A comparison of native and acid thinned normal and waxy corn starches: Physicochemical, thermal, morphological and pasting properties

The starches isolated from normal and waxy corn varieties were hydrolyzed with hydrochloric acid (0.14 mol equivalent/L) and evaluated for physicochemical and functional properties. Acid thinning decreased the amylose content and swelling power but increased the solubility. The light transmittance of acid thinned (AT) starch pastes was higher than those of their native starches after similar storage intervals. The scanning electron microscopic observation demonstrated that the acid thinning did not cause any disruption of the granular crystalline structure. Native normal corn starches showed lower onset temperature (T_o) and peak temperature (T_p) as compared to their counterpart AT starches, whereas the reverse was observed for waxy corn starch. Enthalpy of gelatinization (ΔH_gel) was lower in AT normal and waxy starches as compared to their native starches. The percentage of retrogradation (%R) was significantly higher for native corn starches as compared to their AT starches. A significant reduction in peak—(P_V), trough—(T_V), breakdown—(B_V), final—(F_V), and setback viscosity (S_V) was observed by acid thinning, and the reduction was more pronounced in AT waxy starches. Among AT starches, AT waxy starch showed the lowest values of P_V, T_V, B_V, F_V and S_V.     

Effect of Amylose Content on Gelatinization,Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice

Presently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (T_o), peak (T_p) and conclusion (T_c) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.     

Characterization of Different Starches Oxidized by Hypochlorite

The effects of starch origin (potato, corn, and rice starches) and hypochlorite level (NaOCl, 0.8% and 2% w/w) on the structures and physicochemical properties of oxidized starches were investigated. Carboxyl and carbonyl group contents of oxidized starches increased with increasing NaOCl level, with potato starch having the highest and corn starch having the lowest carboxyl groups content at both NaOCl levels. Oxidation generally reduced the pasting temperature and viscosity of native starches as demonstrated by using a Rapid Visco Analyser. The peak viscosities of oxidized rice and corn starches were higher than those of their native counterparts at 0.8% NaOCl. The morphology of starches was not altered and X‐ray diffraction patterns of all the starches remained unchanged after oxidation. Oxidized starch batters exhibited greater adhesions than did native starch batters, with rice starch batter exhibiting the greatest adhesion. Carbohydrate profiles by high‐performance size‐exclusion chromatography indicated that both amylopectin and amylose were degraded during oxidation. The level of oxidation was largely dependent on the degree of crystallinity of starch and the degree of polymerization of amylose, whereas the adhesion property of oxidized starch was mainly attributed to its granular size and shape.     

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.     

A study of the retrogradation process in five argentine rice starches

Rate of the retrogradation process of five new argentine genotypes rice starches with different amylose contents and gelatinization temperatures during storage at 4.5 ± 0.5 °C was studied using differential scanning calorimetry (DSC).Significant differences were not found among transition temperatures, i.e., T₀ (onset temperature), T_p (peak temperature) and T_c (conclusion temperature), of non-waxy genotypes when studied using DSC. An increased retrogradation enthalpy (ΔH, mJ/mg) with the storage time occurred with all non-waxy samples. The waxy genotype, W4109, did not show a retrogradation peak for the period under study. Genotypes with high total amylose content (TAM) retrograded more than those with lower content. The kinetic parameters “k” and “n” were evaluated using the Avrami model appearing to be related to the water-soluble amylose (SAM) content. Relationship between the retrogradation degree (%R) and the water-insoluble amylose (IAM) content was found. Gelatinization temperature of the starch (T_G) seemed to affect the retrogradation rate.     

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.     

Gelatinization Characteristics of Starch from du,wx, ae,and ae wx Endosperm of Sweet Corn Inbred la5125

Starch gelatinization in excess water was studied by differential scanning calorimetry for the mutants dull (du), waxy (wx), and amylose extender (ae), and the double mutant amylose-extender, waxy (ae wx) from the Ia5125 sweet corn inbred background. Onset temperature (T_o), peak temperature (T_max), and enthalpy (ΔH) were determined. For du and wx starches T_max was within 1°C of the value for the normal starch (T_max = 69.4°C). For starches from ae and ae wx mutants, T_max was 7–8°C higher than the normal starch. The highest enthalpies were observed for wx (3.26 cal/g) and ae wx (3.39 cal/g) starches; ae (2.93 cal/g) and normal (2.52 cal/g) starches were intermediate, and du (2.32 cal/g) starch had the lowest enthalpy. The endotherm of the ae starch was completed at just above 100°C, in distinction to reports for ae mutants from dent lines. Although the ae wx endotherm occurred at a higher temperature than the wx, the endotherm was sharpened relative to the ae endotherm, and was complete at 90°C.     

Physicochemical properties of waxy and normal corn starches treated in different anhydrous alcohols with hydrochloric acid

Corn starches (25 g, d. b.) were treated in anhydrous methanol, ethanol, 2-propanol or 1-butanol (100 ml) with 1 ml 36% hydrochloric acid at 45 °C for 1 h, the molecular weight and chain length distributions of starch were examined by high-performance size-exclusion chromatography (HPSEC), and the granule size, granular structure, λ_max, blue value, solubility and gelatinization thermal properties of starch were also examined. Results showed the recovery yields of the treated starch were higher than 96%, and the granule sizes of treated starches were slightly lower than their counterpart native starch. Starches after acid-alcohol treated showed internal fissures or cavities in some granules, and the number of granule with fissures or cavities increased with the increasing carbon number of alcohol. The weight average degree of polymerization and relative content of F1 fraction of starch after treated profoundly decreased, and the amylose and long chain of amylopectin of starch were preferentially degraded. The degradation extent of molecules after acid-alcohol treatment was found directly related to the alternation of internal structure of starch granule. The λ_max and blue value of both waxy and normal corn starches after treated also obviously decreased with the increasing carbon number of alcohol, while the solubility of starch profoundly increased after treated. The gelatinization onset temperature (T_o) of acid-alcohol treated waxy corn starch decreased with the increasing carbon number of alcohol, but the treated normal corn starches showed similar T_o values. Despite the alcohol used, the solubility of treated waxy corn starch linearly correlated (r²=0.983) with T/T_o value (T was the measuring temperature used for solubility determination). Whereas, normal corn starch treated in different alcohols showed distinct relations between T/T_o and solubility.     

Microstructural and physicochemical properties of heat-moisture treated waxy and normal starches

Starches from normal rice (21.72% amylose), waxy rice (1.64% amylose), normal corn (25.19% amylose), waxy corn (2.06% amylose), normal potato (28.97% amylose) and waxy potato (3.92% amylose) were heat-treated at 100 °C for 16 h at a moisture content of 25%. The effect of heat-moisture treatment (HMT) on morphology, structure, and physicochemical properties of those starches was investigated. The HMT did not change the size, shape, and surface characteristics of corn and potato starch granules, while surface change/partial gelatinization was found on the granules of rice starches. The X-ray diffraction pattern of normal and waxy potato starches was shifted from B- to C-type by HMT. The crystallinity of the starch samples, except waxy potato starch decreased on HMT. The viscosity profiles changed significantly with HMT. The treated starches, except the waxy potato starch, had higher pasting temperature and lower viscosity. The differences in viscosity values before and after HMT were more pronounced in normal starches than in waxy starches, whereas changes in the pasting temperature showed the reverse (waxy > normal). Shifts of the gelatinization temperature to higher values and gelatinization enthalpy to lower values as well as biphasic endotherms were found in treated starches. HMT increased enzyme digestibility of treated starches (except waxy corn starch); i.e., rapidly and slowly digestible starches increased, but resistant starch decreased. Although there was no absolute consistency on the data obtained from the three pairs of waxy and normal starches, in most cases the effects of HMT on normal starches were more pronounced than the corresponding waxy starches.     

Effect of amylose content on estimated kinetic parameters for a starch viscosity model

The apparent viscosity profile of starches during gelatinization varies with different amylose content. This study focused on the influence of amylose content on the kinetic parameters of a starch viscosity model for corn starches. The five parameters were: gelatinization rate constant (k_g), gelatinization activation energy (E_g), relative increase in apparent viscosity during gelatinization (A^α), relative decrease in apparent viscosity during shearing (B), and viscous activation energy (E_v). The parameters were estimated at different amylose content using both ordinary least squares nonlinear regression and the sequential method. The mixer viscometry approach was used to measure apparent viscosity. The first part of this paper presents parameter estimation results for waxy corn starch. The model was validated by using the parameters to predict viscosity for the same starch in a different measuring system, i.e., the RVA. The second part of this paper presents the estimated parameters for corn starch blends at different amylose content. The following parameters were significantly affected by amylose content: k_g and E_g both decreased with amylose content by an power-law relationship. Activation energy of gelatinization ranged from 121 to 1169 kJ/mol. The other parameters A^α, B, and E_v were not significantly influenced by amylose content. In summary, the gelatinization parameters k_g and E_g dramatically decreased as amylose increased from 3% to 35% (waxy corn starch blends).     

Functional,thermal and molecular behaviours of ozone-oxidised cocoyam and yam starches

Ozone-oxidised starches were prepared from the native starches isolated from white and red cocoyam, and white and yellow yam cultivars. The native and oxidised starches were evaluated for functional, thermal and molecular properties. The correlations between the amount of reacted ozone and carbonyl and carboxyl contents of the starches were positive, as ozone generation time (OGT) increased. Significant differences were obtained in terms of swelling power, solubility, pasting properties and textural properties of the native starches upon oxidation. The DSC data showed lower transition temperatures and enthalpies for retrograded gels compared to the gelatinized gels of the same starch types. The native starches showed C_B-type XRD patterns while the oxidised starches resembled the C_A-type pattern. As amylose content increased, amylopectin contents of the starches decreased upon oxidation. Similarly, an increase in M_w values were observed with a corresponding decrease in M_n values upon oxidation.     

Starch–cassia gum interactions: A microstructure – Rheology study

We present for the first time the interactions of starch and cassia gum – a novel galactomannan recently approved for use in food processing. Viscoelastic, pasting and microstructural characterization of various starches (waxy; high amylose; normal; cross-linked waxy corn starch; potato starch) containing different levels of the cassia gum was carried out. Significant changes were observed in the morphology of granule remnants formed during gelatinization in the starch pastes prepared with and without the addition of cassia gum. The freeze-dried starch–cassia gum pastes presented a shrunken and tight arrangement of the starch granule remnants, when studied by scanning electron microscopy. A significant reduction in the granule remnant size was also calculated using laser diffraction particle size analysis. The extent of interaction with cassia gum differed significantly among the various starch types. All the unmodified corn starches recorded an increase in peak viscosity at all levels of the cassia gum addition. An increase in the final viscosity of these starches was also observed by the addition of cassia gum, with high amylose and normal corn starch showing the maximum. Similarly, the extent of breakdown and setback viscosity also differed among the different starch types. Ranges of dynamic rheological measurements (temperature, time and frequency sweeps) were performed within the viscoelastic zones. Rheological parameters, such as storage modulus (G′), loss modulus (G″) and the gelatinization temperature (T_gel), of the corn starches during the heating cycle were observed to increase, when cassia gum was present at lower levels. The starch–gum systems also exhibited higher tan δ values during both the heating and the cooling cycles, indicating the dominance of the viscous modulus. The G′ and G″ of all the corn starch gels containing cassia gum showed higher values throughout the frequency sweep range. However, the increase in G′ and G″ of different starches was not always consistent with the increase in cassia gum levels. The changes in rheological behaviour during storage of the starch gels, aged on the plate of the rheometer and then studied through time sweeps at 5 °C and frequency sweeps at 25 °C, suggested that the starch gels containing cassia gum had less pronounced changes in the rheological parameters than had their control counterparts.     

Formation of starch spherulites: Role of amylose content and thermal events

Commercial maize starches and potato starches of two cultivars differing in physicochemical composition (granule size distribution; amylose to amylopectin ratio) and crystallinity were heated to 180 °C and then cooled by fast quench using a differential scanning calorimeter (DSC), in order to produce spherulitic starch morphologies. Among the raw maize starches, waxy maize starch had highest relative crystallinity (49%) whereas a lowest crystallinity of 33–39% was calculated for high-amylose maize starches. Potato starches showed a relative crystallinity of 50%. The temperatures and enthalpies of gelatinisation and melting varied among all the starches. High-amylose maize starches showed higher transition temperatures of gelatinisation (T_gel), whereas waxy maize starch had lowest T_gel and enthalpy of gelatinisation (ΔH_gel). Similarly, a considerable variation in parameters related with crystalline melting (T_m1, T_m2 and ΔH_m1, ΔH_m2) was observed for different starches. The superheated gels of different starches treated using DSC were subjected to polarised microscopy, to confirm the formation of spherulites. Both the high-amylose starch gels showed the presence of spherulites exhibiting birefringence and a weak crystalline pattern. No birefringence was observed for waxy maize starch gel, while potato starch gels had some birefringence. The particle size distribution of high-amylose maize starch gels analysed through Zetasizer showed the sizes of spherulitic particles fall in the range of 300 nm–900 nm. The scanning electron micrographs of the dried high-amylose maize starch gels showed the presence of round spherulites consisting of several aggregated spherulitic particles. Amylose content and melting of crystallites during heating play an important role during recrystallisation of amylose (spherulite morphologies).     

氧化糯玉米淀粉的制备及性能研究

以糯玉米淀粉为原料,以次氯酸钠为氧化剂,氢氧化钠为催化剂,对氧化糯玉米淀粉的制备及性能进行了研究.考察了反应时间、反应温度、次氯酸钠用量、pH对氧化糯玉米淀粉羧基含量的影响,采用酸碱滴定法测定氧化糯玉米淀粉羧基含量.试验结果表明,随着次氯酸钠用量增加,氧化糯玉米淀粉的羧基含量也随之增大;在一定时间范围内,氧化糯玉米淀粉的羧基含量随反应时间的增加而增加;反应温度和pH对氧化糯玉米羧基含量的影响呈倒抛物线趋势,存在最大值.糯玉米淀粉经氧化后,其液透明度和黏度热稳定性提高,但其冻融稳定性和凝沉性下降.     

Development and Physicochemical Characterization of New Resistant Citrate Starch from Different Corn Starches

Resistant starch has drawn broad interest for both potential health benefits and functional properties. In this study, a technology was developed to increase resistant starch content of corn starch using esterification with citric acid at elevated temperature. Waxy corn, normal corn and high‐amylose corn starches were used as model starches. Citric acid (40% of starch dry weight) was reacted with corn starch at different temperatures (120–150°C) for different reaction times (3–9 h). The effect of reaction conditions on resistant starch content in the citrate corn starch was investigated. When conducting the reaction at 140°C for 7 h, the highest resistant starch content was found in waxy corn citrate starch (87.5%) with the highest degree of substitution (DS, 0.16) of all starches. High‐amylose corn starch had 86.4% resistant starch content and 0.14 DS, and normal corn starch had 78.8% resistant starch and 0.12 DS. The physicochemical properties of these citrate starches were characterized using various analytical techniques. In the presence of excess water upon heating, citrate starch made from waxy corn starch had no peak in the DSC thermogram, and small peaks were found for normal corn starch (0.4 J/g) and Hylon VII starch (3.0 J/g) in the thermograms. This indicates that citrate substitution changes granule properties. There are no retrogradation peaks in the thermograms when starch was reheated after 2 weeks storage at 5°C. All the citrate starches showed no peaks in RVA pasting curves, indicating citrate substitution changes the pasting properties of corn starch as well. Moreover, citrate starch from waxy corn is more thermally stable than the other citrate starches.     

Retrogradation properties of rice starch gelatinized by heat and high hydrostatic pressure (HHP)

Retrogradation process of pressure-gelatinized rice starches was investigated and compared with the heat-gelatinized ones in this study. Our results showed that the retrogradation rate of normal rice starch gelatinized by high hydrostatic pressure (HHP) was slower than that by heat. Nevertheless, there was no difference in retrogradation rate for waxy rice starch gelatinized by the two treatments (P > 0.05). The DSC data were further analyzed using the Avrami equation. The result indicated that the pressure-gelatinized normal rice starch had a lower recrystallization rate (k) and a higher Avrami exponent (n) than the heat-gelatinized one, but the two treatments did not affect the k and n for waxy rice starch. Furthermore, the intact starch granules and lower amylose leaching were observed only in the pressure-gelatinized normal rice starch. These findings suggest that the retardation mechanism of HHP on starch retrogradation is probably attributed to less broken granules and lower leached amylose.     

Comparison between Size Exclusion Chromatography and Micro‐Batch Analyses of Corn Starches in DMSO using Light Scattering Detector

The molecular structure of corn starches different in amylose content (waxy, normal, and high‐amylose) was analyzed in 90% dimethyl sulfoxide (DMSO) solution by refractive index (RI) and multi‐angle laser light scattering (MALLS) detectors. The starch sample solutions were measured either by medium‐pressure size exclusion chromatography (MPSEC) or by the micro‐batch mode. For waxy corn starch, the average molar mass (M_w) and radius of gyration (R_g) values were similar in both methods. However, for normal and high‐amylose corn starches, M_w measured by the micro‐batch mode was 2–4 times greater than that by the chromatographic method, although R_g values obtained from both methods were not very different. The M_w difference was the greater the higher the amylose content of starch.     

Digestibility and Pasting Properties of Rice Starch Heat‐Moisture Treated at the Melting Temperature (Tm )

Non‐waxy and waxy rice starches adjusted to 20% moisture (wet based, w.b.) were heated in a differential scanning calorimeter to determine the optimum parameters for producing slowly digestible starch (SDS). Starches heated to the temperature of melting (T_m) and held for 60 min in the calorimeter showed a slow digestibility compared to unheated samples. Digestibility decreased by 25 and 10%, respectively, for non‐waxy and waxy rice starches relative to non‐treated starches. Heat‐moisture treatment of waxy corn, non‐waxy corn and wheat starches at the T_m determined for non‐waxy rice starch did not result in significant decreases in digestibility. For waxy rice starches heat‐treated in microwave or conventional ovens at the T_m , there were slight but significant increases in digestibility of the treated starches compared to non‐treated starches at all incubation times. Digestibility was higher for starches heated for 30 min than for 60 min. Non‐waxy rice starches did not show any significant changes in digestibility. Heat‐moisture treatment at the T_m and the holding time of sample at that temperature in a differential scanning calorimeter were found to be significant to the formation of slowly digestible heat‐moisture treated starch.     

Comparison of Thermal and Viscoelastic Properties of Four Waxy Starches and the Effect of Added Surfactant

The waxy starches used in this investigation (maize (WM), barley (WB) and two rice starches RD4 and IR29) showed different gelatinization temperatures (GT) and enthalpies (ΔH_G) measured with differential scanning calorimetry (DSC). The differences in GT and ΔH_G could only partially be related to X-ray crystallinity. The high GT waxy starches WM and RD4 retrograded to a greater extent measured with DSC and the order of increased retrogradation agreed well with the order of X-ray crystallinity of the retrograded waxy starches. The melting temperature (T_C) of the retrograded waxy starches in contrast to GT was very similar for all starches. This indicates that the temperature of the glass transition (T_g) of the amorphous regions in the starch granules controlled the onset GT and perhaps also the extent of retrogradation. Addition of cetyl trimethyl ammonium bromide (CTAB) decreased the extent of retrogradation more than 45% compared to the melting enthalpy (ΔH_C) of the waxy starches without CTAB addition. The rice starch RD4 was most affected by the CTAB addition, and the WM starch the least. The viscoelastic behaviour in the temperature interval 25–90°C of 12%(w/w) gels differed between the waxy starches. The WB starch gels showed the highest storage modulus (G′) value and the lowest phase angle (δ), i. e. strongest and least viscous gels. The WM starch gels showed the lowest G′ value and the highest δ. The rice starches were in between with the RC4 starch (high GT) showing higher G′ value and lower δ than the IR29 (low GT). The viscoelastic parameters changed only slightly with increased temperature. The addition of CTAB to the waxy starch gels changed the viscoelastic behaviour of the stronger and less viscous starch gels of the WB and RD4 as their G′ value decreased and δ increased with increased temperature. The effect on WM and IR29 was only small.     

双氧水氧化糯玉米淀粉工艺研究

以糯玉米淀粉为原料,双氧水为氧化剂,硫酸铜为催化剂,对氧化糯玉米淀粉的制备工艺进行了研究。考察了反应温度、反应时间、pH、双氧水用量、硫酸铜用量对氧化糯玉米淀粉羧基含量的影响。以红外光谱表征氧化糯玉米淀粉。结果表明,反应温度、反应时间、pH、双氧水用量、硫酸铜用量对糯玉米淀粉氧化均有影响。当硫酸铜用量小于0.082%时,氧化糯玉米淀粉羧基含量随着硫酸铜用量的增加而增加。糯玉米淀粉经双氧水氧化后,其糊液透明度增加,凝沉性减弱。