共查询到20条相似文献,搜索用时 140 毫秒
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微波具有萃取效率高、加热均匀、节省时间等特点,而恒能量同步荧光法应用于多环芳烃的检测可提高选择性,导数技术又能放大窄带灵敏度,抑制宽带,改善分辨能力。本文结合恒能量同步荧光扫描技术与导数技术,采用家用微波炉,建立了食品中苯并(α)芘(BaP)的微波辅助萃取-二阶导数恒能量同步荧光法。探讨了影响微波萃取效率的主要因素,如萃取溶剂的类型及使用量、微波萃取时间及冷却时间、微波辐射功率等,并与超声萃取做了比较。对低脂肪样品直接用混合溶剂微波萃取即可进行光谱扫描检测食品中的BaP;对高脂肪样品将皂化和微波辅助萃取这两步操作同时进行,简化操作步骤,缩短样品的前处理时间,使样品的整个分析过程可在1h内完成。该方法操作简单、快速、费用低廉,已应用于实际样检测,低脂肪样品的加标回收率为90.0%~105.0%,高脂肪样品的为83.3%~94.6%,方法重现性好,结果令人满意。 相似文献
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分析黔产山香草挥发油的化学成分。采用微波萃取和水蒸气蒸馏两种方法提取山香草挥发油,运用气相色谱-质谱联用技术(GC-MS)对挥发油成分进行分离鉴定,并采用面积归一化法确定各成分的相对百分含量。水蒸气蒸馏法鉴定了39种成分,占挥发油总成分的91.44%;微波萃取法鉴定了55种成分,占挥发油总量的88.77%。实验结果为山香草的开发利用提供了理论依据。 相似文献
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微波辅助萃取-分光光度法测定卫矛中总黄酮 总被引:4,自引:0,他引:4
采用微波辅助萃取法提取,以分光光度法测定卫矛样品中的总黄酮含量。并且通过单因素实验和正交实验设计优化了溶剂浓度、溶剂用量、微波功率和微波辐射时间等微波提取条件,确定了微波辅助萃取法提取卫矛中黄酮类化合物的最佳条件为:使用60%乙醇,在液固比40:1条件下,以255 W的微波功率,微波辐射5 min。在上述最优条件下进行了精密度和回收率实验,所得结果的相对标准偏差为1.71% (n=5),回收率在97%~101%之间。与传统的索氏提取法和超声波提取法比较,微波辅助萃取法具有操作简便,经济可靠,重现性好等特点。该实验采用的微波辅助萃取-分光光度法测定法简便高效,可推广应用于各类中草药中总黄酮的含量测定。 相似文献
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采用微波辅助萃取-水蒸气蒸馏方法提取中药制剂的有效成分,结合紫外分光光度法测定其含量。以提取六味地黄丸中有效成分丹皮酚为试验对象,探讨了微波辅助萃取的实验条件,优化的实验条件是:以乙醇+水(V/V,1∶2)为萃取溶剂,样品与溶剂比1∶50(W/V),微波功率380W,辐射时间2min。结果表明采用微波辅助水蒸气蒸馏对中药制剂进行预处理,可以明显加快丹皮酚的溶出速率,缩短水蒸气蒸馏的时间,将方法应用于牡丹皮及4种中药制剂中丹皮酚的测定,结果满意。 相似文献
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野蔷薇根中总皂苷的提取及其抑菌作用 总被引:1,自引:0,他引:1
探讨超声-微波辅助技术提取野蔷薇根中总皂苷的最佳工艺条件,并分析其抑菌作用。采用单因素试验和正交试验,以皂苷得率为指标,分别考察微波功率、提取时间、乙醇浓度及料液比对总皂苷提取的影响,并采用平板打孔法和试管稀释法测定抗菌活性。超声-微波辅助技术提取野蔷薇根中总皂苷的最佳工艺条件为微波功率100W、乙醇浓度70%、微波时间2min、料液比1:9g/mL。野蔷薇根齐墩果酸对枯草芽孢杆菌、大肠杆菌、金黄色葡萄球菌、变形杆菌和白色黏菌均有强的抑制作用。 相似文献
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Ultrasound (US) and Microwaves (MW) are effective methods for processes intensification. Their combined use in the same reactor can lead to remarkable results. Recently there has been a resurgence of interest in this field for new synthetic applications using reactors based upon existing technologies. We describe here a new type of apparatus in which the thermal energy is continuously removed from the system making possible the use of high power and adjustable ultrasonic and microwave densities throughout the process. The installation consists of a glass reactor located in a monomode applicator which is immersed at the same time in an ultrasonic device which can be operated at different frequencies and powers. A liquid, transparent to microwaves, was used to couple ultrasonic energy to the reactor and to remove the heat generated. Comsol software was used to get information about the distribution of ultrasonic and microwave energy between the reactor liquid and the coupling fluid. The performance was assessed using the conversion of p-nitrophenol into 4-nitrocatechol as a chemical dosimeter and a transesterification. 相似文献
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The effects of microwave, ultrasound and combined ultrasound-microwave (UM) treatment with different intensities on structural and hydrolysis properties of myofibrillar protein (MP) were investigated. Free radical scavenging ability, angiotensin-I-converting enzyme (ACE) inhibitory activity, and cellular antioxidant and anti-inflammatory abilities of the related bioactive peptides were also evaluated. Raman spectroscopic analysis indicated that MP molecule tended to unfold and stretch with increasing in β-turn and random coil content under mild microwave (100 W), ultrasound (100–200 W) and combined UM treatments. Meanwhile, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed these treatments could also improve the thermal stability against heat-induced denaturation and degeneration. The 200 W ultrasound treatment clearly increased MP solubility by disrupting the highly-ordered aggregates into smaller filament and fragment structures. The 300 W ultrasound coupled with 100 W microwave treatment further enhanced these effects. The resulting partially denatured structure induced by suitable ultrasound and combined UM treatments increased the susceptibility of MP to exogenous enzymes, thereby accelerating hydrolytic process and yielding a high peptide concentration in MP hydrolysates. MP peptides could effectively inhibit free radical and ACE activity, which also improved the ability of antioxidant defence system, and suppressed the production of proinflammatory cytokines in RAW 264.7 cells stimulated by H2O2. The combination of 100 W microwave and 300 W ultrasound treatment was optimal method for generating bioactive MP peptides with the strongest multi-activity effects against H2O2-induced cell damage. 相似文献
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The use of non-thermal processing technologies has been on the surge due to ever increasing demand for highest quality convenient foods containing the natural taste & flavor and being free of chemical additives and preservatives. Among the various non-thermal processing methods, ultrasound technology has proven to be very valuable. Ultrasound processing, being used alone or in combination with other processing methods, yields significant positive results on the quality of foods, thus has been considered efficacious. Food processes performed under the action of ultrasound are believed to be affected in part by cavitation phenomenon and mass transfer enhancement. It is considered to be an emerging and promising technology and has been applied efficiently in food processing industry for several processes such as freezing, filtration, drying, separation, emulsion, sterilization, and extraction. Various researches have opined that ultrasound leads to an increase in the performance of the process and improves the quality factors of the food. The present paper will discuss the mechanical, chemical and biochemical effects produced by the propagation of high intensity ultrasonic waves through the medium. This review outlines the current knowledge about application of ultrasound in food technology including processing, preservation and extraction. In addition, the several advantages of ultrasound processing, which when combined with other different technologies (such as microwave, supercritical CO2, high pressure processing, enzymatic extraction, etc.) are being examined. These include an array of effects such as effective mixing, retention of food characteristics, faster energy and mass transfer, reduced thermal and concentration gradients, effective extraction, increased production, and efficient alternative to conventional techniques. Furthermore, the paper presents the necessary theoretical background and details of the technology, technique, and safety precautions about ultrasound. 相似文献
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In this study, microwave pretreatment and grinding treatment were used to enhance sulforaphane formation, then ultrasonic-assisted extraction (UAE) was applied to extract sulforaphane using simultaneous hydrolysis and extraction method. The effects of various parameters, which were ultrasonic time, ultrasonic power, solid-water ratio and solid-ethyl acetate ratio on the extraction rate of sulforaphane were investigated. The results showed that microwave pretreatment enhanced sulforaphane formation. Excessive size reduction did not increase or even reduced extraction rate of sulforaphane. Simultaneous hydrolysis and extraction significantly increased extraction rate of sulforaphane compared to hydrolysis followed by extraction. UAE accelerated mass transfer and the solubilization of the targeted compounds due to the acoustic cavitation effect, thus enhanced enzymatic hydrolysis of glucoraphanin and the extraction rate of sulforaphane. The extraction rate of sulforaphane using UAE with simultaneous hydrolysis and extraction was 4.07-fold of the conventional extraction method. UAE was an effective method to extract sulforaphane from broccoli seeds since it led to higher yield of sulforaphane in a much shorter extraction time. 相似文献
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Microwave and ultrasound have been demonstrated to be outstanding process intensification techniques for transesterification of oil. According to their mechanisms, simultaneous effects can surely bring about better enhancement than sole microwave or ultrasound. Therefore, this study aimed to investigate the important factors and their suitable levels in the KOH-catalyzed transesterification of soybean oil with methanol by using synergistic assistance of microwave-ultrasound (CAMU). The feasibility of application of CAMU in transesterification of oil was demonstrated. When the dosage of methanol, soybean oil and KOH were 15.4 g, 34.7 g (with methanol-to-oil molar ratio of 12:1) and 1 g, respectively, and the microwave power, ultrasonic power, ultrasonic mode, reaction temperature and reaction time were 700 W, 800 W, 1:0, 65 °C and 6 min, respectively, the transesterification reached 98.0% of yield, being the highest yield among all the results obtained; while by using 600 W of microwave plus stirring instead of CAMU, only 57.4% of yield could be obtained. Compared with other reaction techniques, the transesterification by applying novel CAMU was found to have remarkable advantages. Furthermore, by monitoring the variation of real-time temperature and microwave power during transesterification reactions with different microwave operation time and by taking comparison of the corresponding yield, it was demonstrated that the main reason for the acceleration of microwave-assisted transesterification was the polarization and further activation of reactants caused by microwave irradiation, but not the factor of fast heating. 相似文献