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PubMed2006

Determination of the maximum water solubility of eight native starches and the solubility of their acidic-methanol and -ethanol modified analogues.

The maximum water solubilities of eight native starches from potato, shoti, tapioca, maize, waxy maize, amylomaize-7, wheat, and rice and their acid-methanol and acid-ethanol modified analogues have been determined. Maximum solubilities of 18.7 and 17.4 mg/mL were obtained for waxy maize and tapioca and 12.4 mg/mL for potato and maize starches by autoclaving 220 mg/10 mL at 121 degrees C; 8.7 mg/mL was obtained for shoti starch by stirring in 85:15 (v/v) Me(2)SO-H(2)O at 20 degrees C; and 7.0 and 5.2mg/mL for rice and amylomaize-7 starches by stirring in 1M NaOH at 20 degrees C. The acid-alcohol treated starches were 4-9 times more soluble than their native starches. The compositions of the solubilized starches had, in general, much higher ratios of amylose to amylopectin than the ratios in their native granules. A major exception to this was the acid-methanol treated potato, shoti, and rice starches that had much lower ratios of amylose to amylopectin than the ratios in their granules.

Amylopectin↗
PubMed2005

Continuous butanol fermentation and feed starch retrogradation: butanol fermentation sustainability using Clostridium beijerinckii BA101.

Use of starch solution as feed for butanol bioconversion processes employing Clostridium beijerinckii BA101 may have added economic advantage over the use of glucose. Acetone butanol ethanol (ABE) was produced from 30 gL(-1) starch solution using a continuous process. The bioreactor was fed at a dilution rate of 0.02 h(-1) and starch solution/feed volume (3 L) was replaced every 72 h. The continuous reactor fed with cornstarch solution (feed temperature 19 degrees C) produced approximately 6.0 gL(-1) total ABE. Increasing the feed storage temperature to 37 degrees C improved ABE production to 7.2 gL(-1) suggesting that retrogradation was occurring more rapidly at 19 degrees C. In both these cases the fermentation drifted toward acid production after approximately 260 h, consistent with the retrogradation of starch overtime. The use of soluble starch, which is less prone to retrogradation, resulted in the production of 9.9 gL(-1) ABE at 37 degrees C feed storage temperature, as compared to 7.2 gL(-1) ABE when cornstarch was used. It should be noted that gelatinized starch retrogradation takes place after sterilization and prior to use of the feed medium, and does not occur during long-term storage of the raw corn material in the months leading up to processing. The degree of hydrolysis of gelatinized starch decreased from 68.8 to 56.2% in 3 days when stored at 37 degrees C. Soluble starch which does not retrograde demonstrated no change in the degree of hydrolysis.

Acetone↗
PubMed1975

Digestibility of starches in infants and children.

The digestibility of various starches has been studied in normal infants of different ages. During balance periods of 3 days, while the infants were receiving known dietary quantities of the starch to be tested, the fecal content of lactic acid, glucose, dextrins, and starch was measured. After the first year of life, children were able to absorb almost completely 170 gm/m2 of body surface of cooked wheat starch given in the form of biscuit or macaroni. A lower absorption coefficient was found for potato starch given in the form of biscuit. Cooked wheat, tapioca, corn, rice, and potato starch in amounts of 45 and 85 gm/m2/day, respectively, for 1- and 3-mo-old infants, were almost completely absorbed. In 1-mo-old infants larger amounts (110 gm/m2/day) of cooked rice starch were well tolerated; it should therefore be possible to provide a large part of the carbohydrate requirements of infants from the first month of life with cooked starches.

Animals↗
PubMed2003

Potato starch granule nanostructure studied by high resolution non-contact AFM.

Surface studies at ambient conditions of potato starch granules subjected to multiple freezing and thawing, performed by a high resolution non-contact atomic force microscopy (nc-AFM), revealed some details of the starch granule nanostructure. After the treatment, a significant separation and a chain-like organisation of the granule surface elements have been observed. An accurate analysis of the granule surface nanostructure with a single amylopectine cluster resolution could be carried out. The oblong nodules of approximately 20-50 nm in diameter have been observed at the surface of the potato starch granules. The same size particles were precipitated by ethanol from gelatinized potato starch suspensions. They were also detected at the surface of oat and wheat starch granules. After multiple freezing and thawing, the eroded potato granule surface revealed a lamellar structure of its interior. The 30-40 nm inter-lamellar distances were estimated by means of nc-AFM. These findings fit previously proposed dimensions of the structural elements in the crystalline region of the starch granule. The observed surface sub-particles might correspond to the single amylopectine side chain clusters bundled into larger blocklets packed in the lamellae within the starch granule. The results supported the blocklet model of the starch granule structure.

Chemical Precipitation↗
PubMed2002

Properties and applications of starch-converting enzymes of the alpha-amylase family.

Starch is a major storage product of many economically important crops such as wheat, rice, maize, tapioca, and potato. A large-scale starch processing industry has emerged in the last century. In the past decades, we have seen a shift from the acid hydrolysis of starch to the use of starch-converting enzymes in the production of maltodextrin, modified starches, or glucose and fructose syrups. Currently, these enzymes comprise about 30% of the world's enzyme production. Besides the use in starch hydrolysis, starch-converting enzymes are also used in a number of other industrial applications, such as laundry and porcelain detergents or as anti-staling agents in baking. A number of these starch-converting enzymes belong to a single family: the alpha-amylase family or family13 glycosyl hydrolases. This group of enzymes share a number of common characteristics such as a (beta/alpha)(8) barrel structure, the hydrolysis or formation of glycosidic bonds in the alpha conformation, and a number of conserved amino acid residues in the active site. As many as 21 different reaction and product specificities are found in this family. Currently, 25 three-dimensional (3D) structures of a few members of the alpha-amylase family have been determined using protein crystallization and X-ray crystallography. These data in combination with site-directed mutagenesis studies have helped to better understand the interactions between the substrate or product molecule and the different amino acids found in and around the active site. This review illustrates the reaction and product diversity found within the alpha-amylase family, the mechanistic principles deduced from structure-function relationship structures, and the use of the enzymes of this family in industrial applications.

Amino Acid Sequence↗
PubMed2006

Phosphate positioning and availability in the starch granule matrix as studied by EPR.

Cu(2+) was introduced as an EPR probe into the starch granules isolated from different starch crop genotypes including transgenically modified potatoes generated for extreme amylose and starch phosphate monoester concentrations. Several discrete copper adducts bound to the starch matrix with different strength was revealed. It was found that phosphate has a significant influence on the type of these species, their number, location in the structure, and strength of binding. Well dispersed Cu(2+) complexes with axial symmetry are formed in the semicrystalline part of the starch linked through O-P- bonds in the phosphorylated starches. In the amorphous part of the starch, freely rotating hexaaqua complexes of Cu(2+) and complexes coupled antiferromagnetically are formed. The amount of the former increases with content of phosphate indicating enhanced binding of water in the granules. The results complement previous experimental data and molecular models for the starch granule with respect to the location and effects of phosphate and crystalline matter.

Amylose↗
PubMed2006

Structural basis for the slow digestion property of native cereal starches.

Native cereal starches are ideal slowly digestible starches (SDS), and the structural basis for their slow digestion property was investigated. The shape, size, surface pores and channels, and degree of crystallinity of starch granules were not related to the proportion of SDS, while semicrystalline structure was critical to the slow digestion property as evidenced by loss of SDS after cooking. The high proportion of SDS in cereal starches, as compared to potato starch, was related to their A-type crystalline structure with a lower degree of perfection as indicated by a higher amount of shortest A chains with a degree of polymerization (DP) of 5-10. The A-type amorphous lamellae, an important component of crystalline regions of native cereal starches, also affect the amount of SDS as shown by a reduction of SDS in lintnerized maize starches. These observations demonstrate that the supramolecular A-type crystalline structure, including the distribution and perfection of crystalline regions (both crystalline and amorphous lamellae), determines the slow digestion property of native cereal starches.

Amylopectin↗
PubMed2001

Photodegradation of cassava and corn starches.

The baking expansion properties of sour cassava starch (Polvilho azedo) are attributable to photochemical starch degradation induced by heterolactic fermentation after sun-drying. This study investigated the effects of UV irradiation on the different structural levels of cassava starch as compared to those of corn starch and dextrins. Photosensitive compounds excited at 360 and 290 nm in cassava starch were photodegraded when starch was exposed to sunlight or 360 nm irradiation. UV irradiation depolymerized cassava and corn starches, inducing modifications due, at least in part, to a mechanism involving free radicals. Lactic acid was also photodegraded. Photodegradation induced by UV absorption could have been due to fluorescent chromophores found in starches and nonfluorescent chromophores present in glucosidic units.

Cooking↗
PubMed2003

Fine structures and physicochemical properties of starches from chalky and translucent rice kernels.

This work compared the molecular structures and physicochemical properties of starches obtained from chalky and translucent kernels of six rice cultivars. Starch samples were prepared according to a modified alkali steeping method. Crystallinity, pasting characteristics, and thermal properties were studied by X-ray diffraction, rapid viscosity analysis, and differential scanning calorimetry, respectively. Starch molecular size fractions (amylopectin, amylose, and intermediate material) were estimated by high-performance size exclusion chromatography, and the chain length profiles of isoamylase-debranched amylopectin were evaluated by high-performance anion-exchange chromatography with pulsed amperometric detection. Starches from chalky kernels contained less amylose (more amylopectin) and more short branch-chain amylopectin (less long branch-chain amylopectin) compared with the translucent kernel starches. Differences in starch structural features significantly correlated with observed variation in grain translucency, starch X-ray diffraction patterns, thermal properties, and pasting characteristics. Starch synthesis in chalky kernels may slightly favor glucan chain branching over chain elongation.

Amylopectin↗
PubMed2003

A three component interaction among starch, protein, and free fatty acids revealed by pasting profiles.

A three way interaction among starch, protein, and lipid that affects the Rapid Viscoanalyzer (RVA) paste viscosity profile was revealed using a model system composed of isolated sorghum starch, whey protein isolate, and free fatty acids (FFAs) (20:2:1, w/w/w). A prominent cooling stage viscosity peak in the RVA profile was produced when all three components were present in the system, while there was no viscosity peak when either protein or FFA alone was combined with starch. The magnitude of the cooling stage viscosity peak differed with addition of palmitic, oleic, or linoleic acids to starch and protein. Amylose was the major functional molecule of the starch component. Addition of both protein and FFA to starch substantially reduced starch solubility after gelatinization, while solubility was less affected by single addition of FFA and was not affected by protein. Nonspecificity of this interaction phenomenon was demonstrated by similar results using maize starch and other soluble proteins.

Absorption↗
PubMed2004

Characterization of potato leaf starch.

The starch accumulation-degradation process as well as the structure of leaf starch are not completely understood. To study this, starch was isolated from potato leaves collected in the early morning and late afternoon in July and August, representing different starch accumulation rates. The starch content of potato leaves varied between 2.9 and 12.9% (dry matter basis) over the night and day in the middle of July and between 0.6 and 1.5% in August. Scanning electron microscopy analyses of the four isolated starch samples showed that the granules had either an oval or a round shape and did not exceed 5 microm in size. Starch was extracted by successive washing steps with dimethyl sulfoxide and precipitated with ethanol. An elution profile on Sepharose CL-6B of debranched starch showed the presence of a material with a chain length distribution between that generally found for amylose and amylopectin. Amylopectin unit chains of low molecular size were present in a higher amount in the afternoon than in the morning samples. What remains at the end of the night is depleted in specific chain lengths, mainly between DP 15 and 24 and above DP 35, relative to the end of the day.

Chemical Precipitation↗
PubMed2005

In vitro starch digestibility and predicted glycemic index of corn tortilla, black beans, and tortilla-bean mixture: effect of cold storage.

People in the rural areas of Mexico consume corn tortillas and beans as basic components of their diet. However, little is known about the nutritionally relevant features of starch present in such combined meals. The objective of the present study was to evaluate the in vitro bioavailability of starch in tortilla-bean mixtures stored at 4 degrees C for different times, as compared to that of corn tortilla and boiled black beans kept separately under the same conditions. Available starch (AS), resistant starch (RS), and retrograded resistant starch (RRS) contents were measured. The in vitro starch hydrolysis indices (HI) of freshly cooked and cold-stored samples were evaluated using a chewing/dialysis digestion protocol. HIs were used to predict glycemic indices (pGI) of the samples. AS in tortilla and beans decreased between 3 and 6% after 48-72 h, whereas values in the mixture fell by 3% after 48 h, with no further change by 72 h. Only minor rises in RS contents (1.5-1.6%) were recorded for tortilla and beans after 72 h of storage, and a lower increase (0.4%) was recorded in the mixture. Judging from RRS values, an important proportion of RS is due to starch retrogradation. The HI and pGI were higher in tortilla than in bean and the mixture. Hydrolysis rate values decreased in the stored samples, a pattern that corresponded with RS and RRS changes. The slow digestion features of common beans are largely retained by the legume-tortilla combination. Data support the perceived health beneficial properties of starch in this traditional cereal-legume food.

Cold Temperature↗
PubMed2005

Effect of storage time on the retrogradation of banana starch extrudate.

Starch was isolated from banana starch and the retrogradation phenomenon was studied using diverse techniques, including an enzymatic measurement. Wide-angle X-ray scattering (WAXS) showed that the sample stored for 7 h presented small peaks and when the storage time increased the peaks increased in intensity. The type of diffraction pattern found in banana extrudates is typical of the A-type crystal polymorph. The crystallinity index from the diffractograms, showed a plateau after approximately 20 h of storage. The short-range order measurement with Fourier transform infrared (FTIR) spectroscopy showed that banana starch retrogradation reached a maximum value at approximately 11 h of storage, a value that agrees with the results obtained with differential scanning calorimetry (DSC), because the maximum enthalpy value (approximately 5 J/g) was calculated in the stored sample for 8 h, without changes in the stored samples for more time. Retrograded resistant starch values did not change after 12 h of storage, obtaining the maximum starch retrogradation level. FTIR, DSC, and the enzymatic technique showed the changes at the molecular level in starch during storage; in the case of WAXS, they determine the long-range order that explains the differences found in the starch retrogradation pattern measurement in banana starch.

Calorimetry, Differential Scanning↗
PubMed2005

Influence of lipid extraction process on the rheological characteristics, swelling power, and granule size of rice starches in excess water.

The influence of the lipid extraction process on both macroscopic and microscopic characteristics of nonwaxy rice starch gelatinization in excess water was examined. Surface lipids extraction did not change the thermodynamics of starch gelatinization but lead to a significant reduction (33%) in the enthalpy of starch-lipid complex melting at high temperature, resulting in less viscous dispersions. Internal lipid extraction using hot aqueous alcoholic solutions resulted in an irreversible increase in starch granule diameter (50% increase in D[4,3]) and a dramatic change in cooking characteristics of the starch. Instead of the bimodal swelling observed for native nonwaxy rice starch, only one broad transition in swelling, solubility, granule size, and viscosity was observed in the case of the totally defatted starch. While the total removal of lipids resulted in a slight increase in starch swelling at intermediate temperatures, the harshness of the process caused irreparable changes leading to notably lower swelling at high temperatures.

Calorimetry, Differential Scanning↗
PubMed1999

Isolation and partial characterization of banana starches.

Two varieties of banana green fruit growing in Guerrero, Mexico, were used for starch isolation. Chemical analysis and physicochemical and functional properties were studied in these starches. The "macho" variety presented higher starch yield than "criollo". In general, chemical compositions in both starches were similar, except in ash content, where the "criollo" variety showed a lower value than "macho". The results of freeze-thaw stability suggested that banana starches cannot be used in frozen products. Both starches presented similar water retention capacity values that increased when temperature increased. Solubility profiles showed that at low temperature "criollo" had lower solubility than "macho", but at higher temperature an inverse behavior was evident; also the solubility increased when temperature increased. Behavior similar to that for solubility was obtained in the swelling test. The banana starch studies indicate the "macho" and "criollo" varieties have different starch structures as evidenced by viscosity.

Fruit↗
PubMed2000

Thermal and physicochemical properties of rice grain, flour and starch.

Three types of rices, namely, Thailand rice (Indica), Nipponbare (Japonica), and Himenomochi (Japonica waxy), in grain, flour, and starch forms have been studied for their thermal and physicochemical properties. In grain form, Indica was slender and Japonica rices were bold and thick. Indica had the highest protein and amylose equivalent. Protein contents in isolated starches varied from 0.2 to 0.9%. Cooked Indica grain was hardest and waxy rice was softest; stickiness was highest in Japonica rice. Glass transition temperature (T(g)) was highest in Indica rice flour (approximately 222 degrees C) and almost the same in Japonica rice flours. Melting point was highest for Japonica (approximately 264 degrees C) and almost the same for Japonica waxy and Indica rice flours. T(g) values of starches were almost the same in Indica and Japonica waxy (approximately 237 degrees C); defatting caused reduction in this property in all of the starches. Highest melting point was shown by Indica starch (approximately 276 degrees C) and was almost the same for the other two starches. Protein and fats play a critical role in glass transition and melting points of rice flours and their respective starches. Viscosities of the cooked pastes of flour and starch during cooking in an RVA instrument and their gel and other properties have been discussed.

Calorimetry, Differential Scanning↗
PubMed2000

Effect of sucrose on the thermomechanical behavior of concentrated wheat and waxy corn starch-water preparations.

The rheological behavior of concentrated starch preparations from two different origins (wheat and waxy corn) was studied in the presence of sucrose by dynamic mechanical thermal analysis (DMTA). Moisture contents ranged from 30 to 60% (w/w wsb), and samples contained 0, 10, or 20 g of sucrose for 100 g of the starch-water mixture. The storage modulus (G') changes during heating depended strongly on water content (in the moisture range studied), and the importance of these variations was dependent upon the starch type. Sucrose addition resulted in a shift to higher temperatures of the increase in G' during heating. Differential scanning calorimetry (DSC) and electron-spin resonance (ESR) analyses were performed in parallel in order to relate the viscoelastic changes to water migrations and to structural disorganization of starch. Sucrose was found to increase the gelatinization temperature and enthalpy of both starches, implying a stabilization of the granular structure during heating. The sugar-water interactions do not appear to be the only way by which sucrose delays starch gelatinization. The obtained results suggest that sugar-starch interactions in the amorphous and/or the crystalline regions of the starch granules should be envisaged.

Calorimetry, Differential Scanning↗
PubMed2000

Rheological and physicochemical properties of starches from moist- and dry-type sweetpotatoes.

Although starch makes up from 50 to 70% of sweetpotato (SP) dry matter, its role in cooked texture is unknown. The purpose of this research was to characterize raw starches isolated from SP cultivars and experimental selections (C/S) with a wide range of textural properties when cooked and to investigate the relationship between textural properties of the cooked roots and characteristics of the isolated starches. Shear stress measured by uniaxial compression of cooked SP cylinders served as an objective measure of SP texture. Starches were isolated from C/S representing three SP texture types: moist (Jewel and Beauregard); intermediate (NC10-28 and NC2-26); and dry (NC6-30 and NC8-22). The following parameters of isolated starches were measured: amylose content by colorimetric and differential scanning calorimetric (DSC) methods; swelling power, solubility, gelatinization enthalpy (DeltaH), and pasting properties by Brabender amylograph (BA) and rapid viscoanalyzer (RVA). Pasting temperatures for SP C/S measured by BA and RVA were significantly correlated. Due to high shear degradation in RVA, RVA viscosities of starch suspensions decreased as much as 40% during cooking at 95 degrees C, whereas the BA viscosities changed little at this temperature. There were no statistically significant differences among the C/S for amylose or DeltaH. However, significant C/S differences in swelling power, solubility, and pasting properties were observed. Although differences in some rheological and physical properties were observed for C/S starches, shear stress was statistically correlated only with DSC onset temperature (r = 0.78), indicating that factors other than the properties measured on isolated starches are mainly responsible for the texture of cooked SP C/S.

Calorimetry, Differential Scanning↗