本文選題：乳酸脫氫酶　切入點(diǎn)：MetMbR活性　出處：《甘肅農(nóng)業(yè)大學(xué)》2017年碩士論文

【摘要】：肉色是消費(fèi)者判斷肉新鮮程度和貨架期的重要指標(biāo),冷卻肉表面的褐變被消費(fèi)者認(rèn)為是品質(zhì)劣變的表征。本實(shí)驗(yàn)以有氧儲(chǔ)藏條件下的冷卻牛肉為試驗(yàn)材料,探究了宰后冷藏過(guò)程中影響肉色穩(wěn)定性的主要生化因子變化規(guī)律以及LDH活力與MRA活性表達(dá)的相關(guān)性,從穩(wěn)定肌紅蛋白氧化還原形式的生化機(jī)制入手,明確了乳酸脫氫酶和高鐵肌紅蛋白還原與肉色穩(wěn)定性的關(guān)系,并結(jié)合體外孵化揭示乳酸脫氫酶在冷卻牛肉肉色穩(wěn)定及高鐵肌紅蛋白還原作用機(jī)理。結(jié)果如下:1.宰后冷藏期間三組冷卻肉肉色L*和b*值都呈現(xiàn)出先增大后減小的變化趨勢(shì),在1~3 d內(nèi)無(wú)明顯變化。抑制組L*值和b*值相對(duì)初始值降低了2.26%和6.79%,而對(duì)照組和激活組L*值分別升高了3.47%和4.46%(P0.05),b*值分別降低了2.89%和0.74%。對(duì)照組、抑制組和激活組a*值在冷藏過(guò)程中相對(duì)初始值降低了17.5%、25.23%和2.35%(P0.05)。2.冷藏初期冷卻肉中肌紅蛋白主要以O(shè)Mb的形式存在(約占56%),成熟7d后OMb降低至10.93%,MMb則升高至68.90%(P0.05),另外,肉的冷藏期間LDH活性、NADH的濃度、MetMbR的活力也顯著下降,相比于初始狀態(tài)降幅分別為45.96%27.81%和84.64%(P0.05),導(dǎo)致MMb大量積累。3.草氨酸鈉抑制劑處理過(guò)的肌肉中LDH活性、NADH濃度顯著降低(P0.05),而甜菜堿處理肌肉后LDH活性,NADH濃度及顯著升高(P0.05),肉色更穩(wěn)定。說(shuō)明草氨酸鈉在肌肉組織中能夠有效的抑制乳酸脫氫酶的活性從而導(dǎo)致NADH濃度及MetMbR活性降低,影響MetMb還原因而降低肉色的穩(wěn)定性,甜菜堿作用與之相反。4.SDS-PAGE電泳圖譜(乳酸脫氫酶同工酶)分析發(fā)現(xiàn),對(duì)照組的LDH1同種型表達(dá)顯著高于處理組1,顯著低于處理組2(P0.01),表明草氨酸鈉在肌肉組織中能夠有效抑制LDH-B活性,阻礙了LDH1蛋白表達(dá),降低了NADH的生成速率。從而導(dǎo)致MetMbR活性降低,影響MetMb還原因而降低肉色的穩(wěn)定性,甜菜堿作用與之相反。5.乳酸-LDH-NAD~+體系在缺乏牛肌肉提取物(LDH)、NAD~+或乳酸鹽的反應(yīng)混合物中,高鐵肌紅蛋白還原酶活力不明顯。將L-乳酸鹽為替換D-乳酸鹽或者增加草酸酸鈉到混合物中導(dǎo)致沒(méi)有高鐵肌紅蛋白還原,增加混合物中牛肌肉提取物的量、NAD~+或乳酸鹽濃度、適當(dāng)提高乳酸鹽 NAD~+ 肌肉提取物(LDH)系統(tǒng)的pH和反應(yīng)溫都會(huì)明顯提高高鐵肌紅蛋白還原力(P0.05)。用乳酸鉀代替混合物中的乳酸鈉時(shí)高鐵肌紅蛋白還原力沒(méi)有差異(P0.05)。離體實(shí)驗(yàn)驗(yàn)證了乳酸脫氫酶參與MetMb還原,同時(shí)是L-乳酸鹽和NAD~+的相互作用。
[Abstract]:Meat color is an important index for consumers to judge the freshness and shelf life of meat. The browning of cooled meat surface is regarded by consumers as a sign of poor quality. The changes of main biochemical factors affecting the stability of meat color during postmortem refrigeration and the correlation between the activity of LDH and the expression of MRA activity were investigated. The biochemical mechanism of stabilizing the redox form of myoglobin was discussed. The relationship between the reduction of lactate dehydrogenase and high iron myoglobin and the stability of meat color was clarified. Combined with in vitro incubation, lactate dehydrogenase was found to be stable in the color of chilled beef and the mechanism of the reduction of high iron myoglobin. The results were as follows: 1. During the period of postmortem refrigeration, the values of L* and b* of the three groups of chilled meat showed a tendency of increasing first and then decreasing. The values of L * and B * decreased by 2.26% and 6.79%, while those of control group and activation group increased by 3.47% and 4.46%, respectively, and decreased by 2.89% and 0.74%, respectively. The relative initial values of inhibition group and activation group decreased by 17.525% and 2.35% respectively during cold storage. The myoglobin in the chilled meat was mainly in the form of OMb (about 56.5%). After 7 days of maturity, OMb decreased to 10.93% and increased to 68.90%, P0.05%. The activity of LDH activity nadh and MetMbR also decreased significantly during cold storage of meat. Compared with the initial state, the decreases were 45.96% and 84.64%, respectively, which resulted in a large accumulation of MMb in the muscle treated with sodium oxalate inhibitor. The concentration of LDH activity and nadh in the muscle treated with sodium oxalate inhibitor decreased significantly, while the concentration of nadh in muscle treated with betaine significantly increased the concentration of P0.05. The results show that sodium oxalate can effectively inhibit the activity of lactate dehydrogenase in muscle tissue, resulting in the decrease of NADH concentration and MetMbR activity. The effect of betaine on the stability of meat color was found by SDS-PAGE electrophoresis (lactate dehydrogenase isozyme) analysis. The expression of LDH1 isotype in the control group was significantly higher than that in the treatment group 1 and significantly lower than that in the treatment group 2 (P 0.01), which indicated that sodium oxalate could effectively inhibit the activity of LDH-B in muscle tissue, hinder the expression of LDH1 protein, and decrease the rate of NADH production, which resulted in the decrease of MetMbR activity. The effect of betaine on the stability of meat color was also affected by the effect of betaine. 5. Lactic acid-LDH-NAD ~ system was used in the reaction mixture of lack of bovine muscle extract (MetMb) or lactate. The activity of ferric myoglobin reductase was not obvious. When L- lactate was substituted for D- lactate or sodium oxalate was added to the mixture, there was no reduction of ferric myoglobin, and the amount of bovine muscle extract in the mixture was increased, and the concentration of NAD- or lactate in the mixture was increased. When the pH and reaction temperature of the lactate NAD ~ + muscle extract (LDH) system were properly increased, the reductive capacity of ferric myoglobin was significantly increased (P0.05). There was no difference in the reductive capacity of ferric myoglobin with potassium lactate instead of sodium lactate in the mixture (P0.05N). The results showed that lactate dehydrogenase was involved in MetMb reduction. It is also the interaction of L-lactate and NAD ~.
【學(xué)位授予單位】：甘肅農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TS251.52

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