Studies of the retrogradation process for various starch gels using Raman spectroscopy

The retrogradation of untreated wild-type starches (potato, maize, and wheat), waxy maize starches, and one pregelatinized, modified amylose-rich starch was investigated continuously using Raman spectroscopy. The method detects conformational changes due to the multi-stage retrogradation, the rate of which differs between the starches. The pregelatinized, modified amylose-rich starch shows all stages of retrogradation in the course of its Raman spectra. In comparison to amylose, the retrogradation of amylopectin is faster at the beginning of the measurements and slower in the later stages. The untreated starches can be ranked in the order of their rate of retrogradation as follows: potato>maize>wheat.     

Oxidized and acid thinned starch derivatives of hybrid maize: functional characteristics, wide-angle X-ray diffractometry and thermal properties

Starch isolated from hybrid maize (8535-23) was subjected to oxidation and acid thinning. Proximate analyses revealed that moisture, ash, protein, fat, fibre, and pH reduced after oxidation and acid thinning. Percentage amylose content reduced from 20.42% in native starch to 18.76 and 17.65% in oxidised and acid thinned starch derivatives, respectively. Wide-angle X-ray diffraction patterns indicated strong peaks at 15.9 degrees, 17.2 degrees, 18.8 degrees, and 25.0 degrees 2theta. No significant difference was observed between the X-ray pattern of the native and modified starches. Both swelling power and solubility increased with increase in temperature. Oxidation and acid thinning reduced swelling power and increased solubility starch. At all pHs, both oxidation and acid thinning reduced the swelling capacity of the native starch. Oxidation increased water and oil absorption capacity of the native starch, while both hydrophilic and hydrophobic properties reduced following acid thinning. Least gelation concentration reduced in acid thinned starch but increased in oxidised derivative. Pasting temperature (Tp), peak viscosity (Pv), hot paste viscosity (Hv), and viscosity after 30 min holding at 95 degrees C (H(v30)) reduced following both modifications. However, values for cold paste viscosity (Cv) and setback (SB) reduced in oxidised derivative and increased in acid thinned starch. Light transmittance of the starch pastes reduced with increase in storage days, however, reduction was more pronounced in native and acid thinned starches. Onset temperature (To), peak temperature (Tp) and conclusion temperature (Tc) of gelatinisation reduced in modified starches compared with native hybrid maize starch. Also, gelatinisation enthalpy reduced after oxidation and acid thinning. Enthalpy of regelatinisation increased as days of storage of starch paste increased.     

Preparation and characterization of gelatinized granular starches from aqueous ethanol treatments

In order to modify the properties of native starch granules, the formation of gelatinized granular forms (GGS) from normal, waxy, and high amylose maize, as well as potato and tapioca starches was investigated by treating granules with aqueous ethanol at varying starch:water:ethanol ratios and then heating in a rotary evaporator to remove ethanol. The modified starches were characterized using bright field, polarized and electron microscopy. Short/long range molecular order and enthalpic transitions on heating were also studied using infrared spectroscopy, X-ray diffractometry and differential scanning calorimetry respectively. A diffuse birefringence pattern without Maltese cross was observed for most GGS samples. Treatment with aqueous ethanol resulted in starch-specific changes in the surface of granules, most noticeably swelling and disintegration in waxy maize, surface wrinkling in normal maize and tapioca, swelling and opening-up in potato starches, and swelling and bursting in high amylose maize. The ratio of ethanol to water at which original granular order was disrupted also varied with starch type. GGS had less short range molecular order than native granules as inferred by comparing 1047/1022 wave number ratio from infrared spectroscopy. Similarly, A- and B-type diffraction reflections were either reduced or completely lost with evolution of V-type patterns in GGS.     

Influence of Soy Protein Isolate Hydrolysates Obtained under High Hydrostatic Pressure on Pasting and Short-Term Retrogradation Behavior of Maize Starch

The influences of soy protein isolate hydrolysate (SPIH) obtained during different pressure treatments for 4 h on pasting and short-term retrogradation behaviors of maize starch (MS) were investigated. The results showed solubility of MS markedly increased, whereas swelling power decreased with increased SPIH concentration and pressure. Compared with native MS, the addition of SPIH led to decrease of peak viscosity, final viscosity, setback, and breakdown, whereas pasting temperature was increased. Meanwhile, differential scanning calorimetry (DSC) analysis also showed an increase in gelatinization temperature. In addition, low-field nuclear magnetic resonance (LF-NMR) analysis indicated that the tight association of water and starch molecules was observed with increasing pressures and additions of SPIH. Confocal laser scanning microscopy (CLSM) and atomic force microscope (AFM) images indicated that SPIH obtained at 200 MPa dispersed in the MS gel system to block the formation of hydrogen bonds and inhibit the recrystallization of MS. Fourier transform infrared (FTIR) spectroscopy analysis demonstrated that the addition of SPIH resulted in a decrease in hydrogen bonds within the starch molecules and the result supported above CLSM and AFM measurement results. The results proved that the addition of SPIH could effectively influence pasting characteristics and inhibit the short-term retrogradation of MS, which can be helpful to the application of SPIH in starch-based functional foods.

     

Physico-chemical and morphological characteristics of New Zealand Taewa (Maori potato) starches

The physico-chemical, morphological, thermal, pasting, textural, and retrogradation properties of the starches isolated from four traditional Taewa (Maori potato) cultivars (Karuparera, Tutaekuri, Huakaroro, Moemoe) of New Zealand were studied and compared with starch properties of a modern potato cultivar (Nadine). The relationships between the different starch characteristics were quantified using Pearson correlation and principal component analysis. Significant differences were observed among physico-chemical properties such as phosphorus content, amylose content, swelling power, solubility and light transmittance of starches from the different potato cultivars. The starch granule morphology (size and shape) for all the potato cultivars showed considerable variation when studied by scanning electron microscopy and particle size analysis. Starch granules from Nadine and Moemoe cultivars showed the presence of large and irregular or cuboid granules in fairly high number compared with the starches from the other cultivars. The transition temperatures (T_o; T_p; T_c) and the enthalpies (ΔH_gel) associated with gelatinization suggested differences in the stability of the crystalline structures among these potato starches. The Moemoe starch showed the lowest T_o, while it was higher for Tutaekuri and Karuparera starches. Pasting properties such as peak, final and breakdown viscosity and texture profile analysis (TPA) parameters of starch gels such as hardness and fracturability were found to be higher for Nadine and Huakaroro starches. The Nadine and Huakaroro starch gels also had lower tendency towards retrogradation as evidenced by their lower syneresis (%) during storage at 4 °C. Principal component analysis showed that the Tutaekuri and Nadine cultivars differed to the greatest degree in terms of the properties of their starches.     

Rheological and structural properties of starches from γ-irradiated and stored potatoes

Starch was extracted from irradiated and stored potato tubers and the properties were compared to CIPC (chlorpropham) treated tubers. The granule properties and dynamic viscoelasticity in temperature ramp and frequency sweep modes were studied while heating the samples. Starch structural characteristics were investigated by high performance anion exchange chromatography (HPAEC) and Fourier transform infrared spectroscopy (FTIR). Gamma-irradiation of potato tubers at a dosage of 0.1 kGy induced some degradation of starch molecules, resulting in earlier swelling of starch granules, and greater extents of amylose and total carbohydrate leaching. The early swelling phenomenon was also enhanced with tuber storage time. The retrogradation rate and extent for a concentrated starch gel also increased with tuber storage time whereas γ-irradiation delayed the gel retrogradation. Sprout inhibiting methods could be selected based on the specific processing and texture requirements of the end products.     

Identification of the thermal transitions in potato starch at a low water content as studied by preparative DSC

The aim of this work was to identify the transitions in the complex DSC profiles of potato starch at a low water content. Preparative DSC involves the thermal processing of samples in stainless steel DSC pans in a way that allows their subsequent structural characterization. The low temperature (LT), dual melting (M1–M2), and high temperature (HT) endotherms observed in DSC profiles of potato starch with 16% water were assigned to enthalpy relaxation, melting with preservation of granular identity, and transition of the melted granules into a molecular melt, respectively. Granular melting was accompanied by a strong reduction of swelling capacity. Significant molecular degradation was observed after the HT transition. There is evidence that HT does not represent a true thermodynamic transition, but is due to a volume change in the sample. In contrast to potato starch, maize starch with 16% water gave inhomogeneous samples after processing, presumably because of its low packing density.     

The influence of amylose and amylopectin characteristics on gelatinization and retrogradation properties of different starches

Physico-chemical properties of starch from wheat, rye, barley (waxy, high-amylose and normal-amylose), waxy maize, pea and potato (normal-amylose and high-amylopectin) were studied. Emphasis was given to the amylose (total, apparent and lipid-complexed) and amylopectin characteristics as well as to the gelatinization and retrogradation properties measured using differential scanning calorimetry. The total amylose content varied from ca. 1 % for waxy maize to 37% for high-amylose barley. The amylopectin characteristics were determined by high-performance size-exclusion chromatography after debranching with isoamylase. The weight-average degree of polymerization ( _w) was 26, 33 and 27 for the A-, B-, and C-type starches, respectively. In general, the potato starches exhibited the highest retrogradation enthalpies and the cereal starches the lowest, while the pea starch showed an intermediate retrogradation enthalpy. The data were analysed by principal component analysis (PCA). The _w showed positive correlation to the melting interval, the peak minimum, the offset temperatures of the retrogradation-related endotherm as well as to the gelatinization and retrogradation enthalpies. However, the high-amylose barley retrograded to a greater extent than the other cereal starches, despite low _w (24). The amylose content was negatively correlated to the onset and the peak minimum temperatures of gelatinization.     

State diagram of potato starch–water mixtures treated with high hydrostatic pressure

Potato starch–water mixture was treated with high hydrostatic pressure (HHP) of up to 1.2 GPa, and effect of starch content (10–70% (w/w)) on HHP-gelatinization was investigated by differential scanning calorimetry (DSC). Depending on the treatment pressure and potato starch content, DSC thermograms showed decrease in enthalpy change of heat gelatinization reflecting the progress of HHP-gelatinization and increase in enthalpy change of re-gelatinization of retrograded starch. From the viewpoint of the enthalpy changes, physically modified state of HHP-treated potato starch–water mixtures was classified as follows: no change, partial gelatinization, complete gelatinization, partial gelatinization and retrogradation, and complete gelatinization and retrogradation. A state diagram of potato starch–water mixtures (treatment pressure vs. starch content) was presented.     

Increasing the efficiency of the enzymatic hydrolysis of potato starch in a membrane reactor

The aim of the work was to define the physicochemical parameters of a reaction system that alter the effectiveness of a continuous recycle membrane reactor during potato starch hydrolysis. The enzymatic hydrolysis of starch in an ultrafiltration reaction system proceeded with a continuous decrease in the permeate flux, accompanied by an increase in dry substance content in both the permeate and retentate fractions. The decrease in the permeate flux was caused by an increase in feed viscosity. If a prehydrolysis process was conducted, it was possible to enzymatically hydrolyse potato starch in solutions with concentrations up to 20%. A quasi-steady state of starch enzymatic hydrolysis was reached in the ultrafiltration reaction system by alternately supplementing it with starch solution and water.     

Physicochemical and Binder Properties of Starch Obtained from Cyperus esculentus

The purpose of this study was to isolate starch from the tubers of Cyperus esculentus L. and evaluate its physicochemical and binder properties. Extraction of starch using sodium metabisulfite yielded 37 g of starch per 100 g of the tubers. Scanning electron microscopy indicated that Cyperus starch consists of oval to elliptical particles with a smooth surface. Cyperus starch demonstrates a narrow particle size distribution with a mean of 8.25 μm. Cyperus starch conforms well to United States Pharmacopeia standards established for widely used starches like maize and potato. The X-ray powder diffraction pattern and moisture sorption profile of Cyperus starch were comparable to that of maize starch. Cyperus starch had lower swelling power than maize and potato starch, indicative of stronger associative forces within the granules. Carr’s index and Hausner ratio indicate that Cyperus starch should have comparable flow properties with respect to maize and potato starch. Cyperus starch was employed as binder for the formulation of metronidazole tablets. Formulations containing 5%, 7.5%, and 10% Cyperus starch were compared with those containing 10% potato starch. At 10% binder concentration, the tablets containing Cyperus starch exhibited better hardness and negligible friability as compared with those with potato starch. Although the binder concentration had a significant effect on the disintegration time of the tablets, it did not seem to affect the dissolution profile. These results indicate that Cyperus starch provides excellent binding properties without compromising drug release characteristics and should be explored in pharmaceutical formulations.Key words: Cyperus esculentus, Cyperus starch, pharmaceutical excipient, physicochemical evaluation, starch characterization     

Effects of an added inclusion-amylose complex on the retrogradation of some starches and amylopectin

The effects of added cetyltrimethylammonium bromide (CTAB)-amylose complex on retrogradation of some starches (waxy-maize, maize, and potato starch) and on amylopectin from potato have been studied by differential scanning calorimetry (DSC). The starches and amylopectin samples with added CTAB-amylose complex received four different heat treatments prior to storage and DSC measurements that either melted the complex or left the complex intact. The calorimetry measurements showed that intact CTAB-amylose complex had much less effect on decreasing the retrogradation of the starches and the amylopectin than samples with melted complex prior to measurements. This is discussed in relation to possible complex formation of amylopectin and lipids and the effects of adding uncomplexed lipids on the retrogradation of waxy starches and amylopectin.     

The Pasting and Gel Textural Properties of Corn Starch in Glucose,Fructose and Maltose Syrup

The pasting and gel textural properties of corn starch in syrup at different concentrations were investigated by Rapid Visco Analyzer (RVA) and Texture profile analysis (TPA) tests. The results showed that the pasting temperatures of corn starch greatly increased, especially at higher sugar concentration. Increasing concentration of syrup caused an increase in peak, trough and final viscosity of corn starch. Peak viscosity and the disintegration rate of starch increased in the following order: fructose syrup> maltose syrup> glucose syrup. Increasing syrup concentration to 13%, 25% and 50% resulted in a lower retrogradation rate than the control. When the maltose syrup concentration increased to 50%, the retrogradation rate decreased to 14.30% from 33.38%. The highest hardness was observed when the syrup concentration was 25%. There was a particular low hardness when the concentration of syrup was 50%. The springiness of starch gels in syrup was similar at different concentrations.     

Extraction of starches from tuber crops using ammonia

Ammonia solution (0·03 ) was used to extract starch from various tuber crops by the conventional settling method. It was found that there was noticeable improvement in the yield of starch from Colocasia (6–16%), while it fell for sweet potato starch and remained almost the same for the other starches. The various properties of starch, thus extracted, were compared with those for starch obtained by water extraction. It was found that total amylose of all starches were unaffected while the ‘soluble amylose’ was slightly suppressed for Colocasia starch extracted with ammonia solution. Peak viscosity was found to be increased to a large extent for Colocasia and Dioscorea esculenta starches by ammonia extraction, while it was lowered for sweet potato starch. The swelling volume of Colocasia starch extracted with ammonia was similarly enhanced by 25%, but the Dioscorea esculenta starch did not show such a tendency. Sweet Potato starch suffered a reduction in swelling volume. Phosphorus content was found to be independent of the extraction medium.     

Synthesis, characterization and functional properties of low substituted acetylated corn starch

Acetylated corn starch (ACS) was synthesized by the reaction of native corn starch (NCS) with acetic anhydride (AA) in an aqueous medium in the presence of sodium hydroxide as a catalyst. The factors that could affect the degree of substitution (DS) and reaction efficiency (RE) of corn starch were investigated which included the reaction temperature and time, the mass ratio of AA to starch, the ratio of the water volume to starch mass and pH. The optimal DS of 0.071 and RE of 67.05% was obtained. FTIR spectrometry showed new bands at 1733, 1375 and 1252 cm(-1). The SEM of the ACS indicated some cavities on the granules which fused together, compared with NCS. Wide angle X-ray diffraction revealed that ACS had a similar profile as NCS (A type). However, the intensity of peaks were diminished. DSC thermograms exhibited that ACS had some lower gelatinization temperatures and enthalpies than NCS. The functional properties of ACS such as the swelling power, solubility, water absorption, clarity, freeze-thaw stability, retrogradation and viscosity were also studied. The results suggest that the ACS has much better functional properties than the NCS, and could be expected to have wide applications especially in food industry.     

Contribution of the net charge to the regulatory effects of amino acids and epsilon-poly(L-lysine) on the gelatinization behavior of potato starch granules

The effects of lysine (Lys), monosodium glutamate (GluNa), glycine, alanine and epsilon-poly(L-lysine) (PL) with different degrees of polymerization on the gelatinization behavior of potato starch granules were investigated by DSC, viscosity and swelling measurements, microscopic observation, and measurement of the retained amino acid amount to clarify the contribution of the net charge to their regulatory effects on the gelatinization behavior. The amino acids and PL each contributed to an increase in the gelatinization temperature, and a decrease in the peak viscosity and swelling. These effects strongly depended on the absolute value of their net charge. The disappearance of a negative or positive net charge by adjusting the pH value weakened the contribution. The swelling index and size of the potato starch granules changed according to replacement of the swelling medium. The amino acids and PL were easily retained by the swollen potato starch granules according to replacement of the outer solution of the starch granules.     

秸秆还田对旱作马铃薯块茎淀粉合成关键酶活性及基因表达的影响

为探讨秸秆还田下旱作马铃薯块茎形成过程中淀粉合成关键酶活性及基因表达特性,以马铃薯栽培品种"青薯9号"为材料,以露地栽培为对照,设置秸秆还田处理,研究了马铃薯块茎形成过程中淀粉合成关键酶活性、基因表达、淀粉糊化及累积指标。结果表明:秸秆还田显著提高了旱作马铃薯SSS酶活性,降低了AGPP、GBSS酶活性,而对SBE酶活性没有显著影响;显著提高了SSⅡ、SSⅢ基因表达量,降低了AGPase、GBSSⅠ、SBEⅠ、SBEⅡ基因表达量;显著增加了淀粉崩解值,减少了淀粉各阶段粘度、回生值,而对淀粉糊化温度没有显著影响;显著增加了直链淀粉含量及直/支链淀粉比,减少了总淀粉含量;GBSS酶活性与AGPase、SBEⅠ基因表达量呈显著正相关,与直链淀粉含量、直/支链淀粉比呈显著负相关;SBE酶活性与SSⅡ基因表达量、峰值粘度、低谷粘度、最终粘度、总淀粉含量呈显著正相关,与崩解值、糊化温度呈显著负相关;AGPase基因表达量与直链淀粉含量呈显著负相关;GBSSⅠ基因表达量与最终粘度、回生值呈显著正相关,与糊化温度呈显著负相关;淀粉糊化与累积无显著相关性。     

Change of granular and molecular structures of waxy maize and potato starches after treated in alcohols with or without hydrochloric acid

Starches from waxy maize and potato were treated in methanol and 2-propanol either with or without 0.36% hydrochloric acid at 65 °C for 1 h. The granule morphology, molecular structure and pasting properties of the starches were determined and the effects of treatments on the granule and molecular structures of starch were investigated. Starch treated in alcohols without acid showed loss of native order through the hilum of granules, and no obvious molecular degradation was found. However, acid–alcohol treated starch showed many cracks inside granules, and both waxy maize and potato starches showed obvious molecular degradation after treated. Furthermore, the amylose chains and long chains of amylopectin of starch were more easily degraded with acid–alcohol treatment. The pasting viscosity of acid–alcohol treated starches were also obviously less than that of their counterpart native starch and starch after alcohol treatment. The extent of degradation of molecules and the decrease of pasting viscosity on potato starch after acid–alcohol treated were more obvious than that of waxy maize starch. The result indicates that the degradation preferentially occur in the amorphous region when starch treated by acid–alcohol, and the degradation of starch molecules enhances the amorphous excretion and the occurrence of cracks inside the granules.     

Studies on the hydrothermal modifications of new cocoyam (Xanthosoma sagittifolium) starch

Native new cocoyam starch (nNCS) was subjected to annealing (aNCS) and heat moisture treatment at 18% moisture level (h₁₈NCS), 21% moisture level (h₂₁NCS), 24% moisture level (h₂₄NCS) and 27% moisture level (h₂₇NCS) as hydrothermal treatments. Scanning electron and light microscopy revealed round and polygonal shapes with sizes ranging from 15 to 40 μm for native and modified starches. nNCS showed “A” pattern X-ray diffraction and no significant differences were observed in the X-ray pattern of the modified starches. Swelling power and solubility reduced following heat moisture treatment. At all pH studied (2–12), unmodified new cocoyam starch exhibited higher swelling capacity and solubility than the modified derivatives. Hydrothermal modifications improved water absorption capacity but reduced oil absorption capacity. Pasting temperature of native starch shifted to higher values following annealing and heat moisture treatment. Hot paste viscosity (Hv), viscosity after 30 min holding at 95 °C (Hv₃₀) and cold paste viscosity (Cv) reduced after annealing and heat moisture treatment. The result also indicates that hydrothermal treatments reduced the tendency for setback. As the number of days of storage of starch paste increased from 1 to 10, light transmittance of all the starches reduced but marked reduction of light transmittance was observed in native starch. DSC studies revealed increase in gelatinization temperature following annealing and heat moisture treatment. Starch hydrothermal modifications reduced retrogradation as enthalpies of regelatinization reduced following modifications. The regelatinization peak in the second day scanning shifted to lower temperature than the gelatinization peak in first run heating DSC curve for all samples. The regelatinization peak also became larger and shifted to higher temperature range when the storage days increased from 2 to 7.     

Enzymatic degradation of and bovine serum albumin release from starch-acetate films

The effect of acetylation of potato starch on swelling, enzymatic degradation, and bovine serum albumin (BSA, molecular mass 68 kDa) release rate from polymer films was studied. Potato starch and potato starch acetates (SA), having a degree of substitution of 1.9 or 2.6, were investigated. Polymer films were incubated in phosphate buffer solution pH 7.4 in the absence and presence of enzymes (alpha-amylase, amyloglucosidase, esterase) or in human serum. The acetylation of potato starch decreased its swelling considerably. Increased acetylation of starch also considerably retarded its enzymatic degradation. Due to the decreased swelling and degradation of SA films, BSA was released much slower from SA films than from potato starch films, both in the presence and absence of enzymes.