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PubMedDate not supplied

Measurement of the molecular weight distribution of debranched starch.

Combining molecular weight distribution (MWD) data for linear chains of debranched starch from capillary electrophoresis and from size exclusion chromatography (SEC) with detection by differential refractive index and by multi-angle laser light scattering has enabled Mark-Houwink parameters to be determined for linear starch chains. For accurate results, it was found to be important to take SEC band broadening into account, and a methodology for implementing this is presented. This deconvolution technique can be used to reveal features such as maxima or shoulders in the MWD which have qualitative as well as quantitative significance. Remarkably, these data show that the empirical Mark-Houwink relation between molecular weight and hydrodynamic volume is, for linear debranched starch, valid for much lower molecular weights than synthetic polymers. This implies that these Mark-Houwink parameters can be used with "universal calibration" to enable SEC to be used with relative ease to provide MWDs for debranched starch for essentially any degree of polymerization.

Chromatography, Gel↗
PubMed2006

Development of a low glycemic maize starch: preparation and characterization.

A low glycemic index starch was developed by partial alpha-amylase treatment, and its fine structure responsible for slowly digestible and resistant properties was investigated. Different digestion rates were obtained for gelatinized, retrograded starch by varying the enzyme dosage and reaction time. Analysis by high performance size-exclusion chromatography (HPSEC) coupled with multiangle laser-light scattering indicated that the molecular weighs of amylopectin and amylose were reduced during the digestion, to less than 100 kDa. A debranched chain length study using high performance anion-exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector and HPSEC revealed that short chains of amylopectin and noncrystalline amylose were rapidly digested, while DPn 121 chains showed resistance, followed by DPn 46 chains. X-ray diffraction analysis revealed that the crystalline structure in the treated starches survived cooking. These starches not only have slowly digestible and resistant character, but also retain some branched structure for adequate functionality.

Administration, Oral↗
PubMed2006

Gelatinization of starch in excess water: beyond the melting of lamellar crystallites. A combined wide- and small-angle X-ray scattering study.

The gelatinization of waxy rice, regular rice, and potato starch suspensions (66% w/w moisture) was investigated by real-time small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) during heating and by fast ramp differential scanning calorimetry (DSC). The high-angle tail of the SAXS patterns suggested the transition from surface to mass fractal structures in the DSC gelatinization range. Amylose plays a major role in determining the dimensions of the self-similar structures that develop during this process as the characteristic power-law scattering behavior extends to lower scattering angles for regular than for waxy starches. Crystallinity of A-type starches is lost in the temperature region roughly corresponding to the DSC gelatinization range. At the end of the gelatinization endotherm, the B-type potato starch showed residual crystallinity (WAXD), while SAXS-patterns exhibited features of remaining lamellar stacks. Results indicate that the melting of amylopectin crystallites during gelatinization is accompanied by the (exothermic) formation of amorphous networks.

Amylose↗
PubMedDate not supplied

Purification and kinetics of a raw starch-hydrolyzing, thermostable, and neutral glucoamylase of the thermophilic mold Thermomucor indicae-seudaticae.

The purified glucoamylase of the thermophilic mold Thermomucor indicae-seudaticaehad a molecular mass of 42 kDa with a pI of 8.2. It is a glycoprotein with 9-10.5% carbohydrate content, which acted optimally at 60 degrees C and pH 7.0, with a t(1/2) of 12 h at 60 degrees C and 7 h at 80 degrees C. Its experimental activation energy was 43 KJ mol(-1) with temperature quotient (Q(10)) of 1.35, while the values predicted by response surface methodology (RSM) were 43 KJ mol(-1) and 1.28, respectively. The enzyme hydrolyzed soluble starch at 50 degrees C (K(m) 0.50 mg mL(-1) and V(max) 109 micromol mg(-1) protein min(-1)) and at 60 degrees C (K(m) 0.40 and V(max) 143 micromol mg(-1) protein min(-1)). The experimental K(m) and V(max) values are in agreement with the predicted values at 50 degrees C (K(m) 0.45 mg mL(-1) and V(max) 111.11 micromol mg(-1) protein min(-1)) and at 60 degrees C (K(m) 0.36 mg mL(-1)and V(max) 142.85 micromol mg(-1) protein min(-1)). An Arrhenius plot indicated thermal activation up to 60 degrees C, and thereafter, inactivation. The enzyme was strongly stimulated by Co(2+), Fe(2+), Ag(2+), and Ca(2+), slightly stimulated by Cu(2+) and Mg(2+), and inhibited by Hg(2+), Zn(2+), Ni(2+), and Mn(2+). Among additives, dextran and trehalose slightly enhanced the activity. Glucoamylase activity was inhibited by EDTA, beta-mercaptoethanol, dithiothreitol, and n-bromosuccinimide, and n-ethylmaleimide inhibited its activity completely. This suggested the involvement of tryptophan and cysteine in catalytic activity and the critical role of disulfide linkages in maintaining the conformation of the enzyme. The enzyme hydrolyzed around 82% of soluble starch and 65% of raw starch (K(m) 2.4 mg mL(-1), V(max) 50 micromol mg(-1) protein min(-1)), and it was remarkably insensitive to glucose, suggesting its applicability in starch saccharification.

Enzyme Activation↗
PubMed2001

Nutritional properties of starch in buckwheat products: studies in vitro and in vivo.

The nutritional characteristics of buckwheat starch were studied to identify the possibility for reduced postmeal metabolic responses to various buckwheat products. The in vitro rate of starch hydrolysis and resistant starch (RS) formation in boiled buckwheat groats and in a series of breads, baked with 30-70% of buckwheat flour (BWF) or groats (BWG), respectively, were evaluated in vitro. In parallel, postprandial glucose and insulin responses and also the satiety score to BWG and wheat bread with 50% BWG as compared with the reference white wheat bread (WWB) were studied in healthy humans. The highest concentration of RS was found in boiled BWG (6% total starch basis). The RS level in bread products based on different proportions of BWF or BWG (30-70%) varied from 0.9 to 4.4%. The rate of in vitro amylolysis was significantly lower (P < 0.05) in all buckwheat products in comparison with the reference WWB. The calculated hydrolysis indices (HI) were lowest in boiled BWG (HI = 50) and in bread with 70% BWG (HI = 54). Consumption of boiled BWG or bread based on wheat flour and 50% BWG induced significantly lower postprandial blood glucose and insulin responses compared with the WWB. The calculated glycemic and insulinemic indices (GI and II) for boiled BWG were 61 and 53 and for the buckwheat bread, 66 and 74, respectively. The highest satiety score was found with boiled BWG. It is concluded that buckwheat has potential use in the design of foods with lower GI properties.

Adult↗
PubMed2001

Development of NMR and raman spectroscopic methods for the determination of the degree of substitution of maleate in modified starches.

In this paper we report the application of NMR spectroscopy and Raman spectroscopy to determine the degree of maleate substitution in maleinated starches. Five kinds of maleinated starches were investigated and calibration sets were constructed to derive linear regression equations that may be used to predict the degree of maleate substitution for starch samples with unknown amounts of chemical modification. The calibration sets reported have very high linearity (r > 0.99) for both the NMR and Raman methods. The NMR and Raman calibration sets allow fast and nondestructive measurement of the degree of maleate substitution for different starches with little need of sample preparation.

Calibration↗
PubMed2002

Characterization of resistant starch type III from banana (Musa acuminata).

Banana starch (Musa acuminata var. Nandigobe) was evaluated for its use in generating resistant starch (RS) type III. Structural, physicochemical, and biological properties of these products were analyzed. The investigated process includes debranching of the native starch and retrogradation under different storage temperatures and starch concentrations. After enzymatic debranching, a high amount of low-molecular-weight polymers with a degree of polymerization between 10 and 35 glucose units beside a higher molecular weight fraction were found. The resulting products comprised RS contents of about 50%. After heat-moisture treatment, the RS yield increased up to 84%. Peak temperatures of about 145 degrees C found in DSC measurements pointed to a high thermal stability of the RS products. In vitro fermentations of the RS products, carried out with intestinal microflora of healthy humans, resulted in a molar ratio of acetate:propionate:butyrate of about 49:17:34. The established method allowed the production of a high-quality RS with prebiotic properties for health preventing applications.

Amylose↗
PubMed2003

Detection of a novel three component complex consisting of starch, protein, and free fatty acids.

A water soluble three way complex composed of starch, whey protein, and free fatty acid (FFA) was detected in a dilute three component system after heating. In high-performance size exclusion chromatography (HPSEC) profiles of the starch-protein-FFA system, the three way complex eluted between amylopectin and amylose. The molecular mass of the complex, based on multiangle laser light scattering/HPSEC and pullulan standards, was estimated to be approximately (6-7) x 10(6) Da. Carbohydrate measurement by the phenol-sulfuric acid method clearly showed that the starch amylose fraction shifted to a higher molecular weight elution volume following complexation. Whey protein existed as large disulfide-linked aggregates and is speculated to be the organizer of the three way complex. Differential scanning calorimetry of the freeze-dried complex showed the presence of an amylose-FFA melting endotherm, thus proving that FFA was the third component in the three way complex and that the amylose-FFA complex was one of the structural components of the complex. The complexation mechanism and its relationship with changes in starch functionality were discussed.

Amylopectin↗
PubMed2005

Comparative study of the retrogradation of intermediate water content waxy maize, wheat, and potato starches.

The retrogradation of extruded starches from three different botanical sources was studied in concentrated conditions (34 +/- 1% water) at 25 degrees C using differential scanning calorimetry (DSC) and isothermal calorimetry, Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray scattering. Potato starch showed the highest rate of retrogradation (approximately 0.17 h(-1)) followed by waxy maize (approximately 0.12 h(-1)), while the retrogradation of wheat starch was the slowest (approximately 0.05 h(-1)). In addition to the kinetics, the extent of molecular order in the retrograded samples was studied in detail in terms of "short-range" (helical) and "long-range" (crystalline) distance scales. The amylopectin crystallinity indices were essentially the same (approximately 47-51% amylopectin basis) for the three starches. However, significant differences were found in the enthalpy of melting measured by DSC after "full" retrogradation (potato, 11.6 +/- 0.7; waxy maize, 9.0 +/- 0.5; and wheat, 6.1 +/- 0.3 J/g of amylopectin). The degree of short-range molecular order in the retrograded state determined by FTIR was waxy maize > potato > wheat. The effect of amylopectin average chain length and the polymorphism of the crystalline phase were taken into account to explain the differences in the retrogradation enthalpies.

Amylopectin↗
PubMed2005

Influence of incorporated wild Solanum genomes on potato properties in terms of starch nanostructure and glycoalkaloid content.

Interspecific somatic hybrids produced by protoplast fusion between two wild Solanum species (S. acaule, acl; S. brevidens, brd) and cultivated potato Solanum tuberosum (tbr) were analyzed in terms of the starch nanometer-range structure and glycoalkaloid (GA) contents. The crystallinity of starch granules, the average size of starch crystallites, and the lamellar distances were obtained from tuber samples using wide-angle and small-angle X-ray scattering methods. These measurements showed that incorporation of wild genomes from either nontuberous (brd) or tuberous (acl) Solanum species caused no significant modifications of the nanostructure of potato starch. In contrast, the GA profiles of the hybrids, which were analyzed by LC-ESI-MS in both tuber and foliage samples, differed considerably from those of cultivated potato. Regardless of the low total tuber GA concentrations (approximately 9 mg/100 g of fresh weight), the somatic hybrids contained GAs not detected in the parental species. A high proportion of spirotype GAs consisting of 5,6-dihydrogenated aglycons, for example, alpha-tomatine and tomatidine bound with solatriose, and chacotriose were found in the hybrids. In conclusion, the foliage of interspecific hybrids contained a higher variation in the structures of GAs than did the tubers.

Alkaloids↗
PubMed2005

Structural stability and prebiotic properties of resistant starch type 3 increase bile acid turnover and lower secondary bile acid formation.

Microbial metabolism is essential in maintaining a healthy mucosa in the large bowel, preferentially through butyrate specific mechanisms. This system depends on starch supply. Two structurally different resistant starches type 3 (RS3) have been investigated with respect to their resistance to digestion, fermentability, and their effects on the composition and turnover of bile acids in rats. RSA (a mixture of retrograded maltodextrins and branched high molecular weight polymers), which is more resistant than RSB (a retrograded potato starch), increased the rate of fermentation accompanied by a decrease of pH in cecum, colon, and feces. Because they were bound to RS3, less bile acids were reabsorbed, resulting in a higher turnover through the large bowel. Because of the rise of volume, the bile acid level was unchanged and the formation of secondary bile acids was partly suppressed. The results proved a strong relation between RS3, short chain fatty acid production, and microflora. However, butyrate specific benefits are only achieved by an intake of RS3 that result in good fermentation properties, which depend on the kind of the resistant starch structures.

Animals↗
PubMed2005

Kinetics of the surface hydrolysis of raw starch by glucoamylase.

The hydrolysis of raw starch catalyzed by glucoamylase has been studied with starch granules of different sizes by use of an amperometric glucose sensor by which the direct and continuous observation of the concentration of glucose can be achieved even in a thick raw starch suspension. The initial rate of the enzymatic hydrolysis in the raw starch suspension increased with increasing concentration of the enzyme to approach a saturation value and was proportional to the amount of substrate. Also, the rate was proportional to the specific surface area of the substrate. The experimental results can be explained well by the rate equations derived from a three-step mechanism, which consists of adsorption of the free enzyme onto the surface of the substrate, reaction of the adsorbed enzyme with the substrate, and liberation of the product.

Glucan 1,4-alpha-Glucosidase↗
PubMed2006

Discrimination of irradiated starch gels using FT-Raman spectroscopy and chemometrics.

The effects of gamma-irradiation on starch gels were characterized at the molecular level by Fourier transform (FT) Raman spectroscopy. Starches from five different sources were gelatinized and irradiated at 3, 5, and 10 kGy using a Co60 gamma-irradiator. Gamma-irradiation effects on starch gels were noted by the C-H stretch (2800-3000 cm(-1)) and O-H stretch (3000-3600 cm(-1)) and bend (1600-1800 cm(-1)) regions of the FT-Raman spectra. FT-Raman molecular fingerprints obtained through spectral analyses were used for discrimination of the gels based on the extent of irradiation by means of two different pattern-recognition techniques: canonical variate analysis (CVA) and soft modeling of class analogy (SIMCA). A complete discrimination of irradiated starches was attained using a hybrid partial least-squares (PLS) and CVA model, using the spectral variations in the C-H stretch and O-H stretch and bend regions of FT-Raman spectra. Using the same spectral regions, SIMCA predicted 84% of samples correctly.

Chemical Phenomena↗
PubMed2006

Amylose-lipid complexes as controlled lipid release agents during starch gelatinization and pasting.

The effect of amylose-lipid (AM-L) complexes consisting of amylose populations with different peak degrees of polymerization (DP) and complexed with glyceryl monostearate (GMS) or docosanoic acid (C22) on the pasting properties of wheat and rice starches was evaluated with a rapid visco analyzer (RVA). AM-L complexes were formed by both (i) addition of lipids to amylose fractions with peak DP 20, 60, 400, or 950 at 60 degrees C or (ii) potato phosphorylase-catalyzed amylose synthesis in the presence of lipids. All AM-L complexes affected pasting properties in line with their dissociation characteristics. AM-L complexes therefore have potential as "controlled lipid release agents" with effects markedly different from those observable with emulsifier addition in starch pasting. More in particular, short chain AM-L complexes resulted in a starch pasting behavior comparable to that of cross-linked starch, as evidenced by reduced granule swelling, good viscosity stability in conditions of high temperature and shear, and a stable cold paste viscosity.

Amylose↗
PubMed2006

Influence of drying temperature, water content, and heating rate on gelatinization of corn starches.

The gelatinization properties of starch extracted from corn and waxy corn dried at different temperatures were determined at various water contents and heating rates by differential scanning calorimetry. All gelatinization transition temperatures increased with drying temperature and heating rate. Onset and peak temperatures remained relatively constant, whereas end temperature decreased in the presence of excess water. The gelatinization enthalpy (deltaH(g)) of corn starch decreased with drying temperature at 50% water; however, it remained constant for waxy corn starch. The effects of water content and heating rate on deltaH(g) were dependent on each other. The minimum water levels required for gelatinization of starch extracted from corn dried at 20 and 100 degrees C are 21 and 29%, respectively. The activation energy (E(a)) was calculated using an Arrhenius-type equation and two first-order models; the degree of conversion (alpha) was predicted using a newly proposed model that produced good results for both E(a) and alpha.

Calorimetry, Differential Scanning↗
PubMed2006

Octenyl succinic anhydride modified early indica rice starches differing in amylose content.

Seven early indica rice starches with different amylose contents were modified by octenyl succinic anhydride (OSA) in aqueous suspension systems to evaluate the effect of amylose contents on starch esterification. The crystalline structure and pasting properties of starches were investigated using X-ray diffraction and a Rapid Visco Analyzer (RVA). The results indicated that the amylose content had a positive impact on the OSA modification. As the amylose content increased from 0 to 39.6%, the degree of substitution increased from 0.024 to 0.030 and the reaction efficiency increased from 62.8 to 77.5%. X-ray diffraction scans confirmed that the amylose was mainly present in the amorphous domain of the granule and was highly substituted after the OSA treatment. The RVA profiles demonstrated that the OSA starches had higher viscosities than their native counterparts. Moreover, negative correlations were observed between the amylose content and the major RVA parameters (e.g., peak viscosity, hot paste viscosity, cool paste viscosity, and breakdown viscosity).

Amylose↗
PubMed2006

Molecular properties and activities of tuber proteins from starch potato cv. Kuras.

Potato starch production leaves behind a huge amount of juice. This juice is rich in protein, which might be exploited for food, biotechnological, and pharmaceutical applications. In northern Europe cv. Kuras is dominant for industrial starch production, and juice protein of freshly harvested mature tubers was fractionated by Superdex 200 gel filtration. The fractions were subjected to selected activity assays (patatin, peroxidase, glyoxalases I and II, alpha-mannosidase, inhibition of trypsin, Fusarium protease, and alcalase) and protein subunit size determination by SDS-PAGE and mass spectrometry. Proteins present in SDS-PAGE bands were identified by tryptic peptide mass fingerprinting. Protein complexes such as ribosomes and proteasomes eluted with the void volume of the gel filtration. Large proteins were enzymes of starch synthesis dominated by starch phosphorylase L-1 (ca. 4% of total protein). Five identified dimeric patatin variants (25%) coeluted with four monomeric lipoxygenase variants (10%) at 97 kDa. Protease inhibitor I variants (4%) at 46 kDa (hexamer) inhibited alcalase. Fourteen Kunitz protease inhibitor variants (30%) at 19 kDa inhibited trypsin and Fusarium protease. Carboxypeptidase inhibitor variants (5%) and defensins (5%) coeluted with phenolics. The native sizes and molecular properties were determined for 43 different potato tuber proteins, several for the first time.

Electrophoresis, Polyacrylamide Gel↗
PubMed1999

Effect of steam pressure treatment on the physicochemical properties of Dioscorea starches.

Dioscorea alata and Dioscorea rotundata starches were subjected to steam pressure treatments (0.35, 0.7, and 1.05 kg cm(-)(2)) for different periods. The total amylose content in the treated starches was not significantly affected, but the soluble amylose content decreased 3-5-fold. Reducing values and lambda(max) of the iodine complexes were unaffected. Viscosity of the starch paste was reduced by the treatments, and at higher pressures and longer time of treatments, the peak viscosity values were reduced to very low values. Pasting temperatures were enhanced considerably. Swelling volumes underwent reduction, but no change in solubility occurred. Clarity and paste stability were markedly lowered. The results suggest that starch granules are compressed by the steam pressure treatment, leading to vast changes in physicochemical properties.

Amylose↗