry, that is, no

154

oily surface, indication a possible impregnation of the oil in the polymeric chain.

155 156

The chloroform was chosen as solvent due to its affinity to PBAT and easy solubilization and evaporation.

157

Authors, while researching the ability of chloroform to evaporate after solubilizing

158

polymers in order to make films verified that all residual chloroform was removed with

159

the application of an annealing process at 40 ºC due to high molecular mobility of the

160

amorphous fraction of the polymer studied, PCL (Teske, Arbeiter, Schober, Eickner, &

161

Grabow, 2018).

162

PBAT is formed by butylene terephthalate units (BT) and butylene adipate units

163

(BA). These units share a common crystal structure, forming a mixed arrangement. This

164

unit combination creates a disordered structure, reflected on PBAT’s low crystallinity

165

(Wang, Wei, Zheng, & Xiao, 2015). Therefore, it is likely that solvent residue is in low

166

concentration due to its high capacity of evaporation among the polymeric chains.

167

Moreover, solvent residue removal is less analysed when large-scale fabrication is taken

168

into account.

169

The result of antimicrobial activity is shown in Figure 1. It was possible to

170

visualize the inhibition halos with diameters of 20.2 mm for E. coli, 10.3 mm for E.

171

aerogenes, and 10.6 mm for S. aureus. According to the interpretation of antimicrobial

172

sensitivity tests (NCCLS, 2003), E. coli growth was considered sensitive to the OO

173

because, according to the standard, the microorganism can be appropriately inhibited by

174

the antimicrobial agent. In contrast, E. aerogenes and S.aureus growth were considered

175

resistant, that is, the microorganisms are not inhibited but the concentration of the

176

antimicrobial agent. Therefore, orange oil has a greater capacity to stop E. coli growth.

177

The resulting chromatogram is shown in Figure 2 and Table 1. A total of 6

178

components were detected and the major component (99.5%) was found be d-limonene.

179

Totally 6 components were detected and the major component was found to be d-limonene 5

180

with 99.5%. The high level of purity of the oil is noticeable as well as that limonene is the

181

major component in the composition of the oil.

182 183

Figure 3 shows the FTIR spectra for all films studies as well as for the pure orange oil.

184

The main vibrational bands of PBAT are located in the same limonene region,

185

where the peak at 3065 cm-1 is related to the stretching mode of =C-H, and in 2958 and

186

2875 cm-1 , CH3 and CH2 stretching mode (Cai, Lv, & Feng, 2013). Besides this, at 1710

187

cm-1, the C=O stretching vibration of the ester group is located; and at 720 cm-1 the

188

vibrations of four or more -CH2 from the methylene group (Bheemaneni, Saravana, &

189

Kandaswamy, 2018). The vibrational mode out of the plane of the limonene =CH2 bond is

190

located at 889 cm-1 (Zapata, Villa, Correa, & Williams, 2009).

191

It can be observed in the spectra of Figure 3 that the OO characteristic functional

192

groups were not identified in the spectra of the films with OO in their composition. This

193

fact can be attributed to band superposition due the high intensity of PBAT’s molecular

194

vibration. Same behavior was observed by other authors (Mallardo et al., 2016; Rubilar et

195

al., 2013).

196

To confirm the presence of the OO in the structure of the PBAT films, a PCA

197

(principal component analysis) was performed with the infrared spectra of all films, neat

198

and added with OO.

199

PCA is a statistical method of dimension reduction that identifies indices that

200

contribute the most for variation in a sample (Liu et al., 2020). It is an efficient tool for

201

reducing data dimension because it considers the samples and the variables in its set and

202

presents results in the form of clusters (Salgueiro & Castro, 2016).

203

Thus, the region of vibration of the -CH bonds was chosen to verify the presence

204

of the oil by PCA. From the variance data, the film scores were plotted, as seen in Figure

205

4.

206

From Figure 4 the separation of films in four distinct clusters can be seen. The

207

PC1 and PC2 described 96% of the total variation of the treated data, allowing the

208

groupings of the films. The first principal component (PC1) describes 88% of the total

209

variation and the second component (PC2) 8%, that is, PC1 makes possible to visualize

210

the difference between pure PBAT films and the ones with addition of OO, and PC2

211

allows us to see the difference between the films containing OO in different

212

concentrations.

6

213

Thereby, the films with the addition of oil are found in different agglomerates from

214

the pure film, thus showing the existence of anomalous groups of the PBAT structure.

215

This may be considered, as a confirmation of the presence of OO in the polymer’s

216

structure.

217

Furthermore, the results obtained by PCA indicate that the films can be clearly

218

distinguished by composition, indication that each concentration presents differences

219

among themselves.

220

Based on the data obtained in the TGA and DTG curve, as shown in Figure 5 and

221

Table 2, one may observe the stability of the material and the influence of the orange oil

222

on the degradation temperature when in comparison to the pure film.

223

Based on these results, it is clear that the addition of oil did not alter the thermal

224

stability of the material. For every composition of the film, degradation occurred in only

225

one stage.

226

The decomposition process of all samples started at about 392 ºC, with an

227

accentuated mass loss, being finished at around 450 ºC. From the DTG curve, the

228

temperature of maximum degradation (Tmax.deg) of about 430 °C was found for all samples.

229

All of them presented a mass loss greater than 90%. It is observed in Table 2 that Tonset did

230

not present any relevant changes for any oil concentration; Tendset presented variations of 8

231

and 7 °C with addition of 10 and 15% of oil, respectively. The addition of 10% of OO

232

reduced the Tendset, while the addition of 15% increased it. The Tmax.deg did not show any

233

variation in value with addition of oil. In general, it is observed that the addition of the oil

234

did not cause significant changes in the PBAT film.

235

The decomposition of adipic acid as well as 1,4-Butanediol, present in the PBAT’s

236

structure occurs at around 340 to 400 °C (Ibrahim, Rahim, Yunus, & Sharif, 2011).

237

Changes in degradation temperatures may be related to the degradation of the oil that

238

occurs first, causing modifications in the composition of the film (Cardoso et al., 2017).

239

The thermal transitions by DSC of the films and their values may be observed in

240

Table 3. Two peaks were observed , one referring to the melting temperature (Tm) and a

241

second one related to the crystallization temperature (Tc). Table 3 shows that the Orange

242

oil did not alter the Tm of PBAT. No formulation altered the value as they remained close

243

to the value of Tm for the neat PBAT films. However, there was a decrease of the heat of

244

fusion (∆Hm) with the addition of OO at 10 and 15%, indicating that less heat would be

245

required for melting the polymer with the increment of orange oil within PBAT’s

246

structure. As for Tc, there was no alteration with the addition of 5%, but there was an 7

247

increase in its value with the addition of 10 and 15% of oil. This rise in the Tc , at higher

248

concentrations, may be caused by the molecular structure of the oil, which modified the

249

mobility of the polymer chain (Qin, Li, Liu, Yuan, & Li, 2017). The decrease in the degree

250

of crystallinity was observed in active packagings of polypropylene additivated with

251

thymol and carvacrol, indicating that this diminishing may be related to the interaction

252

between the molecules of the additive and the macromolecular structure of the polymer

253

(Ramos, Jiménez, Peltzer, & Garrigós, 2012).

254 255

In Figure 6, one may observe the micrographs of the PBAT films and of the films additivated with 5%, 10% and 15% of OO.

256

A surface with a homogeneous morphology with very clear grain contours was

257

observed in the PBAT film. As the concentration of OO became higher, the grain contours

258

became smoother, although the presence of oil droplets could be seen spread in the

259

polymer matrix. The presence of these droplets can be attributed to the difficulty that the

260

oil creates for the polymer chains to aggregate, resulting in an open structure (Atarés &

261

Chiralt, 2016).

262

Besides that, the drying of the film can lead to the formation of micropores

263

(Ahmad, Benjakul, Prodpran, & Agustini, 2012). The refered pore formation has also been

264

observed with oil containing carvacrol and thymol in polypropylene films (Ramos et al.,

265

2012).

266

Observing the neat PBAT’s film thickness values (0.098a ± 0.0084) in comparison

267

with additivated films - PBAT5 (0.101a ± 0.0050), PBAT 10 (0.094a ± 0.0050) e PBAT15

268

(0.096a ± 0.0033) – it can be verified that there is no significant variation in that property.

269

Therefore, the addition of the oil in concentrations up to 15% does not chance PBAT’s

270

structure.

271

In Table 4, it can be verified that, in comparison with neat PBAT, values for tensile

272

strength (TS), elongation at break (EAB) and elastic modulus (E) significantly decreased

273

(p ≤ 0,05) with the addition of OO.

274

An important factor for tensile strength reduction can be the partial substitution of

275

strong interactions that exist between polymeric chains by weak interactions between the

276

polymeric chain and the oil in the formation of the polymeric structure (Shen, Zhang, Liu,

277

& Wang, 2014).

278

For Sung et al., (2014), when antimicrobial additives are added to the polymeric

279

matrix, a compatibility between the component and the matrix may happen. This happens

280

because initially, the oil will migrate for amorphous regions, which are areas that 8

281

presented lower density in the polymeric structure. Then, with the raise in oil

282

concentration, all amorphous region is occupied and the oil will start to occupy the

283

crystalline region, lowering tensile strength.

284 285

For the elastic modulus, there was a decrease with the addition of oil, though this reduction was only significant for films with 5 and 10 % OO.

286

Cardoso et al., (2017) observed that the addition of orange oil in the PBAT matrix

287

caused the elastic modulus to decrease as the oil concentration increased. The authors

288

indicated that this behavior may be related to the molecular arrangement of the Polymer.

289

The PBAT presents three CH bonds, and the action of the oil happens in them, reducing

290

the elastic modulus and tensile strength.

291

For utilization as packaging, it is necessary that the polymeric material have tensile

292

strength greater than 3,5 MPa (Kim, Lee, & Park, 1995). The results obtained for all

293

samples show higher values than indicated for packaging use, therefore, for this variable,

294

PBAT can be used as packaging material.

295

In addition, PBAT mechanical properties are comparable to those of low-density

296

polyethylene (LDPE) films and high-density polyethylene (HDPE) for which TS and E

297

values are 8.6-17 and 17-35 MPa, and 500 and 300%, respectively (Li, Shankar, Rhim, &

298

Oh, 2015).

299

Therefore, even though films were produced by casting, a laboratory technique,

300

mechanical analysis proves the capacity of PBAT in maintaining its integrity under high

301

tension, confirming its potential for usage as transport or storage of products.

302

The antimicrobial activity of the films was qualitatively evaluated by measuring

303

optical density. This value is related to microorganism growth in culture media, that is, the

304

higher the E. coli concentration, the higher the absorbance. The antimicrobial activity of

305

the films can be observed in Figure 7.

306

It is possible to observe that additivated films reduced the microbial growth when

307

compared to PBAT films. After 6 hours of incubation, samples presented similar

308

absorbance readings. Possibly, in the beginning of the test, the bacterium is adapting to the

309

culture medium. After 24 hours, PBAT5, PBAT10 and PBAT15 films presented microbial

310

growth, however, when comparing to PBAT, there was a reduction in the variable

311

measured.

312

After 30 hours of incubation, there was a considerable rise in the absorbance for

313

PBAT, indicating an acceleration in the growth of E. coli. After 48 hours, the medium

9

314

containing the PBAT films still presented bacterial growth, while PBAT5, PBAT10 and

315

PBAT15 kept a lower value when compared to PBAT film.

316

Thus, it can be observed that all additivated films reduced E. coli growth. Among

317

the formulations, however, PBAT15 was the one that presented higher efficiency in

318

reducing the microbial growth.

319

By definition, antimicrobial active packaging presents as it main property the

320

inhibition of microbial growth or microbial death, making food safer and enlarging their

321

shelf lives (Wong et al., 2020).

322

Therefore, it is confirmed that there was migration of the Orange oil to the culture

323

medium, that is, the Orange oil was released from the polymeric chain and moved into the

324

inoculum, reducing E. coli growth.

325 326

It is then confirmed that orange oil is a promising additive for the manufacturing of active packaging, given the results of the antimicrobial activity.

327 328

4. Conclusion

329 330

In conclusion, we can affirm the efficacy of the action of Orange essential oil

331

against the bacterium E.coli, presenting an inhibition halo greater than 20 mm. By using

332

PCA, it was possible to visualize, by the separation of films in clusters, the presence of the

333

Orange essential oil in the PBAT films. The thermal results obtained via DSC and TGA

334

enable the utilization of orange oil in biodegradable PBAT films for possible application

335

as active packaging because the addition of the oil does not compromise the thermal

336

stability of PBAT. With the raise in oil concentration, films presented better homogeneity,

337

as observed with SEM. Even though a decrease in the values of the studied variables was

338

noticed in the tensile testing, the films presented sufficient strength for its usage as

339

packaging. There was migration of the Orange oil to the inoculum, reducing growth rate of

340

the bacterium E. coli, observed by absorbance measurements.

341 342

Acknowledgments

343 344

The authors would like to thank the Laboratory of Polymeric Materials and

345

Characterization (LMPC/UFPE) and National Council for Scientific and Technological

346

Development (CNPq) for the financial support.

347 10

348

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TABLE

Table 1. Chemical composition of orange essential oil Retention Time Active ingredient component d-Limonene α-pinene Linalool α-Phellandrene Octanal Decanal TOTAL

(min) 6.28 5.46 e 4.51 7.62 5.19 5.67 9.32

Area (%) 99.50 0.33 0.07 0.05 0.03 0.02 100 %

Table 2. Degradation and residue temperatures of the PBAT film and the films added with orange oil Tonset Tendset Tmax.deg Mass loss during Residue degradation Samples (°C) (°C) (°C) (%) (%) PBAT 392 449 428 83.84 5.61 PBAT5 394 453 427 87.04 4.57 PBAT10 394 445 428 80.41 4.85 PBAT15 390 449 429 89.54 4.62 Table 3. Specific values obtained through differential scanning calorimetry for each composition. 1st cooling 2nd heating Samples Tc ∆Hc Xc Tm ∆Hm (°C) (J/g) (%) (°C) (J/g) PBAT 64.67 13.10 11.49 120.98 10.41 PBAT5 64.67 11.93 10.46 119.67 10.99 PBAT10 65.31 5.21 4.57 119.57 9.79 PBAT15 69.49 12.63 11.08 120.21 7.20 Table 4. Effect of OO concentration on mechanical properties of neat PBAT films. Samples PBAT PBAT5 PBAT10 PBAT15 a,b,c

Tensile Strength (TS) (Mpa) 9,573a ± 0,489 8,434b ± 0,385 8,138b,c ± 0,358 7,703c ± 0,102

Elastic Modulus (E) (MPa) 49,267a ± 0,315 44,683b ± 0,376 41,780c ± 0,754 48,610a ± 0,219

shows that they are significantly different with p ≤ 0.05

Elongation at break (EAB) (%) 515,03a ± 10,08 497,37a,b ± 7,77 471,30b ± 24,46 417,33c ± 12,02

FIGURES

10.3 mm

20.2 mm

(b)

(a)

10.6 mm

(c) Figure 1 - Halos of inhibition of microorganisms: a) E. aerogenes, b) E. coli and c) S. aureus

Figure 2 - Characteristic chromatogram of the OO by GC-MS

Figure 3. FTIR spectra of: (a) PBAT, (b) OO, (c) PBAT5, (d) PBAT10 OO and (e) PBAT15.

Figure 4. Scores plot for PC1 x PC2 of Neat PBAT films (P) and films containing 5%, 10% and 15% of OO.

1

2

Figure 5. (1) TGA and (2) DTG of (a) PBAT, (b) PBAT5, (c) PBAT10 e (d) PBAT15.

Figure 6. Micrographs of the (a) Neat PBAT film and the films with addition of (b) 5%, (c) 10% and (d) 15% of OO, recorded with SEM.

Figure 7. Growth of E. coli in the presence of composite films PBAT, PBAT5, PBAT10 and PBAT15.

Highlights •

Films produced by casting from PBAT and orange oil (OO).

•

OO has a high concentration of d-limonene.

•

E. coli growth was considered sensitive to the film activity.

•

PCA indicated the incorporation of OO into the film by group separation.

•

The increase in the concentration of OO causes the appearance of pores.