Starch as a smart, cheap, and green gatekeeper for the controlled release of propyl gallate from antioxidant biodegradable packaging films.

Oxidative rancidity of food products and massive consumption of plastic packaging have put the necessity in manufacturing novel antioxidant biodegradable packaging films. A comprehensive investigation was conducted on starch/poly(butylene adipate-co-terephthalate) (PBAT) antioxidant blown films, in which starch acted as a gatekeeper for the controlled release of propyl gallate (PG). PG was well integrated into the matrices and bound to starch molecules by hydrogen bonding. All films showed strong anti-ultraviolet performance, and higher oxygen barrier than the traditional polyethylene film. Increasing starch proportions promoted the swelling of films and the release of PG, thereby causing higher antioxidant activity at the same contact time to free radical solutions. Similar polarity made PG prone to partition and rapid migration into the food simulants with higher ethanol concentration and the high-fat-content peanut butter. The film with 20:80 w/w starch/PBAT proportion and 3% w/w PG content effectively suppressed the oxidation of peanut butter within 300-day storage. Findings demonstrated this strategy for manufacturing starch/PBAT antioxidant films as a long-term active packaging in food industry.

Effect of polydimethylsiloxane on the structure and barrier properties of starch/PBAT composite films.

This study aimed to investigate the effects of polydimethylsiloxane (PDMS) with a low surface energy on the structure and physicochemical properties of starch/poly (butylene adipate-co-terephthalate) (PBAT) blown films. The film's appearance was not significantly changed after the addition of PDMS. Compared with the films without PDMS, the films with PDMS displayed a smoother surface. A 2% w/w PDMS addition resulted in the maximum mechanical properties (8.10 MPa of strength, 211.00% of modulus) and surface hydrophobicity (87°) of the films. By contrast, the film with 3% w/w PDMS showed the lowest light transmittance, water vapor (2.73 × 10-11 g·cm·cm2·s-1·Pa-1) and oxygen permeability (9.73 × 10-13·cm3·cm·cm-2·s-1·Pa-1), owing to the improved tightness of the matrix, which increased the zigzag path for molecules to pass through. Films with higher PDMS contents effectively extended the shelf life of packaged bananas and shiitake mushrooms, benefiting from the outstanding and appropriate barrier properties, according to principal component analysis results. Findings supported that high-content starch/PBAT films containing PDMS had potential in the preservation of fresh agricultural products.

A biodegradable pH-response packaging film with blueberry extract: Blown-extrusion fabrication, multifunctional activity, and kinetic investigation.

This work proposed a novel strategy for manufacturing biodegradable pH-response packaging. Briefly, to minimize the amount and thermal processing times of blueberry extract (BE), ethanol-dissolved BE (≤ 3‰ w/w) was sprayed onto the starch/poly(butylene adipate-co-terephthalate) (PBAT) pellets before extrusion blowing. BE was well-integrated into the matrix, forming uniformly colored films. The films with BE exhibited superior mechanical (7.85 MPa of strength, 606.53% of elongation) and enhanced barrier capabilities against ultraviolet light, moisture, and gas. Additionally, they exhibited good antioxidant capacity (68.69%), antibacterial activity (72.40%), and maintained color stability. The film with 3‰ w/w BE presented excellent color responsiveness (ΔE⁎ ≥ 15) in the alkaline range, and successfully monitored the spoilage of shrimp. The pigments in the film had the maximum migration degree (≥ 70%) and rate in 50% ethanol simulation, following a first-order kinetic behavior dominated by Fickian diffusion. Findings supported the application of this strategy in the fabrication of starch/PBAT/BE films for pH-response intelligent packaging.

Influence of enzymatic modification on the basis of improved extrusion cooking technology (IECT) on the structure and properties of corn starch.

Enzymatic modification can directly affect the structure and properties of starch, but generally causes high energy consumption in drying process. Improved extrusion cooking technology (IECT) itself is a starch modification technology. In this work, a co-extrusion method of starch with 42 % moisture and enzyme was adopted to reveal the effects of different enzyme dosages on the structure and properties of corn starch. After enzyme treatment on the basis of IECT, starch granules were broken into fragments without the occurrence of clear Maltese cross. R1047/1022 and R995/1022 values, peak intensity of Raman spectra and gelatinization temperature decreased, and the full width at half maximum at 480 cm-1 of Raman spectra raised. Moreover, the bound water proportion decreased from 87.44 % to 85.84 % âˆ¼ 78.67 %, and the maximum light transmittance and dextrose equivalent values increased to 34.13 % and 26.14, respectively. The solubility of starch granules was all above 60 %. Findings supported that the mechanochemical effect of IECT on starch was conducive to the enzymatic modification.

Starch/poly(butylene adipate-co-terephthalate) blown antimicrobial films based on ε-polylysine hydrochloride and different nanomontmorillonites.

With increasing awareness on environmental protection and food safety, the development of biodegradable antimicrobial packaging materials has been paid growing emphasis. In this work, starch/poly(butylene adipate-co-terephthalate)/ε-polylysine hydrochloride films were prepared by extrusion blowing, and five commercial organically modified nanomontmorillonites (OMMT, including DK1, DK2, DK3, DK4, and DK5) were used as reinforcing agents. Intercalated structures were formed in the nanocomposite films, especially for those with DK3 and DK4 owing to their higher hydrophobicity and larger interlayer spacing. Adding OMMT weakened hydrogen bonds and the gelatinization/plasticization degree of starch. Morphology analysis revealed that the agglomeration of OMMT occurred in the films, but the film containing DK3 still showed a relatively homogeneous microstructure. Loading OMMT enhanced the strength, deformation resistance, thermal stability, surface hydrophobicity, but decreased barrier properties and water sensitivity of the films. Antimicrobial activity showed that the OMMT and ε-polylysine hydrochloride possessed a synergistic effect against Staphylococcus aureus and Escherichia coli. The maximum inhibition rate was observed in that with DK4, approaching 100 %. Findings supported the application of commercial OMMT in manufacturing biodegradable antimicrobial blown films.

Effect of improved extrusion cooking technology (IECT) on structure, physical properties and in vitro digestibility of starch.

Extrusion can modify the structure and physical properties of starch, while the extent of improved extrusion cooking technology (IECT) affects the starch with high moisture content and different crystal types remaining unclear. Therefore, the influence of IECT at different screw speeds on the structure, physical properties and in vitro digestibility of corn (A-type), potato (B-type) and pea (C-type) starches with high moisture content (42 %) was explored. Results indicated that IECT treatment caused similar variations on structure, physical properties, and in vitro digestibility of the 3 types of starches. The contents of slowly digestible starch (SDS) and resistant starch (RS) decreased by IECT treatment, accompanied by a reduction of crystallinity, enthalpy of gelatinization, gelatinization temperature and viscosity, while the content of rapidly digestible starch (RDS) and the ratio of bound water increased. And the changes in in vitro digestibility of starch were closely related to the damage to starch structure caused by IECT. Furthermore, most of starch granules were in the agglomeration stage by appropriate IECT treatment, which induced the exposure of a great quantity of enzyme binding sites to enhance the in vitro digestibility.

The effect of non-thermal physical modification on the structure, properties and chemical activity of starch: A review.

Non-thermal physical treatments has obvious advantages in regulating the structure and properties of starch compared with chemical treatment. Hance, this article summarized and compared the effects of three kinds of non-thermal physical treatments including grinding and ball milling, high hydrostatic pressure and ultrasonic on the structure, properties and chemical activity of starches from different plants. The potential applications of non-thermal physical modified starch were introduced. And strategies to solve the problems in the current research were put forward. It is found that although starch has a dense structure, the starch granules could be deformed under three kinds of non-thermal physical treatments, which could damage the granule morphology, microstructure, and crystal structure of starch, reduce particle size, increase solubility and swelling power, and promote starch gelatinization. Three kinds of non-thermal physical treated starch could be used as flocculant thickener, starch based edible films and fat substitutes. Non-thermal physical treatments caused the structure of starch to undergo three stages, which were similar to mechanochemical effects. When starch was in the stress stage and the transition stage from aggregation to agglomeration, its active sites significantly increase and move inward, ultimately leading to a significant increase in the chemical activity of starch.

Influences of high hydrostatic pressure on structures and properties of mung bean starch and quality of cationic starch.

It is difficult to improve the quality of chemical-modified starch by traditional technology. Hence, in this study, mung bean starch with poor chemical activity was used as raw material, the native starch was treated and the cationic starch was prepared under high hydrostatic pressure (HHP) at 500 MPa and 40 °C. By studying the changes in the structure and properties of native starch after HHP treatment, the influence mechanism of HHP on improving the quality of cationic starch was analyzed. Results showed high pressure could make water and etherifying agent enter the starch granules through pores, and HHP made the structure of starch undergone three stages similar to mechanochemical effect. After HHP treated for 5 and 20 min, the degree of substitution, reaction efficiency and other qualities of cationic starch increased remarkably. Hence, proper HHP treatment could help to improve the chemical activity of starch and quality of cationic starch.

Exploring the mechanism of high hydrostatic pressure on the chemical activity of starch based on its structure and properties changes.

High hydrostatic pressure (HHP) could induce changes in the structure and properties of starch. Native corn starch was treated and octenyl succinic anhydride (OSA)-modified corn starch was prepared under different pressures (200, 350, 500 and 600 MPa) at 40℃ for 20 min. The mechanism of HHP on the chemical activity of starch was elucidated by analyzing the relationship between the changes of native starch structure and properties and the quality of OSA-modified starch. Results showed that HHP not only helped water and OSA to penetrate the starch granules but also made the structure of starch granules undergone three changes similar to mechanochemical effects. The starch granules treated by 200 MPa were in the stress stage, and the starch granules treated by 500 MPa were in the transition stage from aggregation to agglomeration. Proper pressure treatment could significantly improve chemical activity of starch and quality of OSA-modified starch.

Effects of co-plasticization of glycerol and small molecular esters on the physicochemical properties of extrusion-blown high-content starch/poly(butylene adipate-co-terephthalate) films.

BACKGROUND: Poor mechanical and water barrier properties of starch-based films severely restrict their applications as packaging materials. In this study, glycerol was combined with various small molecular esters (SMEs) with different molecular structures to plasticize high-content starch/poly(butylene adipate-co-terephthalate) (80/20, w/w) films (SPFs) prepared by extrusion blowing. The effects of co-plasticization on the physicochemical properties and film-forming mechanism of SPFs were investigated. RESULTS: The addition of glycerides to SPFs reduced intermolecular interaction, increased molecular chain mobility, and decreased glass transition, melting temperatures, and crystallinity. Mechanical and water barrier properties of SPFs were improved significantly with the co-plasticization of glycerol and SMEs. The incorporation of triacetate glyceride increased tensile strength of SPFs by 54% and the water contact angle by up to 95°. The SPF with diacetate glyceride exhibited the minimum water vapor permeability, which decreased by 39%. CONCLUSION: The levels of hydrophilic/hydrophobic groups in SMEs and their molecular weights were essential for the plasticizing effects. Glycerides tended to infiltrate into starch for effective plasticization compared with citrates. The combination of glycerol and glycerides had better plasticizing effects on starch. © 2023 Society of Chemical Industry.

Exploring the influence mechanism of water grinding on the gel properties of corn starch based on changes in its structure and properties.

BACKGROUND: At present, most studies have focused on the preparation of modified starches by dry grinding. As an excellent starch plasticizer, water might enhance the action of grinding on the structure of starch granules, and water grinding might improve the gel properties of starch. Therefore, this article explored the influence mechanism of water grinding on the gel properties of corn starch based on the changes in its structure and properties. RESULTS: The results showed that water grinding could make water enter the starch granules and hydrate the starch molecules, and the starch gelatinized after water grinding for 20 min. Thus, water enhanced the action of grinding on the structure of the starch granules. Under the plasticization and grinding action of water grinding, the mechanochemical effect of the starch granules occurred. When the starch was in the aggregation stage (7.5-10 min), the crystallinity of the starch increased, and the starch molecules rearranged into a more stable structure, which increased apparent viscosity (η), elastic modulus (G') and viscous modulus (G″) of the starch gels. CONCLUSION: Therefore, appropriate water grinding (10 min) contributed to increasing the viscoelasticity of starch gels. This study provided a theoretical foundation for research on improving the properties of starch by mechanical modification in future. © 2023 Society of Chemical Industry.

Extrusion-blown starch/PBAT biodegradable active films incorporated with high retentions of tea polyphenols and the release kinetics into food simulants.

To reduce thermal degradation of tea polyphenols (TP) in final active packaging materials, poly(butylene adipate-co-terephthalate) (PBAT), starch, plasticizer, and TP were directly synthesized into masterbatches by one-pot method in this study without pre-dispersion, and then blown into active films. TP interacted with starch through hydrogen bonds, with little interaction with PBAT. Barrier properties were improved by incorporating TP into the films, whereas mechanical properties slightly decreased. Blending starch into PBAT greatly accelerated the degradation of the film. And the incorporation of TP slowed down the short-term degradation of the starch/PBAT film, but accelerated the long-term degradation. The initial total polyphenol content in the active film was positively related to the TP loading, whereas the initial retention rate remained above 95 % regardless of TP loadings. The retention rate of TP in active films decreased with storage time, but it was still above 80 % after 12 months, with a favorable stability. TP-loaded films displayed efficient antioxidant and antimicrobial activities with strong dose dependence. The release of TP into food simulants was mainly induced by random diffusion, with little effect from polymer swelling. The short-term release kinetics was well described by Fick's second law. This work has demonstrated the feasibility of TP being incorporated into the active films with high retention through high-throughput fabrication, which provides formula and technical options for the industrial development of active packaging materials.

Effects of natural wax types on the physicochemical properties of starch/gelatin edible films fabricated by extrusion blowing.

To address the limitation of strong hydrophilicity of edible films, starch/gelatin (S/G) films incorporated with natural waxes (beeswax (BW), candelilla wax (CL), and carnauba wax (CB)) were fabricated by extrusion blowing. Rheological analysis demonstrated that the incorporation of natural waxes reduced storage modulus and complex viscosity of S/G blends. BW and CL weakened molecular interactions among film components, whereas CB did not. CB exhibited the strongest crystalline behavior after film formation. The degree of starch gelatinization and water vapor barrier property of films depended on wax type. The presence of waxes increased the water resistance and surface hydrophobicity of the films. However, CL and BW addition decreased the tensile strength of films. The highest water contact angle (102.6°), strongest thermal stability, and lowest water vapor permeability were found in S/G-BW film, which could be the optimal choice to produce highly hydrophobic edible films.

Relationship between phase morphologies and mechanical properties of thermoplastic starch/poly(butylene adipate-co-terephthalate) composite films prepared by extrusion blowing.

Biodegradable films with various weight proportions of thermoplastic starch (TPS) and poly(butylene adipate-co-terephthalate) (PBAT) were prepared by extrusion blowing. Relationship between phase morphologies and mechanical properties of TPS/PBAT composite films was investigated and discussed. Iodine dyeing technique was used to clearly identify TPS and PBAT phases in the composite films. Such blending systems proved to be immiscible and the phase morphology evolution with changes in TPS/PBAT proportions was elucidated. Two phase transition points were found near PBAT content of 30 and 70 wt%, respectively, where mechanical properties of the composite films leaped. Significant correlations were established between mechanical properties and continuity indices of the two phases, namely a positive correlation with continuity index of PBAT and a negative correlation with that of TPS. Inducing the formation and enhancement of continuous structure of PBAT phase is proposed as a practical approach to improve mechanical properties of TPS/PBAT composite films.

Does environmental regulation lessen health risks? Evidence from Chinese cities.

Introduction: Atmospheric pollution is a severe problem confronting the world today, endangering not only natural ecosystem equilibrium but also human life and health. As a result, governments have enacted environmental regulations to minimize pollutant emissions, enhance air quality and protect public health. In this setting, it is critical to explore the health implications of environmental regulation. Methods: Based on city panel data from 2009 to 2020, the influence of environmental regulatory intensity on health risks in China is examined in this study. Results: It is discovered that enhanced environmental regulation significantly reduces health risks in cities, with each 1-unit increase in the degree of environmental regulation lowering the total number of local premature deaths from stroke, ischemic heart disease, and lung cancer by approximately 15.4%, a finding that remains true after multiple robustness tests. Furthermore, advances in science and technology are shown to boost the health benefits from environmental regulation. We also discover that inland cities, southern cities, and non-low-carbon pilot cities benefit more from environmental regulation. Discussion: The results of this research can serve as a theoretical and empirical foundation for comprehending the social welfare consequences of environmental regulation and for guiding environmental regulation decision-making.

Effects of adding methods and modification types of cellulose on the physicochemical properties of starch/PBAT blown films.

This study revealed the relationship between cellulose types/adding methods and film properties, in which sodium carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), and microcrystalline cellulose (MCC) were added into starch/PBAT blown films in powder, aqueous solution, and emulsion forms, respectively. Cellulose interacted with starch networks via hydrogen bonds, and those added in emulsion form made more homogeneous film morphologies. MCC emulsion enhanced the film strength (40%) and modulus (149%) to the greatest extent, while comprehensively, HPMC emulsion possessed better reinforcement effects on the films, which increased mechanical properties (31% ~ 100%), moisture barrier (20%), oxygen barrier (93%), surface hydrophobicity (20%), as well as water resistance (12% ~ 76%). Findings supported the application of cellulose in high-throughput biodegradable films, and the high-content starch/PBAT blown films reinforced by HPMC emulsion had great potential in commercial packaging fields.

Effects of beeswax emulsified by octenyl succinate starch on the structure and physicochemical properties of acid-modified starchfilms.

This work aimed to develop a novel strategy to modulate the distribution of beeswax in acid-modified starch films via tuning octenyl succinate starch (OSS) ratios and to elucidate their structure-property relationships. The apparent viscosity and storage modulus of the film-forming solution decreased with the increase of OSS ratio. Attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy revealed that the hydrogen bond in the film-forming network was cleaved with the presence of OSS. Scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD) demonstrated that OSS ratio had an obvious effect on the formation and distribution of beeswax crystal particles. Uniform distribution of beeswax effectively enhanced the hydrophobicity and water barrier properties of films and performed preferable elongation at break but at the expense of tensile strength and optical properties. The films with higher OSS ratio (>12 %) presented higher thermal stability. This study provides new information on the rational design of emulsified films to obtain desirable physicochemical properties by tuning the distribution of beeswax.

Effects of soybean oil on rheological characteristics of dough under high hydrostatic pressure.

In order to improve the stability of dough with soybean oil, this article explored the effect of soybean oil addition on the rheological characteristics of dough under high hydrostatic pressure. The results showed that, compared with the dough without soybean oil, the ß-sheet, disulfide bonds content, and gauche-gauche-gauche in the dough increased by 4.23%, 0.85 µmol/g, and 4.16%, respectively when the dough was added with 6% soybean oil, which improved the degree of cross-linking polymerization of gluten protein and the stability of gluten network. Meanwhile, the dough had the highest elastic modulus and the lowest maximum creep compliance (6.85 × 10-4 Pa-1 ), indicating that 6% soybean oil significantly increased the elasticity and hardness of the dough. The results of short-range ordered structure and paste properties showed that with the addition of soybean oil, the ordered structure and paste viscosity decreased with the increase of soybean oil.

Preparation and evaluation of agar/maltodextrin-beeswax emulsion films with various hydrophilic-lipophilic balance emulsifiers.

The structural and physicochemical properties of agar/maltodextrin-beeswax films in the presence of three emulsifiers, including glycerol monostearate, sodium stearoyl lactylate, and polysorbate 80 were investigated. Scanning electron microscopy revealed that addition of lower hydrophilic-lipophilic balance value emulsifiers produced smaller size and more uniform distribution of beeswax in the film matrix. X-ray diffraction and differential scanning calorimetry indicated that the emulsifiers with lower hydrophilic-lipophilic balance values promoted the compatibility between agar/maltodextrin and beeswax more effectively. The incorporation of different emulsifiers showed diverse impacts on the film network structure and physicochemical properties. Agar/maltodextrin-beeswax-polysorbate 80 film showed maximum stiffness (861.99 MPa). Agar/maltodextrin-beeswax-glycerol monostearate film exhibited the highest tensile strength (26.79 MPa), elongation at break (31.83%), water vapor barrier (7.64 × 10-13 g·m-1·s-1·Pa-1) and oxygen barrier properties (3.82 × 10-17 cm2·s-1·Pa-1), which could be more effective for packaging foods that are prone to oxidize.

Antimicrobial starch/poly(butylene adipate-co-terephthalate) nanocomposite films loaded with a combination of silver and zinc oxide nanoparticles for food packaging.

Antimicrobial starch/PBAT films with the combination of silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) were prepared by extrusion blowing. SEM demonstrated the relatively homogeneous distribution of nanoparticles on the fracture surfaces of the nanocomposite films. The incorporation of nanoparticles improved mechanical and barrier properties of the film. The UV-vis spectroscopy revealed that the SP-ZnO(1) film had the highest UV-absorbance. The inhibition effects of the nanocomposite films against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria were observed. The antimicrobial efficiency of SP-Ag(0.8)-ZnO(0.2) and SP-Ag(0.6)-ZnO(0.4) films reached more than 95% within 3 h of contact. The combination of AgNPs and ZnONPs into starch/PBAT blends showed synergistic effects on improving material properties and antimicrobial efficiency of the films. Furthermore, preliminary packaging studies on peaches and nectarines revealed that the antimicrobial films inhibited spoilage of fresh produce and extended their shelf life compared with commercial LDPE packaging films.