CHARACTERIZATION OF THE ACTION OF BACILLUS SUBTILUS ALPHA-AMYLASE ON SWEET POTATO STARCH,AMYLOSE AND AMYLOPECTIN1

The action pattern of Bacillus subtilis alpha-amylase on Jewel variety sweet potato starch, amylose and amylopectin was monitored using high performance size exclusion chromatography. A wide range of products, from high molecular weight polysaccharides to specific saccharides of low molecular weights, were observed. The hydrolysis pattern for amylose in starch was concealed by hydrolytic fragments formed from amylolysis of the greater quantity of amylopectin. Amylopectin was degraded to a more specific mixture of polysaccharide fragments. Changes in molecular size of hydrolytic fragments formed during amylolysis supported the cluster model previously proposed for amylopectin. These results also suggest that the action of alpha-amylase on sweet potato starch is generally a nonrandom process, primarily resulting from enzymatic action on amylopectin. To support this hypothesis, a more random pattern of hydrolysis was observed from acid treated starch.     

Molecular Weight Characterization and Gelling Properties of Acid-Modified Maize Starches

The reduction in the molecular weight distribution during acid hydrolysis of ordinary and waxy maize starch occured in two stages: first amylopectin degraded to intermediate high molecular weight polysac-charides, secondly, these were further hydrolyzed. The amylose moiety of ordinary and high-amylose starch was not affected very much by the hydrolysis conditions used (0.1–1 M HCI, 40°C, 0.3–4 h), but the gelling properties of starch weakened. The amylopectin degradation products, probably branched dextrins, were shown to hinder the gel formation of amylose in the starch pastes.     

Wx基因对小麦淀粉生物合成和积累的影响

为研究Wx基因的缺失对小麦淀粉生物合成的影响,本研究以8个Wx小麦近等基因系为材料,在灌浆期的10、20、30和40 d取籽粒测定直链淀粉、支链淀粉、总淀粉的含量及合成速度。结果表明:直链淀粉、支链淀粉和总淀粉含量及积累速率在花后逐渐增加,以花后10~20 d最大,此后逐渐降低。3个Wx基因对直链淀粉的含量及积累速率的影响依次为Wx-B1Wx-A1Wx-D1;小麦Wx基因型对直链淀粉的合成及积累速率影响较大,而对支链淀粉的影响较小,其对总淀粉含量及其积累的影响主要通过直链淀粉进行。     

THE SUSCEPTIBILITY OF CEREAL STARCHES TO AMYLOLYSIS DURING GERMINATION AND MATURATION

During the maturation of normal and high amylose barley the susceptibility of the raw starches to attack by α-amylase remains constant until the moisture content of the grain falls below about 60%. Thereafter the starch develops a resistance to amylolysis which is directly proportional to the loss of grain moisture. The mean diameter of the starch granules of barleys and malt remains unchanged during digestion but the blue values of the residual starches decrease throughout. During the malting of wheat and barley the bulk of the starch solubilized is the amylopectin fraction although amylose is increasingly utilized when germination is prolonged. When high amylose barley is malted the blue value of the starch declines steadily throughout the growth period, suggesting that the spatial arrangements of the molecules within the granule influence the solubilization of the starch. The susceptibilities of wheats and normal and high amylose barleys to amylolysis were significantly lower than those of the corresponding malted products.     

Starch Structure and Digestibility of Rice High in Resistant Starch

Starch digestibility and starch structure of a high‐resistant starch (RS) rice (RS111) was compared to that of a wild rice type (R7954). RS111 exhibited high RS content and incomplete starch hydrolysis in both cooked rice and retrograded rice flour. High RS rice RS111 had a higher λ_max of absorbance and blue value of iodine‐binding starch complex and contained a higher percentage of intermediate chains of amylopectin than R/954. X‐ray diffraction pattern of RS isolated from cooked high RS rice displayed a mixture of B‐ and V‐type that was more resistant to starch hydrolysis by alpha‐amylase. Resistant starch in RS111 is composed mainly of linear amylose and some low‐molecular‐weight amylopectin.     

Influence of Selected Parameters of Starch Gelatinization and Hydrolysis on Stability of Amylose‐Lipid Complexes

Dissociation of amylose – lipid complexes (AMLs) upon gelatinization and enzymatic hydrolysis of wheat starch has been examined using differential scanning calorimetry (DSC). Digestion of starch by the thermostable α‐amylase THERMAMYL 120L was carried out under conditions applied for enzymatic hydrolysis of wheat starch in industry, i.e. 5 min incubation at 105°C, followed by 60–90 min hydrolysis at 95°C. For comparison reasons, samples of wheat starch slurries were incubated under the same conditions but in the absence of enzyme. The enthalpy and temperature of AMLs dissociation and the shapes of peaks in the DSC endo‐ and exotherms depended on conditions of starch processing prior to DSC measurements. Wheat starch gelatinization coupled with its digestion by α‐amylase resulted in more pronounced AML degradation as compared to gelatinization in the absence of enzyme. Different shapes of peaks in thermograms and different temperatures of AMLs dissociation and reassociation indicate that different AML polymorphs were generated in the examined samples. Their concentrations depended on conditions (temperature, time and the presence or absence of α‐amylase) of wheat starch treatment.     

Effect of annealing on the semicrystalline structure of normal and waxy corn starches

The influence of amylose and amylopectin on structural reorganization occurred during annealing was studied for normal and waxy corn starches. Annealing caused an increase in crystallinity in the waxy corn starch, whereas the number of pores on the granule surface, observed by SEM, increased especially for normal corn starch. Amylose and amylopectin chains of the annealed normal corn starch were degraded to greater extension during enzymatic hydrolysis than those of the native starch. On contrary, the annealing caused a protective effect on waxy corn starch amylopectin toward the enzymatic reaction suggesting that this treatment promoted a better interaction between amylopectin chains of waxy corn starch. The amylose molecules of normal corn starch may have impaired the mobility of amylopectin molecules and restricted the reorganization of the crystalline structure during the annealing. The major increase in pores number on the granule surface of annealed normal corn starch, resulted of the endogenous amylase action during annealing, could facilitate the exogenous enzymes’ role in the degradation of the starch granules’ amorphous area.     

ACTION PATTERN OF BACILLUS LICHENIFORMIS ALPHA-AMYLASE ON ORDINARY, WAXY, AND HIGH-AMYLOSE CORN STARCHES AND THEIR HYDROXYPROPYL DERIVATIVES

The action of thermally stable alpha-amylase from Bacillus licheniformis on ordinary, waxy and high-amylose corn starches and their hydroxypropyl derivatives gave distinctive patterns of malto-oligosaccharide products that were dependent on conversion time. These alpha-amylolysis patterns of the various starches were derived from high performance liquid chromatographic analyses of the oligosaccharide compositions produced at various levels of hydrolysis. The products from amylolysis at high substrate concentrations (20–30%) and elevated temperature (95°C) suggest an endo-specific hydrolysis of the amylose and amylopectin chains to give a trio product-specificity for the formation of DP₅, DP₃, and DP₂ oligosaccharides. These results confirm and expand the studies by Saito (1973) and Nakakuki et al. (1984), who found that B. licheniformis amylase degraded a 1% solution of short-chain amylose at 40° to give mainly DP₅ and DP₃ oligomers. The hydroxypropyl groups on ordinary, waxy and high-amylose starch derivatives greatly hindered alpha-amylolysis, but the action patterns were essentially the same.     

In vitro availability of starch in heat‐treated potatoes as related to genotype,weight and storage time

The objective of the study was to determine the influence of potato variety, weight and storage time after lifting on the glycaemic index (GI) and resistant starch (RS) content predicted from measurement of the rate and extent of in vitro starch hydrolysis, respectively. The potatoes were either boiled, or boiled and subjected to different heat‐cycling conditions selected to promote retrogradation of amylose or amylopectin, respectively. The hydrolysis indices (HI) and predicted GIs of all 19 potato products were high and fell within narrow ranges of 122–144 and 118–138, respectively. No correlation between average weight of the potato tuber and HI was found. Furthermore, there was no difference in HI between potatoes stored for 1–3 or 8–10 months, nor between varieties of new potato and winter potato. However, the HI was significantly lowered by temperature cycling at conditions known to promote retrogradation of amylopectin (6 °C, 48 h) compared with 6 °C for 24 h followed by 70 °C for 24 h. RS content was already substantial in boiled potatoes, 4.5 g 100 g^?1 (starch basis), and could be increased further by temperature cycling, the highest yield obtained, 9.8 g 100 g^?1 (starch basis), following heat treatment at 6 °C for 24 h followed by 70 °C for 24 h; that is at conditions known to favour amylose retrogradation. Copyright © 2004 Society of Chemical Industry     

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.     

The effect of concentration and botanical source on the gelation and retrogradation of starch

The changes in shear modulus of pea, wheat, maize and potato starch gels with time, at concentrations between 10 and 40% w/w, were followed. In this range, the cooling of gelatinised dispersions of starch resulted in turbid, elastic gels. The initial rate of development of stiffness of the gels followed the order: pea>maize>wheat>potato, and was related to the amount of amylose solubilised during gelatinisation. The initial gelation was not reversed on heating to 100° C. There was also a long-term increase in gel stiffness, which was thermally reversible. This long-term increase, linked to a crystallisation involving amylopectin, followed the order: pea>potato>maize>wheat. With increasing starch concentration this latter process becomes more important.     

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.     

Inner Structure of Potato Starch Granules

A combination treatment (dry-heat and glucoamylase) was applied on potato starch granules. Many inner granules in the granules after the treatments were observed by SEM. The inner granule located near edge of ellipsoid of granule was partially degraded X-ray diffraction pattern of starch granules did not change before and after the treatments in spite of over 50% loss by amylase digestion. GPC and iodine reaction of the sample showed the treatments brought about fairly large degradation of both amylopectin and amylose components, but GPC of debranched sample after the combination treatments showed amylose was thoroughly degraded while peaks pattern of amylopectin did not change. Small size granules were more susceptible than large size granules by the treatments.     

Ein Beitrag zur Biosynthese amylosereicher Erbsenstärken

Contribution to the Biosynthesis of High-amylose Pea Starches Biosynthesis of starch is a complex process but few details are still unknown. This paper describes an investigation upon pea starch biosynthesis. Peas as a source of starch offer two qualities, a pea starch with 40% amylose content (smooth pea starch) and a pea starch with more than 60% amylose content (wrinkled pea starch). Samples for analysis were taken during growth. According to the quantitative determination of starch and amylose the accuracy of amylose detection was tested. Furthermore a qualitative analysis was carried out by molecular weight estimation of the starch. Both kinds of peas showed a high amylose synthesis during the last few days of growth, whereas amylopectin synthesis was highly in earlier stages. Wrinkled peas have shown only little synthesis activity of amylopectin during maturity. Therefore the amylose content of these peas was higher, instead of equal amylose synthesis quotas of both smooth and wrinkled peas.     

Production and physicochemical properties of resistant starch from hydrolysed wrinkled pea starch

The content and physicochemical properties of resistant starches (RS) from wrinkled pea starch obtained by different molecular mass reduction processes were evaluated. Native and gelatinised starches were submitted to acid hydrolysis (2 m HCl for 2.5 h) or enzymic hydrolysis (pullulanase, 40 U g^?1 for 10 h), followed by hydrothermal treatment (autoclaving at 121 °C for 30 min), refrigeration (4 °C for 24 h) and lyophilisation. Native starch showed RS and total dietary fibre contents of 39.8% and 14.3%, respectively, while processed ones showed values from 38.5% to 54.6% and from 22.9% to 37.1%, respectively. From these, the highest contents were among acid‐modified starches. Processed starches showed endotherms between 144 and 166 °C, owing to the amylose retrogradation. Native and processed starches showed low viscosity, which is inversely proportional to the RS concentration in samples. The heat treatment promoted an increase in the water absorption index. The pea starch is a good source for obtaining resistant starch by acid hydrolysis.     

Effect of the Extent of Conversion and Retrogradation on the Digestibility of Potato Starch

The effect of starch conversion on the susceptibility of potato granules to α‐amylase was studied by direct sampling at different pasting times corresponding to different points on the RVA profile of a 6.4% (w/w) suspension of starch in distilled water. Native granules showed high resistance to α‐amylase with 8.6 ± 0.4% digestibility for a 6 h incubation period with the enzyme. When the suspension was heated to 60 °C, the digestibility increased to 53.5 ± 0.7% although, at this temperature, there was still no noticeable increase in the measured viscosity (≤0.040 Pa · s). The material sampled after a pasting time corresponding to the RVA peak viscosity showed a digestibility of 88.4 ± 0.5%. This suggested, owing to the expected retrogradation of amylose on cooling, the quasi‐total susceptibility of amylopectin to enzymatic digestion at this pasting stage. The effect of ions on the swelling of potato starch was used to assess whether the decrease of the swelling of the granules in the presence of NaCl was paralleled by an increase in resistance to α‐amylase. A small (∼6.1%) but significant decrease in the digestibility of pasted starch was observed in the presence of salt. Finally, the effect of the retrogradation of the amylopectin fraction on its digestibility was assessed in extruded potato starch ribbons containing 35% (w/w) water and stored at different temperatures. After 14 days of storage, the digestibility decreased from 77.0 ± 0.9% in the freshly extruded samples to between 28.0 ± 1.7% and 42.1 ± 0.3%, depending on the storage temperature. This suggested a measurable difference in the α‐amylase susceptibility between the A and B polymorphs of retrograded amylopectin.     

Insights into the relations between the molecular structures and physicochemical properties of normal and waxy wheat B-starch after repeated and continuous annealing

The effect of repeated annealing treatment (RANN) and continuous annealing treatment (CANN) on the structure, physicochemical properties and digestibility of wheat B-starch were studied. Annealing degraded the starch molecules, disrupted amylopectin and amylose structures, and decreased the molecular weight and the long chain of amylopectin. Meanwhile, the double helix structure and the crystalline and amorphous region were broken, the starch and water molecules were rearranged after RANN and CANN. As a result, annealing increased the crystallinity, gelatinisation temperature, resistant starch and slowly digestible starch content, while decreased the solubility, swelling power and pasting viscosity. The different changes of structural and physicochemical properties for normal and waxy B-starch upon annealing treatment were because of the different amylose contents and amylopectin chain mobility. The RANN exhibited greater advantages than CANN in the modification of the structural, physicochemical, and digestible properties of normal B-starch; while CANN significantly affected properties of waxy B-starch.     

Characterization of Dextrins obtained by Enzymatic Treatment of Cationic Potato Starch

The substitution pattern of cationic potato starches was studied using starch hydrolyzing enzymes and a characterization of the hydrolysis products. Native and cationic starch samples were hydrolyzed with pullulanase, isoamylase, and α‐amylase and the molecular‐weight distributions of the resulting dextrins were studied using gel permeation chromatography. Isoamylase hydrolyzed the native potato starch sample readily, whereas hydrolysis with pullulanase was incomplete. Pullulanase hydrolyzed, however, cationic starch with higher DS (degree of substitution) more efficiently than isoamylase. The hydrolysis products obtained with pullulanase were separated according to charge using cation‐exchange chromatography into one unbound and two bound fractions. The unbound fraction possessed an increasing number of short chains from amylopectin with increasing DS of the starch sample. The bound material contained amylose and dextrins with sizes corresponding to the long B‐chains. The high portion of uncharged dextrins after α‐amylolysis suggested that the substitution pattern, on the molecular level, was non‐random. The composition of the unbound and bound material, obtained by ion‐exchange chromatography of α‐amylase treated starches, suggested a more intense fragmentation with increasing DS of the sample. Possibly, the substituents influence substrate conformation and thereby alter the hydrolysis patterns. It is concluded that a thorough understanding of the enzymatic hydrolysis patterns is of ultimate importance in structural studies of modified starch.     

Effects of Wheat Starch Contents on Malt Qualities

The relationships between wheat starch content and wheat malt qualities were studied in the present work. Six wheat varieties that were typical in starch, protein content and amylopectin/amylose ratio were selected from 12 wheat varieties and germinated under the same conditions. The decreased degree of total starch content after malting had a positive correlation (r = 0.8020, P < 0.1) with the amylopectin/amylose ratio of the raw wheat. Extracts of wheat malts were influenced by starch content and the amylopectin/amylose ratio of the raw wheat. When the amylopectin/amylose ratio was in the range 3.65:1?3.93:1, extracts of the malts had significant positive correlation (r = 0.967, P = 0.002) with the starch content of the raw wheat. In this investigation a suitable amylopectin/amylose ratio (3.65:1 to 3.93:1), a high starch content and a low protein content were the characteristics of a wheat variety suitable for malting.     

Isolation and Some Properties of Amylase from Streptomyces hygroscopicus SF-1084

After screening about three thousands of Streptomyces strains from soils, a strain of Streptomyces hygroscopicus SF-1084, which gave the highest amylase production was isolated and some properties of the amylase were studied. Amylase production media were examined and a medium which consisted of glucose 2%, corn starch 5.5%, corn meal 1%, wheat germ 0.5%, soy bean meal 1.4%, KH₂PO₄ 0.2% adjusted to pH 7.0 was used to produce the amylase. Amylase production by 30 l jar fermenter was reached at 1500 u/ml in 110 h culture. The amylase was purified from broth filtrate by the method of ammonium sulfate precipitation, DEAE-sephadex A-50 column chromatography and Sephadex G-150 gelfiltration to get single band on a polyacrylamide disc gel electrophoresis. It is shown that the SF-1084 amylase produced 88% maltose from amylose and 80% maltose from amylopectin in 48 h saccharification. From the pattern of blue value and reducing value, the amylase is supposed to have endogenous action on starch and the activity is not inhibited by PCNB (pentachloronitrobenzene); the SF-1084 amylase does not belong to β-amylase. The optimum pH of the amylase was 5 to 6 and the optimum temperature was 50 to 55 °C. The amylase was fairly thermostable and the residual activity after incubation at 90 °C for 15 min and 100 °C for 15 min were revealed more than 50% and 30% respectively.