Screw Configuration Effects on Macroscopic Characteristics of Extradates Produced by Twin-screw Extrusion of Rice Flour

The effects of 29 screw configurations on rice flour extrudates were investigated. The moisture content, screw speed and feed flow rate during all extrusion experiments were 15%, 400 rpm, and 12kg/h, respectively. Temperature profile in the 8 barrel sections from feed to die end were set at 0, 30, 30, 30, 70, 100, 150, and 150°C. Incorporation of kneading block (KB) and reverse screw element (RSE) in screw profiles significantly influenced apparent density, product expansion (radial, axial and overall), and breaking strength. Apparent density and overall expansion were functions of die temperature. KB was the best element for maximizing radial expansion. Product hardness (breaking strength) decreased with increasing radial expansion.     

Physical Properties of Extruded Products as Affected by Cheese Whey

Corn, rice and potato flour were extruded with sweet whey solids (SWS) or whey protein concentrate (WPC) using low and high shear extrusion processing conditions. WPC added at product content of 25% had minimal effect on the texture of extruded products. Expansion and breaking strength were improved in some processes through changes in extrusion shear and moisture. Whey product incorporation resulted in reduced specific mechanical energy input to the process. Increasing whey product concentration beyond 25% reduced expansion and water absorption indices significantly, affecting textural hardness. Product quality characteristics were directly related to the whey product content.     

Starch Conversion During Extrusion as Affected by Added Gelatin

Waxy maize starch was modified by twin-screw extrusion cooking in the presence and absence of gelatin. X-ray diffraction, microscopy, rheology, and differential scanning calorimetry studies showed that, at constant specific mechanical energy and extruder heater temperatures, the degree of starch conversion decreased with increasing levels of gelatin. It was hypothesized that during extrusion cooking, the gelatin acts as a lubricant, protecting the starch from being converted since more mechanical energy would be dissipated in the gelatin phase than the starch phase.     

Physical Properties of Cooked Wheat Grains as Affected by Cooking Temperature and Duration

The physical properties of soft and hard wheat grains, cooked with steam under pressure, were investigated. These included water uptake, rheological properties as observed by modulus of elasticity (E) and maximum compressive contact stress (S_max), color in CIE L*a*b* system and pasting properties by Rapid Visco Analyzer (RVA). Four cooking temperatures (110, 120, 130 and 1408 C) and six cooking durations (20, 40, 60, 80, 100 and 120 min) for each temperature were studied. Water uptake (WU) and rheological properties were analyzed immediately after cooking conditions were achieved. For color and pasting properties, cooked wheat grains were dried at low temperature and ground before analysis. It was found that WU increased proportionally with cooking temperatures and durations. Hard wheat grains tended to absorb more water than soft wheat grains. Both E and S_max decreased rapidly when wheat grains were cooked. Such decreases were found to be more rapid in hard wheat grains. Wheat grains became darker when cooked, resulting in the decrease of L* values and increase of a* and b* values. Cooked wheat grains lost their natural pasting properties compared to uncooked grains, resulting in the decrease of viscosity in their RVA profiles. The experimental data fitted well in second-order polynomial models (p # 0.0001). The built models were sufficiently accurate for most of the studied properties (R² ranging from 0.58–0.97).     

螺杆挤压机及其应用研究现状

综述了螺杆挤压机挤压加工的原理以及单螺杆、双螺杆、三螺杆挤压机和超临界二氧化碳挤压膨化机几种挤压加工设备,并简介了螺杆挤压机的应用。     

单螺杆挤压机中长螺杆的改进

对现有国内普遍使用的单螺杆挤压机中的长螺杆进行改进研究,提出一种带有交变螺距的螺杆组件结构,改进后的单螺杆挤压机省去了原来利用电能加热的装置,达到节约能源、方便生产,用此机组生产出的挤压膨化食品膨化效果优于未改进前,每小时的班产量是未改进前的3倍。     

Starch-stearic Acid Complex Development within Single and Twin Screw Extruders

Corn starch was extruded with 4% stearic acid in Brabender single screw and twin screw laboratory extruders. The screws were cooled and removed and samples were collected from locations along the screws. In the single screw extruder, starch gelatinization as determined by DSC and polarized light microscopy started in the compression zone and was completed in the metering zone. Starch-stearic acid complex formation as determined by iodine binding capacity and X-ray diffraction started at the same point as gelatinization and increased to a maximum near the tip of the screw. In the twin screw extruder, starch gelatinization and starch-stearic acid complex formation started at a distance of seven screw diameters and continued from there to the die end.     

不同来源的淀粉制备淀粉磷酸单酯的性能及应用

本文比较了马铃薯淀粉、蜡质玉米淀粉、木薯淀粉、小麦淀粉及经磷酸化后产品的物理性能，着重研究了其粘度及糖、盐对其粘度的影响并比较了磷酸化对糊的透明度、冻融稳定性及其对发泡体系的影响，结果表明不同淀粉制得的淀粉磷酸单酯的性能有很大差别。在蛋糕中的应用试验表明，在蛋糕中添加淀粉磷酸单酯可以增加比容并延长其货架寿命。     

三种天然植物淀粉辅料对米粉丝品质特性的影响

以天然绿豆淀粉、玉米淀粉及马铃薯淀粉3种天然植物淀粉为原料,探讨其作为辅料添加对米粉丝蒸煮品质和质构特性的影响。结果表明,添加适量的绿豆淀粉、玉米淀粉或马铃薯淀粉可显著提高米粉丝的烹煮品质及质构特性。绿豆淀粉添加量在0.5~1.5%时加工的米粉丝具有较高的烹煮品质,其添加量在1%时可以显著提高米粉丝的质构特性;玉米淀粉的添加量为6%时米粉丝的烹煮品质较佳,其添加量在4~6%时可显著提高米粉丝的质构特性;马铃薯淀粉的添加量为2%时,米粉丝具有最高的烹煮品质,其添加量在2~3%时可使米粉丝的质构特性显著提高。综合考虑,当绿豆淀粉、玉米淀粉或马铃薯淀粉的添加量分别达到1%、6%和2%时能够显著改善米粉丝的蒸煮和质构品质特性。     

不同原淀粉及其羟丙基淀粉性质的研究

本实验对糯米淀粉、糯玉米淀粉、马铃薯淀粉、普通玉米淀粉及其羟丙基淀粉的基本性质进行了研究比较.结果表明,四种淀粉及其羟丙基淀粉的黏度、透明度、冷藏稳定性、冻融稳定性、碘显色反应以及白度都有明显差异.研究还发现,羟丙基化不仅可以降低各种淀粉的糊化起始温度及碘显色反应,还可改善淀粉的透明度、冷藏稳定性及冻融稳定性.     

韧化温度和时间对不同直链淀粉质量分数玉米淀粉物化性质的影响

为进一步探讨韧化处理对淀粉性质的作用机理,通过测定糊化性质、热特性、膨胀力、结晶特性及观察偏光十字现象和微观结构,研究了不同韧化温度和时间对不同直链淀粉质量分数玉米淀粉（普通玉米淀粉（normal corn starch,NCS）和蜡质玉米淀粉（waxy corn starch,WCS））物化性质的影响。结果表明,韧化处理主要作用于NCS和WCS淀粉颗粒的无定形区,对淀粉结晶类型没有影响;但韧化处理能够明显增强NCS和WCS的热稳定性和抗剪切能力,抑制淀粉老化和糊化,显著降低峰值黏度和膨胀力（P＜0.05）。韧化温度升高至60 ℃时韧化效果更加明显,糊化焓和相对结晶度明显降低,颗粒表面被明显破坏。但延长韧化时间对NCS和WCS老化的抑制效果和对糊化焓、膨胀力、颗粒形貌等的影响不明显。     

不同淀粉原料的疏水改性及其性质研究

本文研究了不同添加量的辛烯基琥珀酸酐(OSA)、Al3+以及不同p H值在改性过程中对玉米淀粉、木薯淀粉和马铃薯淀粉休止角、活化指数、接触角、分散性、和偏光特性的影响。实验表明,随着OSA、Al3+添加量和交联过程中p H值的增加,玉米淀粉和木薯淀粉的休止角呈现出先减少后增加的特征,而只有p H值的变化对马铃薯淀粉的休止角产生了比较明显的影响;改性后,三中淀粉的接触角均大于90°,证明淀粉疏水性得到显著提高;同时,在活化指数试验中,木薯淀粉和马铃薯淀粉的活化指数可以达到0.95;液体石蜡中的分散性测试表明,玉米淀粉的分散性最好,其次是木薯淀粉,马铃薯淀粉的分散性最差,而改性后淀粉的分散性较原淀粉并未出现明显变化;最后,通过观察同等光强条件下淀粉的偏光特性,发现改性后淀粉颗粒出现偏光十字变弱、表面阴影增加的情况。     

Functional and Structural Properties of Corn,Potato, and Cassava Starches as Affected by a Single-Screw Extruder

The aim of this study was to identify suitable starch sources that can improve the structural integrity of plant protein-based extruded feeds, specifically aquatic feeds. Extrusion trials were performed, using a single-screw extruder. Extruder temperature, screw speed, and moisture content were varied in a factorial design with a replicated central composite point. The effects of these variables on functional and structural properties of the extrudates were evaluated. Temperature had the dominant effect on all properties. Increasing extruder temperature resulted in notable increases in onset temperature of gelatinization and glass transition temperature of all extrudates. The lowest water absorption, alkaline viscosity, and the highest water solubility, in addition to the lowest Rapid Visco Analyzer profile were found for corn starch extrudates. The lowest thermal stability was observed for the potato extrudate. It is expected that cassava and potato starches can contribute better in the formation of a cohesive structure and the generation of more expanded extrudates, specifically in the production of aquafeed. The higher enthalpy transition of corn extrudates indicated the higher thermal stability of corn starch which can lead in production of more durable aquafeed extrudates.     

山西不同品种谷子淀粉的理化特性研究

从谷子主产区山西省选取8个具有代表性的谷子栽培品种作为供试材料,分析研究了其淀粉的颗粒形态及粒径大小、直链淀粉含量、碘蓝值与淀粉糊的透光率、冻融稳定性、糊化特性、溶解度与膨胀度及凝沉特性等理化性状。结果表明：小米淀粉颗粒均为单粒,外形规整,多数为多角形,少数为卵圆形,具有清晰可见的偏光十字,不同品种间淀粉颗粒形态差异明显。小米淀粉小颗粒的粒径为0.42~2.25 μm,大颗粒的粒径为3.42~29.26 μm,小米淀粉的粒径分布特征呈现出“三峰”型。8个品种的直链淀粉含量变幅为2.22~17.96%,碘蓝值变幅为0.586~0.872,透光率变幅为2.4~29.2%,析水率变幅为3.67~49.85%,糊化温度变幅为67.6~78.8 ℃,各品种间具有显著差异。此外,各品种淀粉的糊化特性、溶解度、膨胀势及淀粉糊的凝沉特性也有着明显的差异。因此,应根据不同的加工目的采用相适宜的品种。     

双螺杆挤压机操作参数变化对谷物产品特性的影响

对食品双螺杆挤压机的操作参数与挤出过程及谷物产品特性之间的关系作了试验研究。通过改变螺杆转速、进料速率这两个变化因素,研究模头压力、模头处物料温度、主机电流、产品膨化度、产品水溶性指数、产品吸水性指数等指标的变化规律,建立有关数学模型并进行分析。     

Preparation and Physical Properties of Zein-Coated High-Amylose Corn Starch Film

The objective of this study was to prepare the edible composite films using high-amylose corn starch (HACS) and corn zein and to determine their physical properties. HACS was gelatinized using the specially designed high-pressure container. HACS film containing 20 g sorbitol/100 g as a plasticizer had suitable physical properties. The HACS film coated with corn zein containing 20 g oleic acid/100 g had moderate physical properties and barrier properties.     

不同直链/ 支链比的玉米淀粉分子质量及其构象

采用凝胶渗透色谱(GPC)和十八角度激光光散射(MALLS)技术,以二甲基亚砜为流动相测定蜡质玉米淀粉、普通玉米淀粉、直链/ 支链比1:1 的高直链玉米淀粉(G50)、直链/ 支链比4:1 的高直链玉米淀粉(G80)的分子质量及其分布以及在二甲基亚砜(DMSO)溶液中的均方根旋转半径和构象。结果表明：分子质量最大的是蜡质玉米淀粉,其重均分子质量达到了1.416 × 108g/mol,其次是普通玉米淀粉2.744 × 107g/mol 与G50 1.026 × 107g/mol,最小的是G80 的3.992 × 106g/mol;均方根旋转半径也是随着直链淀粉含量的增加依次减小;蜡质玉米淀粉在DMSO 溶液中的构象是较为紧密的无规则卷曲型,其他3 种玉米淀粉的构象均为球型。     

High-Protein Texturized Products of Defatted Soy Flour, Corn Starch and Beef: Shelf-Life, Physical and Sensory Properties

Selected mixes consisting of Bf [high-beef (29%) low-fat (2.96%)], bf [low-beef (20%) low-fat] and BF [high-beef high-fat (5%)] which incorporated raw beef, defatted soy flour, and corn starch were extruded in a single-screw extruder. The products had no flavor additives and trained sensory panelists detected hay-like, beany or grainy flavors. Bf extrudate was more expanded than BF extrudate and rated least hard by the sensory panel, whereas bf extrudate was least susceptible to lipid oxidation. Bf and bf extrudates showed microstruc-tures with large air cells. All three showed advantages of beef and soy flour in amino acid and fatty acid compositions, respectively, and were microbiologically safe during prolonged storage at 37°C.     

Structural and Physical Properties of Starches Isolated from Six Varieties of Millet Grown in China

This study investigated the structural and physical properties of starches extracted from six varieties of millet mainly grown in China. The amylose content of millet starches ranged from 17.6 to 28.4 g/100 g (dry weight basis, db), and a variety of waxy proso millet starch (0.38 g/100 g, db) was identified. These starches exhibited a majority of large polygonal granules with several indentations, few small spherical granules, and A-type crystallinity. Proso millet starch showed prominent paste clarity and freeze-thaw stability, whereas finger millet starch exhibited the highest solubility. Moreover, barnyard millet starch had the lowest sediment volume. The gelatinization enthalpy of proso millet starch was the highest (5.16 J/g). For non-waxy millet starch, the ratio of retrogradation (R%) was positively correlated with amylose content. Among all starches, the storage modulus (G′) was higher than the loss modulus (G″) during heating and cooling. The G′ and G″ of proso millet starch and barnyard millet starch pastes were significantly lower than other starches during cooling. The pasting properties of six millet starches significantly differed, had positive correlation with amylose content, and were affected by NaCl, sucrose, and pH values.