韧化处理对不同玉米淀粉理化特性的影响

以不同直/支链比例的普通玉米淀粉和蜡质玉米淀粉为材料,在40、50、60℃进行韧化处理,研究韧化处理对玉米淀粉理化特性的影响。结果表明：韧化处理的两种玉米淀粉颗粒形貌有较小变化。韧化处理后,两种淀粉的溶解度和膨胀度随着处理温度的升高而降低;所有韧化处理过的玉米淀粉黏度低于原淀粉,起糊温度高于原淀粉;韧化处理后淀粉的糊化温度升高,热焓变化不大。     

Effects of cross-linking and low molecular amylose on pasting characteristics of waxy corn starch

The action of amylose within the granule of normal corn starch is investigated by changes in pasting characteristics of waxy corn starch in a Rapid Visco Analyzer (RVA), using addition of soluble amylose (DP = 18) and cross-linking with epichlorohydrin. Although waxy corn starch, containing no amylose, did not show an effect of addition of amylose on pasting characteristics, by cross-linking with epichlorohydrin, the pasting peak viscosity and breakdown were greatly enhanced and set-back (viscosity increased in the cooling process after gelatinization) was generated. The cross-linking depressed the disintegration of starch granules in the swelling process, with amylose interaction, resulting in RVA pasting characteristics similar to those seen with normal corn starch containing amylose. Set-back was essentially caused by rearrangement among modified amylopectins. Addition of sodium dodecyl sulfate (SDS) to the RVA more efficiently enhanced the effect. This indicated that amylose in normal corn starch interacts with amylopectin through locally strong linkages.     

Amylose Content and Chain Profile of Amylopectin from Normal,High Amylose and Waxy Barleys

The amylose content and the chain profile of amylopectin from normal, waxy and high amylose barley starches were determined after enzymatic debranching and gel permeation chromatography and the degree of branching of the amylopectin was analysed by 1H-n.m.r. spectroscopy. The normal barley starch contained around 30%, the high amylose around 40% and the waxy starch 9% amylose. The amylopectin of the high amylose starches had longer chains than those of the normal or waxy starches, especially in the molecular weight interval 5,400-8,000, but less of those below 2,400 in molecular weight. The chain length of amylopectin from high amylose barley was on average 5 units longer than those of normal or waxy barleys.     

The Fine Structure of Corn Starches of Various Amylose-Percentage: Waxy,Normal and Amylomaize

The fine structure of high-amylose corn starches has been studied after dispersion of the starch and fractionation into their components amylose and amylopectin. The resulting amylopectin fraction reported in the literature possesses anomalous properties with regard to the waxy and normal amylopectin. However, the experimental results obtained by different authors for determining the structure lead to controversal explanations. Therefore, using an enzymic method, which permits the direct examination of the constitutive chains of the starch, the fine structure of the amylopectin of an amylomaize starch (64% amylose) has been investigated and compared with those of waxy and normal starches. The pullulanase – debranched chains are fractionated by gel permeation and their linearity are checked under the action of β-amylase. The inner chains of the amylopectin fraction are studied after debranching of the β-limit dextrins. The results show the identity between amylopectins from waxy and normal starches. The amylopectin fraction of amylomaize has its own structure with longer inner chains than those of waxy-maize amylopectin.     

Localisation of Amylose and Amylopectin in Starch Granules Using Enzyme-Gold Labelling

The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.     

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.     

Amylopectin structure of heat–moisture treated starches

The effects of heat–moisture treatment (HMT; moisture content of 25%, at 100°C for 24 h) on starch chain distribution and unit chain distribution of amylopectin in normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starches were investigated. After HMT, starch chain distribution (amylose and amylopectin responses) of waxy corn and potato starches were identical to those of untreated starches, whereas the chromatographic response of waxy rice starch showed a slight decrease, but with a slight increase in peak tailing. This result indicated that HMT had no (or very limited) effect on the degradation of amylopectins. Analysis of unit chain distribution of amylopectins revealed that waxy characteristics affected the molecular structure of amylopectin in untreated starches, i.e., the CL of normal‐type starches was greater than that of waxy‐type starches. After HMT, the CL and unit chain distribution of all starches were no different than those of untreated starches. The results implied that changes in the physico‐chemical properties of HMT starches would be due to other phenomena rather than the degradation of amylopectin molecular structure. However, the thermal degradation of amylopectin molecules of waxy starches could occur by HMT at higher treatment temperatures (120 and 140°C).     

Solubility Behavior of Granular Corn Starches in Methyl Sulfoxide (DMSO) as Measured by High Performance Size Exclusion Chromatography

The extent of corn starch dispersibility and the relative molecular solubility of amylose and amylopectin in methyl sulfoxide (DMSO) were determined. Granular corn starches with <l, 25, 53, and 70% amylose were dispersed in 0–100% DMSO (in water) solutions at 30°C for 30 min. Maximum dispersibility for all starches (98%) was obtained when 90% DMSO/10% water was used; regular (normal) dent corn starch was equally dispersed in solutions with 88–94% DMSO. Molecular solubility, the presence of individual molecules of amylose and amylopectin, of starches was also measured (after centrifugation and filtration) by high performance size-exclusion chromatography (HPSEC). Starches were dispersed in 90% DMSO and heated for 10 min at temperatures of 35–120ºC. At low temperatures, high coefficients of variation resulted from additional DMSO solubilization after treatment. At 120ºC, 70% amylose starch was >90% solubilized, while waxy starch was only 47% solubilized. When starches were treated for 18–89 h in 90ºC DMSO, solubility stopped increasing after 67 h. High amylose starch (70%) was mostly solubilized, but 53% amylose, waxy and regular starches could only be fully solubilized after exposure to shear. Amylopectin molecules appeared more susceptible to shear induced depolymerization than amylose. The percent amylopectin in the high amylose starches reflected that as determined by iodine binding analysis and the manufacturer; while the percent amylopectin in regular starch was too low (manufacturers: 75%, HPSEC: 65%). Undispersed components were mostly amylopectin. Since amylose is fully solubilized, however, the HPSEC can be used to quickly determine percent amylose in starch.     

酸解对不同链/支比含量玉米淀粉特性的影响

以4种不同链/支比含量的玉米淀粉为原料,酸解处理不同时间,以酸解玉米淀粉的形貌特性、冻融稳定性、膨胀度、溶解度、晶体性质为指标衡量不同酸解时间对玉米淀粉结构性质的影响。结果表明:4种玉米淀粉酸水解程度的顺序为:蜡质玉米普通玉米淀粉G50G80。酸解后,同品种的4种玉米淀粉的析水率随着酸解天数的增加而增加;溶解度增加,膨胀度降低。酸解并未改变淀粉的晶型,随着酸解时间的延长,蜡质玉米淀粉和普通玉米的相对结晶度先增大后保持不变,G50和G80的相对结晶度随着酸解时间的增加而增大。表明酸解对低直链淀粉(蜡质玉米淀粉和普通玉米淀粉)的结构、性能影响最大。     

Stufenweise Elutionsanalyse der Fraktionen von thermisch dispergierter Amylose-, Kartoffel- und Wachsmaisstärke

Stepwise Elution Analysis of Fractions of Thermically Dispersed High Amylose, Potato and Waxy Corn Starch. Changes in the starch constituents - the amylose and the amylopectin — from dispersions of high amylose, potato- and waxy corn starch were studied by stepwise elution analysis and determination of molecular weight. The dispersions were prepared by dispersing the pastes 1 and 3 h at 120 °C and the amyloses and amylopectins separated by means of n-butanol and methanol, resp. With the exeption of a partial separation in waxy corn starch no separation of pastes into amylose and amylopectin could be observed, probably due to the mild pasting conditions in the Brabender Viscograph. By stepwise elution analysis it could be stated that after prolonged thermic dispersing of the pastes of high amylose starch the amylose and amylopectin do no longer change, which is in good agreement with the values of molecular weight. By analogous treatment of the pastes of potato starch, however, a decomposition of amylose and amylopectin could be stated. In the dispersions of waxy corn starch the amylose molecules decompose to a degree whereafter thermic dispersing of 3 h practically no complex with n-butanol could be observed. Relatively great losses were stated at the isolation of the precipitated constituents. It was stated that the isolated amyloses of potato starch are suitable substrates for activity measurements of α-amylase in human serum and urine as well as in other biologic materials.     

Water Binding Capacity of Commercial Produced Native and Modified Starches

The water binding capacities of five cereal and three tuberous starches, as well as fourteen modified wheat starches were determined using a Differential Scanning Calorimetry technique. Of the native starches, the tuberous ones had the highest moisture binding capacities. The influence of amylose/amylopectin ratio on water binding capacity was examined using waxy maize, normal maize and high amylose maize starches and increases in amylose level were found to result in reduced water binding. Chemical modification caused a reduction in the water binding capacity of wheat starch presumably as a result of blocking water binding sites on the starch molecules. Pregelatinized wheat starch showed a higher water binding capacity than wheat starch as a consequence of the disruption of the internal structure of the granule.     

Molecular Fractionation of Starch in Nycodenz‐Dimethyl Sulfoxide by Density‐Gradient Ultracentrifugation

Starches from various origins (normal corn, waxy corn, high‐amylose corn, normal rice, waxy rice, potato and tapioca) were fractionated by density‐gradient ultracentrifugation at 124,000×g, using a gradient of Nycodenz (0–40%, w/w) in 90% dimethyl sulfoxide (DMSO). The fractions of different densities were collected from a centrifuge tube, and then analyzed by the phenol‐sulfuric acid method and iodine‐binding test. Amylose and amylopectin were clearly separated by the density‐gradient centrifugation within 6 h of centrifugation in the total carbohydrate vs. density profile. The amylose content in the starches, measured from the centrifugation for 6 h, agreed with the values reported in the literature, and the content of intermediate fraction (5–13%) was also measured. Amylopectin quickly reached a density region (1.22–1.23 g/mL) with a sharp and stable peak, whereas amylose showed a band in a broad density range, moving toward higher density as the centrifugation continued. The buoyant density of amylose became similar to that of amylopectin after extensive centrifugation. Because the sedimentation rate of amylose was much lower than that of amylopectin, both starch chains are effectively fractionated in the gradient medium, and the iodine‐binding property of the fractionated starches provides valuable information on the chain conformation of starch.     

Chemical composition,digestibility and emulsification properties of octenyl succinic esters of various starches

Octenyl succinate starches are commonly used as emulsifiers and texturizing agents in many food-systems. Rice, tapioca, corn, wheat and potato starches were modified with octenyl succinic anhydride (OSA) at 3% level. Structural characterization, molecular weight, starch digestibility and physical properties of starch granule stabilized emulsions were studied for modified starches. Modified potato (0.022) and wheat (0.018) starches had the highest and lowest degrees of OSA substitution, respectively. For all starches, amylose and amylopectin molecular mass was significantly (P < 0.05) lower for OSA starches. OSA modification may have hydrolyzed the small amylose and amylopectin chains, or caused rearrangement of the starch molecules. Although the starch modification improved emulsification properties, botanical source showed more influence on this parameter. Overall, botanical source had more influence on functional properties than degree of substitution. Further studies on OSA group distribution and fine molecular structure of amylopectin and relationship with functional properties will be important.     

Effect of annealing on the functionality of Bambara groundnut (Vigna subterranea) starch–palmitic acid complex

Bambara groundnut is an underutilised African leguminous crop. This study investigated the effect of annealing on the complexing ability and functionality of Bambara groundnut starch with palmitic acid. Corn starch was included as the reference. Annealing created cracks and pores on the surface of Bambara groundnut and corn starches, respectively. Bambara groundnut starch had significantly higher amylose content, higher peak and final viscosities than corn starch. The peak viscosities of native Bambara groundnut and corn starches significantly reduced with palmitic acid addition. Greater reduction in peak viscosities was observed when the annealed starches were complexed with palmitic acid, suggesting that more palmitic acid was complexed after annealing. This was confirmed by XRD peaks and melting enthalpies. Pasting of native Bambara groundnut and corn starches with palmitic acid resulted in the formation of type I V‐amylose complexes, while type II complexes were formed from annealed starches pasted with palmitic acid.     

湿热处理对蜡质玉米淀粉性质及羧甲基反应活性的影响

本实验研究了湿热处理对蜡质玉米淀粉性质及羧甲基反应活性的影响.结果表明,经湿热处理后,蜡质玉米淀粉的颗粒形貌基本没发生变化,偏光十字未消失,但表面出现了一些裂纹:湿热处理没能改变蜡质玉米淀粉的晶型,但晶体结构变强,糊化温度升高,糊黏度降低.经湿热处理后淀粉中直链淀粉含量增加,羧甲基反应活性降低.     

3种玉米淀粉的性质比较

研究了高直链玉米淀粉、糯玉米淀粉、普通玉米淀粉的粒度分布、糊流变、质构、冻融稳定性等物理化学性质,结果表明:3种玉米淀粉的颗粒形状差异不大。高直链玉米淀粉的粒度分布一致性较高,同样条件下糯玉米淀粉糊粘度大于其他2种淀粉,糯玉米淀粉的冻融稳定性大于普通玉米淀粉和高直链玉米淀粉,为玉米淀粉在食品中的应用奠定了基础。     

Modification of granular corn starch with 4-alpha-glucanotransferase from Thermotoga maritima: effects on structural and physical properties

ABSTRACT:  Corn starch was converted using α-1,4-glucanotransferase from Thermotoga maritima (TmαGT), a hyperthermophilic bacterium, without inducing gelatinization, and the structural changes and physical properties of the modified starches were investigated. Enzyme modification was induced at 65 °C for 8, 16, or 24 h, and the morphology of the modified starches was observed with light and scanning electron microscopy. Granule integrity was mostly maintained after enzyme treatment, although some granules were partially fragmented as evidenced by enlarged surface pores and some cracks. The modified starches had lower apparent amylose levels than raw starch. The molecular weights of amylose and amylopectin molecules in the treated starches were lower than those of raw starch, and the amount of branched molecules, which had much lower molecular weights, also increased in the treated starches. The chain-length distribution of amylopectin showed an increased number of shorter branched chains. The modified starches showed a wider melting temperature range and a lower melting enthalpy than that of raw starch. The X-ray diffraction pattern of the modified starches showed typical A-type starch peaks, but the relative crystallinities were lower than that of raw starch. The solubility and paste clarity of the modified starches were much higher than those of raw starch. The modified starch gels maintained their rigidity over the whole frequency range tested and showed thermoreversibility between 4 and 75 °C. These results suggest that TmαGT can be used to produce granular corn starch, which contains amylose and amylopectin having lower molecular weights and a thermoreversible gelation property.     

Effect of cooking time and ingredients on the performance of different starches in white sauces

The effect of white sauce ingredients and increased cooking time at 90 °C on the degree of gelatinization of corn, waxy corn, rice, potato and modified waxy corn starches was studied. The changes in pasting properties, linear viscoelastic properties, and microstructure were determined. In all the native starches in water, a longer cooking time at 90 °C caused greater starch granule swelling and more leaching of solubilized starch polymers into the intergranular space. These effects were more noticeable in the waxy corn and potato starches. The potato starch was the most affected, with complete disruption of the starch granules after 300 s at 90 °C. The microstructural changes which transformed a system characterized by starch granules dispersed in a continuous phase (amylose/amylopectin matrix) into a system with an increase in the continuous phase and a decrease in starch granules were associated with a decrease in system viscoelasticity. The elastic moduli were higher in the sauce than in the starch in water system. However, with the exception of potato starch, the white sauce showed lower viscoelasticity than the starch in water system. The white sauce ingredients decreased the effect of cooking time on the starch gelatinization process, particularly in potato starch.     

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

Starches from normal rice (21.72% amylose), waxy rice (1.64% amylose), normal corn (25.19% amylose), waxy corn (2.06% amylose), normal potato (28.97% amylose) and waxy potato (3.92% amylose) were heat-treated at 100 °C for 16 h at a moisture content of 25%. The effect of heat-moisture treatment (HMT) on morphology, structure, and physicochemical properties of those starches was investigated. The HMT did not change the size, shape, and surface characteristics of corn and potato starch granules, while surface change/partial gelatinization was found on the granules of rice starches. The X-ray diffraction pattern of normal and waxy potato starches was shifted from B- to C-type by HMT. The crystallinity of the starch samples, except waxy potato starch decreased on HMT. The viscosity profiles changed significantly with HMT. The treated starches, except the waxy potato starch, had higher pasting temperature and lower viscosity. The differences in viscosity values before and after HMT were more pronounced in normal starches than in waxy starches, whereas changes in the pasting temperature showed the reverse (waxy > normal). Shifts of the gelatinization temperature to higher values and gelatinization enthalpy to lower values as well as biphasic endotherms were found in treated starches. HMT increased enzyme digestibility of treated starches (except waxy corn starch); i.e., rapidly and slowly digestible starches increased, but resistant starch decreased. Although there was no absolute consistency on the data obtained from the three pairs of waxy and normal starches, in most cases the effects of HMT on normal starches were more pronounced than the corresponding waxy starches.     

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.