The effect of extractable lipid on the viscosity characteristics of corn and wheat starches

The defatting of both corn and wheat starch with 85% methanol yields starches which start to gelatinise at lower temperatures and have increased overall viscosities compared with untreated starches. The lipids extracted from wheat and corn starch with 85 % methanol were similar in total amount but showed very large differences in the proportions of neutral and phospholipids. The extracted corn lipids contained eight times as much neutral lipids (mainly free fatty acids) as phospholipids whereas the proportions of neutral and phospholipids in wheat starch were approximately equal. Addition of extracted lipids to defatted starches significantly modified the swelling and viscosity characteristics. Addition of wheat and corn lipids to potato starch (which contains almost no lipids) indicated that the higher percentage of phospholipids in wheat starch probably contributed towards the lower viscosity characteristics of wheat starch compared with corn starch.     

Characteristics of Volatile Compounds of Starches Extracted with Aqueous Solutions

Volatile compounds of wheat, corn, and potato starches were determined prior to and upon extraction of the starches with aqueous solutions of sodium hydroxide (NaOH), ethanol, and sodium dodecyl sulfate (SDS). Aqueous NaOH extraction was effective in reducing the level of total volatiles and removing certain volatiles from both wheat and corn starches without increasing the level of hexanal, an important lipid autoxidation product. However, the extraction did not considerably influence the composition and abundance of volatiles in potato starch. Aqueous ethanol extraction reduced the level of total volatiles only in wheat starch. Aqueous SDS extraction was not practical in the removal of volatiles from cereal starches. However, SDS extraction was effective in removing volatiles from potato starch, as well as reducing its hexanal level. It is evident that NaOH extraction is suitable for the removal of volatiles associated with cereal starches, whereas SDS extraction is more appropriate for tuber starches.     

几种淀粉的相对分子质量分布、微晶结构及形貌的研究

以小麦、马铃薯、甘薯、玉米、芋头为原料提取淀粉。采用碘兰值法、凝胶色谱、X衍射和扫描电镜,研究淀粉组成及淀粉级分的特性、淀粉的晶体特性和微观形态,为淀粉类食品的深加工提供理论基础。研究表明,芋头淀粉的碘兰值最小,其他4种淀粉碘兰值相差不大。玉米淀粉为高直链淀粉,小麦淀粉的3个级分较明显。马铃薯淀粉表现为B型X衍射图谱的特征,甘薯淀粉表现为C型X衍射图谱的特征,而小麦淀粉、玉米淀粉和芋头淀粉表现为A型X衍射图谱的特征,马铃薯淀粉的结晶度最小,玉米淀粉的结晶度最大、微晶尺寸最小,甘薯淀粉的微晶尺寸最大。     

SOME PHYSICOCHEMlCAL PROPERTIES OF STARCHES AS AFFECTED BY CHANGES IN ATMOSPHERIC PRESSURE

The effects of varying atmospheric pressures on the properties of starches were investigated. Four types of starches-corn, rice, potato and wheat-were studied for their water-binding capacity and viscosity behavior. Photomicrographs of starch suspensions were taken at five altitudes and temperatures of 22 °, 60 °, 70 °, 80 ° and 90 °C respectively. Measurements of the photomicrographs showed corn, potato and rice starch granules to increase in size on changing elevation from sea level to 10,000 feet. Wheat starch was not affected. Water-binding capacity increased for corn and potato starches as the altitude increased, but rice and wheat starches were not affected. The viscosity of corn, rice and wheat starch suspensions decreased initially with increasing altitudes but increased at the higher altitudes. The viscosity of potato starch suspensions did not change at increased elevations.     

Morphological,thermal, rheological and noodle‐making properties of potato and corn starch

A comparison between the morphological, thermal, rheological and noodle‐making properties of corn starch and potato starches separated from five different potato cultivars was made. The granule size and shape of all starches differed significantly. Potato starch granules were comparatively larger than corn starch granules, while the transition temperatures were found to be higher for corn starch. Consistency coefficients and flow behaviour indices measured by back extrusion were higher for potato starches than for corn starch. Stickiness of cooked starch pastes was observed to depend upon their consistency coefficient. The gels made from all potato starches showed higher gel strength than those from corn starch. The gel strength of starches from both corn and potato increased during refrigerated storage. The amylose content, swelling power, solubility and light transmittance values of potato starches were significantly higher than those of corn starch. Noodles made from potato starches had higher cooked weight and cooking loss than corn starch noodles. Texture profile analysis revealed that potato starch noodles also had higher hardness and cohesiveness than corn starch noodles. Hardness of cooked noodles from all starches increased and cohesiveness decreased during storage. Noodles made from starches of higher viscosity exhibited higher hardness and cohesiveness. Textural differences among cooked starch noodles appeared to be associated with morphological, thermal and rheological properties of corn starch and potato starches. © 2002 Society of Chemical Industry     

Rate of Hydroxypropylation of Starches as a Function of Reaction Time

To determine the course of the hydroxypropylation reaction as a function of reaction time, waxy corn, normal corn, potato, and wheat starches were reacted with propylene oxide under normal reaction conditions. Amounts of leached material and MS values of both leached and granular molecules were determined over the course of reaction. For waxy and normal corn starches, the extent of reaction increased linearly from 0 to 12 h, after which the reaction proceeded at an ever decreasing rate, reaching zero at about 30 h of reaction. The initial rate of reaction was determined by reacting waxy corn starch with a greater amount of propylene oxide (10×normal concentration) so that there would be no slowing of the reaction due to loss of reagent. Results confirmed that the initial reaction rate was linear. The hypothesis that, as derivatization proceeds, granules are opened up, resulting in ever increasing rates of reaction was not substantiated. Amounts and MS values of leached molecules from waxy and normal corn starches increased continuously over the course of the reaction. For potato and wheat starches, MS values of the granular starch also increased continuously over the entire reaction period. Amounts of leached molecules from potato starch were greater than those from wheat starch, with the amount leached at 30 h from potato starch being slightly more than that from normal and waxy corn starches and that from wheat starch being considerably less.     

甘肃主要杂豆淀粉理化特性分析

以甘肃产三角豌豆、白豌豆、小白芸豆、麻豌豆为材料,采用湿磨法提取淀粉,以玉米、马铃薯及绿豆淀粉为对照,对杂豆淀粉的理化特性进行分析。结果表明：参试杂豆淀粉颗粒多呈卵圆形,偏光十字较明显,多呈“X”形和斜十字形,部分淀粉颗粒呈现明显多脐点现象,平均粒径为21～29μm,其中三角豌豆淀粉的粒径最大而麻豌豆淀粉颗粒最小;淀粉颗粒的结晶类型与绿豆淀粉相同,为C型。其直链淀粉含量远高于玉米淀粉和马铃薯淀粉,且麻豌豆＞小白芸豆＞白豌豆＞三角豌豆淀粉。杂豆淀粉属限制型膨胀淀粉,起糊温度为72.6～78.8℃,且具有较好的热糊和冷糊稳定性,淀粉糊的透明度较高,但凝沉速度均极快,冻融稳定性也都较差。4种杂豆淀粉的理化特性与绿豆淀粉相近,可耐受高温处理,但不宜用于冷冻类食品的生产。     

Characteristics of pores in native and hydrolyzed starch granules

Low‐temperature nitrogen adsorption and mercury porosimetry were applied for analyzing effect of α‐amylolysis upon the porosity of granules of native corn, wheat, rice, and potato starches. Specific surface area (S_BET), porosity, pore size distribution, total pore area, and mean pore radius were determined for native and digested granules. It was found that native starch granules are macroporous materials with a small participation of mesopores. In the case of native starches, the highest value of S_BET was obtained for rice starch (1.27 m²/g) and the lowest – for potato starch (0.14 m²/g). Pore size distribution curves obtained by nitrogen adsorption showed peaks in the range of diameters 2–3 nm (for all starches) and 100–200 nm (for corn and rice starches). After 60 min of enzyme action, surface area of all starches doubled in comparison to native ones. Arising of the new pores was also noted. The results of mercury porosimetry measurements showed that rice starch had the highest total area of pores and porosity but the lowest mean pore radius among all native starches. The pore size distribution curves for all starches exhibited solely one peak corresponding to the dominant group of pores of the radii in the range 0.5–8 µm, dependent on the starch source. There were also much smaller peaks situated within the range of 3–30 µm. After α‐amylolysis of corn and rice starches, the average radius of the dominant group of pores diminished. No substantial changes in the pore radii could be noted for potato starch.     

Study on physicochemical characteristics of waxy potato starch in comparison with other waxy starches

The physicochemical properties of wx potato, wx corn, and wx rice starches were examined and compared. wx potato starch displayed the B‐type XRD pattern, whereas wx rice and wx corn displayed the A‐type. Shapes of wx potato starch were oval or slightly round, wx corn and wx rice starch granules were polygonal. AM contents of the three starches were between 1.0 and 1.5%. Rapid viscosity analyzer data showed initial pasting temperatures of wx potato, wx corn, and wx rice starches as 69.6, 75.4, and 76.8°C, respectively, peak viscosity, breakdown, and setback of wx potato starch were 2114, 1084, and 4 mPa s. Using DSC, onset temperature of gelatinization of wx potato starch was 5.5–7.2°C higher than those of wx rice and wx corn starches. The thermal enthalpies of the starches studied in our laboratory were in the range of 0.2268–1.9900 J/g with decreasing order of wx potato > wx corn > wx rice starch.     

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 different starches on rheological and microstructural properties of (I) model processed cheese

A range of processed cheese spread samples containing starch were prepared on a Rapid Visco Analyser (RVA). The starches used were waxy cornstarch, high‐amylose cornstarch, rice starch, potato starch, wheat starch and acid‐converted starch. Incorporation of the starches at different levels produced marked differences in the rheological, microstructural and functional properties of the processed cheese spreads. Rheological attributes such as complex modulus and viscosity increased; the extent of increase depended on the starch type and the starch level. Starch incorporation at reduced protein levels demonstrated the possibility of maintaining satisfactory rheological properties at lower ingredient cost.     

河南省主要种植小麦品种淀粉特性研究

采用小麦籽粒湿法分离淀粉技术，分离提取河南省种植的36种小麦和4种国外商品小麦的淀粉，计算出淀粉提取率．小麦淀粉提取率与品种有关；分析了这些淀粉样品的水分、脂类、蛋白质和直链淀粉含量，采用快速粘度分析仪(RVA)测定淀粉糊特性，测定了淀粉糊流变学特性，进行了回归分析和聚类分析，以淀粉的流变学特性为基础，进行了分类对比。发现安农98005与澳洲商品软麦具有相近的淀粉特性。     

Adsorption of Methyl Orange on Starches

Adsorption characteristics of methyl orange were investigated on kudzu, sweet potato, corn, rice, wheat, potato and snake gourd starches. No adsorption of methyl orange, an anionic dye, was observed on potato starch and snake gourd starch because of the presence of phosphate esters. Adsorption isotherms were found to fit both the Langmuir equation and Freundlich equation in all others. The degree of adsorption by kudzu, sweet potato, corn and wheat starches was related to the number of hydroxyl groups. We suggested methyl orange was confined to a monolayer on surface hydroxyl groups of the starches.     

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.     

凉粉草胶与不同淀粉混合体系糊化和质构性质的研究

凉粉草胶(MBG)与淀粉作用可以形成凝胶。为比较不同淀粉与MBG混合体系糊化和凝胶性质的差异,选取玉米等八种常见淀粉,利用Brabender糊化仪、质构仪、对MBG与不同淀粉混合体系的糊化和质构性质进行了研究。结果发现,MBG对谷类淀粉(大米、小麦、玉米)和豆类淀粉(绿豆、豌豆)的糊化性质的影响都比较显著,对薯类淀粉(木薯、马铃薯、甘薯)的不显著,但MBG与薯类淀粉混合体系的黏度远高于MBG与豆类和谷类淀粉的;MBG与大米淀粉形成的凝胶硬度最大,与马铃薯淀粉形成的凝胶硬度次之,与豌豆淀粉形成的凝胶硬度最小。淀粉与MBG之间相互作用的强弱可以从Brabender糊化曲线上的特征点值E-D来比较。     

Effect of Acetylation on Some Properties of Corn and Potato Starches

Corn starch and starches separated from different potato cultivars were acetylated to evaluate the effect of plant source on the physicochemical, morphological, thermal, rheological, textural and retrogradation properties of the starches. Corn starch showed a lower degree of acetylation than potato starches under similar experimental conditions. The degree of acetylation for different potato starches also differed significantly. Morphological examination revealed that the granules of acetylated Kufri Chandermukhi and Kufri Sindhuri starches tended to appear as fused and less smooth than native starch granules. Acetylation of corn and potato starches decreased the transition temperatures and enthalpy of gelatinization and increased swelling power and light transmittance. However, the change in these was greater in the potato starches with higher percentage of small sized granules. Acetylated starches showed higher peak G', G'' and lower tan δ than their counterpart native starches during heating. Among the starches from different cultivars, the change in the rheological parameters after acetylation differed to a significant extent. The retrogradation was observed to be negligible in the acetylated cooked starch pastes. Results implied that the change in functional properties of starches with acetylation depends on source and granule morphology of native starch.     

Ultrasound-treated starch: SEM and TEM imaging,and functional behaviour

Potato, wheat, corn and rice starch granules were suspended in water or ethanol and sonicated at frequency of 20 KHz and power 170 W for 30 min. The effect of ultrasonic treatment on starch structure was assessed on the basis of blue value (BV), A₆₈₀/A₅₄₅ ratio and λ_max determinations. The results showed that modification of starches in both solvents led to the reduction of all parameters connected with the starch–iodine complex. However, depolymerization of starch was higher when it was sonicated in water than in ethanol (e.g. BVs for potato starch: native and sonicated in water and ethanol were equal, respectively, 0.306, 0.275, and 0.279). Starch granules were also observed under scanning and transmission electron microscopes. The main effects of ultrasonic action were cracks and depressions on the surface of granules, which were especially well seen in the case of potato and wheat starches. Ultrasonic treatment, especially in water, influenced functional properties of starch causing an increase of fat and water absorption, least gelling concentration (except potato starch), solubility and swelling power, and a decrease of starch paste viscosity. Effect of ultrasounds on clarity of pastes was rather small, except potato starch for which its value increased from 70.3 to 82.5% after sonication in water.     

TEXTURAL PROPERTIES OF STARCH GELS FILLED WITH COLLAGEN AND CHITIN

Chitin and collagen powders were added as fillers to various starches (potato, sweet potato, kudzu, corn, wheat, and mung bean), heated at 100C for 10 min with stirring to make a hot paste and allowed to gel quiescently at 5C for 2 h in order to investigate the effects of the filler particle on the texture of the gels. The parameters of hardness, cohesiveness and adhesiveness were determined instrumentally and compared. The filler particles of collagen and chitin were effective in increasing hardness of corn starch gels but had no effects on hardness of the potato, sweet potato, kudzu, wheat and mung bean starch gels except at the lower starch concentrations. Cohesiveness was increased slightly in all starch gels by addition of collagen whereas chitin addition only increased the cohesiveness of sweet potato and mung bean starch gels. Collagen and chitin addition increased adhesiveness all of starch gels, but the intensity of the effect was most remarkable for collagen. The observed differences in effects was apparently due to differences in the interactions between starches and filler particles arising from differences in the surface properties of the filler particles.     

超声波辅助提取油莎豆淀粉工艺优化及其理化特性

为了得到超声波辅助提取油莎豆淀粉的最佳条件,以及油莎豆淀粉的理化特性,本文通过单因素和响应面试验研究提取油莎豆淀粉的最佳条件,通过扫描电镜分析、傅里叶红外变换分析、X射线衍射分析、DSC分析研究其理化特性。结果表明:最佳工艺条件为温度30 ℃、时间50 min、液料比15:1 mL/g、pH8,此条件下油莎豆淀粉提取率为92.22%±0.99%。将油莎豆淀粉与小麦淀粉等五种淀粉的理化特性对比发现:油莎豆淀粉颗粒较其它淀粉表面光滑,粒径范围与木薯淀粉、红薯淀粉、小麦淀粉相近,明显小于马铃薯淀粉,粒径范围2~15 μm,处于中小水平;油莎豆淀粉C-O和O-H拉伸程度较低,C-H的伸缩振动程度较低;油莎豆淀粉晶型与大多数谷物淀粉相似,属于A型淀粉;油莎豆淀粉在DSC实验中起始温度、峰值温度仅低于红薯淀粉,终止温度低于红薯淀粉和玉米淀粉。综上,油莎豆淀粉粒径相对较小,其属于A型淀粉,与B型淀粉相比不易发生水解,且其支链淀粉结构较多。     

Characterization of Phosphate Monoester Resistant Starch

The properties and structures of corn, wheat, and potato native starches and their phosphate monoester resistant starches were tested and compared. The results indicated that the resistant starch content, light transmittance, and freeze-thaw stability of the phosphate monoester resistant starch increased after modification. The native starches exhibited much higher peak viscosities compared with resistant starch (RS) and phosphate monoester resistant starches. The phosphate monoester resistant starch from corn and wheat starch exhibited a higher peak and final viscosity and lower gelatinization temperatures compared with the resistant starch, while the peak and final viscosity of the potato phosphate monoester resistant starch samples were lower than that of potato resistant starch. In the FT-IR graph, a new peak at 1244 cm^?1 (P=O bond) was observed for all kinds of phosphate monoester resistant starch.