超高压与重组果胶甲酯酶抑制剂联合应用对鲜榨橙汁果胶甲酯酶活性及品质的影响

为了探究超高压与重组果胶甲酯酶抑制剂(recombinant pectin methylesterase inhibitor,rPMEI)联合处理对鲜榨橙汁中果胶甲酯酶(pectin methylesterase,PME)活性及品质的影响,研究了超高压(400、500和600 MPa,5 min,20 ℃)与重组果胶甲酯酶抑制剂对橙汁微生物、PME酶活、色泽和V_C含量的影响。结果表明:超高压处理条件为500 MPa/5 min,rPMEI添加浓度为0.06 mg/mL时,橙汁中的菌落总数、霉菌与酵母菌数均能达到农业行业标准《NY/T 434-2016绿色食品、果蔬汁饮料》所规定的要求,同时PME被完全钝化;橙汁色泽变化显著小于热处理组(ΔE^*=1.22<2.26);V_C保留率为85.1%,显著高于热处理组(保留率=8.33%)。     

果蔬加工中果胶甲基酯酶活性抑制的研究进展

果胶甲基酯酶（pectin methylesterase,PME）是一种广泛存在于高等植物、真菌和细菌的果胶降解酶,其残余活性会导致果蔬汁和鲜切果蔬等产品产生分层沉淀、析水结块、质构软化等品质劣变。因此,在果蔬加工过程中实现对PME活性的有效抑制是加工的重要目的。目前生产中对于PME活性的抑制主要以热加工方式为主,但这会对热敏性果蔬产品品质造成不可逆转的不良影响。随着人们生活水平和健康意识的提高,为了满足人们对更高品质产品的追求,一些新型热加工和非热加工技术以及PME抑制剂逐渐被研究并应用于PME活性的抑制。本文综述当前热、非热加工方式和抑制剂对于PME的抑制效果及其机理,并列举不同加工方式联合处理或加工手段与抑制剂联合处理在PME抑制方面的应用情况,以期为未来更高品质果蔬产品的加工提供理论指导。     

Influence of Enzymatic Clarification with a Pectin Methylesterase on Cider Fermentation

In this study, the effect of two apple juice treatments (clarification with a pectin methylesterase in the presence and absence of sulphiting) on the cidermaking process was investigated. Pre‐fermentative clarification with the pectin methylesterase (Rapidase CPE) slowed the alcoholic fermentation in respect to traditional fermentation, the greatest effect being found for the combination of the enzymatic treatment with sulphur dioxide addition. With this treatment the start of the fermentation was delayed seven days. Enzymatic clarification delayed malolactic fermentation (MLF) and the interaction of both treatments produced a cider in which malolactic fermentation had not occurred. Both treatments ensured that the volatile acid levels during the maturation phase were significantly lower than in the traditional fermentation. Enzymatic clarification led to lower levels of yeasts during the active phase of alcoholic fermentation with respect to the control. When this treatment was combined with sulphiting, a decrease in apiculate yeast numbers during alcoholic fermentation was observed and a better survival of these species was noted after 59 days of fermentation.     

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。     

Mild-Heat and High-Pressure Inactivation of Carrot Pectin Methylesterase: A Kinetic Study

ABSTRACT: Pectin methylesterase (PME) was extracted from carrots and purified by affinity chromatography. The thermal high-pressure inactivation of the PME was investigated in a model system. Under these conditions, the (thermo) stable fraction is not inactivated and the isobaric-isothermal inactivation followed a fractional-conversion model. At lower pressures (< 300 MPa) and higher temperatures (> 50°C), an antagonistic effect of pressure and heat was observed. A 2nd- and 3rd-degree polynomial model (derived from available thermodynamic model) was successfully used to describe the heat pressure dependence of the inactivation rate constants. From the purified carrot PME sample, the thermostable PME fraction was isolated. The thermal inactivation of this fraction followed first-order kinetics.     

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.     

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.     

辐照食品分析检测技术的研究进展

本文介绍了国内外辐照食品检测技术的研究进展，着重对化学分析法、电子自旋共振(ESR)法及热释光分析(TL)法进行了阐述，并对今后辐照食品检测技术的研究提出了建议。     

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.     

Nontargeted Analytical Methods as a Powerful Tool for the Authentication of Spices and Herbs: A Review

Food fraud in herbs and spices is an important topic, which has led to new technologies being studied as potential tools for fraud identification. Nontargeted technologies have proven to be a useful tool for the authentication of herbs and spices. The present review focuses on the use of near‐infrared, hyperspectral imaging, Fourier‐transform infrared, Raman, nuclear magnetic resonance, and electron spin resonance spectroscopy for the authentication of spices, which includes the determination of origin and irradiated spices and the identification of adulterants. The methods developed based on vibrational spectroscopy combined with chemometric techniques seem to be promising tools for determining the presence of adulterants and contaminants in herbs and spices. On the other hand, nuclear magnetic resonance seems to be the most efficient technology to determine the origin of herbs and spices although, for some cases, studies with near‐infrared spectroscopy can be a viable substitute. Electron spin resonance spectroscopy is the technique par excellence used for the authentication of irradiated herbs and spices, so its use should be expanded to many more spices’ varieties. Portable devices are preferred by those involved in the food industry, due to its manageability and low cost. Data fusion and big data are shown as promising tools for spice fraud control. In conclusion, spectroscopic techniques show a great efficiency to authenticate spices, although their evaluation must be expanded to other spice varieties, to new strategies of data analysis (as data fusion and big data), and to the use of portable devices.     

植物多糖分析方法综述

目的：探讨植物多糖的分析方法, 为植物多糖的分析方法学研究提供参考。方法：比较各类多糖分析方法的优缺点。结果：薄层色谱法操作快捷且成本低,多用于多糖的初步研究,HPLC 已成为目前糖类物质分析的最主要方法,HPLC-MS(high performance liquid chromatography -mass spectrometry,液质联用)在多糖分析中有广阔的应用前景。结论：植物多糖的分析方法有较大的改进和发展空间,对其进行深入研究有助于将多糖开发为极具潜力和价值的保健食品和药品。     

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.     

Potential Application of Hot Rehydration Alone or in Combination with Hydrogen Peroxide to Control Pectin Methylesterase Activity and Microbial Load in Cold-stored Intermediate-moisture Sun-dried Figs

ABSTRACT: Sun-dried figs contain a considerable amount of pectin methylesterase (PME) activity (22 JAM COOH/ min/g). The enzyme causes softening and loss of desired gummy texture in cold-stored intermediate-moisture (IM) sun-dried figs brought to a 28% to 29% moisture range. Partial reduction of PME activity (28%) delayed undesirable textural changes in IM figs rehydrated at 80 °C for 16 min. The heat treatment did not cause a considerable reduction in microbial load. However, the addition of 2.5% H2O2 to the rehydration medium at 80 °C reduced the initial total mesophilic aerobic count of figs by at least 90% and turned the figs from a brown color to a desirable and stable yellow-light brown. The in situ fig catalase remains after rehydration at 80 °C. Thus, by reducing the contact period of figs with H2O2 or by pureeing figs, it is possible to eliminate residual H2O2 and to obtain safe and SO2-free light-colored fig products.     

脱氧雪腐镰刀菌烯醇及其衍生物检测方法的研究进展

脱氧雪腐镰刀菌烯醇（deoxynivalenol,DON）属B型单端孢霉烯族毒素,主要由镰刀菌在侵染小麦等禾谷类作物的过程中产生。DON是目前谷物及其制品中污染最为普遍的一种真菌毒素,具有明显的毒性,食用被其污染的饲料和食物会对动物和人类产生急性或慢性毒性作用。因此,为了保护消费者健康并最大限度减少经济损失,迫切需要建立高效、简单、快速的检测技术以实现对DON及其衍生物的有效监测。本文对DON及其衍生物常见的定性定量检测方法进行了系统阐述,并对新兴检测技术的创新点及其潜在应用价值进行了讨论分析,以期为DON及其衍生物检测方法的科学选择提供参考。     

3种脂肪氧合酶酶活测定方法

采用量压法、分光光度法和KI-淀粉法测定了一系列经不同程度热处理的脂肪氧合酶酶活力.分析了3种方法的优缺点和相关性,结果表明相关性良好,其中,量压法具有最广泛的酶液适用性,分光光度法灵敏度最高,KI-淀粉法更适合于工业化应用.     

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.