桃树胶的性质研究

本试验在初步完成提胶工艺所获得的成品放的基础上，对桃树胶的一些主要性能进行了探索，试验表明，该胶的溶解性较好，随波浓度的增加，粘度亦增大，在弱酸性条件下有较大粘度。感官性质：溶液无色透明，口感粘稠，味谈。     

Uniaxial Extensional Viscosity During Extrusion Cooking from Entrance Pressure Drop Method

Uniaxial extensional viscosity of corn meal at moisture contents of 30 and 35% (dry weight basis) and temerature of 160 and 180°C was estimated from entrance pressure'drop measurements during extrusion cooking. The value of the shear component of the entrance pressure drop was an order of magnitude below that of the extensional component. Food doughs exhibited shear thinning and extension thinning behavior during processing conditions used. Increasing moisture and temperature decreased extensional viscosity at higher extension rates. The Trouton ratio ranged from 25 to 50 and was affected by product moisture content, barrel temperature, and deformation rate.     

Organic Acid Changes During Ripening of Processing Peaches

Organic acids and their changes during peach (Prunus persica L. Batsch) fruit ripening were quantified by HPLC for clingstone culti-vars,‘Babygold 5’and‘Babygold 7′, and a freestone cultivar,‘Cresthaven’. At full maturity,‘Babygold 5’and‘Babygold 7’had about 60% malic, 20% citric and 19% quinic acid; whereas‘Cresthaven’had similar amounts of all three organic acids (37, 3.5 and 28%, respectively). During fruit ripening,‘Babygold 5’and‘Babygold 7’increased in malic acid and decreased in citric and quinic acids, whereas,‘Cresthaven’showed little change in these organic acids.     

螺杆挤压过程食品流动能力计算与综合修正

螺杆挤压推料是食品加工过程中完成食品的输送、挤压与混合的常用工序,确定螺杆挤压过程食品流动能力,是为研究食品加工工艺及设备提供必要的条件。本文针对具有幂律非牛顿流体特性的一类食品,对前人的螺杆挤压流动模型及公式进行了简化与扩展,并提出了一种模型修正法--综合系数修正法。     

RHEOLOGY OF DIFFERENT FORMULATIONS OF MILK CHOCOLATE AND THE EFFECT ON COATING THICKNESS

This work characterized the flow properties and investigated the effect of grind, emulsifier type and emulsifier level on the coating thickness of milk chocolate. Rheological properties were characterized using a concentric cylinder viscometer according to the method recommended by the International Confectionery Association. The thickness of the chocolate on dip‐coated acrylic plates was obtained by a gravimetric method. A three‐way analysis of variance was performed for the coating thickness. All three factors were significant; the thickness of the chocolate coating was greater for fine grind, soy lecithin for emulsifier and for low concentrations of emulsifier. The thicknesses were well predicted using the model with the Casson model parameters from the rheological characterization.     

玉米产品挤压膨化特性的影响因素

以优质的玉米为原料,采用挤压膨化技术,研制出玉米膨化产品。通过正交试验确定了挤压温度、物料水分含量、螺杆转速对产品膨化物糊化度的影响,并找出了最佳工艺参数值:挤压温度160℃,物料水分含量20%,螺杆转速300r/min。     

不同温度与包装对鹰嘴蜜桃贮藏效果的影响

本研究以连平鹰嘴蜜桃为材料,探究了PVC自发气调保鲜袋、PE自发气调保鲜袋和NP纸袋三种包装材料在常温和2±1℃低温贮藏条件下对采后鹰嘴蜜桃呼吸强度、乙烯释放量、硬度、失重率、好果率、可溶性固形物、可滴定酸和维生素C变化的影响。结果表明:低温和PVC、PE、NP包装都能够较好的抑制果实的呼吸强度、降低乙烯释放量,提高好果率和保持较好的贮藏品质。其中PVC结合低温贮藏效果最好,在降低果实呼吸强度和乙烯释放量的同时,将呼吸跃变发生时间和乙烯高峰释放时间推迟了4 d;贮藏40 d后鹰嘴蜜桃果实的可溶性固形物含量仍能维持在9.51%,可滴定酸含量为0.23%,维生素C含量为5.90 mg/100 g,果实硬度为8.20 kg/cm2,果实失重率为3.10%,好果率达84.50%。     

Kinetics of Thermomechanical Destruction of Thiamin During Extrusion Cooking

Maize grits were extrusion cooked in a CM45-F conical, counter-rotating twin-screw extruder, at different barrel temperatures (140–200°C), feed moistures (11.8–14.2% w.b.), feed rates (37–51 kg/h), screw speeds (65–81 rpm), and initial thiamin concentrations (9–93 mg/kg). Residence time distribution was measured by a dye tracer technique. A first-order rate equation was used to model the reaction kinetics, which allowed the calculation of the destruction rate constant using residence time distribution curves. The k-values were most dependent on barrel temperature, feed moisture, and screw speed. The destruction rate constant of thiamin during extrusion cooking was a function of product temperature and shear stress.     

淀粉反应挤出改性及挤出过程中淀粉颗粒变化

原淀粉经各种改性后性质发生变化,使其应用范围更加广阔。淀粉改性方法有化学法、物理法和生物法,其中化学法改性工艺比较成熟,但改性过程需使用大量化学试剂,应用受到限制,而物理法改性不存在这个问题。反应挤出法是物理改性一种,作为一种新技术,在淀粉改性中有很多优点。该文主要介绍反应挤出政性原理、特点、应用现状、影响因素及挤出过程中淀粉颗粒变化。     

苦荞麦粉的挤压膨化特性研究

本文研究了苦荞麦粉在QPS65X2型双螺杆挤压膨化机膨化时,螺杆转速,含水量,进料量对膨化度的影响,结果表明化度随含水量增加而下降,随杆转速,进料量的增加而上升,研究了苦荞麦粉与其它辅料（大豆,芝麻,南瓜粉）的配比,螺杆转速,进料量,含水量协同挤压膨化,结果表明：苦荞麦心粉与皮粉的比例为70：30,螺杆转速为350r/min,进料量为450g/min,水分含量为15％时膨化效果最好;苦荞麦粉与大豆的比例为95：5,螺杆转速为350r/min,进料量为350g/min,水分含量为10％时膨化效果最好;苦荞麦粉与芝麻的比例为98：2,螺杆转速为350r/min,进料量为450g/min,水分含量为15％时膨化效果最好;苦荞麦粉与南瓜的比例为95：5,螺杆转速为350r/min,进料量为550g/min,水分含量为10％时膨化效果最好。     

反应挤出技术在变性淀粉生产中的应用

主要阐述了反应挤出的原理和特点，并且概括了当前用反应挤出法生产氧化、酯化、接枝、交联和醚化等变性淀粉的现状。认为反应挤出技术是变性淀粉生产中一种经济可行的方法。     

Tomographic Techniques for Measuring Fluid Flow Properties

Experimental fluid velocity profiles can be readily obtained by using tomographic techniques. Combining measurements of a fluid velocity profile with a simultaneous pressure drop permits the evaluation of rheological properties. In order to control a process and to assure product quality, it is useful to monitor the rheological properties in‐line or on‐line. Two tomographic techniques, magnetic resonance imaging (MRI) and ultrasonic Doppler velocimetry (UDV), were used to obtain velocity profiles for a 65.7 °Brix corn syrup solution and a 4.3 °Brix tomato juice. The UDV technique provided velocity profiles that compared well with the MRI method. For the corn syrup, the shear viscosity of 1.37 Pa‐s (UDV) and 1.51 Pa‐s (MRI) agreed well with the offline measurement of 1.57 Pa‐s. The tomato juice was best characterized as a Bingham plastic fluid. The yield stress ranged from 4.44 Pa to 4.70 Pa, which matched well with the off‐line value of 4.50 Pa. The strengths and limitations of both techniques are presented.     

桃仁多肽螯合亚铁的抑菌活性及结构表征

分别对亚铁离子与不同分子质量桃仁多肽和不同植物多肽形成的螯合物,以及亚铁、锌、钙和镁离子与桃仁多肽形成螯合物的抑菌活性进行比较,并对螯合物进行结构表征。结果表明：小分子质量（小于5 000 Da）桃仁多肽PKP3组分与亚铁离子螯合后的抑菌活性强于大分子质量（大于10 000 Da）桃仁多肽亚铁螯合物,桃仁多肽与亚铁离子和锌离子螯合后有较强抑菌活性;4 种植物多肽与亚铁离子所形成的螯合物间的抑菌活性存在显著性差异（P＜0.05）,其中桃仁多肽螯合亚铁和小麦多肽螯合亚铁的抑菌活性最强,对大肠杆菌的最小抑菌浓度（minimum inhibitory concentration,MIC）均为5.0 mg/mL,对金黄色葡萄球菌的MIC分别为2.5、5.0 mg/mL;傅里叶变换红外光谱分析表明亚铁离子与4 种植物多肽分子的—COO－、N—H、C＝O形成配位键,多肽与亚铁离子能有效地螯合形成多肽螯合亚铁。     

Flow Behavior of Milk Chocolate Melt and the Application to Coating Flow

ABSTRACT: The rheological properties of chocolate, especially shear viscosity and yield stress, are important control parameters for enrobing processes in confectionery manufacture. The rheological parameters of molten milk chocolate were measured at 42°C during steady pipe flow using a magnetic resonance imaging (MRI) viscometric method. The experimental method combines shear rate values obtained from an MR velocity image and shear stress values obtained from an independent pressure drop measurement. The experimental factors were emulsifier type and emulsifier level. The rheogram data were fit by the Casson model to yield the Casson yield stress and plastic viscosity. The Casson yield stress ranged from 1.9 to 15.0 Pa; the Casson viscosity ranged from 6.0 to 14.6 Pa s as a function of emulsifier content. The rheological parameters were incorporated into a drainage theory model to predict coating thicknesses in the enrobing process. The model was solved numerically and yielded good approximations to the experimental values that were between 1.1 to 2.7 mm.     

Nucleation and Expansion During Extrusion and Microwave Heating of Cereal Foods

Expansion of biopolymer matrices is the basis for the production of a wide variety of cereal foods. A limited number of manufacturing processes provide practical solutions for the development of an impressive variety of expanded products, just by changing process variables. It is therefore essential that the mechanisms involved in expansion are well known and controlled. This paper summarizes the knowledge of nucleation and expansion in extruded and microwaved products available to date. The effect of processing conditions and properties of the biopolymeric matrix on nucleation and expansion are discussed. Moisture content enables the glassy polymeric matrix to turn into rubbery state at process temperatures, which allows superheated steam bubbles to form at nuclei and then expand, expansion being governed by the biaxial extensional viscosity of the matrix. Nucleation and expansion theories are presented along with quantitative data that support them.     

挤压对豌豆淀粉的消化及理化特性评价

本文旨在探究单螺杆挤压对豌豆淀粉消化特性的作用机理,阐述物料水分、螺杆转速和挤出温度影响规律,并通过扫描电子显微镜,X-衍射,快速黏度仪从分子晶型、结构、黏度性质等角度,揭示豌豆抗性淀粉的理化性质.结果表明,豌豆淀粉经挤压处理,快消化淀粉含量显著降低,抗性淀粉和慢消化淀粉含量也发生不同程度影响,其中在水分含量26％,螺...     

Flow Distribution of Food Materials in an Annular Extrusion Die

ABSTRACT: The objective of this study was to determine the effects of die geometry, food material and operating parameters on flow distribution in an annular extrusion die. A diverging annular die with a conical insert was designed such that the eccentricity of the central conical core could be maintained at 0, 1, and 2 mm. Corn syrup, cornstarch, cornmeal, and wheat flour were extruded through the die using a twin-screw extruder at varying mass flow rates. It was found that perfect geometrical alignment was very critical in achieving flow uniformity, and should be considered as the important factor in practical applications. The type of food material and mass flow rate had negligible effects on the flow distribution.     

Salmonella Inactivation During Extrusion of an Oat Flour Model Food

Little research exists on Salmonella inactivation during extrusion processing, yet many outbreaks associated with low water activity foods since 2006 were linked to extruded foods. The aim of this research was to study Salmonella inactivation during extrusion of a model cereal product. Oat flour was inoculated with Salmonella enterica serovar Agona, an outbreak strain isolated from puffed cereals, and processed using a single‐screw extruder at a feed rate of 75 kg/h and a screw speed of 500 rpm. Extrudate samples were collected from the barrel outlet in sterile bags and immediately cooled in an ice–water bath. Populations were determined using standard plate count methods or a modified most probable number when populations were low. Reductions in population were determined and analyzed using a general linear model. The regression model obtained for the response surface tested was Log (N_R/N_O) = 20.50 + 0.82T ? 141.16a_w – 0.0039T² + 87.91a_w² (R² = 0.69). The model showed significant (p < 0.05) linear and quadratic effects of a_w and temperature and enabled an assessment of critical control parameters. Reductions of 0.67 ± 0.14 to 7.34 ± 0.02 log CFU/g were observed over ranges of a_w (0.72 to 0.96) and temperature (65 to 100 °C) tested. Processing conditions above 82 °C and 0.89 a_w achieved on average greater than a 5‐log reduction of Salmonella. Results indicate that extrusion is an effective means for reducing Salmonella as most processes commonly employed to produce cereals and other low water activity foods exceed these parameters. Thus, contamination of an extruded food product would most likely occur postprocessing as a result of environmental contamination or through the addition of coatings and flavorings.     

桃仁多肽螯合亚铁的结构表征及体外模拟消化

以桃仁蛋白酶解分离所得多肽和氯化亚铁为原料,研究不同品种多肽、铁盐和不同分子质量多肽组分对螯合率的影响,以及对多肽螯合亚铁(PKP3-Fe)的结构表征和体外模拟消化的影响。研究结果表明,桃仁多肽与亚铁离子的螯合率显著高于(P<0.05)大豆多肽、玉米多肽和鱼胶原蛋白肽,氯化亚铁和小分子质量桃仁多肽具有更高的螯合率。桃仁多肽与亚铁离子螯合前、后的紫外光谱和荧光光谱图对比显示,螯合后紫外吸收峰位置、峰值均发生迁移,内源荧光强度明显减弱,有螯合物形成;傅里叶红外光谱分析表明,亚铁离子与桃仁多肽中的-COO-、N-H、C-N、O-H形成配位键;扫描电镜图显示,桃仁多肽螯合后微观结构发生明显改变,有光滑球状颗粒生成。在模拟胃部消化过程中,PKP3-Fe的铁离子释放率显著低于硫酸亚铁片和乳酸亚铁片(P<0.05),避免了大量氢氧化铁沉淀的生成,进入模拟肠液后,PKP3-Fe仍有相当部分成分在肠道中以离子态或与多肽以螯合物的状态存在,能更好地被人体吸收利用。     

Capillary Flow and Rheology Measurements on Chocolate Crumb/Sunflower Oil Mixtures

ABSTRACT: Rates of penetration of sunflower oil into beds of 3 types of chocolate crumb have been measured and the results analyzed using the Washburn-Rideal theory. The data show that the rates are a function of both the specific surface area of the crumb particles and their surface composition. Addition of an emulsifier to the oil reduces the penetration rate into the crumb made with full-cream milk powder, whereas for crumbs containing skimmed-milk powder, rates go through a maximum with increase of emulsifier concentration. Rheological data for dispersions of crumb in oil were fitted to the Casson equation. An inverse correlation was found between penetration rates and Casson yield values.