Critically Review an Article

Critically evaluate the article

– Rationale/Objectives (Any novelty)

– Methodology used

– Any flaws and errors in experimental design/methodology

– Main finding

– Significance of findings

– Is the conclusion supported by the experimental results

Guidelines to Critically Review an Article

Abstract

• Does the abstract accurately describe the objectives and main results obtained?
• Does the abstract include information that cannot be substantiated by the results obtained?Keywords

Are the keywords appropriate? If not, what change would you suggest?

Introduction

• What was the objective of the study?
• Was the background information adequate to understand the aims of the study?
• On what prior observations was the research based on? What was and was not known at the time of the research?
• Methods

• What methods were used to accomplish this purpose? Are the methods valid for studying the problem?
• Check the methods for flaws. Is the experimental design sound? Is the sample selection adequate?
• Were the methods described in sufficient detail for others to repeat or extend the study?
• If standard methods were used, were adequate references given?
• If methods were modified, were the modifications described carefully?
• Have the authors indicated the reasons why particular procedures were used?
• Have the author specified the statistical procedures used? Are the statistical methods used appropriate?

Results

• What were the main findings of the study? Do the results obtained make sense?
• Did the results obtained answered the objectives stated in the introduction?
• Carefully examine the data presented in the tables and diagrams. Does the title or legend accurately describe the content.
• Are there discrepancies between the results in the text and those in the figures?

• Discussion
• Does the discussion address the objectives and hypothesis?
• Does the interpretation arise logically from the data or is it too far-fetched?
• If the objectives were not met, do the authors have any explanation?
• Did the research discover a new finding or created a new research technique?
• Significance of the work? Did the author mention wider implications of the findings?
• Have the flaws or shortcomings of the research been addressed?
• Did the reported observations or interpretations support or refute observations or interpretations made by other researchers?
• Did the author mention about any future research? Are there other research possibilities as suggested.

• Conclusion
• What was the conclusion of this research article?

• Is the conclusion consistent with the study results?
• References
• Did the authors cite appropriate papers for comments made? Are the references relevant and correctly formatted?
• Did the authors cite their own publications needlessly?

• Acknowledgments
• Could the source of the research funding have influenced the research topic or conclusions?

International Journal of Biological Macromolecules 235 (2023) 123889
Contents lists available at ScienceDirect
International Journal of Biological Macromolecules
journal homepage: www.elsevier.com/locate/ijbiomac
Biodegradable starch-based packaging films incorporated with
polyurethane-encapsulated essential-oil microcapsules for sustained
food preservation
Wei Wang a, Weiwei Zhang a, Lin Li a, Weijun Deng b, Ming Liu a, *, Jing Hu, Professor a, *
a
b
School of Perfume and Aroma Technology, Shanghai Institute of Technology, 201418 Shanghai, China
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 201418 Shanghai, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Polyurethane microcapsules
Essential oils
Starch-based packaging films
Food preservation
Novel starch-based packaging films with sustained antibacterial activity were successfully made by incorporating
polyurethane-encapsulated essential-oil microcapsules (EOs@PU) as an alternative synthetic preservative for
food preservation. Herein, three essential oils (EOs) were blended to make composite essential oils with a more
harmonious aroma and higher antibacterial ability and encapsulated into polyurethane (PU) to form EOs@PU
microcapsules based on interfacial polymerization. The morphology of the constructed EOs@PU microcapsules
was regular and uniform with an average size of approximately 3 μm, thus enabling high loading capacity (59.01
%). As such, we further integrated the obtained EOs@PU microcapsules into potato starch to prepare food
packaging films for sustained food preservation. Consequently, the prepared starch-based packaging films
incorporated with EOs@PU microcapsules had an excellent UV blocking rate (>90 %) and low cell toxicity.
Notably, the long-term release of EOs@PU microcapsules gave the packaging films a sustained antibacterial
ability, prolonging the shelf life of fresh blueberries and raspberries at 25 ◦ C (> 7 days). Furthermore, the
biodegradation rate of food packaging films cultured with natural soil was 95 % after 8 days, clarifying the
excellent biodegradability of the packaging films for environmental protection. As demonstrated, the biode­
gradable packaging films provided a natural and safe strategy for food preservation.
1. Introduction
Food spoilage during storage and transportation is exceptionally
intractable, and can lead to tremendous economic losses and severe
health hazards [1]. Food packaging films could mitigate mechanical
damage but fail to suppress bacterial growth. Therefore, it is necessary
to add extra preservatives into packaging films to enhance their anti­
bacterial properties for prolonged shelf life and improved food quality.
However, the safety hazards of synthetic antibacterial preservatives
pose a risk to the health and safety of consumers, thus leading re­
searchers to focus on alternatives such as natural preservatives [2,3]. In
particular, essential oils (EOs), possessing excellent antibacterial prop­
erties and being naturally safe, have been utilized in packaging films,
making them a potential alternate synthetic preservative [4–6]. How­
ever, using free EOs directly weakened the preservation ability because
the active ingredients of EOs suffered high volatility during a short
period and extreme instability to ambient conditions. Furthermore, the
heavy odor of free EOs could surpass the acceptable sensory quality of
protected foods [7–9]. With these problems in mind, encapsulation
technology was considered to eliminate the aforementioned shortcom­
ings. This technology is capable of encapsulating EOs to form capsules
separating the ambient conditions and even controlling their sustained
release. Currently, EO microcapsules have been used for food preser­
vation [10,11]. Hasheminejad reported the effects of chitosan-based EO
nanocapsules on the preservation of pomegranate arils, which showed
that the effectiveness of EO capsules is obviously better than that of free
EO [12]. Chang prepared EO microcapsules and tested them with lettuce
at 20 ◦ C to examine the preservative effect, which displayed no obvious
color difference after 5 days, thus indicating an excellent antimicrobial
effect [13]. Therefore, it is important to integrate EO capsules into fresh
foods to increase their shelf life.
Notably, the methods for adding EO capsules to fresh foods are also
critical for food quality and safety. Among them, packaging films are
able to prevent food pollution and extend shelf life by limiting the
* Corresponding authors.
E-mail addresses: mingliu@sit.edu.cn (M. Liu), hujing616@126.com (J. Hu).
https://doi.org/10.1016/j.ijbiomac.2023.123889
Received 1 December 2022; Received in revised form 24 February 2023; Accepted 26 February 2023
Available online 3 March 2023
0141-8130/© 2023 Elsevier B.V. All rights reserved.
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
substance exchange between food and the environment [14]. Wang et al.
[15] prepared composite films loaded with ginger essential oil with
long-lasting antioxidant capacity and antibacterial properties and
revealed the adverse effect of these films on the environment. However,
their actual ability to keep food fresh needs further verification.
Therefore, there is still a great challenge to prepare safe, effective, and
biodegradable packaging films incorporated with EO capsules possess­
ing high stability with the ability to preserve food. Potato starch has
been widely utilized as a film material due to its high biodegradability,
high safety, and cost-effectiveness, making it promising and practical for
food preservation [16]. Furthermore, the polyurethane-based (PU)
polymer synthesized by the TDI trimer (L75) possesses high mechanical
properties and thermal stability due to all of its benzene rings, and a high
degree of cross-linking due to all of its − CNO groups. Hence, PU is an
ideal polymer to encapsulate EOs with antimicrobial activity and
improve their stability [17].
In this study, to obtain a more harmonious aroma and higher anti­
bacterial effect [18], we chose tea tree essential oil, lavender essential
oil, and perilla leaf oil to make composite EOs, and then encapsulated
them into PU microcapsules to ensure loading capacity [17–22] and UV
blocking [23]. Subsequently, biocompatible and cost-effective [24,25]
potato starch was utilized to incorporate EOs@PU microcapsules
(Scheme 1). Consequently, we successfully made biodegradable and
effective food packaging films incorporated with EOs@PU microcap­
sules with sustained slow-release, advanced UV blocking, and high
stability for fresh food preservation.
Bio-Technology Co., Ltd. (Shanghai, China). Lennox Broth (LB) was
supplied by Qingdao Hope Bio-Technology Co., Ltd. (Qingdao, China).
Mouse embryonic fibroblast cells (NIH-3 T3 cells) were purchased from
Icell Bioscience Inc., Shanghai (Shanghai, China). Deionized water was
made by Shanghai Institute of Technology.
2.2. Preparation of the EOs@PU microcapsules
First, EOs (0.3 g, tea tree essential oil: lavender essential oil: perilla
leaf oil = 50:3:3 (w/w)), L75 (0.2 g), and Arabic gum aqueous solution
(4 mL, 5 wt%) were mixed and stirred evenly in the oil phase. The
mixture was stirred at 500 r min− 1 for 10 min and then treated with an
ultrasonic cell pulverizer for 10 min to obtain an oil/water emulsion.
Afterward, the emulsion was transferred to a 25 mL flask, stirred at
50 ◦ C, and then added to a xylitol aqueous solution (0.8 mL, 3.29 mol
L− 1). Then the temperature was raised to 70 ◦ C for 2 h. Subsequently, the
reaction solution was centrifuged, washed with water three times and
lyophilized for 12 h to obtain white EOs@PU microcapsules.
2.3. Preparation of starch-based packaging films
First, potato starch was dispersed in deionized water and stirred
evenly at 70 ◦ C for 30 min. Then, EOs@PU microcapsules were added
and stirred evenly. Finally, the mixture was poured into a mold, dried at
room temperature for 48 h, and then peeled to obtain the packaging
films.
2. Experimental section
2.4. Characterization of materials
2.1. Materials
2.4.1. Optical morphology
The optical morphology of the EOs@PU microcapsules was observed
by an LW600LJT instrument (Shanghai Cewei Photoelectricity Tech­
nology Co., Ltd., China) to collect photographs.
Tea tree essential oil, lavender essential oil, and perilla leaf oil were
provided by Jiangxi Senhai Natural Plant Oil Co., Ltd. (Jiangxi, China).
Arabic gum (pharmaceutical grade) and potato starch powder were
obtained from Shanghai Aladdin Bio-Chem Technology Co., Ltd.
(Shanghai, China). Xylitol (purity >99 %), glycerol, and absolute
ethanol were provided by Shanghai Titan Technology Co., Ltd.
(Shanghai, China). In addition, 2,4-Toluene diisocyanate tripolymer
(L75) was supplied by Bayer Co., Ltd. (Shanghai, China). Escherichia coli
(ATCC 8739) and Staphylococcus aureus (ATCC 6538) strains were pur­
chased from the China General Microbiological Culture Collection
Center (Beijing, China). Agar powder was supplied by Shanghai Yuanye
2.4.2. Dynamic light scattering
The particle size and size distribution of the EOs@PU microcapsules
were determined by a MASTERSIZER-3000 analyzer (Malvern Instru­
ment Company, UK) to obtain the size data of the EOs@PU
microcapsules.
2.4.3. Scanning electron microscopy
The microscopic morphology of the microcapsules was investigated
Scheme 1. EOs@PU microcapsules with high loading capacity were prepared to protect the essential oil as a natural antimicrobial agent, and subsequently, active
packaging film containing EOs@PU microcapsules was made to have great UV blocking and sustained food preservation abilities.
2
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
with an S-3400 N microscope (HITACHI Company, Japan). The prepared
EOs@PU microcapsules were dispersed in absolute ethanol. After ul­
trasonic dispersion, the EOs@PU microcapsules were dropped onto sil­
icon wafers. After drying, gold was sprayed on the EOs@PU
microcapsules to be observed by using the instrument.
According to the previous experimental method [32], the antibac­
terial ability of the packaging films was determined by E. coli and
S. aureus growth. Various kinds of active bacterial suspensions with a
concentration of approximately 106 CFU mL− 1 were prepared by using
LB liquid medium. Then, the control samples and the packaging films
were cut into small pieces of 20 × 20 × 2 mm3. Afterward, ultraviolet
lamp irradiation for 30 min is used for sterilization. Then, 5 mL normal
saline and 100 μL of the bacterial solution was added to the 10 mL
sterilized centrifuge tube, and a membrane was added for coculture for
12 h. Sterilized LB agar medium was injected into a sterile Petri dish, and
100 μL bacterial suspension after coculture was inoculated after the
culture solidified, and the bacterial liquid coated plate without coculture
but with a membrane was used as a control. Plates coated with bacterial
liquid were placed in an incubator and incubated at 37 ◦ C for 12 h, and
then the growth of colonies was observed.
2.4.4. Fourier transform infrared spectroscopy
Materials and films were measured by Fourier Transform Infrared
(FT-IR) spectroscopy in a Nicoletttin10 spectrometer (NIKOLI Instru­
ment Company, USA). All the above samples were mixed with potassium
bromide for tableting, and then their FT-IR spectra were collected by the
FT-IR spectrometer. Wavenumbers ranged from 4000 to 400 cm− 1 with
a resolution of 4 cm− 1.
2.4.5. Thermogravimetric analysis
The thermal stability of the corresponding samples was determined
by a Q5000IR analyzer (TA Company, USA). TGA was performed by
heating the specimens from 30 to 600 ◦ C in nitrogen flow (20 mL min− 1),
and the heating rate was 10 ◦ C min− 1.
2.8. Tensile testing
The tensile strength and elongation at the breaking points of the
packaging films were evaluated by using a universal testing machine
(SUN500, CARDANO AL CAMP company, Italy) operated at a crosshead
speed of 100 mm min− 1. The samples were cut into an oblong shape
(testing measure of 30 × 10 × 2 mm3) for tests.
2.5. Loading capacity
The loading capacity was determined according to the method
described in the literature [26]. The amount of EOs in the microcapsules
were determined by extraction with absolute ethanol as the solvent.
First, microcapsules (50 mg) were taken, and EOs were extracted by
ultrasonic cell crushing treatment with 5 mL absolute ethanol every time
for 10 min. The extraction process was repeated three times to ensure
complete extraction. After centrifugation, the supernatant was sonicated
for 10 min to ensure complete dissolution of the EOs. The supernatant
was analyzed by a UV–vis spectrophotometer (UV-1900, Shimadzu In­
struments (Suzhou) Co., Ltd., China), and the amount (g) of EOs in the
microcapsules was obtained according to the standard curve of EOs. The
extraction test was carried out 5 times to determine the average value.
The maximum absorption wavelength of the ethanol solution of the EOs
was 266 nm. Hence, ethanol solutions of EOs at concentrations of 0.04,
0.08, 0.12, 0.16, and 0.20 mg mL− 1 were prepared and their absorbance
at 266 nm was measured to fit the standard curve. The loading capacity
of EOs can be calculated according to the following formula:
LC(%) =
W2
× 100
W1
2.9. Transparency and UV blocking
Badges of the Shanghai Institute of Technology were placed on the
packaging films with EOs@PU microcapsules, and the transparency of
the films was observed. The absorbance of packaging films with
EOs@PU microcapsules was determined by spectrophotometry (UV1800, Shimadzu Instruments (Suzhou) Co., Ltd., China) within the
wavelength range of 200–900 nm. The UV blocking performance of
packaging films with EOs@PU microcapsules was determined by
investigating the wavelength band at 200–400 nm.
2.10. Sustained preservation
The EOs@PU microcapsules with different contents incorporated
into packaging films were used to preserve blueberries, raspberries, and
grapes at room temperature. The change in perishable fruits was
observed during storage to compare the antibacterial ability of the food
packaging films with different contents of EOs@PU microcapsules.
(1)
where LC(%) represents the content of the core material; W1 is the mass
of the microcapsules; and W2 is the weight of the EOs extracted from
broken microcapsules.
2.11. Cytotoxicity analysis
The Cell Counting Kit-8 (CCK-8) assay [33] was used to detect the
changes in cell viability when NIH-3T3 cells were cocultured with
packaging films with different contents of EOs@PU microcapsules for
24 h, to determine their cytotoxicity in vitro. First, the NIH-3T3 cells in
the logarithmic growth phase were counted, and the cell concentration
was adjusted. NIH-3T3 cells were inoculated into a 96-well plate at 4 ×
104 well − 1 and cultured overnight in a constant temperature incubator.
Afterward, the samples were sterilized with ultraviolet light for 30 min
and extracted with 1 mL complete medium at 37 ◦ C for 24 h. A complete
medium (100 μL well− 1) was added to the control group. The sample
group was added to 100 μL well− 1 leaching solution with 1 cm2 mL− 1
packaging films and cultured for 24 h. Finally, the medium was
removed. The wells were washed with PBS three times, and a culture
medium containing 10 % CCK-8, 5 % CO2 was added at 100 μL well − 1
and kept at 37 ◦ C in a constant temperature incubator for 2 h. The
absorbance at 450 nm was detected by a microplate reader (TECAN,
model: SPARK 10 M).
2.6. EOs release
EOs@PU microcapsules (50 mg) and EOs (30 mg, with the same mass
as loaded content) were placed at 25 ◦ C and 50 ◦ C, and samples were
taken at different time intervals to test the release rate of EOs by UV–vis
spectrophotometry. Furthermore, the packaging film with EOs@PU
microcapsules was cut into 40 mm × 40 mm squares, placed in 50 mL of
50 % (v/v) ethanol solution in a beaker, and then stored at 25 ◦ C for 11 h
(samples were taken every 30 min). Finally, the EOs emission was
measured at 266 nm by a UV–vis spectrophotometer. In addition, the
EOs release profiles were plotted using four mathematical models
[27–30].
2.7. Antibacterial property
The method of Gu et al. [31] was used to examine the antimicrobial
properties of the EOs@PU microcapsules. The antibacterial activity of
the control group, EOs, PU microcapsules, and EOs@PU microcapsules
against E. coli and S. aureus was tested.
2.12. Degradability experiment
Degradability was determined by measuring the weight loss of films
3
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
buried in the soil. The packaging films with EOs@PU microcapsules
were cut into small pieces of 50 × 20 × 2 mm3, weighed, tied to a corner
with thread, and buried approximately 15 cm below the soil surface. Soil
humidity was adjusted by spraying tap water on the soil once a day,
washed with distilled water several times to remove soil particles, and
dried at room temperature until they reached a constant weight. The
weight loss was then calculated using the following formula:
Weight loss (%) =
W0 − Wt
× 100
W0
scattering. As shown in Fig. 1a and b, the EOs@PU microcapsules
appeared as round particles with good dispersion and the particle size
was approximately 2.73 ± 0.65 μm. Subsequently, to further observe the
EOs@PU microcapsules morphology clear with more detail, the
EOs@PU microcapsules were observed by SEM, in which they had a
regular spherical shape and smooth surface, as presented in Fig. 1c.
These results suggested that the obtained EOs@PU microcapsules have
regular and uniform morphology with an average size of approximately
3 μm.
The structure of the prepared microcapsules was determined by FTIR to clarify whether the EOs were successfully encapsulated into PU
capsules. As shown in Fig. 1d, the absorption band at 3448 cm− 1 cor­
responds to O–H vibration, while the strong absorption bands at 2962
cm− 1 and 2876 cm− 1 come from C–H and -CH2- as well as asymmetric
-CH(CH3) stretching vibration and -CH(CH2)- symmetric and asym­
metric stretching vibration [34]. The strong bands at 1447 cm− 1 and
1377 cm− 1 are caused by -CH2 and -CH3 vibrations [35], and the vi­
bration of the C–C bond belonging to the hydrocarbon skeleton appears
below 1300 cm− 1. The strong absorption peak at 3389 cm− 1 belongs to
the stretching vibration of N–H, which means that there was a strong
hydrogen bond on the capsule wall. The absorption peak at 2273 cm− 1 is
the characteristic peak of the − CNO group. In addition, the content of
the − CNO group was determined by toluene-dibutylamine titration. The
results showed that L75 was completely involved in the reaction and no
harmful substance remained (Table S1). There was no − CNO group
absorption band at 2273 cm− 1 in the EOs@PU microcapsules, which
indicated that the polymerization of L75 and xylitol was completed and
a polyurethane capsule wall was formed. The outcome of FI-IR
confirmed that the EOs were successfully incorporated into PU
microcapsules.
To determine whether the thermal stability of the EOs was improved
after encapsulation, the thermal stability of the EOs, PU microcapsules,
and EOs@PU microcapsules was analyzed using thermogravimetric
analysis (TGA). The results clearly indicate that the EOs decomposed
before 92.5 ◦ C (Fig. 1e), which indicates their exceedingly poor thermal
(2)
where W0 is the initial weight of the sample; and Wt is the dry weight of
the sample after degradation in soil.
3. Results and discussion
3.1. Characterization of EOs@PU microcapsules
Tea tree essential oil, lavender essential oil, and perilla leaf oil were
blended in ratio, making the aroma harmonious, to prepare composite
essential oils (Fig. S1). In addition, the composite essential oils had a
synergistic antibacterial effect as shown in Fig. S2, which is consistent
with literature reports. Then, the composite EOs, L75, and Arabic gum
were mixed to form the oil phase, where L75 acted as the reactive
monomer and Arabic gum acted as the emulsifier. Afterward, the
aqueous solution of xylitol as the water phase was slowly added to the
above oil phase, which allowed the − CNO groups of L75 and the − OH
groups of xylitol to react at the oil/water interface. In particular, more
xylitol was added to allow the − CNO groups to react completely. After
centrifugation, the obtained product was washed three times with water
to remove excess xylitol. Finally, the EOs@PU microcapsules were ob­
tained by lyophilization.
First, to observe the overall morphology and size of the EOs@PU
microcapsules, the suspension of EOs@PU microcapsules was dispersed
in water and observed by optical microscopy and dynamic light
Fig. 1. Morphology of the constructed EOs@PU microcapsules. (a) Optical morphology of aqueous EOs@PU microcapsules (The scale bar is 10 μm); (b) Particle size
distribution of EOs@PU microcapsules; (c) SEM photograph of EOs@PU microcapsules; (d) FT-IR spectra of EOs, PU microcapsules, and EOs@PU microcapsules; (e,
f) TGA and DTG curves of EOs, PU microcapsules, and EOs@PU microcapsules. Note: The PU microcapsules successfully encapsulate the EOs with regular and
uniform morphology improved stability, and high loading capacity.
4
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
similar to the core content calculated by TGA of 59.01 %, which might
be due to the EOs@PU microcapsules requiring a freeze-drying process
before TGA, resulting in the loss of some EOs. The value of the loading
capacity of PU microcapsules was much higher than that reported in
previous literature [36,37]. The results clearly showed that the PU mi­
crocapsules successfully encapsulated the EOs with high loading ca­
pacity (Fig. S4).
stability. The main weight loss of PU microcapsules was 220–350 ◦ C
(Fig. 1f), indicating the decomposition of the microcapsule shell. The
weight loss of the EOs@PU microcapsules was 150–200 ◦ C, which cor­
responded to the loss of the compound EOs. Additionally, the loading
capacity was calculated from the ratio of the mass of the EOs to the mass
of the EOs@PU microcapsules as 59.01 %. TGA demonstrated that PU
microcapsules are capable of improving the thermal stability of free EOs.
To further quantify the loading capacity of the EOs@PU microcap­
sules, a UV–vis spectrophotometer was used to determine the EOs con­
tent. First, the absorbance of free EOs in the ethanol solution was
obtained to establish the standard curve illustrated in Fig. S3. Subse­
quently, the EOs in the PU microcapsules were extracted with ethanol,
and the calculated LC by the standard curve was 63.40 %, which was
3.2. Sustained release and antibacterial properties of EOs@PU
microcapsules
The release rates of free EOs and EOs@PU microcapsules were
investigated at 25 ◦ C and 50 ◦ C, respectively. Obviously, EOs volatilized
Fig. 2. Sustained-release behaviors and
long-term antibacterial properties of
EOs@PU microcapsules. (a) Release of
EOs and EOs@PU microcapsules at
different temperatures; (b) Photographs
and diameter (mm) of E. coli inhibition
circles treated with EOs and EOs@PU
microcapsules for 12 h, 24 h, 48 h; (c)
Photographs and diameter (mm) of
S. aureus inhibition circles treated with
EOs and EOs@PU microcapsules for 12 h,
24 h, 48 h. Note: EOs@PU microcapsules
have sustained release and excellent longterm antibacterial properties, making
them potentially applicable in food pres­
ervation techniques.
5
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
after being placed at 50 ◦ C for 24 h and were completely volatilized after
being placed at 25 ◦ C for 96 h (Fig. 2a), because free EOs are mainly
composed of volatile compounds. Comparably, sustained EOs release
was achieved due to the powerful protective effect of the EOs@PU mi­
crocapsules. EOs in the EOs@PU microcapsules gradually decreased
over time. After 6.5 d, the EOs content of PU microcapsules calculated
by TGA remained at 57.82 % and 33.91 % at 25 ◦ C and 50 ◦ C, respec­
tively, which verified that the EOs@PU microcapsules are capable of
sustained EOs release. Furthermore, the EOs release profiles were
plotted using four mathematical models, where the first-order model
had a better-fit degree than the others (Fig. S5), as shown in Table S2.
The first-order release model is the basic release model for sustainedrelease materials with a constant half-life. Consequently, the dynamic
release of EOs depended on their concentration in the solution.
E. coli and S. aureus are highly insidious to contaminate fresh foods
and endanger human health. Therefore, it is of great significance to
investigate the antimicrobial properties of the microcapsules. Conse­
quently, there were no antibacterial circles in the control and PU
microcapsule groups, while the diameter of the antibacterial circle of the
EOs@PU microcapsules decreased slightly with time. During the
experiment, the average diameter of the E. coli inhibition circle of the
EOs@PU microcapsules was at least 3.61 mm larger than that of the EOs,
indicating that the EOs@PU microcapsules had a significant and longlasting antibacterial effect on E. coli (Fig. 2b). In addition, the average
S. aureus inhibition circle diameter of the EOs@PU microcapsules before
24 h was smaller than that of the EOs. However, after incubation for 48
h, the diameter of the S.aureus inhibition circle of the EOs@PU micro­
capsules was 3.16 mm larger than that of the EOs (Fig. 2c). The above
analysis indicated that the EOs@PU microcapsules had excellent longterm antibacterial properties and sustained-release behaviors, which
made them promising to be used for food preservation.
3.3. Characterization of food packaging films with EOs@PU
microcapsules
After the potato starch solution was gelatinized, glycerin was added
as a plasticizer, followed by incorporation of the EOs@PU microcap­
sules. Then, the mixture was poured into the mold to prepare the
packaging films. The packaging films with EOs@PU microcapsules are
presented in Fig. 3a. All packaging films have different degrees of
transparency, and with the increase in the content of EOs@PU micro­
capsules, the transparency of the films decreases slightly [38]. Overall,
the packaging films with EOs@PU microcapsules have high trans­
parency, making them have potential for commercial use.
Certain mechanical properties can effectively maintain the integrity
of packaging films to bear the pressure generated during storage and
transportation. The film thickness is between 0.20 and 0.27 mm
(Table S3). The results of the tensile strength of the packaging films
showed packaging films with EOs@PU microcapsules had the lowest
tensile strength of 1.67 MPa (Fig. 3b), which is far higher than the tensile
strength of reported food packaging films (tensile strength of approxi­
mately 36 kPa) [39]. With the increase in the concentration of EOs@PU
microcapsules in the packaging films, their strength gradually decreases,
caused by the increase in additive content [40]. Furthermore, the out­
comes of the experiment showed that with the increase in EOs@PU
microcapsules in packaging films, the values of elongation at the
breaking point and fracture strength decreased (Table S3), which was
due to the increase in pore size of the films, leading to possible rupture
points [41]. Test analysis revealed that the packaging films have good
mechanical properties.
It is obvious that the infrared spectra of packaging films and pack­
aging films with EOs@PU microcapsules were basically the same
(Fig. 3c). There was a strong absorption peak at approximately 3344
cm− 1, which was the stretching vibration of -OH, and the antisymmetric
stretching vibration peak of -CH2 was at approximately 2934 cm− 1.
Additionally, 1650 cm− 1 represented the characteristic peak of tightly
Fig. 3. (a) Appearance of packaging films with different contents of EOs@PU microcapsules; (c) Thickness of packaging films with different contents of EOs@PU
microcapsules; (c) FT-IR spectra of EOs@PU microcapsules, packaging films, and packaging films with EOs@PU microcapsules; (d, e) TGA and DTG curves of
EOs@PU microcapsules, packaging films and packaging films with EOs@PU microcapsules. Note: EOs@PU microcapsules were successfully incorporated into
packaging films with high transparency and good mechanical properties.
6
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
bound water in starch, 1459 cm− 1 represented the bending vibration of
-CH2 in -CH2OH and 1352 cm− 1 represented the bending vibration of
-CH. Moreover, 1200–700 cm− 1 was the absorption peak of poly­
saccharides, and 1150 cm− 1 was the stretching vibration of C–O and
C–C bonds. Together, 1019 cm− 1 was mainly the stretching vibration of
the C–O bond and the bending vibration of C-OH. The packaging films
contained EOs@PU microcapsules, so there were characteristic peaks of
PU microcapsules. The absorption band at 2877 cm− 1 came from
asymmetric -CH(CH3) stretching vibration and -CH(CH2)- symmetric
and asymmetric stretching vibration (Gallart-Mateu, Largo-Arango,
Larkman, Garrigues, & de la Guardia, 2018). The characteristic peak
– O stretching vibration in the EOs
near 1714 cm− 1 was related to the C–
and PU microcapsules, and the characteristic peaks near 1540 cm− 1 and
1225 cm− 1 were related to the urethane bond. The vibration of the C–C
bond belonging to the hydrocarbon skeleton appeared below 1300
cm− 1. From the above analysis, it can be seen that packaging films with
EOs@PU microcapsules were successfully prepared and that the
EOs@PU microcapsules were not destroyed in the packaging film.
It was obvious that packaging films and packaging films with
EOs@PU microcapsules had the same initial decomposition tempera­
ture, and there were mainly three weight loss stages (Fig. 3d). In the first
stage from 30 ◦ C to 89 ◦ C, packaging films lost 6.47 % of their weight,
while packaging films with EOs@PU microcapsules lost 5.64 %. The
decomposition temperatures of the two films were almost the same
during the transition from the first stage to the second stage because the
quality change in this stage was due to the evaporation of bound water
in the films. In the second stage, the weight loss of the packaging films
was significant from 89 ◦ C to 240 ◦ C, with a 53.75 % decrease in residual
mass from 93.53 % to 39.78 %. Meanwhile, packaging films with
EOs@PU microcapsules decreased in residual mass by 51.11 % from
94.36 % to 43.25 % from 89 ◦ C to 210 ◦ C. The weight loss of packaging
films with EOs@PU microcapsules at this stage was mainly due to the
weight loss of partial starch and the loss of essential oils in microcap­
sules. In the third stage, packaging films lost weight from 240 ◦ C to
339 ◦ C, and continued to lose 24.23 %, while the weight of packaging
films with EOs@PU microcapsules decreased by 36.26 % from 210 ◦ C to
350 ◦ C. The mass reduction rate and decomposition temperature of the
packaging films were less than those of the packaging films with
EOs@PU microcapsules, which was due to the high weight loss tem­
perature of the PU microcapsules.
It can be observed from Fig. 3e that the first decomposition rate peak
of the two films was small, the second stage rate peak was wide and
short, and the third decomposition rate peak was narrow and high,
indicating that although the weight loss ratio of the films was large in
the second stage, the rate was slow, while the maximum weight loss rate
occurred in the third stage. The reason was that the decomposition rate
of the starch films was more thorough in the third stage after it was
decomposed into many short chains in the second stage, while the
microcapsules in the packaging films made its decomposition rate lower.
3.4. UV blocking ability and antibacterial properties of packaging films
with EOs@PU microcapsules
When the content of EOs@PU microcapsules in packaging films was
≥2 %, the UV absorption rate was ≥90 % (Fig. 4a), which indicated that
the packaging films with EOs@PU microcapsules had excellent UV
blocking ability. The addition of EOs@PU microcapsules into the
packaging films has a blocking effect on ultraviolet light (200–400 nm),
which is consistent with the results reported by Arrieta et al. [23]
Packaging films have an excellent UV blocking ability, which prevents
the oxidative breakdown of the active compounds in EOs [42].
The inhibition of E. coli and S. aureus by packaging films with
EOs@PU microcapsules is illustrated in Fig. 4b. Obviously, it can be seen
that the higher the content of EOs@PU microcapsules, the stronger the
antibacterial ability of packaging films. When the content of EOs@PU
microcapsules in packaging films was 2 %, the colony number of the two
bacteria was obviously reduced. Meanwhile, when the content of
EOs@PU microcapsules in packaging films was ≥8 %, there was almost
no inhibition. The main reason was that the higher content of the
EOs@PU microcapsules, the more EOs were released from the films,
which significantly changed the permeability of the cell membrane and
killed the bacteria [43], thus making packaging films with EOs@PU
microcapsules have an antibacterial effect. Similar to the release of EOs
in PU microcapsules, four mathematical models were used to draw the
release curve of EOs in the packaging film, of which the first-order model
had a better fit than other models (Fig. S6).
3.5. Sustained preservation of perishable fruit
Blueberries and raspberries were used for freshness experiments as
perishable fruits. With the extension of storage time, the water content
of the fruits gradually decreased, the surface state gradually deterio­
rated, and more antibacterial agents were released from packaging films
[44]. It may be that microcapsule packaging films can effectively delay
the ripening process of fruits [45]. The fruits remained fresher with
increasing EO@PU microcapsule content in the films. The packaging
films with 8 % content of EOs@PU microcapsules could prolong the
shelf life of blueberries and raspberries for 7 d (Fig. 5) at room tem­
perature, therefore, packaging films incorporated with EOs@PU mi­
crocapsules have a huge positive effect on delaying perishable fruit
decay. Simultaneously, the grapes did not decay after 10 d storage
(Fig. S7) at room temperature. Moreover, the weight loss test (Fig. S8a),
sensory evaluation (Fig. S8b), and biological evaluation (Fig. S8c and
Fig. S8d) during grape storage proved that 8 % content of EOs@PU
microcapsules in the packaging film had the best effect on maintaining
the freshness of the fruit. Using packaging films to preserve fruit at room
Fig. 4. Excellent UV blocking ability and antibacterial properties of packaging films with EOs@PU microcapsules is shown. (a) UV–vis transmittance spectra of
packaging films with different contents of EOs@PU microcapsules; (b) Antibacterial properties of packaging films with different contents of EOs@PU microcapsules.
Note: Packaging films with EOs@PU microcapsules have excellent UV blocking ability and good antibacterial properties.
7
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
Fig. 6a. Therefore, packaging films with EOs@PU microcapsules are
considered to be biosecure. Furthermore, to verify the environmental
friendliness of the packaging films, degradation experiments were con­
ducted. The outdoor natural soil embedding of packaging films was
measured by weight loss of the films over 8 d as illustrated in Fig. 6b.
The mass loss of all films was approximately 50 % on the second day of
degradation, but not >75 % on the fourth day of degradation, therefore
the degradation rate of packaging films slowed down overtime. This may
be due to the interaction of amylose and amylopectin in the gelatini­
zation process of starch films to form a three-dimensional network
structure. In the early stage of degradation in soil, the network structure
was destroyed, and in the later stage, each starch segment was degraded.
Although the degradation rate of packaging films with EOs@PU mi­
crocapsules slows down with time, the mass loss of all kinds of pack­
aging films exceed 95 % on the 8th day of degradation, which is much
higher than that of biodegradable food packaging materials previously
reported.25 This shows that packaging films with EOs@PU microcap­
sules have good soil degradability, making them a potential sustainable
material.
4. Conclusions
In this work, EOs@PU microcapsules were successfully prepared by
interfacial polymerization and subsequently incorporated into pack­
aging films. The obtained EOs@PU microcapsules were morphologically
uniform and had regular spherical shape with an average size of
approximately 3 μm, thus giving the capsules a high loading capacity
and sustained release behavior. In particular, both the EOs@PU micro­
capsules and the packaging films with EOs@PU microcapsules had
excellent and prolonged antibacterial activity against E. coli and
S. aureus, thus giving them the ability to preserve perishable fruit.
Moreover, the packaging films with EOs@PU microcapsules have good
mechanical properties, advanced UV blocking, favorable biosecurity,
and excellent biodegradability for preservation of fresh fruit. As
demonstrated, it is highly applicable to incorporate natural antibacterial
essential oil delivery systems with sustainable packaging films as a
sustainable food preservation technique commercially. In addition, it
provides a general approach to fabricating other active ingredient de­
livery systems with sustained release performance by interfacial poly­
merization. However, there is no current regulation of polyurethane as a
food packaging material.
Fig. 5. Sustained preservation of blueberries and raspberries treated with
packaging films with no treatment, treatment with 0 % EOs@PU microcapsules
and packaging films with 8 % EOs@PU microcapsules for 0 d, 1 d, 2 d, 3 d, 5 d,
7 d. Note: Packaging films with EOs@PU microcapsules have low cytotoxicity
and sustained fruit preservation.
temperature is better than that reported in the literature [46,47] and
even comparable to the effectiveness of preserving fruit by refrigeration.
3.6. Biosecurity and biodegradation of packaging films with EOs@PU
microcapsules
To verify that the packaging films prepared in this work are harmless
to humans, cytotoxicity experiments were conducted by the CCK-8
method to test the effect of packaging films on the cell activity and
proliferation of NIH-3 T3 cells. With varying contents of EOs@PU mi­
crocapsules in packaging films, cell viability was ≥60 % as presented in
Fig. 6. Biosecurity and biodegradation of packaging films incorporated with EOs@PU microcapsules. (a) Effect of EOs@PU microcapsule content in packaging films
on NIH-3 T3 cell viability (**p ≤ 0.01); (b) Soil biodegradability of packaging films with different contents of EOs@PU microcapsules. Note: Packaging films with
EOs@PU microcapsules have excellent biodegradability as well as biosafety in the environment.
8
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
CRediT authorship contribution statement
[11] F. Montisci, P.P. Mazzeo, C. Carraro, M. Prencipe, P. Pelagatti, F. Fornari,
F. Bianchi, M. Careri, A. Bacchi, Dispensing essential oil components through
cocrystallization: sustainable and smart materials for food preservation and
agricultural applications, ACS Sustain. Chem. Eng. 10 (2022) 8388–8399, https://
doi.org/10.1021/acssuschemeng.2c01257.
[12] N. Hasheminejad, F. Khodaiyan, The effect of clove essential oil loaded chitosan
nanoparticles on the shelf life and quality of pomegranate arils, Food Chem. 309
(2020), 125520, https://doi.org/10.1016/j.foodchem.2019.125520.
[13] Y. Chang, I. Choi, A.R. Cho, J. Han, Y. Chang, I. Choi, A.R. Cho, J. Han, Reduction
of Dickeya chrysanthemi on fresh-cut iceberg lettuce using antimicrobial sachet
containing microencapsulated oregano essential oil, LWT Food Sci. Technol. 82
(2017) 361–368, https://doi.org/10.1016/j.lwt.2017.04.043.
[14] J. Chen, M. Zheng, K.B. Tan, J. Lin, M. Chen, Y. Zhu, Development of xanthan
gum/hydroxypropyl methyl cellulose composite films incorporating tea
polyphenol and its application on fresh-cut green bell peppers preservation, Int. J.
Biol. Macromol. 211 (2022) 198–206, https://doi.org/10.1016/j.
ijbiomac.2022.05.043.
[15] H.H. Wang, M.Y. Li, Z.Y. Dong, T.H. Zhang, Q.Y. Yu, Preparation and
characterization of ginger essential oil microcapsule composite films, Foods 10
(2021) 2268, https://doi.org/10.3390/foods10102268.
[16] C. Cai, R. Ma, M. Duan, Y. Deng, T. Liu, D. Lu, Effect of starch film containing
thyme essential oil microcapsules on physicochemical activity of mango, LWT Food
Sci. Technol. 131 (2020), 109700, https://doi.org/10.1016/j.lwt.2020.109700.
[17] G. Cui, J. Wang, X. Wang, W. Li, X. Zhang, Preparation and properties of narrowly
dispersed polyurethane nanocapsules containing essential oil via phase inversion
emulsification, J. Agric. Food Chem. 66 (2018) 10799–10807, https://doi.org/
10.1021/acs.jafc.8b02406.
[18] S. Ayari, S. Shankar, P. Follett, F. Hossain, M. Lacroix, Potential synergistic
antimicrobial efficiency of binary combinations of essential oils against Bacillus
cereus and paenibacillus amylolyticus-part A, Microb. Pathog. 141 (2020), 104008,
https://doi.org/10.1016/j.micpath.2020.104008.
[19] E. Koh, N.K. Kim, J. Shin, Y.W. Kim, Polyurethane microcapsules for self-healing
paint coatings, RSC Adv. 4 (2014) 16214–16223, https://doi.org/10.1039/
C4RA00213J.
[20] E. Koh, S. Lee, J. Shin, Y.W. Kim, Renewable polyurethane microcapsules with
isosorbide derivatives for self-healing anticorrosion coatings, Ind. Eng. Chem. Res.
52 (2013) 15541–15548, https://doi.org/10.1021/ie402505s.
[21] E. Koh, S. Park, Self-anticorrosion performance efficiency of renewable dimer-acidbased polyol microcapsules containing corrosion inhibitors with two triazole
groups, Prog. Org. Coat. 109 (2017) 61–69, https://doi.org/10.1016/j.
porgcoat.2017.04.021.
[22] Y. Xu, L. Wang, Y. Tong, S. Xiang, X. Guo, J. Li, H. Gao, X. Wu, Study on the
preparation, characterization, and release behavior of carbosulfan/polyurethane
microcapsules, J. Appl. Polym. Sci. 133 (2016) 43844, https://doi.org/10.1002/
app.43844.
[23] M.P. Arrieta, V. Sessini, L. Peponi, Biodegradable poly(ester-urethane)
incorporated with catechin with shape memory and antioxidant activity for food
packaging, Eur. Polym. J. 94 (2017) 111–124, https://doi.org/10.1016/j.
eurpolymj.2017.06.047.
[24] M. Ghasemlou, N. Aliheidari, R. Fahmi, S. Shojaee-Aliabadi, B. Keshavarz, M.
J. Cran, R. Khaksar, Physical, mechanical and barrier properties of corn starch
films incorporated with plant essential oils, Carbohydr. Polym. 98 (2013)
1117–1126, https://doi.org/10.1016/j.carbpol.2013.07.026.
[25] M. Li, T. Witt, F. Xie, F.J. Warren, P.J. Halley, R.G. Gilbert, Biodegradation of
starch films: the roles of molecular and crystalline structure, Carbohydr. Polym.
122 (2015) 115–122, https://doi.org/10.1016/j.carbpol.2015.01.011.
[26] Y.B. Chong, H. Zhang, C.Y. Yue, J. Yang, Fabrication and release behavior of
microcapsules with double-layered shell containing clove oil for antibacterial
applications, ACS Appl. Mater. Interfaces 10 (2018) 15532–15541, https://doi.
org/10.1021/acsami.8b05467.
[27] H. Huang, T. Belwal, X. Lin, J. Limwachiranon, L. Zou, Z. Luo, Novel bind-thenrelease model based on fluorescence spectroscopy analysis with molecular docking
simulation: new insights to zero-order release of arbutin and coumaric acid, Food
Hydrocoll. 112 (2021), 106356, https://doi.org/10.1016/j.foodhyd.2020.106356.
[28] S. Jafari, M. Soleimani, M. Badinezhad, Application of different mathematical
models for further investigation of in vitro drug release mechanisms based on
magnetic nano-composite, Polym. Bull. 79 (2022) 1021–1038, https://doi.org/
10.1007/s00289-021-03537-9.
[29] I.Y. Wu, S. Bala, N. Škalko-Basnet, M.P. di Cagno, Interpreting non-linear drug
diffusion data: utilizing korsmeyer-peppas model to study drug release from
liposomes, Eur. J. Pharm. Sci. 138 (2019), 105026, https://doi.org/10.1016/j.
ejps.2019.105026.
[30] W. Zhang, X.C. Wang, J.J. Wang, L.L. Zhang, Drugs adsorption and release
behavior of collagen/bacterial cellulose porous microspheres, Int. J. Biol.
Macromol. 140 (2019) 196–205, https://doi.org/10.1016/j.ijbiomac.2019.08.139.
[31] R. Gu, H. Yun, L. Chen, Q. Wang, X. Huang, Regenerated cellulose films with
amino-terminated hyperbranched polyamic anchored nanosilver for active food
packaging, ACS Appl. Bio. Mater. 3 (2020) 602–610, https://doi.org/10.1021/
acsabm.9b00992.
[32] J. Hu, J. Zhang, L. Li, X. Bao, W. Deng, K. Chen, Chitosan-coated organosilica
nanoparticles as a dual responsive delivery system of natural fragrance for axillary
odor problem, Carbohydr. Polym. 269 (2021), 118277, https://doi.org/10.1016/j.
carbpol.2021.118277.
[33] P. Baipaywad, Y. Kim, J.S. Wi, T. Paik, H. Park, Size-controlled synthesis,
characterization, and cytotoxicity study of monodisperse poly(dimethylsiloxane)
Wei Wang: Conceptualization, Methodology, Investigation, Soft­
ware, Formal analysis, Writing – original draft, Writing – review &
editing. Weiwei Zhang: Methodology, Investigation, Validation. Lin Li:
Resources, Supervision. Weijun Deng: Resources, Supervision. Ming
Liu: Supervision, Investigation, Visualization. Jing Hu: Resources, Su­
pervision, Funding acquisition, Conceptualization, Data curation,
Writing – review & editing.
Declaration of competing interest
All authors have seen and approved the final version of the manu­
script being submitted. We warrant that the article is the authors’ orig­
inal work, hasn’t received prior publication and isn’t under consideration
for publication elsewhere.
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. The authors declare no competing
financial interest.
Acknowledgments
Financial supports from National Natural Science Foundation of
China (22078196 & 22278268), Shanghai Shuguang Talent Project
(19SG52), Shanghai Natural Science Foundation (22ZR1460400) are
appreciated.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.ijbiomac.2023.123889.
References
[1] S. Jung, Y. Cui, M. Barnes, C. Satam, S. Zhang, R.A. Chowdhury,
A. Adumbumkulath, O. Sahin, C. Miller, S.M. Sajadi, L.M. Sassi, Y. Ji, M.R. Bennett,
M. Yu, J. Friguglietti, F.A. Merchant, R. Verduzco, S. Roy, R. Vajtai, J.C. Meredith,
J.P. Youngblood, N. Koratkar, M.M. Rahman, P.M. Ajayan, Multifunctional bionanocomposite coatings for perishable fruits, Adv. Mater. 32 (2020) 1908291,
https://doi.org/10.1002/adma.201908291.
[2] S. Ahmed, D.E. Sameen, R. Lu, R. Li, J. Dai, W. Qin, Y. Liu, Research progress on
antimicrobial materials for food packaging, Crit. Rev. Food Sci. Nutr. 62 (2022)
3088–3102, https://doi.org/10.1080/10408398.2020.1863327.
[3] A. Lather, S. Sharma, A. Khatkar, Aesculin based glucosamine-6-phosphate
synthase inhibitors as novel preservatives for food and pharmaceutical products:
in-silico studies, antioxidant, antimicrobial and preservative efficacy evaluation,
BMC Chemistry 15 (2021) 45, https://doi.org/10.1186/s13065-021-00769-8.
[4] N. Khorshidian, M. Yousefi, E. Khanniri, A.M. Mortazavian, Potential application of
essential oils as antimicrobial preservatives in cheese, Innov. Food Sci. Emerg.
Technol. 45 (2018) 62–72, https://doi.org/10.1016/j.ifset.2017.09.020.
[5] B. Fathi-Achachlouei, N. Babolanimogadam, Y. Zahedi, Influence of anise
(Pimpinella anisum L.) essential oil on the microbial, chemical, and sensory
properties of chicken fillets wrapped with gelatin film, food sciTechnol. Int. 27
(2020) 123–134, https://doi.org/10.1177/1082013220935224.
[6] S.M.B. Hashemi, A. Mousavi Khaneghah, Characterization of novel basil-seed gum
active edible films and coatings containing oregano essential oil, Prog. Org. Coat.
110 (2017) 35–41, https://doi.org/10.1016/j.porgcoat.2017.04.041.
[7] H. Cui, M. Bai, L. Lin, Plasma-treated poly(ethylene oxide) nanofibers containing
tea tree oil/beta-cyclodextrin inclusion complex for antibacterial packaging,
Carbohydr. Polym. 179 (2018) 360–369, https://doi.org/10.1016/j.
carbpol.2017.10.011.
[8] F. Gao, H. Zhou, Z. Shen, G. Zhu, L. Hao, H. Chen, H. Xu, X. Zhou, Long-lasting
anti-bacterial activity and bacteriostatic mechanism of tea tree oil adsorbed on the
amino-functionalized mesoporous silica-coated by PAA, Colloids Surf. B 188
(2020), 110784, https://doi.org/10.1016/j.colsurfb.2020.110784.
[9] M. Subbuvel, P. Kavan, Preparation and characterization of polylactic acid/
fenugreek essential oil/curcumin composite films for food packaging applications,
Int. J. Biol. Macromol. 194 (2022) 470–483, https://doi.org/10.1016/j.
ijbiomac.2021.11.090.
[10] F. Froiio, A. Mosaddik, M.T. Morshed, D. Paolino, H. Fessi, A. Elaissari, Edible
polymers for essential oils encapsulation: application in food preservation, Ind.
Eng. Chem. Res. 58 (2019) 20932–20945, https://doi.org/10.1021/acs.
iecr.9b02418.
9
W. Wang et al.
International Journal of Biological Macromolecules 235 (2023) 123889
[41] M. Cheng, J. Wang, R. Zhang, R. Kong, W. Lu, X. Wang, Characterization and
application of the microencapsulated carvacrol/sodium alginate films as food
packaging materials, Int. J. Biol. Macromol. 141 (2019) 259–267, https://doi.org/
10.1016/j.ijbiomac.2019.08.215.
[42] L.J. Li, P. Hong, F. Chen, H. Sun, Y.F. Yang, X. Yu, G.L. Huang, L.M. Wu, H. Ni,
Characterization of the aldehydes and their transformations induced by UV
irradiation and air exposure of white guanxi honey pummelo (Citrus grandis (L.)
Osbeck) essential oil, J. Agric. Food Chem. 64 (2016) 5000–5010, https://doi.org/
10.1021/acs.jafc.6b01369.
[43] D. Yu, J. Wang, X. Shao, F. Xu, H. Wang, Antifungal modes of action of tea tree oil
and its two characteristic components against Botrytis cinerea, J. Appl. Microbiol.
119 (2015) 1253–1262, https://doi.org/10.1111/jam.12939.
[44] H. Lee, S.C. Min, Antimicrobial edible defatted soybean meal-based films
incorporating the lactoperoxidase system, LWT Food Sci. Technol. 54 (2013)
42–50, https://doi.org/10.1016/j.lwt.2013.05.012.
[45] S. Rokayya, F. Jia, Y. Li, X. Nie, M. Helal, Application of nano-titanum dioxide
coating on fresh Highbush blueberries shelf life stored under ambient temperature,
LWT Food Sci. Technol. 137 (2020), 110422, https://doi.org/10.1016/j.
lwt.2020.110422.
[46] I. Khalifa, A.E.M. Hamdy, B. Hassan, A.S. Soliman, Effect of Chitosanâ olive oil
processing residues coatings on keeping quality of Coldâ storage strawberry
(Fragaria ananassavar. Festival), J. Food Qual. 39 (2016) 504–515, https://doi.
org/10.1111/jfq.12213.
[47] C. Zhang, W. Li, B. Zhu, H. Chen, H. Chi, L. Li, Y. Qin, J. Xue, The quality
evaluation of postharvest strawberries stored in nano-ag packages at refrigeration
temperature, Polymers 10 (2018) 894, https://doi.org/10.3390/polym10080894.
nanoparticles, J. Ind. Eng. Chem. 53 (2017) 177–182, https://doi.org/10.1016/j.
jiec.2017.04.023.
[34] D. Gallart-Mateu, C.D. Largo-Arango, T. Larkman, S. Garrigues, M. de la Guardia,
Fast authentication of tea tree oil through spectroscopy, Talanta 189 (2018)
404–410, https://doi.org/10.1016/j.talanta.2018.07.023.
[35] S. Tankeu, I. Vermaak, G. Kamatou, A. Viljoen, Vibrational spectroscopy as a rapid
quality control method for Melaleuca alternifolia cheel (tea tree oil), Phytochem.
Anal. 25 (2014) 81–88, https://doi.org/10.1002/pca.2470.
[36] N. Azizi, Y. Chevalier, M. Majdoub, Isosorbide-based microcapsules for cosmetotextiles, Ind. Crop. Prod. 52 (2014) 150–157, https://doi.org/10.1016/j.
indcrop.2013.10.027.
[37] X. Bai, J. Li, C. Wang, Q. Ren, Thermo-expandable microcapsules with
polyurethane as the shell, J. Polym. Res. 27 (2020) 185, https://doi.org/10.1007/
s10965-020-02160-y.
[38] Z.J. Zhang, N. Li, H.Z. Li, X.J. Li, J.M. Cao, G.P. Zhang, D.L. He, Preparation and
characterization of biocomposite chitosan film containing Perilla frutescens (L.)
Britt. essential oil, Ind. Crops Prod. 112 (2018) 660–667, https://doi.org/10.1016/
j.indcrop.2017.12.073.
[39] T. Min, Z. Zhu, X. Sun, Z. Yuan, Y. Wen, Highly efficient antifogging and
antibacterial food packaging film fabricated by novel quaternary ammonium
chitosan composite, Food Chem. 308 (2019), 125682, https://doi.org/10.1016/j.
foodchem.2019.125682.
[40] A. Cagri, Z. Ustunol, E.T. Ryser, Antimicrobial, mechanical, and moisture barrier
properties of low pH whey protein-based edible films containing p-aminobenzoic
or sorbic acids, J. Food Sci. 66 (2001) 865–870, https://doi.org/10.1111/j.13652621.2001.tb15188.x.
10