不同挤压参数对大豆粕蛋白质结构的影响

该文系统研究了油脂提取前挤压膨化预处理工艺对大豆粕蛋白质表面疏水性、游离巯基含量的影响，分析了物料水分、膨化温度、δ段长度、模孔长度、螺杆转速等不同挤压参数与蛋白质结构变化的关系，建立了挤压参数与粕蛋白质游离巯基含量关系的量化模型。结果表明：低物料水分、低膨化温度、短模孔可以减少挤压膨化预处理工艺过程中蛋白质结构的破坏程度。相反，高物料水分、高温挤压膨化时，会加剧蛋白质分子内部疏水基的暴露和蛋白质的交联。在此基础上改进的挤压膨化预处理工艺更有利于蛋白质结构的改善。     

香蕉茎秆挤压脱水技术装备研究进展及改进方向

香蕉茎秆挤压脱水工艺是香蕉茎秆资源化利用的关键步骤,可以有效地降低运输成本,减轻蕉农的劳动强度,有利于提高香蕉茎秆的综合利用率。该文从介绍香蕉茎秆原料结构形态,化学成分以及蕉秆水分的存在形态出发,详细论述了国内外对高含水量的香蕉茎秆采取的脱水技术的研究现状和最新进展,指出了各种典型设备的结构特点。讨论了各种机械挤压脱水设备的实用性、优缺点及商业推广价值。指出平板压榨为间歇生产,压榨周期长;螺旋挤压脱水要求原料为粉碎性物料,物料的适应性差;轧辊式挤压脱水为连续生产,效率较高。针对香蕉茎秆体形高大质地软,纤维长的特点,确定香蕉茎秆挤压脱水技术应采取轧辊式挤压脱水工艺,提出轧辊式挤压脱水设备的开发改进建议,认为设备体积小,操作简单安全,处理量大,可靠性高是主要的研究方向。     

双低油菜籽脱皮冷榨的关键技术研究

针对双低油菜籽脱皮籽仁在冷榨过程中存在的一些关键技术问题，提出了双阶多级压榨的冷榨结构模型，对现有的螺旋榨油机的榨膛结构进行了改进，设计并制造了一种小型实验型冷榨机。在该机上，对操作工艺参数对脱皮籽仁的冷榨性能的影响进行了实验研究，结果表明，榨油机设定在较低转速(11 r/min) 有利于油料的冷榨，对入榨油料进行适度的调质(水分在6.4%)处理能改善油脂的提取效率，5%以下的仁中含皮率的要求是适宜的。冷榨脱皮菜籽仁的最大料筒温度始终低于70℃，确保了冷榨的需要。所研究的成果将为大型商用冷榨机的开发铺平道路。     

微波技术在食品和农产品加工中应用研究进展

微波加热技术具有速度快、可控性高等特点,在食品和农产品的热加工过程中具有较强应用潜力。该研究在分析微波加热原理的基础上,从技术应用、设备研制和仿真研究等方面介绍微波加热应用现状,如在农产品干燥、杀菌、萃取和膨化等方面进行深入研究和应用。指出微波加热在机理解析、工艺局限性、加热不均匀性和能量利用低等问题,尤其是微波场对物料内极性成分作用机制的研究深度、微波加热时在物料内温度和水分分布的不均匀性规律定量表征等方面,严重影响产品质量稳定性和能量充分利用。从揭示微波在加热腔体内传递和物料内吸收的机理,提高微波加热均匀性和改善加工质量,以及研制智能化工业用微波加工设备等方面,指出微波加热技术在食品和农产品加工中应用热点研究方向。针对微波加热技术在农产品和食品加工中科学问题、技术需求和设备现状,为发挥技术优势、拓展应用领域,该文提出微波加热理论研究与技术应用的发展趋势,以期提高微波热加工技术工业化应用适用性、保证产品质量和能量利用率。     

植物蛋白高水分挤压组织化技术研究进展

植物蛋白高水分挤压组织化技术是近年来发展的一项食品质构重组技术,在食品和饲料加工中有广泛用途。该文通过分析相关文献资料,介绍了植物蛋白高水分挤压组织化技术的定义和技术难点;论述了挤压参数之间的关系、操作参数的优化和产品特性的评价方法;讨论了产品组织化结构的形成机理等问题。分析结果认为,“高水分”的界定还需要科学依据;完善组织化产品评价指标体系有助于提高产品质量和开发新产品;多种植物蛋白复合挤压有助于改善产品的营养价值,丰富产品的种类。     

降温缓苏多级顺流粮食干燥工艺的模拟研究

针对现实多级顺流粮食干燥机在结构及使用上的缺陷,依据粮粒在降温过程中内部水分扩散方程的相关理论,提出一种降温缓苏与顺流加热干燥相结合的降温缓苏多级顺流干燥工艺,并进行了该干燥工艺与理想型多级顺流干燥工艺的模拟对比试验,证明这种新干燥工艺具有更容易保证粮食品质,节能高效的优越性.     

挤压引起食品特性变化的数学模型研究综述

挤压是一项有效的食品加工技术,物料在挤压机内既受到加热又受到剪切,经历的是一个非等温过程,且停留时间出现分布。正确建立挤压食品特性变化的数学模型是对产品质量进行预测和控制的基础,可以将描述挤压引起的食品特性变化的数学模型分为6类:流变模型、动力学模型、降解模型、膨胀模型、质构模型和统计模型。含水率、温度、停留时间分布(RTD)、时温历程、剪切历程等因素都可能对产品特性产生影响。该文详细论述了在建立前3种模型的过程中如何考虑这些因素的影响。该文最后简要论述了今后的研究方向。     

挤压制备高直链玉米淀粉脂工艺优化及结构功能特性

为提高淀粉-脂质复合物制备效率，拓宽其在低血糖指数食品中的应用，以高直链玉米淀粉和胡麻油为原料，双螺杆挤压为核心制备技术，复合指数为评价指标，采用单因素和正交优化试验获取最佳制备工艺条件，并对复合物结构及特性进行测定分析。结果表明，优化工艺参数为胡麻油与淀粉质量比0.24、喂料水分40%、机筒温度125 °C、螺杆转速150 r/min，在此条件下复合物的复合指数为85.63%。通过傅里叶红外光谱及形态学观察，表明胡麻油与淀粉分子发生结合，说明双螺杆挤压制备淀粉脂是可行的；挤压淀粉-脂质复合物表现较强的热稳定性、抗消化特性和较低的黏弹性。根据以上结果可知挤压处理促进淀粉与脂质分子的有效复合，进而改变淀粉分子的结构及理化特性, 研究结果可为淀粉-脂质复合物在低血糖指数食品中的应用提供参考。     

食品挤压机的研究现状

概述了挤压食品的工艺特点和产品,重点综述了国际食品挤压机的发展和研究现状,指出了国际的研究导向和国内的某些突破以及存在的问题,供研究参考。     

植物蛋白肉3D打印工艺参数优化

为提高植物蛋白肉3D打印品质,该研究探究了3D打印工艺参数对植物蛋白肉品质的影响。通过单因素试验,分析打印速度、喷嘴高度和挤压流量等3D打印工艺参数对植物蛋白肉的硬度、弹性和咀嚼性的影响规律。采用Box-Behnken Design响应面试验设计,分别建立硬度、弹性和咀嚼性的多元回归拟合模型,提出基于多目标烟花算法的植物蛋白肉硬度、弹性和咀嚼性的3D打印工艺参数优化方法。研究结果表明,打印速度为49.06 mm/s、喷嘴高度为1.21 mm、挤压流量为80.75 mm³/s时,植物蛋白肉硬度、弹性和咀嚼性分别为43.14 N、2.78 mm、75.92 mJ,与鸡肉品质相似度最高。优化结果与验证性试验结果相比,硬度误差为2.21%、弹性误差为5.48%、咀嚼性误差为2.52%。该研究通过3D打印工艺参数的优化改善了植物蛋白肉的品质,可为高品质植物蛋白肉研究与生产提供参考。     

小麦分蘖形态学特征X射线-CT无损检测

针对传统小麦分蘖形态学特征需采用人工接触或有损方法获取,不仅过程繁琐、主观性强而且会影响小麦后续生长。为实现小麦分蘖性状快速、准确、无损测量,该文提出一种基于X射线断层成像的小麦分蘖形态学特征提取方法。首先构建了小麦分蘖X-ray CT断层扫描成像系统,采用滤波反投影(filtered back projection,FBP)断层重建算法和图形处理单元(graphics processing unit,GPU)加速算法快速获取小麦分蘖茎秆断层图像,设计了专门的分蘖图像分析算法实现对小麦分蘖形态学特征参数(分蘖数、分蘖角度、分蘖茎粗和分蘖壁厚)的无损检测。该研究对107株小麦植株测量结果表明:分蘖数测量准确率可达100%,分蘖角度、茎粗和壁厚的平均测量误差分别为3.65%,4.84%和7.86%。该技术相较于人工测量方法和石蜡切片方法,能够对小麦分蘖形态学特征进行较为精准无损检测,实现单株测量效率约200 s,对于小麦功能基因组和抗倒伏能力品种的筛选具有重要的研究意义。     

Extrusion of Cross‐Linked Hydroxypropylated Corn Starches II. Morphological and Molecular Characterization

A series of cross‐linked hydroxypropylated corn starches were extruded with a Leistritz micro‐18 co‐rotating extruder. Extrusion process variables including moisture (30, 35, and 40%), barrel temperature (60, 80, and 100°C), and screw design (low, medium, and high shear) were investigated. Scanning electron microscopy (SEM) of extruded starches showed a gel phase with distorted granules and granule fragments after extrusion at 60°C. After extrusion at 100°C only a gel phase was observed with no granular structures remaining. High performance size exclusion chromatography (HPSEC) equipped with multiangle laser light‐scattering (MALLS) and refractive index (RI) detectors showed extruded starches degraded to different extents, depending on extrusion conditions. The average molecular weight of the amylopectin of unextruded native corn starch was 7.7 × 10⁸. Extrusion at 30% moisture, 100°C, and high shear reduced the molecular weight of amylopectin to 1.0 × 10⁸. Hydroxypropylated normal corn starch extruded at identical conditions showed greater decreases in amylopectin molecular weight. With the addition of cross‐linking, the amylopectin fractions of the extruded starches were less degraded than those of their native and hydroxypropylated corn starch counterparts. Similarly, increasing moisture content during extrusion lowered amylopectin degradation in the extruded starches. Increasing temperature during extrusion of cross‐linked hydroxypropylated starches at high moisture content (e.g., 40%) lowered amylopectin molecular weights of the extruded starches, whereas increasing extrusion temperature at low moisture content (30%) resulted in less degraded molecules. This difference was attributed to the higher glass transition temperatures of the cross‐linked starches.     

Leavened dough processing by supercritical fluid extrusion (SCFX)

Yeast-leavened dough processing is semicontinuous due to the requirement for fermentation at constant temperature and humidity. Also, new regulations on the emission of alcohols are becoming burdensome on the baking industry. Extrusion processing of dough with supercritical carbon dioxide (SC-CO(2)) is envisioned to alleviate emission problems and to decrease production time by eliminating fermentation. A bread dough formulation with 50% (w/w) moisture was leavened by injecting 1.5% (w/w) SC-CO(2) in a twin-screw extruder at 37 degrees C. Specific mechanical energy input was 260 kJ/kg. The operating apparent shear rate range was 60-260 s(-1). SCFX-leavened dough density (420-430 kg/m(3)) was in good agreement with values reported for similar doughs. The flow behavior index, obtained by an on-line slit rheometer, was 0.49 for the nonleavened control and 0.63 for the SCFX-leavened dough. Apparent viscosity of the SCFX-leavened dough varied from 37 to 23 Pa-s. This new continuous process offers attractive possibilities for industrial applications if further developed.     

Effects of Corn Sample,Mill Type,and Particle Size on Corn Curl and Pet Food Extrudates

The effects of corn sample, grinder type, and particle size of ground corn on the extrusion of corn curls and pet food were studied. Extrusion runs were conducted using a twin-screw extruder. Properties of corn curl and pet food extrudates were affected significantly by corn samples obtained from different parts of the country (Nebraska, Illinois, and Texas), even though grinding and extrusion parameters were held constant. The type of grinder used to grind the corn had an effect on extrusion properties. The volumetric expansion index (VEI) of extrudate from pin-milled samples was lower than that of extrudate from the same corn ground in a hammer mill or roller mill. Small particle size, obtained by grinding corn in a hammer mill with different screen sizes, produced extrudate with a significantly higher VEI than extrudate from coarse- or medium-sized particles.     

Waxy Soft White Wheat: Extrusion Characteristics and Thermal and Rheological Properties

Waxy wheat flour was analyzed for its thermal and rheological properties and was extruded to evaluate its potential for extruded products. Normal soft white wheat flour was analyzed with the same methods and same extrusion conditions to directly compare differences between the two types of flour. Through DSC analysis, waxy wheat flour was found to have a higher gelatinization peak temperature of 66.4°C than normal wheat at 64.0°C, although the transition required 2.00 J/g less energy. Rapid visco‐analysis indicated that the waxy wheat flour pasted much more quickly and at lower temperatures than the normal wheat flour. Preliminary extrusion experiments were conducted to determine the optimal screw profile for waxy wheat with respect to maximum radial expansion. The optimum screw profile was used for extrusion trials with varying flour moisture (15–25% wb) and extruder screw speed (200–400 rpm) while monitoring process conditions including back pressure and specific mechanical energy. Physical properties of the extrudates were then studied. The radial expansion ratios of the waxy wheat extrudates exceeded those of the normal wheat extrudates by nearly twice as much, and it was observed that the waxy wheat flour took less energy in the form of fewer shear screw elements to expand. The waxy wheat extrudates also exhibited significantly higher water solubility and less water absorption than the normal wheat extrudates owing to solubilizing of the extrudates. The results of our study indicate that waxy wheat flour may be a viable ingredient for creating direct expanded products with less energy.     

挤压加工参数对重组米生产过程及产品膨胀度的影响

为了考察重组米生产过程中挤压加工变量对几种系统参数与产品膨胀度的影响,试验以杂交籼米（9?718品种）为原料,利用响应面模型,以螺杆转速、进料速度、进料含水率以及末端机筒温度为输入变量,以挤压系统参数（物料温度、模头压强、扭矩、比机械能和产品含水率）和重组米膨胀度为响应变量,探索在重组米生产过程中加工变量与系统参数及产品膨胀度的关系。结果表明,压强、比机械能和产品膨胀度都受到4个挤压变量的显著影响,但是物料温度受进料速度影响不显著,马达扭矩受末端机筒温度影响不显著,产品含水率仅受进料含水率的显著影响。比机械能与螺杆转速正相关,与进料速度、进料含水率和末端机筒温度负相关。所得二次回归模型均拟合良好,建立的挤压数学模型可应用于重组米生产,为重组米工业化生产的过程预测和产品性质预测提供参考。     

Extrusion Chemistry of Wheat Flour Proteins: II. Sulfhydryl-Disulfide Content and Protein Structural Changes

Effects of twin-screw extrusion conditions on wheat flour proteins were studied, using a two-level fractional factorial experimental design (11 and 14% protein content, 160 and 185°C, 16 and 20% moisture, 300 and 500 rpm screw speed, mass flow rate of 225 and 400 g/min). Total protein detectable by solid-phase bicinchoninic acid assay decreased slightly after extrusion, with greatest protein loss at 16% moisture and 160°C. Sulfhydryl content of both flours increased after extrusion at 185°C and 16% moisture with moderate specific mechanical energy (SME ≈ 400–600 kJ/kg) or 160°C and 16% moisture with high SME (SME > 1,000 kJ/kg). Disulfide bonds increased under comparable conditions but with moderate shear (SME = 510–540 kJ/kg). At 20% moisture and either temperature, sulfhydryl and total thiol contents decreased without corresponding increases in disulfides. Reversed-phase HPLC indicated gliadins were the fractions most affected by extrusion; high molecular weight glutenin subunits also were affected. Changes in gliadins were extensive at 185°C and 16% moisture and were minimal at 160°C and 20% moisture. SDS-PAGE confirmed the disappearance of protein bands and appearance of new material at low and high molecular weights, presumably resulting from polypeptide fragmentation followed by random radical recombination. Both protein fragmentation and cross-linking appeared to involve free radicals.     

Using an In‐Line Slit‐Die Viscometer to Study the Effects of Extrusion Parameters on Corn Melt Rheology

An in‐line slit‐die viscometer (SDV) was used to measure the viscosity of a melt extrudate independently of the extruder operating conditions. The melt produced by extrusion of the corn grits followed a power law rheological model. The viscosity of the melt and extrusion parameters such as specific mechanical energy (SME), torque, and die pressure decreased with increasing moisture content. The degree of starch gelatinization increased when barrel temperature increased from 90 to 130°C. At temperatures higher than 130°C, most of the starch had gelatinized. The increase in barrel temperature, however, resulted in small changes in the apparent viscosity of the melt, until a maximum of ≈130°C. At a constant feed rate, SME increased and torque decreased when screw speed increased due to the shear thinning behavior of the melt. At a constant screw speed, the torque increased and SME decreased with increasing feed rate. This was due to a decrease in apparent viscosity of the melt at higher feed rates. SME is not an independent extrusion variable and should be used with caution either when predicting the effect of thermomechanical treatment of the product or as the key and only variable for controlling the food extrusion process.     

Effect of Particle Size and Moisture Content on Viscosity of Fish Feed

A model was developed for the influence of particle size on the extrusion of a fish feed and the physical characteristics of the extrudates evaluated. The study was conducted using factorial experiments in a fractional replication design for four variables with three levels, and one‐third of the replicates (3⁴ factorial in 27 units) were examined in a laboratory extruder. The torque‐screw speed measurement was used to develop a viscosity model equation that considered different shear rates, product temperature, initial moisture content, and particle size. When particle size decreased, the apparent viscosity became smaller. The barrel pressure was important in producing extrudate with a uniform volume over the range of processing conditions tested because it had a strong correlation with the volumetric expansion. The material with lower moisture and larger particles caused the specific mechanical energy to increase. The viscosity model developed in this study can be applied to the development of large‐scale extrusion models that determine the effect of particle size on the feed material extrudates.