Effect of processing on the viscoelastic, tensile and optical properties of albumen/starch-based bioplastics

Preparation of Surgical Thread from a Bioplastic Based on Nopal Mucilage

Currently, natural materials represent a sustainable option for the manufacture of biopolymers with numerous industrial applications and characteristics comparable with synthetic materials. Nopal mucilage (NM) is an excellent natural resource for the synthesis of bioplastics (BPs). In the present research, the fabrication of biopolymers by using NM is addressed. Changes in the plasticizer (sorbitol and cellulose) concentration, in addition to the implementation of two sources of starch (corn starch (CS) and potato starch (PS)) to obtain the surgical thread, were analyzed. The NM extracted was close to 14% with ethanol. During the characterization of the extract, properties such as moisture, humidity, viscosity, and functional groups, among others, were determined. In the CS and PS analysis, different structures of the polymeric chains were observed. BP degradation with different solvents was performed. Additionally, the addition of sorbitol and cellulose for the BP mixtures presenting the highest resistance to solvent degradation and less solubility to water was conducted. The obtained thread had a uniform diameter, good elasticity, and low capillarity compared to other prototypes reported in the literature.

Twin-Screw Extrusion of Oat: Evolutions of Rheological Behavior, Thermal Properties and Structures of Extruded Oat in Different Extrusion Zones

Further investigation of material properties during the extrusion process is essential to achieve precise control of the quality of the extrudate. Whole oat flour was used to produce low moisture puffed samples by a twin-screw extruder. X-ray diffraction (XRD), Scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermal analysis, and rheological experiments were used to deeply characterize changes in the structure and cross-linking of oats in different extrusion zones. Results indicated that the melting region was the main region that changed oat starch, including the major transformation of oat starch crystal morphology and the significant decrease of enthalpy representing the starch pasting peak in the differential scanning calorimeter (DSC) pattern (p < 0.05). Moreover, the unstable structure of the protein increased in the barrel and then decreased significantly (p < 0.05) after being extruded through the die head. The viscosity of oats increased in the cooking zone but decreased after the melting zone. A transformation occurred from elastic-dominant behavior to viscoelastic-dominant behavior for oats in the melting zone and after being extruded. This study provides further theoretical support for the research of the change of materials during extrusion and the development of oat-based food.

Influence of whey protein isolate on pasting, thermal, and structural characteristics of oat starch

We investigated the effects of different concentrations of whey protein isolate (WPI) on oat starch characteristics in terms of pasting, thermal, and structural properties. The pasting properties of the starch showed that hot paste viscosity increased with the addition of WPI in the system, and relative breakdown decreased. Thermal analysis showed a significant effect of WPI on oat starch by increasing the peak temperature of differential scanning calorimeter endotherms. The X-ray diffraction and Fourier transform infrared spectroscopy studies revealed that WPI increased the ordered structuration of starch paste, as evident by an increase in relative crystallinity; in addition, a decrease in infrared bands at 1,024 cm^-1 and 1,080 cm^-1 suggested decreased gelatinization of oat starch granules. Overall, WPI at different concentrations affected the oat starch gelatinization properties.

Thermal, pasting and structural studies of oat starch-caseinate interactions

The effects of different concentrations of calcium caseinate (CaCn) on pasting, thermal and structural properties of oat starch were investigated. The effect of CaCn on oat starch was highly dependent on the concentration of CaCn in the mixtures. Characterizations of pasting properties revealed that breakdown, final and setback viscosities increased at high relative contents of CaCn (>50%, w/w), while setback and stability ratio were decreased. Thermal analysis showed an increase in gelatinization temperature and a decrease in enthalpy change. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) suggested significant effects of CaCn on oat starch gelatinization. Based on XRD results, a decreasing trend was observed on the relative crystallinity of the starch-protein mixtures containing high levels of CaCn (e.g. 50% and 75% relative CaCn contents). Increases in FT-IR bands at 1024 cm^-1 and 1152 cm^-1 suggested an increase in amorphous structuration of the mentioned starch-protein mixtures.

Rheology of Polymer Processing in Spain (1995-2020)

The contribution of Spanish scientists to the rheology involved in polymer processing during the last 25 years is investigated. It is shown that the performed research covers, at different levels, all industrial polymeric materials: thermoplastics, thermosets, adhesives, biopolymers, composites and nanocomposites, and polymer modified bitumen. Therefore, the rheological behaviour of these materials in processing methods such as extrusion, injection moulding, additive manufacturing, and others is discussed, based on the literature results. A detailed view of the most outstanding achievements, based on the rheological criteria of the authors, is offered.

Proteins from Agri-Food Industrial Biowastes or Co-Products and Their Applications as Green Materials

A great amount of biowastes, comprising byproducts and biomass wastes, is originated yearly from the agri-food industry. These biowastes are commonly rich in proteins and polysaccharides and are mainly discarded or used for animal feeding. As regulations aim to shift from a fossil-based to a bio-based circular economy model, biowastes are also being employed for producing bio-based materials. This may involve their use in high-value applications and therefore a remarkable revalorization of those resources. The present review summarizes the main sources of protein from biowastes and co-products of the agri-food industry (i.e., wheat gluten, potato, zein, soy, rapeseed, sunflower, protein, casein, whey, blood, gelatin, collagen, keratin, and algae protein concentrates), assessing the bioplastic application (i.e., food packaging and coating, controlled release of active agents, absorbent and superabsorbent materials, agriculture, and scaffolds) for which they have been more extensively produced. The most common wet and dry processes to produce protein-based materials are also described (i.e., compression molding, injection molding, extrusion, 3D-printing, casting, and electrospinning), as well as the main characterization techniques (i.e., mechanical and rheological properties, tensile strength tests, rheological tests, thermal characterization, and optical properties). In this sense, the strategy of producing materials from biowastes to be used in agricultural applications, which converge with the zero-waste approach, seems to be remarkably attractive from a sustainability prospect (including environmental, economic, and social angles). This approach allows envisioning a reduction of some of the impacts along the product life cycle, contributing to tackling the transition toward a circular economy.

Natural Polymeric Materials: A Solution to Plastic Pollution from the Agro-Food Sector

Conventional petroleum-derived plastics represent a serious problem for global pollution because, when discarded in the environment, are believed to remain for hundreds of years. In order to reduce dependence on fossil resources, bioplastic materials are being proposed as safer alternatives. Bioplastics are bio-based and/or biodegradable materials, typically derived from renewable sources. Food waste as feedstock represents one of the recent applications in the research field of bioplastics production. To date, several food wastes have been used as raw materials for the production of bioplastics, including mostly fruit and vegetable wastes. The conversion of fruit and vegetable wastes into biomaterials could occur through simple or more complex processes. In some cases, biopolymers extracted from raw biomass are directly manufactured; on the other hand, the extracted biopolymers could be reinforced or used as reinforcing agents and/or natural fillers in order to obtain biocomposites. The present review covers available results on the application of methods used in the last 10 years for the design of biomaterials obtained from formulations made up with both fruits and vegetables by-products. Particular attention will be addressed to the waste pre-treatment, to the bioplastic formulation and to its processing, as well as to the mechanical and physical properties of the obtained materials.

Effects of Hybridized Organically Modified Montmorillonite and Cellulose Nanocrystals on Rheological Properties and Thermal Stability of K-Carrageenan Bio-Nanocomposite

Herein, hybrid k-carrageenan bio-nanocomposite films were fabricated by using two types of nanofillers, organically modified montmorillonite (OMMT), and cellulose nanocrystals (CNCs). Hybrid bio-nanocomposite films were made by casting techniques employing 4 wt% of CNCs, OMMT, and hybridized CNCs/OMMT in a 1:1 ratio. The rheological and morphological properties and thermal stability of all composites were investigated using rotational rheometry, thermogravimetry analysis, differential scanning calorimetry, field emission scanning electron microscopy, and transmission electron microscopy (TEM). The results showed that the hybrid CNC/OMMT bio-nanocomposite exhibited significantly improved properties as compared to those for the bio-nanocomposites with single fillers due to the nanosize and homogenous nanofiller dispersion in the matrix. Rheological analysis of the hybrid bio-nanocomposite showed higher dynamic shear storage modulus and complex viscosity values when compared to those for the bio-nanocomposite with individual fillers. The TEM analysis of the hybridized CNC/OMMT bio-nanocomposite revealed that more particles were packed together in the CNC network, which restricted the matrix mobility. The heat resistance and thermal stability bio-nanocomposite k-carrageenan film enhanced rapidly with the addition of hybridized CNCs/OMMT to 275 °C. The hybridized CNCs/OMMT exhibited synergistic effects due to the good affinity through interfacial interactions, resulting in the improvement of the material properties.

Valorization of industrial by-products through bioplastic production: defatted rice bran and kraft lignin utilization

The objective of this study was to develop a bioplastic from industrial by-products. Commercial defatted rice bran (DRB) was extruded with 0–30% kraft lignin (KL) as a filler and 30% glycerol as a plasticizer. Firstly, the effect of extrusion temperature on the plasticized DRB’s processability was determined. Increasing the die extrusion temperature from 100°C to 150°C improved the extrudability by decreasing the die pressure and motor current. Subsequently, the effect of KL on plasticized DRB was studied. The addition of 10–30% KL improved DRB processability. The addition of 30% KL markedly lowered the die pressure in comparison to using a 150°C extrusion temperature. Moreover, KL addition decreased DRB viscosity determined by a capillary rheometer. These results were coherent with a decreased storage modulus in a rubber state and an increased tan δ height determined by a dynamic mechanical thermal analyzer (DMA). However, n values of DRB with 10–30% KL could not be explained by a simple mixing rule. This may be attributed to the interaction between DRB and KL, as shown by Fourier transform infrared (FTIR) spectra. KL addition increased Young’s modulus and the glass transition temperature (Tg) of plasticized DRB. Therefore, blending DRB with KL is an effective way to improve polymer flowability at the processing temperature and mechanical properties at ambient temperature.

Development of crayfish bio-based plastic materials processed by small-scale injection moulding

BACKGROUND

Protein has been investigated as a source for biodegradable polymeric materials. This work evaluates the development of plastic materials based on crayfish and glycerol blends, processed by injection moulding, as a fully biodegradable alternative to conventional polymer-based plastics. The effect of different additives, namely sodium sulfite or bisulfite as reducing agents, urea as denaturing agent and L-cysteine as cross-linking agent, is also analysed.

RESULTS

The incorporation of any additive always yields an increase in energy efficiency at the mixing stage, but its effect on the mechanical properties of the bioplastics is not so clear, and even dampened. The additive developing a greater effect is L-cysteine, showing higher Young's modulus values and exhibiting a remnant thermosetting potential. Thus, processing at higher temperature yields a remarkable increase in extensibility.

CONCLUSION

This work illustrates the feasibility of crayfish-based green biodegradable plastics, thereby contributing to the search for potential value-added applications for this by-product.

Thermal, mechanical, and moisture absorption properties of egg white protein bioplastics with natural rubber and glycerol

Petroleum-based plastics have many drawbacks: the large amount of energy required to produce the plastic, the waste generated as a result of plastic production, and the accumulation of waste due to slow degradation rate. It is because of these negative attributes of conventional plastic use that attention is being focused on environmentally friendly plastics from alternative sources. Albumin protein provides one possible source of raw material, with inherent antimicrobial properties that may make it suitable for medical applications. We conducted this study to investigate the various bioplastic properties of the albumin with the use of three plasticizers - water, glycerol, and natural rubber latex. Based on results, 75:25 albumin-water, 75:25 albumin-glycerol, and 80:20 albumin-natural rubber were the best blending ratios for each plasticizer for a subsequent time study to determine water stability, with the 80:20 albumin-natural rubber blend ratio having possessed the best thermal, tensile, and viscoelastic properties overall.