Development and characterization of starch films prepared by extrusion blowing: The synergistic plasticizing effect of water and glycerol

doi:10.1016/j.lwt.2021.111820

LWT

Volume 148, August 2021, 111820

https://doi.org/10.1016/j.lwt.2021.111820 Get rights and content

Highlights

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Starch films were prepared by extrusion blowing.
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There were two stages for synergistic plasticizing effect of water and glycerol.
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The addition of 15% G-15% W co-plasticizers is optimal for extrusion film blowing.
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The introduction of water can greatly reduce the production cost of starch films.

Abstract

Herein, we have investigated the synergistic plasticizing effect of water (W) and glycerol (G) on the physicochemical and structural properties of starch-based films prepared by extrusion blowing. Fourier transform infrared spectroscopy (FT-IR) revealed that glycerol could act as a typical plasticizer in the presence of sufficient amounts of water (approximately 15%). All the films exhibited a B + V-type crystalline structure by X-ray diffraction (XRD). We hypothesize that there were two stages for the effect of plasticizer on the mechanical properties of the composite film. The crystallinity, thermal stability, and water vapor permeability (WVP) of the film initially decreased and then increased with increasing water content from 0 to 20%. The opposite trends were observed for surface smoothness and surface hydrophobicity. Moreover, the addition of 15% G-15% W co-plasticizers was optimal for film blowing, which can substantially reduce the cost of producing starch-based films.

Graphical abstract

Introduction

Presently, there has been increasing attention on starch-based biodegradable materials to reduce the environmental impacts of petroleum-based plastics (Bagde & Nadanathangam, 2019; Dhumal, Ahmed, Bandara, & Sarkar, 2019; Gao, Dong, Hou, & Zhang, 2012; Garavand, Rouhi, Razavi, Cacciotti, & Mohammadi, 2017; Lipatova, Losev, Makarova, Rodicheva, & Burmistrov, 2020; Yan, Hou, Guo, & Dong, 2012; Zhai et al., 2020; Zhang, Wang, et al., 2019). Unfortunately, starch exhibited a poor thermal processing property, owing to its thermal degradation prior to melting stage. Plasticizers can destroy intramolecular and intermolecular hydrogen bonds and disrupt the double helical structures of starch molecules, which in turn tend to reduce the melting temperature, yielding a thermoplastic starch. Currently, polyols, such as glycerol are widely used as plasticizers for the preparation of starch-based films.

In fact, water also showed a good plasticizing property. However, research on the plasticizing mechanism of water is very unsystematic, because the most common film forming method (solution casting method) considers water as a solution carrier of starch gelatinization rather than plasticizer additive. Solution casting process typically requires water for starch gelatinization. The directly added fixed water will be disorderly lost during heating and starch gelatinization, then later evaporated to form thin film. The instability of water molecules in film-forming substrates makes it seldom used as a plasticizer. When compared with the above film forming method, extrusion blowing is a continuous, efficient, and commercial method that can be used as a potential alternative choice to solution casting to prepare starch-based film (Gao et al., 2019; Huntrakul, Yoksan, Sane, & Harnkarnsujarit, 2020; Sun, Liu, Ji, Hou, & Dong, 2017). Moreover, the appropriate moisture content during the extrusion process significantly affects the viscosity as along with the extrusion efficiency, which may further inhibit the retrogradation process of the film product and improve its mechanical properties (Matzinos, Tserki, Kontoyiannis, & Panayiotou, 2002).

In this context, starch-based films with different physicochemical and structural properties can be obtained by controlling the constant amount of co-plasticizers (glycerol and water) and adjusting glycerol/water ratios during extrusion process. In addition, it is worth noting that the extrusion blowing process requires a substantial amount of plasticizer due to its industrial production mode and water would substantially reduce the production cost of starch films. Therefore, it is essential to investigate the synergistic plasticizing effect of water and glycerol in extrusion film blowing process with limited water by strictly controlling other film-forming conditions.

Herein, starch-based films incorporated with different glycerol/water ratios were developed through extrusion blowing process. The physicochemical and structural properties of prepared films were then investigated.

Section snippets

Materials

Hydroxypropyl starch (0.031 degree of substitution, 12.5 wt% moisture, 0.23 wt% ashes, 0.26 wt% lipids, 0.24 wt% proteins, and 22.5 wt% amylose) was procured from Proloxing Starch Co., Ltd. (Zhejiang, China). Glycerol was provided by Fuyu Fine Chemical Co., Ltd. (Tianjin, China). Deionized water was prepared in the lab.

Compounding and extruding

Glycerol and deionized water mixed in different proportions with a constant total amount (300 g) were blended with hydroxypropyl starch (2000 g) in an SHR50A mixer (Hongji Co.,

FT-IR spectra of films

FT-IR spectra of films were recorded to explore the molecular interactions between starch molecules and plasticizer. As shown in Fig. 2Ⅰ, all film specimens exhibited characteristic peaks belonging to starch. The peaks at 2920 and 1640 cm⁻¹ were related to C–H stretching vibration and tightly bound water bending vibration, respectively (Zhang, Mei, Chen, & Chen, 2017). A broad peak at approximately 3280 cm⁻¹ was attributed to complex stretching vibrations of hydroxyl groups that were associated

Conclusions

Different proportions of glycerol and water were used as plasticizers to fabricate starch-based films by extrusion blowing. There were two stages for the effect of composite plasticizer on the properties of starch-based films. A 15% G-15% W co-plasticized film would exhibit the highest TS of 5.27 MPa, WCA value of 52.80, the lowest WVP value of 4.16 g⋅mm⋅h⁻¹⋅m⁻²⋅kPa⁻¹ along with smooth surface. Further, there were no notable differences among the appearances of starch-based films when water

CRediT authorship contribution statement

Wei Gao: Investigation, Software, Visualization, Writing – original draft. Jie Zhu: Supervision, Project administration. Xuemin Kang: Investigation, Data curation. Bin Wang: Investigation, Formal analysis. Pengfei Liu: Formal analysis, Writing – review & editing. Bo Cui: Conceptualization, Methodology, Writing – review & editing, Supervision. A.M. Abd El-Aty: Investigation, Formal analysis, Writing – review & editing.

Declaration of competing interest

The authors declare there is no conflict of interest.

Acknowledgements

The authors appreciate the financial support of National Key Research & Development Program in China (2019YFD1002704), the Natural Science Foundation of Shandong Province (ZR2018BC064), the Special Funds for Taishan Scholars Project, the Funds for Innovation Team of Jinan (2018GXRC004), Major projects for independent innovation of Shandong Province (2019JZZY010722), Shandong Bohai Granary Science demonstration Project (2019BHLC002), University Student Innovation and Entrepreneurship Training

References (52)

P.C. Araujo-Farro et al.
Development of films based on quinoa (Chenopodium quinoa, Willdenow) starch
Carbohydrate Polymers
(2010)
P. Bagde et al.
Mechanical, antibacterial and biodegradable properties of starch film containing bacteriocin immobilized crystalline nanocellulose
Carbohydrate Polymers
(2019)
J. Bonilla et al.
Effect of essential oils and homogenization conditions on properties of chitosan-based films
Food Hydrocolloids
(2012)
Y.P. Chang et al.
Interactive plasticizing-antiplasticizing effects of water and glycerol on the tensile properties of tapioca starch films
Food Hydrocolloids
(2006)
Y. Cheng et al.
Effect of gelatin bloom values on the physicochemical properties of starch/gelatin-beeswax composite films fabricated by extrusion blowing
Food Hydrocolloids
(2021)
G.A. Denavi et al.
Structural and functional properties of soy protein isolate and cod gelatin blend films
Food Hydrocolloids
(2009)
C.V. Dhumal et al.
Improvement of antimicrobial activity of sago starch/guar gum bi-phasic edible films by incorporating carvacrol and citral
Food Packaging and Shelf Life
(2019)
W. Gao et al.
Effects of clays with various hydrophilicities on properties of starch-clay nanocomposites by film blowing
Carbohydrate Polymers
(2012)
W. Gao et al.
The co-plasticization effects of glycerol and small molecular sugars on starch-based nanocomposite films prepared by extrusion blowing
International Journal of Biological Macromolecules
(2019)
W. Gao et al.
Physicochemical properties of corn starch affected by the separation of granule shells
International Journal of Biological Macromolecules
(2020)

A. Pawlak et al.

Thermogravimetric and FTIR studies of chitosan blends

Thermochimica Acta

(2003)

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¹: Wei Gao and Jie Zhu contributed equally to this work and are co-first authors.

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