Crystallinity of Acid Treated Corn Starch

The hydrolysis of corn starch by 1N H₂SO₄-30% ethanol aqueous solution at 45°C increased linearly with increasing of hydrolysis time for 20 d. The relative crystallinity of native corn starch showed 0.350 by X-ray diffraction and it increased gradually with increasing of hydrolysis time up to 8 d. The increasing ratio of 1/hydrolysis residue to hydrolysis time increased more largely than that of relative crystallinity after 14 d. On the other hand, the relative crystallinity of native corn starch by deuteration showed 0.341 very near to the value by X-ray diffraction. Moreover, this increasing ratio of the crystallinity accompanied by acid hydrolysis showed an inclination similar to that given by X-ray diffraction. These facts suggest that the exchanging of OH for OD groups may be caused very a little in crystalline region of corn starch granules.     

On the Acid Resistance of Starch Granules

When potato starch was hydrolyzed to form Nägeli amylodextrin by 16% sulfuric acid at 30°C, only the amorphous portion of the starch granules was deteriorated. The crystallinity of Nägeli amylodextrin showing the hydrolysis ratio of 0.22 was 1.28 times as large as that of original starch. The hydrolysis process at above 45°C was given by two exponential equations. The value of acid resistance portion (C_o) at 30 and 38°C was 100%, while the values at 45, 50 and 55°C were 67, 38 and 18%, respectively. The high value of C_o generally showed the high acid resistance in the various starches. Sweet potato and waxy rice starches were more easily hydrolyzed than other starches, although they gave the relatively high value of C_o. Thus, it was slightly more difficult for low acid resistance portion of potato starch to be hydrolyzed than for that of other starches. Moreover, that of waxy rice was easily hydrolyzed.     

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.     

Hydration and physicochemical properties of small‐particle cassava starch

Acid hydrolysis followed by ball milling was applied to cassava starch in order to fracture the granules. Lintnerisation led to degradation first in the amorphous domains and increased the crystallinity. The resulting increase in internal defects and brittleness made the granules more susceptible to breakage upon milling. Ball milling, although leading to some degree of crystallinity loss, could effectively reduce the size of acid‐hydrolysed starch while the total double helix remained relatively unchanged. The resulting small‐particle starch was structurally more heterogeneous (wider T_m range). Swelling of small‐particle starch was accompanied by solubilisation of water‐soluble fragments at a temperature greater than 60 °C. The properties of individual granules are strongly influenced by the hydration and physicochemical properties of their amorphous and crystalline domains. © 2002 Society of Chemical Industry     

超声波辅助酸解制备淀粉纳米颗粒及其特性表征

本研究以马铃薯淀粉为原料,用超声波辅助酸水解的方法制备淀粉纳米颗粒,并以颗粒的粒径、产率为指标,研究了硫酸浓度、酸解时间和超声功率对制备淀粉纳米颗粒的影响,试验结果表明:酸易水解淀粉颗粒非结晶区,使颗粒的结晶度明显提高,颗粒的粒径可降至1 800~2 200 nm,超声波辅助处理后,粒径能进一步降低至120~150 nm范围内。试验得出最适制备工艺参数为:在40℃条件下,用3 mol/L硫酸水解15%的淀粉乳,搅拌速度为100 r/min,超声功率为400 W,酸解20 h后,得到的淀粉纳米颗粒平均粒径在50~80 nm范围内,产率为14.1%,结晶度由21.57%增长到46.35%,吸水率由34.8%增长到96.9%。     

Preparation and Characterization of Annealed‐Enzymatically Hydrolyzed Tapioca Starch and the Utilization in Tableting

Tapioca starch was annealed at 60°C for 90 min followed by hydrolysis with α‐amylase at 60°C at various lengths of time (30, 60 and 120 min) to obtain high‐crystalline starches. The reaction products were subjected to spray drying to obtain annealed–enzymatically hydrolyzed–spray dried tapioca starch (SANET) in the form of spherical agglomerated granules. The properties of SANET were compared with those of annealed–spray dried tapioca starch without enzymatic treatment (SANT) and native–spray dried tapioca starch (SNT). Scanning electron micrographs of the starch samples were used to study the morphological changes and to suggest the mode of enzyme attack during hydrolysis. The á‐amylase preferentially attacked the interior of the starch granules, leaving a deep round hole on the starch granule surface. It was found by X‐ray diffraction that both annealing and amylolysis did not alter the A type diffraction pattern. The% relative crystallinity of SANET was raised with increasing hydrolysis time and with decreasing amylose content. High performance size exclusion chromatography (HPSEC) demonstrated the decrease of the degree of polymerization (DP) of the amylose fraction of SANET after prolonged hydrolysis. For the utilization of SANET as tablet filler, it was directly compressed by a tablet compression machine at 4 kN to obtain tablets. The increased relative crystallinity of starch resulted in increased crushing strength and disintegration time, but in a decreased tablet friability.     

Effect of Hydrothermal Treatment on Formation and Structural Characteristics of Slowly Digestible Non‐pasted Granular Sweet Potato Starch

The formation and structural characteristics of slowly digestible non‐pasted granular starch in sweet potato starch were investigated under various hydrothermal treatment conditions. The moisture content of the sweet potato starch was adjusted to 20, 50 or 90%, and the starch was heated at 40, 55 or 100°C for 12 h in a dry oven. The relative crystallinity of the hydrothermally treated samples was decreased with increasing temperature, and the X‐ray diffraction patterns of the samples were altered from C_b‐type to A‐type. Microscopic observations did not reveal any changes in the starch granules of any samples except those with moisture contents of 50 and 90% that were heated at 100°C. When gelatinization parameters were examined, samples with moisture contents of 50 and 90% that were heated at 55°C and samples of all moisture contents that were heated at 100°C had peak temperatures higher than that of raw starch but gelatinization enthalpies lower than that of raw starch. The swelling factor of the samples heated at 40°C did not change significantly, whereas that of samples heated at 55 and 100°C was decreased at increased moisture levels. The sweet potato starch with 50% moisture content that was heated at 55°C had the highest content of granular slowly digestible starch, about 200% that of raw starch, although our study did not involve further hydrothermal treatment conditions. Further study is required to complete a process for more efficient production of heat stable and slowly digestible starch.     

Physicochemical,crystalline, and thermal properties of native and enzyme hydrolyzed Pueraria lobata (Willd.) Ohwi and Pueraria thomsonii Benth. starches

Starches isolated from the bulbs of Pueraria lobata (Willd.) Ohwi (PLO) and Pueraria thomsonii Benth. (PTB) were hydrolysed by glucoamylase for different lengths of time (2, 4, 8, 12, and 24 h). The hydrolysis results were compared by scanning electron microscope (SEM), X‐ray power diffractometer (XRD), and differential scanning calorimetry (DSC). The SEM results revealed that both of the PLO and PTB starches showed the same hydrolysis mechanism, which indicated that the glucoamylase primarily attacking the exterior of starch granules and then the interior. The results of XRD revealed the crystalline type of PTB starch changed from C‐type to A‐type with crystallinity reducing from 43.5 to 20.9% during the hydrolysis. Unlike PTB starch, the PLO starch did not show marked changes in crystalline style but lower degree of crystallinity was obtained from 32.4 to 13.7% during the hydrolysis. All the XRD results demonstrated that B‐type polymorph was preferentially degraded than A‐type polymorph in the C‐type starch. The DSC results revealed that both of the PLO and PTB starches showed decreased enthalpy of gelatinization (ΔH_gel) and gelatinization temperature range (R)‐value after hydrolysis, while the gelatinization temperature (T_p) indicated different tendency, initially ranging from 68.6 to 64.3°C and then increasing to 67.8°C for PLO starch. While for PTB starch, the T_p‐value showed progressive reduction from 85.4 to 74.3°C during the whole process.     

Melting Properties and Lintnerisation of Potato Starch with Different Degrees of Phosphorylation

Lintner dextrins were prepared from size fractionated potato starch granules from two potato varieties (90BKG22 and Lady Rosetta) that contain high or low natural content of esterified phosphate, respectively. The time course of hydrolysis showed the typical two‐phase kinetics, with a maximal degree of hydrolysis of between 74% and 81% after 30 days of hydrolysis, except for the fraction of smallest granules of the low phosphorylated variety (low P), which was hydrolysed to 98%. The relative amount of retained glucose‐6‐P in the Lintner dextrins was 18.6% for the low P variety and 46.6% for the high P variety. However, when calculating the relative distribution of phosphate in the granules, it was shown that approximately 80% (low P) and 35.5% (high P) was located in the amorphous region. Melting characteristics were followed by differential scanning calorimetry (DSC). The DSC endothermic peak became low and broad during the time course of hydrolysis, with rise in enthalpy change, indicating a strong dependency on the amorphous region of the granules. After annealing the same fractions showed the typical raise in gelatinisation temperature and narrowing of gelatinisation peak. The values of the melting temperatures (T_o, T_m and T_c) are positively correlated to the degree of phosphorylation of the starch dextrin fractions both before and after annealing.     

Characterization of nanoparticles prepared by acid hydrolysis of various starches

Various starches of different AM contents and origins such as wx maize, normal maize, high AM maize, potato, and mungbean starches were hydrolyzed using a H₂SO₄ solution (3.16 M) at 40°C for 7 days, and the starch particles were isolated from the hydrolysates by centrifugation. The hydrolysis rates varied from 61.4 to 90.9% depending on the starch type. Unexpectedly, A‐type starches were more resistant to the acid hydrolysis than B‐type starches. XRD results revealed that the starch particles with B‐crystalline type exhibited a decrease in peak intensity. In addition, in a DSC analysis, the crystals remaining in the B‐type starch particles were readily disrupted in the water dispersion so that no melting endotherm appeared. Electron microscopy confirmed that the starch particles had round or oval shapes with diameters ranging from 40 to 70 nm, which possibly represented the starch blocklets in granules. The acid degraded mainly AM and long AP chains, resulting in increasing the proportion of short chains.     

Comparison of the morphological,crystalline, and thermal properties of different crystalline types of starches after acid hydrolysis

A‐type maize starch, B‐type Fritillaria ussurensis, and C‐type Rhizoma dioscorea starches were hydrolyzed (32 days) with 2.2 N HCl. Regardless of the crystallinity level, starch with predominant B‐crystalline type was less susceptible to acid degradation than A‐type and C‐type starches, and initial rates of hydrolysis in B‐type was lower than others. The SEM and XRD results revealed that different types of starch displayed different hydrolysis mechanisms. The acid corrosion started from the exterior surface of A‐type and B‐type starches followed by the core of granules. However, the hydrogen ions primarily attacked the interior of the C‐type R. dioscorea starch granules and then the exterior. FT‐IR results confirmed that the amorphous regions in the starch granules were hydrolysed first. After 8–32 days of hydrolysis, the acid‐modified C‐type starch showed typical A‐type characteristics upon analysis of the XRD pattern. The average particle size of hydrolytic starch decreased with increasing hydrolysis time. The thermal results revealed that the hydrolytic starch showed lower ΔH than the native starch, while displaying higher peak width (T_c − T_o) value.     

Chemical and Physical Characterisation of Grain Tef [Eragrostis tef (Zucc.) Trotter] Starch Granule Composition

Chemical and physical properties of starch granules isolated from five grain tef (Eragrostis tef) varieties were characterised and compared with those of maize starch. Endogenous starch lipids extracted with hot water‐saturated n‐butanol and total starch lipids extracted with n‐hexane after HCl hydrolysis were 7.8 mg/g (mean) and 8.9 mg/g (mean), respectively, slightly lower than in the maize starch granules. The starch phosphorus content (0.65 mg/g) was higher than that of maize starch but virtually the same as reported for rice starch. The starch granule‐swelling factor was lower than that of maize starch and extent of amylose leaching was higher. The starch X‐ray diffraction pattern was characteristic of A type starch with a mean crystallinity of 37%, apparently lower than the crystallinity of maize starch and more similar to that reported for rice and sorghum starches. The starch DSC gelatinisation temperature was high, like for other tropical cereals; T_o, T_p, T_c and ΔH were in the range 63.8—65.4, 70.2—71.3, 81.3—81.5 °C and 2.28—7.22 J/g, respectively. The lower swelling, apparently lower percentage crystallinity and lower DSC gelatinisation endotherms than maize starch suggest that the proportion of long amylopectin A chains in tef starch is smaller than in maize starch.     

Gelatinization Transitions of Acid‐modified Tapioca Starches by Differential Scanning Calorimetry (DSC)

Tapioca starch was partially hydrolyzed by 6 % and 12 % hydrochloric acid (w/v) at room temperature for various length of time. The gelatinization transitions of the acid‐modified tapioca starches were studied using Differential Scanning Calorimetry. Starch suspensions (67 % moisture) were heated at 5 °C/min to follow melting transition of amylopectin. As the hydrolysis time increased, onset (T_o), peak (T_p) and conclusion (T_c) temperatures of gelatinization have been observed to increase, in the same order of relative crystallinity, until reaching some critical values, then decreased with the large broadening of the endotherms. The increasing of the transition temperatures corresponded to the retrogradation of the remaining partially hydrolyzed amylose followed by a decrease of these parameters corresponding to the reduction of the length of the chains of double helices amylopectin.     

酸解时间对大米淀粉结构性质的影响

以4种不同直链淀粉含量的大米淀粉(0%的优糯3号、10.90%的稻花灿、21.03%的聚两优、28.46%的华优香占)为原料,酸解处理不同时间,以酸解大米淀粉的酸解率、颗粒形貌、结晶性质、溶解度的变化为指标衡量不同酸解时间对大米淀粉结构及性质的影响。结果表明,不同直链淀粉含量的大米淀粉具有不同的耐酸性,酸解时间对不同直链淀粉含量大米淀粉的结构和性质有着不同的影响。大米淀粉酸解率与直链淀粉含量成反比,优糯3号为50%而华优香占仅为30%;所有淀粉颗粒在酸解后均产生一定程度的破碎,偏光十字变形直至消失,酸解相同时间,直链淀粉含量高的大米淀粉破碎率低;酸解未改变淀粉的晶型,仍为A晶型;随着酸解时间的延长相对结晶度增加;淀粉的溶解度随着酸解时间的增加而增大。     

Properties of starch from root tuber of Stephania epigaea in comparison with potato and maize starches

The dry root tuber of Stephania epigaea contained 36.5% starch, indicating a good starch source. In this study, starch was isolated from S. epigaea. Its morphology, physicochemical, and functional properties were investigated and compared with potato and maize starches. S. epigaea starch had small spherical granules with centric hila and large ellipsoidal granules with eccentric hila, and granule sizes varied from 7 to 40 μm. The starch had 33.9% amylose content and B-type crystallinity. The gelatinization onset, peak, and final temperatures were 59.4, 62.3, and 66.2°C, respectively, and were lower than those of potato and maize starches, but the enthalpy (16.3 J/g) was higher than that of potato and maize starches. The peak, hot, final, and breakdown viscosities were 2227, 1623, 2149, and 594 dPa s, respectively, and were significantly higher than those of maize starch and lower than those of potato starch. S. epigaea starch was more susceptible to amylase hydrolysis and in vitro digestion than potato starch and less than maize starch. This study would be useful for the applications of starch from S. epigaea in the food and non-food industries.     

The Reactivity of Porcine Pancreatic alpha-Amylase Towards Native,Defatted and Heat-moisture Treated Potato Starches Before and After Hydroxypropylation

Potato starch was defatted (hot 75% n-propanol) and heat-moisture treated (100°C, 30% moisture) for various time intervals. The results showed that the above treatments increased the susceptibility of potato starch granules (heat-moisture treated > defatted) towards hydrolysis by porcine pancreatic α-amylase. These differences can be accounted for by the structural changes that occur within the amorphous and crystalline regions of the starch granule during defatting and heat-moisture treatment. Native, defatted (7 h) and heat-moisture treated (100°C, 30% moisture, 16 h) potato starches were hydroxypropylated (to different levels of molar substitution [MS]) with propylene oxide (2 → 20 %). The results showed that the alkaline reagents (NaOH and Na₂SO₄) used during hydroxypropylation increased the susceptibility of the above starches (native > defatted > heat-moisture treated) towards hydrolysis by α-amylase. Addition of propylene oxide to alkali treated starches, further enhanced their susceptibility, towards α-amylase. However, granule susceptibility towards α-amylase did not increase exponentially with increase in MS. The extent of hydrolysis began to decrease at MS levels of 0.29 (native), 0.28 (heat-moisture treated) and 0,26 (defatted).     

Comparative Acid Modification of Various Starches

Eight starches (maize, sorghum, finger millet, waxy and nonwaxy rice, chick pea, tapioca and potato) were acid modified with 0.5N HCl at 50°C. Alkali fluidity number (AFN) increased progressively with time of modification, and was highest in cereal followed by root, legume, and tuber starches. However, reduction in the number average molecular weight (M̄_n) was in the reverse order. Potato starch had the highest M̄_n, among the nonwaxy native starches and showed the greatest fall upon modification, whereas cereal starches had the least M̄_n in native form and showed the least fall. In fact, there was a clear proportionality between the M̄_n, of native starch and the extent of its hydrolysis under any given set of conditions. This relationship could be expressed by two intersecting lines, one for grains and one for root and tuber starches. When acid modified starches were recovered and dried without neutralization, hydrolysis still continued strongly in potato starch and slightly in tapioca, finger millet and sorghum starches. Other starches showed no change.     

Effects of fatty acid chain length on properties of potato starch–fatty acid complexes under partially gelatinization

A series of starch–fatty acid samples were prepared using potato starch and four fatty acids differing in their chain length, including lauric (C12), myristic (C14), palmitic (C16), and stearic (C18) acids. The results indicated that the fatty-acid chain length played a significant role in altering the properties of potato starch–fatty acid complexes. The complexing index of potato starch–fatty acid complexes decreased from 0.38 to 0.18 with increasing carbon-chain length. V-type crystalline polymorphs were formed between starch and four fatty acids, with shorter chain fatty acids preserving more crystalline structure. X-ray diffraction studies revealed that the degree of crystallinity exhibited by the starch samples was dependent on the fatty-acid chain length. In the Fourier transformed infrared spectrum of the samples, the new spikes at 2917, 2850, 1018, and 720 cm^?1 were assumed to be related to the presence of fatty long chains. The formation of amylose–fatty acid complex inhibited granule swelling of potato starch, w\ith longer chain fatty acids showing greater inhibition. Scanning electron microscopy microscopic examination indicated that amylose–fatty acid interactions taken place during starch gelatinization retarded the destruction of the granules.     

Comparative Investigation on Acid Hydrolysis of Sweet Potato Starches with Different Amylopectin Chain‐Length

The solubilization of starch from the new sweet potato cultivar “Quick Sweet” (QS) in 2.2 M aqueous HCl occurred at a much higher rate than that from normal sweet potato (NS). QS starch has an abnormal amylopectin chain‐length distribution with an unusually high percentage of short side‐chains. Two‐stage hydrolysis occurred in both cases. The apparent first‐order kinetic constants (k) were calculated for both stages of the hydrolytic process in both types of sweet potato starch. A more drastic difference between the investigated starches (k for QS and NS starches was 27.0×10^‐2 d^‐1 and 7.0×10^‐2 d^‐1, respectively) was observed for the first stage of the hydrolysis affecting the amorphous regions of starches whereas the rate for the second stage (the degradation of the crystalline part) for the starch from QS was only slightly higher. The role of the structural defectiveness of QS in decreasing the granular resistance to acid hydrolysis and increasing the absorptive properties of the granules for water molecules is discussed.     

The effect of starch gelatinization and solute concentrations on T g′ of starch model system

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the T_g′ of the gelatinized potato starch but had clearly increased their ΔC_p in the T_g′ region. Annealing at a temperature slightly below the T_g′ of −5 °C, led to maximal freeze‐concentration in the total/partial gelatinized starch and a higher T_g′ value at about −3 °C was obtained. The T_g′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The T_g′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on T_g′ than sucrose. © 2000 Society of Chemical Industry