Retrogradation of Sweetpotato Starch

Hardness and the percentage of leaked water of sweetpotato starch gels after storage were investigated as indexes of starch retrogradation. Starches of some varieties of sweetpotato were retrograded rapidly, but those of others were not retrograded during storage for one week. After one month of storage, starches of all varieties were highly retrograded, but the varietal order of hardness and the percentage of leaked water were almost the same as that after storage for one week. The study of chain length distribution by gel permeation chromatography after debranching by isoamylase showed that the hardness and the percentage of leaked water from the gel were positively correlated with amylose content and the proportion of Fr 1, the fraction of the highest molecular weight, containing amylose and extremely long chains of amylopectin, and negatively correlated with the proportion of Fr 3, the fraction with the lowest molecular weight, containing shorter chains of amylopectin. In addition, it was demonstrated by high performance anion exchange chromatography that the proportion of extra‐short chains (around DP 10) of amylopectin after isoamylase treatment was negatively correlated with the retrogradation index of starch. These results suggest that retrogradation of sweetpotato starch was promoted by amylose and extremely long chains of amylopectin and was inhibited by extra‐short chains (around DP 10) of amylopectin.     

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.     

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.     

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.     

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.     

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.     

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).     

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。     

Starch retrogradation

Abstract

Starch granules heated in excess water undergo an order‐disorder phase transition called gelatinization (1) over a temperature range characteristic of the starch source. This phase transition is a non‐equilibrium process associated with the diffusion of water into the granule, hydration and swelling of the starch granules, uptake of heat, loss of crystallinity, and amylose leaching (1–3). On cooling, the starch chains (amylose and amylopectin) in the gelatinized paste associate, leading to the formation of a more ordered structure. These molecular interactions are termed collectively “retrogradation” and have important textural and dietary implications (not covered in this review). This review summarizes the present knowledge on amylose gelation and amylopectin crystallization, and on the factors that influence starch retrogradation.     

Effect of Environmental Temperature During Development of Rice Plants on Some Properties of Endosperm Starch

Starch granules were isolated from polished grains of rice plants (Oriza sativa L.) grown under controlled temperature conditions. Distribution of isoamylase-debranched starch materials and unit chain-length of amylopectin were examined by gel-filtration on columns. Higher environment temperature decreases amylose concentration in endosperm starches of Japanese rice cultivars. The amylose concentration in the endosperm starch is determined by the environment temperature 5 – 15 days after heading. Interestingly, the higher environment temperature seemed to increase the amount of long B chains and decrease that of short chains of amylopectin. The effect of environment temperature on pasting characteristics of starch by DSC, starch-granule digestibility by amylases and X-ray diffractograms of starch was also investigated.     

Effect of Gamma Irradiation on Molecular Structure and Physicochemical Properties of Corn Starch

ABSTRACT:  Carboxyl content and amylose leaching of gamma-irradiated corn starch increased and swelling factor decreased with increasing radiation dose. The apparent amylose content decreased gradually from 28.7% for native starch to 20.9% for 50 kGy irradiated starch. The proportion of short amylopectin branch chains (DP 6 to 12) increased, while the proportion of longer branch chains (DP ≥ 37) decreased with increasing radiation dose. The relative crystallinity and the degree of granule surface order decreased from 28.5% and 0.631 in native starch to 26.9% and 0.605 in 50 kGy irradiated starch, respectively. Pasting viscosity and gelatinization temperatures decreased with an increase in radiation dose. At a high dose (50 kGy), melting of amylose–lipid complex in DSC thermogram was not observed. The rapidly digestible starch (RDS) content slightly decreased up to 10 kGy but increased at 50 kGy. The resistant starch (RS) content slightly decreased at 2 kGy and then increased up to 50 kGy. The slowly digestible starch (SDS) content showed the opposite trend to RS content. Slower irradiation dose rate reduced carboxyl content, swelling factor, and amylose leaching. The apparent amylose content and amylopectin chain length distribution were not significantly affected by dose rate of gamma irradiation. However, the relative crystallinity and gelatinization enthalpy increased with slower dose rate. Slower dose rate decreased RDS and SDS contents, and increased RS content.     

Structural modification and characterization of rice starch treated by Thermus aquaticus 4-α-glucanotransferase

Rice starch was modified using Thermus aquaticus 4-α-glucanotransferase (TAαGTase) in this study. The changes in the molecular structure and the effect on the starch retrogradation by TAαGTase treatment were investigated on isolated rice starch. By treating TAαGTase, molecular weight profile of amylopectins shifted to higher elution time from 1.0 × 10⁸ to 2.4 × 10⁷ or 0.8 × 10⁷, depending on the level of enzyme dosage. Meanwhile, there were huge increases in the proportions of content corresponding to amylose size and even smaller molecules. On treating with TAαGTase, short branch chains (DP 1–8) increased, and longer branch chains (>DP 19) increased significantly as well, with a broader distribution up to DP 46 compared to the control rice starch. Amylose content decreased from 30.0 to 21.8–23.7%. This indicated that the amylose could be transferred to the amylopectin branch chain by the disproportionation of TAαGTase, resulting in lowering the amylose content and the formation of amylopectin with a broader branch-chain length distribution. TAαGTase modified rice starch showed that X-ray diffraction pattern of the B-type crystalline even before cold storage, and that a variety of cyclic glucans (DP 5–19) were produced by enzymatic reaction. In particular, the accelerated rate of starch retrogradation was clearly observed compared to the control due to an overall increase in the number of elongated long-branch chains, decrease in the amount of amylose–lipid complex, and the possible synergistic effects of these factors.     

Comparison of Starch Physicochemical Properties from Medium‐Grain Rice Cultivars Grown in California and Arkansas

The starch molecular structure and physicochemical properties of two medium‐grain rice cultivars from Arkansas (Bengal, Medark) and from California (M202, M204) were determined and compared when they were grown in their respective locations and grown together in Arkansas to better understand the impacts of genetics and environment on starch characteristics. Both M202 and M204 contained significantly higher amylose contents (13.2‐15.3%) compared with the Arkansas cultivars (11.6‐12.4%). Starch from the Arkansas rice cultivars exhibited higher pasting and gelatinization temperatures and higher enthalpy values. Rice amylopectin from the California cultivars consisted of a smaller proportion of intermediate chains (DP 13‐24), and had a lower molecular weight and a smaller radius of gyration. When the four cultivars were grown together in Arkansas, the ranges for amylose content narrowed (10.6‐12.4%), their differences in thermal and pasting properties became smaller, and the molecular characteristics of amylose and amylopectin changed for all four cultivars. This study demonstrated that genetics, location, and crop year all contributed to variations in rice starch fine structure and physicochemical properties.     

6种不同种类直支链淀粉相互混合对其回生的影响

目的 研究6种不同种类直支链淀粉相互混合对其回生的影响。方法 将玉米淀粉、甘薯淀粉、木薯淀粉、马铃薯淀粉、糯米淀粉、小麦淀粉等6种不同种类直支链淀粉分离出来, 然后两两混合, 研究不同直支链混合对其回生率的影响。 结果 马铃薯支链淀粉与甘薯支链淀粉以2:8(m:m)混合回生率最低, 为60.0%, 玉米支链淀粉与木薯支链淀粉以8:2(m:m)混合回生率最低为52.6%, 小麦支链淀粉与糯米支链淀粉以8:2(m:m)混合回生率最低为51.2%, 甘薯支链淀粉与小麦支链淀粉以1:1(m:m)混合回生率最低为53.7%。木薯支链淀粉与小麦直链淀粉以1:1(m:m)混合时所得淀粉回生率最大, 达到了92.0%, 混合淀粉回生后X射线晶型为B型。结论 不同种类直支链淀粉混合对其回生率影响很大, 食品加工中尽量不要混合使用木薯支链淀粉与小麦直链淀粉。     

原花青素抑制玉米淀粉回生作用的研究

目的研究原花青素(OPCs)对高直链玉米淀粉、普通玉米淀粉和高支链玉米淀粉回生的影响。方法采用差示扫描量热仪(DSC)、傅立叶红外光谱仪(FTIR)、核磁共振光谱仪(NMR)测定与分析原花青素与淀粉间的相互作用;同时测定原花青素对淀粉体外消化性的影响。结果结果表明,随着OPCs含量的增加,高直链玉米淀粉回生程度降低;当OPCs添加量为5%时,原花青素对普通玉米淀粉和高支链玉米淀粉回生抑制效果较好。高直链玉米淀粉中慢消化淀粉(SDS)含量随OPCs增加而增加,普通淀粉中SDS含量在添加5%OPCs时较高,而高支链玉米淀粉的快消化淀粉(RDS)含量在5%时较高;NMR结果表明OPCs分子与直链和支链淀粉之间均存在分子间相互作用。结论添加5%原花青素对三种玉米淀粉回生抑制效果较好;原花青素对直链和支链淀粉的结合方式和结合能力不同。     

The Effect of Environmental Temperature on Distribution of Unit Chains of Rice Amylopectin

The effects of environmental temperature during the early development of seeds on the structural characteristics of the endosperm starch were investigated using near‐isogenic lines of rice plants (Taichung 65, waxy), grown under temperature controlled conditions. High performance gel permeation chromatography (HPLC) demonstrated that Pseudomonas isoamylase‐debranched amylopectins of rice plants grown at lower temperature (25°C) contain increased amounts of short chains and decreased amounts of long chains as compared with amylopectins obtained from rice plants grown at higher temperature (30°C). By high performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) of isoamylase‐debranched amylopectins it was detected that the amount of unit chains with degree of polymerization (DP) 6 and 11‐13, in the amylopectin of rice plants grown at lower temperature (25°C) had significantly increased and the amount of unit chains with DP 8, 22‐24 and 29 had significantly decreased, as compared with the amylopectin of rice plants grown at higher temperature (30°C). It was confirmed that the environmental temperature between 5 and 10 d after pollination strongly influenced the structure characteristics of the endosperm starch of rice plants.     

Molecular Structure of Starches from Cassava Varieties having Different Cooked Root Textures

Starches from 12 cassava varieties with different cooked root texture; i.e. mealy, firm and mealy and firm, were investigated with a particular focus on aspects of molecular structures of amylose and amylopectin. Structural elements of amylopectin were essentially constant in terms of unit chain distributions and chain lengths. All cassava amylopectins displayed two distinct chain length peaks, at DP 40–46 and at DP 11–13, with a shoulder at DP 17–19, and average chain length (CL) of amylopectins was 17–20. A fraction of extra‐long chains in the range of 0.24–1.78% was found. Amylose and amylopectin from four varieties with different textures of cooked root were isolated. Data from C‐chain distributions indicated that the molecular size of amylopectin from M‐hanatee (Hanatee), a locally adapted cassava variety, was 2.5–2.9 times smaller than those of the other varieties. Three of the four amylose samples, except that from M‐hanatee, were very similar in average DP (4120–4390), chain length (530–550) and number of chains (7.1–7.5), and composed of nearly equal numbers of linear and branched molecules. The amylose from the M‐hanatee variety showed a unique characteristic: it had smaller size (2050), shorter chain length (450), fewer chains (4.7) and a higher content of linear fraction (58%), when compared with other amyloses.     

Functional Properties and Retrogradation of Heat‐Moisture Treated Wheat and Potato Starches in the Presence of Hydroxypropyl β‐cyclodextrin

Some functional and retrogradation properties of native and heat‐moisture treated potato and wheat starches were examined in the presence of hydroxypropyl β‐cyclodextrin (HPβ‐CD). HPβ‐CD increased swelling factor, amylose leaching, and solubility of both native and heat‐moisture treated wheat starches but it had less impact on corresponding potato starches. Gelatinization enthalpy of native wheat starch was decreased in the presence of HPβ‐CD but was increased in potato starch with increasing concentration. Reduction of amylose‐lipid complex endotherm in both native and heat‐moisture treated wheat starch was observed in the presence of HPβ‐CD. Heat‐moisture treatment did not change the transition parameters of amylose‐lipid complex showing its resistance to hydrothermal treatment. HPβ‐CD greatly decreased the pasting temperature of wheat starch. Cold paste viscosity of both native and heat‐moisture treated wheat starch was increased by HPβ‐CD to a greater extent than corresponding potato starch. Amylopectin retrogradation of all the starches was unaffected in the presence of HPβ‐CD but heat‐moisture treatment slightly decreased retrogradation of potato starch. These results suggest that HPβ‐CD can disrupt the amylose‐lipid complex within the starch granule in both native and heat‐moisture treated wheat starch but has no influence on amylopectin retrogradation. However, greatly increased wheat starch setback with HPβ‐CD indicates its greater effect on wheat starch amylose retrogradation.     

Retrogradation of Potato Starch as Studied by Fourier Transform Infrared Spectroscopy

Retrogradation kinetics for a potato starch-water system (10% w/w gel) was monitored by Fourier Transform Infrared spectroscopy and compared with waxy maize starch. The spectra showed the C-C and C-O stretching region (1300-800 cm⁻¹) to be sensitive to the retrogradation process. A multi-stage process was observed during the retrogradation of potato starch and characterized as the formation of short- and long-range order. The first stage was characterized as the formation of helices and the fast formation of crystalline amylose regions. The second stage was described as the induction time for amylopectin helix aggregation. Stage three was described as the helix-helix aggregation and the crystallization of amylopectin. The overall-first order calculated rate constant of potato starch was (9.6±1.4) 10⁻ 3h⁻¹. The calculated rate constant were in agreement with the known difference in retrogradation kinetics of waxy maize and potato starch. The effects were explained by the differences in retrogradation rate of amylopectin and amylose. Potato starch consists of amylose as well as amylopectin. Whereas amylose crystallization occurs within a few hours, amylopectin crystallization is slow and takes a few weeks.     

挤压对糙米中淀粉理化性质的影响

本文研究了挤压对糙米淀粉糊化和热力学性质、结晶结构、支链淀粉分支链长等的影响。结果表明,挤压处理使糙米淀粉的峰值粘度、回生值和热焓值分别由1811 cP、1677 cP和9.41 J/g降低至107 cP、53 cP和0.97 J/g,淀粉发生糊化。糙米淀粉X-射线衍射峰的强度和位置在挤压后均发生变化,淀粉结晶结构由A型转变为V型,相对结晶度由31.33%降至20.95%。傅立叶变换红外光谱图中1047 cm-1/1022 cm-1的比率由挤压前的0.811下降为挤压后的0.732,表明挤压使淀粉结晶区比例降低。同时,挤压后淀粉-碘复合物吸收光谱强度增加,说明挤压使直链淀粉比例增加。阴离子交换色谱结果显示,挤压后支链淀粉A链（DP6-12）比例增加,B1链（DP13-24）和B2链（DP25-36）比例减少,证明支链淀粉发生降解。此外,扫描电子显微镜结果表明,挤压产物中淀粉颗粒变大,淀粉表面变得粗糙且有褶皱和裂痕。