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Abstract Starch in pasta is slowly digested, which is nutritionally advantageous because it reduces post-prandial glycemia, a risk factor for type 2 diabetes. We examine the role of proteinaceous amylase inhibitors, providing insights into how wheat proteins slow starch digestion. Gluten samples were extracted in the laboratory and also commercially obtained, and incubated in water at 37 °C and 100 °C. The centrifuged supernatant and gluten pellet were incubated with porcine α-amylase, and enzymatic activity measurement revealed that the supernatant from gluten heated to 100 °C retained the capacity to significantly reduce amylolytic activity. Confocal microscopy showed that the gluten pellet had become porous following heat treatment. These results are consistent with an increased concentration of soluble proteins after cooking. Proteins in the soluble fraction and gluten pellet were identified with mass spectrometry proteomics, which screened a limited number of endogenous double-headed α-amylase/trypsin inhibitors (α-AI(s)), found to be enriched in the supernatant after cooking. Endogenous α-AI(s) play a role in slowing starch digestion by interacting with α-amylase as it penetrates the gluten network that entraps the starch, resulting in an immobilization of the enzyme onto the gluten network, so that the digestion of starch entrapped by the gluten network is inhibited. Graphical abstract Wheat gluten network contains highly thermally stable proteinaceous α-amylase inhibitors that interact and complex with the α-amylase to inhibit the starch digestion. Image 1 Highlights • Slow starch digestion in pasta is nutritionally advantageous. • Thermostable α-amylase inhibitors (α-AI(s)) present in gluten network. • Proteomics screened limited number of probable target α-AI(s). • Endogenous α-AI(s) slow starch digestion by interacting with α-amylase. [ABSTRACT FROM AUTHOR]

Australian wild rices have significant genetic differences from domesticated rices, which might provide rices with different starch molecular structure and thus different functional properties. Molecular structure, gelatinization properties, and pasting behaviours of starch of three Australian wild rices ( Oryza australiensis , taxa A ( O. rufipogon like) and taxa B ( O. meridionalis like)) were determined and compared to domesticated indica and japonica rice. These had higher amylose content, more shorter amylose chains and fewer short amylopectin chains, resulted in a high gelatinization temperature in these wild rices. Compared to domesticated japonica rice, taxa A had a lower pasting viscosity; taxa B had a similar pasting viscosity but lower final viscosity. The significantly different starch molecular structure from that of normal domesticated rices, and concomitantly different properties, suggest advantageous uses in products such as rice crackers or rice pudding, and a source of nutritionally-desirable slowly digestible starch. [ABSTRACT FROM AUTHOR]

The roles that the compact structure and proteins in pasta play in retarding evolution of starch molecular structure during in vitro digestion are explored, using four types of cooked samples: whole pasta, pasta powder, semolina (with proteins) and extracted starch without proteins. These were subjected to in vitro digestion with porcine α-amylase, collecting samples at different times and characterizing the weight distribution of branched starch molecules using size-exclusion chromatography. Measurement of α-amylase activity showed that a protein (or proteins) from semolina or pasta powder interacted with α-amylase, causing reduced enzymatic activity and retarding digestion of branched starch molecules with hydrodynamic radius ( R h ) < 100 nm; this protein(s) was susceptible to proteolysis. Thus the compact structure of pasta protects the starch and proteins in the interior of the whole pasta, reducing the enzymatic degradation of starch molecules, especially for molecules with R h > 100 nm. [ABSTRACT FROM AUTHOR]

Abstract: Biodegradable superabsorbent polymers (SAPs) were prepared by grafting acrylamide onto starches then crosslinking with N,N′-methylene-bisacrylamide. This work focused on the effects of the amylose/amylopectin ratio of starches from the same source (corn) on the grafting reactions and performance of the resultant starch-based SAPs. To characterise each SAP, the acrylamide groups grafted onto the starch were detected by FTIR; grafting ratio and grafting efficiency were evaluated by a gravimetric method; and graft position and the length of the grafted segment were investigated by NMR. The relationships between the microstructures of the starches, and the graft reactions and performance of the SAPs were studied based on the amylose content in the starches. It was found that under the same reaction conditions, the grafting ratio and efficiency increased with increasing amylose content, which corresponds with water absorption ratio. NMR results indicated that the acrylamide group mainly grafted onto C6, and that the length of the grafted segment decreased with increasing amylopectin content in general, and in particular for waxy starch. The high molecular weight and branched structure of amylopectin reduced the mobility of the polymer chains and increased viscosity, which could explain the graft reactions and performance of the starch-based SAPs. [Copyright &y& Elsevier]

[Display omitted] • Heating lignin above 300 °C decreases lignin solubility and transforms lignin surface structure. • Insoluble lignin derived by thermal processing reduces the apparent α-amylase hydrolysis rate. • Thermally modified insoluble lignin slows digestion of starch and pasta in in vitro models. Lignin, despite being the second most abundant constituent of plant cell walls, is thought to be chemically inert during gastrointestinal digestion and therefore attracts little attention for its role in the human diet. This study explores the heat modifications of lignin to derive species capable of slowing starch digestion in vitro. We applied various advanced biochemical (e.g. enzymic digestion, solubility) and physio-chemical (e.g. scanning electron microscopy, Fourier-Transform-Infrared Spectroscopy, 13C-NMR) analyses to characterize the structure-function of lignin induced by heat treatment. It was found that lignin thermally processed above 300 °C reduced the apparent hydrolysis rate of pancreatic α-amylase, which is ascribed mainly to the insoluble lignin with a modified particle surface morphology. Further kinetic experiments showed that lignin species derived by thermal processing slowed in vitro digestion rates of potato starch and pasta. These findings highlight the potential for utilizing thermally processed lignin in slowing digestion of starchy foods. [ABSTRACT FROM AUTHOR]

Starch molecular structural effects in duckweed (Lemna minor and Landoltia punctata) controlling in vitro enzymatic degradation kinetics was studied. The molecular size distributions of fully-branched starches and the chain length distributions (CLDs) of enzymatically debranched duckweed starches were obtained using size-exclusion-chromatography (SEC). The CLDs of both debranched amylose and amylopectin were fitted with models using biologically-meaningful parameters. While there were no significant correlations between amylose content and starch degradation rate, the total amounts of amylose with shorter chain length negatively correlated with undigested starch content, and the amount of amylopectin long chains negatively correlated with the degradation rate coefficient. This provides new knowledge for the utilization of duckweed starches in bioethanol production. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Background Starch is a complex branched glucose polymer, mainly comprising amylose and amylopectin. The number of individual chains as a function of the number of monomer units they contain, i.e. the chain-length distributions (CLDs), are controlled by the underlying biosynthetic process occurring during plant growth. CLDs are currently commonly related to biosynthetic processes and to functional properties by dividing into arbitrarily chosen regions. However, this empiricism is not completely satisfactory: conclusions can depend on the choice of division. Biosynthesis-based models replacing this arbitrary division by model-based parameterization have been developed, but are presently rarely used, because of the complex underlying mathematics. Scope and approach These models are summarized in non-mathematical language. These give information on the biosynthetic processes producing the starch, and yield a parameterization of CLD data to give a fit that is essentially the same as experiment. Additionally, the models are sufficiently flexible that they can also fit data for modified starches. This enables the whole CLDs for both amylose and amylopectin as a small number of parameters which can be used to find statistically-valid structure-property relations. Key findings and conclusions The underlying theory and data-fitting methodology can be used both to better understand starch biosynthesis, to see what structural features control functional properties and to deduce mechanisms for observed correlations. This enables raw materials to be chosen in non-empirical ways to select and process grains and other starch sources for improved foods and other products. Highlights • Starch molecular structure: a major determinant of properties of starch-based foods. • The fundamental structural level is the chain-length distribution (CLD). • Finding structure-property relations needs non-empirical CLD parameterization. • Biosynthetic models enabling this are explained in a non-mathematical way. • This enables publicly-available code to be readily used to find such relations. [ABSTRACT FROM AUTHOR]

Correlations among barley protein, starch molecular structure and grain size were determined using 30 barley samples with variable protein contents. Starch molecular structure was characterized by fluorophore-assisted carbohydrate electrophoresis and by size-exclusion chromatography (SEC, also termed GPC). The chain-length distributions of amylopectin were fitted using a mathematical model reflecting the relative activities of starch branching enzymes and starch synthase enzymes. Increased protein content significantly and negatively correlated with higher amounts of amylose with longer chains (degree of polymerization, DP 1600–40000) while barley grain sizes positively associated with starch contents. Protein content also positively correlated with the proportion of longer chains of amylopectin (DP 34–100). These results showed that the enzyme activities of starch synthases change with protein content, leading to altered starch contents, structures and grain sizes. From this perspective, selecting for large grain size (or low protein content) does not necessarily relate to starch structure, although may suggest long chains of amylopectin. Measuring starch structure could give a good indication of process performance in human food, animal feed and brewing, as all these structural features contribute to significant functional properties. [ABSTRACT FROM AUTHOR]

Abstract: Nanosized hemoglobin-based oxygen carriers are one of the most promising blood substitutes. In the present study, a comprehensive strategy for the preparation of nanosized cationic amylose-encapsulated hemoglobins (NCAHbs) was developed. First, cationic amylase (CA) was synthesized from amylose and quaternary ammonium salt by an etherification reaction. The structure of CA was characterized using Fourier transform infrared spectrophotometry (FTIR) and proton nuclear magnetic resonance spectrophotometry (1H NMR). The degree of substitution and the zeta potential were also measured. Then, the NCAHbs were prepared by electrostatic adhesion, reverse micelles and cross-linking. The UV–visible spectrophotometer was used to measure the entrapment efficiency (EE%) and drug loading efficiency (DL%) of the NCAHbs. Transmission electron microscopy and Malvern Nano-zs 90 analyzer were used to observe the size distribution and morphology of particles. Chemical structure was determined from the FTIR spectrum. A Hemox analyzer was used to measure the P50 and Hill coefficients. A lethal hemorrhagic shock model in rats was used to evaluate the therapeutic effect of the NCAHbs. The results showed that the combined methods improved the size, stability, EE%, DL%, and oxygen-carrying capacity of the NCAHbs. The average diameter of the NCAHbs was 92.53 ± 3.64 nm, with a narrow polydispersity index of 0.027. The EE% was 80.05% ± 1.56% and DL% was 61.55% ± 1.41%. The P50 and Hill coefficient were equal to 28.96 ± 1.33 mmHg and 2.55 ± 0.22, respectively. The size of NCAHbs remained below 200 nm for six days in PBS solution. The NCAHbs could effectively prevent lung injury from progressing to lethal hemorrhagic shock because they acted as both a volume expander and an oxygen carrier. [Copyright &y& Elsevier]

Abstract: Various edible starch films were prepared via extrusion, with a particular focus on the effects of the amylose content of starches from the same resource (corn) on film processibility and performances. Four corn starches with different amylose contents (4.3–77.4%) were used as model materials. The effects of various extrusion processing conditions, such as temperature, screw speed, feeding rate, and water content were systematically investigated. It was found that, while a higher amylose content increased the difficulty of extrusion processing, this could be overcome by increasing the processing temperature, moisture content, and equilibration time. On the other hand, mechanical testing, differential scanning calorimetry, dynamic mechanical analysis, and microscopy showed that films based on higher amylose starch had better mechanical and thermal properties. The reasons include not only the easy entanglement of long linear amylose chains, but also the retained granular structure in high-amylose films, which may act as self-reinforcement. [Copyright &y& Elsevier]

This work concerns how the multi-scale supramolecular structure of starch relates to its digestion rate from a view of structural heterogeneity. The untreated granule starch displayed a dual-phase digestion pattern, ascribed to two digestible fractions within the heterogeneous multi-scale structure of starch, which had prominently different digestion rates. Not only amorphous starch but also part of molecular orders (crystallites with flaws) were digested at a same rate k 1 at the first phase; densely-assembled starch including orders with fewer flaws was digested at a rather slow rate k 2 ( ca . 2/5 of k 1 ) at the second phase. When alkali altered the heterogeneous supramolecular structure of starch, the digestion behaviors were also changed. The 0.1% (w/v) alkali solution slightly disrupted the starch multi-scale structure, which reduced the molecular orders, disrupted the lamellae, weakened the molecular organization within growth rings, and enlarged the granule pores. Then, part of resistant starch was transformed into slowly-digestible fraction with a digestion rate close to k 2 . In contrast, when stronger (0.5% w/v) alkali was used, the starch multi-scale structure was more apparently disrupted, causing even granule swelling. This structural change resulted in a triple-phase digestion with three different digestion rates. Moreover, especially with stronger alkali, along with the structural disruption, some orders with a higher thermal stability emerged and reduced the accessibility of starch molecules to the enzyme. In this case, the digestion rate decreased with the treatment time. [ABSTRACT FROM AUTHOR]

The flexible film is widely applied in the modern electronic industry, whilst it is still challenging to use biopolymer substrates (e.g., starch) to prepare flexible film well-performed in conductivity and fluorescence. In the study, a novel conductive, fluorescent, and flexible biopolymer film was prepared via a cost-effective method by fabricating the nitrogen-doped oxide-reduced graphene quantum dots (N-rGO-QDs) into the thermoplastic starch (TPS) substrate. TPS/N-rGO-QDs film with 10 wt% N-rGO-QDs showed the desirable lowest resistivity (0.082 Ω·m), acceptable light transmittance (60–80 %), and durable fluorescence intensity (9000 CPS). The results reveal a novel starch-based multifunctional film with satisfactory electrical and fluorescent performances, which is hypothesized potential to be applied in some frontier domains, like human wearable devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Starch-based foods frequently contain different starch digestible fractions, with distinct digestion rates and locations in human upper gastrointestinal tract. Understanding the physical basis for these starch components is critical for developing foods with low glycemic index (GI) values. Conducting first-order kinetics analysis has been able to extract information on starch digestion properties, with solid physical basis. However, there is currently no clear procedure in terms of defining different starch fractions by first-order kinetics analysis. This review proposes that starch-based foods can be categorized as structurally homogenous or heterogenous starch systems by fitting their starch digestograms to the first-order kinetics model, which are characterized by a single set or multiple sets of digestion rate constants and the fractions remaining undigested at long times during in vitro digestion. In line with starch hierarchical structures, it helps understand the structural origins for different starch components in foods, which can ultimately help the development of functional foods with low GI. Procedure to identify the starch fractions in starch-based foods to better understand their physical basis. SF is single fraction. RDF represents rapidly digestible starch fraction, while SDF represents slowly digestible starch fraction. [Display omitted] • Starch-based foods often contain multiple starch fractions. • These foods can be defined as structurally homogeneous or heterogenous foods. • This definition helps the understanding of physical basis for starch digestibility. [ABSTRACT FROM AUTHOR]

Combined analytical techniques were used to explore the effects of alkali treatment on the multi-scale structure and digestion behavior of starches with different amylose/amylopectin ratios. Alkali treatment disrupted the amorphous matrix, and partial lamellae and crystallites, which weakened starch molecular packing and eventually enhanced the susceptibility of starch to alkali. Stronger alkali treatment (0.5% w/w) made this effect more prominent and even transformed the dual-phase digestion of starch into a triple-phase pattern. Compared with high-amylose starch, regular maize starch, which possesses some unique structure characteristics typically as pores and crystallite weak points, showed evident changes of hierarchical structure and in digestion rate. Thus, alkali treatment has been demonstrated as a simple method to modulate starch hierarchical structure and thus to realize the rational development of starch-based food products with desired digestibility. [ABSTRACT FROM AUTHOR]