高效液相色谱法测定火锅底料中辣椒素类物质

为了测定火锅底料中的辣味物质(辣椒素及二氢辣椒素),建立了高效液相色谱快速检测方法:色谱柱为C18InertSustain(4.6 mm×250 mm,5μm),流动相为甲醇和水(V/V,65∶35),流速1.0mL/min,柱温30℃,进样量10μL,检测波长280nm。辣椒素类物质的提取采用超声波辅助提取。结果表明:火锅底料中的辣椒素类物质含量在0.256~0.816g/kg之间,斯科维尔系数在3948~12583SHU。     

高效液相色谱法测定豆瓣中辣椒素类物质含量

豆瓣是以蚕豆和辣椒作为主要原料生产的一种调味品,是西南地区尤其是四川地区的一种传统发酵食品。为了测定豆瓣中的辣味物质(辣椒素及二氢辣椒素),建立了高效液相色谱快速检测方法:色谱柱为C18反相色谱柱(250mm×4.6mm,5μm),流动相为甲醇和水(V/V,75∶25),流速1.0mL/min,柱温30℃,进样量20μL,检测波长280nm。辣椒素类物质的提取采用超声波辅助提取。结果表明:豆瓣样品中辣椒素含量在0.0161～0.0624g/kg之间,二氢辣椒素的含量在0.0142～0.0357g/kg之间,斯科维尔指数在519～1671SHU之间。     

高效液相色谱法测定辣椒制品中的辣椒素类物质

该研究采用了高效液相色谱法对辣椒制品中的辣椒素类物质进行检测,并对其提取条件和检测方法进行了研究。以乙醇∶水＝70∶30（V∶V）作为提取液,采用直接萃取法提取样品中的辣椒素和二氢辣椒素,以0.3%磷酸二氢钾溶液-乙腈（62:38,V:V）为流动相,检测波长230 nm,Macherey-Nagel Nucleosil120-5 C18色谱柱（4.6 mm×250 mm, 5 μm）分离。结果表明,辣椒素和二氢辣椒素在20～100 μg/mL质量浓度范围线性关系良好（R12 = 0.999 8,R22 = 0.999 9）,检出限为0.001 g/kg,加标回收率分别为93%～104%和86%～103%,相对标准偏差RSD＜5%。该方法操作简单、快速,具有良好的准确性和精密度,可有效排除香辛料物质的杂峰干扰,适合各类辣椒制品中辣椒素类物质的检测。     

辣椒素类物质辣味的研究进展

辣椒素类物质是一类带有香草基团和中长链脂肪酰胺结构的生物碱,其中辣椒素和二氢辣椒素辣度最高。部分辣椒素类物质可激活相关受体,引起痛觉与热觉神经信号的传导,使人感到辣味。斯科维尔指数法是评价辣度最常见的方法,但评价结果仅与辣味物质的含量有关,无法真正反映样品的辣度,而时间-强度法可获得多个与辣度相关的定量指标,具有更高的参考价值。除增加辣椒素类物质的含量外,使用水基分散系、提高体系温度、增感作用的产生甚至其他感觉刺激均可显著提升辣椒素类物质辣味感知强度,在感官评价中应当特别注意。综上,本文总结辣椒素类物质的结构、分布,辣味呈现机制、评价方法以及影响辣味感知的因素等方面,以期为食品辣味强度预测和辣味食品的开发提供参考。     

超高效液相色谱-串联质谱法测定食用油脂中辣椒素

目的 建立一种超高效液相色谱-串联质谱测定食用油脂中辣椒素的分析方法。方法 试样经正己烷溶解,氢氧化钠水溶液提取,碱性提取液经硫酸酸化后,过PEP-2固相萃取小柱净化,采用超高效液相色谱－串联质谱仪检测,外标法定量。以ACQUITY UPLC BEH C18色谱柱(3.0mm×100mm,1.7μm)为固定相,以0.1%甲酸水溶液和0.1%甲酸乙腈溶液为流动相进行梯度洗脱,串联质谱分析中采用电喷雾离子源正离子模式和多反应监测模式。结果 天然辣椒素、二氢辣椒素、合成辣椒素的质量浓度在0.1μg/L~100μg/L内与其对应的峰面积呈线性关系,检出限(3S/N)合成辣椒素为0.01 μg/kg;天然辣椒素为0.006 μg/kg;二氢辣椒素为0.005 μg/kg。以空白样品为基体进行加标回收试验,回收率在80.3%～96.2%,测定值的相对标准偏差(n=6)为4.5%～5.6%。结论 该方法快速、准确,能满足食用油脂中辣椒素的快速筛查和检测要求。     

LC-MS/MS法测定食用油中的辣椒素和二氢辣椒素

建立了用氨基固相萃取小柱净化提取液,液相色谱串联质谱（LC-MS/MS）法测定食用油中辣椒素和二氢辣椒素含量的检测方法。结果表明,辣椒素在0～100 ng/mL范围内线性关系良好（R2 = 0.998 6）,平均回收率在70.6%～90.5%,相对标准偏差（RSD,n=3）在3.1%～8.9%,检出限为0.03 μg/kg;二氢辣椒素在0～20 ng/mL范围内线性关系良好（R2 = 0.998 8）,平均回收率在71.5%～100.7%,相对标准偏差（RSD,n=3）在6.0%～13.2%,检出限为0.006 μg/kg。该方法简便快速、准确可靠,是鉴别地沟油和测定食用油中辣椒素类物质的有效方法。     

不同灭菌方法对辣椒粉中辣椒素类物质稳定性影响的研究

采用加热、微波、臭氧三种灭菌方式对辣椒粉进行灭菌,以辣椒素类物质含量为特征指标选用响应面法探讨不同灭菌方式对辣椒素类物质稳定性的影响,结果表明:加热灭菌过程中温度对辣椒素类物质稳定性有显著性影响,加热时间对其影响不显著;微波功率及微波时间均都对辣椒素类物质稳定性有显著性影响;臭氧灭菌过程中灭菌时间对辣椒素类物质稳定性有显著性作用,臭氧浓度对辣椒素类物质影响不显著,最佳灭菌条件为:浓度3.16mg/L,灭菌时间24.2min,辣椒素类物质含量达2.59mg/g。     

豆瓣中辣椒素类物质的超声波提取及其热稳定性

对豆瓣中辣椒素类物质的超声波提取条件(提取溶剂、提取温度、提取时间和提取次数)和豆瓣中辣椒素类物质的热稳定性进行研究。结果表明：最佳提取条件为超声波功率200W、超声波频率40kHz、2.5g豆瓣采用10mL甲醇提取两次、提取温度70℃、提取时间5min;热稳定性实验表明,随着加热温度的升高,豆瓣中辣椒素类物质的含量会逐渐下降,当温度达到130℃时,豆瓣中辣椒素类物质的含量开始下降,当温度达到200℃时,辣椒素类物质的含量明显下降。     

基于氧化氮掺杂石墨烯修饰碳糊电极高灵敏测定辣椒素

采用一步水热合成法制备氧化氮掺杂石墨烯(nitrogen-doped graphene oxide,NGO),采用X射线光电子能谱,透射电子显微镜对其进行表征。采用滴涂法制备了氧化氮掺杂石墨烯修饰碳糊电极(nitrogen-doped graphene oxide/carbon paste electrode,NGO/CPE),研究辣椒素在NGO/CPE上的电化学行为,发现与裸碳糊电极相比,NGO/CPE能显著增加辣椒素的响应信号。优化了NGO质量浓度、富集时间、介质p H值等实验参数,利用差分脉冲伏安法对辣椒素进行测定,辣椒素氧化峰电流与其质量浓度在5.0~1 200μg/L范围内呈良好线性关系,检出限为2.0μg/L(RSN=3)。将本方法用于辣椒粉样品中辣椒素含量检测,结果与比色法基本一致。     

EGCG通过激活AMPK、抑制PPARγ调控3T3-L1脂肪细胞中脂滴蓄积

研究表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）对3T3-L1成熟脂肪细胞脂滴蓄积的影响。通过体外诱导分化培养3T3-L1前脂肪细胞,经EGCG处理后,脂肪细胞脂滴大小减小,并表现为时间和浓度依赖性;不会引起成熟脂肪细胞的凋亡。与对照组相比,EGCG处理组显著降低与脂代谢、转运和吸收相关基因的mRNA的表达水平;EGCG处理可以显著降低过氧化物酶体增殖物激活受体（peroxisome proliferators-activated receptor-γ,PPARγ）的表达并激活腺苷一磷酸（adenosine monophosphate,AMP)活化蛋白激酶（AMP-activated protein kinase,AMPK）。使用AMPK抑制剂Dorsomorphin处理成熟脂肪细胞,发现与单独抑制剂组相比,EGCG能提高磷酸化-AMPK的表达水平,并抑制PPARγ的表达。结论：EGCG可能通过激活AMPK从而抑制PPARγ的表达并显著降低与脂代谢、转运和吸收相关基因的mRNA的表达水平,从而减少3T3-L1成熟脂肪细胞的脂滴蓄积。     

不同显色方法测定绿豆壳中黄酮含量的比较研究

采用光谱扫描 ,AlCl3 显色、低浓度AlCl3 显色、Al (NO3 ) 3 显色、低pH值Al(NO3 ) 3 显色的方法分别测定绿豆壳中黄酮物质的特征吸收峰 ,并与芦丁标准物质的特征吸收峰进行比较 ,结果表明采用低浓度AlCl3 显色的方法最适合绿豆壳中黄酮含量的测定。     

十二胺萃取分离制革污泥淋滤液中铁和铬的方法研究

采用十二胺盐(RNH2Cl)为萃取剂,萃取分离制革污泥淋滤液中的Cr3+与Fe3+。结果表明,在pH=2左右,采用10%RNH3Cl-10%正辛醇-正己烷萃取体系,Fe3+的萃取率达到99%,有效地分离了制革污泥淋滤液中的Fe和Cr。并且以1mol·L-1的盐酸作为反萃剂反萃负载有机相,单级反萃率可以达到90%左右。针对试验中产生的两相乳化现象,破乳条件为:80℃、NaCl的浓度15g·L-1,两相在10min即可分层。     

hs-3、ws-3乳酸菌发酵剂冻干研究

通过研究冻干保护剂的冻干厚度、干燥时间与冻干发酵剂含水量的关系,确定hs-3、ws-3乳酸菌冷冻干燥时间为13h,冻干厚度为0.75cm。对不同复合冷冻保护剂进行筛选,确定10%胡萝卜汁 6%葡萄糖 1%琼脂 1%麦芽糊精 1%番茄汁为乳酸菌优良的冷冻复合保护剂。冻干混合菌种发酵剂经发酵活力检测性能优良。     

Contribution of cysteine and glutathione conjugates to the formation of the volatile thiols 3‐mercaptohexan‐1‐ol (3MH) and 3‐mercaptohexyl acetate (3MHA) during fermentation by Saccharomyces cerevisiae

Background and Aims: 3‐Mercaptohexan‐1‐ol (3MH) and its ester 3‐mercaptohexyl acetate (3MHA) are potent aromatic thiols that substantially contribute to varietal wine aroma. During fermentation, non‐volatile 3MH conjugates are converted by yeast to volatile 3MH and 3MHA. Two types of 3MH conjugates have been identified, S‐3‐(hexan‐1‐ol)‐L‐cysteine (Cys‐3MH) and S‐3‐(hexan‐1‐ol)‐glutathione (GSH‐3MH). Yeast‐driven formation of 3MH from these precursors has been previously demonstrated, while the relationship between 3MHA and GSH‐3MH remains to be established. This paper aims to investigate yeast conversion of GSH‐3MH to 3MH and 3MHA, and to assess the relative contribution of each individual conjugate to the 3MH/3MHA pool of finished wines. Methods and Results: Fermentation experiments were carried out in model grape juice containing Cys‐3MH and GSH‐3MH. We found 3MH formation from GSH‐3MH to be significantly less efficient than that of Cys‐3MH. Conversely, esterification of 3MH to 3MHA was higher when 3MH was formed from GSH‐3MH. Additional in vitro assays for measuring enzyme cleavage activity suggest the involvement of a different mechanism in 3MH conversion for the two precursors. Conclusions: These results indicate that although both 3MH conjugates can be converted by yeast, the type of precursor affects the rate of formation of 3MH and 3MHA during fermentation. Significance of the Study: Management of the pool of aromatic thiols during fermentation can depend on relative proportions of different 3MH conjugates.     

Formation of 3-chloropropane-1,2-diol in systems simulating processed foods

Formation of 3-chloropropane-1,2-diol (3-MCPD) from the precursors glycerol, triolein and soy lecithin in the presence of sodium chloride was studied. The precursors were reacted with sodium chloride in an emulsion stabilised with an emulsifier under conditions which modelled the thermal treatment of foods during processing. Three sets of experiments were carried out aimed to monitor the influence of various factors (NaCl, water content and temperature) on the yield of 3-MCPD. The formation of 3-MCPD strongly depended on the concentration of NaCl and reached a maximum level at about 4–7% NaCl. The highest amount of 3-MCPD was formed in media containing approximately 13–17% water. The amount of 3-MCPD increased with increasing temperature over the range 100–230 °C and reached its highest value at 230 °C. The production of 3-MCPD was also followed in models very closely related to selected foods which had been shown to have a high potential to yield 3-MCPD during processing (salami, beefburgers, processed cheese, biscuits, crackers, doughnuts). The highest levels of 3-MCPD were formed in models simulating salami as they had the highest content of both fat and salt of all the samples. The lowest amount of 3-MCPD was formed in the models simulating biscuits and crackers as they had a low salt content and, at the same time, their water content was below the optimum level.     

NaN02-Al(N03)3显色分光光度法测定香椿叶总黄酮的含量

采用NaNO2-Al(NO3)3显色分光光度法测定香椿叶提取液中总黄酮含量,并对测定条件进行研究.结果表明:以芦丁为标样,以NaN02-Al(NO3)3为显色剂,碱性条件下在510 nm处测定显色液的吸光度确定总黄酮的含量,黄酮含量在12.032 mg/L～96.256 mg/L范围内,服从比耳定律,回归方程A=0.011 9C-0.008 4,相关系数R2=0.999 8,方法的回收率为96.33%～101.20%,相对标准偏差(RSD)为1.26%;本方法简便、快速.     

LC-MS/MS法分析尿液中丙烯醛、巴豆醛代谢产物——3-HPMA和3-HMPMA

建立了一种同时检测人尿样中丙烯醛和巴豆醛巯基尿酸类代谢物--N-乙酰基-S-(3-羟基丙基)半胱氨酸(3-HPMA)、N-乙酰基-S-(3-羟基丙基-1-甲基)半胱氨酸(3-HMPMA)的液相色谱-三重四级杆串联质谱(HPLC-MS/MS)方法.该方法以3-HPMA-D、3-HMPMA-D,作内标,采用Isolute ENV+固相萃取柱对样品进行净化,Agilent Extend C<,18>柱分离,多离子监测模式检测3-HPMA和3-HMPMA,并采用该方法测定了8名吸烟者和8名非吸烟者尿样中3-HPMA和3-HMPMA的含量.结果表明:①3-HPMA和3-HMPMA的精密度为2.41%～11.22%,回收率为91.11%～114.66%,检测限分别为1.0和1.3 ng/mL;②8名吸烟者尿样中3-HPMA含量为943.05～6303.54ng/mL,3-HMPMA含量为1061.73～6373.74 ng/mL.8名非吸烟者尿样中3-HPMA含量为14.13～640.93 ng/mL,3-HMPMA含量为23.36～119.40 ng/mL.