Here, we discovered that starch could be straightforwardly processed into optically transparent electroconductive films by compression molding at a relatively mild temperature (55 or 65 °C), much lower than those commonly used in biopolymer melt processing (typically over 150 °C). Such significantly reduced processing temperature was achieved with the use of an ionic liquid plasticizer, 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]). A higher [C2mim][OAc] content, lower processing temperature (55 °C), and/or higher relative humidity (RH) (75%) during the sample postprocessing conditioning suppressed the crystallinity of the processed material. The original A-type crystalline structure of starch was eliminated, although small amounts of B-type and V-type crystals were formed subsequently. The starch crystallinity could be linked to the mechanical properties of the films. Moreover, the processing destroyed the original lamellar structure of starch, and the amorphous starch processed with [C2mim][OAc]/water could aggregate on the nanoscale. The films displayed excellent electrical conductivity (>10–3 S/cm), which was higher with a lower processing temperature (55 °C) and a higher conditioning RH (75%). The incorporation of [C2mim][OAc] reduced the thermal decomposition temperature of starch by 30 K, while the formulation and processing conditions did not affect the film thermal stability.Keywords: 1-Ethyl-3-methylimidazolium acetate; Electroconductive films; Energy-saving processing; Ionic liquid; Plasticizer; Starch-based materials;

•CMS/QAS colloidal nanocapsules were fabricated through layer by layer assembly.•Higher DS and lower Mw of CMS improve the encapsulating efficiency of BSA.•CMS with lower DS or Mw benefit to nanocapsules with compact core-shell structure.•Nanocapsules fabricated by CMS with lower DS and Mw showed colon-specific release.•Nanocapsules structural changes in simulated GIT were modulated by DS and Mw of CMS.Anionic carboxymethyl starch (CMS) and cationic quaternary ammonium starch (QAS), were used to fabricate nanocapsules through electrostatic layer by layer (LbL) alternate deposition onto colloidal BSA particles. An ideal starch-based colloidal nanocapsule was achieved by adjusting the degree of substitution (DS) and weight average molecular molar mass (Mw) of CMS. The nanocapsules fabricated by CMS with lower DS or Mw possessed more compact and stable core-shell structure, which favoured the BSA delivery from the upper gastrointestinal tract (GIT) to the colon. In particular, CMS/QAS nanocapsules constructed by CMS with lower DS and Mw showed better colon-specific delivery and release performance in simulated GIT fluid after 7 days’ storage in different kinds of beverage (33.04%-46.35% in upper GIT, 52.70%–64.97% in colon, respectively). These findings demonstrated that CMS/QAS nanocapsules constructed by CMS with lower DS and Mw can be further exploited as a potential oral delivery system for protein to colon.

•Film amylose/amylopectin ratio affected DEP migration during microwave heating.•The strong interaction between starch and DEP of waxy film inhibited DEP migration.•Further amorphization of G50 film in microwave process favored DEP migration.•Damaged crystalline structure of G80 film in microwave process favored DEP migration.•The smallest size of micro-ordered region of G80 film favored DEP migration.Plasticizer, as a necessary processing aid in producing packaging materials, migrated into food stuffs, which caused food safety problems. In order to restraint plasticizer migration, the hydrophobic esterified starch-based films with different multi-scale structures were prepared by regulation the ratio of amylose and amylopectin. The influence of multi-scale structures including molecular interactions between plasticizer and esterified starch, crystalline structure and aggregation structure on inhibition of diethyl phthalate (DEP) migration during microwave heating was studied. As the strongest molecular interactions between starch and DEP, the amount of plasticizer migration in waxy film was lower than that of G50 film and G80 film. Even the largest size of micro-ordered region impeded the DEP movement in G50 film, the serious further amorphization in G50 film amorphous region in microwave process and weaker molecular interactions led to higher DEP migration compared with that of waxy film. The amount of DEP migration in G80 film were the largest which resulted from weaker molecular interactions, damaged crystalline structure during microwave process and the smallest size of micro-ordered region. This study provided a new method to control DEP migration which favored the application of esterified starch-based biodegradable material for food packaging.

•Resistant starch acetate and chitosan were used as delivery carriers for liquid products.•Double polysaccharide film coating thickness determined the immunologic peptide release.•The microparticle delivery system exhibited a good colon-targeting behavior.•Orally administrated microparticles with yogurt showed higher immunologic function.A new carrier system for controlled release of immunologic peptides based on double polysaccharide film-coated microparticles (PCMPs) used with liquid products was developed. The release behavior of PCMPs was shown dependent on the thicknesses of the outer chitosan film and the inner resistant starch acetate (RSA) film. The in-vitro release results indicated that, with optimized polysaccharide coating thickness (RSA: 4–5%; chitosan: 6–7%), the release rate of Thymopoietin (TP5) was less than 30% before the microparticles reached the colon, and was 50% in the colon. Besides, the bioavailability of PCMPs was evaluated based on the cell proliferation and protein expression. Compared with the intraperitoneal injection or oral administration, the immunodeficient rats that were orally administrated with the yogurt containing TP5-loaded PCMPs with different storage times possessed a good colon-targeting behavior, higher ratios of CD4/CD8 and IgG expression, indicating the improvement in the TP5 immunologic function.

•Spermine modified starch (SMS) formed self-assembly nanocomplexes with pDNA.•The NH2 content (DS) of SMS affected the nano-structure of SMS/pDNA complexes.•SMS with the highest DS and pDNA assembled at w/w of 25 achieved best transfection.•Compact nano-structure at acidic pH resulted in superior transfection efficiency.This study aims at developing starch based gene carriers with low cytotoxicity and high transfection efficiency. Starch molecules with molecular weight of about 50 kDa were cationically modified by spermine to obtain spermine modified starch (SMS) based gene carriers. Plasmid pAcGFP1-C1 (pDNA) was chosen as the model gene material and formed self-assembly nanocomplexes with SMS. The cytotoxicity and transfection efficiency of SMS/pDNA complexes were tested in HepG2 cell lines. Results showed that SMS/pDNA complexes formed by SMS-DS3 with the highest primary amine content (1.17 μmol mg−1) and pDNA at the weight ratio of 25 displayed the highest transfection efficiency (∼40%) with low cytotoxicity. Dynamic Light Scattering (DLS) and Small Angel X-ray Scattering (SAXS) investigation under simulated acidified endosomal environments (pH 5.0–7.4) revealed that SMS-DS3/pDNA complexes (∼180 nm) with moderately compact structures within acidic environments (i.e. no significant particle size changes, slightly shrunken shapes) showed superior transfection efficiency.

The effects of non-covalent interactions between gallic acid (GA) and starch on starch digestibility and supramolecular structural changes (short-range ordered molecular structure, crystalline structure, lamellar structure and fractal structure) were investigated. The results indicated that the digestibility of both starches was substantially reduced in the rapidly digestible starch (RDS) content, but resistant starch (RS) was increased after interacting with GA. The RS content of starch–GA complexes ranged from 17.70 to 50.02%, which is much higher than that of high amylose starch (G50) (11.11%) and normal maize starch (NMS) (4.46%). Compared with native starches, starch–GA complexes possess more ordered and compact structures; furthermore, G50–GA complexes possessed more compact scattering objects, thicker crystalline lamellae and thinner amorphous lamellae than those of NMS–GA complexes. This revealed that more ordered multi-scale structures promote the RS formation. Docking studies were conducted to reveal the mechanism of digestibility variations. It showed that GA would non-covalently interact with starch molecules and contribute to ordered structure formation to somewhat extent; meanwhile, GA had higher binding affinities to α-amylase than to starch chains; during the hydrolytic process, GA could be released from the complex and was more likely to occupy the active sites of Asp197, Asp300, His299 and Glu233 by hydrogen bonds and van der Waals forces, which kept starch out of the active site pocket and reduced starch digestibility. These results demonstrate that the non-covalent interactions between GA and starch could be a promising method of controlling starch structures and starch digestion behaviors.

•Plasticised starch films were prepared by a simple compression moulding process.•[C2mim][OAc] suppressed densification in amorphous starch during ageing.•[C2mim][OAc] stabilised starch structure on the nano-scale during ageing.•[C2mim][OAc]-plasticised starch had stabilised structure and mechanical properties.The focus of this study was on the effects of plasticisers (the ionic liquid 1-ethyl-3-methylimidazolium acetate, or [Emim][OAc]; and glycerol) on the changes of starch structure on multiple length scales, and the variation in properties of plasticised starch-based films, during ageing. The films were prepared by a simple melt compression moulding process, followed by storage at different relative humidity (RH) environments. Compared with glycerol, [Emim][OAc] could result in greater homogeneity in [Emim][OAc]-plasticised starch-based films (no gel-like aggregates and less molecular order (crystallites) on the nano-scale). Besides, much weaker starch–starch interactions but stronger starch-[Emim][OAc] interactions at the molecular level led to reduced strength and stiffness but increased flexibility of the films. More importantly, [Emim][OAc] (especially at high content) was revealed to more effectively maintain the plasticised state during ageing than glycerol: the densification (especially in the amorphous regions) was suppressed; and the structural characteristics especially on the nano-scale were stabilised (especially at a high RH), presumably due to the suppressed starch molecular interactions by [Emim][OAc] as confirmed by Raman spectroscopy. Such behaviour contributed to stabilised mechanical properties. Nonetheless, the crystallinity and thermal stability of starch-based films with both plasticisers were much less affected by ageing and moisture uptake during storage (42 days), but mostly depended on the plasticiser type and content. As starch is a typical semi-crystalline bio-polymer containing abundant hydroxyl groups and strong hydrogen bonding, the findings here could also be significant in creating materials from other similar biopolymers with tailored sensitivity and properties to the environment.

For effective oral delivery of polypeptide or protein and enhancement their oral bioavailability, a new resistant starch–glycoprotein complex bioadhesive carrier and an oral colon-targeted bioadhesive delivery microparticle system were developed. A glycoprotein, concanavalin A (Con A), was successfully conjugated to the molecules of resistant starch acetate (RSA), leading to the formation of resistant starch–glycoprotein complex. This Con A-conjugated RSA film as a coating material showed an excellent controlled-release property. In streptozotocin (STZ)-induced type II diabetic rats, the insulin-loaded microparticles coated with this Con A-conjugated RSA film exhibited good hypoglycemic response for keeping the plasma glucose level within the normal range for totally 44–52 h after oral administration with different insulin dosages. Oral glucose tolerance tests indicated that successive oral administration of these colon-targeted bioadhesive microparticles with insulin at a level of 50 IU/kg could achieve a hypoglycemic effect similar to that by injection of insulin at 35 IU/kg. Therefore, the potential of this new Con A-conjugated RSA film-coated microparticle system has been demonstrated to be capable of improving the oral bioavailability of bioactive proteins and peptides.

•HMT displayed an influence on the aggregation structures at different scale levels.•Amylose acted as the backbone of aggregation structures to provide a resistance to HMT.•Phosphate monoester promoted the destruction by HMT to the aggregation structures.•Phosphate monoester played a more significant role in changing the lamellar thickness.For three cultivars of potato starch, heat-moisture treatment (HMT) displayed an influence on the aggregation structures at different scale levels. With HMT, the granular morphology of potato starch granules remained similarly, and an increase in the average repeat distance of semi-crystalline lamellae was observed. The crystalline structure and birefringence were also affected. Moreover, the polymorphic transformation (B → A + B) could be related to dehydration, whereas the decrease in the degree of crystallinity might be resulted from the rupture of hydrogen bonds. Interestingly, amylose could act as the backbone of the aggregation structures of potato starch to provide resistance to HMT, but phosphate monoester could promote the destruction during HMT. In addition, compared with amylose, phosphate monoester played a more significant role in changing the average repeat distance of semi-crystalline lamellae (long period) during HMT.

For the delivery of bioactive components to the colon, an oral colon-specific controlled release system coated with a resistant starch-based film through aqueous dispersion coating process was developed. Starch was modified by a high-temperature–pressure reaction, enzymatic debranching, and retrogradation, resulting in a dramatic increase in the resistibility against enzymatic digestion (meaning the formation of resistant starch, specifically RS3). This increase could be associated with an increase in the relative crystallinity, a greater amount of starch molecular aggregation structure, and the formation of a compact mass fractal structure, resulting from the treatment. The microparticles coated with this RS3 film showed an excellent controlled release property. In streptozotocin (STZ)-induced type II diabetic rats, the RS3 film-coated insulin-loaded microparticles exhibited the ability to steadily decrease the plasma glucose level initially and then maintain the plasma glucose level within the normal range for total 14–22 h with different insulin dosages after oral administration; no glycopenia or glycemic fluctuation was observed. Therefore, the potential of this new RS3 film-coated microparticle system has been demonstrated for the accurate delivery of bioactive polypeptides or protein to the colon.

The octenyl succinic anhydride (OSA) modified corn starch (OSAS) was synthesised with different degrees of substitution (DS) and the influences of three factors namely OSA/starch ratio, reaction temperature, and reaction time on the DS of OSAS were studied by response surface methodology (RSM). As a delivery carrier material, the characteristics of OSAS were investigated. The resistant starch (RS) content of OSAS was increased with increasing DS, indicating the improvement of colon-targeting property. The swelling ratio (SR) of the OSAS in simulated gastrointestinal fluids was higher than that of native starch and its hydrophilicity was decreased with increasing DS. For in vitro release study, the percentage of released bioactive components was less than 7% within the first 8 h and close to 100% over a period of 36 h when the DS was 0.60. These results demonstrate that OSAS can be a potential carrier for colon-targeted delivery of bioactive food components.Research highlights► Octenyl succinate starch with different higher DS is synthesised. ► Increased resistant starch content indicates better colon-targeting. ► Octenyl succinate starch can be a potential carrier for colon-targeted delivery.

•Con A was conjugated to the resistant starch acetate molecules with 8–32 μg/mg.•G′ and Tg changes of Con A-RSA film under simulated GIT conditions were analyzed.•Colon-targeting controlled release can be achieved by adjusting the coupled Con A.•Con A-RSA film coated microcapsules showed good colon-targeting and bioadhesion.•Con A-RSA film is a potential colon-targeting bioadhesive film coating material.For the effectiveness of bioactive ingredient targeting delivery in the gastrointestinal tract (GIT), the concanavalin A (Con A)-conjugated RSA film was developed for the potential bioadhesive coating material for colon-targeting bioadhesive microcapsules which were designed by the method of extrusion–spheronization and film coating process. The Con A-conjugated RSA films with coupled Con A from 8 to 32 μg/mg showed sufficient higher storage modulus (G′) and glass transition temperature (Tg). The G′ and Tg increased as immersion in simulated digestive fluids progressed which allowed the films transformed from a viscoelastic state to a glassy state and is benefit for the bioactive ingredients releasing. Through adjusting the amount of coupled Con A the brittleness time and brittlement of Con A-conjugated RSA film could be adjusted and controlled for matching the colon targeting and releasing performance. The in-vitro and in-vivo study demonstrated that the Con A-conjugated RSA film coated microcapsules have good colon targeting and bioadhensive properties which could not only target bioactive molecules to the colon but also increase the residence time of the microcapsules for 72 h in the colon.

•HMT transformed RDS into SDS and RS for both regular and high-amylose starches.•HMT induced more intense structural disorganizations for high-amylose starch.•HMT was more effective at inducing molecular rearrangements for high-amylose starch.•With HMT, high-amylose starch exhibited a greater increase in the SDS + RS content.To rationalize the effects of heat-moisture treatment (HMT) on starch digestibility, the HMT-induced alterations in the mesoscopic and molecular scale structures of regular and high-amylose maize starches, as well as in their digestibility, were evaluated. Accompanying the supramolecular structural disorganizations and certain molecular degradation induced by HMT, somewhat molecular rearrangements occurred to probably form densely packed starch fractions, which eventually weakened starch digestion and thus transformed RDS into SDS and RS for regular and high-amylose starches. Interestingly, due to its larger amount of inter-helical water molecules that could be induced by HMT, B-polymorphic high-amylose starch was more susceptible to HMT (relative A-polymorphic regular starch), causing more prominent structural evolutions including molecular re-assembly and thus increasingly slowed digestion. In particular, the treated high-amylose starch with 30% moisture content showed a high SDS + RS content (48.3%). The results indicate that HMT-treated starch may serve as a functional ingredient with adjustable enzymatic digestibility for various food products.

•South China 5 (SC5) cassava starches with various growth periods were evaluated.•Growth time led to slight changes in lamellar and crystalline structures.•Pasting behaviors of SC5 starches were apparently altered by growth time.•9 months growth time was the turning point for cassava starch properties.Starches were isolated from South China 5 (SC5) cassava harvested for 7, 8, 9, 10 and 11 months. During growth, the granule size, lamellar structure, crystalline structure and digestibility changed slightly, while the amylose content varied between 20.93% and 22.61%. However, the molecular weight showed an obvious increase as the harvesting time increased to 9 months, and then decreased during 9–11 months. The pasting behaviors were greatly affected by harvesting time. A shorter growth time led to higher pasting temperature, and lower peak, breakdown and setback viscosities. This trend became contrary when the growth time prolonged from 9 to 11 months. Hence, the starch harvested at 9 months showed the lowest pasting temperature (64.6 °C), but highest paste viscosity (2105 cP) and retrogradation tendency. All these results confirm that the growth time of 9 months was the turning point for the physicochemical features of SC5 during growth. This study provides fundamental data for rationally tailoring cassava starch properties by simply controlling the harvest time.

•From a structural point of view, glow-plasma effects on starch thermal behavior were explored.•Glow-plasma degraded starch crystallites with low perfection and thermal stability.•Glow-plasma increased the transition temperature values of cassava starch.•Glow-plasma narrowed the gelatinization temperature range of cassava starch.•Glow-plasma can serve as a technique to modulate starch thermal property.The thermal property of cassava starch was regulated by the oxygen or helium glow-plasma treatment to change its supramolecular hierarchical structure. By investigating the microstructural and mesoscopic scale structural alterations and the thermal transition without and with the glow-plasma treatment, the underlying mechanism was explored through establishing a structure–thermal property relationship. Particularly, while there were negligible changes to the granule morphology, the glow-plasma predominantly disorganized the crystallites with low perfection and thermal stability, resulting in decreased alignment of double-helices within the crystalline lamellae, reduced relative crystallinity and thermal transition enthalpy, and increased transition temperatures accompanied by a narrowed gelatinization temperature range. The thermal transition parameters could be further modulated by simply changing the atmosphere type and treatment time. This is much different from our previous study which showed if glow-plasma disrupted the supramolecular structure of starch, the thermal transition temperatures would be reduced. These findings from present study indicate that the glow-plasma treatment can serve as a highly-safe physical method to rationally regulate the hierarchical structure of cassava starch and thus to realize the development of starch-based products with desired thermal behavior.Industrial relevanceGlow-plasma is a non-thermal physical technique and has gain huge interest in polymer modification due to the concerns over generated wastes and safety issues resulting from chemical modification. As the major storage carbohydrate in higher plants, starch is one of the most important raw materials for food and non-food industries. To improve the performance of starch and extend its applications, it is indispensible to understand how a specific technique alters the structure–property of starch. Regarding this, the present work revealed that the oxygen or helium glow-plasma preferably disorganized the crystallites of cassava starch with low perfection and thermal stability, which resulted in decreases in the relative crystallinity and the transition enthalpy but increases in the transition temperatures together with a narrowed transition temperature range. The thermal behavior of cassava starch could be further regulated by changing the gas type and the treatment time. These findings are much different from a previous work which showed if glow-plasma disorganized the supramolecular structure of starch, its thermal transition temperatures would be reduced. Hence, this study enables an understanding of how glow-plasma modulates the thermal property of cassava starch from a structural view, which is of value for rationally using glow-plasma as a new method to regulate the thermal transition of starch, for the production of starchy food products with desired thermal behavior.

•Breadfruit starch was modified by heat-moisture treatment (HMT).•Moisture of starch played a major role in HMT.•HMT altered the multi-scale structures and properties of starch.•HMT was effective to enhance the enzyme resistance of breadfruit starch.Breadfruit starch was subjected to heat-moisture treatment (HMT) at different moisture content (MC). HMT did not apparently change the starch granule morphology but decreased the molecular weight and increased the amylose content. With increased MC, HMT transformed the crystalline structure (B → A + B → A) and decreased the relative crystallinity. With ≥25% MC, the scattering peak at ca. 0.6 nm−1 disappeared, suggesting the lamellar structure was damaged. Compared with native starch, HMT-modified samples showed greater thermostability. Increased MC contributed to a higher pasting temperature, lower viscosity, and no breakdown. The pasting temperature of native and HMT samples ranged from 68.8 to 86.2 °C. HMT increased the slowly-digestible starch (SDS) and resistant starch (RS) contents. The SDS content was 13.24% with 35% MC, which was 10.25% higher than that of native starch. The increased enzyme resistance could be ascribed to the rearrangement of molecular chains and more compact granule structure.

This study compared the solubility of starch (G50) and microcrystalline cellulose (MCC) in an ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), at different temperatures. From SAXS and WAXS analysis, polysaccharides could be totally dissolved in [Emim][OAc]. Fourier-transform infrared (FTIR) spectra showed a similar dissolution mechanism for starch and MCC, which was related to the formation of hydrogen bonds between polysaccharide hydroxyls and acetic anions, causing the breakage of the hydrogen bonding network of the polysaccharide. The polysaccharide–[Emim][OAc] solutions displayed viscosity in the order of G50–[Emim][OAc] < G50/MCC–[Emim][OAc] < MCC–[Emim][OAc], which led to speculation that the molecular chain of G50 and MCC existed concordantly in [Emim][OAc]. The intrinsic viscosity study showed that G50 was much less temperature-sensitive than MCC, and G50/MCC solutions showed intermediate and tuned behaviors. Steady-shear measurements indicated that for dilute solutions, there was a slightly shear-thinning behavior at low shear rates, and high concentration solutions presented an apparent shear-thinning behavior at high shear rates. These characteristics also reflect the different conformation of polysaccharide chains in the solution, which guides the processing of polysaccharide materials and composites for the desired structure and properties.