chitosan aerogel with rapid shape recovery for noncompressible hemorrhage

Journal Pre-proofs Injectable Antibacterial Cellulose Nanofiber/Chitosan Aerogel with Rapid Shape Recovery for Noncompressible Hemorrhage Xialian Fan, Yijin Li, Xiumin Li, Yonghui Wu, Keyong Tang, Jie Liu, Xuejing Zheng, Guangming Wan PII: DOI: Reference:

S0141-8130(19)34000-0 https://doi.org/10.1016/j.ijbiomac.2019.10.273 BIOMAC 13774

To appear in:

International Journal of Biological Macromolecules

Received Date: Revised Date: Accepted Date:

29 May 2019 30 October 2019 30 October 2019

Please cite this article as: X. Fan, Y. Li, X. Li, Y. Wu, K. Tang, J. Liu, X. Zheng, G. Wan, Injectable Antibacterial Cellulose Nanofiber/Chitosan Aerogel with Rapid Shape Recovery for Noncompressible Hemorrhage, International Journal of Biological Macromolecules (2019), doi: https://doi.org/10.1016/j.ijbiomac. 2019.10.273

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© 2019 Published by Elsevier B.V.

Development of antioxidant and antimicrobial packaging films based on chitosan and mangosteen (Garcinia mangostana L.) rind powder Xin Zhang, Jing Liu, Huimin Yong, Yan Qin, Jun Liu *, Changhai Jin * College of Food Science and Engineering, Yangzhou University, Yangzhou 225127, PR China 

* Corresponding authors. E-mail addresses: [email protected] (Jun Liu); [email protected] (Changhai Jin)

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Abstract Mangosteen (Garcinia mangostana L.) rind has long been used as traditional medicine in Southeast Asian countries. Due to the presence of abundant polyphenols, mangosteen rind possesses potent antioxidant and antibacterial ability. In this study, mangosteen rind powder (MRP) was incorporated into chitosan (CS) film to develop active packaging for the first time. The structure, physical and functional properties of CS-MRP films containing different MRP contents (2.5, 5 and 10 wt% on CS basis) were determined. Fourier transform infrared spectroscopy revealed that the polyphenols in MRP could interact with CS through intermolecular hydrogen bonds. X-ray diffraction analysis showed the crystallinity of CS-MRP films was higher than that of CS film. Notably, MRP incorporation significantly increased the thickness, tensile strength, and UV-visible light barrier, antioxidant and antibacterial properties of CS film. However, the moisture content, water solubility, water vapor barrier ability and elongation at break of CS film were reduced by MRP incorporation. Moreover, CS-MRP film packaging effectively inhibited the increase in the peroxide value and thiobarbituric acid reactive substances of soybean oil during storage. Our results suggested CS-MRP films could be used as active packaging to increase the oxidative stability of soybean oil in food industry. Keywords: Active packaging; Antimicrobial ability; Antioxidant ability; Chitosan; Mangosteen rind powder

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1. Introduction To mitigate environmental pollution caused by traditional plastic packaging, edible and active packaging has been developed in the past decades [1]. In active packaging area, natural and biodegradable biopolymers (e.g. proteins and polysaccharides) have received increasing attention [2,3]. Among various biopolymers, chitosan (CS) has been widely used to prepare food packaging films because of its low cost and excellent film forming property [4]. CS is a unique positively charged biopolymer that is commercially produced from shellfish processing wastes. In addition, CS film can be used as the carrier of natural antioxidant and antimicrobial agents, such as essential oils, polyphenols and agricultural wastes [5−7]. Mangosteen (Garcinia mangostana L.) is one of the most popular tropical fruits and is known as “the queen of fruits” due to its pleasant flavor [8]. The dark purple or reddish rind of mangosteen accounts for 60 wt% of the fruit and is usually discarded [9]. In many Southeast Asia countries, mangosteen rind has been used as traditional medicine to cure several diseases, such as diarrhoea, dysentery, skin infection, mycosis, inflammation, cholera and fever [10,11]. The pharmaceutical properties of mangosteen rind are attributed to the presence of abundant polyphenols, such as xanthones, anthocyanins, phenolic acids and flavonoids [12,13]. Mangosteen rind has been demonstrated to possess antioxidant, anti-inflammation, anti-tumor, antibacterial, antifungal, antiviral and anti-allergic properties [13,14]. The biological properties of

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mangosteen rind are related with its harvested maturity, extraction solvent and extraction method [15,16,17]. Nowadays, mangosteen rind or its extract has been frequently incorporated into ice cream or beverage to enhance the flavor and functional property of the product [8,18]. However, only a few studies have focused on the development of active packaging by using mangosteen rind extract. For instance, mangosteen rind extract has been incorporated into bacterial cellulose matrix to develop anticancer films [19]. Notably, extraction is a time and energy-consuming process. In addition, the instability of the extract and the residue of extraction solvent limit the application of mangosteen rind extract in food packaging. By contrast, it is more convenient and economic to develop active packaging by directly adding mangosteen rind powder (MRP). In this study, polyphenol-rich MRP was directly incorporated into CS film matrix to develop active packaging for the first time. Effect of MRP content on the structure (morphology, intermolecular interaction and crystallinity), physical properties (color, thickness, moisture content, water solubility, barrier, mechanical and thermal properties) and functional properties (antioxidant and antimicrobial ability) of CS-MRP films was determined. In addition, the effect of CS-MRP film packaging on the oxidative stability of soybean oil was also evaluated. 2. Materials and methods 2.1. Materials

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Mangosteen (G. mangostana L.) fruit and soybean oil were commercially available from the local market (Yangzhou, China). CS (deacetylation degree of 95% and viscosity of 100−200 mpa∙s) was obtained from Macklin Biochemical Co., Ltd. (Shanghai, China). 2,2-Diphenyl-1-picrylhydrazyl (DPPH) was purchased from Sigma Chemical Co. (St. Louis, MO, USA). All other reagents were of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Four foodborne pathogenic bacteria strains (Escherichia coli, Staphylococcus aureus, Salmonella and Listeria monocytogenes) were supplied by the Food Microbial Laboratory of Yangzhou University (Yangzhou, China) and were used for antimicrobial assay. 2.2. Preparation and characterization of MRP MRP was prepared according to the method of Ali et al. [20] with some modifications. Fresh mangosteen fruit was washed with distilled water, and the rind of mangosteen was separated from the fruit. Afterwards, mangosteen rind was cut into small cubes, frozen immediately in liquid nitrogen and lyophilized. The obtained dried mangosteen rind was ground into powder using a disintegrator and then screened by a 80 mesh sieve to afford MRP. The particle morphology of MRP was observed by GeminiSEM 300 scanning electron microscopy (Carl Zeiss, Oberkochen, Germany). The total phenolic content in MRP was determined by Folin-Ciocalteu assay [21]. 2.3. Preparation of CS-MRP films

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CS-MRP films were prepared according to the method of Liu et al. [22] with some modifications. First, CS powder (3.2 g) was fully dissolved in 160 mL of 1% acetic acid aqueous solution. Then, CS solution was mixed with 30 wt% of glycerol and different contents of MRP (0, 2.5, 5, 10 wt%) on CS basis. The obtained film forming solution was degassed, cast on Plexiglas mould (24 cm × 24 cm) and finally dried in a temperature (30 °C) and moisture (50% relative humidity) controlled chamber for 2 days. The resultant films containing 0, 2.5, 5 and 10 wt% of MRP on CS basis were named as CS, CS-MRP I, CS-MRP II and CS-MRP III films, respectively. All the films were equilibrated in a desiccator with 50% relative humidity at 25 °C for 2 days before testing. 2.4. Structural characterization of CS-MRP films The surface and cross-sectional morphology of film was characterized by GeminiSEM 300 scanning electron microscopy (Carl Zeiss, Oberkochen, Germany). Clear surface and cross-sectional images were taken at 1500× and 800× magnifications, respectively. Fourier transform infrared (FT-IR) spectrum of film was recorded in the frequency range of 4000–400 cm−1 on Varian 670 spectrometer (Agilent Technologies, CA, USA) equipped with attenuated total reflectance mode. X-ray diffraction (XRD) pattern of film was recorded by D8 Advance diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) using Ni-filtered Cu Kα radiation in the 2θ range of 5−80°. 2.5. Determination of the physical properties of films

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2.5.1. Color The physical appearance of film was recorded by covering a semi-circular film sample (3 cm in diameter) on a printed paper. The color indices (L, a and b) of film sample were determined using SC-80C colorimeter (Kangguang Optical Instrument Co., Ltd., Beijing, China) according to the method of Yong et al. [23]. The total color difference (ΔE) and whiteness index (WI) of film were calculated as follows: E  ( L *  L) 2  (a * a) 2  (b * b) 2

(1)

2 2 2 WI  100  ( 100  L )  a  b

(2)

2.5.2. Thickness Film thickness was measured by a digital micrometer (Tester Sangyo Co., Ltd., Tokyo, Japan). 2.5.3. Moisture content and water solubility The moisture content and water solubility of film were determined by the method of Yong et al. [23]. Briefly, previously equilibrated film sample (5 × 5 cm) was dried at 105 °C until constant weight. Moisture content was calculated by the weight loss of film sample in relative to its initial weight. Water solubility was determined by immersing thoroughly dried film sample in buffer solution (pH 7.0) for 24 h. 2.5.4. Water vapor permeability (WVP)

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WVP of film was tested by the method of Zhang et al. [24]. Film sample (6 cm × 6 cm) was sealed over a 50 mL of centrifuge tube (2.7 cm in diameter) containing 45 g dried silica gel. The tube was kept in a desiccator containing distilled water at 25 °C and the weight of tube was weighed every 24 h for 8 days. 2.5.5. Optical property The light transmittance was measured by scanning film sample from 200 to 700 nm on Lambda 35 UV-vis spectrophotometer (PerkinElmer Ltd., MA, USA). 2.5.6. Mechanical properties Mechanical properties including tensile strength (TS) and elongation at break (EAB) of film sample (6 cm × 1 cm) were measured by TMS-Pro texture analyzer (Food Technology Co., VA, USA) based on the method of Zhang et al. [24]. 2.5.7. Thermogravimetric analysis (TGA) Thermal properties were determined by heating film sample from 30 to 800 °C at a constant rate of 10 °C/min under 20 mL/min of nitrogen atmosphere on Pyris 1 TGA instrument (Perkin-Elmer Ltd., Waltham, USA). 2.6. Determination of the functional properties of films

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2.6.1. Antioxidant property Antioxidant property of film was determined by DPPH scavenging assay [25]. Film samples (4, 8, 12, 16 and 20 mg) were cut into strips and immersed into 4 mL of 0.1 mmol/L DPPH methanol solution at 20 °C for 1 h. The absorbance of reaction solution was measured at 517 nm. 2.6.2. Antimicrobial property Antimicrobial property of film against four foodborne pathogens (E. coli, Salmonella, S. aureus and L. monocytogenes) was analyzed by agar diffusion method [26]. Film sample (6 mm in diameter) was placed in the upper layer of lysogeny broth agar plate and incubated at 37 °C for 16 h. Finally, the size of inhibition zone formed around film sample was measured. 2.7. Application of films in inhibiting the oxidation of soybean oil Effect of CS-MRP film packaging on the oxidative stability of soybean oil was determined according to the method of Nilsuwan et al. [27] with some modifications. First, each kind of film was prepared into a 3-side sealed pouch (7 cm × 7 cm) by heat sealing. Fresh soybean oil (20 mL) was then transferred into the film pouch, and the pouch was heat sealed. Afterwards, the film pouch containing soybean oil was stored at 25 °C up to 35 days. Oil was sampled (2 mL) every 7 days to analyze its peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). For PV measurement, 50 μL of oil sample was mixed with 5 mL of chloroform/methanol (2:1, v/v). The mixture was reacted with 50

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μL ammonium thiocyanate (30%, w/v) and 50 μL ferrous chloride (20 mmol/L) in HCl solution (3.5%, w/v) at 20 ºC for 20 min. The absorbance of reaction solution was measured at 500 nm. The PV of oil sample was calculated according to the standard curve of cumene hydroperoxide. For TBARS measurement, 0.5 g of oil sample was reacted with 2.5 mL of a mixed solution containing thiobarbituric acid (3.75%, w/v), trichloroacetic acid (15%, w/v) and HCl (0.25 mmoL/L) in a boiling water bath for 10 min. The reaction mixture was cooled to room temperature and centrifuged at 5000 g for 20 min. The absorbance of the supernatant was measured at 532 nm and the TBARS value of oil sample was calculated according to the standard curve of 1,1,3,3-tetramethoxypropane. 2.8. Statistical analysis Data were analyzed by Duncan test using SPSS 13.0 software and expressed as mean ± standard deviation (SD). Significance was defined if p < 0.05. 3. Results and discussion 3.1. Characterization of MRP As shown in Fig. 1A, mangosteen rind presented the brick red color after freeze drying. The mangosteen rind was then milled and sieved to afford MRP (Fig. 1B). SEM observation further showed MRP was in slice shape (Fig. 1C). The total phenolic content in MRP was 3.22 g gallic

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acid equivalent per 100 g powder. The potential phenolic compounds in MRP were xanthones, anthocyanins, phenolic acids and flavonoids [12,13]. Fig. 1 3.2. Structural characterization of films 3.2.1. Microstructures The surface and cross-section of films are presented in Fig. 2 and Fig. 3, respectively. CS film showed a smooth, continuous and dense microstructure, confirming the high compatibility of CS with glycerol [23]. Due to the presence of gravity sedimentation effect, most MRP was distributed on the underside of CS-MRP films. As a result, the underside of CS-MRP films was much rougher than that of CS film. In addition, the roughness of CS-MRP films gradually increased with the increase of MRP content. The lines on the surface of CS-MRP films were caused by the scratches in the mould. Nogueira et al. [28] also observed rough surfaces in arrowroot starch-blackberry pulp composite films due to blackberry pulp solid within film matrix. The cross-section of CS and CS-MRP I films was smooth and homogeneous, indicating the excellent phase compatibility between of CS, glycerol and a low content of MRP (2.5%). Notably, the aggregation of MRP appeared in the cross-section of CS-MRP II and CS-MRP III films. The MRP aggregates could destroy the tight inner structure and disrupted the compactness of CS matrix.

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Ali et al. [20] also found pomegranate peel powder aggregated in starch-based films, which damaged the integrity of film matrix and reduced the physical properties of the films. Fig. 2 Fig. 3 3.2.2. FT-IR spectra The FT-IR spectra of films are shown in Fig. 4. The FT-IR spectrum of MRP showed characteristic bands of phenolic compounds at 1637 cm−1 (C=O stretching), 1515 cm−1 (C=C stretching of aromatic ring) and 1332 cm−1 (C−O deformation of aromatic ring) [23]. As for CS film, the broad band around 3255 cm−1 represented O−H and N−H stretching. The characteristic bands at 1639, 1529 and 1335 cm−1 corresponded to C=O stretching, N−H bending and C−N stretching, respectively [8,24]. However, MRP incorporation did not significantly change the FT-IR spectrum of CS film, further confirming the good compatibility between MRP and CS matrix. Notably, the intensity of band around 3255 cm−1 (O−H stretching of polyphenols and O−H/N−H stretching of CS) gradually increased with the increased of MRP content, which was caused by intermolecular hydrogen bonds formed between the hydroxyl groups of polyphenols and the hydroxyl/amino groups of CS. In addition, the band of N−H bending shifted from 1529 to 1533 cm−1 due to intermolecular hydrogen bonds formed between the hydroxyl groups of polyphenols and

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amino groups of CS [7]. Fig. 4 3.2.3. XRD patterns XRD was applied to determine the crystalline character of films (Fig. 5). A broad peak (around 23°) was observed in the XRD pattern of MRP, suggesting MRP was in the amorphous state. Different from MRP, CS film exhibited a semi-crystalline state with four obvious diffraction peaks at 8.5, 11.8, 18.0 and 22.7° [29]. Notably, the diffraction peaks of CS were all retained in CS-MRP films. Moreover, the intensity of diffraction peaks increased after MRP was incorporated into CS film. The increased crystallinity was probably caused by the aggregates of MRP, which exhibited stronger diffraction ability than sole MRP. In addition, the incorporation of MRP produced more ordered CS network due to the intermolecular interactions between MRP and CS. Similarly, Yong et al. [30] also observed the diffraction peak intensity of CS-eggplant extract films gradually increased with the increase of extract content. Fig. 5 3.3. Physical properties of films 3.3.1. Surface color

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As shown in Fig. 6, CS film was almost colorless and transparent. CS-MRP films presented a yellow color, which gradually darkened with the increase of MRP content. In addition, MRP particles were observed in CS-MRP films. All the color parameters of CS film including L, a, b, total color difference (ΔE) and whiteness index (WI) were affected by the addition of MRP (Table 1). CS-MRP films had lower L and WI values but higher b and ΔE values than CS film (p < 0.05), which was consistent with the yellow color of CS-MRP films. Similar results were reported by Hanani et al. [31], who observed that fish gelatin films containing pomegranate peel powder exhibited a yellow color. Notably, the color of CS-MRP films gradually deepened with the increase of MRP content, which was reflected by the gradually increased ΔE of these films. Fig. 6 Table 1 3.3.2. Thickness, moisture content and water solubility The thickness of films can influence their barrier and mechanical properties [32]. As presented in Table 2, the thickness of CS film significantly increased after incorporating MRP (p < 0.05). In addition, the thicknesses of CS-MRP II and CS-MRP III films were much higher than that of CS-MRP I film (p < 0.05), which was because of more MRP solids in CS-MRP II and CS-MRP III films. Similar results were found when CS film was incorporated with olive pomace [33].

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Moisture content reflects the ability of packaging films to absorb moisture from relative humid environment [30]. The moisture contents of films are also summarized in Table 2. CS film presented the highest moisture content (p < 0.05) due to strong intermolecular hydrogen bonds between moisture and CS. By contrast, CS-MRP films had relatively lower moisture contents (p < 0.05), which was because the interactions between CS and MRP significantly restricted CS to form hydrogen bonds with moisture [33]. Moreover, the decreased moisture content in CS-MRP films was attributed to the hydrophobicity of MRP, which showed a low affinity to moisture. However, other researchers found the incorporation of pomegranate peel powder or olive pomace did not significantly change the moisture content in the films, which was due to the balance of hydrophilic and hydrophobic components in the addictives [31,33]. The water solubility reflects the ability of packaging films to resist water. As presented in Table 2, the water solubility of films gradually decreased with the increase of MRP content (p < 0.05). The decrease of water solubility in CS-MRP films was mainly because MRP was water insoluble. In addition, the intermolecular interactions between MRP and CS also restricted CS to be solubilised in water [34]. Similar decrease of water solubility was observed in fish gelatin-pomegranate peel powder films [31]. Table 2 3.3.3. WVP

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As shown in Table 2, the incorporation of MRP significantly increased the WVP of CS film (p < 0.05). In addition, the WVP of CS-MRP films increased with the increase of MRP content, which was because MRP destroyed the dense and compact network of film matrix [31]. In addition, MRP incorporation increased the motility of CS chains and facilitated the permeation of water vapor through the films. Notably, the WVP of CS-MRP III film was almost twice as compared to CS film, which was due to the aggregation of MRP created more free volume in the film matrix [30]. Similar phenomenon was observed by Alves et al. [6], who found that the WVP of CS film increased after adding grape seed extract-carvacrol microcapsules. 3.3.4. Optical property The optical property is an important feature of packaging films. Films with excellent UV-vis light barrier ability can prevent the loss of nutrient and flavor in food. The light transmittance of CS and CS-MRP films is shown in Fig. 7. CS film exhibited the highest light transmission because of lacking UV-vis absorption groups [25]. By contrast, CS-MRP films showed lower light transmission than CS film. In addition, the light transmission of CS-MRP films gradually decreased with the increase of MRP content. On one hand, the dispersed MRP particles in film matrix could scatter or block light transmission. On the other hand, the polypheols in MRP possessed strong absorption ability against UV-vis radiation [35]. In general, the light barrier ability of the films is negatively correlated with the percentage of light transmittance. Our results

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indicated the UV-vis light barrier property of CS film was significantly enhanced by polyphenol-rich MRP. Many other researchers also found the light barrier property of CS film could be elevated by incorporating olive pomace and propolis [33,36]. Fig. 7 3.3.5. Mechanical properties As shown in Table 3, the incorporation of MRP increased the TS of CS film. In addition, CS-MRP films exhibited gradually increased TS with the increase of MRP content (p < 0.05). The enhanced TS in CS-MRP films was attributed to the interactions between MRP and CS that produced strong interfacial adhesion [37]. Moreover, MRP was well distributed in film matrix and performed as reinforcing filler to strengthen film network, which greatly resisted mechanical stress [30,37]. However, the EAB of CS-MRP films decreased with the increase of MRP content, which was associated with the heterogeneous inner structures of CS-MRP films [31]. The insoluble MRP particles caused discontinuities in CS film matrix, which significantly reduced CS chain-chain interactions [20]. Similarly, fish gelatin-pomegranate peel powder films were found to possess increased TS and reduced EBA than pure gelatin film [31]. Table 3 3.3.6. Thermal property

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The thermal property of the film reflect its ability to resist decomposition at high temperatures and is frequently analyzed by TGA (Fig. 8). TGA profiles showed the weight loss of CS and CS-MRP films had three major stages. The first (30−110 °C), second (111−260 ºC) and third stages (above 260 ºC) were attributed to the volatilization of bound moisture, the degradation of residual glycerol, and the thermal decomposition of CS matrix and MRP [24,38]. Notably, the incorporation of MRP did not significantly change the TGA profile of the films. However, the derivative thermogravimetry (DTG) curve of the films was slightly changed after the incorporation of MRP. The temperature corresponding to the maximum weight loss rate of CS-MRP films (293−295 °C) was higher than that of CS film (289 °C). This indicated that the incorporation of MRP slightly enhanced the thermal stability of CS film. Fig. 8 3.4. Functional properties of films 3.4.1. Antioxidant ability The antioxidant ability (especially free radical scavenging activity) is essential for food packaging films since free radicals can cause the spoilage and oxidative damage of food [39]. As shown in Fig. 9, all the tested films possessed DPPH radical scavenging activity in a dose-dependent manner. CS film possessed the lowest antioxidant ability due to the lack of hydrogen atom donor [30]. The incorporation of

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MRP remarkably improved the DPPH radical scavenging activity of CS film (p < 0.05). In addition, the DPPH radical scavenging activity of CS-MRP films significantly increased with the increase of MRP content. Notably, the DPPH radical scavenging activity of CS-MRP III film was almost four times as that of CS film. The enhanced antioxidant ability of CS-MRP films was mainly attributed to the presence of polyphenols in MRP, which could capture free radicals by donating phenolic hydrogen [23]. Similar enhancements in antioxidant ability were observed when polyphenol-rich black soybean extract and eggplant extract were incorporated into CS matrix [7,30]. Fig. 9 3.4.2. Antimicrobial ability Since foodborne pathogens can seriously affect the quality of food, antimicrobial ability is an important property for active packaging [40]. The antimicrobial ability of CS and CS-MRP films are summarized in Table 4. The antimicrobial ability of CS film was attributed to the cationic property of CS that could interact with the cell membrane of foodborne pathogens, resulting in increased cell permeability [40,41]. CS-MRP films showed a higher antimicrobial ability than CS film (p < 0.05), which was related to the presence of polyphenol-rich MRP. The antimicrobial mechanisms of polyphenols were related to the increased permeability of cell membranes, the deformation of cells and the inhibition of DNA/RNA synthesis [42,43]. The enhanced antimicrobial ability was observed when pomegranate peel powder was added into fish

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gelatin films [31]. In this study, all the films showed higher antimicrobial ability against Gram-positive bacteria than Gram-negative bacteria, which was due to the difference in the cell wall structure, cell physiology and metabolism between Gram-positive and Gram-negative bacteria [44]. Our results were in agreement with those of Hanani et al. [31], who reported phenolic compounds exerted higher antimicrobial ability against Gram-positive bacteria than Gram-negative bacteria. Table 4 3.5. Application of films in inhibiting the oxidation of soybean oil 3.5.1. PV Oxidative rancidity is a major problem for edible oil and oil-containing products [45]. After oxidative rancidity, oil produce peroxides, aldehydes, ketones and other small molecules that have adverse effects on human health. The primary oxidation of oil is often assessed by PV [27]. The changes in the PV of soybean oil during storage are shown in Fig. 10. The PV of oil in four kinds of film pouches increased sharply in the first 14 days, indicating the lipid oxidation of oil entered propagation stage. This was because lipid radicals could react with oxygen to form peroxyl radicals, which acted as the chain carriers of the rapid progressing reaction by attacking a new lipid molecule [46]. The PV of oil decreased after 14 days of storage and then slightly increased and fluctuated between 21 and 35 days of storage. The reduction in PV was due to

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the decomposition of hydroperoxides into secondary oxidation products [47]. As compared with CS film, CS-MRP films showed lower PVs throughout 35 days of storage due to the strong antioxidant activity of MRP released from CS-MRP films. Moreover, oil packaged in the CS-MRP III film exhibited the lowest PV. Fig. 10 3.5.2. TBARS TBARS reflects the quality of oil by measuring the content of aldehydes and ketones formed in the secondary oxidation stage of oil [46]. Effect of different film packaging on the TBARS value of oil during storage is shown in Fig. 11. During the early stage of storage (within 14 days), oil in all the film pouches showed low TBARS values. After 14 days, the TBARS value of oil in different film pouches increased sharply, indicating a large amount of aldehydes and ketones were produced [48]. However, the TBARS value of oil in CS-MRP films was lower than that in CS film. This suggested the antioxidant activity of MRP released from CS-MRP films inhibited the decomposition of hydroperoxides into secondary oxidation products. Fig. 11 4. Conclusion

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Active packaging films were developed by incorporating MRP into CS matrix. FT-IR analysis revealed that CS could interact with polyphenols in MRP through hydrogen bonds. The intermolecular interactions greatly improved the TS of CS-MRP films. Due to abundant polypheols in MRP, CS-MRP films showed higher UV-vis light barrier, antioxidant and antimicrobial properties than CS film. Moreover, CS-MRP film packaging improved the oxidative stability of soybean oil. Our results suggested CS-MRP films (especially CS-MRP III film) could be utilized as active packaging materials to prevent food oxidation and spoilage, thereby extending the shelf-life of food products. Acknowledgements This work was financed by National Natural Science Foundation of China (Nos. 31571788 and 31871803), Natural Science Foundation of Jiangsu Province (No. BK20151310) and Qing Lan Project of Jiangsu Province. Reference [1] S. Dehghani, S.V. Hosseini, J.M. Regenstein, Edible films and coatings in seafood preservation: A review, Food Chem. 240 (2018) 505−513. [2] P. Cazón, G. Velazquez, J.A. Ramírez, M. Vázquez, Polysaccharide-based films and coatings for food packaging: A review, Food Hydrocolloid. 68 (2017) 136−148.

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Figure captions: Fig. 1. Photos of freeze-dried mangosteen rind cubes (A) and MRP (B), and SEM image of MRP (C). Fig. 2. The surface morphology of CS (A), CS-MRP I (B), CS-MRP II (C) and CS-MRP III (D) films. Fig. 3. The cross-sectional morphology of CS (A), CS-MRP I (B), CS-MRP II (C) and CS-MRP III (D) films. Fig. 4. FT-IR spectra of MRP powder (a), and CS (b), CS-MRP I (c), CS-MRP II (d) and CS-MRP III (e) films. Fig. 5. XRD patterns of MRP powder (a), and CS (b), CS-MRP I (c), CS-MRP II (d) and CS-MRP III (e) films. Fig. 6. The physical appearances of CS, CS-MRP I, CS-MRP II and CS-MRP III films. Fig. 7. UV-vis light transmittance of CS, CS-MRP I, CS-MRP II and CS-MRP III films. Fig. 8. TGA (A) and DTG (B) profiles of CS, CS-MRP I, CS-MRP II and CS-MRP III films. Fig. 9. DPPH radical scavenging activity of CS, CS-MRP I, CS-MRP II and CS-MRP III films. Each value represents mean ± SD of triplicates. Fig. 10. PV of oil packaged in CS, CS-MRP I, CS-MRP II and CS-MRP III film pouches. Different lower case letters indicate significantly different (p < 0.05). Fig. 11. TBARS value of oil packaged in CS, CS-MRP I, CS-MRP II and CS-MRP III film pouches. Different lower case letters indicate

56

significantly different (p < 0.05).

57

(A)

(C)

(B)

Fig. 1

58

(A)

(B)

(C)

(D)

Fig. 2

59

(A)

(B)

(C)

(D)

Fig. 3

60

(a) 1724

2927

(b)

820

1515 14421332 1279 1153 1637 1046

3298

Relative intensity

(c)

1639 1529

2926

1335 1403

558

1152

1065 1019

3255

1530

2925

559

1151

1639

(d)

1335 1404 1065 1019

3254 1632

(e) 2926

1336 1152

558

1532 1404

3247

1066 1018

1639 2925

1533

1336

1065

2000

3000

Wavenumber (cm-1)

Fig. 4

61

558

1405

3260

4000

1152

1018

1000

400

(a)

Relative intensity

(b)

(c)

(d)

(e)

5

20

35

50

2θ (°)

Fig. 5

62

65

80

CS film

CS-MRP II film

CS-MRP I film

Fig. 6

63

CS-MRP III film

100 CS film CS-MRP I film CS-MRP II film

80

Transmission (%)

CS-MRP III film 60

40

20

0 200

300

400

500

Wavelength (nm)

Fig. 7

64

600

700

(A)

100

Weight (%)

80

CS film CS-MRP I film CS-MRP II film CS-MRP III film

60

40

20

0

0

200

400

600

800

Temperature (°C)

0

(B)

DTG (%/min)

-2

CS film CS-MRP I film CS-MRP II film CS-MRP III film

-4

-6

-8 0

200

400

Temperature (°C)

Fig. 8

65

600

800

80 CS film

Scavenging ability (%)

CS-MRP I film CS-MRP II film

60

CS-MRP III film

40

20

0 0

1

3

2

Film equivalent (mg/mL)

Fig. 9

66

4

5

PV (mg cumene hydroperoxide/100 g oil)

12

a

c

c

d

10

e

d

f gh h

8

g

i

i

6

CS film CS-MRP I film CS-MRP II film CS-MRP III film

b

j

k m mm m

l

l

n n

4 2 0 0

7

14

21

28

35

Storage time (Days)

Fig. 10

67

gh

CS film CS-MRP I film CS-MRP II film CS-MRP III film

TBARS value (mg malonaldehyde/100 g oil)

3.0 a 2.5

b c d

2.0 f 1.5

1.0

n n n n

k k l

i j m

g

d g

h

i i k

l

0.5

0.0 0

7

14

21

Storage time (Days)

Fig. 11

68

28

35

e

69

Table 1 Color parameters including L, a, b, ΔE and WI of CS and CS-MRP films. a

b

ΔE

WI

68.51

± −0.33

± 4.20

± 26.70

± 68.23

0.22a

0.01d

0.06d

0.26d

0.21a

Films

L

CS film

CS-MRP film CS-MRP film CS-MRP film

I 59.30

± 1.40

± 13.04

± 32.70

± 57.23

0.47b

0.13c

0.47c

0.76c

0.31b

II 53.63

± 4.50

± 26.30

± 45.33

± 46.50

0.77c

0.15b

0.50b

0.35b

0.43c

III 45.04

± 11.02

± 42.43

± 63.08

± 29.70

1.00d

0.6da

0.78a

01.37a

1.36d

±

±

±

±

Values are expressed as mean ± SD (n = 3). Different lower case letters in the same column indicate significantly different (p < 0.05).

Table 2 Thicknesses, moisture contents, water solubility and WVP of CS and CS-MRP films. Films

Film

Moisture

Water

70

WVP

thickness

content (%)

solubility

(mm) CS film

(%)

0.065

± 27.62

± 18.21

0.006c

0.76a

0.29a

CS-MRP I 0.082

± 17.81

± 16.55

0.08b

0.46b

CS-MRP II 0.098

± 17.06

± 15.48

film

0.005a

0.57bc

0.20c

CS-MRP

0.102

± 16.37

± 14.53

III film

0.003a

0.14c

0.10d

film

(×10−10 g m−1 s−1 Pa−1)

0.005b

± 1.51 ± 0.03d

± 2.12 ± 0.06c

± 2.54 ± 0.17b

± 2.97 ± 0.19a

Values are expressed as mean ± SD (n = 10 for film thickness, and n = 3 for moisture content, water solubility and WVP). Different lower case letters in the same column indicate significantly different (p < 0.05).

Table 3 TS and EAB of CS and CS-MRP films. Films

TS (MPa)

EAB (%)

71

CS film

41.59 ± 1.10d 40.31 ± 0.62a

CS-MRP I film

44.60 ± 2.29c 36.04 ± 0.70b

CS-MRP II film

51.57 ± 1.15b 28.71 ± 1.15c

CS-MRP III film 58.21 ± 1.85a 23.54 ± 1.16d Values are expressed as mean ± SD (n = 6). Different lower case letters in the same column indicate significantly different (p < 0.05).

Table 4 Antimicrobial activity of CS and CS-MRP films against four foodborne pathogens. Diameter of inhibition zone (mm) Films

Salmonella

Staphylococcus aureus

Lis

CS film

Gram-negative CS-BPPE film Escherichia coli CS-TiO2-BPPE film 6.51 ± 0.41c C

Gram-positive

7.05 ± 0.24c B

7.55 ± 0.07c B

7.9

CS-MRP I film

7.18 ± 0.03bc C

7.56 ± 0.17bc BC

7.76 ± 0.09b B

8.4

CS-MRP II film

7.62 ± 0.06ab C

7.92 ± 0.08b C

8.11 ± 0.15b B

8.9

CS-MRP III film

8.49 ± 0.10a D

8.74 ± 0.11a C

9.10 ± 0.16a B

9.4

Values are expressed as mean ± SD (n = 3). Different lower case letters in the same column indicate significantly different (p < 0.05). Different capital letters in the same row indicate significantly different (p < 0.05). 72

73

Highlights Active packaging was prepared using mangosteen rind powder (MRP) and chitosan (CS). CS-MRP films had higher light barrier property and tensile strength than CS film. CS-MRP films showed stronger antioxidant and antimicrobial ability than CS film. CS-MRP film packaging increased the oxidative stability of soybean oil.

74