The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

Sodium alginate-based indicator film with enhanced physicochemical properties induced by cellulose nanocrystals and monitor the freshness of chilled meat

Intelligent indicator films with colorimetric pH indicator properties were developed, incorporating black soybean seed coat anthocyanin (BA), cellulose nanocrystals (CNC), and sodium alginate (SA) to monitor meat freshness. The effect of different CNC additions on the microstructure, water barrier properties of the films, and BA release kinetics were comprehensively investigated. The results showed that with the increasement of CNC addition, the mechanical properties of SA/BA/CNC films were improved, the water contact angle significantly increased from 51.6° to 69°. Moreover, water solubility, vapor adsorption, and permeability significantly decreased, indicating enhanced water barrier properties. The release kinetic results showed that BA was released rapidly within 72 h and slowly thereafter, and its release process was described by Fick's model. Films with 7 % and 10 % CNC had lower BA diffusion coefficients. Their diffusions were formulated as linear regression equations (y = nx + a), where R2 was >0.80 and n was <0.50. Structural characterization showed that CNC immobilized BA mainly through hydrogen bonding, forming compact network microstructures with SA and BA. Meat freshness monitoring results showed that the film containing 7 % CNC showed visible color changes with increasing total volatile basic nitrogen and pH, along with low BA release, high water barrier and mechanical properties. Therefore, CNC has great potential for improving the physicochemical properties of indicator films, and the intelligent colorimetric indicator film could be applied to various food product.

Investigating the Impact of Moisture Levels on Structural Alterations and Physicochemical Properties of Cassava Flour through Extrusion: A Comprehensive Study

The extrusion process, a vital technique for starch modification, is notably influenced by the moisture content (MC). This study aimed to elucidate the effect of varying MC levels (18, 22, 26, and 30%) on the structural and physicochemical characteristics of cassava flour during extrusion. Extrusion resulted in the fraction of degree of polymerization 13‒24, degree of branching, and molecular weight increased with increasing MC, with values of above indexes being 32.29%, 1.05%, and 1.21 × 105 g/mol, respectively, at a MC of 18%. This suggested that the degradation of amylopectin and amylose. Additionally, there was an increase in rapidly digestible starch (RDS) and a decrease in slowly digestible starch (SDS) in the extrudates in comparison to the native cassava flour. The extrusion of cassava flour at 18% MC exhibited the highest levels of RDS and SDS, reaching 64.52% and 4.06%, respectively. These findings indicated that low moisture extrusion could be a more effective method for disrupting the structure of cassava starch and enhancing the digestibility of cassava flour, offering valuable insights for the optimized use of cassava extrudates in various applications.

Effects of different oil additives on water resistance of corn starch straws

To investigate the effect of oil additives on improving the water resistance of corn starch straws, corn oil (CO), soybean oil (SO), rapeseed oil (RO), peanut oil (PO), lard (LD) and coconut oil (CCO) were chosen and compared the structure and properties of starch straws with different oil additives. Corn starch straws (CS), and starch straws supplemented with CO, SO, RO, PO, LD and CCO were prepared by thermoplastic extrusion. The results showed that the incorporation of oils effectively enhanced the water resistance of starch straws such as water absorption, water solubility and water swelling performance. Meanwhile, the flexural strength of starch straws significantly increased. There was no significant linear relationship among starch chain length, oil unsaturation and straw performance. Among seven starch straws, S-SO had the strongest hydrogen bond interaction (3289 cm-1) and relaxation time (0.96 ms). The S-CO had the highest relative crystallinity (16.82 %) and degree of double helix (1.535), hence resulting in the lowest water absorption and solubility values, the highest flexural strength (23.43 MPa), the highest ΔT value (9.93 °C) and ΔH value (4.79 J/g). S-RO had the highest thermal transition temperatures.

Innovative plasticization technique for talc-powder reinforced wheat-starch biomass composite plastics with enhanced mechanical strength

N-methyl-morpholine-N-oxide (NMMO) was initially created as a plasticizer for starch to produce thermoplastic wheat starch. Subsequently, talc powder was used as a reinforcing filler to enhance the mechanical strength of thermoplastic biomass-based composite plastics. The chemical structure, crystal structure, and microscopic morphology were analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Additionally, the thermal properties were explored through thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The hydrated NMMO plasticizer demonstrated an outstanding plasticizing effect on starch, resulting in a composite with remarkable mechanical properties. In fact, the pure thermoplastic wheat starch plasticized with hydrated NMMO exhibited the highest mechanical strength recorded so far, with a tensile strength of up to 9.4 MPa. In addition, talcum powder displayed a noticeable reinforcing effect. When the talcum powder content reached 30 wt%, the targeted composite achieved a tensile strength of 20.5 MPa and a Young's modulus of 177.9 MPa. These values were 118 % and 48 % higher, respectively, than those of the pure thermoplastic starch sample. This innovative plasticizing method opens up a new avenue for the development of high-mechanical-strength thermoplastic biomass-based composite plastics with promising potential applications.

Moisture loss inhibition with biopolymer films for preservation of fruits and vegetables: A review

In cold storage, fruits and vegetables still keep a low respiratory rate. Although cold storage is beneficial to maintain the quality of some fruits and vegetables, several factors (temperature and humidity fluctuations, heat inflow, air velocity, light, etc.) will accelerate moisture loss. Biopolymer films have attracted great attention for fruits and vegetables preservation because of their biodegradable and barrier properties. However, there is still a certain amount of water transfer occurring between storage environment/biopolymer films/fruits and vegetables (EFF). The effect of biopolymer films to inhibit moisture loss of fruits and vegetables and the water transfer mechanism in EFF system need to be studied systematically. Therefore, the moisture loss of fruits and vegetables, crucial properties, major components, fabrication methods, and formation mechanisms of biopolymer films were reviewed. Further, this study highlights the EFF system, responses of fruits and vegetables, and water transfer in EFF. This work aims to clarify the characteristics of EFF members, their influence on each other, and water transfer, which is conducive to improving the preservation efficiency of fruits and vegetables purposefully in future studies. In addition, the prospects of studies in EFF systems are shown.

Development of cinnamon essential oil-loaded PBAT/thermoplastic starch active packaging films with different release behavior and antimicrobial activity

The poly (butylene adipate-co-terephthalate)/thermoplastic starch (PBAT/TPS) active packaging films containing cinnamon essential oil (CEO) were fabricated by melting blending and extrusion casting method. The effects of TPS content (0 %, 10 %, 20 %, 30 %, 40 % and 50 %) on the properties of the films and their application in largemouth bass preservation were studied. As TPS content increased from 0 % to 50 %, the water vapor permeability increased from 7.923 × 10-13 (g•cm/(cm2•s•Pa)) to 23.967 × 10-13 (g•cm/(cm2•s•Pa)), the oxygen permeability decreased from 8.642 × 10-11 (cm3•m/(m2•s•Pa)) to 3.644 × 10-11 (cm3•m/(m2•s•Pa)), the retention of CEO in the films increased. The release rate of CEO from the films into food simulant (10 % ethanol) accelerated with increasing TPS. The films exhibited different antibacterial activity against E. coli, S. aureus, and S. putrefaciens. It was closely related with the release behavior of the CEO. The films containing CEO could efficiently inhibit the decomposition of protein and the growth of microorganisms in largemouth bass. It showed that the higher TPS in the films, the better inhibitory effect. This study provided a new idea for developing PBAT/TPS active films with different release behavior of active agents and different antibacterial activity for food packaging.

From micro to macro: Physical-chemical characterization of wheat starch-based films modified with PEG200, sodium citrate, or citric acid

Needing to extend the shelf-life of packaged food and the evolving consumer demands led researchers to seek innovative, eco-friendly, and biocompatible packaging solutions. Starch is among the most promising natural and renewable alternatives to non-degradable plastics. Here, we deeply study the structural features of starch films modified by adding citric acid (CA) or sodium citrate (SC) as a cross-linker and polyethylene glycol 200 (PEG200) as a plasticizer and obtained through solvent casting. The substances' influence on starch films was evaluated through Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and Solid-state Nuclear Magnetic Resonance (ss-NMR) spectroscopies. Films' macroscopic properties, such as swelling index, solubility, thermo-mechanical features, and moisture absorption, were also assessed to foresee potential applications. Proper amounts of CA, CS, and PEG200 improve film properties and inhibit starch chains' retrogradation and recrystallization. Besides, the chemical neighbourhood of nuclei observed through ss-NMR significantly changed alongside the polymer chains' mobility. The latter result indicates a different polymer chain structural organization that could justify the film's higher resistance to thermal degradation and elongation at the break. This methodological approach is effective in predicting the macroscopic behaviour of a polymeric material and could be helpful for the application of such products in food preservation.

Influence of Glycerol and SISAL Microfiber Contents on the Thermal and Tensile Properties of Thermoplastic Starch Composites

The increasing use of petroleum plastics has caused environmental damage due to the degradation time of these materials. An alternative to petroleum plastics could be thermoplastic starch (TPS). However, thermoplastic starch does not exhibit satisfactory tensile properties. The mechanical properties of thermoplastic starch can be improved by adding sisal microfibers. Thus, the objective of this study was to evaluate the influence of different levels of glycerol and sisal microfibers on the thermal and tensile properties of thermoplastic corn starch composites. The microfibers were obtained via mechanical treatment followed by chemical treatment (alkaline treatment and bleaching). The films were obtained by the casting method using commercial corn starch and glycerol as a plasticizing agent, reinforced with sisal microfibers. Fourier transform infrared spectroscopy (FTIR) results revealed that the addition of microfibers did not change the chemical structure of the TPS matrix. The films from the samples with 18% glycerol and 10% microfibers had the highest value for the maximum tension, equal to 4.78 MPa. The thermal decomposition profile of TPS was not altered by the addition of microfibers. Our findings demonstrated the profound influence of glycerol and microfiber contents on the tensile properties of thermoplastic starch composites.

Colorimetric pH indicators based on well-defined amylose and amylopectin matrices enriched with anthocyanins from red cabbage

This study aimed to prepare a novel colorimetric indicator film from virtually pure (99 %) amylose (AM) and anthocyanins extracted from red cabbage (RCA). The AM used was a unique engineered bulk material extracted from transgenic barley grains. Films produced by solution casting were compared to normal barely starch (NB) and pure barley amylopectin (AP), with amylose contents of 30 % and 0 %, respectively. The pH-indicator films were produced by incorporation of RCA into the different starch support matrices with different amylose contents. Barrier, thermal, and mechanical properties, photo degradation stability, and release behavior data revealed that RCA interact differently through the glucan matrices. Microstructural observations showed that RCA were evenly dispersed in the glucan matrix, and AM+RCA indicator films showed high UV-barrier and mechanical performance over normal starch. FTIR revealed that RCA was properly affected by the AM matrix. Moreover, the AM+RCA films showed sensitive color changes in the pH range (2-11) and a predominant Fickian diffusion release mechanism for RCA. This study provides for the first time data regarding AM films with RCA and their promising potential for application as support matrices in responsive food and other industrial biodegradable packaging materials.