Estimation of the distribution of molecular weight for amylose by the low-angle laser-light-scattering technique combined with high-performance gel chromatography

A comprehensive review on starch: Structure, modification, and applications in slow/controlled-release fertilizers in agriculture

This comprehensive review thoroughly examines starch's structure, modifications, and applications in slow/controlled-release fertilizers (SRFs) for agricultural purposes. The review begins by exploring starch's unique structure and properties, providing insights into its molecular arrangement and physicochemical characteristics. Various methods of modifying starch, including physical, chemical, and enzymatic techniques, are discussed, highlighting their ability to impart desirable properties such as controlled release and improved stability. The review then focuses on the applications of starch in the development of SRFs. It emphasizes the role of starch-based hydrogels as effective nutrient carriers, enabling their sustained release to plants over extended periods. Additionally, incorporating starch-based hydrogel nano-composites are explored, highlighting their potential in optimizing nutrient release profiles and promoting plant growth. Furthermore, the review highlights the benefits of starch-based fertilizers in enhancing plant growth and crop yield while minimizing nutrient losses. It presents case studies and field trials demonstrating starch-based formulations' efficacy in promoting sustainable agricultural practices. Overall, this review consolidates current knowledge on starch, its modifications, and its applications in SRFs, providing valuable insights into the potential of starch-based formulations to improve nutrient management, boost crop productivity, and support sustainable agriculture.

Transformations and functional role of starch during potato crisp making: A review

Potato chips are a major product in the savory snack market and are consumed worldwide because of their enjoyable and distinctive organoleptic properties. They are conventionally produced by deep-frying thin slices of fresh potato. In contrast, potato crisps are manufactured from dried potato derivatives such as potato flakes (PFs). Their production is reviewed in this manuscript and requires the formation of dough based on hydrated PFs. Expansion of the dough during deep-frying provides the crisps with their desired crunchy texture. As part of an overall trend, the consumer search for calorie-reduced food products has also stimulated research to lower oil uptake during crisp production. However, minimizing oil absorption without losing the characteristic palatability of deep-fried products is challenging and requires fundamental knowledge on factors determining product texture and oil absorption. The transformations and functional role of starch, potato's main constituent, during crisp making are key in this respect and are reviewed here.

CO2-Responsive CCT Protein Stimulates the Ectopic Expression of Particular Starch Biosynthesis-Related Enzymes, Which Markedly Change the Structure of Starch in the Leaf Sheaths of Rice

CO2-responsive CCT protein (CRCT) is suggested to be a positive regulator of starch biosynthesis in the leaf sheaths of rice, regulating the expression levels of starch biosynthesis-related genes. In this study, the effects of CRCT expression levels on the expression of starch biosynthesis-related enzymes and the quality of starch were studied. Using native-PAGE/activity staining and immunoblotting, we found that the protein levels of starch synthase I, branching enzyme I, branching enzyme IIa, isoamylase 1 and phosphorylase 1 were largely correlated with the CRCT expression levels in the leaf sheaths of CRCT transgenic lines. In contrast, the CRCT expression levels largely did not affect the expression levels and/or activities of starch biosynthesis-related enzymes in the leaf blades and endosperm tissues. The analysis of the chain-length distribution of starch in the leaf sheaths showed that short chains with a degree of polymerization from 5 to 14 were increased in the overexpression lines but decreased in the knockdown lines. The amylose content of starch in the leaf sheath was greatly increased in the overexpression lines. In contrast, the molecular weight of the amylopectin of starch in the leaf sheath of overexpression lines did not change compared with those of the non-transgenic rice. These results suggest that CRCT can control the quality and the quantity of starch in the leaf sheath by regulating the expression of particular starch biosynthesis-related enzymes.

Assessment of the influence of amylose-LPC complexation on the extent of wheat starch digestibility by size-exclusion chromatography

Amylose forms inclusion complexes with lysophosphatidylcholine (LPC), that decrease the susceptibility of amylose to amylase degradation. This study on the influence of complexation on starch susceptibility to amylase explains the nature of this protective effect. Wheat starch suspensions (9% w/w) containing 0.5-5% LPC were subjected to hydrolysis by porcine pancreatic α-amylase at 37 °C for several digestion times. The digesta were analysed by size-exclusion chromatography (SEC). The molar mass distribution was closely dependent on the digestion time and amount of LPC. This study precisely demonstrates the alteration of the digestion profile of starch on a molecular level, influenced by amylose-LPC complexation; however the effect depends on the digestion time. During 15 and 30 min digestion, inclusion complexes not only protect amylopectin in the initial hydrolysis stage, but also demonstrate lower susceptibility of the molecular amylose complexes to amylase hydrolysis. Digestion for 240 min resulted in a lower oligosaccharide peak concentration, in the presence of a high LPC concentration, which is related to less degradation of complexed amylose fraction.

Peculiarities of enhancing resistant starch in ruminants using chemical methods: opportunities and challenges

High-producing ruminants are fed high amounts of cereal grains, at the expense of dietary fiber, to meet their high energy demands. Grains consist mainly of starch, which is easily degraded in the rumen by microbial glycosidases, providing energy for rapid growth of rumen microbes and short-chain fatty acids (SCFA) as the main energy source for the host. Yet, low dietary fiber contents and the rapid accumulation of SCFA lead to rumen disorders in cattle. The chemical processing of grains has become increasingly important to confer their starch resistances against rumen microbial glycosidases, hence generating ruminally resistant starch (RRS). In ruminants, unlike monogastric species, the strategy of enhancing resistant starch is useful, not only in lowering the amount of carbohydrate substrates available for digestion in the upper gut sections, but also in enhancing the net hepatic glucose supply, which can be utilized by the host more efficiently than the hepatic gluconeogenesis of SCFA. The use of chemical methods to enhance the RRS of grains and the feeding of RRS face challenges in the practice; therefore, the present article attempts to summarize the most important achievements in the chemical processing methods used to generate RRS, and review advantages and challenges of feeding RRS to ruminants.

Crop-derived polysaccharides as binders for high-capacity silicon/graphite-based electrodes in lithium-ion batteries

Rice to power: Amylopectin is a major component of agricultural products such as corn, potato, and rice. Silicon-graphite electrodes are prepared by using slurries of these polysaccharides as binders. Compared to the conventionally used binder PVdF, they exhibit drastically improved electrode performance in Li cells. The improved performance is coupled to the degree of branching.

Interference prevention in size-exclusion chromatographic analysis of debranched starch glucans by aqueous system

Branch chain-length distribution of amylopectin plays an important role on the characteristics of starch. One of the adapted protocols for determining the chain-length distribution and mass proportion of starch molecules is that starch is debranched with isoamylase and then analyzed by using high-performance size-exclusion chromatography coupled with multiangle laser-light scattering and refractive index detection (HPSEC-MALS-RI). However, ammonium sulfate in commercial isoamylase and acetate in debranching buffer give significant interferences on the chromatograms because of their undesirable ionic interactions with column sorbent materials. This study deals with development for correcting those interferences. A weak anion-exchange resin or selective precipitation with barium acetate was employed to remove sulfate prior to HPSEC determination. The interference of acetate was overcome by means of high ionic strength eluent, 0.3 M sodium nitrate. The specific refractive index increment (dn/dc) of amylodextrin was determined to be 0.147 using the modified conditions and was applied to calculate the molecular weight distribution of debranched starch molecules.

Toward a full characterization of native starch: separation and detection by size-exclusion chromatography

The structure of starch molecules is relevant to nutrition and industrial applications. Size-exclusion chromatography (SEC, also known as GPC) of native starch generally suffers non-satisfactory repeatability and reproducibility of the dissolution and separation. This work combines two polar organic solvents: dimethylsulfoxide for complete dissolution and dimethylacetamide to limit shear degradation. The separation is as repeatable as that of polystyrene standards performing dissolution and separation at 80 degrees C. Successful covalent-labeling on the glucose unit is claimed to be published here for the first time in non-degradative conditions and allows the use of UV detector with significantly higher sensitivity than with a refractometer.

A new NMR method for directly monitoring and quantifying the dissolution kinetics of starch in DMSO

The kinetics of dissolution of starch is needed for (i) understanding digestive processes; (ii) providing data that could correlate with higher levels of starch structure; (iii) improving techniques for starch characterization in solution. A novel method is presented here to directly monitor these dissolution kinetics by time-resolved (1)H solution-state nuclear magnetic resonance (NMR); studies were carried out in deuterated dimethyl sulfoxide (DMSO-d(6)). By assuming pseudo-first-order kinetics with respect to starch concentration, the data for various starch samples yield values of the apparent rate coefficients for the rate of appearance of completely dissolved anhydroglucose units, results which have not been obtained hitherto. The presence of a limited amount of water in DMSO had a drastic effect on dissolution kinetics (slowing it down at high temperatures), indicating multiple pathways for the dissolution mechanism. Dynamic light scattering (DLS) appears to be more limited than the NMR method to monitor the kinetics of dissolution. The newly developed NMR method can be extended to other solvents and polysaccharides.

Enzymatic hydrolysis of flavonoids and pectic oligosaccharides from bergamot (Citrus bergamia Risso) peel

Pectinolytic and cellulolytic enzymes (Pectinase 62L, Pectinase 690L, and Cellulase CO13P) were used to evaluate the solubilization of carbohydrates and low molecular weight flavonoids from bergamot peel, a major byproduct of the essential oil industry. The enzymes were characterized for main-chain and side-chain polysaccharide hydrolyzing activities and also against pure samples of various flavonoids previously identified in bergamot peel to determine various glycosidase activities. The addition of Pectinase 62L or 690L alone, or the combination of Pectinase 62L and Cellulase CO13P, was capable of solubilizing between 70 and 80% of the bergamot peel, and up to 90% of the flavonoid glycosides present were cleaved to their aglycones. Cellulase CO13P alone solubilized 62% of the peel but had no deglycosylating effect on the flavonoid glycosides. Over a 24-h time course, a rapid release of cell wall carbohydrates was observed after treatment with Pectinase 62L, with a concurrent gradual hydrolysis of the flavonoid glycosides. Size-exclusion chromatography of the solubilized extract showed that after 24-h incubation, the majority of the solubilized carbohydrates were present as monosaccharides with a smaller proportion of oligosaccharides.

In vitro evaluation of the prebiotic activity of a pectic oligosaccharide-rich extract enzymatically derived from bergamot peel

The prebiotic effect of a pectic oligosaccharide-rich extract enzymatically derived from bergamot peel was studied using pure and mixed cultures of human faecal bacteria. This was compared to the prebiotic effect of fructo-oligosaccharides (FOS). Individual species of bifidobacteria and lactobacilli responded positively to the addition of the bergamot extract, which contained oligosaccharides in the range of three to seven. Fermentation studies were also carried out in controlled pH batch mixed human faecal cultures and changes in gut bacterial groups were monitored over 24 h by fluorescent in situ hybridisation, a culture-independent microbial assessment. Addition of the bergamot oligosaccharides (BOS) resulted in a high increase in the number of bifidobacteria and lactobacilli, whereas the clostridial population decreased. A prebiotic index (PI) was calculated for both FOS and BOS after 10 and 24 h incubation. Generally, higher PI scores were obtained after 10 h incubation, with BOS showing a greater value (6.90) than FOS (6.12).

Improved Methods for the Structural Analysis of the Amylose-Rich Fraction from Rice Flour

Cooking and sensory properties of rice are largely determined by the amylose content and structure. For relationships between functional and structural properties, a more accurate method to determine the structure of amylose is required. Here we calibrate size exclusion chromatography (SEC) columns, using Mark-Houwink parameters for linear starch and pullulan standards, to obtain the true molecular weight distribution of linear starch. When the molecular weight distribution is reported relative to pullulan, rather than the actual molecular weight which is readily obtained from universal calibration, it is seen that the molecular weights of longer amylose chains are greatly underestimated. We validate the SEC method to enable the measurement of the hydrodynamic volume distribution of the starch by examining reproducibility and recovery. Analysis of the starch in the sample pre- and post-SEC shows that 20% of the carbohydrate is not recovered. Comparison of the weight-average degree of polymerization, X(w), of (undebranched) starch of pre- and post-SEC is made using iodine binding as well as Berry plots of data from multi-angle laser light scattering (MALLS). These both show that current SEC techniques for starch analysis lead to significant loss of high molecular weight material. Indeed, for the systems studied here, the values for X(w) after SEC are about three times lower than those before SEC. Iodine-starch complexes of pre- and post-SEC samples reveals that the SEC techniques give reliable data for the amylose fraction but not for amylopectin. We address reports in the literature suggesting that the conventional isoamylase method for debranching starch would lead to incomplete debranching and thus incorrect molecular weight distributions. However, it is shown using (1)H NMR that isoamylase can completely debranch the amylose (to within the detection limit of 0.5%), and by SEC that successive incubation with isoamylase, alpha-amylase, and beta-amylase can degrade the amylose-rich fraction completely to maltose. We develop a method to obtain a hot water soluble fraction (HWSF), rich in undamaged amylose molecules, directly from rice flour, avoiding the structural degradation of previous techniques. With appropriate sample handling, the formation of associations between starch chains is minimized. With the combination of calibrated and validated SEC methods, and an improved extraction of amylose from rice, the X(w) for both HWSF and debranched HWSF are found to be much larger than has previously been reported.

Influence of amylopectin structure and amylose content on the gelling properties of five cultivars of cassava starches

Five cassava genotypes were investigated to identify the fine amylopectin structures and granule chemical compositions, which differentiated the starches into high (T(o) = 63.7 degrees C on average) and low (57.3 degrees C on average) gelatinization temperatures. The amylose contents (15.9-22.4%) and granular dimensions (12.9-17.2 microm) significantly differed among the starches. Diverse amylopectin structural elements resulted in significant swelling power, viscoelastic properties, and gel firmness. Debranched starches revealed a trimodal amylopectin distribution of three fractions: FIII (DP 12), FII (DP 24.31), and FI (DP 63) and FIII (DP 12), FII (DP 24.69), and FI (DP 67) for the low and high gelatinization starch groups, respectively. The higher proportion of FI long chain entanglement with amylose chain lengths to form longer helical structures was confirmed in the high gelatinization starch group, which developed "true" gels with better shear resistance, frequency independence, and higher gel firmness. Significant amounts of resistant starch fractions revealed the potential for application of these genotype starches in diverse foods.

Improving starch for food and industrial applications

Progress in understanding starch biosynthesis, and the isolation of many of the genes involved in this process, has enabled the genetic modification of crops in a rational manner to produce novel starches with improved functionality. For example, potato starches have been created that contain unprecedented levels of amylose and phosphate. Amylose-free short-chain amylopectin starches have also been developed; these starches have excellent freeze-thaw stability without the need for chemical modification. These developments highlight the potential to create even more modified starches in the future.

Structure and physicochemical properties of starches from kidney bean seeds at immature, premature and mature stages of development

Starches from kidney bean (Phaseolus vulgaris L. cv. Toramame) seeds at the immature, premature, mature stages of development were examined. The starch content increased from 94, 219 to 265 mg per seed. Starches showed the C(a)-crystalline type composed of small (<5 micrometer) and large (10-35 micrometer) granules, with the large granules largely increasing with maturity. The amylose content increased from 21, 26 to 27%, and rapid viscograms and DSC thermograms suggested that the mature-stage starch was gelatinized with ease. The amylose increased in size from DPn 820, 1000 to 1080 and a number of chains per molecule (NC) from 3.3, 4.2 to 4.5. The branched amylose was a minor component (11-18% by mole) with NC 20-22. The amylopectin was similar in CL (23), beta-amylolysis limit (59%), and chain-length distribution, but reduced in size (DPn 17,100-5270) and increased in content of phosphorus (114-174 ppm) with an increase in the amount of phosphorus linked to C-6 of the glucose residue (8-66%).

Structural studies of starches with different water contents

The proportion of double helices in starches from a series of pea [rb, rug4-b, rug3-a, and lam-c mutants, and the wild type (WT) parental line], potato and maize (normal and low amylose), and wheat (normal) lines, ranged from about 30-50% on a dry weight basis. In relatively dry starch powders, only about half of the double helices were in crystalline order, this proportion being higher for A-type than for B-type starches. Using starch from WT pea as an example, it was found that increasing water content results in an increase in total crystallinity. When the water content was raised to a level similar to that in excess water, the proportion of crystallinity was close to the proportion of double helices (DH). Measuring crystallinity in starches with a high water content is difficult using traditional methods such as x-ray diffraction. A method was developed, therefore, for determining starch structural characteristics in excess water by measuring the enthalpy of gelatinization transition in quasi-equilibrium differential scanning calorimetry (DSC) experiments. It is suggested that DH% = DeltaH(sp)/DeltaH(DH) x 100%, where DeltaH(sp) and DeltaH(DH) represent the specific enthalpies of gelatinisation transition, DeltaH(sp) being measured as J/g dry starch weight and DeltaH(DH) as J/g DH, in starch. Studies on potato and maize starches in excess water and in 0.6M KCl showed, respectively, that DeltaH(DH) was 36.3 and 35.6 J/g for B-type polymorphs and 33.0 and 35.0 J/g for A-type polymorphs. For C-type starches, such as those from pea, intermediate values of DeltaH(DH), related to the proportions A-/B-polymorphs, should be used. The type of crystallinity in starch can be determined by the shift in peak temperature for thermograms in excess water and in excess 0.6M KCl. For B-polymorphs this shift was found to be approximately 2-3 degrees C and for A-polymorphs approximately 7-12 degrees C. The ratio between ordered areas with both A- and B-polymorphs can be determined from the enthalpies of disruption of each area. These enthalpies can be obtained by deconvolution of bimodal thermograms produced by C-type starches in excess 0.6M KCl. This methodical approach can be applied to all starches that give a sharp gelatinisation thermogram in excess water. Using a range of methods, including DSC, it was found that starch granules from the mutant peas are constructed in a similar way to those from the WT, with B-polymorphs in the centre and A-polymorphs at the periphery of all granules. The proportion of A/B-polymorphs, however, differed between the mutants. It was found that in addition to increasing the total crystallinity, increasing the water content within the granules also resulted in an increase in the proportion of B-polymorphs.

Discrete forms of amylose are synthesized by isoforms of GBSSI in pea

Amyloses with distinct molecular masses are found in the starch of pea embryos compared with the starch of pea leaves. In pea embryos, a granule-bound starch synthase protein (GBSSIa) is required for the synthesis of a significant portion of the amylose. However, this protein seems to be insignificant in the synthesis of amylose in pea leaves. cDNA clones encoding a second isoform of GBSSI, GBSSIb, have been isolated from pea leaves. Comparison of GBSSIa and GBSSIb activities shows them to have distinct properties. These differences have been confirmed by the expression of GBSSIa and GBSSIb in the amylose-free mutant of potato. GBSSIa and GBSSIb make distinct forms of amylose that differ in their molecular mass. These differences in product specificity, coupled with differences in the tissues in which GBSSIa and GBSSIb are most active, explain the distinct forms of amylose found in different tissues of pea. The shorter form of amylose formed by GBSSIa confers less susceptibility to the retrogradation of starch pastes than the amylose formed by GBSSIb. The product specificity of GBSSIa could provide beneficial attributes to starches for food and nonfood uses.

The effect of water content on the ordered/disordered structures in starches

(13)C cross-polarization magic angle spinning NMR has been used to study the ordered and disordered structures of starches with different water contents. The amorphous regions of starch have been shown to produce NMR patterns only if they are in a glassy state, the widths, positions, and areas of the peaks to some extent being dependent on the temperature and the water content of the starch. In the amorphous region, the peaks were all Gaussian in shape, while the peaks in the ordered regions had Lorentz profiles. Water contents in the range 10-50% did not influence the proportion of double helices in the starch. Decreasing the water content to 1-3%, however, resulted in a significant decrease in the proportion of double helices, the effect being greater in B- than in A-type starches. It is suggested that short-range order structures in starches (double helices) are stabilized by becoming part of long-range order structures (crystallites).

Determination of molecular weight of agars and effect of the molecular weight on the glass transition

A novel procedure to determine the molecular weight (MW) and MW distributions for various agars is described. The MW values of commercial agars, an agarose, an agaropectin, and hydrolyzed agaroses were determined by size exclusion chromatography-low angle laser light scattering, using 4.0 M guanidine hydrochloride as eluent to avoid gelation. The MW for the commercial agars was between 106 400 and 243 500 with polydispersity between 1.283 and 6. 600. The MW of the agarose separated from a commercial agar was lower than that of the agaropectin. To prepare agaroses with different MW values, the obtained agarose was hydrolyzed. The MW of the agarose decreased with hydrolysis time, and the polydispersity, on the contrary, increased. The glass transition temperature (T(g)) of agarose with different MW values and that of agaropectin were measured by differential scanning calorimetry. The T(g) of the agarose was higher than that of the agaropectin with higher MW. The T(g) of agarose increased with MW.

Examination of number-average degree of polymerization and molar-based distribution of amylose by fluorescent labeling with 2-aminopyridine

Suitable conditions for the fluorescent labeling of the reducing residue of amylose with 2-aminopyridine were examined. Amylose of up to 38.5 nmol was labeled with a constant labeling efficiency. The same efficiencies were obtained for amyloses having a number-average degree of polymerization (dpn) of 521-4400. The analysis of labeled amylose on size-exclusion HPLC with refractive index and fluorescence detection enabled the determination of dpn and dp distribution on a molar basis. The analysis of eight amylose specimens from seven botanical sources (potato, sweet potato, barley, wheat, indica rice, japonica rice, and maize) gave dpn values in good agreement with those determined by a conventional colorimetric method. The molar-based distributions of these amyloses were characteristic of botanical source and revealed the presence of several molecular species with different dp not detectable in the distribution on a weight basis. Small amyloses with a dp less than 10(3) were predominant in the cereals while amyloses with a dp over 10(3) were predominant in the tubers, suggesting a difference in the biosynthetic process determining the dp distribution of amylose between cereals and tubers.