食品中金属元素形态分析技术及其应用

金属元素在食品中的形态分析是当前比较热门的研究领域,本文总结了国内外金属元素形态分析的多种技术,包括化学分析技术、滤膜过滤技术、离子交换树脂技术、电化学分析技术、色谱分析技术、毛细管电泳技术等,特别介绍了它们在食品中金属形态分析中的应用.     

Orange Juices and Concentrates Stabilization by a Proteic Inhibitor of Pectin Methylesterase

A proteic inhibitor of pectin methylesterase (PME), recently discovered in kiwi, was used to stabilize cloud of orange juice concentrate with “Cut-back,” 42° Brix. To concentrated and pasteurized orange juice were added increasing amounts of fresh juice (12° Brix) with PME 0.8 U/mL at the fresh to pasteurized ratios 6.6 to 38%. The PME inhibitor (65% pure), from kiwi, was added at 50 mg/L. After 8 mo at 5°C samples were compared with controls containing the same amount of fresh juice with PME inhibited by pasteurization. Pasteurized samples were not different from those treated with PME inhibitor. Conversely, where PME was not inhibited, cloud stability decreased with increasing amounts of fresh juice. Use of kiwi PME inhibitor in fruit juice production has potential advantages.     

低盐腌渍仔姜果胶甲酯酶保脆工艺的优化

采用果胶甲酯酶对低盐腌渍的仔姜进行保脆处理。采用单因素试验研究葡萄糖酸钙的添加量、果胶甲酯酶的添加量和保脆处理的温度与时间对低盐腌渍仔姜的影响。以硬度为指标,通过正交试验优化低盐腌渍仔姜的保脆工艺。结果表明,低盐腌渍生姜的最佳保脆工艺条件为果胶甲酯酶添加量0.8%,处理温度40℃,处理时间25min,葡萄糖酸钙添加量0.4%。在此条件下,保脆后的低盐腌渍仔姜片的平均硬度为3209.224g。     

Pectin Modifications: A Review

In recent years, the interest in studying modification of pectin has increased. A number of hydroxyl and carboxyl groups distributed along the backbone as well as a certain amount of neutral sugars presented as side chains make pectin capable of preparing a broad spectrum of derivatives. By forming pectin derivatives, their properties may be modified and some other new functional properties may be created. This article attempts to review the information about various methods used for pectin modification, including substitution (alkylation, amidation, quaternization, thiolation, sulfation, oxidation, etc.), chain elongation (cross-linking and grafting) and depolymerization (chemical, physical, and enzymatic degradation). Characteristics and applications of some pectin derivatives are also presented. In addition, the safety and regulatory status of pectin and its derivatives were reviewed.     

木聚糖酶酶活测定方法

介绍和比较了测定木聚糖酶酶活的三种方法,详述了工作曲线法测定木聚糖酶酶活的操作方法及注意事项,并提供了实际应用。     

Inactivation Kinetics of Peach Pulp Pectin Methylesterase as a Function of High Hydrostatic Pressure and Temperature Process Conditions

A kinetic study of the inactivation of endogenous pectin methylesterase (PME) in Greek commercial peach pulp under high hydrostatic pressure (HHP; 100–800 MPa) combined with moderate temperature (30–70 °C) was conducted. Thermal inactivation of the enzyme at ambient pressure conditions was also studied. PME inactivation was modeled by first order kinetics at all conditions tested. High pressure and temperature acted synergistically on PME inactivation, except at the high temperature of 70 °C at the middle pressure range (100–600 MPa), where an antagonistic effect of pressure and temperature was observed. At this specific middle pressure range, an increase of pressure processing led to increased inactivation rate constants of peach PME. A multiparameter model was developed to express the PME inactivation rate constant as a function of temperature and pressure process conditions, taking into account the dependence of both activation energy and activation volume on pressure and temperature, respectively. A good correlation between experimental and predicted values of inactivation rate constants was established. This modeling approach enables the quantitative estimation of the HHP–temperature conditions needed to achieve a targeted PME inactivation in the peach pulp.     

Analytical Methods for Chitosan

SUMMARY

Biopolymer chitosan is a prospective textile auxiliary agent prepared from chitin or from bioprocesses waste. Chitosan has a lot of important characteristicsespecially high sorption of basic ions and biodegradability. In this study we tested chitosan using the following analytical methodsviscosimetry, spectrophotometry (IR, VIS, UV), ninhydrin reaction and sorption methods. We discussed an influence of molecular weight and degree of chemical modification as well.     

Application of Analytical Methods for the Determination of Bioactive Compounds in Some Berries

Fluorometry, ESI-MS, FTIR, and radical scavenging assays were used for characterization of bioactive compounds and the levels of their antioxidant activities. Polyphenols, flavonoids, anthocyanins, and ascorbic acid and the level of antioxidant activity of water extracts of “Murtilla-like” [Myrteola nummularia (Poiret) Berg.], and other widely consumed berries were determined and compared. The contents of bioactive compounds and the levels of antioxidant activities in water extracts differed significantly in the investigated samples (P?<?0.05). “Murtilla-like” extracts contained polyphenols (mg GAE/g)—19.13?±?0.9, flavonoids, (mg CE/g)—3.12?±?0.1, anthocyanins (mg CGE/g)—120.23?±?5.4, and ascorbic acid (mg/g)—2.20?±?0.1; and antioxidant activities (μmolTE/g) by ABTS and CUPRAC assays were 200.55?±?8.7 and CUPRAC 116.76?±?5.7, respectively. Chemometrical processing was done on the basis of kinetic data of two variables (concentration and reaction time) by DPPH scavenging reaction. Polyphenol content highly correlated with antioxidant capacity (R² from 0.96 to 0.83). The quenching properties of berries were studied by the interaction of water polyphenol extracts with a small protein such as BSA by 3-D fluorescence and FTIR spectroscopy. These methods were used as additional tools for the characterization of polyphenols. Wild-grown non-investigated berries were compared with widely consumed ones, using their bioactive composition, antioxidant activities, and antiproliferative and fluorescence properties. In conclusion, the antioxidant properties of “Murtilla-like” can be used as a new source for consumption. The bioactivity of “Murtilla-like” is comparable with blueberries and raspberries. 3-D fluorescence and FTIR spectroscopy can be applied as additional analytical tools for rapid estimation of the quality of food products.

Demethylation of Pectic Substances: Relationship to Methylesterase Activity during Brine Storage of Cherries

Residual pectin methylesterase activity (60% of initial activity) was present in cherry fruit stored 12 mo in brine. The specific activity of pectin methylesterase increased during the first 4 mo (195% of initial specific activity) but remained relatively stable thereafter. Methanol concentration increased (+144.5%) indicating that pectic substances underwent continuous demethylation during 12 mo storage. Pectin deesterification was probably of enzymatic origin since notable chemical deesterification occurred only at a pH lower than that found in fruit during storage. Residual pectin methylesterase activity introduces the possibility of improving fruit texture by manipulating physico-chemical conditions prior to blanching and candying.     

一种测定乙醇脱氢酶活性的循环催化流动分析法

基于乙醇(EtOH)/乙醇脱氢酶(ADH)/氧化型辅酶I(NAD+)催化反应体系,建立了一种用于ADH活性测定的循环催化流动分析法(RCFA),并优选该测定体系的实验条件,得到如下参:Tris-HCl缓冲液浓度(pH 8.9)为0.1 mol/L.EtOH的浓度为15.6 mol/L,NAD+浓度为9.0 mmol/L,ADH用量20 μL/次,反应液流速为0.98 mL/min,反应液体积为2 mL;ADH的测定范围为0.6～50 U/L,检出限为0.14 U/L,相对标准偏差≤1.3%(n=11).RCFA法具有测定过程简便、快速、自动化特点,能对ADH催化反应过程进行连续循环检测,可对ADH活性变化实现动态研究.RCFA法使反应液循环不但节省了大量的试剂和酶量、降低了测定成本,而且循环测定时不存在人为误差,提高了测定结果的准确度.     

淀粉酶活性常量与微量测定方法比较

以实验室保存的淀粉酶产生菌枯草芽孢杆菌为出发菌株,经过平板分离、点种、碘熏蒸,筛选出产淀粉酶活力较高的菌株。本实验重点采用常量测定法和微量测定法对酶活性进行测定,并对所得数据进行比较分析,结果显示,两种方法测定的酶活性差异不明显,说明微量测定法是可以代替常量测定法的。     

多肽类药物分析方法的研究进展

对近年多肽类药物的各种分析方法,包括生物检定法、免疫分析法、同位素标记示踪法、色谱、质谱、核磁共振、色谱光谱联用技术等的研究进展作一综述.     

多肽类药物分析方法的研究进展

对近年多肽类药物的各种分析方法,包括生物检定法、免疫分析法、同位素标记示踪法、色谱、质谱、核磁共振、色谱光谱联用技术等的研究进展作一综述。     

烟草特有亚硝胺分析方法研究进展

综述了近年来烟草及卷烟烟气中烟草特有亚硝胺(TSNAs)分析方法研究进展,认为尽管这方面的研究已取得了许多重要成就,但由于烟草和烟草烟气分析中基体背景十分复杂,所以研究建立分析速度快、定量准确、重现性好、分析成本低的TSNAs分析新方法在当前仍然是十分必要的。     

食盐中钙含量测定方法综述

文章综述了近30a来测定食盐中钙元素的各种方法,探讨了测定食盐中钙元素的发展之路.目前常用的方法是火焰原子吸收光谱法,还有容量法、比浊法、分光光度法、石墨炉无火焰原子吸收法、鳌合树脂分离富集法、电感耦合等离子体发射光谱法等,并分别介绍了其优、缺点.     

A Review of Current Methods for the Determination of Acrylamide in Food Products

Acrylamide (AA) is a potentially carcinogenic substance which is formed during heating of food products containing carbohydrates and asparagine. It was first detected in food products in 2002. Since that time, several analytical methods have been made available for the quantification of AA in various foods. Starting from the announcement in 2002, occurrence, formation, chemistry, toxicology, and potential health risk in the human diet have been investigated and methods of analysis have been reviewed in many articles. In this paper, current information and analytical methods for the determination of AA have been reviewed.     

反式脂肪酸分析方法的研究进展

本文综述了反式脂肪酸的来源、结构和分析方法。详细介绍了红外光谱法、气相色谱法、银离子高效液相色谱法在反式脂肪酸研究中的应用，并对各种分析方法的优缺点进行了比较。     

乙醇的测定方法综述

乙醇是一种重要的化工原料,其测定方法很多,主要有物理方法和化学方法,介绍了乙醇的测定方法和各种方法的适用范围。     

Analytical Methods for Virus Detection in Water and Food

Potential ways to address the issues that relate to the techniques for analyzing food and environmental samples for the presence of enteric viruses are discussed. It is not the authors?? remit to produce or recommend standard or reference methods but to address specific issues in the analytical procedures. Foods of primary importance are bivalve molluscs, particularly, oysters, clams, and mussels; salad crops such as lettuce, green onions and other greens; and soft fruits such as raspberries and strawberries. All types of water, not only drinking water but also recreational water (fresh, marine, and swimming pool), river water (irrigation water), raw and treated sewage are potential vehicles for virus transmission. Well over 100 different enteric viruses could be food or water contaminants; however, with few exceptions, most well-characterized foodborne or waterborne viral outbreaks are restricted to hepatitis A virus (HAV) and calicivirus, essentially norovirus (NoV). Target viruses for analytical methods include, in addition to NoV and HAV, hepatitis E virus (HEV), enteroviruses (e.g., poliovirus), adenovirus, rotavirus, astrovirus, and any other relevant virus likely to be transmitted by food or water. A survey of the currently available methods for detection of viruses in food and environmental matrices was conducted, gathering information on protocols for extraction of viruses from various matrices and on the various specific detection techniques for each virus type.