HPLC外标法测定亚麻籽油中4种环肽含量的研究

以环肽标准样品定性,采用外标法定量,建立了HPLC测定亚麻籽油中环肽A、环肽C、环肽D和环肽E的方法。采用固相萃取法提取亚麻籽油中的环肽,用Diamonsil C18色谱柱,以乙腈和水为流动相梯度洗脱,柱温35℃,二极管阵列检测器在波长214 nm处进行检测,30 min内完成对4种环肽的分离检测。结果表明:该方法的线性范围为10~160μg/m L,相关系数大于等于0.999 5;环肽A、环肽C、环肽D、环肽E的平均加标回收率分别为94.62%、92.25%、84.07%和100.14%。用该方法测定不同工艺制取的亚麻籽油中环肽的含量,发现未经过精炼的亚麻籽油中环肽含量高于市售亚麻籽油的,其中,冷榨工艺比热榨工艺更能保留亚麻籽油中的环肽。     

高效液相色谱快速分析亚麻籽环肽条件研究

采用高效液相色谱法分析亚麻籽环肽组成及相对含量。以14种亚麻籽环肽色谱峰平均分离度和分析效率作为指标,对不同色谱柱、进样量、梯度洗脱初始体积分数、流速、乙腈体积分数上升速率进行优化,并利用HPLC-ESI-MS进行定性分析。结果表明,高效液相色谱最优条件为:采用Kinetex色谱柱,水、乙腈为流动相,进样量5μL,梯度洗脱程序为乙腈体积分数从40%以5%/min升至90%,流速1 m L/min。最优条件下亚麻籽环肽14个色谱峰分离度较好,平均分离度为1. 65,分析时间为9. 09 min,分离效率为10. 86。优化后的色谱条件可对市售亚麻籽、亚麻籽油以及亚麻籽粕中环肽组成进行有效分析。     

亚麻籽环肽混合物抑制霉菌生长繁殖活性

选取宛氏拟青霉(AS 3.776)和黄曲霉(CICC 2476)作为试验菌株,于121℃高温灭菌前、后添加一定浓度梯度的亚麻籽环肽混合物(flaxseed cyclolinopeptides,FCLPs)到马铃薯葡萄糖琼脂培养基中。FCLPs对宛氏拟青霉孢子形成的半数抑制浓度IC50分别为0.53 mg/m L(高温灭菌)和0.34 mg/m L(未经高温灭菌);对黄曲霉孢子形成的IC50值分别为0.31 mg/m L(高温灭菌)和0.24 mg/m L(未经高温灭菌)。高温灭菌处理后,FCLPs保持了相当的抑菌活性,对宛氏拟青霉的抑制活性最低残留76.8%(菌落生长)和76.7%(孢子形成);对于黄曲霉的抑制活性,最低残留分别为61.6%(菌落生长)和41.7%(孢子形成)。FCLPs对孢子萌发率的平均抑制率为17.8%(宛氏拟青霉)和7.8%(黄曲霉)。采用高效液相色谱法分析霉菌培养后从培养基中提取的FCLPs,发现高温灭菌会降低环肽的含量,这可能是导致环肽抗菌活性下降的原因之一,但环肽中4种主要环肽的比例没有发生明显变化,且没有发现环肽霉菌代谢物产生。综上所述,FCLPs对霉菌具有一定抑制活性,对高温处理较为稳定,能耐食品的热加工,相比现有抗菌肽具有独特优势。     

四种聚合物包装材料对亚麻籽油氧化产物的影响研究

为了探究聚合物包装材料对食用油氧化的影响,以亚麻籽油和不同聚合物包装材料(聚酰胺(PA),聚乙烯(PE),聚对苯二甲酸乙二醇酯(PET)和聚丙烯(PP))为研究对象,探讨在室温和60℃条件下四种聚合物包装材料表面和颗粒对亚麻籽油初级氧化产物及挥发性产物的影响。利用接触角测量仪、傅里叶变换红外光谱仪及气相色谱-质谱联用仪对材料表面特性、亚麻籽油初级氧化产物及挥发性产物进行了测定。结果表明:包装材料亲水性顺序为PET PP PE PA;在不同温度的氧化条件下,材料表面和颗粒对亚麻籽油产生氢过氧化物速率顺序均为PP PA PE≈PET和PA PP≈PE PET;不同聚合物表面对亚麻籽油在室温及60℃条件下产生挥发性物质总量影响顺序分别为PP PET≈PE PA和PP PA PET PE。聚合物的亲水性对亚麻籽油氧化变化有较大影响,且不同温度下对氧化产物的影响具有一定差异性。     

DSC和Rancimat法测定亚麻籽油氧化稳定性研究

采用差示扫描量热仪(DSC)测定压榨亚麻籽油和菜籽油的起始氧化温度,并采用DSC法和油脂氧化稳定性测定仪(Rancimat)法测定两种食用油在不同氧化温度下的诱导氧化时间。实验结果表明:亚麻籽油的起始氧化温度比菜籽油的起始氧化温度低30℃;DSC法和Rancimat法测定的诱导氧化时间均随氧化温度升高而缩短,两种方法在不同氧化温度下的诱导氧化时间有显著的线性相关性;DSC法的诱导氧化时间与氧化温度的相关系数最高,更利于未知温度下诱导氧化时间的推导。在检测方法上,与Rancimat法比较,DSC法用量小,测定时间短,更适于食用油的快速氧化稳定性测定。     

葡萄籽油和亚麻籽油储藏期间氧化对功能性成分影响

通过实验研究35℃恒温避光储藏亚麻籽油和葡萄籽油过氧化值、p–茴香胺值、脂肪酸组成和维生素E含量变化,探讨储藏期间油脂氧化劣变对其功能性成分影响。结果表明,经60天储藏,葡萄籽油、亚麻油过氧化值分别达241.30 mmol/kg、248.72 mmol/kg;p–茴香胺值为32.20、104.06;油脂脂肪酸组成不饱和脂肪酸减少0.35%和0.41%,亚油酸和亚麻酸分别降低0.20%和0.09%、0.23%和1.04%,反式脂肪酸含量基本没有变化;维生素E含量显著降低均未检出;储藏期间亚麻籽油氧化对功能性成分影响均大于葡萄籽油。     

高温条件下亚麻籽油二次氧化产物的动态变化

探讨了亚麻籽油在100～200℃条件下加热1～5 h的过程中过氧化值、酸价、羰基值以及二次氧化产物脂肪族醛类化合物的动态变化。结果表明:亚麻籽油在100℃条件下加热时,过氧化值随加热时间的延长而升高;在120～200℃条件下加热时,过氧化值随加热时间的延长呈现先升高后降低的趋势。酸价和羰基值均随加热温度的升高和加热时间的延长而升高。亚麻籽油高温氧化过程中亚麻酸产生的特征二次氧化产物含量最高,其次是亚油酸,油酸最少。亚麻酸特征二次氧化产物中丙醛最易生成且含量最高,反-2-戊烯醛和反-2-己烯醛产生较晚、较慢,亚油酸特征二次氧化产物中己醛最先生成,反-2-壬烯醛和反,反-2,4-癸二烯醛生成较晚、较慢;油酸特征二次氧化产物中壬醛在120℃加热1 h没有生成,之后其含量随加热温度升高而增加,随加热时间延长先增加后降低。     

亚麻籽脱皮及分离技术研究

研究了影响亚麻籽脱皮与分离的因素及效果。研究表明,140℃的脱皮前烘烤处理,亚麻籽的含水量小于4%,脱皮机转速在2 000~3 000 r/m in时,脱皮率和粉末度比较适宜;静电在6 000~11 000 V,静电吸附面与皮仁混合物在3~5 cm距离时对亚麻籽皮的吸附效果好,皮仁混合物在传输带上铺得越均匀越薄分离效果越好。在最佳分离状态下,亚麻籽的仁皮分离效果可达到皮中含仁率小于1%,仁中含皮率小于3%。     

亚麻籽胶中酸性多糖和中性多糖的分离纯化

采用十六烷基三甲基溴化胺 (CTAB)络合法 ,利用离子交换柱层析和凝胶柱层析从亚麻籽胶中分离得到酸性多糖 (AFM -1 )和中性多糖 (NFM -1 )纯品 ,其分子质量分别为 7 62× 1 0 5u和 1 1 9× 1 0 6u ,总糖含量分别为 5 8 92 %和 84 93%,糖醛酸含量分别为 33 5 5 %和 6 5 8%,AFM-1中C、H和N的含量分别为 2 8 0 4%、5 89%和 0 80 %,红外光谱测定表明 ,AFM -1和NFM -1具有多糖的特征吸收 ,并且其糖环均为吡喃环。     

降胆固醇亚麻籽蛋白酶解肽的分离纯化及结构鉴定

采用Protease M对亚麻籽蛋白进行酶解,制备具有降胆固醇活性的亚麻籽蛋白酶解肽,对其进行分离纯化及结构鉴定,并合成相应多肽验证其降胆固醇活性。结果表明,经Protease M对亚麻籽蛋白酶解4 h时获得的亚麻籽蛋白酶解肽胆固醇胶束溶解度抑制率最高,为47.57%;继续采用超滤技术将其分离为相对分子质量小于等于3 kDa、3~5 kDa、5~10 kDa、10~30 kDa和大于30 kDa 5个组分,发现相对分子质量小于等于3 kDa的组分胆固醇胶束溶解度抑制率最高,为71.0%;再经大孔树脂对该组分进行吸附后经过不同体积分数乙醇溶液洗脱,发现75%的乙醇洗脱分离得到的组分胆固醇胶束溶解度抑制率最高,为79.8%;采用反相高效液相色谱（RP-HPLC）对其进一步分离纯化,收集到F9组分的胆固醇胶束溶解度抑制率最高,为85.7%;最后采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS/MS)从F9组分中鉴定出6种降胆固醇亚麻籽肽,氨基酸序列分别为Ile-Ile-Pro-Ala-Phe(IIPAF)、Leu-Asn-Phe-Phe(LNFF)、Leu-Leu-Gly-Thr-Leu(LLGTL)、Ile-Pro-Pro-Phe(IPPF)、Ile-Ile-Phe(IIF)和Leu-Leu-Gly-Ala(LLGA),其胆固醇胶束溶解度抑制率分别为82.8%、77.8%、88.0%、93.5%、80.3%和87.1%。     

高效液相色谱法测定卤制鸡肝中两种胆固醇氧化物

建立一种可以分析测定鸡肝中7-酮基胆固醇和胆甾烯酮的方法。方法 样品与弗罗里硅土填料混合研磨后装柱,乙腈为洗脱剂,萃取与净化一步完成。无水乙醇为流动相,在240～285nm变波长条件下液相色谱测定。结果 2种胆固醇氧化物在0.25～100μg/ml范围内线性关系良好,r均＞0.9993,方法检出限分别为0.015、0.045μg/g。优化条件下,组分在鸡肝样品中的平均回收率在74.1%～97.0%之间,RSDs＜5.57%。结论 该方法适合于鸡肝中胆固醇氧化物的测定。     

Sterols heating: degradation and formation of their ring-structure polar oxidation products

Cholesterol and phytosterols can be oxidised under heating conditions to give sterol oxidation products (SOPs), known by their toxic effects. This paper studied the degradation of cholesterol and three plant sterols during a 360 min heating treatment (180 °C). The formation and further degradation of SOPs was also analysed by GC-MS. Results revealed a sterol susceptibility to degradation according to the following decreasing order: campesterol≈β-sitosterol≥stigmasterol>cholesterol. The degradation curve fit (R(2)=0.907-0.979) a logarithmic model. SOPs increased their concentration during the first 5-10 min and thereafter, their degradation rate was higher than their formation rate, resulting in a decrease over time. Irrespective of the sterol from which they had derived, 7-keto derivatives presented the highest levels throughout the entire process, and also SOPs with the same type of oxidation followed a similar degradation pattern (R=0.90-0.99).     

热重法对亚麻籽油的氧化动力学研究

本文以亚麻籽油为研究对象,研究了不同升温速率对亚麻籽油DSC曲线和TG曲线的影响,并分别根据DSC曲线和TG曲线对亚麻籽油的氧化进行了动力学求解。研究结果表明,升温速率对亚麻籽油DSC曲线和TG曲线的形状和氧化起始温度均有显著影响,利用TGA技术和DSC技术求解出的亚麻籽油氧化活化能基本一致。      

Black tea thearubigins—their HPLC separation and preparation during in-vitro oxidation

A reverse phase, gradient elution HPLC method has been developed to separate black tea thearubigin compounds. Using diode array spectroscopy, spectral data are provided for the major pigment peaks. The analytical method has been used to monitor the formation of the thearubigin compounds during black tea fermentation. In-vitro model fermentation systems using partially purified tea polyphenol oxidase and mixtures of six pure catechins have also been analysed. Data are presented to relate many of the thearubigins in black tea liquors to their catechin precursors. Manipulation of the in-vitro model system conditions will be used to prepare various thearubigins for further structural studies.     

Clean-up method of forchlorfenuron in agricultural products for HPLC analysis

A simplified method for the determination of forchlorfenuron in agricultural products by HPLC with UV detection was investigated. A chopped sample homogenate from agricultural products was extracted with acetone. The extract was filtrated and concentrated. The residues was loaded onto a Chem Elut column and extracted with ethyl acetate. The crude extract was purified on Oasis HLB and Bond Elut PSA mini-columns using a mixture of methanol and ethyl acetate. Forchlorfenuron was analyzed by HPLC with UV detection (263 nm). HPLC separation was performed on an ODS column with methanol-water as the mobile phase. Recoveries of forchlorfenuron from several agricultural products fortified at the level of 0.1 microg/g were in the range of 87.6-99.5%. The limit of detection (S/N=3) was 0.005 microg/g in the sample.     

Simple analysis of maleic hydrazide in agricultural products by HPLC

A simplified HPLC determination method for maleic hydrazide in agricultural products was developed, and commercial agricultural crops were investigated. The homogenate of agricultural products was extracted with water. The crude extract was purified on an ACCUCAT Bond Elut extraction cartridge using water. Maleic hydrazide was analyzed by HPLC with UV detection (303 nm). The HPLC separation was performed on a ZORBAX SB-Aq column with acetonitrile-water-phosphoric acid(5:95:0.01) as the mobile phase. Recoveries of maleic hydrazide from 15 agricultural products fortified at 1.0 and 10 micrograms/g were in the ranges of 92.6-104.9% and 94.2-101.3%, respectively. The limit of detection was 0.5 microgram/g in samples. The proposed method was applied to the determination of 242 commercial vegetables and fruits. Maleic hydrazide was detected in 2 samples of imported onion at the levels of 4.9 and 7.2 micrograms/g.