分光光度法测定大蒜提取物中硫代亚磺酸酯含量

硫代亚磺酸酯是大蒜中的活性成分 ,由大蒜中非蛋白质氨基酸———蒜氨酸 (alliin)经内源酶蒜氨酸酶 (alliinase ,蒜氨酸裂合酶 ,EC4·4·1·4 )的酶解作用而生成的。介绍了一种利用L -半光氨酸和DTNB检测新鲜大蒜及大蒜提取物中硫代亚磺酸酯的分光光度法。此方法具有简便 ,快速和灵敏度高的特点。     

大蒜中硫代亚磺酸酯提取工艺及其稳定性研究

采用乙醇溶液提取大蒜中的硫代亚磺酸酯,研究了乙醇浓度、提取温度、提取时间、料液比对硫代亚磺酸酯提取量的影响,在单因素实验的基础上采用响应面法确定了最佳提取条件:乙醇浓度为64.89%,提取温度为19.06℃,提取时间为1.48 h,料液比为1∶4.48(g∶mL),硫代亚磺酸酯含量可达4.17 mmol/100 g。对硫代亚磺酸酯的稳定性研究表明:随着温度的升高,硫代亚磺酸酯稳定性下降,提取液在贮存过程中,随着硫代亚磺酸酯含量的降低,二烯丙基二硫醚(DADS)与二烯丙基三硫醚(DATS)的含量会上升。     

Improving fresh and processed garlic by irradiation under different storage conditions

Hungarian garlic bulbs were irradiated with gamma rays (0.15 kGy) and stored at 20, 4 and ?20 °C for 8 months. At the end of storage period, marketable value of bulbs increased especially with those kept under low temperatures, whereas the storage at room temperature (20 °C) produced high losses in bulbs due to infestation and/or infection in unirradiated but less in irradiated samples. Gas chromatographic analysis of volatile oils revealed the presence of 18 compounds. Diallyl disulphide and diallyl trisulphide compounds were cleary identified. Irradiation induced reduction in the percentages of these compounds especially for the first one. Cold or freezing treatment preserved the volatile sulphur contents on garlic cloves at their maximum value. Also, subsequently drying of irradiated cloves resulted in better quality than those unirradiated before drying process. It is concluded that irradiation as an alternative preservation method is useful in the improvement of storeability of fresh or dried garlic bulbs during long storage period.     

大蒜在模拟加工及人体环境条件下杀菌作用研究

文章研究了大蒜在模拟人体内环境(消化环境)和体外加工处理条件下对病原细菌的抗菌活性。方法:滤纸片法。结果表明大蒜在经过模拟人体或加工条件的处理之后,其榨汁对金黄色葡萄球菌、苏云金芽孢杆菌、变形杆菌、大肠杆菌、枯草杆菌与痢疾杆菌等都有比较明显的抑菌效果。     

高产纳豆激酶的枯草芽孢杆菌优选及发酵工艺条件优化

以黄豆为主料,添加不同辅料,采用不同处理方式,以产酶活力为指标研究三株枯草芽孢杆菌发酵性能,筛选优势菌株进行固态发酵,确定最优工艺条件。结果表明:在三株受试菌种中BS21076发酵性能最优,活菌数及纳豆激酶活力均较高;最优固态发酵条件为:大豆90℃下烘炒5min,破碎度为四瓣,魔芋精粉添加量3%,接种量为8%,37℃下发酵24h;在此条件下,酶活力可达(3582.48±83.13)U/g,较传统发酵NK活力极显著(p<0.01)提高。      

高产纳豆激酶的枯草芽孢杆菌优选及发酵工艺条件优化

以黄豆为主料,添加不同辅料,采用不同处理方式,以产酶活力为指标研究三株枯草芽孢杆菌发酵性能,筛选优势菌株进行固态发酵,确定最优工艺条件。结果表明:在三株受试菌种中BS21076发酵性能最优,活菌数及纳豆激酶活力均较高;最优固态发酵条件为:大豆90℃下烘炒5min,破碎度为四瓣,魔芋精粉添加量3%,接种量为8%,37℃下发酵24h;在此条件下,酶活力可达(3582.48±83.13)U/g,较传统发酵NK活力极显著(p0.01)提高。     

Changes in thermoluminescence properties of minerals separated from irradiated potatoes and garlic during long-term storage under different light conditions

The effect of different light conditions on the specificity and reliability of thermoluminescence (TL) analysis to detect irradiated samples (potatoes and garlic) during 2?years of storage was investigated. The silicate minerals separated from the nonirradiated samples provided a low-intensity TL glow curve with a maximum peak after 300?°C demonstrating the absence of an irradiation history. The TL glow curve from the irradiated samples provided easy discrimination with TL glow curves of high intensity and maximum peak in temperatures range of 160?C185?°C. The results were also confirmed by calculating the TL ratio (TL₁/TL₂) through normalization (re-irradiation) step. The key parameters of the TL analysis including the TL intensity, TL glow curve shape, and the TL ratio exhibited a time-dependent change. The bleaching effect of different light conditions was also significant, which was most prominent in the case of natural light with a prominent decrease in the TL intensity and ratio. The maximum TL glow peak also showed a shift towards the higher temperature. However, all irradiated samples, irrespective of the storage conditions and time, were easily discernable from the nonirradiated ones considering the shape and intensity of the TL glow curve.     

Antioxidant and antimicrobial activities of fresh garlic and aged garlic by-products extracted with different solvents

Food Science and Biotechnology - This study aims to investigate antioxidative and antibacterial properties of fresh garlic (non-aged, NG) and aged garlic (AG) by-products extracted with distilled...     

保存时间及温度对藠头不同部位中硫代亚磺酸酯含量的影响

用分光光度法检测藠头各部位硫代亚磺酸酯的含量,并研究保存时间及温度对藠头各部位中硫代亚磺酸酯保留的影响。结果表明,藠头各部位均含有较高的硫代亚磺酸酯,但在粉碎之后含量随时间增长迅速降低,并未见明显的储存温度对硫代亚磺酸酯保留量的影响。     

大蒜总黄酮的超声波辅助提取及其抗氧化活性

以大蒜为原料,在单因素试验的基础上通过正交试验设计优化了大蒜总黄酮的超声波辅助提取工艺条件,并研究了大蒜总黄酮的体外抗氧化活性。结果表明:乙醇体积分数对大蒜总黄酮提取率具有显著性影响,大蒜总黄酮的超声辅助提取最佳工艺条件为,乙醇体积分数60%,超声温度60℃,超声时间60 min,料液比1∶30(g∶mL),在此工艺条件下总黄酮提取率为4.213%。抗氧化活性结果表明:大蒜总黄酮对羟自由基(·OH)和超氧阴离子自由基(O2-·)均具有一定的清除能力,在相同浓度下,大蒜总黄酮对·OH的清除效果强于Vc,对O2-·的清除效果略低于Vc。     

Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

 The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test. Received: 27 May 1998 / Revised version: 15 July 1998     

Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

 The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test.     

Physicochemical and sensory characteristics of whey protein hydrolysates generated at different total solids levels

Whey protein hydrolysates were generated at different total solids (TS) levels (50-300 g/l) using the commercially available proteolytic preparation Debitrase HYW20, while enzyme to substrate ratio, pH and temperature were maintained constant. Hydrolysis proceeded at a faster rate at lower TS reaching a degree of hydrolysis (DH) of 16.6% at 300 g TS/l, compared with a DH of 22.7% at 50 g TS/l after 6 h hydrolysis. The slower breakdown of intact whey proteins at high TS was quantified by gel-permeation HPLC. Reversed-phase (RP) HPLC of hydrolysate samples of equivalent DH (approximately 15%) generated at different TS levels indicated that certain hydrophobic peptide peaks were present at higher levels in hydrolysates generated at low TS. Sensory evaluation showed that hydrolysates with equivalent DH values were significantly (P < 0.0005) less bitter when generated at 300 g TS/l (mean bitterness score = 25.4%) than hydrolysates generated at 50 g TS/l (mean bitterness score = 39.9%). A specific hydrophobic peptide peak present at higher concentrations in hydrolysates generated at low TS was isolated and identified as beta-lactoglobulin f(43-57), a fragment having the physical and chemical characteristics of a bitter peptide.     

不同浸泡条件对薄膜包装材料总迁移量检测结果的影响

薄膜普遍用作食品直接接触包装材料。薄膜包装材料在使用过程中要与食品直接接触较长时间。如果生产的薄膜材料所用原材料不合格,生产工艺不合理,薄膜材料中的某些化学成份就可能会很快渗透或溶入到食品中,尤其在遇到高温、高油、醋等物质可直接转移到食品中,造成食品的化学性污染^[1]。我国食品卫生法明确规定,对食品包装材料必须进行卫生检测^［2］。总迁移量是国家标准中检测食品包装材料卫生标准分析方法中的重要指标,指的是从食品接触材料及制品中迁移到与之接触的食品模拟物中的所有非挥发性物质的总量^[3]。本文以本公司使用的左旋肉碱胶薄膜包装材料不同浸泡方法与浸泡条件的总迁移量进行探讨。     

Cyanobacteria hepatotoxins,microcystins: bioavailability in contaminated mussels exposed to different environmental conditions

Mussels such as Mytilus galloprovincialis accumulate cyanotoxins without being affected by them. Microcystins (MCs), being the most common and studied cyanotoxins, covalently bind to protein phosphatases but this bond may be affected by environmental conditions. In this work, we studied the effect of different environmental and cooking conditions on the bioavailability of MCs in contaminated mussels. Conservation of contaminated mussels at room temperature (20 °C) led to a significant reduction of detectable MCs in the mussels. The conservation in the fridge (4 °C) produced a significant difference with a decrease on the detectable MC after 24, 48 and 72 h of exposure. The effects of the cooking on the MCs availability showed that boiling does not significantly change the MCs content of the mussels. Nevertheless, the microwave treatment significantly reduced the MCs content in both time periods used (1 and 5 min). Our work shows that the bioavailability of MCs in contaminated mussels may be changed due to conservation or cooking conditions.     

预冷条件及采摘熟度对草莓品质影响的研究

研究了3种不同成熟度的草莓经不同预冷条件(温度和时间)处理后,室温放置,草莓品质的变化情况。结果显示:经预冷处理后,草莓硬度提高,口感、外观品质也得到明显改善;未熟果预冷处理后Brix值比对照区低,成熟果预冷处理后Brix值比对照区高。     

Quantitative variation of total and individual high molecular weight glutenin subunits of wheat in relation to variation in environmental conditions

The total amount of the high molecular weight glutenin (HMWg) subunits, and the amount of the individual subunits, present in kernels of wheat (Triticum aestivum L) were studied in relation to differences in growing conditions. The amounts of individual HMWg subunits in four varieties, each grown at six sites in The Netherlands, differed considerably between the sites. Only to a limited extent (0-66%, depending on variety) could this variation be ascribed to differences in protein content of the samples. The cause of the rest of the variation is unknown. Accordingly, the total amount of the HMWg subunits, relative to the total amount of proteins present in a wholemeal flour of a variety, differs between the samples produced at different sites. Thus the preference for synthesis of a certain protein fraction may vary depending on the environment. A second experiment showed that variation in protein contents of samples of two varieties grown on the same trial field accounted for about 90% of the variation in the total amount of HMWg subunits. The samples of each variety differed in protein content as a result of differences in the amount of N fertiliser applied. Within each variety, the ratio between the individual HMWg subunits was less dependent on variations in environmental conditions than on the actual amount, indicating that the levels of expression of the individual HMWg subunit genes are regulated by a common mechanism. The implications of the results for the selection possibilities of wheat with desired bread-making quality and for studies concerning genetic Variation in the amount of HMWg subunits are discussed.     

Volatile distribution in garlic (Allium sativum L.) by solid phase microextraction (SPME) with different processing conditions

Treatments of autoclaving, high temperature aging (aged-black garlic), crushing, and roasting at 100, 150, and 200°C were applied to alter the volatile profiles of garlic (Allium sativum L.). Headspace volatiles in samples were analyzed by a solid phase microextraction (SPME)-GC/MS. Total peak areas of crushed-raw garlic were the highest and those of aged-black garlic clove were the lowest. Crushing effects were clearly observed in raw garlic, aged-black garlic, and roasted garlic at 200°C for 60 min. Sulfur-containing volatiles including diallyl disulfide and diallyl trisulfide were major volatiles. Generally, peak areas of diallyl disulfide decreased when garlic received autoclaving and roasting treatment while diallyl trisulfide and allyl methyl trisulfide increased during heat treatment compared to raw garlic. Roasting at 200°C for 60 min caused the formation of pyrazines greatly in garlic. Principal component analysis (PCA) for the volatile profiles by SPME-GC/MS could discriminate types of processed garlic successfully.