Starch Related Changes in Stored Soft Sorghum Porridge

Soft sorghum (Sorghum bicolor (L.) Moench) unfermented porridge was prepared by cooking pearled sorghum flour (6% solids in water) in a microwave oven. Fermented porridge was prepared by mixing with Lactobacillus delbruekii for 12 hr at 48°C. followed by cookine. Porridge was aged (0–12 hr) at 25°C or 7.5%. Starch polymer solibility was determined by high performance size exclusion chromatography (HPSEC) and rheology followed with a rotational viscometer. During aging, solubilized and gelled amylose and amylopectin retrogradation rates were higher in porridge stored at 7.5 than at 25°C. Amylose polymer solubility decreased with storage, while solubilized amylopectin remained in solution. Fermented porridges were lighter in color and their initial consistency indexes increased faster. HPSEC of soluble polymers was more sensitive than enzymatic starch digestion.     

Chemical and physicochemical properties of dried wet masa and dry masa flour

Commercial ‘masas’ and dry ‘masa’ flours (DMFs) were evaluated for chemical composition, water retention capacity (WRC), gelatinization, retrogradation and X‐ray diffraction. Both masas and DMF had similar chemical compositions. The masas had higher soluble carbohydrate contents and lower WRCs than DMF. In the same way, DMFs had lower gelatinization temperatures and enthalpies of gelatinization than masas. These results were confirmed by X‐ray diffraction analysis showing a lower degree of crystallinity in DMFs than in masas. The melting temperature in retrogradated samples of both masas and DMFs had a tendency to increase as storage time increased. This increment was more apparent with the enthalpy of melting. These results were probably associated with crystal perfection during starch retrogradation, ie recrystallization of gelatinized starch occurred as a time‐dependent process. Copyright © 2003 Society of Chemical Industry     

Gelatinization and Solubility Properties of Commercial Oat Starch

Gelatinization and solubility characteristics of starch contribute to unique functionality in foods. Corn and oat starch viscoamylographs (35g db) showed peak viscosities of 400 and 390B.U., respectively. Oat starch had a more rapid (89.7 vs 85.6°C) and higher set back (790 vs. 740B.U.) than corn. Data on soluble components of cooled (85°C) starch pastes, as collected and analyzed by high-performance size exclusion chromatography (HPSEC), suggest that amylopectin plays a significant (P<0.05) role in oat paste set back; for corn starch, amylose is the dominant factor. Solubilities and apparent molecular weights (MW) of oat starch heated (65-120°C) under shear and subsequent sonication (0-40s) in water or 90% methyl sulfoxide (DMSO) were also determined by HPSEC. An intermediate MW fraction was eluted on the HPSEC chromatograms only when oat starch was heated in water (100-120°C/30min) or DMSO and sonicated, suggesting that this fraction may not be inherent in the native granule. in water, polymer solubility and peak MW increased with temperature (65-120°C), whereas in DMSO, solubility decreased with heating (65-100°C), while peak MW remained basically constant. Aqueous (aq) leaching at 75°C solubilized more corn amylose than amylopectin, but amylopectin and amylose co-leached from oat starch granules. Aq leaching, at 20°C above their DSC peak ends (85 and 95°C for oat and corn, resepctively), showed more amylopectin leached from oat starch granules whereas more amylose was leached from corn starch granules.     

EVALUATION OF THE RHEOLOGICAL PROPERTIES OF FRESH CORN MASA USING SQUEEZING FLOW VISCOMETRY: BIAXIAL EXTENSIONAL VISCOSITY1

Alkaline corn was cooked for 20, 55 or 80 min, and the nixtamal was ground into masas with medium or coarse particle size distributions. Water was added to each corn masas in order to obtain the same adhesiveness. Rheological properties of these masas were evaluated with the squeezing flow viscometry technique with lubrication at crosshead speeds of 0.05, 0.2 and 0.5 cm/min, respectively. From the data collected, stress-strain and biaxial elongational viscosityradial extension rate curves were obtained. All the fresh corn masas gave the same stress and elongational viscosity at any given specific strain and radial extension rate, respectively, regardless of the cooking time and degree of grinding. The elongational viscosity could be useful to predict fresh corn masa behavior during molding and cutting steps in the tortilla-making process.     

Solubility Behavior of Granular Corn Starches in Methyl Sulfoxide (DMSO) as Measured by High Performance Size Exclusion Chromatography

The extent of corn starch dispersibility and the relative molecular solubility of amylose and amylopectin in methyl sulfoxide (DMSO) were determined. Granular corn starches with <l, 25, 53, and 70% amylose were dispersed in 0–100% DMSO (in water) solutions at 30°C for 30 min. Maximum dispersibility for all starches (98%) was obtained when 90% DMSO/10% water was used; regular (normal) dent corn starch was equally dispersed in solutions with 88–94% DMSO. Molecular solubility, the presence of individual molecules of amylose and amylopectin, of starches was also measured (after centrifugation and filtration) by high performance size-exclusion chromatography (HPSEC). Starches were dispersed in 90% DMSO and heated for 10 min at temperatures of 35–120ºC. At low temperatures, high coefficients of variation resulted from additional DMSO solubilization after treatment. At 120ºC, 70% amylose starch was >90% solubilized, while waxy starch was only 47% solubilized. When starches were treated for 18–89 h in 90ºC DMSO, solubility stopped increasing after 67 h. High amylose starch (70%) was mostly solubilized, but 53% amylose, waxy and regular starches could only be fully solubilized after exposure to shear. Amylopectin molecules appeared more susceptible to shear induced depolymerization than amylose. The percent amylopectin in the high amylose starches reflected that as determined by iodine binding analysis and the manufacturer; while the percent amylopectin in regular starch was too low (manufacturers: 75%, HPSEC: 65%). Undispersed components were mostly amylopectin. Since amylose is fully solubilized, however, the HPSEC can be used to quickly determine percent amylose in starch.     

20种高粱淀粉特性

对我国高粱主产区的20 种高粱淀粉的微观结构、物理特性、糊化回生特性及热特性进行比较研究。结果表明：高粱淀粉颗粒多数为不规则形状,表面内凹,颗粒较大,其中部分颗粒表面有类蜂窝状结构,少数为球形,表面光滑,颗粒小,淀粉颗粒粒径在5～20μm 之间;不同品种高粱淀粉的直链淀粉含量、物理特性、糊化回生特性及热特性差异较大。因此,不同的加工目的应该选择不同的高粱品种。     

Effect of cooking time and ingredients on the performance of different starches in white sauces

The effect of white sauce ingredients and increased cooking time at 90 °C on the degree of gelatinization of corn, waxy corn, rice, potato and modified waxy corn starches was studied. The changes in pasting properties, linear viscoelastic properties, and microstructure were determined. In all the native starches in water, a longer cooking time at 90 °C caused greater starch granule swelling and more leaching of solubilized starch polymers into the intergranular space. These effects were more noticeable in the waxy corn and potato starches. The potato starch was the most affected, with complete disruption of the starch granules after 300 s at 90 °C. The microstructural changes which transformed a system characterized by starch granules dispersed in a continuous phase (amylose/amylopectin matrix) into a system with an increase in the continuous phase and a decrease in starch granules were associated with a decrease in system viscoelasticity. The elastic moduli were higher in the sauce than in the starch in water system. However, with the exception of potato starch, the white sauce showed lower viscoelasticity than the starch in water system. The white sauce ingredients decreased the effect of cooking time on the starch gelatinization process, particularly in potato starch.     

Laboratory Wet‐Milling of Grain Sorghum With Abbreviated Steeping to Give Two Products

Short‐time and no‐time steeping were used in the wet‐milling of grain sorghum to give two products, starch in over 78% recovery (starch basis) plus the remaining grain solids. In the wet‐milling process 1.5 parts of fresh water were used per part of grain to compensate for drying and transfer losses. Starting with 100 g (dry solids) of commercial No.2 grain sorghum, steep time (1—3 h), steep temperature (25—60 °C), and coarse‐grinding speed (7, 500—12, 500 rpm with tip speed of 90.4—150.7 km/h) were varied in a model study; starch recovery, starch lightness (L*), and damaged starch were the responses. Grain sorghum was steeped with twice its weight of process water containing 0.2% sulfur dioxide and the steeped kernels were added to an equal volume of process water and the mixture was ground for 6 min in a Waring blender with blunt blades (d = 3.2 cm). The course‐ground material was sieved (opening 1190 μm) to collect the bran/germ, and the throughs were allowed to stand. The sedimented phase was finely ground by one pass through a plate mill, and the fine fiber removed by sieving (opening 73 μm). The slurry was adjusted to a specific gravity of 1.04, and the starch was separated from the protein fraction on a starch table. The protein fraction was combined with the steep‐liquor concentrate (54% solids) plus the bran/fiber and the fine‐fiber fractions to give the co‐product, which contained 70% moisture (wet basis, wb) and 27% protein (dry basis, db). In the surface response study, recovery of starch ranged from 57 to 89%, starch protein content from 0.4 to 0.5%, and lightness (L*) from 90 to 93. Damaged starch content was constant at around 0.4%. Commercial grain sorghum gave the highest starch recovery (90%) after steeping 2 h at 55 °C and coarse‐grinding at 10, 500 rpm; whereas a food‐grade, a white and a red sorghum gave 85, 84, and 80% recoveries, respectively. The four starches had lightness (L*) values of 93—94 and damaged starch contents of 0.4—0.6%. When the commercial grain sorghum was wet‐ground without steeping in 2 parts of water containing 0.2% sulfur dioxide, a 78% recovery of starch was obtained with L* 93.7 and starch damage 0.5%.     

Effect of Cooking Time,Steeping and Lime Concentration on Starch Gelatinization of Corn During Nixtamalization

White dent corn was nixtamalized under different conditions to evaluate thermal properties using differential scanning calorimetry (DSC), swelling power and solubility. Cooking time was the factor that had the major influence on the behavior of the evaluated parameters as indicated by the analysis of variance. Onset and peak temperatures of gelatinization increased with increasing cooking time while gelatinization enthalpies decreased, indicating that more starch granules were gelatinized. A decrease in the swelling power was also observed at increasing cooking times, but solubility was significantly inhibited only if steeping was allowed. Considering these results, it was assumed that amylose‐lipid complexes are being formed during cooking and reorganized during steeping. X‐ray studies confirmed the presence of amylose‐lipid complexes. Steeping also caused an increment in the peak temperature that seemed to support the hypothesis of recrystallization or annealing occurring during this nixtamalization step. Temperature ranges indicated that in general, lime acted as a factor for structural disorganization.     

Changes in Corn and Sorghum During Nixtamalization and Tortilla Baking

Structural changes occurred in corn and sorghum during the alkaline-cooking process as it progressed from the raw kernel to the tortilla. The alkali weakened the cell walls, facilitating the removal of the pericarp, solubilized cell walls in the peripheral endosperm, caused swelling and partial destruction of starch granules, and modified the physical appearance of the protein bodies. Masa (ground nixtamal) consisted of small pieces of germ, pericarp, aleurone and endosperm, and free starch granules, cell fragments, and dissolved or dispersed solids and lipids in water. During tortilla baking, an additional degradation of cell walls, further loss of starch crystallinity, and partial destruction of protein bodies occurred.     

Thermal and rheological properties of hydrogels prepared with retrograded waxy rice starch powders

Waxy rice starch dispersed in water (50% solids) was gelatinized by heating the dispersion at 121°C for 20 min, and retrograded by storing the paste at 4°C for 2 days. The starch gel was then freeze-dried and ground into powders. The retrograded starch powders were hydrated at 20–30% solid concentration at different temperatures (4 and 23°C), and then thermal and rheological properties were analyzed using the hydrogels. The gel hydrated at 4°C had an onset temperature of melting at 34.9°C, which was approximately 10°C lower than that observed for the gel hydrated at 23°C. The enthalpy value was greater for the gel hydrated at 4°C (14.2 J/g) than the gel hydrated at 23°C (8.8 J/g). The yield stress and consistency of the hydrogels were proportional to the solid concentration. The hydrogel prepared with 30% retrograded starch powders at 4°C displayed a thick creamy texture with retrograded starch crystals that could melt at a temperature range of 35–51°C. The thermal and rheological properties of the hydrogels exhibited the possibility for the retrograded starch powders to be used as fat mimetic in foods.     

Physical Properties of Starches Isolated from Yellow Corn,Sorghum, Sordan and Pearl Millet

Water-binding capacity, swelling power and solubility, amylograph viscosity, relative, specific, reduced and intrinsic viscosities of starches isolated from yellow corn, sorghum (Giza 3 and 114), Sordan 79 and pearl millet were investigated. Yellow corn and pearl millet starches were characterized by their higher water binding capacities. Pearl millet starch showed higher initial transition temperatures (about 91°C) to be gelatinized than the other starch which gelatinized at initial transition temperature ranging from 66 to 70°C. Differences in maximum viscosities expressed as Brabender units were also ranging from 780 to 185 BU. On the other hand, slight differences in intrinsic viscosity were observed.     

红小豆淀粉理化性质研究

以红小豆为材料,采用水磨法提取红小豆淀粉,以玉米淀粉、红薯淀粉作对照,对其颗粒特性以及糊化黏度特性等理化特性进行研究。实验结果表明,红小豆淀粉颗粒呈椭圆卵形,颗粒完整,表面光滑,粒径较长,偏光十字明显,具有类似树木年轮的轮纹结构,脐点位于颗粒中心。与对照相比,红小豆淀粉具有较低的糊化温度,较高的糊黏度,较差的冷热稳定性,易发生老化。pH、蔗糖对红小豆淀粉糊的黏度性质有影响。     

20种蚕豆淀粉物理特性、糊化回生特性与粉丝品质的关系

对20种中国主产区蚕豆淀粉粉丝烹煮品质和感官品质进行了评价,并对蚕豆淀粉的物理特性指标、糊化回生指标与相应的粉丝品质进行相关性分析。淮安大蚕豆等5个蚕豆品种的淀粉制作的粉丝品质最好,而青海马牙等3个蚕豆品种的淀粉制作的粉丝品质较差。蚕豆淀粉部分物理特性指标与粉丝品质的密切相关表现在:持水性越低,溶解度越低,膨润力越低,粉丝品质越好。淀粉的冻藏缩水率、透光率与粉丝的烹煮、感官品质指标相关性不大。蚕豆淀粉的RVA参数与其粉丝感官品质指标密切相关,其中衰减度、峰粘度、保持强度等对其影响最大。蚕豆淀粉凝胶强度越大,粉丝的烹煮品质和感官品质越好。在评价蚕豆淀粉品种的粉丝加工适应性时,一方面可以通过测试蚕豆淀粉的溶解度、持水性、膨润力和凝胶强度来预测其粉丝烹煮品质和感官品质的好坏;另一方面可以用RVA测试蚕豆淀粉,预测其相应的粉丝感官品质的优劣。     

Physicochemical and structural properties of starches isolated from corn cultivars grown in Indian temperate climate

Starches isolated from five corn cultivars namely C4, C5, C6, C8, and C15 were investigated for their physicochemical and structural properties. The amylose content of corn starches varied from 24.74 to 30.32 g/100 g among the cultivars. The starch granules showed polyhedral granule shapes and differences in their mean granule size ranged from 2.3 to 19.5 μm. The starch samples showed A-type diffraction pattern with strong reflection at 15.25, 18.11, and 23.33°. Pasting profile, textural, and thermal properties of corn starch showed the cultivar differences. Raman spectroscopy showed the major band intensities at 1340, 1082, 940, 865, 523, 485, 440, and 412 cm^?1. Syneresis and turbidity of gelatinized pastes of starches varied among the cultivars and increased progressively with the increase in storage period. The present study can be used for identifying differences between corn genotypes for starch quality and could provide guidance to possible industries for their end use.     

Corn Masa and Tortillas from Extruded Instant Corn Flour Containing Hydrocolloids and Lime

Extruded instant corn flour (EICF) samples with hydrocolloids (gums), such as gum arabic, carboxymethylcellulose (CMC), guar and xanthan and with different concentrations of lime (0.1, 0.2 and 0.3% w/w) were prepared by extrusion. The gums were added before or after thermal processing. The dehydration process followed through the weight loss (WL) in masa, the physicochemical (water absorption capacity (WAC) and WL during cooking) characteristics of masa were optimized to give longer dehydration times and tortillas with good textural (rollability, tensile strength and cutting force) properties. The lowest effective moisture diffusion coefficient (D*) was found in masa samples containing 0.2% (w/w) of lime and 0.5% (w/w) of the xanthan gum added before extrusion. These masas produce tortillas with optimum textural characteristics and highest yields.     

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

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

A Differential Scanning Calorimetry Study on the Effect of Annealing on Gelatinization Behavior of Corn Starch

Gelatinization characteristics of laboratory-isolated and commercial corn starch were compared by differential scanning calorimetry (DSC) before and after being annealed at subgelatinization temperatures in excess water. Prior to annealing, commercial corn starch has a relatively narrow gelatinization range, with a peak temperature at 71°C. Starches isolated in the laboratory have wide gelatinization ranges and lower peak temperatures. After annealing, commercial starch showed little change in gelatinization characteristics, whereas laboratory starches all had narrowed gelatinization ranges, higher peak temperatures, and increased gelatinization enthalpy, indicating changes in the internal structure of the starch granules. This demonstrates that the wet-milling process anneals corn starch during the isolation procedure.     

Characterization of the agglomeration of roasted shredded cassava (Manihot esculenta crantz) roots

Roasted and granulated cassava roots flour, known as ‘rale’ in the south of Mozambique, is a common meal in sub‐Saharan Africa and is consumed reconstituted with hot or cold water. In this work, analysis of rale was carried out with the aim of understanding what determines the agglomeration properties. Rale is agglomerated roasted cassava flour with about 95% of starch gelatinized. The pre‐gelatinized and agglomerated cassava gives cold swelling as well as a resistance against disintegration when heated. The softness of swollen agglomerated granules is temperature dependent. Microscopy of rale agglomerates shows that the granulation is formed by partial swelled starch granules bound together by retrograded leached AM. A physical model of rale consisting of glass beads agglomerated by drying with an AP or AM solution showed that particles with retrograded AM were resistant to disintegration in water at 90°C while glass beads agglomerated with AP did not show comparable heat resistance. Thus it was concluded that the leaching and retrogradation of AM is essential to obtain the rale agglomeration and functionality.     

Studies on Physicochemical,Pasting Characteristics and Amylolytic Susceptibility of Starch from Sorghum (Sorghum bicolor L. Moench) Grains

Preparation, physicochemical properties, pasting behavior and amylolytic susceptibility of sorghum starch have been investigated. The yield of starch was about 60.25%, on whole grain basis. The starch exhibited double stage swelling and low solubility pattern in an aqueous system. Viscoamylographic studies on pasting behaviour of the starch revealed a peak viscosity of 800 B. U. at 8% (w/v) concentration; however, it decreased considerably during cooking (viz. holding period of 30 min at 93°C). The amylose content of the starch was 23.45%. The gelatinization temperature range was found to be 68.5–72.5–78.5°C. The results indicated that the native starch hydrolyzed to a limited extent by human salivary α-amylase and glucoamylase as compared to gelatinized starch. In addition, the mode of attack by amylolytic enzymes on the native starch granules viewed by SEM has been studied in detail.