一种新型二肽甜味剂的合成及表征

以3-环己基-L-丙氨酸、Boc-L-天冬氨酸-4-苄酯为原料合成二肽L-天冬氨酰-3-环己基-L-丙氨酸-1-甲酯(Ⅰ),以3-羟基-4-甲氧基苯甲醛为原料经过Witting反应、H2还原和DIBAL-H还原三步反应合成3-羟基-4-甲氧基苯丙醛(Ⅱ),然后Ⅰ与Ⅱ在氢气、Pd/C催化作用下进行还原氨化反应,得到目标产物N-[3-(3-羟基-4-甲氧基苯基)丙基]-α-L-天冬氨酰-3-环己基-L-丙氨酸-1-甲酯(Ⅲ),总产率为47%。产物的结构采用IR、~1HNMR、~(13)CNMR和HRMS进行表征,并验证其甜度约为蔗糖的25000倍。合成终产物的最佳工艺条件为:n(Ⅱ)∶n(Ⅰ)=1∶1,Pd/C催化剂用量为反应物总重的10%,体积分数80%的甲醇水溶液为溶剂,反应温度35℃,反应时间20 h。     

农药多残留分析中QuEchERS方法介绍

主要讨论在农药多残留分析中的一种简便、快速、安全、价格低廉的分析方法——QuEchERS法。该方法的主要步骤是用含1%醋酸的乙腈对样品进行浸提,再加入无水硫酸镁与醋酸钠振荡促使其分层,随后进行分散固相萃取,即将浸提液转移至含有PSA吸附剂、硫酸镁的离心管中,运用Teflon涂层离心管进行离心,取离心液至自动进样瓶用于GC/MS或LC/MS进行测定,并对其稳定性和可靠性进行了分析和评价。同时本方法也可根据可供选择的分析仪器种类、检测限、靶标农药的范围以及使用介质的差异进行适当调整。     

渗透汽化在醇/水分离中的应用

一种新型的膜分离技术即渗透汽化技术逐渐在食品工业中得到应用.该文简要介绍了渗透汽化原理和渗透汽化分离膜,着重论述了渗透汽化技术在食品工业中醇/水分离方面的应用研究.     

Effect of potassic and phosphatic fertilizer type, fertilizer Cd concentration and zinc rate on cadmium uptake by potatoes

In some areas of southern Australia, cadmium (Cd) concentrations in excess of the Australian maximum permitted concentration (0.05 mg kg^–1 fresh weight) have been found in tubers of commercially grown potato (Solanum tuberosum L.) crops. Field experiments were therefore conducted in various regions of Australia to determine if Cd uptake by potatoes could be minimised by changes in either phosphorus (P), potassium (K) or zinc (Zn) fertilizer management.Changing the chemical form in which either P fertilizer (monoammonium phosphate, diammonium phosphate, single superphosphate and reactive rock phosphate) or K fertilizer (potassium chloride and potassium sulfate) were added to crops had little influence on tuber Cd concentrations. Fertilizer Cd concentrations also had little influence on tuber Cd concentrations, suggesting that residual Cd in the soil was a major contributor to Cd uptake by the crops on these soils.Addition of Zn at planting (up to 100 kg Zn ha^–1) significantly reduced tuber Cd concentrations at four of the five sites studied. However, the largest variation was between sites rather than between treatments, with site mean tuber Cd concentrations varying tenfold (from 0.018 to 0.177 mg Cd kg^–1 fresh weight). Factors associated with irrigation water quality at the sites, in particular the chloride concentration, appeared to dominate any effects of changing fertilizer type or Cd concentration.     

酯交换法合成D-异抗坏血酸棕榈酸酯及其抗氧化性能

24℃下,2.9gD 异抗坏血酸和3.8g棕榈酸甲酯分别缓慢加入到14mL的浓硫酸中,搅拌反应24h。反应混合物加入到冰水中,用乙醚萃取,洗涤,除去乙醚,粗产品用甲苯重结晶,得到4.6gD 异抗坏血酸棕榈酸酯,产率79%。用FTIR对产品进行了表征。按国标(GB/T5009.37—1996)方法将产品用于新鲜茶籽油进行抗氧化性能实验,结果表明,D 异抗坏血酸棕榈酸酯是一种比L 抗坏血酸棕榈酸酯更好的油溶性抗氧化剂。     

水解酸化-好氧生物法处理工业废水

水解酸化—好氧生物处理法是近年提出的一种新型处理工业废水的方法。列举了水解酸化工序在生物处理工业废水中的优点，并就其在啤酒废水、屠宰废水、乳品废水、制浆废水以及制药废水中的应用作了介绍。     

高色价栀子黄色素的精制

研究了大孔吸附树脂对栀子黄的精制效果。比较了6种树脂对栀子黄的吸附效果,并选择HPD450树脂精制栀子黄色素。获得高色价、低OD值的栀子黄色素的大孔树脂吸附分离的适宜精制条件为:水提取液ρ(栀子黄)=7 mg/mL,水提取液与树脂的体积比为7∶1,依次用6BV水、4BV体积分数为5%的乙醇、3BV体积分数为20%的乙醇、4BV体积分数为80%的乙醇梯度洗脱。在此条件下,得到OD值为0.394、色价达423.4的精制产品。     

Ultra-high pressure sterilization of powdery food stuff—a new application of a roller compactor

A new non-heating technique was developed for the sterilization of food stuff. Applying a roller compactor, ultra-high pressure sterilization has experimentally demonstrated its ability to sterilize dry powders, such as corn flour and Chinese herbs, with little quality deterioration. Also, the degree of food sterilization was found correlated well with the linear press forces between the rollers, roller gaps, and number of compaction passes. In comparison to the conventional high pressure sterilization technique, the new dry continuous processing method has the advantage of lower investment cost and is more versatile for sterilizing various food powders.     

氢化物发生-原子荧光法测定食品容器等样品中锑含量

本文研究了用氢化物发生-原子荧光法测定食品容器等样品中的锑含量,样品用4%乙酸提取,采用原子荧光光度计进行测定。本文实验利用添加法测定回收率,其平均回收率为97.73%-102. 11%,本方法RSD小于2.0%,最低检出限0.001mg·L~(-1)。