温度和质量浓度对茶多酚水溶液稳定性的影响

从色差、透光率、吸光度、pH值、电位和儿茶素含量变化探讨质量浓度和温度对茶多酚水溶液稳定性的影响。结果表明：不同质量浓度和温度贮存的茶多酚溶液稳定性差异都较大,其变化趋势主要表现为灭菌、贮存过程中,茶多酚溶液的亮度、透光率逐渐下降,溶液色泽和吸光度逐渐加深和增大,儿茶素含量和pH值呈现显著下降,且茶多酚质量浓度越高变化趋势越明显;25 ℃贮存时,色差、透光率、吸光度、pH值和儿茶素含量的变化程度均明显高于4 ℃贮存时;茶多酚溶液的电位绝对值随着质量浓度的增加逐渐减小,说明质量浓度低的茶多酚溶液较稳定。从变化趋势可判断出茶多酚质量浓度为400～800 mg/L,4 ℃贮存时,茶多酚稳定性相对较好,更适合保存和开发利用茶多酚。     

超滤浓缩乳清蛋白并分离乳糖的研究

采用管式超滤装置,选用切割分子量为20000的聚丙烯腈膜,对乳清进行了超滤浓缩试验。结果表明,降低乳清pH值可提高透液通量,把乳清调整至pH7．0,再离心除去不溶性钙盐,可获得最大透液透量。中性乳清经离心沉降后,在进口压力0.24MPa,温度45℃条件下浓缩180min,平均透液通量达到29．1kg／m2·h,蛋白质含量提高到2.85％,透过液中乳糖浓度变化不大。     

辅色剂对木棉花色苷辅色效果及其稳定性的影响

选用丁二酸、柠檬酸、果糖、甘氨酸作辅色剂。研究木棉花色素溶液在一种辅色剂作用下的辅色及稳定性,并测定其吸光度。结果表明,在pH 3的条件下,柠檬酸、丁二酸使溶液颜色加深,能增加色素的吸光度;果糖和甘氨酸无增色效果,吸光度减少。在0.5% ～5%浓度范围内,色素溶液的吸光度与丁二酸浓度与呈正相关。分别在80℃加热3 h、0.1% ～1%浓度的H_2O_2氧化30 min、自然光照和紫外线辐射7 d的条件下, 5%丁二酸能保持对木棉花色素辅色的稳定性。     

Excel建模用于混合酸性染料组分的分析

选用混合组分为酸性黑MR:酸性蓝5R:分散黑EXSF=70:15:15,对引入分散黑的酸性染料体系进行分析,通过采用分光光度法检测各组分的最大吸收波长、计算吸光度系数及浓度误差,对浓度误差可控性进行了探索。同时用Excel表建立了几只弱酸性染料的"吸光度-浓度"基础数据库,用Excel的矩阵、逆矩阵功能,计算了混合染液中各组分染料的浓度。结果表明,混合染料溶液中有分散染料时,求解误差较大,若直接忽略分散组分浓度所得酸性染料组分结果误差约5%;使用Excel表格及利用其矩阵、逆矩阵命令,可以使得分光光度法分析酸性染料残液组分浓度求解更方便。     

紫外分光光度法测定卵磷脂胶囊中的磷脂酰胆碱

采用紫外分光光度法,在波长207nm处测定卵磷脂在正己烷溶液中的吸光度.结果表明,在0.0102mg/mL～0.0510mg/mL浓度范围内,吸光度与浓度呈良好的线性关系(r=0.9997),加标回收率为99.94%(RSD=0.4),方法具有良好的重现性和稳定性,采用该法对市售的2种卵磷脂保健胶囊中的磷脂酰胆碱含量分别进行了测定.     

火麻仁油总酚含量福林酚测定法的优化

对火麻仁油的多酚提取及福林酚（Folin-Ciocalteu,FC）分光光度法测定总酚含量的条件进行优化,优化后的方法为：吸取0.5 mL 80%乙醇溶液加入到0.25 mL油样中,在室温下（25℃）混匀,以4 000 r/min离心15 min,提取3次后合并上相定容至1.5 mL。以没食子酸为标准品绘制标准曲线,火麻仁油多酚提取液中加入0.1 mol/L福林酚试剂3.5 mL,反应10 min后加入7.5%碳酸钠溶液2.5 mL,暗处反应1 h并于765 nm处测定吸光度。对优化方法以没食子酸为标准品进行评价,结果表明没食子酸浓度在10 μg/mL～80 μg/mL与吸光度的线性关系良好（r2=0.998 6）,该方法测得加标回收率为（104.41±1.98）%,同一样品重复测定6次的相对标准偏差（relative standard deviation,RSD）为2.20%,0～3 h内测定吸光度的RSD为0.92%,重复性和稳定性良好,可作为火麻仁油的酚类油脂伴随物含量的有效的分析测定方法。     

分光光度法测定乳制品中硫氰酸钠的含量

将乳制品样品经三氯乙酸溶液提取,过滤加硝酸酸化,再加入硫酸铁铵溶液,生成硫氰酸铁络合离子,使溶液呈血红色,在最大吸收波长处测定其吸光值,根据吸光度曲线确定硫氰酸钠含量。结果显示:硫氰酸钠浓度为1~30 mg/L、460 nm波长时,吸光度呈良好线性关系,奶粉和牛奶的相对标准偏差分别为3.47%和2.23%,加标回收率为98.6%~99.7%。考虑到显色的稳定性,标准溶液显色后应该在30 min内进行检测。利用分光光度法测定乳制品中的硫酸氢钠,具有操作简便、回收率高、实验成本低、分析周期短、结果准确等优点,适合在广大中小企业推广使用。     

双波长分光光度法染液吸光度在线检测装置

考虑到染液的浑浊性、多组分、外界背景干扰等因素的影响,基于双波长分光光度法原理,采用嵌入式处理器研制了一套染液吸光度检测装置。该装置无需参比溶液,解决了多组分或有背景干扰染液吸光度无法准确测量的问题。用这个装置对3种染液分别进行实验,获取双单色光透过染液的光强,并在线绘制染液的吸光度曲线,从中选取2个最大吸光度并计算其吸光度差,最大程度消除背景干扰等因素的影响。实验发现,该装置测定的染液吸光度误差小,准确度高,为在线染液浓度测量提供了有效途径。     

原料乳及乳粉中糊精掺假的检测方法

研究了原料乳及乳粉中糊精含量的检测方法,样品通过离心除去牛乳中脂肪,在加入沉淀试剂除＋去蛋白、肽和低聚糖等干扰物质,制备澄清透明待测乳清液,加入无水乙醇使糊精结晶形成悬浊液,该悬浊液的吸光度与糊精掺入量有关。通过吸光度换算出糊精质量浓度。结果表明,该方法用于检测原料乳及复原乳中糊精质量浓度在O．025g／100mL以上具有良好的重现性和回收率,同时方法操作简单,结果准确,适用于乳品企业进行原料及产品中糊精质量浓度的检测。     

鹰嘴豆分离蛋白的胶凝性

研究了蛋白质浓度、pH、NaCl及CaCl2对鹰嘴豆分离蛋白胶凝性的影响。pH3.0、无盐加入时,蛋白质分散液以溶液状存在;pH3.0、0.1mol/LNaCl与pH7.0、高离子强度(NaCl:0.5～1.0mol/L)条件下,蛋白质分散液表现出半溶液状性质。pH3.0、高离子强度(NaCl:0.5～1.0mol/L)与pH7.0、低离子强度(NaCl:0～0.1mol/L)条件下,蛋白质分散液以凝胶状存在。pH3.0、NaCl浓度0.5～1.0mol/L与pH7.0、NaCl浓度0～0.1mol/L时具有相似的胶凝动力学。CaCl2对蛋白质的胶凝性影响与NaCl基本相同。pH3.0时,CaCl2的浓度为0.1和0.3mol/L时的凝胶强度分别为24和26.4g;NaCl浓度为0.1、0.5、1.0mol/L时的凝胶强度分别为7.6、8.4和9.3g。     

Thermostable Water Dispersions of Myofibrillar Proteins from Atlantic Mackerel (Scomber scombrus)

A process for preparation of a thermostable, low viscosity water dispersion of myofibrillar proteins from Atlantic mackerel (Scomber scombrus) was developed. The comminuted meat was washed sequentially with cold water, a bicarbonate solution, and cold water. It was then homogenized in ice-cold water. Apparent viscosity of the dispersion depended on protein concentration and temperature. Lowering pH to 3.7 by acetic acid reduced viscosity of the dispersion which remained unchanged irrespective of temperature. The proteins did not precipitate upon heating to 100° followed by centrifugation at 5000 xg for 15 min, even in the presence of 50 mM NaCl solution. However, increasing pH of the acidified solution resulted in precipitation of proteins. Acetic acid also prevented separation of water upon centrifugation of heated dispersion.     

氧化石墨烯紫外吸收适配体传感器对链霉素残留的高灵敏检测

目的：根据核酸适配体对氧化石墨烯（graphene oxide,GO）水溶液聚集的保护作用,建立高灵敏和特异性检测链霉素（streptomycin,STR）残留的适配体传感器。方法：在GO饱和水溶液中,STR核酸适配体可通过疏水键和π-π键作用在GO分子表面从而促进其分散,当STR进入体系后,适配体与STR结合并脱离GO,导致GO分散性降低而聚集,离心后在230?nm波长测定上清液吸光度,建立STR质量浓度的对数lgCSTR与GO吸光度之间的线性关系,进而实现对STR的定量检测。结果：在优化的实验条件下,GO吸光度随着STR质量浓度的增大而降低,且与STR质量浓度的对数在0.002?4～240?ng/mL范围内呈良好的线性关系,线性方程为A=－0.105?73lgCSTR＋0.471 5（R2=0.994）,检出限为0.001?3?ng/mL;同时,对不同来源的蜂蜜实际样品做加标回收率实验,回收率分别为89.3%～108.1%和94.7%～110%。结论：本研究建立的基于氧化石墨烯紫外吸收信号的适配体传感器用于STR残留检测,具有良好重复性和稳定性,可用于STR残留的快速、高灵敏检测。     

Antimicrobial,rheological, and physicochemical properties of sago starch films filled with nanorod-rich zinc oxide

The effects of zinc oxide nanorod incorporation on the flow properties of sago starch solution and antimicrobial, sorption isotherm, water vapor permeability, and UV transmission of sago starch films were investigated. The nanorod-rich ZnO (ZnO-N) was homogenized by sonication and incorporated into sago starch solutions at different concentrations (e.g. 1%, 2%, 3%, and 5% w/w dried starch). Introduction of low concentration ZnO-N to starch solutions significantly increased the viscosity of the solution and significantly decreased the permeability of the films to water vapor by less than one third. Solubility, moisture content, and monolayer water content of the films were decreased, whereas contact angle was increased with higher ZnO-N concentration. ZnO-N starch films had 0% UV transmittance and were able to absorb more than 80% of Near Infrared spectra. ZnO-N sago starch films exhibited excellent antimicrobial activity against Staphylococcus aureus. These properties suggest that ZnO nanorod has the potential as a filler in starch-based films for use as active packaging materials in the pharmaceutical and food industries.     

啤酒酵母中还原型谷胱甘肽清除自由基能力的研究

选用啤酒酵母为原料,采用热水浸提提取还原型谷胱甘肽(GSH),经过高速离心分离、阳离子交换树脂纯化、等电点沉淀及真空浓缩干燥制备还原型谷胱甘肽。采用1,1-二苯基-2-苦肼基(DPPH)自由基反应体系,抗氧化性物质抗坏血酸作为参照物,根据DPPH·体系吸光值的变化研究GSH清除自由基的能力,DPPH·反应体系为5mL0.0817mmol/L DPPH·溶液+5mL样品溶液,反应时间30min。考察了不同浓度GSH和抗坏血酸与DPPH·自由基清除率的关系。结果表明,GSH比抗坏血酸抗氧化能力差一些,但GSH清除DPPH自由基能力与其浓度呈明显的量效关系,因此,啤酒酵母GSH有重要的抗氧化开发价值。     

Boric acid permeation in forward osmosis membrane processes: modeling, experiments, and implications

Forward osmosis (FO) is attracting increasing interest for its potential applications in desalination. In FO, permeation of contaminants from feed solution into draw solution through the semipermeable membrane can take place simultaneously with water diffusion. Understanding the contaminants transport through and rejection by FO membrane has significant technical implications in the way to separate clean water from the diluted draw solution. In this study, a model was developed to predict boron flux in FO operation. A strong agreement between modeling results and experimental data indicates that the model developed in this study can accurately predict the boron transport through FO membranes. Furthermore, the model can guide the fabrication of improved FO membranes with decreased boron permeability and structural parameter to minimize boron flux. Both theoretical model and experimental results demonstrated that when membrane active layer was facing draw solution, boron flux was substantially greater compared to the other membrane orientation due to more severe internal concentration polarization. In this investigation, for the first time, rejection of contaminants was defined in FO processes. This is critical to compare the membrane performance between different membranes and experimental conditions.     

肉桂醛浓度对浓缩乳清蛋白/壳聚糖复合膜性能的影响

为了研究新型高性能抗菌包装材料,本文将肉桂醛添加到浓缩乳清蛋白/壳聚糖复合膜中制成抗菌复合膜,采用FT-IR对复合膜的微观结构进行表征,研究了肉桂醛浓度对复合膜厚度、透光率、机械性能、水蒸气透过系数、氧气透过率等性质的影响,以及其对复合膜抗菌性能的影响。肉桂醛与浓缩乳清蛋白/壳聚糖复合膜有很好的相容性。结果表明:随着肉桂醛浓度的增加,膜的透光率和抗拉强度减小,当肉桂醛浓度为0.3%时,膜的水蒸气透过系数最小,为1.15×10-13 g/(cm·s·Pa),当肉桂醛浓度为0.4%时,膜的厚度和氧气透过率最小,氧气透过率为1.1×10-5 cm3/(m2·d·Pa),当肉桂醛浓度为0.5%时,膜的断裂伸长率最大,为57.5%,膜的抑菌效力随着肉桂醛浓度的增大而显著增大。该研究可为肉桂醛/浓缩乳清蛋白/壳聚糖复合抗菌膜的生产工艺参数的优化提供新的参考。     

Fluorescence inner-filtering correction for determining the humification index of dissolved organic matter

The use of fluorescence spectrometry has been suggested as a simple method to determine the extent of natural organic matter humification by quantifying the red-shifting of fluorescence emission that occurs with increasing humification. Humification indices are calculated by dividing fluorescence intensity at longer wavelengths by intensity at shorter wavelengths. These indices calculated without any specific efforts to standardize dissolved organic matter (DOM) concentration will result in index values thatvary with DOM concentration due to fluorescence innerfiltering effects. This study critically evaluated the effect of DOM concentration on humification index determination using organic matter isolated from field corn extract, soil: water extract, and soil fulvic acid. The results show that humification index values are sensitive to DOM concentration of the solution and are linear with respect to transmittance of the solution at the 254 nm used as the excitation wavelength. An approximate correction for DOM is to exploit the linear nature of the regression fit and to determine index values at the extrapolated 100% transmittance value. An exact correction using explicit correction factors for both primary and secondary innerfiltration effects was shown to give humification index values that are concentration invariant when absorbance of the solution at 254 nm was less than approximately 0.3 unit. Defining the humification index as the fluorescence intensity in the 300-345 nm region divided by the sum of intensity in the 300-345 nm and 435-480 nm regions was statistically advantageous. This study suggests that for quantitative results which can be used to compare humification of natural organic matter across different studies, correction of the fluorescence emission spectra for innerfiltration effects is needed.     

低糖雪莲薯果脯真空渗糖工艺条件的优化

研究低糖雪莲薯果脯的加工工艺条件,对护色、漂烫和硬化等渗糖前预处理过程进行研究,得出最佳条件:用0.4%浓度的柠檬酸溶液对原料护色,沸水漂烫10min,0.5%浓度氯化钙溶液对原料进行硬化2 h.采用真空渗糖的方法对原料糖渍处理,并对真空渗糖温度、渗糖时间、柠檬酸用量和糖液浓度等因素设计正交试验,得出最佳工艺条件:温度35℃、时间120min、柠檬酸0.20%及蔗糖45%.     

柚子皮基香芹酚抗菌膜的制备及性能

为使柚子皮基膜获得抗菌活性,向其中添加香芹酚,通过流延法制备柚子皮基抗菌膜,研究香芹酚质量分 数对膜的颜色、透光率、微观结构、水蒸气透过系数、力学性能和抗菌活性等的影响。结果表明：随着香芹酚质量 分数的增加,柚子皮基抗菌膜的颜色逐渐偏黄;透光率、水蒸气透过系数和抗拉强度降低;而厚度、断裂伸长率和 抗菌活性增加。综合分析结果可知,香芹酚质量分数为1.0%时的柚子皮基抗菌膜具有相对较好的综合性能,此时其 膜厚度为（0.125±0.021）mm、抗拉强度为（12.53±0.72）MPa、断裂伸长率为（16.29±0.60）%、水蒸气透过系 数为（4.06±0.25）×10－12 g·cm/（cm2·s·Pa）、透光率为（49.97±0.38）%、对大肠杆菌和金黄色葡萄球菌的 抑菌圈面积分别达到（377.62±19.63）mm2和（506.82±11.28）mm2。研究结果可为柚子皮基香芹酚抗菌膜的实际 应用提供理论依据。