Postmortem Changes in ATP, Creatine Phosphate, and Lactate in Sardine Muscle

Postmortem changes were followed in sardines stored in ice. Fast (“white”) muscle creatine phosphate began decreasing from 25 μmol/ g immediately after death. ATP concentration remained about 10 μmol/ g and began decreasing after 2 hr when rigor mortis onset was observed. ATP decreased rapidly when creatine phosphate concentration reached a level similar to ATP, and was 2 μmol/g after 8 hr when full rigor was observed. Lactate accumulation proceeded parallel to ATP degradation (correlation coefficient r = -0.995) and the degree of rigor mortis (r = -0.989). In contrast, sardine slow muscle was low in creatine phosphate (1 μmol/g) and ATP (5 μmol/g), both of which decreased immediately after death. Lactate accumulation was low in this muscle and correlation with rigor mortis progress was lower (r = -0.902) than for fast muscle.     

宰后不同时间蒙寒杂交羔羊霖肉的营养品质分析

研究了宰后不同时间羊肉的营养品质差异,以蒙寒杂交羔羊霖肉为试验材料,对低温条件下(4℃)宰后羊肉7个时间点(1 h、6 h、12 h、1 d、3 d、5 d、7 d)的水分、总脂肪酸、总氨基酸以及矿物质含量进行检测。结果表明,宰后初期(1~6 h)羊肉的水分含量显著高于宰后1 d的羊肉(P<0.05);随着宰后时间的延长,不饱和脂肪酸/饱和脂肪酸比值逐渐降低,宰后1 h的羊肉更接近我国营养协会推荐比值;矿物质质元素的含量(干基)随贮藏时间的延长逐渐降低,其原因可能与部分矿物质元素随滴水损失流失有关;总氨基酸含量没有显著变化。因此,从营养物质的含量角度分析,宰后1~6 h以内羊肉的营养水平(水分、矿物质、脂肪酸)相对较高。     

A Method for the Analysis of ATP Metabolites in Beef Skeletal Muscle by HPLC

A method to determine inosine, hypoxanthine, NAD, AMP, IMP, IDP, ADP, adenylosuccinic acid, ITP and ATP contents in postmortem muscle by HPLC has been developed. The method consists of an homogenization of the muscle in 0.5M HClO₄ or 10% TCA, extraction of the compound with 0.5M tri-n-octylamine/Freon 113 and single injection chromatography on a Whatman Partisil-10/25 SAX column.     

Desmin Degradation in Postmortem Fish Muscle

The degradation of desmin was studied in postmortem white dorsal muscle from sea bass, brown trout, turbot and sardine, stored at 0–4°C. Based on desmin specific antibody tests, results showed that the extent and rate of desmin degradation in postmortem fish muscle varied considerably among species. There was no degradation of desmin during the first 4 days postmortem storage of sea bass and brown trout, whereas 10 to 20% of muscle desmin was degraded during the first 4 days of postmortem storage of turbot. Sardine muscle presented a very complex pattern of desmin degradation products and aggregated desmin fragments detected within the first 24h. Most polypeptides were larger than the nondenatured desmin. Desmin degradation would not be a suitable marker for evaluation of postmortem changes of stored fish.     

宰后贮藏过程中羔羊肉食用品质的变化

研究宰后不同时间羔羊肉食用品质的差异。以羔羊背最长肌为研究对象,测定4℃贮藏条件下,宰后不同时间(1、6、12、24、72、120、168 h)羔羊肉中心温度、菌落总数、pH值、肌节长度、剪切力、肉色、肌红蛋白相对含量和蒸煮损失的变化。结果表明:宰后羔羊肉的pH值从宰后1 h的6.45下降到宰后120 h的5.40左右;宰后1 h和6 h羔羊肉的肌节长度无显著变化(P0.05),宰后12 h最短,宰后24 h后开始变长,而宰后120、168 h变化不显著(P0.05);羔羊肉亮度值(L*)随宰后时间的延长呈上升趋势,红度值(a*)和黄度值则先升高后降低,且氧合肌红蛋白相对含量与a*变化规律一致;羔羊肉剪切力呈现先上升后下降的趋势,在宰后12 h达到最大;宰后1 h羔羊肉的蒸煮损失最低,随后不断增加,168 h时达到最大。综上,宰后6 h前的羔羊肉处于僵直前期,宰后6～24 h时处于僵直期,宰后24～120 h处于解僵期,宰后120 h时解僵过程完成;僵直前和解僵后羔羊肉的食用品质存在差异,僵直前羔羊肉的保水性较高,成熟后羔羊肉的嫩度较高,L*和a*较高。     

A Simple Centrifugal Method for Measuring Expressible Moisture, A Water-Binding Property of Muscle Foods

With the development of more refined methods of measuring water-binding properties of meats, the term “water-holding capacity” needs to be replaced with more specific and carefully defined terms such as expressible moisture, water-binding potential, and free drip. An improved method of measuring expressible moisture is described which is simple and reproducible. It basically measures the amount of liquid squeezed out of a protein system with centrifugal force, by measuring the weight gain of a filter paper surrounding the sample. This method seems to be highly sensitive to factors that affect the water-binding properties of muscle foods.     

Change in Titin Position in Postmortem Bovine Muscle

Myofibrils were prepared from bovine psoas muscles removed from the carcass at 3 and 48 hr postmortem and subsequently stained with a monoclonal antibody against titin. The antibody stained 2 bands per sarcomere (perpendicular to the fiber direction) in myofibrils from 3-hr muscle but often revealed 4 bands per sarcomere in the 48-hr samples. The results suggested that (1) the titin shape might be altered within the first 2 days postmortem, or (2) proteolysis of titin or a protein to which it was attached occurred.     

Postmortem breakdown of ATP and glycogen in ground muscle: A review

The postmorte metabolism of ATP and glycogen in ground bovine muscle (in some cases also in rabbit muscle) was studied. At pH 7 protons released during postmortem glycolysis are bound by the phosphorylation of ADP to ATP and are liberated during enzymic hydrolysis of ATP. At lower pH values the protons are immediately released during glycolysis. Not more than 10% of the total drop in pH postmortem is due to protons liberated by the hydrolysis of ATP present in the tissue at death. Half of the buffering capacity of bovine muscle is caused by the myofibrillar proteins. The myofibrillar ATPases, rather than the membrane ATPases, seem to predominate in hydrolysing ATP postmortem in the intact as well as in the ground muscle. The rate of the breakdown of ATP determines the rate of postmortem glycolysis. Phosphofructokinase and, to a lesser extent, phosphorylase play the major role in the control of glycolytic metabolite levels in ground muscle. The mean values of glycogen recovery, obtained by measuring all glycolytic metabolites and lactate, indicate a general stoichiometric relationship in ground tissue, although several muscles did not fit in the scheme. Grinding of the prerigor muscle causes an accelerated hydrolysis of ATP and ADP, resulting in a faster increase in the IMP concentration and in an accelerated glycolysis. The increase in the turnover of ATP by grinding might be due to a faster release of Ca(++) ions from the damage sarcoplasmic reticulum. Addition of sodium chloride (2-4%) to the ground pregidor muscle causes an increase in the rate of the breakdown of ATP to IMP. NaCl changes the steady-state of glycolysis without a major change in the rate of glycogen breakdown. The stimulation of phosphofructokinase observed is probably due to the faster disapearance of ATP in the presence of NaCl. The faster turnover of ATP could be due to an enhanced release of Ca(++) ions from the sarcoplasmic reticulum by exchange against Na(+) After several hours postmortem an inhibition of glycolysis occurs in the salted tissue which is probably due to a denaturation of glycolytic enzymes by the combined effect of low pH (<6) and high ionic strength. The high water-holding capacity of prerigor salted ground beef does not decrease postmortem in spite of the high rate of ATP breakdown. This effect can be explained by an inhibition of rigor mortis in the fibre fragments caused by the combined effect of ATP, high pH and salt ions. Addition of diphosphate to the prerigor ground tissue in the absence or presence of added NaCl results in an acceleration of ATP and glycogen breakdown. A hypothesis for the high ATP turnover is discussed. The higher rate of glycogen breakdown in the presence of diphosphate is caused mainly by an acceleration of the phosphofructokinase step. A rate limitation, by diphosphate, in the glyceraldehyde-3-phosphate dehydrogenase step and/or the following glycolytic steps was also observed.     

Postmortem Changes in Mule Duck Muscle Marinated in Red Wine

Postmortem changes in duck breast muscle as affected by red wine marination at 5 °C were studied. Myofibrils were purified from the control (CON) and the red wine marinated muscle (RW) after 0, 1, 3, 7, and 14 d storage. The results showed that myofibril fragmentation index (MFI) was significantly (p < 0.05) higher in RW than in CON samples. Myosin heavy chain, α‐actinin, troponin‐T, titin, and nebulin were degraded more rapidly as seen on SDS‐PAGE in RW than in CON samples. Our results suggested that red wine marination can cause postmortem changes in mule duck breast muscle.     

Influence of Postmortem Changes in Bovine Muscle on the Water-Holding Capacity of Beef. Postmortem Storage of Muscle at 20°C

Rigor mortis occurs in bovine neck muscles as soon as pH 5.9 and an ATP level of about 1 μMol/g are reached. At 20°C muscle contraction does not occur before the onset of rigor. Postmortem changes in water-holding capacity (WHC) were followed by measuring the cooking loss of unsalted and salted (2% NaCl) muscle homogenates prepared after storage of the intact muscle tissue at 20°C for different periods postmortem. At tissue pH above 5.9 addition of salt causes a strong increase of WHC of muscle homogenates. There is a small decrease of WHC of both unsalted and salted homogenates during the prerigor phase which is apparently caused by the postmortem fall of pH. Rigor mortis does not influence the WHC of unsalted muscle homogenates but causes a strong decrease of WHC of salted homogenates. The reason for this difference is discussed. No more than one-third of the total postmortem decrease of WHC and protein solubility in salted muscle homogenates was attributed to the fall of pH, so at least two-thirds were due to the development of rigor.     

宰后肌肉蛋白质变化与嫩度的关系

<正>The tenderness of meat is affected by many factors,but the mechanism is still poorly understood. This paper summarized the domestic and foreign researches in recent years on the meat tenderness and analyzed the relationship between meat tenderness and protein degradation,with a view to provide the reference to the study of meat tenderness and quality.     

A Simple Method of Analysis for Tradescantia Anthocyanins

Acylated B-ring substituted anthocyanins with a 4¹-keto structure may be of interest as food colorants because at pH values above 4.0 they show an extra absorption band at 583 nm. This makes the pigments highly colored at pH >4.0. The extra band also provides a simple method of analysis based on the difference between the absorption at 583 nm at pH 5.5 and 2.0. The Delta E 1% 1 cm for the major anthocyanin in Tradescantia pallida was 97.     

一种快速测定透明质酸浓度的分光光度法

阿利新蓝染料和透明质酸形成复合物后，其吸收程度发生了差异，这种变化与透明质酸浓度０～２５７μｇ范围内有良好的线性关系。本法操作简便、快速、重现性好，准确度和回收率分别为２．３％和９６．３％～１０２％。     

一种简易的尿激酶活性测定方法

本研究改良了溶栓酶筛选采用的平板法,建立了一种新的尿激酶活性测定方法。该方法以琼脂糖为载体,纤维蛋白原经凝血酶激活后转变为纤维蛋白形成凝块,再经尿激酶作用使其溶解,形成透明圈,透明圈的面积与尿激酶的活性大小呈正相关。与《药典》中使用的气泡法测定尿激酶活性相比该方法成本低、操作简单、重复性好。     

An Evaluation of Simple Methods for Following Rigor Development in Fish

Measurements obtained with a simple rigorometer (muscle tension measuring device) were found to correlate well with measurements of the relative ATP/IMP content ratio (258/250 nm absorbance ratio of perchloric extracts), muscle pH, and visual measurements of stiffness in whole fish (tilapia, Areochromis aureus) during rigor development. These simple tests yielded measurements which clearly differentiated the effects of ante-mortem stress on the rate of onset of rigor mortis and associated biochemical changes in the fish muscle.     

Influence of Postmortem Changes in Bovine Muscle on the Water-Holding Capacity of Beef. Postmortem Storage of Muscle at Various Temperatures Between 0 and 30°C

Bovine neck muscles were incubated between 0° and 30°C soon after slaughter. At different times postmortem biochemical and physical parameters and cooking loss in homogenates with or without salt were measured. The rate of pH fall in muscle depends on the incubation temperature. At 0.5°C the pH drops fast at first, leveling off afterwards but between 7° and 14°C there is an initial lag period of 2-3 hr. At 30°C no lag phase occurs. The increased rate of postmortem metabolism at 0.5°C is accompanied by cold shortening which occurs before onset of rigor and is followed by little rigor shortening. Above 16°C rigor shortening increases with rising temperature without prerigor contraction. Neither shortening nor development of rigor have an immediate influence of WHC of muscle and unsalted muscle homogenates; the small decrease of WHC postmortem is due to pH fall only and independent of temperature. Salted homogenates prepared from muscles at different time postmortem show above pH 6.0 a similar relationship between pH and WHC. At the onset of rigor mortis (pH 5.9), however, the WHC of the salted homogenate decreases strongly. The practical consequences of these results with regard to processing of beef are discussed.     

巴美肉羊和小尾寒羊肌纤维特性的研究

以五月龄巴美肉羊和小尾寒羊为研究对象,用pH4.6酸性钱孵育液的ATP酶(ATPase)的组织化学染色法分别对背最长肌、股二头肌和臂三头肌进行染色,分析其肌纤维特性。结果显示同一品种不同部位的肌纤维特性存在差异。巴美肉羊的肌纤维密度较小尾寒羊的大,差异极显著(p<0.01),且不同部位的间肌纤维密度差异显著(p<0.05)。品种之间除肌纤维密度以及背最长和股二头中的肌纤维面积存在显著性差异外,其余肌纤维特性差异均不显著。肌纤维特性在肌纤维类型间差异极显著((p<0.01)。     

白酒勾兑的一种便捷计算方法

从白酒勾兑实践出发,以95%vol酒精为基准,建立了一个简捷的基础数据表.在此表基础上推导出了1套便捷的白酒勾兑计算公式和方法.应用于生产实践,查表方便,计算快捷准确.     

一种提取花生种子中总RNA的简易方法

介绍了一种适合花生种子的RNA提取方法。它具有简便、快速等特点,且所提取的RNA样品产率高,质量好,符合分子生物学实验要求。