Isoamylase (Glycogen 6-glucanohydrolase)

This study investigated leachate and morphological properties of electric-cooked rice (ECR), electric pressure-cooked rice (EPCR), and instant cooked rice (ICR) to explore the effects of cooking methods on eating quality of cooked rice. The leachate was obtained by rinsing cooked rice with warm water. EPCR had the highest amounts of total solid and amylopectin in the leachate and the highest contents of surface and bound lipid. The amylopectin branch chain length of leachate was not significantly different among rice samples. EPCR leachate solution showed the highest apparent viscosity and the greatest decline with increasing shear rate due to high amount of amylopectin. In morphological characteristics, degrees for disruption of the starch structure and compression of protein present in rice kernel were largest in EPCR. Textural hardness of ICR was much lower than that of ECR or EPCR. EPCR had the highest glossiness, stickiness, moistness, and overall acceptability scores. Principal component analysis score plot showed significant differences in leachate and textural characteristics of cooked rice according to cooking methods.

Sweet potato was planted at three soil and air temperatures (21, 25 and 28°C) with the same humidity and light time/intensity. Root tuber starches were isolated, and their multi-scale structures were investigated to reveal the effects of growth temperature on starch properties. Growth temperature did not change the morphology and amylose content of starch, but markedly increased the size of starch from volume-weighted mean diameter 12.2 μm to 17.0 μm. Starch grown at high growth temperature exhibited less A branch-chains and lower branching degree of amylopectin and more B2 and B3+ branch-chains of amylopectin than at low growth temperature. With increasing growth temperature, starch changed from C_C-type to C_A-type, its relative crystallinity and lamellar peak intensity increased, and the thickness of crystalline and amorphous lamellae did not significantly change. Starch grown at high growth temperature exhibited significantly higher gelatinization temperature than at low growth temperature, but had similar gelatinization enthalpy.

Glycogen dysregulation is a hallmark of aging, and aberrant glycogen drives metabolic reprogramming and pathogenesis in multiple diseases. However, glycogen heterogeneity in healthy and diseased tissues remains largely unknown. Herein, we describe a method to define spatial glycogen architecture in mouse and human tissues using matrix-assisted laser desorption/ionization mass spectrometry imaging. This assay provides robust and sensitive spatial glycogen quantification and architecture characterization in the brain, liver, kidney, testis, lung, bladder, and even the bone. Armed with this tool, we interrogated glycogen spatial distribution and architecture in different types of human cancers. We demonstrate that glycogen stores and architecture are heterogeneous among diseases. Additionally, we observe unique hyperphosphorylated glycogen accumulation in Ewing sarcoma, a pediatric bone cancer. Using preclinical models, we correct glycogen hyperphosphorylation in Ewing sarcoma through genetic and pharmacological interventions that ablate in vivo tumor growth, demonstrating the clinical therapeutic potential of targeting glycogen in Ewing sarcoma.

The structure and physicochemical properties of starch isolated from the cotyledon and hull of faba beans and from wheat (as reference) were examined using 16 different methods. The amylose content in faba bean cotyledon and hull starch was 32% and 36%, respectively, and that in wheat starch was 21%. The faba bean cotyledon and hull starch were structurally alike both displaying C-polymorphic pattern, a similar degree of branching and similar branch chain length distributions. Wheat starch had a significantly greater prevalence of short amylopectin chains (DP < 12) and a higher degree of branching. Granules in both faba bean starches exhibited surface cracks and were more homogenous in size than the smoother wheat starch granules. Gelatinisation temperature was higher for the faba bean starches, likely as an effect of high amylose content and longer starch chains delaying granular swelling. Cotyledon starch produced pastes with the highest viscosities in all rheological measurements, probably owing to larger granules. Higher prevalence of lipids and resistant starch reduced the viscosity values for hull starch. For all starches, viscosity increased at faster heating rates. During the rheological analyses, the samples were exposed to different instruments, heating rates and temperatures ranges, differing from standard rheological procedures, which could help predict how different processing techniques effect the final starch textures.

Starch, being a polymer of excessive demand for the development of products of pharmaceutical importance, has been tremendously treated in many ways for improving the desired characteristics such as viscosity, paste clarity, digestibility, swelling, syneresis, and so forth. In the present study, alkali-extracted starch of mandua grains (Eleusine coracana; family Poaceae) was treated with epichlorohydrin for cross-linking and the modified starch was assessed for swelling, solubility, water binding capacity, moisture content, and degree of cross-linking. The digestion resistibility of modified starch was analyzed in simulated gastric fluid (pH 1.2), simulated intestinal fluid (pH 6.8), and simulated colonic fluid (pH 7.4). The structural modifications in treated mandua starch were analyzed by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy, thermogravimetric analysis, and C¹³ nuclear magnetic resonance (¹³C NMR). The results of the study reflected the significant modification in mandua starch after treatment with epichlorohydrin (1.0% w/w sdb, solid dry basis). The degree of cross-linking of treated mandua starch was 85.15%, and the swelling capacity of mandua starch changed from 226.51 ± 2.175 to 103.14 ± 1.998% w/w after cross-linking with epichlorohydrin. A remarkable increment in digestion resistibility was observed in modified mandua starch. The XRD pattern and FTIR spectra revealed the presence of resistant starch after chemical modification. The decomposition pattern of modified mandua starch was also different from extracted mandua starch. All the results reflected the effective modification of mandua starch by epichlorohydrin and the formation of resistant starch to a significant content. The treated mandua starch may have the potential in developing various preparations of food, nutraceuticals, and pharmaceuticals.

Glycogen branching enzymes (GBEs) have been used to generate new branches in starches for producing slowly digestible starches. The aim of this study was to expand the knowledge about the mode of action of these enzymes by identifying structural aspects of starchy substrates affecting the products generated by different GBEs. The structures obtained from incubating five GBEs (three from glycoside hydrolase family (GH) 13 and two from GH57) on five different substrates exhibited minor but statistically significant correlations between the amount of longer chains (degree of polymerization (DP) 9-24) of the product and both the amylose content and the degree of branching of the substrate (Pearson correlation coefficient of ≤−0.773 and ≥0.786, respectively). GH57 GBEs mainly generated large products with long branches (100-700 kDa and DP 11-16) whereas GH13 GBEs produced smaller products with shorter branches (6-150 kDa and DP 3-10).

Supramolecular polymers are the most used materials for 3D printing applications because of their ability to improve the flow behavior of inks, and consequently enhance the mechanical strength of printed architectures. However, their interactions are assessed without considering the fact that their formed structures are affected by the printing process. Here, the effects of printer temperature of an extrusion-based printing system, or surface temperature of a laser powder bed fusion printer, on the molecular behavior of starch were investigated. Starch, being a highly branched polymer, was selected as the tested biopolymer since it provides numerous noteworthy benefits for an investigation of the depolymerization/crosslinking mechanisms upon printing, which could shed light on the impact of 3D printing on non-degradable materials. Completely different behaviors of starch functional properties are found between the two printing systems, where the extrusion-based printer promoted a significant degradation of the starch chains, while the laser powder bed fusion offered a typical behavior associated with crosslinking/branching. Extrusion 3D printing induced a reduction in starch molecular size and therefore in the structural strength of networks formed from it. However, this was also found to increase the starch digestibility rate/extent. In contrast, laser powder bed fusion increased the molecular size, inducing a viscoelastic gel-like character. At the same time, it decreased the starch digestion rate/extent. The obtained data offers information that can support the mechanistic interpretation of the depolymerization/crosslinking kinetics on the non-degradable materials, where it may be much harder to obtain the branch-length distribution. Therefore, the mechanistic information provided from starch can also be useful in understanding the degradation/chain branching of synthetic branched polymers undergoing the same printing processes.

To reduce the wheat-flour-based food texture and flavor deterioration caused by starch retrogradation, herein wheat starch, the most ingredient in wheat flour, was modified by transglucosidase to delay long-term retrogradation of wheat starch. The study proposed promising data of transglucosidase-treated starch about structure, crystallinity and retrogradation kinetics. Structural properties showed that transglucosidase treatment shortened the average chain length from 19.49 to 16.10 and induced the dominance of amorphous state. Moreover, branching degree increased from 14.11% to 17.97% after transglucosidase treatment, resulting in higher water mobility. Amylose content increased from 25.33% to 59.00% due to the hydrolysis ability of transglucosidase. Relative crystallinity of the retrograded starches decreased from 24.33% to 14.50%. Furthermore, the Avrami parameters demonstrated that transglucosidase treatment significantly retarded the retrogradation rate of wheat starch due to the decrease of re-crystalline rate. The outcoming would supply a solid theory foundation for exploring the wheat staple foods with higher qualities.

To investigate the physicochemical, structural, and rheological characteristics of starch from wheat cultivars varying in grain hardness index employed in making jiuqu and to interrelate grain hardness index with physicochemical and structural properties of starch. Starch extracted therefrom was investigated for structural and physicochemical properties. Starch granules showed relatively wide granule size distribution; large size granules showed lenticular shapes while medium and small size granules exhibited spherical or irregular shapes. Starch from wheat with a lower grain hardness index exhibited a relatively higher degree of crystallinity. Chain-length profiles of amylopectin showed distinct differences; among the fractions of fa, fb₁, fb_2, and fb₃ representing the weight-based chain-length proportions in amylopectin, the fa fractions ranged from 19.7% to 21.6%, the fb₁ fractions ranged from 44.4% to 45.6%, the fb₂ fractions ranged from 16.2% to 17.0%, and the fb₃ fractions ranged from 16.1% to 18.8%, respectively. T_o, T_p, T_c, and ∆H of starch ranged from 57.8 to 59.7°C, 61.9 to 64.2°C, 67.4 to 69.8°C, and 11.9 to 12.7 J/g, respectively. Peak viscosity, hot pasting viscosity, cool pasting viscosity, breakdown, and setback of starch ranged from 127 to 221 RVU, 77 to 106 RVU, 217 to 324 RVU, 44 to 116 RVU, and 137 to 218 RVU, respectively. Both G’ and G” increased in the frequency range of 0.628 to 125.6 rad/s; the wheat starch gels were more solid-like during the whole range of frequency sweep.

Horisenbada, prepared by the soaking, steaming, and baking of millets, is a traditional Mongolian food and is characterized by its long shelf life, convenience, and nutrition. In this study, the effect of processing on the starch structure, textural, and digestive property of millets was investigated. Compared to the soaking treatment, steaming and baking significantly reduced the molecular size and crystallinity of the millet starch, while baking increased the proportion of long amylose chains, partially destroyed starch granules, and formed a closely packed granular structure. Soaking and steaming significantly reduced the hardness of the millets, while the hardness of baked millets is comparable to that of raw millet grains. By fitting digestive curves with a first-order model and logarithm of the slope (LOS) plot, it showed that the baking treatment significantly reduced the digestibility of millets, the steaming treatment increased the digestibility of millets, while the soaked millets displayed a similar digestive property with raw millets, in terms of both digestion rate and digestion degree. This study could improve the understanding of the effects of processing on the palatability and health benefits of Horisenbada.

Amylose largely determines rice grain quality profiles. The process of rice amylose biosynthesis is mainly driven by the waxy (Wx) gene, which also affects the diversity of amylose content. The present study assessed the grain quality profiles, starch fine structure, and crystallinity characteristics of the near-isogenic lines Q11(Wx^lv), NIL(Wx^a), and NIL(Wx^b) in the indica rice Q11 background containing different Wx alleles. Q11(Wx^lv) rice contained a relatively higher amylose level but very soft gel consistency and low starch viscosity, compared with rice lines carrying Wx^a and Wx^b. In addition, starch fine structure analysis revealed a remarkable decrease in the relative area ratio of the short amylopectin fraction but an increased amylose fraction in Q11(Wx^lv) rice. Chain length distribution analysis showed that Q11(Wx^lv) rice contained less amylopectin short chains but more intermediate chains, which decreased the crystallinity and lamellar peak intensity, compared with those of NIL(Wx^a) and NIL(Wx^b) rice. Additionally, the starches in developing grains showed different accumulation profiles among the three rice lines. Moreover, significant differences in starch gelatinization and retrogradation characteristics were observed between near-isogenic lines, which were caused by variation in starch fine structure. These findings revealed the effects of Wx^lv on rice grain quality and the fine structure of starch in indica rice.

Cereal grain weight is an important agronomic character, influencing crop yield and quality. The high-amylose cereals usually have grains with different weights. However, it is unclear whether starches from kernels with different weights have different structural properties. In the research, the amylose content, amylopectin structure, crystallinity, and thermal properties of single-kernel starch were investigated in two high-amylose maize inbred lines, and the relationship between amylose/amylopectin content and kernel weight and the differences of starches from kernels with different weights were analyzed. The results showed that kernel weight had significantly positive relationship with amylose content and amylopectin B3+ chains (DP > 36) and average branch-chain length and negative relationship with amylopectin A chains (DP6-12) and B1 chains (DP13-24). The amylopectin A and B1 chains, relative crystallinity, and ordered degree had positive relationship with each other. The amylose content, amylopectin B3+ chains and average branch-chain length, and gelatinization temperature range were positively correlated with each other. Starches from kernels with different weights had different amylose contents, amylopectin structures, and thermal properties. The above results would offer references for breeding of high-amylose cereal crops and applications of grains with different weights.

Enzymatic modification is an effective method to inhibit starch retrogradation. However, lack of quantification of relationships between enzymatic modification and starch retrogradation makes the enzymatic improvement unpredictable. In this study, maltogenic α-amylase (MA) was used to treat wheat starch granules to restrain retrogradation, aiming to elucidate the mechanism of MA hydrolysis on wheat starch granules and to establish a quantitative relationship between the degree of hydrolysis (DH) and retrogradation. Scanning electron microscopy and small angle X-ray scattering results showed that MA hydrolyzed starch granules by a “surface pitting” mode simultaneously acting on crystalline and amorphous regions. Debranching and high performance anion exchange chromatography analysis of MA-treated wheat starch granules demonstrated that the amount of short branches with degree of polymerization＜9 increased and the proportion of medium and long branches decreased. Importantly, the extent of impaired short- and long-term retrogradation of MA-treated starch was clearly linearly correlated with the DH. This finding provides a quantitative method for predicting the degree of retrogradation improvement by enzymatic modification.

The use of unmodified starch in frozen foods can cause extremely undesirable textural changes after the freeze-thaw process. In this study, using cyclodextrin glucanotransferase (CGTase) and branching enzymes, an amylopectin cluster with high freeze-thaw stability was produced, and was named CBAC. It was found to have a water solubility seven times higher, and a molecular weight 77 times lower, than corn starch. According to the results of a differential scanning calorimetry (DSC) analysis, dough containing 5% CBAC lost 19% less water than a control dough after three freeze-thaw cycles. During storage for 7 days at 4°C, bread produced using CBAC-treated dough exhibited a 14% smaller retrogradation peak and 37% less hardness than a control dough, suggesting that CBAC could be a potential candidate for clean label starch, providing high-level food stability under repeated freeze-thaw conditions.

Starch molecules are first degraded to slowly digestible α-limit dextrins (α-LDx) and rapidly hydrolyzable linear malto-oligosaccharides (LMOs) by salivary and pancreatic α-amylases. In this study, we designed a slowly digestible highly branched α-LDx with maximized α-1,6 linkages using 4,6-α-glucanotransferase (4,6-αGT), which creates a short length of α-1,4 side chains with increasing branching points. The results showed that a short length of external chains mainly composed of 1–8 glucosyl units was newly synthesized in different amylose contents of corn starches, and the α-1,6 linkage ratio of branched α-LDx after the chromatographical purification was significantly increased from 4.6% to 22.1%. Both in vitro and in vivo studies confirmed that enzymatically modified α-LDx had improved slowly digestible properties and extended glycemic responses. Therefore, 4,6-αGT treatment enhanced the slowly digestible properties of highly branched α-LDx and promises usefulness as a functional ingredient to attenuate postprandial glucose homeostasis.

To expand the utility of barley malts and decrease the cost of enzyme-modified starch production, the structural and physicochemical characteristics of corn starch modified with fresh barley malts at different hydrolysis time were investigated. The results indicated that compared to native starch, A chain (DP 6-12) of the enzyme-treated starches increased at hydrolysis time (≤12 h), but it decreased at hydrolysis time (>12 h). Inversely, B chains (DP > 13) decreased at hydrolysis time (≤12 h) and they generally increased at hydrolysis time (>12 h). The relative crystallinity decreased from 25.63% to 21.38% and 1047 cm⁻¹/1022 cm⁻¹ reduced from 1.042 to 0.942 after endogenous malt amylases at hydrolysis time from 0 to 72 h, and the thermal degradation temperatures decreased from 323.19 to 295.94°C, whereas the gelatinization temperatures slightly increased. The gel strength decreased at hydrolysis time less than 12 h, but it increased at hydrolysis time more than 12 h. The outcomings would provide a theoretical and applicative basis about how endogenous malt amylases with lower price modify starches to obtain desirable starch derivatives and industrial production.

A method for efficient functional modification of starch granules by thermal ethanol pre-treatment and subsequent maltogenic α-amylase (MA) and branching enzyme (BE) post-treatments is described. Ethanol pre-treatment significantly increased the swelling power of starch granules thereby increasing the MA and BE susceptibility. Ethanol pre-treated granules became shrunk and twisted after incubating in buffer. Sequential MA post-treatments remarkably increased the α-1,6 to α-1,4 ratio and the content of amylopectin short chains (DP 1-10), contributing to the low retrogradation rate. BE post-treatments significantly decreased the product yield, increased the relative crystallinity of starch granules, suggesting BE had intramolecular transglucosylation activity which altered the branch position and reduced the molecular size by forming cyclic structures. Moreover, BE post-treatments showed an α-1,6 to α-1,4 transglucosylation activity by decreasing the α-1,6 to α-1,4 ratio, especially during simultaneous MA and BE catalysis. However, in the simultaneous MA and BE post-catalysis, MA dosage was predominant by noticeably hydrolyzing amylopectin and amylose molecules and increasing the α-1,6 to α-1,4 ratio, thereby leading to the lowest digestibility and retrogradation.

Branch-chain elongated starches can be synthesized by amylosucrase (AS). In this study, potato starches with different branch-chain length were produced using the temperature-dependent elongation property of AS from Deinococcus geothermalis (DGAS). Decreasing the reaction temperature led to a significant rise in the length of the branch-chains, in addition to amylose content. As branch-chain length increased, B-type crystal structure increased significantly alongside it, and the thermal transitions were enhanced, suggesting that the crystalline structure was further stabilized. In addition, a decrease in solubility and swelling power was observed, whereas the gelatinization temperatures and peak viscosities increased accordingly. With respect to digestive properties, a remarkable rise in slowly digestible starch (0-19.8%) and resistant starch (38.2%-62.2%) contents was observed, along with an enhanced resistance to mammalian mucosal α-glucosidase. In conclusion, enzymatic modification by DGAS might be an innovative method to regulate the physicochemical and digestive properties of starches.

This study aimed to compare the effects of extrusion and recrystallization treatments on the structural and physicochemical properties and digestibility of corn (CS) and potato starch (PS). CS and PS were conditioned at 40 % and 60 % moisture content and extruded at 40°C-120°C. The extrudates were stored for 1, 7, and 14 days at 4°C for recrystallization. The structural properties of extruded CS (ECS) and extruded PS (EPS), as well as the crystallization and thermal properties, water solubility, water absorption, and in vitro digestibility of recrystallized ECS (RECS) and recrystallized EPS (REPS), were evaluated. Compared with native starch, both ECS and EPS exhibited a significant decrease in their measured molecular weight. The chain length distribution did not change significantly, but the amylose content increased remarkably. Both RECS and REPS with 60 % moisture content presented a typical B-type pattern, and RECS exhibited V-type characteristic peaks. The melting signals of recrystallized amylopectin (46-64°C) and amylose (136-158°C) of RECS were detected. In vitro digestion experiments showed that RECS had lower digestibility than REPS. The highest slowly digestible starch and resistant starch contents of RECS were approximately 3.5 and 6.5 times that of unextruded CS, respectively.

Dynamic changes of rice starch granules selected for different amylose contents were analyzed in excess water while heated in-situ in a small-angle X-ray scattering (SAXS) instrument. Normal rice starch (NS) and rice starch with high amylopectin (HAP) and high amylose (HAM) were used as models. A 1D linear correlation function and a combination power-law and Gaussian function were used to extract the starch lamellar structure parameters and the fractal dimension, ordering and distribution of starch lamellae from SAXS data. For the resulting starch paste/gels, a model of two-correlation length was fitted to afford the correlation length (ξ) for the paste/gel system. The results showed that HAM exhibited higher long period (LP) and thickness of the crystalline layers (d_c) values than HAP and NS. However, HAP showed the highest ordering lamellar structure. HAP granules were more thermostable than the amylose containing starches. For the gelatinized starches, HAM showed the highest correlation length values but these notably decreased with increasing temperature indicating strong chain segment interaction. This research reveals essential structural changes in lamellae of rice starch granules and rice starch gel structure, which provides potentially useful in the working of starch-based foods and materials.