Abstract
In the current work the physicochemical features of poly(vinyl alcohol) (PVOH) biofilms, enriched with eco-friendly polyols and with carotenoid-rich extracts, were investigated. The polyols, such as glycerol (Gly), 1,3-propanediol (PDO), and 2,3-butanediol (BDO) were used as plasticizers and the tomato-based pigments (TP) as coloring agents. The outcomes showed that β-carotene was the major carotenoid in the TP (1.605 mg β-carotene/100 DW), which imprinted the orange color to the biofilms. The flow behavior indicated that with the increase of shear rate the viscosity of biofilm solutions also increased until 50 s−1, reaching values at 37 °C of approximately 9 ± 0.5 mPa·s for PVOH, and for PVOH+TP, 14 ± 0.5 mPa·s in combination with Gly, PDO, and BDO. The weight, thickness, and density of samples increased with the addition of polyols and TP. Biofilms with TP had lower transparency values compared with control biofilms (without vegetal pigments). The presence of BDO, especially, but also of PDO and glycerol in biofilms created strong bonds within the PVOH matrix by increasing their mechanical resistance. The novelty of the present approach relies on the replacement of synthetic colorants with natural pigments derived from agro-industrial by-products, and the use of a combination of biodegradable polymers and polyols, as an integrated solution for packaging application in the bioplastic industry.
Highlights
Plastic materials are very important for modern society, and their significance in multiple applications is undeniable and well-proven [1,2,3]
The results show β-carotene, which is responsible for the orange color, was present in the highest amounts in the tomato by-product extract (1.605 mg β-carotene/100 DW), while lutein (1.498 mg β-carotene/100 DW) confers the yellow pigmentation of the biofilms
poly(vinyl alcohol) (PVOH)-based biofilms appeared flexible as thebiofilm plastic were materials that are available for appeared as flexible as the plastic materials that are commercially available for packaging, like the plastic materials based on polyethylene or polypropylene
Summary
Plastic materials are very important for modern society, and their significance in multiple applications is undeniable and well-proven [1,2,3]. Within the worldwide use of plastics, packaging represents approximately 26% of the total plastics, an indispensable element of the global economy [4,5]. In line with the objectives of a circular economy, as well as a bioeconomy for reducing the use of fossil resources [10,11], plastics based on renewable raw materials are already being developed as carbon-neutral alternatives to fossil-based products [12,13,14]. The production of plastics from renewable raw materials remains about 1% of total plastics (335 million tons in 2016). This can mainly be attributed to competition with inexpensive plastics made from fossil fuel feedstock at low costs. The supply of biomass raw materials and recycling routes poses additional challenges for biodegradable plastic materials [15,16]
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