酶催化法拆分共轭亚油酸异构体

在Candida rugosa脂肪酶的催化下,采用正辛醇与共轭亚油酸(CLA)进行酯化反应,对CLA异构体进行拆分,并通过单因素实验优化酶法酯化的工艺条件.结果表明最优条件为:AY-30脂肪酶加量40.44 U/g,CLA与正辛醇摩尔比1:1,pH 6.5,温度30℃,反应时间12 h.当酯化率为41.92%时,c9,t11-CLA在两种异构体中的相对含量达到88.13%.     

不同香型烤烟化学成分含量的差异

为了解不同香型烤烟化学成分的含量差异,对2008和2009年88个来自我国18个省区不同品种初烤C3F烟叶样品的25种化学成分进行了检测和感官评吸,并对检测数据进行了描述统计、方差分析和主成分分析.结果表明:①浓香型烤烟总植物碱、氯、淀粉、石油醚提取物总量和绿原酸含量显著较高,Mn,Cu,Zn和芸香苷显著较低;中间香型烤烟Fe,新绿原酸和4-O-咖啡奎尼酸的含量显著较低;中间香型和清香型烤烟的总糖和还原糖显著高于浓香型;清香型烤烟叶黄素、β-胡萝卜素和类胡萝卜素含量显著较高;②3种香型烤烟前3个主成分的化学组分主要是含氮化合物、碳水化合物、多酚及质体色素,浓香型烤烟样品的主成分依次为多酚及质体色素、含氮化合物、碳水化合物,中间香型烤烟样品为质体色素及含氮化合物、多酚、碳水化合物,清香型烤烟样品主成分的化学组分类别存在较多的交叉.     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

The recognition of high molecular weight melanoidins as the main components responsible for radical-scavenging capacity of unheated and heat-treated Canadian honeys

As the Maillard reaction is known to occur in heat-treated foods, unheated and heated honey samples were subjected to the activity-guided fractionation and size-exclusion chromatography to compare the degree of browning, radical scavenging activity (ORAC) and molecular size of the fractions obtained. Heat-treatment increased browning in the fractions of light- and medium-coloured honeys (p < 0.002), accelerated the formation of high molecular weight melanoidins (85–232 kDa) and significantly increased ORAC values (p < 0.0001). In contrast, melanoidin content and ORAC decreased in the fractions of heat-treated dark buckwheat honey (p < 0.001). Unheated dark honey contained a significantly higher amount of melanoidins than other honeys (p < 0.007). Together, results showed that at low initial concentration of melanoidins, heat-treatment accelerated formation of new melanoidins and increased ORAC, while at high concentration it caused decrease and a reduction of radical scavenging activity. This study emphasises the importance of non-enzymatic browning in the prediction of the antioxidant pool in thermally processed honeys.     

酪朊酸钠酶解液的分级膜分离的研究

利用截留不同分子质量(10ku、5ku、3ku和1ku)的超滤膜将水解度为11 5 %的酪朊酸钠水解液按分子质量大小分为5级,利用SDS -PAGE研究了酪朊酸钠水解液的分子质量分布及分级膜的分离效果。结果表明,分级膜分离方法对酪朊酸钠水解液中的混和肽类能按照分子量大小进行有效的分离。     

泡沫分离法优化美味牛肝菌多糖分离工艺

采用间歇式泡沫分离法研究美味牛肝菌水提物中的多糖分离工艺条件。结果表明:常温下,每批投料量为200mL时,间歇式泡沫分离美味牛肝菌多糖的最佳工艺条件为pH6、原料液浓度0.640mg/mL、气体流速300mL/min、表面活性剂用量(0.02mg/mL)25mL、浮选时间55min,回收率可达83.1%。结果显示间歇式泡沫分离美味牛肝菌多糖是一种可行、有效的分离方法。     

Quantitative UPLC‐MS/MS analysis of chlorogenic acid derivatives in antioxidant fractionates from dandelion (Taraxacum officinale) root

While qualitative studies have identified chlorogenic acids in antioxidant extracts, particularly ethyl acetate‐derived extracts, of Taraxacum officinale, quantitative analysis of these phenolic compounds remains largely unreported for this species. In this study, bioactivity‐guided fractionation of an antioxidant crude ethyl acetate extract (DPPH = 295.481 ± 0.955 mg TE g^?1 extract) from T. officinale root resulted in a number of reverse‐phase fractions that demonstrated high antioxidant activity (DPPH = 1058.733–1312.136 mg TE g^?1 extract), stronger than that of the synthetic antioxidant Trolox^®. UPLC‐MS/MS screening of these fractions for the presence of selected mono‐ and di‐caffeoylquinic acids revealed large quantities of 1,5‐dicaffeoylquinic acid present in several fractions (853.052–907.324 μg mg^?1), respectively. Due to the antioxidant potency and high levels of 1,5‐dicaffeoylquinic acid observed in these fractions, it was concluded that specifically this chlorogenic acid derivative is a major contributor to the antioxidant efficacy of dandelion root.     

Effect of electrolyzed reduced water on chiral theanine and polyphenols in tea

Pure d/l-theanine enantiomers were synthesized separately, and SEM was used for their crystal-structure observation. The novel enantiomeric separating method by HPLC was established using the chiral selector of β-CD in the mobile phase. Green tea, white tea, oolong tea, black tea and Pu-erh tea were tested for theanine enantiomers by different degrees of fermentation. The significantly higher d-enantiomeric proportion of theanine was found in white tea than the others, which was probably due to its specific processing step of withering. The effect of electrolyzed reduced water (ERW) on enantiomeric theanine and polyphenols in tea was explored. There was no change of theanine, but rather a loss of ECG (epicatechin gallate) and an increasing amount of GA (gallic acid). ERW also reduced tea cream, which contains significant amount of polyphenols, indicating its potential application in the tea-beverage industry.     

响应面法优化泡沫分离桑叶蛋白工艺

利用响应面法对泡沫分离桑叶蛋白的工艺条件进行优化,在单因素试验的基础上,根据Box-Behnken试验设计原理,选取稀释倍数、离子强度、温度和pH值4 个因素,依据回归分析法来确定各工艺条件的影响因素,以桑叶蛋白的回收率和富集比为响应值作响应面和等高线图,得出桑叶蛋白泡沫分离的最佳工艺条件为：稀释40 倍、pH 5.5、离子强度0.18 mol/kg、温度25 ℃。在该工艺条件下,桑叶蛋白的实际回收率为92.50%,富集比为7.63。验证实验结果表明,泡沫分离法能够作为桑叶蛋白粗分离的一种新方法。     

沙蒿籽胶多糖的分级纯化和结构分析

采用0.1mol/L的氢氧化钾对沙蒿籽胶多糖进行组分分级得到水溶多糖(AG1)和水不溶多糖(AG2)。利用离子交换柱层析从AG1中分离得到酸性多糖(AG11)和中性多糖(AG12)。经凝胶过滤色谱检测,AG11和AG12为均一组分。化学组成分析表明,AG1为葡萄糖糖基组成的葡聚糖,并含有糖醛酸;AG11和AG12分别为阿拉伯糖、鼠李糖、木糖、甘露糖、葡萄糖和半乳糖等糖基组成的杂多糖,并含有糖醛酸,相对分子质量分别为8.63×105Da和3.46×105Da。红外光谱测定表明,AG11、AG12和AG2具有多糖的特征吸收,并且其糖环均为吡喃环。