Addition of glycerol (a highly hygroscopic molecule) produced films with greater water uptake than films without it. Films containing 5% glycerol showed a five-fold greater swelling index. This behavior explained that glycerol leads to the breakdown of molecular interconnectivity between pectin chains, allowing the absorption of large numbers of water molecules.

Dear all, it works as chanels/path for transport and ease of water (solvent) diffusion, thus multiplied uptake occurs which is reflected by increased swelling. My Regards

Effect of glycerol plasticizer loading on the physical, mechanical, thermal, and barrier properties of arrowroot (Maranta arundinacea) starch biopolymers

• J. Tarique,
• S. M. Sapuan &
• A. Khalina

Scientific Reports volume 11, Article number: 13900 (2021) Cite this article

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Abstract This research was set out to explore the development of arrowroot starch (AS) films using glycerol (G) as plasticizer at the ratio of 15, 30, and 45% (w/w, starch basis) using solution casting technique. The developed films were analyzed in terms of physical, structural, mechanical, thermal, environmental, and barrier properties. The incorporation of glycerol to AS film-making solution reduced the brittleness and fragility of films. An increment in glycerol concentration caused an increment in film thickness, moisture content, and solubility in water, whereas density and water absorption were reduced. The tensile strength and modulus of G-plasticized AS films were reduced significantly from 9.34 to 1.95 MPa and 620.79 to 36.08 MPa, respectively, while elongation at break was enhanced from 2.41 to 57.33%. FTIR analysis revealed that intermolecular hydrogen bonding occurred between glycerol and AS in plasticized films compared to control films. The G-plasticized films showed higher thermal stability than control films. The cross-sectional micrographs revealed that the films containing 45% glycerol concentration had higher homogeneity than 15% and 30%. Water vapour permeability of plasticized films increased by an increase in glycerol concentrations. The findings of this research provide insights into the development of bio-degradable food packaging.

Introduction The packaging plays a pivotal role in maintaining the food quality and regulating the interaction between the environment and food1,2,3. Due to magnificent versatility, mechanical and barrier properties, petroleum-based plastics mostly have wide applications in packaging industries4,5,6,7. Even though petroleum-based plastics have outstanding properties, they are also significant source of environmental issues due to their non-biodegradability. Hence, petroleum-based plastics are considered as the major factor, if not the only one, causing solid waste generation and build up in the environment. Petroleum-based plastics are non-biodegradable as well as originating from non-renewable sources8. These non-biodegradable petroleum-based polymers have caused growing concern about the wide usage of packaging due to the rapid depletion of petroleum reserves9,10,11,12,13,14,15. Owing to such concerns, the replacement of petroleum-based packaging with renewable and bio-degradable polymers materials have been stimulated since minimizing related environmental issues with natural polymers is vital16,17,18,19,20. In that regard, the agricultural resources have important biopolymers, such as polysaccharides and proteins to reduce the above-mentioned brief drawbacks of petroleum-based plastics21,22,23,24,25. Nowadays, natural compounds like proteins, lipids, and polysaccharides are utilized in making biodegradable and sustainable films26,27,28. According to Sartori et al.29, starch is one of the highest potentially polysaccharides owing to its potential to build a continuous matrix and low cost, plentiful, renewable, and available in various raw materials. Several researchers have vouched to the rising attention for developing bio-based packaging films by utilization of starch from many sources30,31,32,33,34,35,36,37,38. In this way, the arrowroot (Maranta arundinacea) rhizomes have emerged as powerful sources of starch and fiber.Arrowroot (Maranta arundinacea) is mostly found in the tropical forest as a large perpetual herb and belongs to the Marantaceae family39. Arrowroot starch has excellent characteristics such as digestibility40, gelling ability41,42, as well as having the highest amylose content (40.86%)43, competing with corn starch (28–33%), wheat starch (30–32%), potato (18–20%), and cassava starch (16–19%), which are necessary for producing the films. Previous studies have documented that the film-forming properties of starch depend on the amylose content44,45,46,47, strong and stiff films are made by linking linear chains by hydrogen bonding. Hence, the high amylose content of arrowroot starch develops stronger films than other starch origins.Nonetheless, Pelissari et al.48 reported that there are restrictions like brittleness and hydrophilic behaviour in starch-based films that directly impact the mechanical as well as barrier properties of the films, resulting in affecting the food packaging49. The restrictions, as mentioned above, can be overcome by adding the plasticizers, including glycerol, sorbitol, and polyethene glycol. Among the plasticizing agents, glycerol has been used as a plasticizer to produce starch-based films because of its compatibility with amylose50, which stimulates better mechanical properties through interfering with amylose packing by forces between molecules declines between the starch molecules. Plasticized-starch films showed more flexibility as well as feasibility than unplasticized films for different packaging applications51. Several studies demonstrated the efficacy of glycerol as a plasticizer with concentrations of 20–40% of the starch weight52,53,54,55. Mali et al.52, analyzed the impact of glycerol with the concentration of (0–40%) on tapioca, corn, and yam starches and showed that, regardless of starch types, the tensile strength decreased whereas the elongation at break improved with increasing the concentration of glycerol.