Differences and Mechanism of Waxy Corn Starch and Normal Corn Starch in the Preparation of Recrystallized Resistant Starch (RS3).

This study prepared resistant starch (RS) from waxy corn starch and normal corn starch and analyzed the effects of its molecular and microstructural characteristics on RS content. The RS content of waxy corn resistant starch (RS-WCS) was highest at 57.8%, whereas that of normal corn resistant starch (RS-NCS) was 41.46%. The short-chain amylose contents of RS-WCS and RS-NCS were 47.08% and 37.24%, respectively, proportional to their RS content. Additionally, RS content positively correlated with crystallinity, short-range order degree, and degree of polymerization (DP), exceeding 25. Electron microscopic images, before and after enzymolysis, revealed that RS-WCS was hydrolyzed from the surface to the center by pancreatic α-amylase, while RS-NCS underwent simultaneous hydrolysis at the surface and center. These results indicate that the higher RS content in RS-WCS, compared to RS-NCS, is attributable to the synergistic effects of molecular structure and microstructure.

Feasibility of replacing waxy rice with waxy or sweet-waxy corn viewed from the structure and physicochemical properties of starches.

To explore the feasibility of substituting waxy rice with waxy or sweet-waxy corn, eight varieties of waxy and sweet-waxy corns were selected, including three self-cultivated varieties (Feng nuo 168, Feng nuo 211, and Feng nuo 10). Their starches were isolated and used as research objects, and commercially available waxy rice starch (CAWR) and waxy corn starch (CAWC) were used as controls. X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, rapid viscosity analyzer, and rotational rheometer were used to analyze their physicochemical and structural characteristics. The morphologies of all corn starch granules were generally oval or round, with significant differences in particle size distributions. All ten starches exhibited a typical A-type crystal structure; however, their relative crystallinity varied from 20.08% to 31.43%. Chain length distribution analysis showed that the A/B ratio of Jing cai tian nuo 18 and Feng nuo 168 was similar to that of CAWR. Peak viscosities of corn starches were higher than that of CAWR, except for Feng nuo 10, while their setback values were lower than that of CAWR. Except for Feng nuo 10, the paste transparency of corn starches was higher than that of CAWR (10.77%), especially for Jing cai tian nuo 18 (up to 24%). In summary, Jing cai tian nuo 18 and Feng nuo 168 are promising candidates to replace CAWR in developing various rice-based products.

Insight into the improvement in pasting and gel properties of waxy corn starch by critical melting treatments.

To improve the pasting and gel properties of waxy corn starch (WCS), the native starch was modified by critical melting (CM) at the onset temperature (TO), peak temperature (TP), and conclusion temperature (TC) (labeled CMO, CMP, and CMC respectively). CM treatments significantly enhanced the thermal stability of the WCS, as indicated by the increase in the peak gelatinization temperature, pasting temperature, and peak time. In addition, after CMP treatment, the storage modulus, hardness, gumminess, springiness, and chewiness of starch gels significantly increased by 43.29 %, 31.14 %, 23.36 %, 8.26 %, and 61.43 %, respectively, and the syneresis rate significantly decreased by 19.69 % (p < 0.05). These results indicated that CMP treatments significantly improved the gelling ability and freeze-thaw stability of the WCS. These results are ascribed to the partial disruption and enhanced rearrangement of the starch crystalline structure. CMP treatment induced the crystalline structure of starch to be partially disrupted and a hard structure was formed on the surface of starch granules. The hard structure in CMP-treated starch supplied more attachment points for crystalline structure rearrangement during gelatinization. Therefore, the above results indicated that CMP treatments can be used to modify starch to improve the pasting and gel properties of starch-based food products.

Nano-starch for food applications obtained by hydrolysis and ultrasonication methods.

In the present work, corn (CS) and waxy corn starch (WCS) with different amylose content (determined with the UV-vis spectroscopy) were subjected to acid hydrolysis, ultrasound, and a combination of both, performed at a raised temperature and short period, to obtain nanoparticles (nano-WCS and nano-CS). Scanning transmission electron microscopy (TEM-STEM) proved the effectiveness of the proposed method for nanoparticle synthesis with a size below 5 nm. FTIR spectroscopy and X-ray diffraction (XRD) delivered information on their molecular structure (i.e., reduction in nano-CS crystallinity degree (Xc) arising from higher amylose content and more stable Xc for nano-WCS). Thermogravimetric analysis (TGA) combined with FTIR analysis of gaseous products of thermal decomposition was also performed. The thermal stability decreased in varying degrees for nano-WCS and nano-CS. Less susceptibility of waxy corn starch for modification was proven.Nanoparticles are expected to be effective for functional food, and biomedical applications.

Mesona chinensis polysaccharide accelerates the short-term retrogradation of debranched waxy corn starch.

The effect of non-starch polysaccharides on the structural and functional properties of native starch have been extensively studied. However, the effect of non-starch polysaccharides on the structural characteristics of debranched starch, a kind of enzymatic modified starch, remains unclear. The aim of this study is to investigate the effects of Mesona chinensis polysaccharide (MP) on starch retrogradation and structural properties of debranched waxy corn starch (DWS). The results showed that only appropriate addition of MP (0.5 or 1%) can effectively promote the short-term retrogradation of DWS, while excessive MP (3 or 5%) had a negative effect. Gel hardness results revealed that the short-term retrogradation (24 h) of DWS could be divided into two phases. The retrogradation of DWS-MP gels mainly occurred at first stage (0-4 h), which was demonstrated by the rapid increase of gel hardness and relative crystallinity in this stage. In the second stage (4-24 h), DWS-MP gels were more likely to undergo the aggregation of starch granules as proved by SEM and particle size results. The degree of short-range ordered decreased during the total retrogradation stage. Overall, this work aims to provide an insight into the effect of non-starch polysaccharides on the short-term retrogradation of DWS.

Preparation and physiochemical properties of enzymatically modified octenyl succinate starch.

The high viscosity and low solubility of octenyl succinate starch (OSAS) in water often lead to low reaction efficiency and uneven distribution of OSA groups, which can be solved by subjecting OSA starch to enzymatic digestion. Waxy corn starch is used to produce OSAS. The molecular weight of enzymolysis modified octenyl succinate starches (E-OSAS) decreased with the addition of enzyme, and the substitution of enzymatically digested OSAS was larger than that of OSAS. As the addition of pullulanase increased, the substitution of E-OSAS tended to increase and the apparent viscosity decreased significantly. The smaller its particle size and polydispersity index (PDI), the larger the absolute value of the zeta potential. E40 -OSAS with the smallest particle size and best homogeneity and stability had the smallest weight average molecular weight (1.38 × 106  g/mol), the smallest number average molecular weight (1.37 × 105  g/mol), and the largest degree of substitution of 0.019. The E-OSAS has not been investigated deeply enough, and the enzymatic treatment by pullulanase is not much studied, so this study is of great importance to provide some basis for the research of new microcapsules. PRACTICAL APPLICATION: This work aims to provide wall materials with lower viscosity and better encapsulation properties for the food industry. Waxy corns starch is used to manufacture OSAS. This wall material is a partly biodegradable material that is hydrophilic on the outside and hydrophobic on the inside, and its preparation process is in line with the concept of green chemistry.

Development changes in multi-scale structure and functional properties of waxy corn starch at different stages of kernel growth.

Waxy corn starch is widely used in food and papermaking industries due to its unique properties. In this work, the structural and functional properties of starch isolated from waxy corn at different stages of kernel growth were investigated and their relationships were clarified. The results showed that with kernel growth, the surface of starch granules became smooth gradually, and the inner growth rings and the porous structure grew and became clear. Meanwhile, the weight-average molecular mass (Mw), root mean square radius (Rg), and average particle size increased while the amylose content decreased, which should account for the decreased pasting temperature (from 71.37 to 67.44 °C) and increased peak viscosity (1574.2 to 1883.1 cp) and breakdown value observed. Besides, the contents of slowly digestible starch (SDS) and resistant starch (RS) in waxy corn starch decreased significantly (from 44.01% to 40.88% and from 16.73% to 9.80%, respectively, p < 0.05) due to decreases in the double helix content, crystallinity, and structural order, and increases in the semi-crystalline lamellae thickness and the amorphous content. This research provides basic data for the rational utilization of waxy corn starch at different stages of kernel growth.

Molecular and physical characterization of octenyl succinic anhydride-modified starches with potential applications in pharmaceutics.

Five commercially available starches modified with octenyl succinic anhydride (OSA) are characterized at a molecular, physicochemical and bulk level providing useful data for designing pharmaceutical products. The degree of substitution (DS) of the starches range from 0.017 to 0.032 and their molecular weights (Mw) and radius of gyration (Rz) are lower than those of native starch, suggesting additional modification processes besides the chemical treatment with OSA. The ability of the starches to reduce the water surface tension keeps a direct relationship with the DS and an inverse association with the Mw. Thermal properties, crystallinity assays and morphology evidence that most modified starches characterize by amorphous aggregated structures, possibly generated by gelatinization processes, which favor the flow properties of the powders. Water sorption and surface energy behaviors seem to be related to the number of octenyl succinate (OS) moieties. After dispersion in water, shear-thinning and Newtonian behaviors also depend on the type of OS-starch.

Utilization of waxy corn starch as an efficient chain extender for the preparation of polyurethane elastomers.

Waxy corn starch modified polyurethane elastomers were synthesized by step growth polymerization reaction between NCO-terminated prepolymer and chain extenders (1,4-butanediol/starch). Isophorone diisocyanates (IPDI) was reacted with hydroxyl terminated polybutadiene (HTPB) to synthesize prepolymer that was reacted with different moles of 1,4-butanediol (1,4-BDO) and starch to produced five samples of polyurethane. These specimens were analyzed by Fourier transformed infrared (FTIR) and proton Nuclear Magnetic Resonance (1H NMR) spectroscopy to determine the structural information. However, role of starch as chain extender was examined by gel permeation chromatography (GPC). Additionally, starch increased the thermal stability of PUs as compared to the conventional chain extender (1,4-BDO). Over all, this work has been designed to develop biodegradable polyurethanes that could be used in biomedical systems.

Preparation and properties of granular cold-water-soluble porous starch.

In this work, granular cold-water soluble waxy corn starch (N-GCWS) and granular cold-water soluble porous waxy corn starch (P-GCWS) were prepared by waxy corn starch (WS) treated with alcohol-alkali. Starch morphologies, crystal structures, turbidity, cold water viscosity, freeze-thaw stability and oil absorption capacity of N-GCWS and P-GCWS starches were compared. The results showed porous waxy corn starch (PS) was easier to prepare P-GCWS starch than WS to prepare N-GCWS. SEM showed that PS and WS became dent-twisted and tended to flatten with the increase of CWS. After alcohol-alkali treatment, the X-ray diffraction pattern of PS and WS changed from A type to amorphous and pores were remained on the surface of P-GCWS starches granular. Turbidity, freeze-thaw stability, viscosity, oil absorption capacity of N-GCWS and P-GCWS starches was shown higher than that of WS and PS. The oil absorption capacity of P-GCWS was higher than that of N-GCWS.

Tailoring Digestibility of Starches by Chain Elongation Using Amylosucrase from Neisseria polysaccharea via a Zipper Reaction Mode.

Amylosucrase from Neisseria polysaccharea (NpAS) was applied to modify waxy corn starch (WCS) and irradiated WCS, whose attenuated digestibility was studied. Herein, the mobility of the reaction mixture did not affect the enzyme catalytic efficiency, and the reaction kinetics suggest that the enzyme elongated the starch chain via a zipper reaction mode. The A-type crystalline structure of native and irradiated WCS was changed to B type after NpAS treatment, and a longer chain length led to a further increase in the gelatinization temperature. Chain elongation increased the content of resistant starch (RS) from 22.3% (native WCS) to be as much as 64.4% for NpAS-modified WCS, accordingly decreasing the contents of both rapidly and slowly digestible starches. Pearson correlation analysis implies that the RS content of NpAS-modified starches was positively and negatively correlated to the proportion of intermediate chains [13 ≤ degree of polymerization (DP) ≤ 24] and short chains (DP ≤ 12), respectively.

Green preparation and characterization of starch nanoparticles using a vacuum cold plasma process combined with ultrasonication treatment.

In this study, starch nanoparticles (SNPs) were fabricated via a facile and green method involving a vacuum low-temperature plasma process combined with rapid ultrasonication treatment using waxy corn starch (WCS) and potato starch (PS). Morphology, size, crystalline structure, thermal property, and stability analyses of the SNPs were systematically performed. The obtained SNPs exhibited good uniformity and almost perfect spherical and square shapes. The zeta potential and Fourier transform infrared spectroscopy results confirmed that the SNPs were covered with negative carboxyl groups (zeta potential ranging from -21.8 ±â€¯1.06 to -9.78 ±â€¯0.89 mV). The gelatinization enthalpy of SNPs from PS significantly decreased, changing from 16.63 ±â€¯0.91 to 9.81 ±â€¯0.19 J/g. However, the crystal patterns of SNPs from the WCS and PS after plasma and ultrasonic treatments did not change. The crystallinity of SNPs from PS decreased from 45.2% to 16.5%. This novel approach to preparing SNPs is low cost, simple and green. The developed SNPs could have great potential in the food, biomedical, and material industries.

Complexation of Amylosucrase-Modified Waxy Corn Starch with Fatty Acids: Determination of Their Physicochemical Properties and Digestibilities.

In this study, starch-lipid complexes were prepared using normal corn starch (NC) and amylosucrase-modified waxy corn starch (ASWC) with myristic acid (C14:0) and palmitic acid (C16:0). The amylosucrase modification elongated branch chains in waxy corn starch leading to an increase of apparent amylose content (29.7%) similar to that of NC (29.0%). The X-ray diffraction of starch-lipid complexes revealed a V-type pattern, a clear indication of complex formation. The ability of the ASWC to complex with fatty acids was greater than that of NC. Interestingly, the changes in relative crystallinity, thermal parameters, and digestion properties according to the complexation showed opposite patterns in NC and ASWC. This study found that the structure of ASWC contributes to the formation of starch-fatty acid complexes and suggested that the ASWC can be preferred over NC in a delivery system. PRACTICAL APPLICATION: Amylopectin has been considered to be incapable of forming complexes with fatty acids due to its short chain length and steric hindrance. Through this study, an appropriate enzymatic modification of the molecular structures of waxy starches could make a complexation of waxy starches with fatty acids possible. The findings of this study suggest a promising perspective for utilization of waxy starch as a carrier material of lipophilic molecules.

Impact of continuous and repeated dry heating treatments on the physicochemical and structural properties of waxy corn starch.

In order to investigate the impact of continuous dry heating treatment (CDHT) and repeated dry heating treatment (RDHT) on the structural and physicochemical properties of the waxy corn starch, the starch was prepared at 140 °C for continuous 20 h or for 5 cycles of heating, respectively. Each cycle lasted 4 h and the interval between each cycle was 1 h of cooling at room temperature. It turned out that RDHT and CDHT caused the aggregation of the starch into big lumps. The crystal type of CDHT and RDHT starches remained A-type, while the relative crystallinity and the short-range molecular order of starch characterized with 1040 cm-1/1018 cm-1 increased during first 2 circulations of RDHT and first 8 h of CDHT afterwards decreased upon the increased duration. After the heat treatment the water absorption index, swelling volume, viscosity and thermal parameters of CDHT and RDHT starches decreased, but the solubility, paste clarity and paste temperature of starches increased compared with native starch. Taken together RDHT has a greater impact on decreasing transmittance of starch paste, weakening the resistance to shear force and increasing retrogradation degree of starch paste compared to CDHT for the same duration.

Molecular, crystal and physicochemical properties of granular waxy corn starch after repeated freeze-thaw cycles at different freezing temperatures.

The study was undertaken to reveal the effects of freeze-thaw cycles at different freeze temperature (-20 °C, -40 °C and -80 °C) and the number of freeze-thaw cycles (3, 6, 12, 18, 24 times) on physicochemical and structural properties of waxy corn starch. The number of pores on the surface of starch granules increased, but there was no significant (P < 0.05) effect on molecular weight, transparency, freeze-thaw stability and the crystal structure of starch after repeated freeze-thaw cycle. But the crystallinity intensity decreased after freeze-thaw cycles treatment and a tiny decrease in onset, peak, conclusion temperature and gelatinization enthalpy were found. The RVA analysis exhibited an increase in gelatinization temperatures and a decrease in breakdown and setback value after freeze-thaw treatment, which manifested an increase in the aging and heat resistance of waxy corn starch paste. However, there was no statistical (P < 0.05) difference between different freeze temperatures at the same number of freeze-thaw cycle on physicochemical and structural properties of starch. The obtained data could be helpful in evaluation of the repeated freeze-thaw treatment of waxy corn starch-based foodstuffs and providing the theoretical basic for revealing the effect of repeated freeze-thaw processes in manufacture applications.

The effect of branched limit dextrin on corn and waxy corn gelatinization and retrogradation.

The effect of branched limit dextrins (BLDs) on the gelatinization and retrogradation properties of corn and waxy corn starch was investigated using differential scanning calorimetry (DSC), wide X-ray diffraction (WXRD). The DSC data showed that the presence of BLDs increased the gelatinization and decreased the gelatinization enthalpy (ΔHgel). The retrogradation of corn and waxy corn starch were retarded by BLDs. The BLD with the lowest molecular weight had the best influence on corn and waxy corn starch retrogradation. The result of WXRD confirmed it. Avrami equation was used to analyze the enthalpies of retrograded corn and waxy corn starch. Starch recrystallization rate (k) reduced with the addition of BLDs, indicating that BLDs reduced the kinetics of starch retrogradation.

Pasting and thermal properties of waxy corn starch modified by 1,4-α-glucan branching enzyme.

Waxy corn starch was modified with the 1,4-α-glucan branching enzyme (GBE) from Geobacillus thermoglucosidans STB02. Incubating waxy corn starch with GBE increased the number of α-1,6 branch points and reduced the average chain length. Enzymatic modification also decreased the breakdown and setback values of Brabender viscosity curves, indicating that the modified starch had higher paste stability. Preheating the starch at 65°C for 30min before incubation with GBE could promote enzymatic modification of starch. Linear regression was used to describe the relationships between starch structure and its pasting and thermal properties. The setback value showed a negative linear correlation with the α-1,6 branch point content (R2=0.9824) and a positive linear correlation with the average chain length (R2=0.8954). Meanwhile, the gelatinization enthalpy was also linearly correlated to the α-1,6 branch point content (R2=0.9326) and the average chain length (R2=0.8567). These insights provide a useful reference for food processors.

Impact of amylosucrase modification on the structural and physicochemical properties of native and acid-thinned waxy corn starch.

Recombinant amylosucrase from Neisseria polysaccharea was utilized to modify native and acid-thinned starches. The molecular structures and physicochemical properties of modified starches were investigated. Acid-thinned starch displayed much lower viscosity after gelatinization than did the native starch. However, the enzyme exhibited similar catalytic efficiency for both forms of starch. The modified starches had higher proportions of long (DP>33) and intermediate chains (DP 13-33), and X-ray diffraction showed a B-type crystalline structure for all modified starches. With increasing reaction time, the relative crystallinity and endothermic enthalpy of the modified starches gradually decreased, whereas the melting peak temperatures and resistant starch contents increased. Slight differences were observed in thermal parameters, relative crystallinity, and branch chain length distribution between the modified native and acid-thinned starches. Moreover, the digestibility of the modified starches was not affected by acid hydrolysis pretreatment, but was affected by the percentage of intermediate and long chains.

Preparation and characterization of the inclusion complexes between amylosucrase-treated waxy starch and palmitic acid.

Amylosucrase-treated waxy corn starch (AS) was produced to extend the chain length of amylopectin to a great extent in comparison to its native chain length. An amylopectin-palmitic acid (PA) complex was prepared by heat-treating (121°C) a starch/PA mixture and its subsequent further incubation (95°C, 24 h); moreover, its structure and digestibility were studied. Unmodified waxy starch could not complex at all, whereas elongation due to amylosucrase modification allowed amylopectin to form a complex with PA to a small extent. Complexation between AS and PA caused a decrease in relative crystallinity. The AS-PA complex displayed an endothermic peak representing type I inclusion complexes rather than type II complexes. The formation of complexes did not significantly affect the in vitro digestibility maintaining the low digestibility of AS resulting from extremely small amounts of complexes and the type of complex.

New insights into the action mode of amylosucrase on amylopectin.

To investigate the action mode of amylosucrase (AS) on amylopectin, waxy corn starch (WCS) was selected as an acceptor. The effects of WCS dissolution method, reaction temperature, sucrose concentration and AS activity on transglycosylation degree (TD) were investigated. Under the selected reaction condition, the enzymatic reaction process was divided into two stages, i.e. before and after 0.25h, of which the relations between TD value and reaction time were successfully described using a linear and a logarithmic function, respectively. Then, the elongated WCSs with different TDs were produced according to the theoretical reaction time calculated based on the regression equations. The chain length distribution of the elongated WCSs indicated that all of the branch chains of WCS were greatly elongated by AS before occurrence of starch precipitation. Afterwards, however, AS merely elongated the branch chains whose non-reducing ends were exposed on the surface of the precipitate.