Physico-Chemical Characteristics of Rice Bran Processed by Dry Heating and Extrusion Cooking

Abstract

Rice bran was stabilized by dry heat and extrusion cooking method. Physico-chemical, functional, and storage characteristics of stabilized rice bran were evaluated. The rice bran stabilization affected its crude fat and crude ash contents significantly, whereas the other constituents remained almost unchanged. The content of reducing, nonreducing, and total sugars remained unaffected and did not differ significantly from raw rice bran. The neutral detergent fiber (NDF) contents of raw and dry-heat treated rice bran did not differ significantly. However, after extrusion stabilization, the NDF increased significantly. Similar effects were observed in composition of gum fiber and total fiber. The stabilization of rice bran had a significant reduction in lysine and phytic acid content. Bulk density and water absorption were higher in extruded stabilized rice bran than dry-heat treated bran. Protein solubility was maximum in raw bran, whereas damaged starch content was higher in stabilized bran. Color of the extruded bran was dark brown, whereas that of dry-heat stabilized was light brown. It was observed that dry-heat treated bran was stored up to 30 days, whereas extruded bran was stored up to 60 days without any changes in the free fatty acid content.     

Properties of Soybean-Corn Mixtures Processed by Low-Cost Extrusion

Ground soybeans and corn at ratios 60:40, 70:30, 80:20, and 100:0 soybean :corn were extruded with an Insta Pro 600 extruder. Initial moisture content was adjusted to 10%. Extruder exit temperatures were 127, 138, 149, and 160°C. Soybean trypsin inhibitor activity was destroyed 48.9 to 98.8% as exit temperature increased. Extrusion temperature had no major effect on the tocopherol isomers. Lipoxygenase was completely inactivated by extrusion. In vitro protein digestibilities of samples extruded at 127°C were significantly lower than samples extruded at higher temperatures. Residual lipase activity ranged from 2.7 to 63.7 micromoles H⁺.min^_I.g⁻¹.     

Gelatinization of Corn Grits by Roll Cooking,Extrusion Cooking and Steaming

A large variety of cooked corn products can be prepared on rolls, in extruders or by steamcooking. Slight changes in operating conditions of the cooking equipment can bring about significant changes in absorption, solubility and viscosity properties of the cooked products. Production of processed materials with high water absorption and retaining high cooked paste viscosity appears more difficult by direct steaming than by use of the other methods. Roll-cooking should be better than extrusion-cooking for preparing materials of maximum water absorption and minimum water solubility. Such materials are well suited either for thick gruels or for industrial thickening or gelling agents. Extrusion-cooking should be better for preparing materials of minimum water absorption and maximum water solubility. Such materials are well suited either for beverages or for industrial uses where adhesive properties are desired. Steamcooking should be suitable for preconditioning before roll- or extrusion-cooking, but it appears that heating time must be held to a minimum.     

Heating Characteristics of Whole Kernel Corn Processed in a Steritort

Cans of whole kernel corn in brine and vacuum-packed corn were heated in an FMC Steritort and in a still retort. Two can sizes for each product were processed to simulate two commercial agitating processing machines. The sterilization values (F_o) and heat penetration factors (j, f_h, f₂) were determined from time-temperature data and were influenced by reel rotational speed, corn fill weight, and brine fill or container headspace. For both products, optimum heat penetration for agitated processing occurred at a ratio of brine-to-corn fill weights of about 35% (normal for vacuum-packed products). Above a threshold value, increasing reel rotational speed did not significantly enhance heating, and with the accompanied reduction in retention time in continuous retorts, F_o values would actually be lowered. Sterilization values were somewhat reduced because of overfills of both corn and brine. For the vacuum-packed product, vacuum level significantly influenced heat penetration only for the still processes.     

Extrusion Cooking of Corn/Soybean Mix in Presence of Thermostable α-Amylase

A fractional factorial experiment of a 3⁴ second order orthogonal design was used to study properties of extrusion processed corn/soybean (70/30%, w/w) mixtures in presence of thermostable α-amylase. The viscosity of gruels made from extrudates of corn/soybean mixtures with no added α-amylase was more than 1000-fold higher than that of products extruded with added enzyme. Changes in viscosity and water solubility and absorption indices of slurries from extrudates made under different conditions, indicated enzymatic starch hydrolysis was increased in the extruder when a-amylase was included. The results should be useful in selecting extrusion conditions to yield low viscosity-high nutrient density gruels from extruded products.     

挤压膨化降解糙米中黄曲霉毒素B1

目的：研究挤压工艺参数对黄曲霉毒素B1（aflatoxin B1,AFB1）降解率的影响,为建立粮食产品中AFB1的挤压降解技术提供依据。方法：采用双螺杆挤压机挤压膨化污染AFB1的糙米,分析挤压温度、物料水分、喂料速率和螺杆转速对糙米中AFB1降解率的影响,并通过优化工艺得到最佳工艺条件。结果：单因素试验机筒温度170 ℃时,AFB1降解率最高为37.1%;物料水分24%时,AFB1降解率最高为37.2%;喂料速率30 g/min时,AFB1降解率最高为37.8%;螺杆转速200 r/min时,AFB1降解率最高为39.2%;挤压降解糙米中AFB1正交试验的最佳工艺条件为机筒温度180 ℃、物料水分24%、喂料速率30 g/min、螺杆转速160 r/min,其降解率为48.6%。挤压过程中机筒温度极显著影响AFB1降解,物料水分显著影响AFB1降解,喂料速率和螺杆转速对AFB1降解的影响不显著。结论：挤压膨化加工能有效降解糙米中的AFB1。     

Rice Bran Stabilization by Extrusion Cooking for Extraction of Edible Oil

An extrusion cooking procedure was developed which produces stabie rice bran which shows no significant increase in free fatty acid content for at least 30–60 days. In the optimum process, 500 kg/hr of 12 - 13% moisture bran was extruded at 130°C and held 3 min at 97 - 99°C before cooling. Stabilized bran contained 6 - 7% moisture and was in the form of small flakes with 88% larger than 0.7 mm (25 mesh). Energy required to extrude the bran was 0.07 - 0.08 kW-hr/lcg bran, and wear on the extrusion surface indicated a life of 500 hr for the cone and 1000 - 2000 hr for other wearing parts.     

Corn Alkaline Cooking Properties Related to Grain Characteristics and Viscosity (RVA)

The relationship between kernel properties and alkaline cooking characteristics of 14 corn cultivars with different kernel characteristics was evaluated. Corn hardness was measured by abrasion (TADD), flotation, subjective ratings and a viscometric technique (RVA). Hard corn required longer time for cooking as both cooking and steeping hydration rates were lower compared to soft corn. RVA viscosity measurements were correlated with hardness from TADD, flotation and subjective tests, and alkaline cooking parameters. The rate of water uptake during simmering was correlated with RVA viscosity slope. Hard corn endosperm particles consistently required longer time for hydration and gelatinization of starch to develop viscosity. RVA data complemented flotation hardness data to predict cooking properties. RVA could be used as a model to predict cooking properties of corn.     

响应曲面法对双螺杆挤压蒸煮玉米粉条件的优化

以普通玉米粉为原料,通过双螺杆挤出对玉米粉进行改性,探讨高水分条件下物料含水量、挤出温度、螺杆转速对挤出物糊化度的影响,并建立物料含水量(X1)、挤出温度(X2)、螺杆转速(X3)之间的数学模型,即Y＝96.97－1.49X1－1.21X2－1.85X3－0.37X1X2－1.15X1X3－2.35X2X3－2.20X12－2.50X22－3.77X32,确定了最佳蒸煮条件为含水量34%、挤出温度139℃、螺杆转速223r/min。在此条件下,玉米粉的糊化度为97.5%,与理论预测值基本相符。     

Gelatinization Characteristics of a Cassava/Corn Starch Based Blend during Extrusion Cooking Employing Response Surface Methodology

The gelatinization characteristics of a cassava/corn starch based blend with relatively high moisture content during cooking extrusion were studied. The study was carried out by using Response Surface Methodology. The results showed that the die temperature T_d (°C) was the main influencing factor for the starch gelatinization, and the feed rate of the materials V_f (g/min) was another minor one. Because of the high material moisture content during extrusion the moisture content M_c (%) influenced the gelatinization degree not so obviously. The residence time distribution of the mass during extrusion were studied as well as discussed as a influencing factor on the gelatinization results.     

Low Moisture Extrusion: Effects of Cooking Moisture on Product Characteristics

A commercial Creusot-Loire BC-105 twin-screw expanded dry pet food extruder was operated to provide extruded moistures between 7.9% and 12.4% at constant product density. Low moisture extrusion decreased product uniformity 45% and product shape roundness by 70%. It increased air ceil size 41% and internal fissuring by 25%. After drying all samples to low moisture, the samples extruded at a low initial moisture were more fragile with 15% lower ultimate strength as measured by crushing with an Instron testing machine.     

Investigation of the Nucleation During Extrusion Cooking of Corn Starch by A Novel Nucleation Die

In this paper, a novel method for the investigation of nucleation in expanding starch-based melts is introduced. Therefore, corn starch was extruded by a twin screw extruder. A long slit die, which facilitated the formation of a nucleation area to extend nucleation, was mounted at the exit of the extruder. The temperature of the nucleation die (160–190 °C), the moisture content of the starch melt (17–27 %), and the slit height (4 and 10 mm) were varied to investigate the effect of pressure profile and shear rates on nucleation. The pore size distributions of the samples were determined by image analysis of the cross-sections. The influence of temperature, moisture content, and slit height on nucleation was investigated by analysis of the resulting pore size distribution. We found two totally different types of product: a product with few big pores and a product with small and evenly distributed pores. In general, small pores were achieved when the vapor pressure was reached already at the earlier stages of the nucleation die. The addition of nucleating agents, such as droplets or solid particles did not change the appearance of the products significantly. Applying a nucleation area such as introduced in our study enables further investigation of the mechanisms of nucleation.     

Yield and Quality of Soymilk Processed by Steam-Infusion Cooking

Traditional soymilk is boiled for approximately 60 min at 99°C pH 6.7, which reduces trypsin inhibitor (TI) activity by more than 90% to improve nutritional value. We evaluated continuous, direct steam-infusion cooking that facilitated higher temperatures (99-154°C) than that traditionally used for cooking soymilk. At temperatures above 120°C in steam-infusion cooking we observed consistent temperature-dependent patterns in yields of soymilk, solids, and protein, characterized by an initial decrease, followed by a rise to maximum recovery, then by a final decrease. At 154°C, pH 6.7, maximum recovery occurred at the same point as did adequate in-activation of TI. As much as 90% of the slurry, 86% of the soybean solids, and 90% of the protein were recovered as soymilk after centrifuging at 1050 × G for 5 min. Under optimum conditions for steam-infusion cooking the soymilk also retained less than 8% residual TI activity, and less chemical browning. Using traditional cooking methods, about 72% of the slurry, 61% of soybean solids, and 73% of the protein are recovered.     

脱脂花生蛋白粉对玉米膨化功能特性的影响

以玉米为原料,脱脂花生蛋白粉为主要辅料,对其进行挤压膨化,对产品的功能特性及各分析指标的相互关系进行了研究。结果表明:产品的膨化度和吸水指数(WAI)均随着脱脂花生蛋白粉添加量的增加而下降,色泽逐渐加深,而水溶性指数(WSI)随着脱脂花生蛋白粉添加量的增加而增加,当脱脂花生蛋白粉添加量为25%时,产品的糊化度最高(98.92%),并具有较好的WAI和WSI;得到了各分析指标的关系模型。     

可视芯片检测大豆、水稻和玉米中的转基因成分

本研究选取9种常见转基因食品外源基因,设计了引物对与探针,并制备可视芯片。通过PCR对样品核酸进行扩增,将扩增产物与固定于可视芯片的特异性探针进行杂交分析,验证了芯片的特异性和重复性,并对检测芯片灵敏度进行测试。该方法可以一次检测出5种的常见转基因植物,且实验结果表明该方法高效、准确、简便、高通量、实用性强,灵敏度可达0.1%,并摆脱了基因芯片在杂交结果分析阶段对荧光扫描仪的依赖,杂交结果明显直观。     

复合米糠蛋白-卵白蛋白的起泡特性及相关机理分析

考察复合米糠蛋白（rice bran protein,RBP）-卵白蛋白（ovalbumin,OVA）的起泡特性,并分析在特定pH值与NaCl浓度下溶液与泡沫中不同蛋白质的物化性质,以阐述两种蛋白之间相互作用对起泡特性的影响。结果表明,在pH 4.0条件下,两种蛋白质在起泡能力上可以产生协同作用,且当RBP-OVA质量比为3:1时,添加1% NaCl后RBP-OVA复合蛋白的起泡能力和泡沫稳定性均显著增加;而在pH 7.0、无NaCl的情况下两种蛋白在起泡特性上没有表现出特别明显的协同作用,当添加1% NaCl后二者在起泡能力方面反而表现出一定的拮抗作用。通过对pH 4.0、1% NaCl条件下溶液与泡沫中蛋白质的物化性质进行分析可知,因两种蛋白质在物化性质方面具有一定的互补性,可通过蛋白质之间的相互作用从不同的物化性质角度改善RBP-OVA复合蛋白的起泡能力与泡沫稳定性。     

利用蜂蜡-米糠蜡制备大豆油凝胶油

利用蜂蜡、米糠蜡及其混合物作为凝胶剂,开发大豆油基凝胶油,并将制备的凝胶油与起酥油的物理性质进行比较。通过对2 种添加量下（5%、8%）蜂蜡和米糠蜡（蜂蜡与米糠蜡质量比10∶0、9∶1、8∶2、7∶3、6∶4、5∶5、3∶7、1∶9、0∶10）制备凝胶油的性质测定,结果发现随着米糠蜡比例的增加,凝胶油的硬度（11.9～140.4 g）呈先增加后减小再略有增加的趋势,当蜂蜡与米糠蜡比例为8∶2时,凝胶油的硬度最大,表明蜂蜡和米糠蜡混合后有协同作用;同时析油率采用离心的方法评价,结果发现米糠蜡比例较低（蜂蜡∶米糠蜡＞5∶5）时,凝胶油稳定,析油率为0%,且添加量8%条件下凝胶油的析油率低于普通起酥油。同时固体脂肪曲线、差示扫描量热法结果显示,在10～40 ℃条件下凝胶油的固体脂肪质量分数（8.5%～4%）显著低于起酥油（65%～20%）;融化峰值温度（50.2 ℃）高于起酥油（43.1 ℃）;X射线衍射结果显示8%蜂蜡-米糠蜡（8∶2）凝胶油样品的晶体形态（β’）与起酥油接近,都是细小的结晶。应用发现,蜂蜡与米糠蜡比例为8∶2,添加比例为8%的凝胶油具有较好的烘焙效果,使最终产品的固体脂肪含量大大降低,或许能为消费者拥有更健康的产品提供一条可行途径。     

Extrusion of Rice,Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V^® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V^® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.     

蒸煮处理对马铃薯全粉细胞结构及消化特性的影响

本文以新鲜马铃薯为原料,研究了蒸煮时间对马铃薯全粉的细胞结构、游离淀粉含量、理化性质及消化特性等的影响.结果表明:随着蒸煮时间的延长,马铃薯蒸煮悬浊液电导率从24μm/cm提高到1285μm/cm,全粉碘蓝值(BVI)从8.31增大到19.00,这表明马铃薯全粉中细胞的破损率提高,破损程度增大,胞内物质的释放量及游离淀...