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1.
Changes in the levels of 21 amino compounds, ammonium-N and urea-N. during the storage of fresh beef at various temperatures have been investigated. The meats were also subjected to bacteriological analysis. Glutathione and glutamine were found to decrease in the meats during storage, while most other amino-acids, notably glutamic acid and tryptophan, increased. The increase in glutamic acid appeared to be related to the microbial numbers in the meats. On the other hand, the increase in tryptophan seemed directly related to the time and temperature of storage. There was an initial increase in urea-N followed by a gradual disappearance of this compound from the stored meats. Ammonium-N did not rise significantly until the stage of incipient spoilage had been reached.  相似文献   

2.
【目的】为明确烟叶游离氨基酸等主要含氮化合物与感官质量的关系。【方法】以烤烟品种云烟87为试验材料,测定不同施氮量和留叶数对初烤烟叶各叶位的烟碱、总氮、蛋白质、20种游离氨基酸含量的影响,通过感官质量评价分析主要含氮化合物与感官质量的关系。【结果】1)不同部位烟叶游离氨基酸总量差异显著,依次为下部叶>上部叶>中部叶;2)简单相关分析表明,总氮、蛋白质、游离氨基酸总量以及非烟碱氮占总氮含量的比例,与感官质量呈极显著的负相关关系;脯氨酸占游离氨基酸总量的比例,与感官质量呈极显著的正相关关系;3)逐步回归分析表明,在烟碱、蛋白质和20种游离氨基酸中,谷氨酸、谷氨酰胺、丙氨酸对感官质量的负面效应大于烟碱、蛋白质以及其它游离氨基酸。4)在8个处理中,施氮量127.5kg/hm2、留叶数14片/株处理的烟叶,非烟碱氮、谷氨酸、谷氨酰胺、丙氨酸含量以及游离氨基酸总量最低,感官质量较好。【结论】控制烟叶非烟碱氮含量,尤其是降低谷氨酸、谷氨酰胺、丙氨酸以及游离氨基酸总量,有利于提高烟叶品质。  相似文献   

3.
The effects of sample size, temperature and duration of storage on the soluble nitrogen and phosphorus content of pig slurry were determined. Almost total conversion of soluble nitrogen to ammonia was observed during storage with considerable losses of dissolved ammonia during filtration procedures under alkaline conditions. Phosphorus was associated mainly with the fine particulate matter of the slurry. The interconversion of insoluble to soluble phosphorus appeared to be an anaerobic process. The rates of production of ammonia and soluble phosphorus were increased at higher temperatures. Changes in small storage samples (< 500 cm3) did not reflect the changes likely to occur under normal farm storage conditions.  相似文献   

4.
The influence of final cooked temperature on the form of iron present and on the concentration of taurine, carnosine, coenzyme Q(10) and creatine was investigated in surface and inner parts of 30-mm thick steaks from beef semitendinosus muscle (n=6). The use of a fast, dry-heat cooking method with a Silex clam cooker (set at 200 °C) led to cooking times ranging from 5.6 to 8.6 min for final internal temperatures of 60 and 85 °C, respectively. The proportion of iron as soluble haem iron decreased from 65% in uncooked meat to 22% when cooked to 60 °C and then decreased more gradually with increases in final cooked temperature. The proportion of insoluble haem iron increased in a reciprocal manner, while changes in the proportions of soluble and insoluble non-haem iron were relatively small, but increases in the percentage of insoluble non-haem iron with increasing final temperature were significant (P<0.01). Changes in the forms of iron with cooking generally took place more rapidly in surface samples than inner samples. On a dry-matter basis, concentrations of taurine, carnosine, coenzyme Q(10), and creatine all decreased with cooking, but the decreases were greatest for taurine and creatine. Losses of creatine were at least partly due to conversion to creatinine, and, along with the other compounds, probably included some loss in cooking juices. It is concluded that despite these changes with cooking, beef semitendinosus muscle remains a good source of iron and a useful source of the potentially bioactive compounds taurine, carnosine, coenzyme Q(10) and creatine.  相似文献   

5.
Summary. Various relationships between the extract-release volume (ERV) and the protein and fat contents of fresh beef are studied in relation to theoretical and other considerations. Inter-relationships between the pH, total volatile nitrogen and the extract-release volume of stored beef samples confirm that the drop in the filtrate volume as spoilage advances is due to changes in the protein. the correlations between the ERV and the pH values take into account the changes which occur in both the 'reverse'prerigor and post-rigor stages.  相似文献   

6.
7.
The effects of cooking and sterilization at several temperatures on the free amino acids (FAA) content in albacore (Thunnus alalunga) muscle were studied during the processing of canned tuna. FAAs were derivatized with o-phthalaldehyde, separated on a C18 column by HPLC and detected by both fluorescence and ultra-violet detectors. After cooking the loss of FAAs was not significant. However, in the final product sterilized at 115 degrees C and 110 degrees C (throughout the whole process) there were significant losses with regard to the start material, but not at 118 degrees C (all temperatures leading to the same lethal F-value). The influence of the thermal process time at 115 degrees C was evaluated for 60 and 100 min. Significant losses were found between both canned products (approximately 25%) and between the raw fish and the final product (approximately 12% and approximately 34%, process time 60 and 100 min, respectively). The determination of the content of FAA present in canned albacore may be a useful indication of the severity of the thermal processing.  相似文献   

8.
The mechanical properties of raw meat under tension were studied to characterise the factors responsible for tenderisation during storage. Extensibility and irreversible lengthening in the direction of muscle fibres was determined continuously from 2 h to 10 days after stunning by cycling the muscle between two applied forces. In post-rigor meat, extensibility increased slightly and the muscle lengthened by 40%. Lengthening occurred earlier at higher post-rigor temperatures and was more sensitive to changes in temperature than the changes in texture of cooked meat. Increasing the maximum applied stress also caused lengthening to occur earlier in post-rigor meat. No lengthening was detected pre-rigor. The relationship between the maximum applied stress and the rate of lengthening showed that lengthening would not have occurred with a stress of 0·07 Ncm(-2) or less. These findings suggest that weakening which occurs during conditioning commenced at rigor and that the component responsible for tenderising was about 30 times weaker than indicated using previous techniques. Histological sections showed regular cracks spaced at about 17 μm apart. This was believed to be indicative of the involvement of extracellular components in the texture of conditioned meat.  相似文献   

9.
Minced beef samples stored in high oxygen modified atmosphere packs (80% O(2):20% CO(2)) were evaluated for colour stability during refrigerated storage. The oxymyoglobin content and surface redness (Hunter 'a' value) of m. biceps femoris samples, previously frozen and minced, were significantly lower in samples with a mean vitamin E (α-tocopherol) content of 2.5 μg g(-1) compared with samples with 3.3, 3.9 or 5.5 μg g(-1) after 4, 6 and 8 days of storage at 4 °C. Lipid oxidation was significantly higher in the beef samples with the low vitamin E content compared with the other groups indicating that a likely mechanism for the colour-stabilising effect of vitamin E is through its action as a lipid antioxidant.  相似文献   

10.
研究鸡肉在常温与冷藏条件下呈味核苷酸及游离氨基酸含量的变化。结果表明:常温条件下,6 h时鸡胸肉和鸡腿肉肌苷酸(IMP)含量达到最高,分别为2.27、1.97 mg/g,然后开始显著下降(p<0.05);宰后随贮藏期延长,测定的17种游离氨基酸含量均有不同程度增加,鸡胸肉和鸡腿肉风味氨基酸占比分别在6 h和12 h时达到最大值,依次为59.3%、61.8%。冷藏条件下,IMP含量随时间延长呈先升后降的规律,鸡胸肉和鸡腿肉分别在48 h和36 h时IMP含量达到最大值,即3.14 mg/g和2.81 mg/g,而后缓慢降低;鸡胸肉和鸡腿肉风味氨基酸占比峰值均出现在宰后低温下48 h时,分别为67.1%、66.4%。因此,低温贮藏可以抑制鸡肉中IMP在贮藏过程中的降解,相对于常温贮藏,冷藏可以促进鸡肉中游离氨基酸的生成,有利于提高鸡肉的食用风味。   相似文献   

11.
Italian ryegrass (Lolium multiflorum) S22, grown in a greenhouse in K-deficient soil in pots, was given 40, 80 and 160 mg of N/kg of soil (as ammonium nitrate) and 0, 60, 120 and 240 mg of K/kg of soil (as potassium chloride). In grass grown without added K, increasing N fertiliser increased the concentrations of total N, non-protein-N, ammonium-N, nitrate-N, free amino acids, amides and amines. With adequate K fertiliser all these N fractions decreased. The percentage distribution of N in the free amino-acid pool varied with the amount of N and K given. Without K fertiliser, increasing N had no consistent effect on most amino acids and amides, although it decreased the percentages of alanine and ethanolamine. Increasing K had relatively little effect on the percentage distribution in grass given the two smaller amounts of N. However, in the grass given the largest amount of N, it increased the percentage of most amino acids, especially alanine and 4-amino-n-butyric acid, and decreased glutamine and asparagine. β-Alanine was found only in K-deficient plants. The effect of K in relation to N metabolism and the nutritive value of herbage is briefly discussed.  相似文献   

12.
Summary The effects of cooking and sterilization at several temperatures on the free amino acids (FAA) content in albacore (Thunnus alalunga) muscle were studied during the processing of canned tuna. FAAs were derivatized witho-phtalaldehyde, separated on a C18 column by HPLC and detected by both fluorescence and ultra-violet detectors. After cooking the loss of FAAs was not significant. However, in the final product sterilized at 115 °C and 110 °C (throughout the whole process) there were significant losses with regard to the start material, but not at 118 °C (all temperatures leading to the same lethal F-value). The influence of the thermal process time at 115 °C was evaluated for 60 and 100 min. Significant losses were found between both canned products (25%) and between the raw fish and the final product (12% and 34%, process time 60 and 100 min, respectively). The determination of the content of FAA present in canned albacore may be a useful indication of the severity of the thermal processing.
Veränderung im Gehalt an freien Aminosäuren in Thunfischmuskel (Tunnus alalunga) während der Wärmebehandlung
Zusammenfassung Die Wirkung des Kochens und Sterilisierens bei verschiedenen Temperaturen auf den Gehalt an freien Aminosäuren (FAA) im Thunfischmuskel (Thunnus alalunga) wurde während der Herstellung von Thunfischkonserven untersucht. Die freien Aminosäuren wurden mito-Phtalaldehyd derivatisiert, auf einer C-18-Kolonne mit HPLC abgetrennt und durch Fluorescenz und UV-Detektoren nachgewiesen. Nach dem Kochen war der Verlust an FAA nicht signifikant, jedoch in dem bei 110° und 115 °C sterilisierten Endprodukt ergaben sich signifikante Verluste bezogen auf das Ausgangsmaterial, aber nicht auf das bei 118 °C erhitzte; alle Erhitzungstemperaturen führen zu demselben letalen F-Wert. Der Zeiteinfluß der Erhitzung bei 115 °C wurde bei 60 und 100 min bewertet. Signifikante Verluste sind bei beiden Dosenkonserven aufgetreten (25%) und zwischen diesen und dem Rohfisch ( 12% und 34%) bei einer Erhitzungszeit von 60 und 100 min). Die Bestimmung des FAA-Gehalts in Thunfischkonserven kann für den Nachweis der Einwandfreiheit des thermischen Prozesses sehr nützlich sein.
  相似文献   

13.
葡萄酒酿造过程中氨基酸含量变化的研究   总被引:2,自引:1,他引:2  
应用HPLC对我国4个产区多个品种葡萄酒酿造过程样品中氨基酸含量变化趋势进行了研究,结果表明,L-脯氨酸是所有葡萄汁中氨基酸的主体,也是各样品含量差异最大的氨基酸;红葡萄酒中含脯氨酸、苏氨酸、赖氨酸等20种氨基酸,其中以脯氨酸含量最高,发现不同葡萄品种之间游离氨基酸种类和含量有差别,这与葡萄品种、气候、发酵工艺有关。  相似文献   

14.
建立了甲醛法测定磷脂中氨基氮的新方法,实验结果表明,此法操作简便、快速,有良好的重现性和精密度。用该法测定浓缩大豆磷脂和酰化磷脂中氨基氮,浓缩磷脂和酰化磷脂浓度分别在10~60g/L和20~100g/L范围内与测定结果呈良好的线性关系,精密度分别为1.24%和1.98%,回收率分别为98.3%和97.8%。  相似文献   

15.
16.
When sorghum is malted much of the nitrogen in the kernel is transferred to the roots and shoots. Examination of Osborne protein fractions extracted from the kernel reveals that as in the case of barley the prolamins are the major source of the nitrogen transferred. Electrophoretic prolamin bands remained unchanged during malting, indicating that prolamins are degraded directly to small peptides and amino acids. There was a general decline in the number of glutelin proteins whereas some albumin plus globulin proteins increased in quantity while others decreased. In the roots and shoots there was a considerable increase in both protein nitrogen and non-protein nitrogen as a result of the translocation of the products of storage protein breakdown from the kernel. Several-fold increases occurred in all of the nine essential amino acids determined. Quantitatively, the two most important free amino acids of sorghum malt appear to be asparagine and glutamine, as in germinated wheat and maize. This is in contrast to barley where proline is the major free amino acid.  相似文献   

17.
18.
Beef, lamb, pork and chicken leg muscles were extracted with distilled water and the soluble iron and zinc compounds separated by gel filtration and dialysis. Iron was distributed between five main components: an insoluble fraction, ferritin, haemoglobin, myoglobin and a low molecular weight fraction. In beef and lamb, myoglobin was the predominant iron compound but in pork and chicken, most of the iron was associated with the insoluble fraction. Whereas more than 70% of beef iron was associated with the haemoproteins, haemoglobin and myoglobin, less than 30% of chicken iron was in this form. Even so, in all meats most of the soluble iron was associated with the haemoproteins. Zinc was present mainly in the insoluble fraction. The soluble zinc was distributed between five main components. Over 70% of soluble zinc was associated with two components having molecular weights of 65 000 and 35 000. The nature and availability of zinc and iron in the various meat fractions is discussed.  相似文献   

19.
本文采用柱前衍生-反相高效液相色谱法(RP-HPLC)对95℃条件下不同煮制时间,不同部位的鸡肉及鸡汤中游离氨基酸(FAA)含量进行测定,研究煮制时间对鸡肉及鸡汤游离氨基酸含量的影响规律。结果表明:95℃煮制不同时间,蛋白质发生不同程度的降解。因FAA形成量与降解量的比率及溶于汤中量的差异,鸡肉表层的FAA含量先升高后降低,在40min时达到最大值;鸡肉中心的FAA含量呈现升高趋势,在120min时达到最大值。鸡汤中的FAA含量因肉样中FAA溶于其中而随煮制延长呈显著升高趋势,煮制120min时的含量约是10min的5倍。因此加热120min内,随煮制时间延长鸡汤会更加鲜美可口,且营养价值高。   相似文献   

20.
黑大麦是一种营养丰富,开发价值较高的谷物,发芽会引起谷物食品中成分的变化。本实验首先研究了黑大麦的发芽工艺条件,在此基础上进一步研究发芽对黑大麦中游离氨基酸、蛋白质、脂肪、淀粉、膳食纤维和维生素B1、维生素B2等常规营养成分含量的影响。结果表明:浸泡8 h后,15 ℃温度条件下发芽48 h,黑大麦的发芽率达到最高(62.14%)。与未发芽黑大麦相比,发芽72 h后,黑大麦中游离氨基酸、蛋白质、淀粉、不可溶性膳食纤维、总膳食纤维、维生素B1、维生素B2及钙、铁和锰等元素的含量均显著升高(p<0.05),而可溶性膳食纤维含量显著降低(p<0.05)。发芽可使黑大麦营养价值得到显著提升。  相似文献   

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