Effect of acid‐ethanol treatment followed by ball milling on structural and physicochemical characteristics of cassava starch

Structural and physicochemical characteristics of cassava starch treated with 0.36% HCl in anhydrous ethanol during 1 and 12 h at 30, 40, and 50°C followed by ball milling for 1 h were analyzed. Average yield of acid‐ethanol starches reached 98% independent of the treatment conditions. Solubility of acid‐ethanol starches increased with reaction temperature and time, but it did not change after ball milling. Granule average size reduced with chemical treatment from 25.2 to 20.0 µm after 12 h at 50°C. Ball milling decreased the granule average diameter of the native starch and those chemically treated at 30°C/1 h or 40°C/1 h, but it did not alter the starches treated for 12 h, independent of temperature. From scanning electron microscopy (SEM), starch granules presented round shape and after modification at 50°C/12 h, before and after ball milling, showed a rough and exfoliated surface. Some granules were deformed, suggesting partial gelatinization that was more intense after milling. Starch crystallinity increased as temperature and time of chemical treatment were increased, while amylose content, intrinsic, and pasting viscosities decreased. Gelatinization temperatures increased for all chemical starches. The findings can be related to the preferential destruction of amorphous areas in the granules, which are composed of amylose and amylopectin. After ball milling, the starch crystallinity decreased, amylose content, intrinsic, and pasting viscosities kept unchanged and gelatinization temperatures and enthalpy reduced. Ball milling on native and chemical starches caused the increase of amorphous areas with consequent weakening and decreasing of crystalline areas by breaking of hydrogen bonds within the granules.     

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.     

微波辐射对木薯淀粉性质影响

研究微波辐射前后木薯淀粉物化性质变化,采用微波对30%水分含量木薯淀粉进行处理,结果表明,微波处理增强对应X–射线衍射峰强度,降低膨胀度、溶解度和冻融稳定性;木薯淀粉经处理后糊化起始温度升高、粘度降低,但其粘度曲线不改变。以上数据表明,在淀粉颗粒内无定形区和结晶区直链淀粉与直链淀粉、直链淀粉与支链淀粉发生交互作用,微波处理使淀粉分子发生一定程度降解。     

Structures and Physicochemical Properties of Acid‐Thinned Corn,Potato and Rice Starches

The structures and physicochemical properties of acid‐thinned corn, potato, and rice starches were investigated. Corn, potato, and rice starches were hydrolyzed with 0.14 N hydrochloric acid at 50 °C until reaching a target pasting peak of 200—300 Brabender Units (BU) at 10% solids in the Brabender Visco Amylograph. After acid modification the amylose content decreased slightly and all starches retained their native crystallinity pattern. Acid primarily attacked the amorphous regions within the starch granule and both amylose and amylopectin were hydrolyzed simultaneously by acid. Acid modification decreased the longer chain fraction and increased the shorter chain fraction of corn and rice starches but increased the longer chain fraction and decreased the shorter chain fraction of potato starch, as measured by high‐performance size‐exclusion chromatography. Acid‐thinned potato starches produced much firmer gels than did acid‐thinned corn and rice starches, possibly due to potato starch's relatively higher percentage of long branch chains (degree of polymerization 13—24) in amylopectin. The short‐term development of gel structure by acid‐thinned starches was dependent on amylose content, whereas the long‐term gel strength appeared dependend on the long branch chains in amylopectin.     

Microstructural and Physicochemical Properties of Oxidized Potato Starch for Paper Coating

Heat-induced structural changes were examined for a series of potato starches differing in degree of oxidation and prepared as 25 and 35% dispersions. The molecular weight of amylopectin decreased markedly with the degree of oxidation. Microstructural studies revealed that all oxidized potato starch dispersions heated to 90deg;C contained whole granules. The least oxidized potato starch (Raisamyl 316) paste contained large numbers of swollen granules filled with dissolved amylose. In the more oxidized potato starch dispersions, both amylopectin and amylose were solubilized within the granule. Mixing of the amylose and amylopectin occurred and amylose- and amylopectin-rich domains could be seen inside the granule. At 35% concentration all starches studied formed a gel during cooling (from 90 to 30deg;C). The lower the degree of oxidation, the higher the gelling temperature. Raisamyl 310 formed the firmest gel. The gel formation of most oxidized potato starches was weak. Raising the heating temperature from 90 to 120deg;C, in combination with shearing, delayed the gelation.     

Structural and Physicochemical Characteristics of Lintnerized Native and Sour Cassava Starches

The comprehension of the structure of starch granules is important for the understanding of its physicochemical properties. Native and sour cassava starches after being analyzed with respect to their pasting properties and baking expansion capacity, were treated with 2.2 N HCl at 38 °C for a maximum of nine days. The starch granules remaining after lintnerization were analyzed for amylose content and intrinsic viscosity, by X‐ray diffraction, scanning electron microscopy and chromatographic analysis. The results indicated that the acid hydrolysis on all starches occurred in two steps. The first one, with high hydrolysis rate, was characterized by a quick degradation of the amorphous part of the granules whereas the second step, with lower hydrolysis rate, was characterized by a higher resistance of the organized areas of the granules to acid treatment. Most of the amylose chains were found in the amorphous areas of starch granules only a small percentage was involved in the crystalline regions. The microscopic and chromatographic analysis demonstrated that the acid hydrolysis was not able to disrupt the entire granular crystalline structure. Fermented starch showed amylose and/or amylopectin chain fractions resistant to pullulanase, probably due to structural alterations during fermentation.     

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.     

Effect of acid hydrolysis in the presence of anhydrous alcohols on the structure,thermal and pasting properties of normal,waxy and high‐amylose maize starches

Maize starches with different amylose contents (0%, 23% and 55%) were treated in anhydrous methanol, ethanol, 2‐propanol, 1‐butanol with 0.36% HCl at 25 °C for 5 days. Results showed that the extent of change in physicochemical properties increased from methanol to butanol. Treated waxy maize starch showed higher than 65% solubility at above 75 °C. The diffraction peak at 2θ = 5.3° of amylomaize V starch disappeared after treatment in ethanol, 2‐propanol and 1‐butanol. Acid–alcohol treatment decreased the gelatinisation temperature of normal (from 64.5 to 61.9 °C) and waxy maize (from 68.1 to 61.1 °C) starches, while it increased that of amylomaize V (from 68.7 to 72.3 °C) starch. The extent of the decrease in the pasting viscosity followed the following order: amylomaize V < normal maize < waxy maize. This study indicated that acid–alcohol treatment degraded preferentially the amorphous regions and the different changes depended on the crystal structure and amylose content of starch.     

Isolation and physicochemical characterisation of starch from cocoyam (Colocasia esculenta) grown in Malawi

BACKGROUND: The aim of this study was to determine the physicochemical properties of starches isolated from Malawian cocoyams and compare them with those of cassava and corn starches. RESULTS: The purity of the isolated starches varied from 851 to 947 g kg^?1 and pH from 4.93 to 6.95. Moisture, ash, protein, fat and amylose contents ranged from 104 to 132, 0.3 to 1.5, 3.5 to 8.4, 0.9 to 1.6, and 111 to 237 g kg^?1, respectively. Cocoyam starches gave higher potassium and phosphorus but lower calcium levels than the other starches. The shape of starch granules varied from spherical to polygonal with cocoyam starches displaying smaller‐sized granules than cassava and corn starches. Cocoyam starches gave a higher wavelength of maximum iodine absorption and blue value but lower reducing capacity values than cassava and corn starches. The extent of acid hydrolysis of the starches also differed. Cocoyam starches exhibited amylopectin molecules of higher molecular weights but amylose molecules of lower molecular weights than cassava and corn starches. Cocoyam starches exhibited lower water absorption capacity and swelling power, paste clarity and viscosity but higher solubility, gelatinisation temperatures and retrogradation tendencies than cassava and corn starches. CONCLUSIONS: The physicochemical properties of native Malawian cocoyam starches vary among the different accessions and differ from those of cassava and corn starches. Copyright © 2010 Society of Chemical Industry     

Thermal, microstructural and textural characterisation of gelatinised corn, cassava and yam starch blends

The functional properties of mixtures of maize, cassava and yam starches and their relationships with microstructural characteristics were investigated. Experiments were performed following the simplex‐centroid design with internal points and restrictions (upper limit) for yam starch proportion. The statistical model used (Scheffé canonical equation) was a powerful tool to predict the pastes behaviour within the limits of the experimental area. Polynomials with second level interactions were applied to obtain the surface response. Viscoelastic attributes of mixtures differed from those of individual starches. As shown by differential scanning calorimetry and microscopical observations, physical properties of the mixtures depended on the type of networks obtained. These networks varied upon yam, corn and cassava starch proportions as each one has a particular characteristic: gelatinisation temperature, granule size, swelling capacity and amylose/amylopectin ratio among others.     

Characterization of Cassava Starch Attributes of Different Genotypes

The genetic variation of starch of Indonesian cassava genotypes with various morphological characteristics of roots and eco‐geographical origin was characterized and compared. The morphological characteristics of the roots of 71 collected cassava genotypes were classified into yellow and white for flesh colors, purple, pink, light brown, yellow, cream and white for cortex colors, dark brown and light brown for external colors, as well as conical and cylindrical for root shapes. Starch samples extracted from 17 genotypes showed that the amylose content varied from 17.1 to 21.3%. The mean particle size was around 7.3 to 9.7 µm, and the gelatinization onset temperature was in the range of 63.5‐66.1°C. Seven genotypes were analyzed in more detail for their physicochemical properties. The granule size distribution was in the range of 3.2 µm to 17.6 µm for d10 and d90 (i.e. 90% of the granules were bigger than 3.2 μm and 90% were smaller than 17.6 μm), respectively, and the median granule size was around 7.7‐10.8 µm. The gelatinization temperatures of the different cassava starches were in the range of 63.5‐66.1°C. The phosphate content varied from 23.5‐25.3 nmol/mg starch. Particle size distribution and gelatinization temperature as well as the phosphate content of the starch of the selected seven genotypes also showed minor differences among the genotypes. The swelling power of all starches showed some differences between genotypes, but the profiles were similar. The opacity of starch of all the tested genotypes increased twofold within six days, but no large differences among the different genotypes could be detected except for the genotype Ketan. Strength of the gels, which are indicated with force, adhesiveness, cohesiveness, and elasticity, also did not show large differences.     

Influence of moisture content on the degradation of waxy and normal corn starches acid-treated in methanol

Waxy and normal corn starches with different moisture contents, 5.1-16.9% and 4.8-15.9%, respectively, were prepared and treated in methanol containing 0.36% HCl at 45 °C for 1 h. Recovery of all the treated starches was found to be above 90%. Peak viscosity, gelatinization temperature and enthalpy change of gelatinization of waxy and normal corn starches decreased after treatment and this decrement was found to be more in treated starches having lower initial moisture content. The weight-average degree of polymerization and chain length (CL) of waxy and normal corn starches decreased upon acid-methanol treatment. The decrement ratio of molecular weight of modified starches was found to be negatively correlated with the initial moisture content of the starches. The decrement ratio of normal corn starch was higher than waxy corn starch with similar moisture content of starch. The content and CL of long chain fraction of amylopectin for waxy corn starch slightly decreased after treatment, while no obvious trend was found among starches with different moisture contents. CL of amylose for acid-methanol-treated normal corn starch decreased and this change was found to be higher in starches with lower initial moisture contents. Results demonstrated that the initial moisture content of starch granules strongly influenced the functional properties and degradation of starch treated by acid in methanol.     

Preparation and structural properties of small‐particle cassava starch

Acid and enzyme hydrolyses followed by ball milling were applied to fracture cassava starch granules. Microscopic and chromatographic evidence suggested different mechanisms of the two hydrolyses. Using the enzyme process, granules with a sponge‐like structure and shells with the interior hydrolysed were produced. Amylose and amylopectin were subjected equally to multiple attacks by enzymes, with no significant change in granule crystallinity. The hydrolysed residues could not be effectively broken down by ball milling, although the crystallinity was destroyed. In contrast, the acid treatment caused superficial external corrosion, mainly at the amorphous lamellae, ie the branch points of amylopectin. Acid‐lintnerised starch granules were mostly of Degree of polymerization, DP 10–15 and exhibited increased crystallinity and brittleness, making them more susceptible to breakdown upon milling. Ball milling, although destroying some degree of crystallinity, could effectively reduce the size of acid‐hydrolysed starch, with no further degradation of amylodextrin molecules. By a combination of lintnerisation and ball milling, smaller particle starch (3–8 µm compared with 3–30 µm for native starch) could be produced. It is clear that removal of the amorphous phase prior to milling is critical for effective rupture of the granules. Copyright © 2003 Society of Chemical Industry     

Morphology and Microstructure of Maize Starches with Different Amylose/Amylopectin Content

The morphology and microstructure of maize starches with different amylose/amylopectin ratios (waxy: 0/100; normal maize: 23/77; Gelose 50: 50/50; Gelose 80: 80/20) were studied by microscopy with ordinary and polarized light, scanning electron microscopy (SEM) and X‐ray diffraction (XRD). Generally, the granules of the amylopectin‐rich starches were more regular in shape than those of the amylose‐rich starches, but the surfaces of the amylose‐rich starches were smoother than those of the amylopectin‐rich starches. The birefringence and particle size of the granules were waxy > normal maize > G50 > G80, which also corresponds with the trend of molecular weight. Waxy and normal maize starches showed typical A‐type patterns, while G50 and G80 show B‐type patterns. Crystallinity increases with increasing the amylopectin content.     

Influence of hydroxypropylation on retrogradation properties of native,defatted and heat-moisture treated potato starches

Recent studies have shown that defatting and heat-moisture treatment cause structural changes within the amorphous and crystalline regions of potato starch. Furthermore, the alkaline reagents (NaOH and Na₂SO₄) used during hydroxypropylation has been shown to cause structural changes within the amorphous and crystalline regions of native, defatted and heat-moisture treated starches. In this study, we have compared (using different techniques) the retrogradation properties of potato starch before and after physical (defatting and heat-moisture treatment), and chemical (alkaline treatment and hydroxypropylation) modification. Turbidity measurements showed that changes in turbidity during storage (4°C for 24 h and then at 40°C for 29 days) of native, defatted and heat-moisture treated gelatinized starch pastes were influenced by the interplay of two factors: (1) interaction between leached starch components (amylose–amylose, amylose–amylopectin, amylose–amylopectin), and (2) interaction between granule remnants and leached amylose and amylopectin. In alkali treated gelatinized native, defatted and heat-moisture treated starch pastes, turbidity changes on storage was influenced by aggregation of granule remnants. Hydroxypropylation decreased the rate and extent of increase in turbidity during storage of native, defatted and heat-moisture treated starches. The change in turbidity during storage of hydroxypropylated starch pastes was influenced by the interplay between: (1) steric effects imposed by hydroxypropyl groups on chain aggregation, (2) aggregation between small granule remnants, and (3) settling of large granule remnants beneath the path of the spectrophotometer beam. Stored gelatinized pastes of native, defatted and heat-moisture treated starches gave a `B' type X-ray pattern. A similar pattern was also observed after alkaline treatment, and hydroxypropylation. However, the X-ray intensity of the strong reflection at 5.2 Å decreased after alkaline treatment and hydroxypropylation. The retrogradation endotherm (monitored by differential scanning calorimetry) occurred after 2 days storage in native, defatted and heat-moisture treated starches. A similar trend was also observed after alkaline treatment. However, the retrogradation endotherm appeared only after 7 days in hydroxypropylated starches. The enthalpy of retrogradation in all starches decreased on alkaline treatment and hydroxypropylation.     

Gel Chromatography of Residue and Extract Obtained from Starch Granules by Hot Aqueous 1 -Butanol Solution Treatment

Starch granules of corn starches (normal, waxy, amylo and amylowaxy) and potato starch were treated with hot aqueous solution saturated with 1-butanol and fractionated. These fractionated starches were subjected to an advanced gel chromatography with a column system of Toyopearl HW 75 F. Amylose of normal maize and potato starches was perfectly leached out from the granules, but that of amylo maize was not perfectly extracted. Amylo and amylowaxy maize starches were proved to have large amount of low-molecular weight material. Normal and amylo maizes, and potato starches contained a high-molecular-weight material recognized as amylose type, and it is strongly suggested that amylopectin of normal maize is not same as that of waxy maize. It was found that the GPC analysis was a very important step to estimate an amylose content since a part of amylopectin made a precipitable complex with 1-butanol.     

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。     

Temperature Related Structural Changes in Wheat and Corn Starch Granules and Their Effects on Gels and Dry Foam

The effect of processing temperature on structural changes in wheat, corn, and high amylose corn starch granules was investigated and related to the mechanical properties of gels and microcellular foam (MCF). Scanning electron micrographs (SEM) showed that wheat starch granules form ghosts with thicker walls than dent corn granules. The granule wall was permeable to water and appeared to be at least partially permeable to the solubilized contents of the granule. The ghost walls became visibly porous after heating at 95ºC for 60 min and were completely solubilized by heating to 120ºC. High‐amylose corn starch (HACS) granules were completely dissolved by heating to 140ºC. Gels made with wheat starch had higher gel strength and dynamic modulus compared to dent corn starch gels. The density, compressive strength and modulus of MCF were lower in samples cooked for 60 min. The density of dent corn MCF was higher than that of wheat starch which may have accounted for higher compressive strength and modulus in the corn sample. MCF made from HACS had higher surface area and lower density, compressive strength, and modulus than the other starches tested. There were no significant differences in pore volume or surface area due to extended cooking times.     

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.     

Comparative Studies on Some Physico-chemical, Thermal, Morphological, and Pasting Properties of Acid-thinned Jicama and Maize Starches

Comparative studies on acid hydrolysis of jicama and maize starch were carried out using concentrations of hydrochloric acid of 1.5%, 3.0%, and 4.5% (w/v), for 3 and 6 h, at 40°C. Native maize and jicama starches showed important morphological, thermal, and structural differences from those of tubers and cereals which potentially offer diverse industrial applications. Jicama starch showed low amylose content (12%) and small size of starch granules. Due to these characteristics, jicama starch was more susceptible to degradation during hydrolysis process than maize starch. Under the experimental conditions employed, the acid degradation was not particularly severe, as shown by scanning electronic microscopy analysis which showed small degraded zones and similar X-ray patterns in both starches. However, jicama starch was more susceptible to acid hydrolysis than maize starch, as revealed by the considerable increase in water solubility index, damaged starch, and crystallinity values. Also, the higher susceptibility of jicama starch than maize starch to the hydrolysis conditions was reflected in the sugar content release during hydrolysis. The relative crystallinity of hydrolyzed maize starches decreased during hydrolysis, while those of hydrolyzed jicama starches increased attributable to the lower amylose content of jicama starch in relation to maize starch. Maize and jicama hydrolyzed starches showed low viscosity values with relation to their native starch counterparts. However, native jicama starch showed lower viscosity values than maize starch, suggesting a lower internal stability of the starch granules during hydrolysis. Both native and hydrolyzed maize starches showed higher enthalpy, T _o, T _p, and T _c values than jicama starch and the broadening of the endotherms decreased during the hydrolysis of both starches.