Antioxidant Properties of Cocoa Beans (Theobroma cacao L.): Influence of Cultivar and Roasting Conditions

Effects of various roasting conditions on antioxidant properties of five Theobroma cacao L. varieties were investigated. The cocoa beans were roasted at four different temperatures (110–150°C) and three different air humidities (0.3–5.0%). The raw cocoa beans were characterized by high antioxidant activities. The antioxidant properties of the roasted cocoa beans varied markedly among the analyzed cultivars and geographical regions and were affected by roasting conditions. Generally, cocoa beans of the cv. Forastero from Brazil exhibited higher total phenolic content, free radical scavenging activity, and metal chelating ability than samples of the other analyzed cocoa varieties. Roasting at 110°C caused negligible changes in total phenolics content and antioxidant activity of cocoa beans, while almost all samples tended to have lower antioxidant potential when roasting temperature increased. The air humidity used in roasting did not affect the total phenolics content and antioxidant activity for lowest roasting temperature (110°C). Moreover, the obtained results revealed that thermal processing at the higher temperatures and elevated air humidity resulted in the higher antioxidant capacities. It was also found that the ferrous ion chelating activity of cocoa beans increased with the roasting temperature (in the range from 110 to 150°C), with the exception of cv. Trinitario from Papua New Guinea. The data showed that roasting at lower temperatures with humid air are more favorable in terms of preserving the bioactivity of roasted cocoa beans.     

微波焙烧在难选铁矿中的应用前景

由于微波加热具有加热速度快、反应灵敏、加热均匀、热效率高等优点,近几年在化学、化工和矿业方面的应用正逐渐开展。随着我国对铁矿石资源的需求越来越大,微博能在矿冶领域中潜在的重大作用越来越引起人们的高度重视。结合当前微波应用现状,阐述了微波焙烧在难选铁矿中的研究,重点介绍了微波在赤（褐）铁矿中研究现状,并指出微波在难选铁矿中的发展前景及研究趋势,同时对微波应用的前景进行展望。通过批量生产和技术提升大幅度降低工业用微波源的生产成本,从而降低微波高温设备的制造成本,微波高温设备将取代传统高温设备的市场,逐渐成为主流。      

试验用小型沸腾炉焙烧硫铁矿试验研究

用小型沸腾炉对硫含量50%的硫精矿进行了模拟沸腾焙烧试验,经过对焙烧温度、焙烧时间和进气压力的试验,确定了较佳工艺条件为:焙烧温度800℃,焙烧时间为5min,进气压为0.5MPa,得到的烧渣中硫含量低于0.30%,全铁含量大于64%。实验室模拟焙烧试验产出的烧渣质量较好,达到了高品位铁精矿的质量要求。     

某低品位锌铁矿石深度还原-磁选试验研究

针对广西某含锌13.00%、铁40.20%的低品位微细粒嵌布锌铁矿石,采用深度还原-磁选工艺,考察了还原剂用量、还原温度、还原时间、磨矿细度以及磁场强度等因素对锌、铁还原与铁回收的影响。研究结果表明,采用深度还原-磁选工艺可以有效处理该矿石,焙烧后铁的金属化率在92%以上,锌挥发率在97%以上,且最终获得了铁品位与铁回收率均在90%以上的铁精矿。     

低品位褐铁矿制粒一气基磁化焙烧研究

针对某铁品位为30．16％低品位褐铁矿,采用制粒-气基磁化焙烧-磁选工艺进行了试验研究。结果表明,对小球粒度为5～2mm,混合气体CO、CO2、N2体积比为1：2：2,磁化焙烧料层厚度200mm,焙烧温度为725℃,保温时间为10min的磁化焙烧产品进行磨选试验,在磨矿细度为-0．074mm占85％、弱磁选磁场强度为100kA／m情况下,可以获得铁品位为59．78％、铁回收率达86．19％的弱磁精矿。     

基于硫酸铵+硫酸混合助剂的石煤焙烧─酸浸提钒

为了了解含钒石煤焙烧过程助剂硫酸铵+浓硫酸对焙烧—酸浸提钒效果的影响,以四川广元某V2O5含量为0.82%的含钒石煤试样为研究对象(33.03%的钒赋存在有机质中,59.45%的钒赋存在硅酸盐矿物中),在混合助剂硫酸铵与浓硫酸的物质的量之比为1∶1的情况下,考察了焙烧温度、混合助剂添加量、试样的粒度和浸出温度对钒提取率的影响。结果表明,在添加硫酸铵+浓硫酸助剂的情况下,250℃焙烧导致试样中的云母相消失,伴随着硫酸铁铵、硬石膏新相的生成;焙烧温度上升到400℃,硫酸铁铵的衍射峰强度达到最强;继续提高焙烧温度至500℃,硫酸铁铵的衍射峰强度减弱;在320℃的焙烧熟料中有新相硫酸铝铵生成,至350℃处于增强阶段,至400℃硫酸铝铵相又全部消失。细度为-120目的试样按SO2-4与Al2O3+Fe2O3的物质的量之比3.5添加硫酸铵+浓硫酸,350℃下的焙烧熟料在90℃下进行硫酸酸浸,钒浸出率可达95.67%。     

Influence of the chemical structure on the thermal degradation of the glucosinolates in broccoli sprouts

Glucosinolates are secondary plant metabolites occurring in Brassica vegetables. Food processing significantly reduces glucosinolate content, among other things due to thermal degradation. As there is only little information about thermal glucosinolate breakdown, the influence of the chemical structure as well as the influence of different pH to thermal degradation of individual glucosinolates was studied by analysing desulphoglucosinolates with HPLC-DAD. Thermal degradation was forced by heating broccoli sprouts at 130 °C in dry medium, whereas the influence of the pH was studied by cooking at 100 °C in aqueous medium. Within each group of glucosinolates differences in thermal degradation were revealed. Within the sulphur containing aliphatic glucosinolates the oxidative state of the sulphur atom as well as the side chain length influenced the reactivity. Among the indole glucosinolates great differences in stability were observed. A hydroxyl function in the side chain generally seems to destabilise glucosinolates. Glucosinolates were most stable towards thermal treatment in neutral and slightly acidic medium, whereas they degraded more rapidly in basic medium.     

EFFECT OF INITIAL MOISTURE CONTENT ON THE THIN LAYER DRYING CHARACTERISTICS OF HAZELNUTS DURING ROASTING

ABSTRACT

Effect of initial moisture content on the thin layer drying characteristics of hazelnuts during roasting was described for a temperature range of 100-160°C, using several thin layer equations. The effective diffusivity varied from 2.8×10^?7 to 21.5×10^?7m²/s over the temperature and moisture range. Temperature dependence of the diffusivity coefficient was described by Arrhenius-type relationship. The activation energy for moisture diffusion was found to be 2703 kJ/kg, 2289 kJ/kg and 2030 kJ/kg for the initial moisture content of 12.3% db, 6.14% db, and 2.41% db, respectively. Two-term equation gave better predictions than Henderson and Pabis and Thompson equations, and satisfactorily described thin layer drying characteristics of hazelnut roasting. A generalised mathematical model with the linear temperature dependence for moistured, non-treated and pre-dried hazelnuts were also developed.     

Correlation Between the Stability of Chlorogenic Acids,Antioxidant Activity and Acrylamide Content in Coffee Beans Roasted in Different Conditions

The aim of this study was to determine the effect of different roasting conditions, including temperature, humidity, and roasting air velocity on acrylamide contents in roasted Robusta coffee. In addition, acrylamide concentrations were correlated with the degradation of coffee bean polyphenols and its antioxidant activity. In the process of roasting in a quarter-technological scale apparatus used temperatures ranged from 190 to 216°C. Dry or moist air at a velocity of 0.5 or 1 m s^?1 was used. Beans were roasted to achieve optimal sensory properties. The increase of roasting air velocity regardless of its temperature resulted in the intensification of acrylamide formation. The increase of humidity of roasting air caused a reduction of acrylamide formation, but only at the highest used roasting temperature. However, the modification of roasting conditions to achieve a drop in acrylamide concentration resulted in increased degradation of polyphenols and/or deterioration of antioxidant activity. The optimal roasting parameters were: Temperature 203°C, dry air, and low velocity of roasting air. Under these conditions, the roasted beans were characterized by relatively low level of acrylamide and moderate degradation of polyphenols.