Effect of Cultivation Conditions on Retrogradation of Sweetpotato Starch

Sweetpotatoes were grown under four cultivation conditions, i. e. early planting and early harvesting (I, E‐E), standard (II, STD), early planting and late harvesting (III, E‐L), and late planting and late harvesting (IV, L‐L). Retrogradation of the starch isolated from fresh roots was estimated by the hardness and syneresis rate after two weeks of storage at 5 °C. A significant difference in retrogradation among the cultivation conditions and cultivars was observed. The starch tended to exhibit slower retrogradation in late harvesting, where the temperature was low. The differences in amylose content and the proportion of short unit‐chains (DP 9‐11) of amylopectin among cultivation conditions were also significant. Starch retrogradation was positively correlated with the proportion of chains with DP 12‐14 but negatively correlated with the proportion of DP 9‐11. Moreover, there was no significant correlation between amylose content and retrogradation. These results indicate that the main factor for retrogradation under any cultivation condition is the proportion of short unit‐chains of amylopectin. The best performance of sweetpotato starch as a food ingredient would be achieved by selecting both the proper cultivar and cultivation conditions.     

Starch Properties of New Sweet Potato Lines Having Low Pasting Temperature

Some new sweet potato lines were developed from progenies of a new cultivar, Quick Sweet, having a low pasting temperature. Starch granules from these lines demonstrated an abnormal morphology characterized by cracking into fragments. Starch and amylose contents were different among these lines. Pasting temperatures of these lines determined by the Rapid Visco Analyser were 53.8 to 66.6°C, i.e. 10 to 20°C lower than that of the control. Peak viscosities of some lines were similar to that of the control. Starch retrogradation, evaluated by percentage of leaked water and hardness of starch gels after cold storage, revealed that the control starch retrograded during storage for two to six weeks, but the starches of some lines retrograded much more slowly than the control starch and exhibited excellent cold storage stability. The pasting temperature had significant positive correlations with the percentage of leaked water and the hardness. These results indicate that Quick Sweet is a useful breeding material for improving pasting and retrogradation properties in sweet potato starch.     

Physicochemical Properties of Sweetpotato Starches with Different Gelatinization Temperatures

Physicochemical properties of five sweetpotato starches differing in gelatinization temperature were examined. The gelatinization temperature of Koganesengan starch, an ordinary cultivar of sweetpotato in Japan, was 73.6°C, whereas those of the other starches were measured to be 71.6°C for Kyukei 96162–1, 65.8°C for Kyushu No.127, 63.9°C for Kyukei 240, and 54.9°C for Quick Sweet. Some relationships of the primary structural properties with the gelatinization temperature have been found. As the gelatinization temperature decreased: i) the content of phosphate groups attached to the glucosyl residues decreased, ii) the amylose content, which was determined as difference in long chains of debranched original starch and of its amylopectin, decreased, iii) the proportion of unit chains with DP > 100 in the amylopectin fraction increased, iv) the proportion of unit chains with DP 6 to 10 in the amylopectin fraction increased, whereas that of unit chains with DP 12 to 24 decreased, v) the B‐type crystallinity of the starch granules was enhanced, and vi) the proportion of longer chains constituting each Nägeli amylodextrin increased. Moreover, it was found that thin pastes of the low temperature‐gelatinizing starches retrograded slower during cold storage than the ordinary starch. Among the starches, Quick Sweet starch granules, having the lowest gelatinization temperature, were digested rapidly by pancreatin.     

Structural characterization of rice starch in rice cake modified by Thermus scotoductus 4-alpha-glucanotransferase (TS alpha GTase)

ABSTRACT:  Rice cake was produced with a thermostable 4-α-glucanotransferase from Thermus scotoductus (TSαGTase). Starch molecular fine structure, texture, and retrogradation for the enzymatically prepared rice cake were investigated and compared to those for control rice cake. The amylose content in TSαGTase-treated rice cakes decreased, whereas branched and linear malto-oligosaccharides ranging from maltose to maltoheptaose increased slightly. The average molecular weight of the enzyme-treated rice starch in rice cake decreased as amylopectin macromolecules were cleaved and reorganized into small amylopectin clusters. The number of shorter side chains (degree of polymerization [DP] < 9) increased, whereas the number of longer side chains (DP > 10) decreased through the disproportionation reaction of TSαGTase. After 24 h of storage at 4 °C, the enzyme-treated samples demonstrated significantly lower melting enthalpy of retrograded starch (0.4 mJ/mg) compared to that of the control (1.4 mJ/mg). The results indicated that TSαGTase treatment effectively inhibited starch retrogradation in rice cakes. It is suggested that the reduction of amylose content, the rearrangement of amylopectin, and the production of malto-oligosaccharides caused by TSαGTase treatment are responsible for the ineffective molecular reassociation of rice starch in rice cake.     

Influence of Delayed Harvest Time on Physico‐chemical Properties of Sweetpotato Starch

Eight varieties of sweetpotato [Ipomoea batatas (L.) Lam] were transplanted in June, and harvested in October, November, December 1999 and January 2000. Starch content and starch properties of the tuberous roots were compared on delaying the harvest date. The shoot tops got blighted in early December and chilling injury rate of roots (average of eight varieties) increased up to 76.7% in January with decrease in temperature. Starch contents in October (24.0 g/100 g fresh weight, fw) and November (25.0 g/100 g fw) were almost the same, but the content decreased remarkably in December (21.2 g/100 g fw) and January (15.5 g/100 g fw). In December and January, the sucrose content of the roots had higher values. Hardness and leaked water percentage (LWP) of the starch gels remarkably increased from November to December (hardness: 76.4 to 112.3 g, LWP: 6.6 to 10.9%). On the contrary, the changes in amylose content and pasting properties of the starches were not consistent with decrease in temperature. This suggests that the effect of low temperature on these properties is insignificant after the growth period of sweetpotato. There were significant differences among the varieties in terms of starch retrogradation. The selection of varieties such as Kyushu 123 with the lowest percentage of retrogradation and Kyukei90142‐8 with the lowest chilling injury rate will help to lengthen the storage time in the field at least until December.     

直链淀粉晶种对淀粉回生的影响机制

由于淀粉回生影响因素复杂和研究手段局限,基于直链淀粉主导的短期回生阶段和支链淀粉主导的长期回生阶段关联性的回生共性机制未得到系统阐述。基于此,该研究制备短期回生的直链淀粉晶种,采用FTIR、¹³C CP/MAS NMR等手段,研究其诱导大米淀粉的长期回生过程与规律,揭示短期回生与长期回生关联性。结果表明,所制备的直链淀粉晶种粒度分布在200～450 nm,添加晶种导致淀粉短程有序度由0. 670最高提高至0. 887,双螺旋含量由14. 86%最高提高到了22. 80%。回生淀粉的短程有序度、双螺旋含量显著提高,表明所制备直链淀粉晶种显著促进淀粉长期回生过程,这种晶体协同增长效应,丰富了淀粉回生共性机制。     

酵母菌发酵生淀粉提高马铃薯淀粉回生率机理研究

以马铃薯淀粉为原料,淀粉回生率为考察指标,研究酵母菌发酵对马铃薯淀粉回生率的影响。通过对比发酵前后马铃薯回生淀粉的可见和红外吸收曲线,分析了酵母菌发酵提高马铃薯淀粉回生率的机理。结果表明,纤细酵母菌发酵马铃薯淀粉可使马铃薯淀粉回生率由12%提高到39.4%,提高了2.28倍。发酵后马铃薯回生淀粉中直链淀粉的最大可见吸收波长为587.8 nm,大于发酵前的569.6 nm。酵母菌发酵马铃薯淀粉提高其回生率的原因有两方面:一是发酵过程产生的酶使马铃薯支链淀粉脱支生成直链淀粉,增加了参与回生直链淀粉的量;二是发酵过程使马铃薯淀粉中醛基部分转变为伯醇基,进而生成糖苷键,增加直链淀粉链长,有利于淀粉回生过程晶体长大。     

促进玉米直链淀粉回生的甘薯淀粉晶种的筛选及表征

通过向四次回生的玉米直链淀粉中添加草酸侵蚀的四次回生的甘薯淀粉、甘薯直链和甘薯支链淀粉晶种(质量分数:1%),研究甘薯淀粉晶种对玉米直链淀粉回生的影响。结果表明,甘薯淀粉晶种明显促进了玉米直链淀粉回生长晶,其中甘薯直链淀粉晶种使得玉米直链淀粉回生率达到59.5%,比不添加晶种提高了19.3%。可见吸收光谱研究表明,甘薯淀粉晶种及长晶后的玉米直链淀粉均保持了双螺旋结构。X-射线研究表明草酸侵蚀后甘薯淀粉、甘薯直链淀粉、甘薯支链淀粉均为A+B型。将其分别添加到玉米直链淀粉中并长晶后的样品,结构均为B型。DSC研究表明,甘薯支链淀粉晶种具有最高的吸热焓,说明其晶体含量最高。三种晶种分别促进玉米直链淀粉长晶后的结构较为相似,晶体含量也较相近。该研究为提高淀粉的回生率、研究回生淀粉结晶结构提供良好的技术支持。     

Effect of amylose content and rice type on dynamic viscoelasticity of a composite rice starch gel

Amylose content is an important indicator to determine the utility of raw milled rice. Indica type rice with high amylose content is usually used for manufacturing rice noodles, while Japonica rice may be mixed partially to adjust the noodle texture. The effect of amylose and rice type on dynamic viscoelasticity of rice starch gel was investigated using a model starch composite in this study. The information will be helpful to control and obtain the required noodle texture by combination of different rice types. The results show that nonwaxy Indica and waxy Japonica rice starches in a composite mixture were incompatible and demonstrated their individual gelatinization behavior during heating. High amylose starch showed higher moduli and lower loss tangent values, as well as higher retrogradation rate. The starch gel made from Japonica rice starch showed a slow retrogradation rate even containing a similar amount of amylose to Indica starch. The storage modulus of the gel made from higher amylose rice was shown to be more independent of frequency. Not only amylose content but also chain length distribution in amylopectin affected the dynamic viscoelasticity of rice gel. Japonica rice starch, with fewer super-long chains in amylopectin, retrograded slower after gelatinization than Indica rice, thus the paste is too sticky for production of rice noodles.     

Effect of Starch of Textural Properties of Surimi Gel

The proportion of amylose and amylopectin, and the rheological behavior of eight starches were correlated with the textural properties of starch-containing surimi gels. Findings included the following: increased firmness and cohesiveness with increases in water-holding ability and viscosity of the starch; increased expressible moisture and penetration force with an increase in the amylose fraction due to increased retrogradation: increased tensile force with an increase in the amylopectin fraction: and increased cohesiveness and chewiness after refrigerated storage for all starches with a greater increase for high amylose starches. Surimi gels containing potato starch were the firmest and most cohesive. The textural properties of starch-containing surimi gel correlated well (r = 0.90 to 0.97, P>0.05) with the viscosity of starch paste if 100% amylopectin-containing and pregelatinized starches were excluded from the correlation.     

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP < 14) favoured swelling. Starch pasting behaviour of 5.0 and 8.0% starch suspensions was studied using Rapid Visco Analyser (RVA). For 5.0% suspensions, increased levels of high-MW AP and decreased levels of AM molecules led to higher peak viscosity. Longer AP chains (DP > 18) depressed peak viscosity, while short chains (DP < 14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (ΔH_retro) and peak and conclusion temperatures of retrogradation (T_p,retro and T_c,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature.     

Wheat starch production,structure, functionality and applications—a review

Starch is the main component of wheat having a number of food and industrial applications. Thousands of cultivars/varieties of different wheat types and species differing in starch functionality (thermal, retrogradation, pasting and nutritional properties) are grown throughout the world. These properties are related to starch composition, morphology and structure, which vary with genetics, agronomic and environmental conditions. Starches from soft wheat contain high amounts of surface lipids and proteins and exhibit lower paste viscosity, whereas that from hard cultivars contain high proportion of small granules and amylose content but lower gelatinization temperature and enthalpy. Waxy starches exhibit higher‐percentage crystallinity, gelatinization temperatures, swelling power, paste viscosities and digestibility, but lower‐setback viscosity, rate of retrogradation and levels of starch lipids and proteins than normal and high‐amylose starches. Starches with high levels of lipids are less susceptible towards gelatinization, swelling and retrogradation and are good source of resistant starch, while that with high proportion of long amylopectin chains are more crystalline, gelatinize at high temperatures, increase paste viscosity, retrograde to a greater extent and decrease starch digestibility (high resistant and slowly digestible starch and low rapidly digestible starch).     

The Influences of Chain Length of Amylopectin on Resistant Starch in Rice (Oryza sativa L.)

Amylopectin is the principle component of starch. To elucidate the relationships between amylopectin and resistant starch content, six rice mutants with altered fine structure of amylopectin were selected for comparative studies with the primary wild type and two types of amylose‐extender (ae) mutants. Significant differences in resistant starch content were observed among mutants with similarity or differences in amylose levels. Mutants high in resistant starch had significantly increased proportions of short amylopectin chains with DP≤12, decreased levels of intermediate chains with size of 13≤DP≤36, and decreased fractions of long chains with DP≥37. Additionally, there was a mutant different to ae, which was characterized by an increased level of short chains with 8≤DP≤12 and 13≤DP≤24, and a decreased proportion of long chains with DP≥37. The increased contents of short chains with 8≤DP≤12 and decreased of intermediate and long chains with 24≤DP were clearly associated with the increase of resistant starch in rice.     

Effect of retrogradation,pancreatin digestion and amylose/amylopectin ratio on the fermentation of starch by Clostridium butyricum (NCIMB 7423)

Using three different maize starches (maize, waxy maize and high amylose maize, containing 25%, 1% and 52% amylose, respectively) the influence of amylose/amylopectin content and of retrogradation on fermentation by the porcine caecal anaerobe Clostridium butyricum was assessed. Small intestine digestion was simulated using pancreatin before the starches were exposed to bacterial fermentation. It was found that retrogradation appeared to alter the extent of the fermentation and hence the amount of short-chain fatty acids produced, while pancreatin digestion appeared to alter the way in which the organism fermented the starch and hence the acetate/butyrate ratio. The amylose/amylopectin ratio seemed to have more influence on the way the starch was fermented by the bacteria after the starch had been subjected to digestion with pancreatic enzymes, but had less influence when the starch had been retrograded. © 1998 SCI.     

Structure and physicochemical properties of palmyrah (Borassus flabellifer L.) seed-shoot starch grown in Sri Lanka

Starch from palmyrah (Borassus flabellifer L.) seed-shoot flour was isolated and its composition, morphology, structure and physicochemical properties were determined. The yield of starch was 38.4% on a whole flour basis. The shape of the granule ranged from round to elliptical. Bound lipid, total lipid, apparent amylose, total amylose and resistant starch contents were 0.03%, 0.04%, 30.9%, 32.7% and 32.2%, respectively. The X-ray pattern was of the A-type and relative crystallinity was 34.1%. Palmyrah starch exhibited a high proportion (31.8%) of short amylopectin chains (DP 6–12) and a low proportion (1.2%) of long amylopectin chains (DP > 36). Gelatinization temperatures were 73.1–82.0 °C and enthalpy of gelatinization was 13.6 J/g. Pasting temperature, viscosity breakdown and set-back were 76.5 °C, 147 and 74 BU, respectively. Palmyrah starch exhibited high granular swelling, and restricted amylose leaching. Susceptibility towards in vitro α-amylolysis and retrogradation was low. The results showed that physicochemical properties of palmyrah starch were largely influenced by strong interactions between amylose–amylose and/or amylose–amylopectin chains within the granule interior.     

Retrogradation of sweet potato amylose and amylopectin with narrow molecular weight distribution

Retrogradation of sweet potato amylose and amylopectin with narrow molecular weight distribution at different temperatures was investigated by X-ray diffraction (XRD). Atomic force microscope (AFM), scanning electron microscope (SEM) and light microscopy were combined to study the morphology of the molecular assemblies during retrogradation. Avrami equation was used to the retrogradation kinetics the of above starches by determining the crystallinity and the ratio of peak area of two distinctive peaks. It was found that only the ratio of peak area/total area at 2θ = ~16.3° could represent the crystallinity of retrograded starch-containing amorphous regions. Considering the crystallinity as retrogradation rate, only the retrogradation kinetics of sweet potato amylose could be analysed by Avrami equation, but not the amylopectin’s. All Avrami exponents n of amyloses at any temperatures were less than 1.0, indicating instantaneous nucleation and rod-like growth. AFM results showed that the maximum heights of layered structure for sweet potato amylose, amylopectin and blending of both were approximately 4800, 180 and 200 nm, respectively. The height of the former two decreased during storage, but the height of blending remained unchanged. Amylose served as nuclei of amylopectin during starch retrogradation.     

Physicochemical Properties and Food Uses of Starch from the New Sweetpotato Cultivar Konamizuki

Starch from the new sweetpotato cultivar Konamizuki (KM) was evaluated as a food material, and its basic properties were characterized. Change in elastic modulus during cold storage of KM starch gels and syneresis after freeze-thaw treatment were limited and indicated slow retrogradation properties. In addition, KM starch paste had higher and more stable storage modulus than other starches, suggesting desirable gel-forming properties. These KM gel properties reflected distinctive structural properties, including larger quantities of short unit chains with degree of polymerization 6-10 and amylose-like long chains of the amylopectin, as well as longer amyloses and longer amylose-like chains of the amylopectin compared with other starches. Finally, KM starch was used in the production of tapioca pearls and starchy noodles, and subsequent sensory analyses indicated highly desirable properties as a food material for starchy gel products.     

Chain‐length Distribution Profiles of Amylopectin Isolated from Endosperm Starch of Waxy and Low‐amylose Bread Wheat (Triticum aestivum L.) Lines with Common Genetic Background

Large A‐type endosperm starch granules were isolated from near‐isogenic waxy and non‐waxy lines and low‐amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A‐type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λ_max (range: 532‐538 nm) and blue values at 680 nm (range: 0.026‐0.037) of the iodine‐amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non‐waxy and low‐amylose lines did not contain such long chains as amylose or extra‐long chains of amylopectin affecting iodine complex properties. Chain‐length distribution profiles measured by both high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography (HPAEC) showed that the amylopectin structures of these lines were indistinguishable from each other. Extra‐long chains were not detected in the amylopectins by HPSEC measurement. The side‐chains measured by HPAEC were classified into four groups according to their degree of polymerization (DP), and the proportion of each group were in the following ranges: DP 6‐12, 26.5‐27.5%; DP 13‐24, 43.6‐44.1%; DP 25‐36, 13.6‐14.2%, and DP 37‐60, 11.0‐11.7%. The alleles on the Wx‐D1 locus, i.e., Wx‐D1a, Wx‐D1d, Wx‐D1f, and Wx‐D1g, responsible for granule‐bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine‐amylopectin complex and the chain‐length distribution profiles of amylopectin.     

芋头淀粉的分离和纯化

用重结晶法可以得到纯度较高的芋头直链淀粉和支链淀粉。直、支链淀粉的蓝值分别是1 1 8和 0 2 0 ,λmax分别为 61 4nm和 5 87nm ,芋头淀粉中直链淀粉含量为 1 4 7%。高效液相色谱表明 ,芋头支链淀粉的分子质量具有较宽的分布 ;重均聚合度 ,大米支链淀粉 >芋头直链淀粉 >大米直链淀粉 >芋头支链淀粉 ;分散度 ,芋头支链淀粉 >芋头直链淀粉 >大米直链淀粉 >大米支链淀粉 ;芋头支链淀粉中 ,长支链所占比例 >短支链 ;分散度 ,长支链 >短支链。     

A Study of Annealing and Freeze‐Thaw Stability of Acid‐Modified Tapioca Starches by Differential Scanning Calorimetry (DSC)

Tapioca starch was partially hydrolyzed by 6% (w/v) hydrochloric acid at room temperature for various lengths of time. Annealing and freeze‐thaw stability of the acid‐modified starches were studied using Differential Scanning Calorimetry (DSC). In the annealing study, as the hydrolysis time increased, the effect of annealing on narrowing and shifting the endothermic peak to a higher temperature was decreased. The endothermic transition of annealed 48‐h acid‐modified tapioca starch showed a narrow peak and a broad shoulder, corresponding to the melting of the amylopectin double helices (crystalline regions) and the retrograded partially hydrolyzed amylose, respectively. This effect of annealing on the sharpening of the endotherm was less pronounced on acid‐modified tapioca starches annealed for 192 h and 768 h, respectively. These results indicated that annealing leads to more homogeneous crystallites and this effect is enhanced when the material contains more amorphous and homogeneous domains. In the case of the freeze‐thaw stability study, the melting endotherm of recrystallized amylopectin became larger with increasing hydrolysis time. The first detectable endotherm of native tapioca retrograded gel was observed after five cycles, while all acid‐modified retrograded gels showed the melting endotherm after only one cycle. Increasing hydrolysis time may increase the proportion of short chain amylose and amylopectin molecules, which are able to form double helices, resulting in an increase in the enthalpy and a higher retrogradation rate of the gel.