Mechanistic insights into nitrogen-induced changes in pasting characteristics of rice during storage based on proteomics analysis.

Nitrogen application delays rice quality deterioration due to changes in its pasting characteristics; however, the underlying mechanisms remain unclear. Using a label-free quantitative proteomics approach, we identified differentially expressed proteins (DEPs) during storage in paddy rice treated with different nitrogen levels. On combining the changes in physiological indicators, high-nitrogen treatment was found to downregulate ß-1,3-glucanase, reduce the decomposition of cell wall components, downregulate three proteins involved in starch metabolism, decrease the range of the amylose content and increase the range of the amylopectin, upregulate three proteins related to the lysosomal pathway, and enhance glutelin degradation. In addition, it upregulated three proteins related to flavonoid synthesis, which enhanced the stress response ability of rice, thereby contributing to the stability of biological macromolecules. The discovery of these key DEPs provides potential targets for further control over the deterioration of crop seed storage quality.

Effect of annealing and heat-moisture pretreatments on the oil absorption of normal maize starch during frying.

The impacts of two hydrothermal pretreatments, annealing (ANN) and heat moisture treatment (HMT), on oil-absorption by normal maize starch (NMS) during frying were investigated using low-field nuclear magnetic resonance (LF-NMR). The structural organizations of the fried samples were also evaluated using SEM, XRD, ATR-FTIR, and DSC, respectively. Both hydrothermal pretreatments significantly reduced the total oil content in the starch after frying, with the magnitude of the effect depending on the treatment conditions used. SEM showed that the pretreated fried starch granules preserved more of their original morphology. XRD, FTIR, and DSC showed that both pretreatments preserved more of the short-range double helices and long-range organizations within the orthorhombic crystalline structure for NMS during frying. The promoting effect of ANN/HMT on the interactions of starch molecules and the rearrangement of double helices were hypothesized to be responsible for the increased thermal stability of starch granules in the present work. As a result, fried starch pretreated by ANN/HMT were more organized and more compact than fried NMS, thus inhibiting oil absorption during frying.

Developments on carboxymethyl starch-based smart systems as promising drug carriers: A review.

Conventional drug administrations are associated with low bioavailability, high cost, more side effects, uncontrolled release profile, and patient noncompliance. Therefore, the development of an alternative to traditional drug delivery systems (DDSs) is of crucial significance. Up to now, various materials have been investigated for these purposes, among them, carboxymethyl starch (CMS) owing to its specific advantages has been studied for extensively drug delivery, particularly for oral administration. This review for the first time provides an outline of the CMS application in all areas of drug delivery. Thus, the major focus of this review is the detailed highlighting of the recent advances in CMS based DDSs to offer comprehensive information for overcoming traditional DDSs. The perspectives and the challenges of the CMS-based DDSs are briefly commented as well as. Hopefully, the current review will help to promotion of new innovative types of CMS-based systems for drug delivery applications in the near future.

Quantitative phosphoproteomics analysis reveals that protein modification and sugar metabolism contribute to sprouting in potato after BR treatment.

Brassinosteroids (BRs), a new class of steroid hormones, are involved in the regulation of plant cell elongation and seed germination. Nevertheless, the molecular mechanism of the effect of BRs on tuber sprouting remains largely unknown. In this study, quantitative phosphoproteomics was employed to investigate the protein phosphorylation changes in sprouting induced by BRs. Our results showed that BRs accelerated the conversion of starch into soluble sugar in tubers. A functional enrichment cluster analysis suggested that the "amino acid metabolism pathway" was upregulated and that "plant hormone signal transduction and protein export" were downregulated. BR treatment also changed the phosphorylation of proteins involved in the BR, ABA, starch and sugar signal transduction pathways, such as serine/threonine-protein kinase (BSK), 14-3-3, alpha-glucan water dikinase (GWD), sucrose-phosphate synthase (SPS), sucrose synthase (SS) and alkaline/neutral invertase (A/N-INV). These results shed more light on the pattern of protein phosphorylation in BR promoting potato sprouting.

Effect of dietary fibers on the structure and digestibility of fried potato starch: A comparison of pullulan and pectin.

The granular morphology, long-range and short-range ordered structures of fried potato starch were measured in the absence and presence of the dietary fibers. The in vitro digestibility of the fried starchy samples was also quantified using the Englyst method with logarithm-of-slope (LOS) analysis. After frying, the starch granules disintegrated, their internal crystalline structure disappeared, and the quantity of double helices present decreased. As a result of these changes, the fried starch was digested rapidly. Addition of pullulan or pectin to the samples prior to frying, reduced the structural changes observed in the starch granules during frying. Consequently, the fractions of slowly digestible and resistant starch (SDS and RS) increased significantly in the presence of the dietary fibers. These effects were attributed to the ability of the dietary fibers to sequester some of the water, thereby reducing starch granule structural changes, as well as due to their ability to coat the starch granules and interfere with the starch digestion process.

Roles of dextran, weak acidification and their combination in the quality of wheat bread.

Dextran-containing sourdoughs have been widely employed in baking, obtaining products with higher quality instead of adding additives. This study investigated effects of dextran of a high weight-average molecular weight (Mw) and linear structure, sourdough and their combination on wheat bread quality. The underlying mechanism was explored from properties of pasting, amylopectin retrogradation and water distributions of starch systems. Bread characteristic analyses showed that both dextran and weak acidification due to addition of sourdough improved bread quality, especially crumb softness. Dextran decreased moisture migration due to high water-binding capacity. Enhancements of amylose aggregation by weak acidification contributed to retardation of amylopectin recrystallization. A synergy existed between dextran and weak acidification. Dough rheology demonstrated that weak acidification was fundamental for dextran-induced positive dough viscoelasticity. This study indicates a combined anti-firming performance of high Mw dextran and weak acidification, possibly being a promising strategy to prolong shelf life of wheat bread.

Impact of amylose content on structural changes and oil absorption of fried maize starches.

The absorption of oil during frying has important implications for food quality, cost, and nutrition. Maize starches with low (WMS), intermediate (NMS), and high amylose (HAMS) contents were therefore heated in oil to mimic the frying process, and the impact of amylose content on the hierarchical structures and oil absorption of the fried starches was evaluated. Amylose affected the oil absorption by interfering with the structural evolution of the starch or by directly interacting with the lipids during frying. At low moisture level (20%), the granular state was preserved after frying and so the size and porosity of the granules played a dominant role in the oil absorption process, explaining why the highest oil absorption occurred in WMS. At 40% moisture content, NMS absorbed the most oil because of its granular morphology and lower crystallinity. At 60% moisture content, HAMS absorbed more oil than NMS, because more amylose molecules in HAMS provided more hydrophobic helical cavities available for lipids.

A simple and green method for preparation of non-crystalline granular starch through controlled gelatinization.

Non-crystalline granular starch (NCGS) is of considerable interest because of its unique functional properties. In this study, controlled gelatinization combined with sedimentation was used to prepare the NCGS from normal maize starch. The morphology and crystalline state of the NCGS were investigated using optical and electron microscopy, calorimetry, and X-ray diffraction (XRD). These methods showed that starch granules maintained a granule structure up to around 80 °C but they completely dissociated at higher temperatures. The number of the granules that disappeared the birefringence gradually increased with the temperature increase, and completely disappeared at 75 °C. The DSC results indicated that the crystalline structure of amylopectin was totally destroyed when the treating temperature was greater than or equal to 75 °C. The XRD patterns showed that the crystalline structure of native starch was thoroughly disappeared at 75 °C. However, B-type and V-type crystals formed in the samples heated at 80 °C or higher, corresponding to the short-term retrogradation of amylose and the formation of amylose-lipids complexes, respectively.

Effects of dextran with different molecular weights on the quality of wheat sourdough breads.

This research aimed at investigating the effects of different weight-average molecular weights (Mw: T10, T70, T250, T750, T2000) of dextran (α-(1 → 6)-linked linear backbone, α-(1 → 3)-linked branching) on wheat sourdough bread qualities. Texture analyzer showed that dextran contributed to a significant inhibition of bread staling, particularly dextran T2000. Pasting profiles (Rapid visco-analysis) and steady rheological properties (steady shear measurements) of samples indicated that dextran T2000 suppressed the swelling and gelatinization of wheat starch granules and bound a great amount of water, thus retarding the aging process. Dextran T2000 markedly improved the elastic properties of sourdough-containing dough. Wheat sourdough breads containing dextran T10 exhibited unexpected less firm crumb structure. The improvement of bread qualities was a function of the Mw of dextran. Dextran with high Mw values has the potential for improving the quality of wheat sourdough breads, especially extending shelf life.

Measurement and characterization of external oil in the fried waxy maize starch granules using ATR-FTIR and XRD.

Concerns regarding increased dietary oil uptake have prompted efforts to investigate the oil absorption and distribution in fried starchy foods. In the present study, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, together with a chloroform-methanol method, was used to analyze the external and internal oil contents in fried starchy samples. The micromorphology of fried starchy samples was further investigated using scanning electron microscope (SEM), polarized light microscope (PLM) and confocal laser scanning microscopy (CLSM). The results indicated that large amounts of oil were absorbed in or within waxy maize starch, but the majority of oil was located near the surface layer of the starch granules. After defatting, the internal oil was thoroughly removed, while a small amount of external oil remained. As evidenced by the changes of the crystalline characteristics with the help of X-ray diffraction (XRD), the interaction between starch and lipids on the surface was confirmed to form V-type complex compounds during frying at high moisture.

Understanding the fine structure of intermediate materials of maize starches.

Here we concern the molecular fine structure of intermediate material (IM) fraction in regular maize starch (RMS) and Starpro 40 maize starch (S40). IM had a branching degree and a molar mass (Mw) somewhere between amylopectin (AP) and amylose (AM). Compared with AP, IM had more extra-long (Fr I) and long (Fr II) chains and fb3-chains (degree of polymerization (DP)>36), with a higher average chain length (CL). Also, IM contained less A-chains but more B-chains (both BS-chains with DP 3-25 and BL-chains with DP≥26), accompanied by longer B- and BL-chains, total internal chains (TICL) and average internal chains (ICL), and a similar average external chain length (ECL). Furthermore, relative to RMS-IM, the IM of S40 (with higher apparent amylose content than RMS) showed increases in relatively-long chains, e.g., Fr II, fb3-chains and BL-chains, but reductions in Mw, relatively-short chains (those with DP 6-12, etc.).

Rapid, accurate, and simultaneous measurement of water and oil contents in the fried starchy system using low-field NMR.

Fried starchy food is rich in oil that may pose a risk to health. For controlling of the oil uptake, a rapid and accurate method for the determination of oil content in the fried starchy food is important. In this study, low-field nuclear magnetic resonance (LF-NMR) was applied to simultaneously determine water and oil contents in the model fried starchy system. The proton signals from oil and water were verified and distinguished by desiccation at 105°C. There was no superposition between oil and water signals in the fried starch, making it possible for quantitative analysis of water and oil in a single test. Compared with Soxhlet extraction, the LF-NMR analysis provided a more accurate result of oil content in the fried starchy system, confirming the practicability of the application of LF-NMR technology as a fast and accurate method for the quantification of water and oil in the fried starchy system.

Effect of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage.

The effects of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage were investigated by low field-nuclear magnetic resonance (LF-NMR), scanning electron microscope (SEM), and texture profile analysis (TPA). The addition of pullulan reduced the transversal relaxation time of rice starch gels during cold storage. The microstructure of rice starch gel with 0.5% pullulan was denser and more uniform compared with that of rice starch without pullulan in each period of storage time. With regard to textural properties, 0.01% pullulan addition did not significantly change the texture of rice starch gels, while 0.5% pullulan addition appeared to reduce the hardness and retain the springiness of rice starch gels (P⩽0.05). The restriction effects of pullulan on water mobility and starch retrogradation were hypothesized to be mainly responsible for the water retention, gel structure maintenance, and modification of the textural attributes of rice starch gels.

Crystallite orientation maps in starch granules from polarized Raman spectroscopy (PRS) data.

In this work, polarized Raman spectroscopy (PRS) was used to determine orientation maps of crystallites present in Phajus grandifolius starch granules based on the anisotropic response of the glycosidic Raman band at 865cm(-1). The response of this band was preliminarily evaluated using model A-amylose crystals as standard. The A-amylose crystals oriented "in plane" showed a maximal intensity ratio of ∼3.0 for bands 865/1343cm(-1) when the polarization of the laser was along the chain axis of the crystal, i.e., parallel to the axis of the amylose double helices, and a minimal intensity ratio of ∼0.25 when perpendicular. The orientation maps of Phajus grandifolius starch granules showed two distinct regions: one isotropic and the other with a highly anisotropic response. The origin of the difference might be changes in both organization/concentration and orientation of the crystallites across the starch granules.

Understanding shape and morphology of unusual tubular starch nanocrystals.

Starch nanocrystals (SNC) are aptly described as the insoluble degradation byproducts of starch granules that purportedly display morphologies that are platelet-like, round, square, and oval-like. In this work, we reported the preparation of SNC with unprecedented tubular structures through sulfuric acid hydrolysis of normal maize starch, subsequent exposure to ammonia and relaxation at 4°C. High-resolution transmission electron microscopy observation clearly proved that the SNCs possess tubular nanostructures with polygonal cross-section. After further reviewing the transformations of SNC by acid hydrolysis, ammonia treatment, and curing time at 4°C, a mechanism for T-SNC formation is suggested. It is conjectured that T-SNC gradually self-assembles by combination of smaller platelet-like/square nanocrystals likely loosely aggregated by starch molecular chains from residual amorphous regions. This work paves the way for the pursuit of new approaches for the preparation of starch-based nanomaterials possessing unique morphologies.

Effect of pullulan on the short-term and long-term retrogradation of rice starch.

The effect of pullulan (PUL) on the retrogradation of rice starch (RS) was investigated by means of rapid visco-analyzer (RVA), rotational rheometer, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). RVA results showed that addition of pullulan significantly decreased the breakdown and setback values, which meant that the short-term retrogradation of RS was inhibited. The dynamic time sweep of samples also proved the retarding effect of pullulan on the retrogradation of RS. DSC curves showed clearly that pullulan significantly reduced the retrogradation enthalpy of amylopectin, and the kinetics of retrogradation was analyzed using the Avrami model. XRD results showed that recrystallinity of RS was reduced from 11.565% to 8.841% with the addition of pullulan and this was in line with the DSC results. It could be concluded that the addition of pullulan apparently influenced not only the short-term retrogradation of amylose, but also the long-term retrogradation of amylopectin.