Physicochemical Properties of Waxy and Normal Maize Starches Irradiated at Various pH and Salt Concentrations

Waxy and normal maize starches of various pH values and salt contents were prepared, irradiated with gamma rays (5–20 kGy) and their molecular structure, pasting viscosity and rheological properties determined. Average molar mass and size of both waxy and normal maize starches decreased considerably by irradiation from >338.0×10⁶ to <39.4×10⁶ g/mol and from >237.5 to <125.2 nm, respectively. Adjustments of pH had little influence on the average molar mass and size of irradiated starch, whereas incorporation of salt greatly reduced the molar mass and size of irradiated waxy and normal maize starches. As the pH increased from 4 to 8, the pasting viscosity of the irradiated starches decreased from 1032 to 279 mPa s in waxy and from 699 to 381 mPa s in normal starches. Pasting viscosity of both irradiated waxy and normal starch decreased from 689 to 358 mPa s and from 327 to 184 mPa s as the salt concentration increased from 1 to 5%. The G′ of gels, determined during cooling from 90 to 10°C or storage for 8 h, decreased in irradiated waxy and normal starches by pre‐conditioning at pH 8 and in irradiated waxy starches by pre‐conditioning at 5% NaCl. With 5% NaCl, G′ of irradiated normal maize starch during cooling increased up to the irradiation level of 10 kGy, and increased during storage for 8 h at all levels of irradiation. Incorporated salt prior to irradiation appears to induce incremental modifications in the molecular structure, rheological and retrogradation properties of starch by boosting the degradation of molecules.     

Structural,thermal and viscoelastic characteristics of starches separated from normal,sugary and waxy maize

Starches separated from five types of maize (two normal, one sugary and two waxy) were investigated for physicochemical, thermal, amylopectin structure and viscoelastic properties. Kisan and Paras were normal maize while Parbhat and LM-6 were waxy maize type. Apparent amylose content of normal and sugary maize was 29.5–32.6 and 41.0%, respectively. Swelling power of normal, sugary and waxy maize starches was 11.6–15.2, 7.8 and 30.2–39.2 (g/g), respectively. X-ray diffraction of maize starches indicated typical A-pattern. Maize starch showed a single broad peak at 2θ=23.2° and a dual peak 2θ=17°–18.1, respectively. Waxy maize starches showed the presence of greater crystallinity than other starches while sugary maize starch showed the presence of lower crystallinity and a large amount of amylose–lipid complex. Intrinsic viscosity [η] of starches in 90% DMSO at 25 °C was 79.7–119.5 ml g⁻¹ for normal, 70.5 ml g⁻¹ for sugary and 107.2–118.1 ml g⁻¹ for waxy starches. Branch chain–length distribution of amylopectin revealed that the apparent amylose, long side chain- and short side chain-amylopectin proportion ranged between 0.0–41%, 13.4–31.5% and 41.5–66.8%, respectively, among the various maize starches. Maize sugary showed the highest apparent amylose content and the least amount of short- and long-side chains of amylopectin. LM-6 and Parbhat showed higher proportion of both long- and short-chain amylopectin as compared to other starches. Distribution of α-1, 4-chains of amylopectin (short-/long-chain) ranged between 2.1 and 3.4, the least for LM-6 and the highest for Paras starch. The transition temperatures (T_o–T_c) ranged between 60.5 and 76.1 °C for sugary, 63.5–76.3 °C for normal and 64.4–81.3 °C for waxy maize starch. The enthalpy of gelatinization (ΔH_gel) of sugary, normal and waxy maize starches was 2.47, 3.7–4.75 and 4.15–5.4 J/g, respectively. Normal and sugary maize starches showed higher G′ and G″ than waxy type starches. The change in the moduli during cooling and reheating of pastes cooked at different temperatures revealed low disintegration of granular structure in starch with higher amylose and amylose–lipid complex as well as low crystallinity. The changes in moduli during 10 h at 10 °C revealed highest retrogradation in maize sugary followed by Paras and Kisan starch.     

Honey Amylase Activity and Food Starch Degradation

ABSTRACT: Honey amylase was evaluated for potential to degrade food starch and cause viscosity loss. Honey was assayed for amylase activity with diastase number (DN). A viscosity assay, developed with unmodified waxy maize starch, measured honey amylase rate of viscosity decrease (RVD). The relationship between DN and RVD was linear (R²= 0.98). Modified waxy maize starches showed resistance to honey amylase. Honey heat treatment at 85 °C reduced amylase activity 2 to 5 DN, but confirmed enzyme heat resistance. Optimum pH for honey amylase was confirmed at pH 5.3 to 5.6. RVD activity declined as pH decreased. Preventing food viscosity loss involved selecting honey with lowered DN and/or using modified starches. Complete control of activity was achieved in barbecue sauce at pH < 3.9.     

In vitro Digestibility of Hydroxypropyl Maize,Waxy Maize and High Amylose Maize Starches

Hydroxypropyl derivatives of maize, waxy maize and high amylose maize starches were prepared and characterized. The in vitro digestibility of the raw and gelatinized starches and their derivatives was compared using porcine pancreatic α-amylase. Digestibility of the unmodified starches decreased in the order waxy maize > maize > high amylose maize. Increasing molar substitution (MS) caused a decrease in digestibility for all starch types after gelatinization. Raw maize and high amylose maize starch derivatives showed an initial decrease in digestibility followed by increases at higher MS levels. The digestibility of the raw waxy maize starch derivatives showed a continuing drop as MS increased.     

蜡质玉米淀粉的凝胶化性质及其在陶瓷凝固成型中的应用研究

本文对蜡质玉米淀粉的糊性质、流变特性和凝胶强度等凝胶化性质进行了详细研究。结果表明：与普通玉米淀粉相比，蜡质玉米淀粉易糊化，热粘稳定性差，冷粘稳定性好，凝胶强度低；蜡质玉米淀粉糊属假塑性流体，且糊的表观粘度受淀粉浓度、温度和pH值的影响。利用蜡质玉米淀粉的凝胶化性质可实现Al2O3陶瓷的原位固化成型，且成型的陶瓷坯体外观光洁、平整、无缺陷，坯体的密度高、线收缩率低。     

Effect of acid hydrolysis in the presence of anhydrous alcohols on the structure,thermal and pasting properties of normal,waxy and high‐amylose maize starches

Maize starches with different amylose contents (0%, 23% and 55%) were treated in anhydrous methanol, ethanol, 2‐propanol, 1‐butanol with 0.36% HCl at 25 °C for 5 days. Results showed that the extent of change in physicochemical properties increased from methanol to butanol. Treated waxy maize starch showed higher than 65% solubility at above 75 °C. The diffraction peak at 2θ = 5.3° of amylomaize V starch disappeared after treatment in ethanol, 2‐propanol and 1‐butanol. Acid–alcohol treatment decreased the gelatinisation temperature of normal (from 64.5 to 61.9 °C) and waxy maize (from 68.1 to 61.1 °C) starches, while it increased that of amylomaize V (from 68.7 to 72.3 °C) starch. The extent of the decrease in the pasting viscosity followed the following order: amylomaize V < normal maize < waxy maize. This study indicated that acid–alcohol treatment degraded preferentially the amorphous regions and the different changes depended on the crystal structure and amylose content of starch.     

Molecular Background of Technological Properties of Selected Starches

Selected starches, i.e. waxy maize, amaranth, quinoa, wheat, millet and buckwheat starches, were investigated with respect to their technological properties such as gelatinization, stability to mechanical stress, resistance to conditions and stability in continuous freeze/thaw cycles. Technological properties are correlated with molecular features such as branching characteristics in terms of iodine-complexing potential, molar mass, occupied glucan-coil volume, packing density of glucan coils and rheological properties. Waxy maize and amaranth starches were found to be amylopectin-type short-chain branched (scb) glucans with weight average molar masses M_w = 17 × 10⁶ g/mol and 12 × 10⁶ g/mol, respectively. Waxy maize starch had a high gelatinization potential, high viscosity at 95 °C (340 mPas) low stability at acidic conditions, average stability to shearing and good freeze/thaw stability. For amaranth starch a viscosity of 122 mPas at 95 °C, low resistance to acid, but high stability to applied shearing and even high freeze/thaw stability was determined. Investigated quinoa starch was classified as scb-type glucan, however, the branches are significantly longer than those of waxy maize and amaranth. With a M_w = 11 × 10⁶ g/mol and a viscosity of 187 mPas at 95 °C, this sample is comparably resistant to acidic conditions and to shearing, but instable in freeze/thaw experiments. Wheat, millet and buckwheat starches contain significant percentages of amylose-type long-chain branched (lcb) glucans (22.1, 32.1 and 24.3 %, respectively) with M_w values of 5 × 10⁶ g/mol, 12 × 10⁶ g/mol and 15 × 10⁶ g/mol, respectively. Wheat starch, with a viscosity of 107 mPas at 95 °C, shows low stability under acidic conditions, but high stability to shearing. Wheat and millet starches, but not buckwheat starch, form weak gels in the course of subsequent freeze/thaw cycles. Millet starch, with a viscosity of 101 mPas at 95 °C was found to be moderately stable under acidic conditions and to shearing. Buckwheat starch with a viscosity of 230 mPas at 95 °C shows no acid resistance and is instable upon shearing but performs very well in freeze/thaw experiments.     

Studies on Starch Phosphates. Part 3. On the Esterified Phosphates in Some Cereal Starches

Some cereal starches were investigated whether glucose phosphate residues were in the polysaccharides. Significant amounts (6–15 ppm, as P) of glucose 6-phosphate were found in the acid hydrolysates of corn, waxy corn, rice and waxy rice starches. After the extensive action of bacterial α-amylase on these starches phosphorylated oligosaccharide (α-LPD) was recovered in reasonable yield by a DEAE-Sephadex column chromatography. The α-LPDs prepared from two sources of waxy rice starch contained 81.8 and 94,3% of P₀ at the 6th position of glucose residues and the rest of P₀ at the 2nd and/or 3rd positions of glucose residues. All these results show that these starches have glucose phosphate residues. In wheat starch, however, no evidence for the presence of glucose phosphate residues has been obtained.     

Cross-linking of corn starch with phosphorus oxychloride under ultra high pressure

To investigate the effect of UHP treatment on the cross-linking reaction, normal corn starch was subjected to UHP-assisted reaction with a single addition level of POCl₃, at varied pressure levels ranging from 0.1 to 400 MPa. Swelling power, gelatinization, and pasting properties were assessed for all native and cross-linked starches. UHP-assisted reaction achieved a 12.5% level of conventional reaction time. UHP-assisted POCl₃ starch derivatives, reacted at 100–400 MPa, exhibited reduced swelling powers and gelatinization properties relative to that at 0.1 MPa, though both attributes did not possess any tendency depending on pressure levels. UHP-assisted POCl₃ reaction generated pasting viscosity profiles similar to those observed for conventional cross-linked starches. Pasting viscosity profiles were significantly different among various UHP treatments, though no trends were present. At 400 MPa, the UHP-assisted POCl₃ starch derivative revealed pasting viscosity profiles most similar to those of the conventional POCl₃ starch derivative.     

Effect of Cross Linking on Functional Properties of Cationic Corn Starch

Native corn starch was cross linked with phosphorus oxychloride (POCl₃) before and after cationization to DS 0.04 in an aqueous ethanolic-alkaline solvent with no adverse effects on the cationization reaction rate. Cross linking at six levels of POCl₃ (7.5–120μ1/50g starch) demonstrated that the gelatinization temperatures of cationic starch increased but enthalpies of gelatinization (ΔH) decreased in proportion to the amount of added POCl₃. Amylograph viscosities increased with level of POCl₃ up to a maximum of 45μl POCl₃ and then decreased markedly at higher concentrations of POCl₃. At 30–45μl POCl₃, the amylograph viscosities of cationic corn starch increased very rapidly and remained uniformly high throughout the rest of the heating and cooling cycle. At this level of cross linking and cationization, the modified starch could be used industrially as an adhesive or in paper manufacture at more dilute concentrations and with less energy input for mixing the slurry than would be required for cationic starches which exhibit high peak viscosities but negative setbacks on cooling.     

Comparative Studies on Some Physico-chemical, Thermal, Morphological, and Pasting Properties of Acid-thinned Jicama and Maize Starches

Comparative studies on acid hydrolysis of jicama and maize starch were carried out using concentrations of hydrochloric acid of 1.5%, 3.0%, and 4.5% (w/v), for 3 and 6 h, at 40°C. Native maize and jicama starches showed important morphological, thermal, and structural differences from those of tubers and cereals which potentially offer diverse industrial applications. Jicama starch showed low amylose content (12%) and small size of starch granules. Due to these characteristics, jicama starch was more susceptible to degradation during hydrolysis process than maize starch. Under the experimental conditions employed, the acid degradation was not particularly severe, as shown by scanning electronic microscopy analysis which showed small degraded zones and similar X-ray patterns in both starches. However, jicama starch was more susceptible to acid hydrolysis than maize starch, as revealed by the considerable increase in water solubility index, damaged starch, and crystallinity values. Also, the higher susceptibility of jicama starch than maize starch to the hydrolysis conditions was reflected in the sugar content release during hydrolysis. The relative crystallinity of hydrolyzed maize starches decreased during hydrolysis, while those of hydrolyzed jicama starches increased attributable to the lower amylose content of jicama starch in relation to maize starch. Maize and jicama hydrolyzed starches showed low viscosity values with relation to their native starch counterparts. However, native jicama starch showed lower viscosity values than maize starch, suggesting a lower internal stability of the starch granules during hydrolysis. Both native and hydrolyzed maize starches showed higher enthalpy, T _o, T _p, and T _c values than jicama starch and the broadening of the endotherms decreased during the hydrolysis of both starches.     

Endosperm Structure and Physicochemical Properties of Starches from Normal,Waxy, and Super-Sweet Maize

Maize is a main botanical source used for extraction of starch in the world market. New maize cultivars with different amylose contents and special starch metabolism characteristics have been generated. Three types of maize cultivars, namely, normal maize, waxy maize (wxwx homozygous mutant), and super-sweet maize (sh2sh2 homozygous mutant), were investigated to determine differences in endosperm structures, morphologies, and physicochemical properties of starches. Maize kernels exhibited significantly different contents of total starch, soluble sugar, and amylose. Normal maize kernels contained the largest proportion of floury endosperm, followed by waxy maize and then super-sweet maize. Normal maize starch and waxy maize starch were larger in size than super-sweet maize starch. Normal maize starch and waxy maize starch were spherical and polygonal in floury and vitreous endosperms, respectively. Super-sweet maize starch was spherical both in floury and vitreous endosperms. Waxy maize starch showed the strongest birefringence patterns, the highest crystallinity and the largest proportion of ordered structure in external region of granules, and the largest proportion of double helix components, followed by normal maize starch and then super-sweet maize starch. Waxy maize starch showed the highest peak viscosity, trough viscosity, breakdown viscosity, gelatinization temperatures (i.e., gelatinization conclusion temperature, gelatinization onset temperature, gelatinization peak temperature, and gelatinization enthalpy). By contrast, super-sweet maize starch showed the lowest corresponding values for these parameters.     

Study of the shear and extensional rheology of casein,waxy maize starch and their mixtures

This work investigated the shear and uniaxial extensional flow behaviour of aqueous casein and phosphated waxy maize starch systems as a function of the deformation rate, biopolymer concentration and the temperature. Trouton ratios were calculated to compare different responses of biopolymers to the shear and extensional deformation. It was found that the casein system (20% w/w) had a much higher and linearly increasing Trouton ratio against the log increase of strain rate. The starch system (35% w/w) had a Trouton ratio close to 3 at low strain rates, but increasing linearly once the strain rate exceeded 2 s⁻¹. The apparent shear and extensional viscosity showed an exponential increase with the concentration for both biopolymers, with casein being more concentration dependent. Their Trouton ratios were also very much concentration dependent: remained close to 3 at low biopolymer levels, but increased significantly at higher concentrations. Temperature variation experiments demonstrated that the flow properties of casein and waxy maize starch follow an Arrhenius relationship, with casein showing stronger temperature dependence than starch. While casein systems displayed a decrease in Trouton ratio with temperature increase, waxy maize starch had the opposite behaviour. The mixing of casein–waxy maize starch resulted in higher apparent extensional viscosities and higher Trouton ratios than single biopolymer systems.     

Wettability, surface microstructure and mechanical properties of films based on phosphorus oxychloride-treated zein

BACKGROUND: Zein, the predominant protein in corn, has been extensively studied as an alternative packaging material in edible and biodegradable films. However, films made from 100% zein are brittle under normal conditions. The aim of this investigation was to improve the film‐forming properties of zein by chemical phosphorylation. The surface hydrophobicity, surface microstructure and mechanical properties of films based on untreated and phosphorus oxychloride (POCl₃)‐treated zein were evaluated and compared. The effect of POCl₃ treatment on the rheological properties of zein solutions was also studied. RESULTS: POCl₃ treatment, especially at pH 7 and 9, led to an increase in the apparent viscosity of zein solutions. Atomic force microscopy (AFM) analysis showed that the film based on POCl₃‐treated zein at pH 7 had a stone‐like surface microstructure with a higher roughness (R_q) than the untreated zein film. The AFM data may partially account for the phenomenon that this film exhibited high surface hydrophobicity (H₀). POCl₃ treatment diminished the tensile strength (TS) of zein films from 4.83–6.67 to 1.3–2.29 MPa. However, the elongation at break (EAB) of the films at pH 7 and 9 increased from 3.0–4.5% (control film) to 150.1–122.7% (POCl₃‐treated film), indicating the potential application of zein films in wrapping foods or in non‐food industries such as sugar, fruit or troche that need good extension packing materials. CONCLUSION: The data presented suggest that the properties of zein films could be modulated by chemical phosphorylation treatment with POCl₃ at an appropriate pH value. Copyright © 2011 Society of Chemical Industry     

Bestimmung der absoluten Viskositäten der Wachsmaisstärke in der Verkleisterungsphase

Determinations of Absolute Viscosities in the Pasting Phase of Waxy Maize Starch. The characteristic data of swelling for a 6% suspension of waxy maize starch were determined in Haake-Rotovisko apparatus at three different rates of stirring velocity. The swelling and pasting of the starch were carried out in the same test vessel. The viscogrammes of waxy maize starch displayed essential differences in comparison with potato, maize and wheat starch. The characteristic differences in the viscogrammes of waxy maize starch are due to the high amylopectin content. In consequence of the structural viscosities of the waxy maize starch paste the maximum viscosities V_max are dependent on the changes of the shear rate D, while the corresponding maximum temperature T_max shows only little dependence of stirring velocity.     

EFFECT OF AMYLASE ACTIVITY ON STARCH PASTE VISCOSITY AND ITS IMPLICATIONS FOR FLAVOR PERCEPTION

The viscosity of starch pastes prepared from waxy maize and wheat starches was measured as a function of concentration. Concentrations at which the two starches had comparable viscosities were selected and the decrease in viscosity with time on amylase addition was determined at 37C using a rapid viscosity analyzer (RVA). At the same level of enzyme addition the decrease in viscosity with time was much faster for waxy maize starch compared to wheat starch. For the latter, the time for the RVA viscosity to be reduced to half its value was of the order of 10 s. Volatile release was substantially increased with amylase addition. It is suggested that, at comparable initial viscosities, starch‐thickened products have better flavor and taste perception than products prepared with other thickeners because of the in‐mouth viscosity decrease resulting from amylase degradation. This could be explained by a reduction in perceived viscosity, which may enhance flavor perception as a consequence of signal processing within the brain, and/or an increase in the concentrations of volatiles reaching the olfactory receptors.     

Physicochemical Properties of Starch Isolated from Bracken (Pteridium aquilinim) Rhizome

Bracken (Pteridium aquilinum) is an important wild plant starch resource worldwide. In this work, starch was separated from bracken rhizome, and the physicochemical properties of this starch were systematically investigated and compared with 2 other common starches, that is, starches from waxy maize and potato. There were significant differences in shape, birefringence patterns, size distribution, and amylose content between bracken and the 2 other starches. X‐ray diffraction analysis revealed that bracken starch exhibited a typical C‐type crystalline structure. Bracken starch presented, respectively, lower and higher relative degree of crystallinity than waxy maize and potato starches. Ordered structures in particle surface differed among these 3 starches. The swelling power tendency of bracken starch in different temperature intervals was very similar to that of potato starch. The viscosity parameters during gelatinization were the lowest in waxy maize, followed by bracken and potato starches. The contents of 3 nutritional components, that is, rapidly digestible, slowly digestible, and resistant starches in native, gelatinized, and retrograded starch from bracken rhizome presented more similarities with potato starch than waxy maize starch. These finding indicated that physicochemical properties of bracken starch showed more similarities with potato starch than waxy maize starch.     

Material Properties and Glass Transition Temperatures of Different Thermoplastic Starches After Extrusion Processing

Four different starch sources, namely waxy maize, wheat, potato and pea starch were extruded with the plasticizer glycerol, the latter in concentrations of 15, 20 and 25% (w/w). The glass transition temperatures of the resulting thermoplastic products were measured by Dynamic Mechanical Thermal Analysis (DMTA). Beside mechanical and structural properties also the transition temperatures of the materials were evaluated during tensile and impact tests. Above certain glycerol contents, dependent on the starch source, a lower glass transition temperature T_g resulted in decreased modulus and tensile strengths and increased elongations. Lowering the T_g at different glycerol contents did not influence the impact strength. When the amylose/amylopectin ratio increased a decrease in T_g was found. For pea, wheat, potato and waxy maize starch the T_g was 75 °C, 143 °C, 152 °C and 158 °C, respectively. Therefore products with higher percentages of amylose are more flexible. The shrinkage of the specimens made by injection molding was considerable compared to the specimens made by pressing.     

Effects of waxy maize and potato starches on the stability and physicochemical properties of model sauces prepared with fresh beef meat

Stability and physicochemical properties of model sauces containing 2.5 wt% fresh beef meat (related to raw material), 30 wt% rapeseed oil and native waxy maize starch (WMS) or potato starch (PS) at concentrations ranged from 0.5 to 4.0 wt% were assessed. Sauces thickened with WMS showed a significantly (P < 0.05) higher stability than respective ones made with PS. All studied systems exhibited non‐Newtonian, pseudoplastic behaviour. The Ostwald–de Waele and Herschel–Bulkley models were used to describe the flow properties of model sauces. In comparison with control sample (prepared without starch), addition of this polysaccharide (WMS or PS) increased consistency index, yield stress and apparent viscosity and decreased flow behaviour index of model sauces. The Arrhenius equation was used to determine the effects of temperature (20–50 °C) on the apparent viscosity. The activation energy values were in ranges 7.66–10.59 kJ mol^?1 and 8.87–11.82 kJ mol^?1 in sauces prepared with WMS and PS, respectively. The instrumentally detected changes in consistency and whiteness of model sauces were found, which may be used as the good predictors of the perceived sensory consistency and whiteness.     

Starch from hull-less barley: II. Thermal,rheological and acid hydrolysis characteristics

Gelatinization, granular swelling, amylose leaching, viscosity and acid susceptibility characteristics of starches isolated from 10 hull-less barley (HB) genotypes [zero amylose (CDC Alamo), waxy (CDC candle, SB 94794, SB 94912, and SB 94917), normal amylose (Phoenix, CDC Dawn, SR 93102, and SB 94860) and high amylose (SB 94893 and SB 94897)] were monitored by differential scanning calorimetry (DSC), swelling power (SP), solubility, Brabender viscoamylography, and reaction with 2.2 N HCl (at 35 °C), respectively. DSC data showed that T_o, T_p, T_c, T_c–T_o, and ΔH ranged from 50.1–56.1, 58.1–64.5, 71.0–75.8, 17.9–24.0 °C and 9.6–14.2 J/g of amylopectin, respectively. In compound waxy (SB 94917) and compound normal (SR 93102 and SB 94860) starches, T_o and T_c–T_o were lower and higher, respectively, than in the other starches. ΔH followed the order: compound normal>waxy>normal≈zero amylose>high amylose>compound waxy. The SP followed the order: zero amylose>waxy>compound normal>normal>high amylose. A rapid increase in solubility occurred at lower temperatures (<70 °C) for zero amylose HB starch, however, this increase was gradual for the other starches. At 90 °C, solubility followed the order: high amylose>compound normal>normal>waxy. Zero amylose and waxy HB starches exhibited lower pasting temperatures, higher peak viscosities, and higher viscosity breakdown than normal HB starches. The extent of acid hydrolysis followed the order: zero amylose>compound waxy>waxy>normal>compound normal>high amylose. High correlations were observed between physicochemical properties and structural characteristics of HB starches.