Degradability of Different Phosphorylated Starches and Thermoplastic Films Prepared from Corn Starch Phosphomonoesters

Different starch types (corn, rice, potato, corn amylose and corn amylopectin) were phosphorylated to varying degrees of substitution (DS) and tested both for acid hydrolysis during 3 h in a boiling bath and for enzymatic hydrolysis with a thermostable bacterial α‐amylase (Bacillus licheniformis) for 30 min at 95 °C. Generally, phosphorylated starches showed a reduced degree of acid hydrolysis during the entire time of hydrolysis (3 h) as well as reduced susceptibility to α‐amyIase hydrolysis. The enzyme action was inhibited by the presence of phosphate groups in the modified starch molecules and the extent of inhibition increased with increasing degree of phosphate substitution, regardless of the starch type. Thermoplastic films were fabricated by blending modified corn starches of different DS with polyacrylate, urea and water at a ratio of 4:5:1:50, heating for 30 min at 95 °C before casting and allowing to cool, stand and dry at room temperature. The plastic films prepared from phosphorylated corn starch showed both higher disintegration rate and a greater degradability by thermostable bacterial α‐amylase than the ones prepared from non‐phosphorylated starch. These new acquired properties can meet the increasing demand for biodegradable disposable plastic bags.     

Characterisation of Fractions Obtained by Isoamylolysis and Ion‐exchange Chromatography of Cationic Waxy Maize Starch

Isoamylase hydrolysates of wet‐ (WC) and dry‐cationised (DC) waxy maize starch were fractionated by ion‐exchange chromatography on CM‐Sepharose into an unbound and four bound fractions. The amount of bound dextrins was higher in the WC than in the DC sample. The fractions were characterised by gel‐permeation chromatography and proton‐NMR spectroscopy. The unbound fraction from the WC sample consisted mainly of linear chains formed from amylopectin. The dextrins in the bound fractions contained increased amounts, from 1.2—7.9, of cationic substituents per molecule and the degree of polymerisation increased with the density of substituents. Dextrins weakly bound to CM‐Sepharose had a linear structure, whereas more tightly bound fractions were mixtures of linear and branched dextrins. In the latter, the debranching was incomplete because of sterical hindrance by substituents at or close to the branch points. Most of the dextrins were partly hydrolysed by β‐amylase, but the more highly substituted fractions possessed also a population of β‐amylase resistant dextrins, suggesting substituents at the non‐reducing ends.     

Determination of Optimum Conditions for Enzymatic Debranching of Cassava Starch and Synthesis of Resistant Starch Type III using Central Composite Rotatable Design

Cassava starch was debranched by treatment with isoamylase and pullulanase and the yield of resistant starch type III (RS III) optimized with respect to starch solids concentration (7.5‐15%, w/v), incubation time (8‐24 h) and enzyme concentration using central composite rotatable design. Higher concentrations of pullulanase (10‐35 U/g starch) compared to isoamylase (30–90 mU/g starch) were required to give a similar degree of starch hydrolysis within the experimental domain. A clear debranching end‐point was identifiable by following the reducing value, blue value and β‐hydrolysis limit of cassava starches debranched using isoamylase. It was difficult to define a debranching endpoint of pullulanase treatment by these parameters due to contaminating α‐D ‐(1→4) activity. The yield of RS III was significantly higher in isoamylolysates and increased steadily with increasing degree of hydrolysis to peak at 57.3%. Purification of the debranched material further increased the RS III yield to 64.1%. Prolonged (24 h) hydrolysis of cassava starch with high concentration of pullulanase (35 U/g) gave lower RS III contents in the purified (34.2%) and unpurified (36.2%) hydrolysates compared to 49.5 and 62.4%, respectively, at moderate pullulanase concentration (22.5 U/g) and incubation time (16 h).     

Characterization of Residues from Partially Hydrolyzed Potato and High Amylose Corn Starches by Pancreatic α‐Amylase

High amylose corn starch (HACS) and potato starch were hydrolyzed by pancreatic α‐amylase in vitro. Residues after hydrolysis were collected and characterized for their physicochemical properties and molecular structure. Compared with raw starches, residues had lower apparent amylose contents and higher resistant starch contents. The gelatinization enthalpy of residues from HACS increased while enthalpy of residues from potato starch decreased from 15.4 to 11.3 J/g. Peak viscosity and breakdown values of the residues from potato starch were markedly decreased but final viscosity values did not show much change. Chain length distribution of debranched amylopectin from the residues indicated that the relative portion of short chain in the residue decreased for both starches. More molecules with intermediate chain length (DP 16—31) were found in residue after 48‐h hydrolysis of potato starch.     

响应面试验优化晶种诱导-双酶复合法制备RS_3型籼米抗性淀粉工艺

以微波预糊化籼米淀粉为原料,自制RS_3型马铃薯抗性淀粉为晶种,研究RS_3型籼米抗性淀粉的晶种诱导-双酶复合法制备工艺。利用扫描电子显微镜对淀粉颗粒形貌进行表征并研究淀粉的抗酶解性。在单因素试验的基础上,固定其他酶解条件,以RS_3型籼米抗性淀粉产率为响应值,确定晶种添加量、异淀粉酶添加量、普鲁兰酶添加量和普鲁兰酶酶解时间作为影响产率的主要因素,进行Box-Behnken响应面优化试验。得到RS3型籼米抗性淀粉的最佳制备工艺条件为:晶种添加量5%、异淀粉酶添加量8 U/g、普鲁兰酶添加量8 U/g、普鲁兰酶酶解时间3.50 h。在此最佳制备工艺条件下,RS_3型籼米抗性淀粉产率为27.42%,RS3失去原有的淀粉颗粒形貌,表面变得粗糙,结晶结构致密,具有较强抗酶解能力。     

Lintnerization of Two Amylose‐free Starches of A‐ and B‐Crystalline Types,Respectively

Waxy maize starch (WMS) and potato amylopectin starch (PAPS), representing amylose‐free A‐ and B‐crystalline granules, respectively, were subjected to hydrolysis in diluted hydrochloric acid (lintnerization). The solubilization rate of the granules was dependent on the temperature, but there were only small differences between the samples. The compositions of the lintners obtained at 29°C were also similar, though the sensitivity to enzymatic debranching was different. The degree of debranching increased significantly if pullulanase and isoamylase were used successively. Because some branches remained resistant to enzymatic attack, the degree of scattered branching was difficult to estimate. The amount and composition of β‐limit dextrins suggested, however, that both starches contained scattered branches. Long chains and the shortest chains in the amylopectin molecules were sensitive to lintnerization and therefore probably located outside the crystallites. The composition of the PAPS lintners was dependent on the temperature of the lintnerization, whereas that of WMS lintners was not. The composition of a lintner from normal potato starch was compared with PAPS, and it is concluded that the presence of amylose has a higher effect than the type of crystallinity on the lintnerization results.     

Visual Observation of Hydrolyzed Potato Starch Granules by α‐Amylase with Confocal Laser Scanning Microscopy

Porous starch was produced by digestion of freeze‐dried potato starch with α‐amylase from Bacillus sp. The surface structure of the granules became perforated and in the interior of the granules a capsule‐like cavity was formed, i.e. the hydrolyzed starch can be used as an encapsulant. The structure change of the granules was observed with confocal laser scanning microscopy and scanning electron microscopy. The degree of starch hydrolysis could be correlated with the Avrami equation. The activation energy of starch hydrolysis by α‐amylase was 83 kJ/mol.     

Amidons Lintnérisés Etudes chromatographique et enzymatique des résidus insolubles provenant de l'hydrolyse chlorhydrique d'amidons de céréales,en particulier de maïs cireux

Lintnerized Starches. Chromatographic and Enzymatic Studies of Insoluble Residues from Acid Hydrolysis of Various Cereal Starches, Particularly Waxy Maize Starch . Native cereal starches, particularly waxy maize starch, have been carefully hydrolyzed at 35°C with hydrochloric acid (2,2-N) in heterogeneous phase. Observation of the course of hydrolysis as a function of time makes it possible to classify the starches according to their acid lability. The kinetic values distinctly reveal two phases, i.e. a fast hydrolysis of the amorphous fraction and a slower degradation of the crystalline starch grain fraction. This observation was confirmed by X-ray diffractometric patterns. The hydrolysis speed of acid resistant fractions seems to become slower as the apparent amylose ratio increases. The change in the macromolecular structure of the obtained granular residues or “lintnerized” starches as a function of time was examined after aqueous solubilization by means of gel chromatography using a calibrated Sephadex G-50 column. Lintnerization causes a decrease in the apparent DP of the chains of the starch residues and two subgroups with apparent DP 13 and 25 appear rapidly. These DP are unchanging with time of acid treatment. The chromatographic and enzymatic studies of lintnerized starches were performed directly and after successive enzymatic digests with pullulanase and ß-amylase. After debranching of solubilized residues with pullulanase and gel chromatography a linear chain subgroup of DP 15–20 appears. This one is in fact composed of two subgroups: one more important with a DP 13, the other broad distribution with a DP 15–25. The comparison with the subgroups observed before debranching shows that a main part of the initial subgroup of DP 25 could be considered as formed with singly branched chains. Furthermore a small proportion of pullulanase resistant ß-limit dextrins was obtained. The obtained results permits one to suggest a new model for the structure of waxy maize amylopectin. On the basis of this model the differences in structure existing between the various starches are discussed and the results are compared with those reported elsewhere for potato starch. A parallelism between crystalline patterns of native starches and the amylopectin structure, particularly its branching degree, is observed.     

Granule structural,crystalline, and thermal changes in native Chinese yam starch after hydrolysis with two different enzymes–α‐amylase and gluco‐amylase

Starch extracted from Chinese yam was characterized by scanning electron microscope (SEM), X‐ray powder diffractometer (XRD), and differential scanning calorimeter (DSC) in the process of enzymatic hydrolysis. Yam starch was digested by α‐amylase and gluco‐amylase for different lengths of time, respectively, and two different enzymatic hydrolysis results were compared. The most notable phenomenon revealed by SEM after α‐amylase hydrolysis was the formation of the cavum in the center of the starch granules, while after gluco‐amylase hydrolysis, the outer layer of the granules was peeled off and then some granules even broke into pieces. The XRD of the two enzyme hydrolyzed starches revealed the crystal type of the starch changed from typical C‐type XRD pattern to the representative A‐type pattern in the process of enzymatic hydrolysis. The above results also demonstrated that the partially B‐type polymorph was more easily degraded than A‐type. The thermal result showed that the modified yam starches by both enzymes exhibited increased peak gelatinization temperatures (T_p) and decreased gelatinization enthalpy (ΔH).     

Effects of Modification Sequence on Structures and Properties of Hydroxypropylated and Crosslinked Waxy Maize Starch

The effects of modification sequence on chemical structures and physicochemical properties of hydroxypropylated (HP) and crosslinked (XL) waxy maize starch were investigated. The physicochemical properties, including pasting, gelling, and thermal properties, were studied. The chemical structures of dual‐modified starches and their beta‐limit dextrins were characterized with high‐performance liquid chromatography. The HP‐XL starch had higher Brabender viscosity than did the XL‐HP starch at both pH 7 and 3; however, both showed similar gelling properties. Significantly higher onset and peak gelatinization temperatures, gelatinization enthalpy, and lower retrogradation were observed for the HP‐XL starch. The HP‐XL starch also exhibited significantly higher beta‐amylolysis limit and higher content of low molecular weight saccharides in its isoamylase‐debranched starch, suggesting its structure was more accessible to enzymatic attack than the XL‐HP starch. Structural analyses revealed different distribution patterns of modifying groups between the two modified starches. The results indicate that the modification sequence altered the susceptibility to enzymes, changed the locations of substitution, and modified the physicochemical properties of the HP and XL waxy maize starches.     

Substituent distribution within cross-linked and hydroxypropylated sweet potato starch and potato starch

Revealing the substituents distribution within starch can help to understand the changes of starch properties after modification. The distribution of substituents over cross-linked and hydroxypropylated sweet potato starch was investigated and compared with modified potato starch. The starches were cross-linked with sodium trimetaphosphate and/or hydroxypropylated with propylene oxide. The native and modified starches were gelatinized and hydrolysed by pullulanase, β-amylase, α-amylase and a combination of pullulanase, α-amylase and amyloglucosidase. The hydrolysates were analysed by HPSEC, HPAEC and MALDI-TOF mass spectrometry. Cross-linking had only a slight effect on the enzymatic hydrolysis, where hydroxypropylation evidently limited the enzymatic hydrolysis. The results obtained suggest that the hydroxypropyl substituents are not distributed regularly over the starch chains. Although the average substitution was around 2 hydroxypropyl groups per 10 glucose units, in the enzyme digests of hydroxypropylated starches, oligomer fragments of 10–15 glucose units, carrying 5–8 hydroxypropyl groups, were identified. It is hypothesised that higher levels of substituents are present in the amorphous regions and periphery of clusters of starch granules. This is the first time that the location of hydroxypropyl groups within sweet potato starch has been examined in this detail. Despite significant differences in granule architecture between starches from potato and sweet potato, similar patterns of hydroxypropylation have been found.     

Properties of Low‐substituted Cationic Starch Derivatives Prepared by Different Derivatisation Processes

Cationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution ¹³C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid. The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different. The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.     

Molekulare Struktur und physikalischchemische Eigenschaften von löslichen Stärken und Dextrinen

Molecular Structure and Physico-chemical Properties of Soluble Starches and Dextrins. Physico-chemically modificated starches, so called soluble starches show about ten times increases of reductivity and decrease of molecular weight as compared with native starch. Roasted starch without chemicals undergoes the most significant changes. Smaller and smaller changes are present successively in lintnerizated starches with hydrochloric, nitric and phosphoric acids. Soluble starches slightly α-amylase hydrolyzed in dependence on the reaction time change into high-molecular or medium-molecular dextrins with increasing during reaction degree of reductivity from 0,4 to 4 DE and decreasing molecular weight from 40000 to 6000. During α-amylase hydrolysis of soluble starches to dextrins average number of end-groups decreases in molecules from 11 to 4 and the number of branchings from 10 to 3.     

Preparation and Characterization of Annealed‐Enzymatically Hydrolyzed Tapioca Starch and the Utilization in Tableting

Tapioca starch was annealed at 60°C for 90 min followed by hydrolysis with α‐amylase at 60°C at various lengths of time (30, 60 and 120 min) to obtain high‐crystalline starches. The reaction products were subjected to spray drying to obtain annealed–enzymatically hydrolyzed–spray dried tapioca starch (SANET) in the form of spherical agglomerated granules. The properties of SANET were compared with those of annealed–spray dried tapioca starch without enzymatic treatment (SANT) and native–spray dried tapioca starch (SNT). Scanning electron micrographs of the starch samples were used to study the morphological changes and to suggest the mode of enzyme attack during hydrolysis. The á‐amylase preferentially attacked the interior of the starch granules, leaving a deep round hole on the starch granule surface. It was found by X‐ray diffraction that both annealing and amylolysis did not alter the A type diffraction pattern. The% relative crystallinity of SANET was raised with increasing hydrolysis time and with decreasing amylose content. High performance size exclusion chromatography (HPSEC) demonstrated the decrease of the degree of polymerization (DP) of the amylose fraction of SANET after prolonged hydrolysis. For the utilization of SANET as tablet filler, it was directly compressed by a tablet compression machine at 4 kN to obtain tablets. The increased relative crystallinity of starch resulted in increased crushing strength and disintegration time, but in a decreased tablet friability.     

Structure Analysis of Carboxymethyl Starch by Capillary Electrophoresis and Enzymic Degradation

Carboxymethyl starches (CMS) with a degree of substitution (DS) in the range of 1.2 to 1.5 were analysed by capillary electrophoresis (CE) after hydrolysis and reductive amination in a borate buffer. The monomer composition determined was compared to data calculated by the statistical models of Spurlin and Reuben. In addi­tion, the starch derivatives were exhaustively degraded by α‐amylase and amylo­glucosidase and the amount of glucose liberated was determined. Results were discussed with regard to derivatisation conditions and properties of the carboxymethyl starches.     

Preparation and Evaluation of Hydroxyethyl Starch

Hydroxyethyl starches were prepared by reaction of potato and corn starches with ethylene oxide. The degree of substitution (DS) was determined by the acetylation method and was 0.02 to 0.20 per glucose unit. Determination of position of the alkoxyl groups by thin layer chromatography indicates that 85% of the groups were attached to C2. Periodic oxidation of the hydroxyethyl starch indicated decrease with the increase of DS due to the resistance of C2–3 substituted glycol to cleavage. The iodine adsorption decreased with increasing DS. Therefore iodine adsorption could be taken as a measure of the degree of modification of starch molecule.     

3种大米淀粉脱支前后结构及流变特性

通过普鲁兰酶处理糯米、粳米和籼米淀粉,研究酶水解对3 种大米淀粉结构和流变特性的影响。结果表明,经普鲁兰酶处理后3 种大米淀粉的结晶度降低,无定型区域增加;链长分布结果表明3 种大米淀粉的精细结构相似,水解反应对较短的侧链更有效,糯米淀粉更易被酶解;脱支淀粉和天然大米淀粉的傅里叶变换红外光谱没有明显差异,—OH的伸缩振动吸收峰相对增强;添加普鲁兰酶后,淀粉糊黏度急剧下降,糯米淀粉黏度下降最快,较容易被水解;流变学特性表明淀粉颗粒分子间缔合、排列松散,运动性增强,溶解度和持水力有所增强。糯米淀粉对普鲁兰酶处理较其他两种大米淀粉更为敏感。结论：脱支处理改善了淀粉凝胶性能,增强了淀粉的流动性。     

Effect of debranching and storage condition on crystallinity and functional properties of cassava and potato starches

Debranching starch by pullulanase is considered to improve the RS content of starch which is widely used to produce the starch‐based foods with high‐health benefit impacts. In this study, the cassava and potato starches were debranched by pullulanase, followed by an autoclave treatment and storage at −18°C, 4°C, or 25°C to investigate their crystallinity and functional properties. After debranching, the potato starch contained significantly higher CL (35.4 glucose units) than did the cassava starch (32.4 glucose units). The debranched cassava and potato starches after retrogradation at the storage temperatures had a typical B‐type crystalline structure although the native cassava and potato starches exhibited the different crystalline forms (A‐ and B‐type, respectively). The RS contents of the debranched cassava and potato starches significantly improved with higher RS content of the debranched potato starch than that of the debranched cassava starch at the same storage condition. The storage temperature significantly affected the RS formation of the debranched starches with the highest RS content at storage temperature of −18°C (35 and 48% for the debranched cassava and potato starches, respectively). The debranched starches had significantly lower viscosities and paste clarities but higher solubilities than did the native starches. As a result, the debranched cassava and potato starches can be considered for use not only in functional foods with enhanced health benefits but also in pharmaceutical and cosmetic industries.     

Response surface optimization and characteristics of Indica rice starch‐based fat substitute prepared by α‐amylase

Response surface methodology (RSM) was used to study the effect of enzyme to substrate ratio (11.8–23.6 U α‐amylase/g rice starch), hydrolysis temperature (90–100°C) and pH value (6.0–6.6) on the gel strength of rice starches‐based fat substitute using α‐amylase hydrolysis. The optimum conditions obtained from response surface analysis was 16.52 U/g enzyme dosage, 92°C hydrolysis temperature while the influence of pH was found insignificant in the range tested. Under these optimum conditions, the gel strength of this fat substitute was 113 g/cm², very close to the gel strength of butter of 114 g/cm², while the solubility of the substitute was 1.33 ± 0.01% and the swelling power 4.85 ± 0.02. There were no observable differences in the granular size distribution between the untreated rice starch and the hydrolyzed rice starch. Rheological properties of this rice starch‐based fat substitute implied that it is easier for the substitute to form three‐dimensional networks under 34°C.     

Characterization of nanoparticles prepared by acid hydrolysis of various starches

Various starches of different AM contents and origins such as wx maize, normal maize, high AM maize, potato, and mungbean starches were hydrolyzed using a H₂SO₄ solution (3.16 M) at 40°C for 7 days, and the starch particles were isolated from the hydrolysates by centrifugation. The hydrolysis rates varied from 61.4 to 90.9% depending on the starch type. Unexpectedly, A‐type starches were more resistant to the acid hydrolysis than B‐type starches. XRD results revealed that the starch particles with B‐crystalline type exhibited a decrease in peak intensity. In addition, in a DSC analysis, the crystals remaining in the B‐type starch particles were readily disrupted in the water dispersion so that no melting endotherm appeared. Electron microscopy confirmed that the starch particles had round or oval shapes with diameters ranging from 40 to 70 nm, which possibly represented the starch blocklets in granules. The acid degraded mainly AM and long AP chains, resulting in increasing the proportion of short chains.