高效液相色谱法测定肌酸粉中一水肌酸、肌酸酐和双氰胺含量

目的 建立一种同时检测肌酸粉中一水肌酸,肌酸酐和双氰胺含量的检测方法。方法 样品用水溶解稀释至一定溶度,过滤膜即得样品供试液。采用高效液相色谱法测定,10 mmol/L磷酸二氢钠溶液(氨水调PH至10.5)作为流动相,检测波长为220nm,流速0.8ml/min,外标法定量。结果 本方法在10 min内完成3种目标化合物的分离分析。试样中一水肌酸浓度在0.204~1.02 mg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度一水肌酸标准品添加下,一水肌酸的回收率为97.9%。试样中肌酸酐浓度在0.530~6.36μg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度肌酸酐标准品添加下,肌酸酐的回收率为99.0%。试样中双氰胺浓度在0.0531~0.637μg/mL的范围内与峰面积的线性关系良好, 相关系数r＞0.999。在3水平不同浓度双氰胺标准品添加下, 双氰胺的回收率为106.1%。结论 该方法快速、准确、灵敏, 适合同时测定肌酸粉中一水肌酸,肌酸酐和双氰胺含量。     

Contents of creatine, creatinine and carnosine in porcine muscles of different metabolic types

Creatine, creatinine and carnosine have been analyzed by hydrophilic interaction chromatography (HILIC) in seven different pork muscles of different metabolic type (Semimembranosus, Biceps femoris, Gluteus maximus, Longissimus dorsi, Gluteus medius, Trapezius and Masseter). As reported in previous literature, carnosine contents are related with the type of metabolism, being higher in those muscles with glycolytic metabolism. Creatine and creatinine also showed significantly higher concentrations in glycolytic muscles such as Semimembranosus, Biceps femoris, Gluteus maximus and Longissimus dorsi. Masseter, a red oxidative muscle, was characterized by the lowest contents of creatine, creatinine and carnosine and, finally, Gluteus medius and Trapezius, both intermediate muscles, had also intermediate contents of these studied compounds. Finally, a correlation between initial content of creatine and creatinine formation after cooking has been verified using pure standards and two different metabolic type muscles, Longissimus dorsi and Masseter, obtaining slightly higher creatinine amounts in Longissimus dorsi, probably due to its higher initial creatine content and its lower pH.     

Urinary creatinine and creatine excretion in pigs in relation to body weight and nitrogen balance

In experiments with growing pigs highly significant correlations between body weight and urinary creatinine (r=0.98) or creatine (r=0.95) excretion, were found. Furthermore, creatine made up of 20-25% total urinary creatinine + creatine excretion. Creatinine excreted (expressed as mg kg^?1 body weight) was significantly (P< 0.001) higher in heavier pigs (approx. 75 kg) compared to pigs at 25 kg and urinary creatinine as a percentage of total urinary N-excretion was significantly (P< 0.001) lower for pigs of 25 kg than for pigs of 53 and 75 kg, respectively. There was a significant positive correlation (P< 0.001) between N-balance and creatine excretion in 25 kg pigs whereas the opposite was the case for 75 kg pigs.     

Creatinine,creatine and protein in cooked meat products

The accuracy of the results obtained with a flow injection (FI) system for the simultaneous determination of creatinine and creatine in cooked meat products was evaluated in 30 samples by comparison with those obtained by reference methods. The FI method was then applied to 52 different samples (cooked ham, 14; frankfurters, 11; wieners, 9; chopped, 10; mortadella, 8) and the protein content was also determined. From % creatinine of total creatine (creatine + 1.159 creatinine) an estimation of the heat treatment applied in the processing was made. Cooked ham, mortadella and chopped had the highest values, indicating that the cooking conditions were more severe for these products than those used in the sausages. The ratio of total creatine/protein permitted an estimation of muscular protein to be made. According to the mean value for this ratio, the products were ordered as: cooked ham, 21.9 > chopped, 17.7 > wieners, 15.9 > mortadella, 13.0 > frankfurters, 12.3mg total creatine per gram of protein.     

Xylose-lysine model systems: The effect of pH on the volatile reaction products

Aqueous molal solutions of xylose and lysine (initial pH 4–9) were refluxed either with control of the pH at 5–0 or without pH control (final pH 2–6). Analysis by gas chromatography (GC) and GC-mass spectrometry resulted in the identification of 58 and 28 compounds, respectively, from the two systems. Furans were the main reaction products in both systems and 2-furfural alone comprised 522 and 999 g kg^?1 of the volatiles, respectively, from the systems with final pH values of 5–0 and 2–6. Maintaining the pH at 5–0 resulted in a higher yield and greater numbers of nitrogen-containing compounds, and monocyclic pyrroles, pyridines and 2,3-dihydro-l H-pyrrolizines were identified only in that system. Aliphatic compounds, alicyclic compounds, benzene derivatives. l-(2–furfuryl)pyrroles and pyrazines were also identified. This investigation is the first report of the formation of 2.3-dihydro-l H-pyrrolizines in a model system containing lysine as the amino compound; a possible mechanism is proposed.     

Effect of Amadori rearrangement products on the non-enzymic browning in model systems

The Amadori product was prepared from D-glucose and L-alanine after Hashiba. The browning process was investigated by determining the absorbance at 520 nm, in aqueous solutions at 110 °C for 5–8 h. Because of the limited access of oxygen and its low solubility in the reaction medium, the browning proceeded after zeroth order kinetics with the maximum browning rate at pH = 8–9. The browning rate remained unaffected by additions of sodium sulphite, rutin. propyl gallate (except when present at high levels), iron(III)chloride or copper(II)chloride but decreased in presence of L-cysteine or iron(II)chloride. Hydrogen peroxide bleached the pigment but did not inhibit the subsequent browning of reaction products. Under experimental conditions the solution of Amadori product did not darken with substantially greater rate than the solution of D-glucose and L-alanine. Lower additions of D-glucose to the solution of Amadori product moderately increased the reaction rate while additions of L-alanine or L-hydroxyproline moderately decreased the browning rate.     

黄酮类化合物在阻断亚硝胺合成中的应用

利用植物有效成分阻断亚硝胺合成是防治癌症的有效途径之一.黄酮类化合物在抑制亚硝化反应中有着广泛的应用.重点探讨黄酮类化合物抑制亚硝化反应的机制,典型植物中黄酮含量变化规律及阻断亚硝胺合成或清除亚硝酸盐的效果,以期为寻求最佳的抗癌药物提供帮助.     

Characteristics and antioxidant activity of Maillard reaction products from psicose-lysine and fructose-lysine model systems

D-Psicose, an epimer of D-fructose isomerized at C-3 position, is a rare ketohexose that is thought to be beneficial for obese people and diabetic patients as a noncaloric sweetener. In the present study, model Maillard reaction products were obtained from D-psicose (or D-fructose) and L-lysine heating at 120 °C up to 8 h with the initial pH 9.0. The changes in pH, UV-vis absorbance, and free amino groups during the reaction were detected. Moreover, the antioxidant potential of the Maillard reaction products at different intervals was investigated. Although there was almost no difference in the oxygen radical absorbance capacity, the Maillard reaction products from psicose performed better than that from fructose in the radical-scavenging activity of 2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt and 1, 1,-diphenyl-2-picryl-hydrazyl. The reducing power of the Maillard reaction products from psicose was also stronger than that from fructose. These results indicated that psicose played an effective role in the Maillard reaction and its Maillard reaction products could act as potential antioxidants in food industry.     

Interaction between Maillard reaction products and lipid oxidation in starch‐based model systems

The effect of Maillard reaction products (MRPs) on the kinetics of lipid oxidation in intermediate‐moisture model systems containing pregelatinised starch, glucose, lysine and soybean oil has been studied. The samples, either containing all components or excluding one or more of them, were heated at 100 °C for different times. Lipid oxidation and browning indices were measured and the results confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted, the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of MRPs was also evaluated using a peroxide‐scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples. © 2000 Society of Chemical Industry     

The pathways for the removal of acrylamide in model systems using glycine based on the identification of reaction products

The reaction between acrylamide and glycine was studied in the aqueous model system heated at 150 °C. The main reaction products were identified as C₅H₁₀N₂O₃, C₈H₁₅N₃O₄, C₇H₁₂N₂O₅ and C₁₀H₁₇N₃O₆ using HPLC-MS/MS, IT-TOF and NMR. Both of the critical intermediates were identified as glyoxylic acid and iminodiacetic acid. The pathways for the removal of acrylamide by glycine were proposed as the Michael addition between acrylamide and glycine with or without the initial oxidation of glycine. The changes in the contents of reactants and products provided quantitative evidence for the above pathways. The addition products between acrylamide and other 14 amino acids were identified by HPLC-MS/MS also.     

Determination of the decomposition products of Usal in model systems and determination of dioxopiperazine in soft drinks by HPLC

A HPLC method for the determination of Usal (Aspartame hydrochloride, L-aspartyl-L-phenylalanine methyl ester hydrochloride) and its decomposition products was elaborated. Aspartic acid, phenylalanine, phenylalanine methyl ester, aspartyl-phenylalanine, phenylalanyl-aspartic acid, 5-benzyl-3,6-dioxo-2-piperazineacetic acid (DOP) and Usal were separated on Separon SI C-18. The mobile phase was: 0.5 M NaH2PO4 (pH 2.1) and methanol (85:15 v/v). The detection was carried out at 200 nm. The method for DOP determination was tested by the analysis of 10 types of soft drinks to which DOP was added. In two newly developed sorts of soft drinks sweetened with Usal the formation of DOP was followed during storage. The DOP increment after 34 days of storage reached 0.7 and 6 mg/l at 7 and 20 degrees C, resp. The method is also suitable for DOP determination in the sweetener itself.     

Various instrumental and biochemical parameters as ageing indicators of beef Longissimus dorsi muscle and their relation to creatine and creatinine content

The main dietary source of creatine is red meat. Its ageing is accompanied by deep changes in chemical composition and structure of muscle tissues. The effect of ageing (nonaged—i.e. 24 h post mortem vs. 14 and 28 days post mortem at 1 °C) on the content of creatine and creatinine, on the creatine/creatinine ratio and on other ageing indicators, such as instrumentally measured colour values, pH_ultimate values, length of myofibrilar fragments and total free amino acid content of beef Longissimus dorsi muscle. Muscles originated from eight commercially slaughtered Simmental bulls, 19–20 months old. Generally, all parameters measured were influenced by ageing time at the 5% level or less. Approximately 0.1 unit higher pH values and 1 unit higher colour L ^*, a ^* and b ^* values of ageing samples compared to nonaged was found. Length of myofibrilar fragments being in average the highest (69 μm) for nonaged samples, 34 μm for 14 days aged and the lowest (17 μm) for 28 days aged sample. Higher content of total free amino acids released during 14 and 28 days of storage (10.19 and 18.71 μmol/g) than from nonaged beef (19.75 μmol/g) was found. Creatine content significantly declined with increasing days of ageing (nonaged 6.05 mg/g, 14 days 5.86 mg/g, 28 days 5.66 mg/g). On the contrary, the total content of creatine (creatine + 1.159 × creatinine) was not markedly affected by 14 days of ageing (nonaged 6.27 mg/g, 14 days 6.14 mg/g), although significant difference between nonaged and 28 days aged groups (5.95 mg/g) was observed. It was assumed that the creatinine/creatine ratio might be a good indicator of ageing rate for beef (R ² = 0.974).     

Formation of mutagens in an amino acid-glucose model system and the effect of creatine

Heating of amino acids and glucose in a water solvent system produces substantial amounts of mutagens only at alkaline pH (10·5). Positive response was demonstrated with the Salmonella tester strains TA 98, TA 1538, TA 97, TA 1537 and TA 100. When creatine was added to this system prior to heating, mutagens were formed at all pHs tested (pH 4, 7, 9 and 10·5) and highest mutagenic activity was recorded at pH 9·0 and pH 7·0. The amount of mutagen produced was dependent on the creatine concentrations. A linear increase of mutagenic activity was recorded in the threonine-glucose system when creatine concentration increased to 0·5m. Similar results were also demonstrated in the glycine-glucose system up to 0·2-0·3m creatine. The increased amount of mutagenic activity found in the presence of creatine was demonstrated to be active only against the frame shift tester strains (TA 98 and TA 97) and not when tested with the TA 100 strain.HPLC analyses indicated that the mutagenic activity found in the pure amino acid glucose system at alkaline pH was also found in the presence of creatine; however, the major peak of mutagenic activity in the creatine containing system was not found in the absence of creatine.     

The influence of pH on the non-volatile reaction products of aqueous Maillard model systems by HPLC with diode array detection

Aqueous solutions of sugar (xylose or glucose) and amino acid (glycine or lysine monohydrochloride), one molal with respect to each reactant, were heated without control of the pH for up to 120 min. Total reaction products were analysed by HPLC with diode array detection and the data obtained were distinctive and different from those of the corresponding model systems maintained at pH 5 throughout heating. Less unresolved material and variations in its chromatographic behaviour suggested differences in the melanoidins formed. Resolved peaks from the xylose-lysine and glucose-lysine systems were grouped into spectral families, based on their diode-array spectra. For xylose-lysine, seven of these peaks were common to the systems heated both with and without pH control for 15min (based on retention time and spectral matching). No peaks were common to both glucose-lysine systems heated for 120min.