钙蛋白酶系统对肉的嫩化作用研究进展

肉的嫩度是肉品质的一个重要指标,严重影响肉的食用价值和经济价值.钙蛋白酶系统通过水解肌原纤维蛋白,在宰后肌肉嫩化中起着决定性的作用.综述钙蛋白酶系统(包含钙蛋白酶、钙蛋白酶抑制蛋白和钙蛋白酶激活蛋白3部分)对肉嫩化的作用机制和研究现状,并探讨研究前景.     

钙蛋白酶的活性调节及其与肉嫩度的关系

钙蛋白酶(calpain)是与肉嫩度相关的重要内源性蛋白酶之一,广泛存在于细胞质中,且需要一定量的Ca2 激活。研究表明,钙蛋白酶在Ca2 的激活下能降解肌原纤维蛋白,从而改善肉品嫩度。但是,由于钙蛋白酶抑制蛋白(calpastatin)等因素对钙蛋白酶活性的抑制作用,钙蛋白酶的活性调节成为一系列高度可调的复杂过程。在综述钙蛋白酶结构与功能关系的基础上,进一步阐述了钙蛋白酶的活性调节如何影响肉品嫩度。     

白羽肉鸡胸腿肉的氧化对食用品质和钙蛋白酶活性的影响

为了研究氧化对禽类肌肉的影响程度,为鸡肉品质调控的研究提供参考,本实验以白羽肉鸡为研究对象,选取鸡的胸、腿肉,测定氧化对肌肉持水性能、营养素含量以及对胸肉钙蛋白酶活力的影响。结果显示：氧化可造成肉鸡胸肉和腿肉持水力下降,蒸煮损失率增加,产品得率降低;且过氧化氢（H2O2）溶液浓度对蛋白氧化程度和脂肪氧化程度有影响,随着H2O2溶液浓度的增大,肌肉蛋白质和脂质等营养素水平呈显著下降趋势。而在氧化对钙蛋白酶的活性研究中发现钙蛋白酶活力随H2O2浓度增大而降低,从而推测钙蛋白酶活力水平变化与白羽肉鸡肉质改变的关系密切。     

内源性蛋白酶在宰后猪肉成熟过程中的作用

本文分别阐述了两类内源性蛋白酶,即钙蛋白酶和溶酶体组织蛋白酶的结构、性质、影响酶活性的因素及其在猪肉成熟过程中的作用,认为在猪肉宰后成熟过程中,钙蛋白酶发挥的作用更显著。     

钙蛋白酶系统及其对肉嫩度的影响

钙蛋白酶系统作为影响肉嫩度的重要因素引起了科研人员的广泛关注。钙蛋白酶系统是高度可调的复杂系统，包括钙激活酶、钙激活酶抑制蛋白和钙激活酶激活蛋白，三者相互作用，共同调控宰后肉的嫩化。本文综述了钙蛋白酶系统的结构及功能，并在此基础上阐述了其影响肉嫩度的作用机理。     

钙蛋白酶和肉的成熟嫩化

对钙蛋白酶(Calpain)及其与肉的成熟嫩化的关系作一概述，认为在肉的成熟嫩化过程中。钙蛋白酶和溶解体组织蛋白酶起着巨大的作用，而钙蛋白酶的作用更为显著。     

钙离子对钙激活蛋白酶mRNA表达、活性及其对肌肉蛋白降解的影响

本实验分别以牛肉肌束和分化为肌细胞的L6成肌细胞为研究对象,研究钙离子对离体肌束中钙激活蛋白酶活性、蛋白分解以及活体肌肉(肌细胞)中钙激活蛋白酶mRNA水平表达的影响。结果表明500μmol/L以内的钙离子处理肌束,可以提高肌束中μ-钙激活蛋白酶的活性,当高于此浓度时,μ-钙激活蛋白酶因发生自动降解而失活。但是钙离子对m-钙激活蛋白酶活性影响不大,只有钙离子浓度达到10mmol/L时才会导致自动降解而失活。钙离子可以加速肌肉中蛋白质的降解,且浓度越高,降解越明显;钙离子处理活体肌细胞,在没有产生明显细胞死亡的情况下,可导致μ-钙激活蛋白酶和m-钙激活蛋白酶mRNA水平表达的增加。由本研究的结果初步推断钙离子不仅可以激活钙激活蛋白酶的酶活性,提高分解肌肉蛋白的能力,在刚刚屠宰的肉(肌肉未死亡)中进行钙离子嫩化也可以导致钙激活蛋白酶表达量的增加。     

梅山猪与三元杂交猪肉宰后成熟过程品质变化比较

目的：比较梅山猪与三元杂交猪的肉品质以及影响两个猪种持水力的因素,为梅山猪肉质性状的选择提供一定的参考。方法：选取6 头梅山猪和6 头三元杂交猪,在宰后45 min取胴体左侧背最长肌,采用低场核磁共振技术测定肌肉中水分分布情况以及酪蛋白酶原分析法测定钙蛋白酶的活性,在成熟过程中的1、3、7 d测定肌肉的持水力。结果：梅山猪肉色的L*值和a*值与三元杂交猪差异显著（P＜0.05）。梅山猪宰后成熟1、3 d的贮藏损失率和宰后1 d的蒸煮损失率显著低于三元杂交猪（P＜0.05）,说明梅山猪肉具有较高的保水性。梅山猪宰后45 min的pH值显著高于三元杂交猪（P＜0.05）。低场核磁共振T2弛豫测定结果表明,梅山猪肉中结合水含量显著高于三元杂交猪,自由水含量显著低于三元杂交猪（P＜0.05）。肌肉水分分布的差异在一定程度上解释了两种猪肉的持水力的变化。梅山猪与三元杂交猪肉中的钙蛋白酶活性在成熟第1天差异显著（P＜0.05）,成熟第3天和第7天差异不显著。结论：钙蛋白酶活性对这两个猪种的保水性影响不大,肌肉的水分分布及宰后45 min、pH值的差异解释了梅山猪具有较高的保水性。     

钙激活蛋白酶在肉成熟中的作用机理

与肉成熟有关的内源蛋白酶之一的钙激活蛋白酶类(Calpains),对该酶类的组成成分、存在位置、含量测定、提纯方法、活性测定、不同部位分布特点、宰后含量变化及自我水解的特点进行了详细说明,以了解对探索肉的成熟机理具有重要意义的钙激活蛋白酶类的作用机理。本文引用Titin、Nebulin、Dystzophin、Desmin、Troponin-T等等蛋白的宰后变化分析以说明钙激活蛋白酶促进肉成熟的作用机理。最后指出该酶研究疑问和研究意义。     

鱼肉内源性蛋白酶对其贮藏期品质影响的研究进展

鱼肉贮藏期间会发生一系列物理和化学性质的改变，进而引起鱼肉品质劣变。鱼肉品质劣变的影响因素众多，内源性蛋白酶在这一过程中发挥重要作用。本文重点围绕与贮藏期鱼肉品质下降相关的基质金属蛋白酶、钙蛋白酶和组织蛋白酶三种内源性蛋白酶展开介绍，梳理这三种酶对鱼肉蛋白作用的理论基础，并对其在鱼肉的风味、保水性、颜色及质地等品质变化中的作用机理加以阐述，以表征内源性蛋白酶在鱼肉品质劣变中的作用。同时论述了现今鱼肉内源蛋白酶抑制的几种技术方法，旨在为鱼肉及其制品的品质检测及控制技术开发提供一定参考。     

Changes in smoking prevalence in Ukraine in 2001-5

Objectives

To analyse trends in smoking prevalence in Ukraine from three surveys conducted in 2001–5, and to explore correlates of observed changes, in order to estimate the stage of tobacco epidemic in Ukraine.

Design

Repeated national interview surveys in Ukraine in 2001, 2002 and 2005.

Main outcome measure

Prevalence of current smoking among the population aged ⩾15 years.

Results

The age‐standardised prevalence of current smoking in Ukrainian men was 54.8% in 2001 and 66.8% in 2005. Among Ukrainian women, prevalence increased from 11.5% in 2001 to 20.0% in 2005. ORs for yearly increase in prevalence were estimated as 1.164 (95% CI 1.111 to 1.220) for men and 1.187 (1.124 to 1.253) for women, which implies that, on average, 3–4% of men and 1.5–2% of women living in Ukraine join the smoking population each year.

Conclusions

In Ukraine, smoking prevalence is increasing in most population groups. Among men, the medium deprivation group with secondary education has the highest smoking prevalence. Among women, while the most educated, young and those living in larger cities are the leading group for tobacco use, other groups are also increasing their tobacco use. Tobacco promotion efforts appear to have been significantly more effective in Ukraine than smoking control efforts. The decrease in real cigarette prices in Ukraine in 2001–5 could be the main factor explaining the recent growth in smoking prevalence.Ukraine is a large eastern European country with high smoking prevalence. Tobacco products are widely available at very low prices, and the transnational tobacco industry is extremely successful in promoting its products and lobbying for its interests in the legislative field. Advocacy of tobacco control has only recently achieved some success in the legislative field, with the first tobacco control law being adopted in late 2005. Ukraine ratified the Framework Convention on Tobacco Control in 2006, but there is still much cause for concern regarding the enforcement and effectiveness of the adopted legislative measures. Unfortunately, the government is not yet involved in nationwide surveillance of the tobacco problem, and the available data have mostly been gathered with funding from foreign donors. Several attempts have been made to measure the extent of the tobacco epidemic in the countries of the former Soviet Union (FSU).^{1,2,3,4,5,6,7} Most of these studies have shown rather high smoking prevalence among men (50–70%) and comparatively low prevalence among women (5–20%). Most countries in the FSU have similar smoking rates, while certain trends are shown to be related to the differences in how the transnational tobacco industry succeeds in every national tobacco market.⁶ Unfortunately, few studies have been published showing trends in smoking prevalence in the FSU.⁷ In Ukraine, two studies^3,4 provided point estimates of smoking prevalence.The aim of this study was to analyse trends in smoking prevalence in Ukraine, on the basis of three surveys conducted in 2001–5, and to explore correlates of observed changes in order to estimate the stage of the tobacco epidemic in Ukraine.     

2010年河南省部分食品中重金属污染状况分析

了解河南省部分食品中重金属污染的现状。方法 在河南省18个省辖市采集8大类3 657份食品样品,按照国家标准检测食品中铅、镉和汞的含量,检测结果按照GB 2762—2012《食品安全国家标准食品中污染物限量》进行评价。结果 河南省部分食品中铅含量的平均值为0.34 mg/kg,总体超标率为8.8%(320/3 656),其中粮食、肉类和蔬菜中超标率较高,分别为17.2%(95/552)、14.5%(85/587)和10.7%(57/534);部分食品中镉含量的平均值为0.054 mg/kg,总体超标率为3.9%(143/3 657),其中食用菌和蛋类中超标率较高,分别为9.6%(49/508)和8.1%(42/518);部分食品中汞含量的平均值为0.077 mg/kg,总体超标率为8.3%(303/3 657),其中蔬菜和粮食中超标率较高,分别为25.3%(135/534)和12.3%(68/551)。结论 河南省部分食品中铅、汞污染情况较为严重,其中粮食、蔬菜和肉类食品中污染情况尤为突出,需要加强监管。     

Content of selenium in fishes,caught in lakes in Buriatia

Study of selenium accumulation by fish of Buryatia shows relatively high accumulation level for the Baikal lake (213-513 mcg/kg) contrary to the lakes of Baunt and Selenginsk regions of the republic (84-227 mcg/kg). Selenium deficiency in Baunt region is also confirmed by low selenium levels in meat of native origin (39-95 mcg/kg). Among different tissues and organs the lowest selenium levels are typical for muscles, the value increasing in the row: muscle < skin < air bladder < scales < fin < liver < roe.     

Moulds and mycotoxins in sorghum stored in traditional containers in India

Various traditional containers have been used in India for storage of sorghum grains. Sorghum is susceptible to fungal infestation and toxin elaboration. The present study relates to the mould and mycotoxin contamination (aflatoxin B₁ and T-2 toxin) in stored sorghum in different storage containers viz. “Kotlu” (Storage rooms), earthenware pots, gunny bags and reed baskets. Aspergillus sp. and Fusarium sp. were the prominent genera and the “Kotlu” form of storage was most susceptible to fungal attack. Storage treatment had little effect on fungal contamination, but despite the fungal infestation, the mycotoxin contamination was found to be very low.     

中国固态发酵白酒中功能细菌研究进展

细菌是白酒酿造3大类微生物之一,其在白酒生产中有着重要的作用,如:芽孢杆菌、乳酸菌、放线菌和梭菌等,它们能产生酯类、有机酸、吡嗪、萜烯等微量成分,从而影响白酒的风味与品质。基于细菌在白酒中的重要功能以及微生物分离培养技术和分析检测技术的进步,近年来相关研究越来越深入。该文综述了近年来白酒功能细菌的研究进展,介绍了酿酒各个环节中主要功能细菌及其在白酒中的作用,旨在为白酒功能细菌的研究提供参考。