Biodegradation behavior and digestive properties of starch-based film for food packaging - a review

Exploring urea as a prospective auxiliary for starch functionalization: A concise review on modified starch properties and the sustainable packaging films

Urea is also known as carbamide, an inexpensive and eco-friendly additive for starch functionalization. This article reviews the potential role of urea in starch modification, with the prominence of the mechanism of urea action, alterations in the starch structure and functional properties. In addition, current literature conveys the prospective effect of urea in fabricating starch films for food packaging, and the relevant areas that need to be covered in the forthcoming research are specified at the end of the article section. Urea can modify the diverse physico-chemical and functional properties of starch. Starch-based films exhibit pronounced effects on their mechanical and barrier properties upon the incorporation of urea, although this effect strongly depends on the urea content and degree of substitution (DS). Overall, urea holds great potential for use in the starch and bioplastic film industries, as it produces biocompatible derivatives with desirable performance.

Tailoring hydroxypropyl starch films with curdlan for enhanced properties for edible packaging

Hydroxypropyl starch-based composite system has high potential for many applications such as food packaging and biomedical fields. Here, how the incorporation of curdlan, a thermo-irreversible heating-set gel, tailors the processability, structure, and film performance of hydroxypropyl starch, a cooling-set gel, has been systematically investigated, aiming to achieve enhanced material properties favorable for edible packaging applications. Curdlan incorporation increased the shear-thinning behavior and viscosity of hydroxypropyl starch solution, which was also strongly affected by temperature. The miscibility and comparability between the two polymers with distinct gelation behaviors is a practical and interesting scientific topic. Scanning electron microscopy, dynamic mechanical analysis, and thermogravimetric analysis all indicated good compatibility between hydroxypropyl starch and curdlan. There was no observable phase boundary between the two materials, and all composite films showed only a single relaxation peak and only one polymer thermal decomposition peak. This resulted in improved structural density and overall performance. Compared with pure HPS film, the 7:3 HPS/CD film showed increases in tensile strength by 66.12 % and thermal decomposition temperature by 3 °C, and a reduction in water solubility by 11.72 %. This knowledge gained here may facilitate the development of edible films based on hydroxypropyl starch with satisfying film performance and processability.

Reversible immobilization of cellulase on gelatin for efficient insoluble cellulose hydrolysis

Immobilized enzymes are one of the most common tools used in enzyme engineering, as they can substantially reduce the cost of enzyme isolation and use. However, efficient catalysis of solid substrates using immobilized enzymes is challenging, hydrolysis of insoluble cellulose by immobilized cellulases is a typical example of this problem. In this study, inspired by bees and honeycombs, we prepared gelatin-modified cellulase (BEE) and gelatin hydrogels (HONEYCOMB) to achieve reversible recycling versus release of cellulase through temperature-responsive changes in the triple-stranded helix-like interactions between BEE and HONEYCOMB. At elevated temperatures, BEE was released from HONEYCOMB and participated in hydrolytic saccharification. After 24 h, the glucose yields of both the free enzyme and BEE reached the same level. When the temperature was decreased, BEE recombined with HONEYCOMB to facilitate the effective separation and recycling of BEE from the system. The enzymatic system retained >70 % activity after four reuse cycles. In addition, this system showed good biocompatibility and environmental safety. This method increases the mass transfer capacity and enables easy recovery of immobilized cellulase, thereby serving as a valuable strategy for the immobilization of other enzymes.

Development of starch-based films reinforced with curcumin-loaded nanocomplexes: Characterization and application in the preservation of blueberries

In current study, curcumin-loaded bioactive nanocomplexes (Cur NCs) (2 %, 5 %, 8 %, and 11 %) were used to prepare corn starch (CS)-based composite films (CS-Cur NCs). Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy revealed that Cur NCs were uniformly dispersed in the polymer matrix via physical interaction. Moreover, the mechanical, gas barrier, hydrophobicity, optical, and thermal properties and the antioxidant activity of composite films were potentially improved with the addition of Cur NCs. Subsequently, CS-based film with 11 % Cur NCs exhibited high antioxidant activity (the scavenging rates of DPPH and ABTS are 50.07 % ± 0.82 % and 65.26 % ± 1.60 %, respectively) and was used for packaging blueberries. Compared with the control, the CS-Cur NCs packaging treatment effectively improved the appearance and nutrition of blueberries, and maintained the high activity of several antioxidant enzymes. Furthermore, CS-Cur NCs packaging treatment significantly improved the ascorbic acid (AsA) and glutathione (GSH) levels, thus regulating the AsA-GSH cycle system and suppressing the accumulation of reactive oxygen species (ROS). In summary, the CS-Cur NCs packaging could effectively conserve the postharvest quality of blueberries by improving antioxidant enzyme activity and suppressing excessive accumulation of ROS, which contributes to the development of bioactive packaging and provides novel insights into the preservation of blueberries. This work demonstrates that the development of active packaging is promising to absorb the oxidative radicals from food, and protect the food from inherent and external factors, thus enhancing the quality, security, and shelf-life of the food during storage.

Research advances on the toxicity of biodegradable plastics derived micro/nanoplastics in the environment: A review

The detrimental effects of plastic and microplastic accumulation on ecosystems are widely recognized and indisputable. The emergence of biodegradable plastics (BPs) offers a practical solution to plastic pollution. Problematically, however, not all BPs can be fully degraded in the environment. On the contrary, the scientific community has demonstrated that BPs are more likely than conventional plastics (CPs) to degrade into micro/nanoplastics and release additives, which can have similar or even worse effects than microplastics. However, there is very limited information available on the environmental toxicity assessment of BMPs. The absence of a toxicity evaluation system and the uncertainty regarding combined toxicity with other pollutants also impede the environmental toxicity assessment of BMPs. Currently, research is focused on thoroughly exploring the toxic effects of biodegradable microplastics (BMPs). This paper reviews the pollution status of BMPs in the environment, the degradation behavior of BPs and the influencing factors. This paper comprehensively summarizes the ecotoxicological effects of BPs on ecosystems, considering animals, plants, and microorganisms in various environments such as water bodies, soil, and sediment. The focus is on distinguishing between BMPs and conventional microplastics (CMPs). In addition, the combined toxic effects of BMPs and other pollutants are also being investigated. The findings suggest that BMPs may have different or more severe impacts on ecosystems. The rougher and more intricate surface of BMPs increases the likelihood of causing mechanical damage to organisms and breaking down into smaller plastic particles, releasing additives that lead to a series of cascading negative effects on related organisms and ecosystems. In the case of knowledge gaps, future research is also proposed and anticipated to investigate the toxic effects of BMPs and their evaluation.

An antibacterial packaging film based on amylose starch with quaternary ammonium salt chitosan and its application for meat preservation

A new generation of food packaging films is gradually replacing traditional plastic packaging films because of their biodegradability, safety, and some functional properties such as anti-bacterial and oxidant resistance. In the present work, an antibacterial packing film based on amylose starch and 2-hydroxypropyl-trimethylammonium chloride chitosan (HTCC) was prepared for meat preservation. The interfacial bonding mechanism between amylose, HTCC, and glutaraldehyde (GA) was determined experimentally and through molecular dynamics (MD) simulation. The macromolecular chains of amylose starch and HTCC became entangled via inter-molecular H-bonds and then cross-linked with GA via the Schiff base reaction. The interaction of amylose starch and HTCC improved the mechanical properties of the amylose films. Compared with the amylose films, the tensile strength and elongation at break of the optimal HTCC/amylose films reached to 16.13 MPa (an increase of 206.65 %) and 53.86 % (an increase of 109.49 %). The HTCC/amylose films were found to provide obvious bacteriostatic performance, a relatively low cytotoxicity, the lower transmittance in the UV region, and thus the ability to enhance the preservation of fresh meat. These excellent characteristics therefore suggest that HTCC/amylose films might be promising candidates for application in antibacterial food packaging films.

Study on the Printability of Starch-Based Films Using Ink-Jet Printing

Starch-based films are a valuable alternative to plastic materials that are based on fossil and petrochemical raw resources. In this study, corn and potato starch films with 50% glycerol as a plasticizer were developed, and the properties of films were confirmed by mechanical properties, surface free energy, surface roughness, and, finally, color and gloss analyses. Next, the films were overprinted using ink-jet printing with quick response (QR) codes, text, and pictograms. Finally, the print quality of the obtained prints was determined by optical density, color parameters, and the visual evaluation of prints. In general, corn films exhibit lower values of mechanical parameters (tensile strength, elongation at break, and Young Modulus) and water transition rate (11.1 mg·cm-2·h-1) than potato starch film (12.2 mg·cm-2·h-1), and water solubility is 18.7 ± 1.4 and 20.3 ± 1.2% for corn and potato film, respectively. The results obtained for print quality on starch-based films were very promising. The overprinted QR codes were quickly readable by a smartphone. The sharpness and the quality of the lettering are worse on potato film. At the same time, higher optical densities were measured on potato starch films. The results of this study show the strong potential of using starch films as a modern printing substrate.

A Review on Biopolymer-Based Biodegradable Film for Food Packaging: Trends over the Last Decade and Future Research

In recent years, much attention has been paid to the use of biopolymers as food packaging materials due to their important characteristics and properties. These include non-toxicity, ease of availability, biocompatibility, and biodegradability, indicating their potential as an alternative to conventional plastic packaging that has long been under environmental scrutiny. Given the current focus on sustainable development, it is imperative to develop studies on biopolymers as eco-friendly and sustainable food packaging materials. Therefore, the aim of this review is to explore trends and characteristics of biopolymer-based biodegradable films for food packaging, analyze the contribution of various journals and cooperation between countries, highlight the most influential authors and articles, and provide an overview of the social, environmental, and economic aspects of biodegradable films for food packaging. To achieve this goal, a bibliometric analysis and systematic review based on the PRISMA method were conducted. Relevant articles were carefully selected from the Scopus database. A bibliometric analysis was also conducted to discuss holistically, comprehensively, and objectively biodegradable films for food packaging. An increasing interest was found in this study, especially in the last 3 years with Brazil and China leading the number of papers on biodegradable films for food packaging, which were responsible for 20.4% and 12.5% of the published papers, respectively. The results of the keyword analysis based on the period revealed that the addition of bioactive compounds into packaging films is very promising because it can increase the quality and safety of packaged food. These results reveal that biodegradable films demonstrate a positive and promising trend as food packaging materials that are environmentally friendly and promote sustainability.

Biopolymers as green-based food packaging materials: A focus on modified and unmodified starch-based films

The ideal food packaging materials are recyclable, biodegradable, and compostable. Starch from plant sources, such as tubers, legumes, cereals, and agro-industrial plant residues, is considered one of the most suitable biopolymers for producing biodegradable films due to its natural abundance and low cost. The chemical modification of starch makes it possible to produce films with better technological properties by changing the functional groups into starch. Using biopolymers extracted from agro-industrial waste can add value to a raw material that would otherwise be discarded. The recent COVID-19 pandemic has driven a rise in demand for single-use plastics, intensifying pressure on this already out-of-control issue. This review provides an overview of biopolymers, with a particular focus on starch, to develop sustainable materials for food packaging. This study summarizes the methods and provides a potential approach to starch modification for improving the mechanical and barrier properties of starch-based films. This review also updates some trends pointed out by the food packaging sector in the last years, considering the impacts of the COVID-19 pandemic. Perspectives to achieve more sustainable food packaging toward a more circular economy are drawn.

A combined extrusion, retrogradation, and cross-linking strategy for preparing starch-based straws with desirable mechanical properties

This work developed a novel strategy for producing starch straws with desirable mechanical properties by a combination of extrusion, retrogradation, and sodium trimetaphosphate (STMP) cross-linking. The straws were prepared by first extruding starch, glycerin, and water (10:1:1) with a double screw extruder, then retrograding the resulting straws at 4 °C for 6 h, and finally cross-linking the straws. Rapid visco-analyzer profiles showed decreases in the viscosity of milled straws with increases in the cross-linking duration, perhaps reflecting a higher degree of crosslinking. Fourier transform infrared spectroscopy showed evidence of more hydrogen bonds in the straws with a longer cross-linking duration, while thermogravimetric analysis indicated higher thermal stability for the cross-linked straws than for the controls. The straw cross-linked for 3 h showed 1.52 times higher stiffness after soaking in room-temperature water for 30 min (4967.56 g/s), and 1.88 times higher stiffness after soaking in 60 °C hot water for 5 min (5371.89 g/s) than the original straw. STMP cross-linking also improved the starch straw mechanical properties after soaking in common soft drinks. These findings identify a potential new way to produce biodegradable straws with desirable properties from starch, an affordable biomaterial, while also addressing the problem of petroleum-based plastic pollution.

The Green Era of Food Packaging: General Considerations and New Trends

Recently, academic research and industries have gained awareness about the economic, environmental, and social impacts of conventional plastic packaging and its disposal. This consciousness has oriented efforts towards more sustainable materials such as biopolymers, paving the way for the “green era” of food packaging. This review provides a schematic overview about polymers and blends of them, which are emerging as promising alternatives to conventional plastics. Focus was dedicated to biopolymers from renewable sources and their applications to produce sustainable, active packaging with antimicrobial and antioxidant properties. In particular, the incorporation of plant extracts, food-waste derivatives, and nano-sized materials to produce bio-based active packaging with enhanced technical performances was investigated. According to recent studies, bio-based active packaging enriched with natural-based compounds has the potential to replace petroleum-derived materials. Based on molecular composition, the natural compounds can diversely interact with the native structure of the packaging materials, modulating their barriers, optical and mechanical performances, and conferring them antioxidant and antimicrobial properties. Overall, the recent academic findings could lead to a breakthrough in the field of food packaging, opening the gates to a new generation of packaging solutions which will be sustainable, customised, and green.

Wheat Flour-Based Edible Films: Effect of Gluten on the Rheological Properties, Structure, and Film Characteristics

This work investigates the structure, rheological properties, and film performance of wheat flour hydrocolloids and their comparison with that of a wheat starch (WS)-gluten blend system. The incorporation of gluten could decrease inter-chain hydrogen bonding of starch, thereby reducing the viscosity and solid-like behavior of the film-forming solution and improving the frequency-dependence, but reducing the surface smoothness, compactness, water vapor barrier performance, and mechanical properties of the films. However, good compatibility between starch and gluten could improve the density of self-similar structure, the processability of the film-forming solution, and film performance. The films based on wheat flours showed a denser film structure, better mechanical properties, and thermal stability that was no worse than that based on WS-gluten blends. The knowledge gained from this study could provide guidance to the development of other flour-based edible packaging materials, thereby promoting energy conservation and environmental protection.