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Ultrason Sonochem
Ultrason Sonochem
Ultrasonics Sonochemistry
1350-4177
1873-2828
Elsevier

S1350-4177(24)00315-8
10.1016/j.ultsonch.2024.107067
107067
Original Research Article
Enhancement of zein-based films for mango preservation using high-intensity ultrasound and castor oil plasticization
Fan Xin fanxin2019@sust.edu.cn
⁎
Chang Lu
Pu Huayin
Zhao Jinghua
Wang Huan
Wang Yiyu
He Wenqiang
Huang JunRong
School of Food Science and Engineering, Shaanxi University of Science and Technology, Xi’ an 710021, Shaanxi, China
⁎ Corresponding author. fanxin2019@sust.edu.cn
14 9 2024
12 2024
14 9 2024
111 1070679 7 2024
5 9 2024
12 9 2024
© 2024 The Authors. Published by Elsevier B.V.
2024

https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Zein-based films exhibit high efficiency in ethylene adsorption. However, its brittleness limits the practical applications. To address this issue, this study synergizes the plasticizing effects of high-intensity ultrasound (HIU) and castor oil (CO) to reduce the brittleness of zein-based films. The plasticizing mechanism was demonstrated through the formation of new intermolecular hydrogen bonds and electrostatic interactions, as evidenced by fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. The tensile strength of 6 % CO-zein film increased eightfold. Additionally, the freshness of mangoes stored with 6 % CO-zein film significantly improved, extending their shelf life from 5 days to 15 days. Therefore, this study investigated the synergistic plasticization of zein-based films through the addition of CO, based on HIU. It also provides a theoretical basis for fruit packaging.

Keywords

Zein
Castor oil
High-intensity ultrasound
Plasticizing mechanism
Ethylene adsorption
Mango preservation
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pmc1 Introduction

Fruits are an essential component of the human diet due to their abundance of vitamins, minerals, and other trace elements [1]. According to statistics, the global fruit loss rate is as high as 40–50 % [2]. In particular, climacteric fruits (such as mangoes) are highly sensitive to ethylene in the postharvest environment, leading to rapid ripening and rotting. Therefore, there is a pressing need to develop eco-friendly and efficient fruit packaging materials to reduce fruit loss. Current packaging materials are predominantly petroleum-based, resulting in significant environmental pollution. Zein, a by-product of maize starch processing, exhibits excellent film-forming, biocompatible, and biodegradable characteristics, making it a promising candidate for the development of plastic substitutes [3]. Our research group has discovered that zein contains numerous sulfhydryl sites that can readily undergo a “click reaction” with ethylene, facilitating efficient ethylene adsorption and extending the shelf life of fruits [4], [5]. However, zein consists of nine parallel helical clusters [6], resulting in films with high brittleness [7], which limits their practical applications.

Currently, the mechanisms for reducing the brittleness of zein-based films can be categorized into two approaches. First, polyols rely on internal oxygen atoms to form new hydrogen bonds with zein, weakening the interactions within the zein to achieve a plasticizing effect [8]. Second, substances such as acids expose more side chains of amino acid residues in zein, enhancing intermolecular interactions and resulting in a plasticizing effect [9]. Based on these mechanisms, commonly used methods to reduce the brittleness of zein-based films include physical methods and plasticizers. Among these methods, high-intensity ultrasound (HIU) generates cavitation, which effectively promotes the unfolding of the zein structure and exposes hydrogen bonding sites, thereby achieving a plasticizing effect. Additionally, most researchers use plasticizers such as glycerol [10], oleic acid [11], and polyethylene glycol [12] to reduce the brittleness of zein-based films. When glycerol is combined with oleic acid, the tensile strength of zein-based films increases by 0.47 and 0.22-fold compared to using a single plasticizer [13]. Although the plasticizing effect has been improved, there is still a gap in terms of practical applications.

Therefore, this study synergizes the plasticizing effects of HIU and castor oil (CO) to reduce the brittleness of zein-based films (Fig. 1-A). Firstly, the structure of zein was stretched when treated with 400 W ultrasound for 15 min [14]. Secondly, CO, a bio-based plasticizer, contains polyol hydroxyl groups that provide additional hydrogen bonding sites [15]. Furthermore, CO's long fatty acid chains can effectively improve the hydrophobicity and thermal stability of zein-based films [16]. To date, no studies have reported on reducing the brittleness of zein-based films using CO. This study elucidated the plasticizing mechanism of zein-based films and explored their application in mango preservation by adsorbing ethylene (Fig. 1-B).Fig. 1 A: Preparation process of CO-zein films; B: CO-zein films applied to mango fresh-keeping packaging.

2 Materials and methods

2.1 Materials

Zein (BR 92 %) was obtained from Shanghai Yuanye Bio-Technology Co., Ltd.; ethanol (AR) and 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) were purchased from Tianjin Fuyu Fine Chemical Co. Ltd.; castor oil (CO, AR) was procured from Shanghai Macklin Biochemical Co., Ltd.; potassium bromide (AR) from Tianjin Opu Sheng Chemical Co., Ltd.; sodium chloride (AR) from Shanghai Experiment Reagent Co., Ltd.; ferrous sulfate heptahydrate (FeSO4·7H2O, AR) from Tianjin Kemao Chemical Reagent Co., Ltd.; calcium carbonate (CaCO3, AR) from Shanghai Macklin Biochemical Co., Ltd.; potassium hydroxide (KOH, AR) from Tianjin Fuyu Fine Chemical Co., Ltd.; and sodium dodecyl sulfate (SDS) from Kehao Biotechnology Co., Ltd. Fresh mangoes were sourced from the Xi'an Yurun fruit wholesale market.

2.2 Preparation of CO-zein films

A quantitative amount of zein powder was weighed, and the solvent chosen was 80 % v/v aqueous ethanol with a protein concentration of 25 wt%. This mixture was stirred at room temperature for 5 h until fully dissolved. The protein solution was then subjected to ultrasonic treatment at a power of 400 W for 15 min. Following ultrasound treatment, CO was added to the protein solution at volume fractions of 3 % to 15 %, and the mixture was stirred on a magnetic stirrer for 5 h at room temperature until homogeneous. The resulting solution was pipetted onto round Petri dishes and allowed to equilibrate and stand for 24 h at 25 °C and 75 % relative humidity. The CO-zein-based films were obtained after peeling off the films from the dishes. These films were named CO-zein, 0 %CO-zein, 3 %CO-zein, 6 %CO-zein, 9 %CO-zein, 12 %CO-zein, and 15 %CO-zein for subsequent testing.

2.3 Comprehensive analysis of plasticizing characterization

2.3.1 Mechanical properties

Mechanical properties were analyzed using a physical property analyzer from SMS (UK) with A/MTG preset probes. The testing parameters were as follows: the initial and middle test speeds were set at 1 mm/s, while the final test speed was set at 10 mm/s. The strain was set to 100 %, the trigger force to 10 g, and the return distance to 20 mm. Each test was repeated five times.

2.3.2 Fourier transform infrared spectroscopy (FTIR)

FTIR analysis was conducted using a Vertex 70 Fourier transform infrared spectrometer. A total of 32 scans were performed at a resolution of 400–4000 cm−1. The acquired spectra were analyzed using Origin 2021 and OMNIC 9.0 software [17].

2.3.3 Zeta potential

The zeta potential was measured following a slightly modified method described in the literature [18]. Before measurement, the CO-zein-forming solution was diluted 100 times using an 80 % v/v ethanol aqueous solution and pure CO. The measurement parameters included an instrument temperature of 25 °C and an equilibration time of 2 min.

2.4 Characterization of CO-zein films

2.4.1 Transmittance and whiteness

The sample was placed in a quartz cuvette, and the absorbance at wavelengths ranging from 280 to 800 nm was determined. Transmittance was calculated using the following formula:(1) Transmittance(%)=lgA/d

where A: absorbance, d: the thickness of CO-zein films (mm).

For whiteness, the CO-zein films were placed on an A4 paper for calibration. The L, a, and b values of the CO-zein films were recorded using a handheld colorimeter. Whiteness was calculated using the following formula:(2) W=100-[(100-L*)2+(a*)2+(b*)2]1/2

where L: brightness, a: red-green, b: yellow-blue.

2.4.2 Microtopography

Field emission scanning electron microscopy (FESEM) was used to observe the cross-sectional microtopography of the samples, with a test voltage of 20 kV.

2.4.3 Thermogravimetric analysis (TGA)

TGA was conducted by heating the samples from room temperature to 600 °C at a heating rate of 10 °C/min. The resulting weight loss curve was recorded [19].

2.4.4 Water vapor permeability (WVP), oxygen permeability (OP) and carbon dioxide permeability (CDP)

Conical flasks were filled with 3 g of anhydrous CaCO3 (for measuring WVP), 3 g of FeSO4·7H2O (for measuring OP), and 5 g of KOH (for measuring CDP). The films were then sealed at the mouth of the conical flasks and weighed as M1. Immediately afterward, they were placed in a desiccator containing saturated sodium chloride solution and weighed as M2 after being left to stand for 48 h. Each test was repeated three times.(3) X(WVP,OP,CDP)=(M2-M1)d/AtΔP

where d: film thickness, A: represents area, t: signifies placement time, ΔP: indicates the difference in partial pressures of water vapor, oxygen and carbon dioxide on both sides of the film under experimental conditions.

2.4.5 EDAX and total sulfydryl content

The chemical elements on the surface of the CO-zein films were determined using energy-dispersive X-ray (EDAX) analysis.

For the determination of total sulfhydryl content, an 80 % v/v ethanol aqueous solution was used to dilute the film-forming solution to a concentration of 2 mg/mL, following a slightly modified method [20]. Then, 0.5 mL of the diluted sample, 2 mL of urea-SDS solution, and 50 μL of DTNB (10 mmol/L) were mixed together and reacted at room temperature, protected from light for 15 min. The absorbance at λ = 412 nm was measured as A. The total sulfhydryl content was calculated using the following equation:(4) SH(n molmg-1Protein)=(A/ε)∙(D/C)

where A: absorbance, ε: molar absorption coefficient of 13600 m-1cm−1, D: dilution of 6, C: protein content of 2 mg/mL.

2.4.6 Ethylene adsorption experiment

The CO-zein films (50 mm × 50 mm) ware placed into a gas collection bag (Ningbo Hong Spectrum Instrument Technology Co., Ltd.). Then, the gas bag filled with a certain concentration (160 ± 10 ppm) of ethylene gas. After 24 h, the concentration of the ethylene in the bag was measured by the VOC detector (PGM-7340, RAE Systems, U A).

2.5 Application for mango preservation

2.5.1 Mango freshness test

Mangoes of uniform freshness were placed in a tray and set aside. Two pieces of 0 %-15 % CO-zein film were used to create a “pocket” using a sealing machine (Fig. 1-B). Fresh mangoes were placed inside and stored at room temperature (25 °C). Photographs were taken at intervals from day 0 to day 15.

2.5.2 Weight loss ratio

Both control and experimental mangoes were stored at room temperature and weighed daily from day 0 to day 15 to calculate the weight loss.

2.5.3 Skin and flesh firmness

The firmness of the mango flesh and skin was tested after 15 days using a physical property analyzer from SMS. The P/5 probe was selected, and the probe's front, middle, and back speeds were set at 1 mm/s. Each test was repeated five times.

2.6 Statistical analysis

The results of the tests were expressed as the mean and standard deviation and analyzed using ANOVA in SPSS 27 statistical software, with significance set at p < 0.05.

3 Results and discussion

3.1 Comprehensive analysis of plasticizing characteristics

As shown in Fig. 2-A, the 0 % CO-zein film broke when folded during the macroscopic crimp experiment. In contrast, the brittleness of the 3 %-15 % CO-zein films gradually decreased with the addition of CO, and no fractures occurred. Fig. 2-B demonstrates that the elongation at break of CO-zein films initially increased and then decreased, with the highest value observed in the 6 % CO-zein film (4.51 ± 1.01 %). The elongation at break of the 6 % CO-zein film was higher than that of glycerin-zein films (2.12 %), oleic acid-zein films (1.66 %), and glycerin-oleic acid-zein films (2.12 %) reported in the literature [13]. Furthermore, as depicted in Fig. 2-C, the tensile strength of the 6 % CO-zein film (16.98 ± 2.75 MPa) was significantly better than that of other experimental groups. Compared to the 0 % CO-zein film (2.10 ± 0.04 MPa), the tensile strength increased by more than 8-fold. It is due to the synergistic effect of CO and HIU, which enhances the intermolecular forces of zein, thereby increasing the tensile strength of the 6 % CO-zein film. Therefore, the optimized 6 % CO-zein film exhibited improved mechanical properties.Fig. 2 A: Fracture diagram of CO-zein films; B: Elongation at break of CO-zein films; C: Tensile strength of CO-zein films.

The synergistic plasticizing mechanism of HIU and CO is illustrated in Fig. 3. As shown in Fig. 3-A, with the addition of CO, the amide peak shifted from 1592.99 cm−1 to 1600.96 cm−1, indicating an increased distance between the amino group and the carbonyl group. This results in a decreased likelihood of intramolecular hydrogen bond formation. Meanwhile, the absorption peak of the –OH group shifted from 3483.24 cm−1 to 3424.41 cm−1, suggesting that the –OH group in CO forms new intermolecular hydrogen bonds with the amino acids in zein. This finding is consistent with the work of Zhang et al. [21]. These new intermolecular hydrogen bonds could tightly bind the protein molecular chains, enhancing the intermolecular forces and increasing resistance to external forces. Consequently, the mechanical properties of the CO-zein films were improved.Fig. 3 A: FITR of CO-zein films; B: Zeta potential of CO-zein films; C: Schematic diagram of plasticizing of CO-zein films.

As illustrated in Fig. 3-B, the zeta potential values of zein, CO, and 3 %-15 % CO-zein films were + 2.5 mV, −7.5 mV, and + 3.7 mV to + 2.7 mV, respectively. The change in zeta potential indicated the presence of electrostatic forces between CO and zein. Jing et al. also demonstrated the existence of electrostatic interactions between tannic acid and bovine lactoferrin by characterizing the zeta potential [22]. The increase in zeta potential value in the 15 % CO-zein film was primarily attributed to the excessive concentration of CO, leading to uneven dispersion within the solution.

In summary, the plasticizing mechanism of zein-based films can be described as follows: the structure of zein is stretched after HIU treatment, exposing internal hydrophobic groups. The brittleness of the zein-based film is reduced through the formation of new hydrogen bonds and electrostatic forces with castor oil, as shown in Fig. 3-C.

3.2 Characterization of CO-zein films

3.2.1 Transmittance and whiteness

Fig. 4-A shows the macroscopic view of CO-zein films with concentrations ranging from 0 % to 15 %. The surface of the CO-zein films appeared smooth and uniformly distributed to the naked eye, without any defects such as bubbles or impurities.Fig. 4 A: Sample picture of CO-zein films; B: ultraviolet–visible absorption spectra of CO-zein films; C: Whiteness of CO-zein films.

As shown in Fig. 4-B, the transmittance of all the films was close to zero in the UV region (280–340 nm). This is because zein contains a large number of aromatic amino acids, which have benzene ring structures capable of absorbing ultraviolet light [23]. Therefore, the prepared CO-zein films can effectively protect the product from UV damage. In the visible region (340–800 nm), the transmittance of CO-zein films was lower than that of 0 % CO-zein film. The FTIR results indicated the formation of stronger intermolecular hydrogen bonds within the film, altering the distance and arrangement between film molecules. Thus, when incident light enters the interior of the film, it increases both scattering and absorption of light during propagation, thereby reducing light transmission.

From Fig. 4-C, the whiteness of CO-zein films decreased with the addition of CO, primarily due to two reasons: firstly, after HIU treatment, the molecular structure of zein unfolded. The chromophore (tyrosine residues) contains conjugated structures that can absorb specific wavelengths of light, thereby altering the color of the film [24]. Additionally, the light yellow color of CO itself contributed to the decrease in whiteness of the CO-zein films.

3.2.2 Microtopography, TGA, and permeability

In Fig. 5-A, the cross-sectional structure of the CO-zein films is shown to become progressively smoother with the addition of CO, and the internal “gully” structure of the film gradually disappears, primarily attributed to the gradual unfolding of the protein structure.Fig. 5 A: Section electron microscopy of CO-zein films; B: Thermal stability of CO-zein films; C: Water vapor permeability of CO-zein films; D: Oxygen permeability of CO-zein films; E: Carbon dioxide permeability of CO-zein films.

According to Fig. 5-B, as the volume fraction of CO increased, the Td10 gradually increased. The Td10 of CO-zein films ranging from 0 % to 15 % CO increased from 249.32 °C to 267.69 °C. This improvement in thermal stability can be attributed to two main factors: firstly, the addition of CO, with a boiling point of 313 °C, enhances the thermal stability of the film. Secondly, FTIR and zeta potential analyses indicate the formation of stronger intermolecular hydrogen bonds and electrostatic forces in the CO-zein films. These results lead to a tighter and more robust intermolecular connection between CO and zein, making the films less susceptible to damage caused by changes in external temperature.

As demonstrated in Fig. 5-C, there was no significant difference in the WVP between films containing 0 % to 12 % CO-zein (P>0.05). The analysis aligns with the structural changes observed in Fig. 5-A, where the reduction in the “gully” structure enhances the mobility of water molecules, increasing their opportunity to pass through the film. As a result, the WVP of the CO-zein film increases, corroborated by findings from Easdani and Jiang et al. [3], [25].

It is well-known that the respiration rate of fruits can be moderated by decreasing the OP value and increasing the CDP value of the film, thereby delaying their post-ripening and extending the shelf life of the fruits [26]. As shown in Fig. 5-D, there was no significant difference in the OP values of CO-zein films with CO volume fractions ranging from 0 % to 9 % (P>0.05), all approximately 7.0 × 10-11 g·m·m−2·s−1·Pa−1. However, a notable increase in OP values occurs starting from CO-zein films with a CO volume fraction of 12 %. The addition of CO alters the “gully” structure of the films, straightening the path of oxygen passage, resulting in a shorter path length and an increase in OP value. Similar conclusions were drawn by Li et al. [27] in their study on chitosan composite films.

The CDP values of CO-zein films ranged from 1.2 × 10-12 g·m·m−2·s−1·Pa−1 to 1.6 × 10-12 g·m·m−2·s−1·Pa−1, with a less significant difference observed as the CO volume fraction increased (Fig. 5-E). This effect is mainly because as the number of gullies in the film decreases, the path length for carbon dioxide to pass through the CO-zein film shortens, leading to an increase in the CDP value. In practical applications, a CO-zein film with a low OP value and high CDP value should be selected to delay the post-ripening of fruits. After a comprehensive analysis of the OP and CDP values, a 6 % CO-zein film was identified as the optimal film for this study.

3.2.3 EDAX and total sulfhydryl content

EDAX is primarily employed for qualitative assessment of the elemental composition, chemical state, and distribution on the surface of CO-zein films. As illustrated in Fig. 6-A, the surface distribution of the prepared CO-zein films was uniform without caking, with the green/yellow color indicating the position of N and S elements. The results showed that the 0 % CO-zein film contained 16.82 % N and 2.01 % S, while the 6 % CO-zein film had 16.48 % N and 7.83 % S. This represents a 5.82 % increase in elemental S compared to the 0 % CO-zein film, suggesting that sulfur-containing amino acids are exposed on the zein surface due to the synergistic effect of HIU and CO.Fig. 6 A: EDAX of CO-zein films; B: Total sulfhydryl content of CO-zein films.

Furthermore, the total sulfhydryl content of CO-zein films was analyzed in Fig. 6-B. The total sulfhydryl content in the 0 % CO-zein film was approximately 30.51 ± 1.46 nmol/mg. After the addition of CO, the total sulfhydryl content initially increased and then decreased as the CO concentration increased. The content of total sulfhydryl groups in the 6 % CO-zein film reached its peak value of 37.79 ± 2.53 nmol/mg, which is an increase of 7.28 nmol/mg compared to the 0 % CO-zein film. This increase is primarily due to the dual action of ultrasound treatment and CO, which results in a more stretched protein structure, increased exposure of sulfur-containing amino acids, and consequently, an elevation in the total sulfhydryl content. Wang et al. [28] similarly demonstrated the internal structural unfolding of soy protein by discussing the increase in the total sulfhydryl content of soy protein.

3.3 Application for mango preservation

The visual changes in mango storage over 15 days are shown in Fig. 7-A. At 0 day, the skins of fresh mango samples were yellowish-green in color and did not show any black spots or damage. After 15 days of storage at room temperature, the control mangoes exhibited a large number of black spots and wrinkles due to water loss. In contrast, the experimental group had significantly fewer black spots, and the mangoes packed in the 6 % CO-zein film had the smallest area of black spots.Fig. 7 A: Place mango photos for different days; B: Fruit skin hardness of the mango after 15  days of storage; C: Flesh hardness of the mango after 15  days of storage; D: Weight loss rate of mango; E: Ethylene adsorption efficiency of CO-zein films.

Fig. 7-B and 7-C illustrate the variation in skin and flesh hardness of mangoes between the control and experimental groups. The control mango stored at room temperature for 15 days had the lowest skin and flesh hardness. In contrast, both the skin and flesh hardness of mangoes placed with CO-zein film showed an initial increase followed by a decrease. The highest values were observed in mangoes packed with 6 % CO-zein film, with weights of 887.78 ± 14.96 g and 446.20 ± 9.59 g, respectively. As shown in Fig. 7-D, the weight loss rate of the control mangoes was significantly higher than that of the experimental group during 5 to 15 days of storage. After 15 days, the samples with 0 %-9% CO-zein exhibited minimal weight loss, approximately 5 %.

From Fig. 7-E, the ethylene adsorption efficiency of the CO-zein films showed a tendency to increase and then decrease with the addition of CO. Specifically, the ethylene adsorption efficiency of the 6 % CO-zein film was 32.76 ± 1.61 mg·m−3·h−1, significantly higher than that of the control group (16.51 ± 4.44 mg·m−3·h−1). This increase is mainly due to the unfolding of the zein structure resulting from HIU, which exposes more sulfhydryl groups. Sulfhydryl groups in zein can readily undergo a “click reaction” with ethylene, facilitating efficient adsorption of ethylene and thereby prolonging the shelf life of the fruits. The excellent retention of freshness is attributed to the high efficiency of ethylene adsorption by the 6 % CO-zein film.

4 Conclusions

In this study, CO-zein films were developed using HIU and synergistic green plasticization with CO. The results showed that the optimized 6 % CO-zein film exhibited improved mechanical properties, thermal stability, air permeability, and ethylene adsorption. Mango preservation experiments demonstrated that CO-zein-based films could maintain the freshness of mangoes for at least 15 days. Mangoes wrapped in film samples containing 6 % CO-zein exhibited the lowest weight loss of 5 % and had the highest skin and flesh hardness, measuring 887.78 ± 14.96 g and 446.20 ± 9.59 g, respectively. In conclusion, CO-zein films represent advanced and sustainable packaging materials for fruit preservation.

CRediT authorship contribution statement

Xin Fan: Writing – review & editing, Investigation, Funding acquisition, Conceptualization. Lu Chang: Writing – original draft, Methodology, Data curation, Conceptualization. Huayin Pu: Investigation. Jinghua Zhao: Data curation. Huan Wang: Methodology. Yiyu Wang: Methodology. Wenqiang He: Software. JunRong Huang: Resources.

Declaration of competing interest

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

Acknowledgements

The authors gratefully acknowledge the financial support of this work by the National Natural Science Foundation of China (No. 32272380), the Key Research and Development Program of Shaanxi Province (No. 2024NC-YBXM-140), Scientific Research Program Funded by Shaanxi Provincial Education Department (No. 22JC007), and Young Talent Fund of Association for Science and Technology in Shaanxi (No. 20230225).
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References

1 Yang Z. Wu Q. Jiang F. Zheng D. Wu D. Chen K. Indirect treatment of plasma-processed air to decrease decay and microbiota of strawberry fruit caused by mechanical damage Food Chem. 408 2023 135225 10.1016/j.foodchem.2022.135225
2 Schmidt-Traub G. Obersteiner M. Mosnier A. Fix the broken food system in three steps Nature 569 2019 181 183 10.1038/d41586-019-01420-2 31068714
3 Easdani M. Ahammed S. Saqib M.N. Liu F. Zhong F. Engineering biodegradable controlled gelatin-zein bilayer film with improved mechanical strength and flexibility Food Hydrocoll. 148 2024 109430 10.1016/j.foodhyd.2023.109430
4 Fan X. Rong L. Li Y. Cao Y. Kong L. Zhu Z. Huang J. Fabrication of bio-based hierarchically structured ethylene scavenger films via electrospraying for fruit preservation Food Hydrocoll. 133 2022 107837 10.1016/j.foodhyd.2022.107837
5 Fan X. Zhao J. Rong L. Yang T. Wang H. Chang L. Huang J. Electrospinning of triple-component protein-polysaccharide nanofibers for fabrication of highly efficient ethylene scavenger films ACS Sustain. Chem. Eng. 11 2023 6352 6361 10.1021/acssuschemeng.3c00073
6 Argos P. Pedersen K. Marks M.D. Larkins B.A. A structural model for maize zein proteins J. Biol. Chem. 257 1982 9984 9990 10.1016/S0021-9258(18)33974-7 7107620
7 Nanda A. Pandey P. Rajinikanth P.S. Singh N. Revolution of nanotechnology in food packaging: Harnessing electrospun zein nanofibers for improved preservation - a review Int. J. Biol. Macromol. 260 2024 129416 10.1016/j.ijbiomac.2024.129416
8 Oliviero M. Verdolotti L. Di Maio E. Aurilia M. Iannace S. Effect of supramolecular structures on thermoplastic zein-lignin bionanocomposites J. Agric. Food Chem. 59 2011 10062 10070 10.1021/jf201728p 21834554
9 Shi K. Yu H. Lakshmana Rao S. Lee T.-C. Improved mechanical property and water resistance of zein films by plasticization with tributyl citrate J. Agric. Food Chem. 60 2012 5988 5993 10.1021/jf3001444 22568474
10 Sun Y. Liu Z. Zhang L. Wang X. Li L. Effects of plasticizer type and concentration on rheological, physico-mechanical and structural properties of chitosan/zein film Int. J. Biol. Macromol. 143 2020 334 340 10.1016/j.ijbiomac.2019.12.035 31812748
11 Turasan H. Barber E.A. Malm M. Kokini J.L. Mechanical and spectroscopic characterization of crosslinked zein films cast from solutions of acetic acid leading to a new mechanism for the crosslinking of oleic acid plasticized zein films Food Res. Int. 108 2018 357 367 10.1016/j.foodres.2018.03.063 29735068
12 Zhou L. Wang Y. Physical and antimicrobial properties of zein and methyl cellulose composite films with plasticizers of oleic acid and polyethylene glycol LWT 140 2021 110811 10.1016/j.lwt.2020.110811
13 Xu H. Zhang G. Synergistic effect of oleic acid and glycerol on Zein film plasticization J. Agric. Food Chem. 60 2012 10075 10081 10.1021/jf302940j 22989052
14 Fan X. Yang T. Li Y. Zhao J. Rong L. Feng L. Huang J. Fabrication of depolymerized zein films via high-intensity ultrasound for ethylene adsorption packaging Food Packag. Shelf Life 39 2023 101159 10.1016/j.fpsl.2023.101159
15 Zhong Y. Zhang T. Zhang W. Wang G. Zhang Z. Zhao P. Liu X. Li H. Antibacterial castor oil-based waterborne polyurethane/gelatin films for packaging of strawberries Food Packag. Shelf Life 36 2023 101055 10.1016/j.fpsl.2023.101055
16 Gulmez F. Yercan A. Kocaaga B. Guner F.S. pH-sensitive castor oil/PEG-based polyurethane films for drug delivery J. Drug Deliv. Sci. Technol. 61 2021 102160 10.1016/j.jddst.2020.102160
17 Gao J. Mao Y. Xiang C. Cao M. Ren G. Wang K. Ma X. Wu D. Xie H. Preparation of β-lactoglobulin/gum arabic complex nanoparticles for encapsulation and controlled release of EGCG in simulated gastrointestinal digestion model Food Chem. 354 2021 129516 10.1016/j.foodchem.2021.129516
18 Chen K. Zhang M. Mujumdar A.S. Wang H. Quinoa protein-gum Arabic complex coacervates as a novel carrier for eugenol: Preparation, characterization and application for minced pork preservation Food Hydrocoll. 120 2021 106915 10.1016/j.foodhyd.2021.106915
19 Zhou X. Cheng R. Wang B. Zeng J. Xu J. Li J. Kang L. Cheng Z. Gao W. Chen K. Biodegradable sandwich-architectured films derived from pea starch and polylactic acid with enhanced shelf-life for fruit preservation Carbohydr. Polym. 251 2021 117117 10.1016/j.carbpol.2020.117117
20 Hu H. Wu J. Li-Chan E.C.Y. Zhu L. Zhang F. Xu X. Fan G. Wang L. Huang X. Pan S. Effects of ultrasound on structural and physical properties of soy protein isolate (SPI) dispersions Food Hydrocoll. 30 2013 647 655 10.1016/j.foodhyd.2012.08.001
21 Zheng J. Gao Q. Tang C. Ge G. Zhao M. Sun W. Heteroprotein complex formation of soy protein isolate and lactoferrin: thermodynamic formation mechanism and morphologic structure Food Hydrocoll. 100 2020 105415 10.1016/j.foodhyd.2019.105415
22 Jing H. Huang X. Jiang C. Wang L. Du X. Ma C. Wang H. Effects of tannic acid on the structure and proteolytic digestion of bovine lactoferrin Food Hydrocoll. 117 2021 106666 10.1016/j.foodhyd.2021.106666
23 Yang Z. Liu H. Zhao J. Wang C. Li H. Wang X. Yang Y. Wu H. Gu Z. Li Y. UV absorption enhanced polydopamine coating Mater. Horiz. 2024 10.1039/D4MH00109E
24 Sun C. Dai L. He X. Liu F. Yuan F. Gao Y. Effect of heat treatment on physical, structural, thermal and morphological characteristics of zein in ethanol-water solution Food Hydrocoll. 58 2016 11 19 10.1016/j.foodhyd.2016.02.014
25 Jiang L. Jia F. Han Y. Meng X. Xiao Y. Bai S. Development and characterization of zein edible films incorporated with catechin/β-cyclodextrin inclusion complex nanoparticles Carbohydr. Polym. 261 2021 117877 10.1016/j.carbpol.2021.117877
26 Yuan L. Liu R. Zhou Y. Zhang R. Chen S. Yang Q. Gu Y. Han L. Yan B. Janus biopolymer nanocomposite coating with excellent antibacterial and water/oxygen barrier performance for fruit preservation Food Hydrocoll. 149 2024 109528 10.1016/j.foodhyd.2023.109528
27 Li S. Liu X. Zhang X. Fan L. Wang F. Zhou J. Zhang H. Preparation and characterization of zein-tannic acid nanoparticles/chitosan composite films and application in the preservation of sugar oranges Food Chem. 437 2024 137673 10.1016/j.foodchem.2023.137673
28 Wang H. Wang N. Chen X. Wu Z. Zhong W. Yu D. Zhang H. Effects of moderate electric field on the structural properties and aggregation characteristics of soybean protein isolate Food Hydrocoll. 133 2022 107911 10.1016/j.foodhyd.2022.107911
