Preparation and characterization of cross-linked starch nanocrystals and self-reinforced starch-based nanocomposite films

Cross-linking affecting properties and in-vitro digestibility of starch-sucrose ester complexes

This study investigated the effects of cross-linking on the characteristics and in-vitro digestibility of starch-sucrose ester (SE) complexes. To achieve this, corn starch (CS) was cross-linked with various concentrations of sodium trimetaphosphate /sodium tripolyphosphate (5 %, 10 %, and 15 %). Subsequently, cross-linked starches (CLS) were complexed with SE through hydrothermal treatment. X-ray diffraction analysis revealed that V-type amylose-lipid complexes formed by the interaction between CS and SE. The resultant CS-SE complex significantly reduced CS digestibility, increasing its resistant starch (RS) content from 10.19 % to 22.71 %. The cross-linking modification did not alter the crystalline pattern of the CS-SE complex. Several CLS-SE complexes demonstrated higher enzymatic resistance compared to the CS-SE complex. The CLS10-SE complex exhibited the highest RS content of 39.37 % when the cross-linking agent concentration was 10 %. This phenomenon may be attributable to the cross-linking reaction having enhanced the interaction between starch molecular chains, reducing the solubility and swelling power, thereby hindering the accessibility of starch chains to digestive enzymes. These findings indicate that cross-linking modification is a practical approach to improving the anti-digestion performance of starch-lipid complexes.

Nanofillers in Novel Food Packaging Systems and Their Toxicity Issues

Background: Environmental concerns about petroleum-based plastic packaging materials and the growing demand for food have inspired researchers and the food industry to develop food packaging with better food preservation and biodegradability. Nanocomposites consisting of nanofillers, and synthetic/biopolymers can be applied to improve the physiochemical and antimicrobial properties and sustainability of food packaging. Scope and approach: This review summarized the recent advances in nanofiller and their applications in improved food packaging systems (e.g., nanoclay, carbon nanotubes), active food packaging (e.g., silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs)), intelligent food packaging, and degradable packaging (e.g., titanium dioxide nanoparticles (e.g., TiO2 NPs)). Additionally, the migration processes and related assessment methods for nanofillers were considered, as well as the use of nanofillers to reduce migration. The potential cytotoxicity and ecotoxicity of nanofillers were also reviewed. Key findings: The incorporation of nanofillers may increase Young's modulus (YM) while decreasing the elongation at break (EAB) (y = -1.55x + 1.38, R2 = 0.128, r = -0.358, p = 0.018) and decreasing the water vapor (WVP) and oxygen permeability (OP) (y = 0.30x - 0.57, R2 = 0.039, r = 0.197, p = 0.065). Meanwhile, the addition of metal-based NPs could also extend the shelf-life of food products by lowering lipid oxidation by an average of approx. 350.74% and weight loss by approx. 28.39% during the longest storage period, and significantly increasing antibacterial efficacy against S. aureus compared to the neat polymer films (p = 0.034). Moreover, the migration process of nanofillers may be negligible but still requires further research. Additionally, the ecotoxicity of nanofillers is unclear, as the final distribution of nanocomposites in the environment is unknown. Conclusions: Nanotechnology helps to overcome the challenges associated with traditional packaging materials. Strong regulatory frameworks and safety standards are needed to ensure the appropriate use of nanocomposites. There is also a need to explore how to realize the economic and technical requirements for large-scale implementation of nanocomposite technologies.

Recent advances in starch-based coatings for the postharvest preservation of fruits and vegetables

Efficient and low-cost postharvest preservation of fruits and vegetables has always been one of the urgent problems to be solved in the food field. Due to the wide sources, good environmental and human safety, and high biodegradability, starch-based coating preservation method has great application prospects in the postharvest preservation of fruits and vegetables. However, starch materials also have the disadvantages of poor mechanical properties and easy water absorption performance, which makes it difficult to fully meet the requirements in practical production. Therefore, starch is often used in combination with other components to form composite materials. This paper began with an introduction to the preservation principles of edible starch-based coatings, including inherent properties and extra functional properties. Besides, the preservation principles of edible coatings and the recent advances in the field of fruit and vegetable preservation were also comprehensively reviewed, focusing on the preparation and application of starch-based coatings. The information will contribute to the further development of starch-based coatings to improve the postharvest preservation effect of fruits and vegetables.

Insights into starch-based gels: Selection, fabrication, and application

Starch a natural polymer, has made significant advancements in recent decades, offering superior performance and versatility compared to synthetic materials. This review discusses up-to-date diverse applications of starch gels, their fabrication techniques, and their advantages over synthetic materials. Starch gels renewability, biocompatibility, biodegradability, scalability, and affordability make them attractive. Also, advanced theoretical foundations and emerging industrial technologies could further expand their scope and functions inspiring new applications.

Preparation of starch-palmitic acid complex nanoparticles and their effect on properties of the starch composite film

The corn starch-palmitic acid complex nanoparticles and amylose-palmitic acid complex nanoparticles were prepared through complex and nanoprecipitation. Their mean size values were 138.2 nm and 654.7 nm, respectively, while the two kinds of complex nanoparticles were mainly showed V-type crystalline structure, the crystallinity of these complex nanoparticles was 20.86 % and 46.81 %. Then the starch composite films were prepared using the corn starch-palmitic acid complex nanoparticles and amylose-palmitic acid complex nanoparticles as reinforcement phases. The starch composite film reinforced with amylose-palmitic acid complex nanoparticles had the higher tensile strength and a better wettability with the water contact angle of 86.51°. Though the crystalline properties of starch composite films had no significant difference, the thermal stability improved when the amylose-palmitic acid complex nanoparticles used as reinforcement phase, the maximum thermal degradation temperature was 313 °C. This study provides a new type of reinforcement phase to improve the properties of starch composite films.

Recent preparation, modification and application progress of starch nanocrystals: A review

Due to the advantages of wide sources, high biocompatibility and favorable biodegradability, starch nanocrystals (SNCs) have gradually attracted attention and have bright development prospects in food, agriculture, materials, medicine and other fields. However, the traditional preparation method of SNCs is time-consuming and inefficient, and the physicochemical properties cannot fully meet the needs of multiple applications. Fortunately, the unique onion-like structure of starch granules and the large number of hydroxyl groups present on the surface entitle SNCs to efficient preparation and modification. This paper comprehensively reviewed the improvement methods of SNCs preparation process in recent years, and the advantages and disadvantages of the two improvement strategies were compared. Besides, the importance of introducing different pretreatment methods into the SNCs preparation process was emphasized. It also focused on the different modification treatment and application progress of SNCs, especially in the starch-based surface coating of fruits and vegetables. The information will contribute to further improve the preparation efficiency and physicochemical properties of SNCs, and ultimately expand the application field.

Effect of shear and heat milling of starch on the properties of tapioca starch/cellulose nanofiber composites

Thermoplastic starch was prepared from tapioca starch (TS) and thermo-mechanical modified TS (ModifiedTS) using glycerol as a plasticizer and cellulose nanofiber (CNF) as a reinforcement. The ModifiedTS was produced using shear-and-heat milling machining (SHMM), which effectively reduced starch crystallinity and transformed the granule shape without a chemical reaction. The modified starch with low crystallinity and numerous active hydrogen bonds clearly showed Vh crystal structure after blending with glycerol. The mechanical properties changed significantly upon addition of 10 wt% CNF into plasticized ModifiedTS, which enhanced the yield strength and decreased the elongation at break. A dynamic mechanical analysis revealed a higher glass transition temperature (Tg) of the ModifiedTS films. Tg for the starch film increased from 9.3 °C of the TS film to 29.8 °C of the ModifiedTS film. These results suggest that SHMM provides the ability to widely adjust the mechanical properties of glycerol plasticized starch materials by enhancing interfacial interactions with CNF.

Cassava Starch Films Containing Quinoa Starch Nanocrystals: Physical and Surface Properties

Quinoa starch nanocrystals (QSNCs), obtained by acid hydrolysis, were used as a reinforcing filler in cassava starch films. The influence of QSNC concentrations (0, 2.5, 5.0, 7.5 and 10%, w/w) on the film's physical and surface properties was investigated. QSNCs exhibited conical and parallelepiped shapes. An increase of the QSNC concentration, from 0 to 5%, improved the film's tensile strength from 6.5 to 16.5 MPa, but at 7.5%, it decreased to 11.85 MPa. Adequate exfoliation of QSNCs in the starch matrix also decreased the water vapor permeability (~17%) up to a 5% concentration. At 5.0% and 7.5% concentrations, the films increased in roughness, water contact angle, and opacity, whereas the brightness decreased. Furthermore, at these concentrations, the film's hydrophilic nature changed (water contact angle values of >65°). The SNC addition increased the film opacity without causing major changes in color. Other film properties, such as thickness, moisture content and solubility, were not affected by the QSNC concentration. The DSC (differential scanning calorimetry) results indicated that greater QSNC concentrations increased the second glass transition temperature (related to the biopolymer-rich phase) and the melting enthalpy. However, the film's thermal stability was not altered by the QSNC addition. These findings contribute to overcoming the starch-based films' limitations through the development of nanocomposite materials for future food packaging applications.

Production of Thermoplastic Starch-Aloe vera Gel Film with High Tensile Strength and Improved Water Solubility

Biodegradable film packaging made from thermoplastic starch (TPS) has low mechanical performance and high water solubility, which is incomparable with synthetic films. In this work, Aloe vera (AV) gel and plasticized soluble potato starch were utilised to improve the mechanical stability and water solubility of TPS. Dried starch was mixed with glycerol and different AV gel concentrations (0% to 50%). The TPS + 50% AV gel (30 g TPS + 15 g AV gel) showed the best improvement compared to TPS alone. When compared to similar TPS films with AV gel added, this film is stronger and dissolves better in water. Mechanical qualities improved the tensile strength and Young's modulus of the TPS film, with 1.03 MPa to 9.14 MPa and 51.92 MPa to 769.00 MPa, respectively. This was supported by the improvement of TPS water solubility from 57.44% to 46.6% and also by the increase in decomposition temperature of the TPS. This promises better heat resistance. The crystallinity percentage increase to 24.26% suggested that the formation of hydrogen bonding between TPS and AV gel enhanced crosslinking in the polymeric structure. By adding AV gel, the TPS polymeric structure is improved and can be used as a biodegradable food-packaging film.

Whey protein isolate/jujube polysaccharide-based edible nanocomposite films reinforced with starch nanocrystals for the shelf-life extension of banana: Optimization and characterization

The formulation of new bionanocomposite (BNC) films using whey protein isolates (WPI, 3.3-11.7 %)-jujube polysaccharide (JPS, 1.59-18.41 %)/starch nanocrystals (SNCs, 0.32-3.68 %) blends was optimized. The ultrasound-assisted acid hydrolysis produced ~63.1 nm SNCs from native starch with -24.3 mV ζ-potential. The extracted JPS purification led to a single symmetrical peak for galactoarabinan-rich fraction (1.35 × 10⁵ Da). The optimal levels of barrier (oxygen (11.85 cm³ m^-2 d^-1 atm^-1) and water vapor (3.22 × 10^-10 g m^-1 s^-1 Pa^-1) permeability rate), optical (opacity index (2.7 AU μm^-1), total color difference (18.69), and whiteness index (77.40)), and thermal (glass transition temperature (-8.29 °C) and melting point (110.38 °C)) properties were obtained at 5.0 % WPI, 15.0 % JPS, and 3.0 % SNCs. The film-forming solution of optimal BNCs had a significant antibacterial effect against Staphylococcus aureus and Escherichia coli. The improved crystallinity of BNCs at an optimal SNC level was confirmed by the XRD. The AFM and SEM images confirmed a continuous and uniform network for the optimal BNCs without any pores or cracks accompanied by low surface roughness. The FTIR spectroscopy proved covalent interaction and hydrogen bonding among chemical functional groups of WPI and JPS reinforced with SNCs. The optimal BNC could preserve banana fruits with favorable physicochemical and microbial quality during storage.

Effect of Molecular Weight and Degree of Substitution on the Physical-Chemical Properties of Methylcellulose-Starch Nanocrystal Nanocomposite Films

This research studied the effect of molecular weight (Mw) and degree of substitution (DS) on the microstructure and physicochemical characteristics of methylcellulose (MC) films with or without SNC. The Mw and DS of three types of commercial MC (trade name of M20, A4C, and A4M, respectively) were in the range of 0.826 to 3.404 × 105 Da and 1.70 to 1.83, respectively. Mw significantly affected the viscosity of methylcellulose solutions as well as the microstructure and tensile strength of methylcellulose films, while DS had a pronounced effect on their oxygen permeability properties. The incorporation of 15% (w/w) SNC resulted in the efficient improvement of tensile strength, water, and oxygen barrier properties of films, particularly for the A4C nanocomposite films. The results from SEM and FTIR illustrated that relatively homogenous dispersion of SNC was distinguished in A4C-15% (w/w) SNC films. Furthermore, microstructures of MC-SNC nanocomposite films were strongly dependent on both Mw and DS of MC. This work offers a convenient and green method to fabricate MC-based nanocomposite films with desirable mechanical, light, oxygen, and water vapor barrier properties.