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核磁共振横向弛豫时间(T2)反映不同发酵时间的豆豉制品中氢质子组分及运动性,从而可得出不同发酵时间的豆豉制品中水分的变化规律。采用CPMG(Carr Purcell meiboom-gill)测试,经PQ001分析软件及CPMG序列采集豆豉T2信号,得到T2谱图。谱图显示豆豉中氢质子大致分为4种相态:T21(0.01~1.52 ms)、T22(1.52~7.05 ms)、T23(7.05~100 ms)、T24(100 ms)。从组分含量分析得出,随着厌氧发酵的进行、微生物分泌的酶系对蛋白质为主的原料的分解、微生物的代谢活动、风味物质的形成,结合水含量不断减小,不易流动水即细胞内水存在相互转化的过程(T22与T23),自由水含量也有一定程度减小。随着发酵的进行,豆豉的鲜味成分大量形成、氨基酸态氮显著提高,风味物质显著增加,豆粒软化色泽加深。利用核磁共振法能够间接反映发酵过程中豆豉风味形成、质构等指标的变化。 相似文献
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M. J. R. Nout 《Journal of the Institute of Brewing》2011,117(4):516-522
Fen liquor is typical of Chinese light‐flavour liquor (alcoholic spirit), which is fermented from sorghum with Fen‐Daqu powder. Fen‐Daqu is a saccharifying agent and fermentation starter in this fermentation process and in Fen traditional vinegar. To investigate the changes of biochemical components in Fen‐Daqu during the incubation, samples at seven incubation stages were analyzed by 1H nuclear magnetic resonance (NMR) spectrometry and principal component analysis (PCA). This revealed clear separation of the samples obtained from different incubation stages in the principal component plots by combining PC1 and PC2, which cumulatively accounted for 93.27% of the variance. The major compounds that contributed to discrimination were acetate/alanine, arginine, ascorbate, betaine, choline, ethanol, fructose, galactose, glucose, glucitol, glycerate, lactate, maltose, mannitol, phenylalanine, proline, propylene glycol, threonine and tryptophan. These compounds were regarded as the representative metabolites or biomarkers characteristic for each incubation stage and were related with microbiological changes of importance for quality control in Fen‐Daqu production. 相似文献
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Tan Yang Bin Wu Xianglin Yue Ling Jin Ting Li Xuehua Liang Shuangyan Ding Kaiwen Feng Ganhui Huang Jinsheng Zhang 《Journal of dairy science》2021,104(2):1494-1503
Rapid and sensitive detection technology is the key to preventing food-borne disease outbreaks. In this study, a low-field nuclear magnetic resonance (NMR) biosensor based on polyamidoamine dendrimers was prepared for the rapid detection of Salmonella in milk. The polyamidoamine dendrimer was biotinylated by amide reaction and chelated to diethylene triamine pentacetate acid and gadolinium to form magnetic complexes. The antibody and magnetic complexes were combined through a streptavidin–biotin system using streptavidin as an intermediate bridge to obtain the immunoprobe. Salmonella was captured by the immunoprobe via antigen–antibody interaction and then separated from the mixture by membrane filtration. Finally, the longitudinal relaxation signal of the filtrate was obtained by NMR. The biosensor had excellent anti-interference capability and could detect Salmonella within 1.5 h at a sensitivity of 103 cfu mL–1. This method based on NMR can realize detection in complex samples and has the potential to be a quick and nondestructive method for detecting target bacteria. 相似文献
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M. DE LUCA P. ROCHA-FILHO J.L. GROSSIORD A. RABARON C. VAUTION M. SEILLER 《International journal of cosmetic science》1991,13(1):1-21
The main purpose of this article is to define multiple emulsions, their preparation (new materials and manufacturing processes) methods of characterisation and analysis, and their applications in cosmetology and pharmacy.
The second part is devoted to a presentation of the investigation in our laboratory into the optimal manufacturing process to provide stable formulations. The study of release mechanisms from such formulations mainly shows a breakdown of multiple droplets which could be controlled by variation of solute concentration. 相似文献
The second part is devoted to a presentation of the investigation in our laboratory into the optimal manufacturing process to provide stable formulations. The study of release mechanisms from such formulations mainly shows a breakdown of multiple droplets which could be controlled by variation of solute concentration. 相似文献
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随着经济的快速发展和生活水平的不断提高,食品的营养价值、品质安全受到人们的广泛关注。代谢组学是继基因组学、转录组学和蛋白质组学后的一门新兴组学,日益成为食品科学研究中一种重要的分析技术。代谢处于生命活动调控的末端,相较于其他组学,代谢组学更接近表型。作为一种新型研究手段,代谢组学从整体水平上研究生命体代谢活动和状态,对生物体系中的小分子化合物进行定性定量研究,具有高通量、高灵敏性和高准确性等特点,可以有效克服传统方法的局限性。本文概述了代谢组学的概念、研究方法、分析技术,并介绍了近年来国内外对代谢组学在食品营养、食品安全、食品加工、食品溯源及转基因食品等方面的应用与研究进展,为后续研究提供参考。 相似文献
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鲜切竹笋冷藏过程中生理和生化变化的研究 总被引:10,自引:2,他引:8
研究了最少化加工(MP)对竹笋呼吸强度的影响及MP竹笋贮藏期间呼吸强度的变化。测定了4℃下不同部位的竹笋的总糖、还原糖、总酚、木质素、纤维素、丙二醛(MDA)含量及苯丙氨酸解氨酶(PAL)和多酚氧化酶(PPO)活性的变化。结果表明:加工造成的机械损伤导致了竹笋呼吸强度的迅速增加,在随后的贮藏过程中又逐步减弱。竹笋尖部和中部的总糖和还原糖的含量贮藏前期下降、后期增加,而基部的总糖呈上升趋势。竹笋尖部和中部的总酚含量先减少后上升,之后再减少,而基部的总酚含量没有大的变化。纤维素和木质素含量贮藏前期从尖部的到基部的逐渐增加,贮藏中期从尖部的到基部的有不同程度的下降,贮藏后期有不同程度的增加。各部位MP竹笋的MDA含量在贮藏初期急剧上升,随后维持在高水平状态。尖部的PAL和PPO的活性高于中部和基部的。各部位的PAL活性贮藏前期上升,中期下降,后期又上升。尖、中部的PPO活性贮藏前期上升,后期下降,但仍维持在较高水平,而基部的PPO活性一直下降。 相似文献
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目的 建立可同时测定保健品中烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleotide,NAD+)及其前体化合物含量的核磁共振波谱法。方法 采用核磁共振波谱技术,优化检测条件后,开发了标准曲线法和定量核磁共振(quantitative nuclear magnetic resonance,qNMR)法两种定量检测方法,用于测定保健品中2种形式的NAD及其4种前体化合物。结果 确定了各目标化合物的特征峰。对于标准曲线法,6种目标化合物的线性关系良好(≥0.9999),除烟酰胺(nicotinamide,NAM)的定量限为0.5 mmol/L外,其他5种目标化合物的定量限均为0.2 mmol/L。考察了两种具有代表性的NAD+前体化合物的日间和日内重现性,烟酰胺单核苷酸(nicotinamide mononucleotide,NMN)和NAM的日间重现性分别为0.21%和0.37%,日内重现性分别为1.03%和1.44%。用标准曲线法和qNMR两种方法分别对收集的10个NAD+补充剂保健品进行检测,误差合理(<5%)。结论 建立的核磁共振方法具有良好的可靠性和灵敏度,可用于保健品中NAD+及其前体化合物的生产控制和市场监管。 相似文献
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M.S. Klein M.F. Almstetter G. Schlamberger K. Dettmer H.H.D. Meyer W. Gronwald 《Journal of dairy science》2010,93(4):1539-7367
Milk production in dairy cows has dramatically increased over the past few decades. The selection for higher milk yield affects the partitioning of available nutrients, with more energy being allocated to milk synthesis and less to physiological processes essential to fertility and fitness. In this study, the abundance of numerous milk metabolites in early and late lactation was systematically investigated, with an emphasis on metabolites related to energy metabolism. The aim of the study was the identification and correlation of milk constituents to the metabolic status of the cows. To investigate the influence of lactation stage on physiological and metabolic variables, 2 breeds of different productivity were selected for investigation by high-resolution nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. We could reliably quantify 44 different milk metabolites. The results show that biomarkers such as acetone and β-hydroxybutyrate are clearly correlated to the metabolic status of the individual cows during early lactation. Based on these data, the selection of cows that cope well with the metabolic stress of early lactation should become an option. 相似文献
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目的:采用氢核磁共振(1H nuclear magnetic resonance,1H NMR)结合正交偏最小二乘法(Orthogonal partial least squares,OPLS)建立对蛹虫草中金针菇、杏鲍菇和香菇掺假的快速鉴别方法。方法:主成分分析得分图显示,不同类型的掺假样品并不能完全分离。采用两步法进一步提高模型的鉴别能力,首先对纯蛹虫草和掺假蛹虫草进行OPLS-DA分析,模型显示真假蛹虫草分类良好,两类样品存在明显区别。然后对所有20% (w/w)掺假蛹虫草进行了O2PLS-DA模型分析,通过分别由28个和12个样本组成的训练和测试集来检查鉴别能力的准确性。结果:模型整体拟合优度为R2X = 75.2%, R2Y = 92.3%,整体交叉验证系数Q2 = 89.7%,掺假物金针菇、杏鲍菇和香菇能够被准确辨别。结论:1H NMR代谢指纹图谱结合化学计量学,对于真伪蛹虫草及掺假类型能够有效鉴别,可用于大批量商业筛选。 相似文献
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《Journal of dairy science》2022,105(1):535-548
Nuclear magnetic resonance spectroscopy was applied to investigate the association between milk metabolome and udder quarter health status in dairy cows. Mammary gland health status was defined by combining information provided by traditional somatic cell count (SCC) and differential SCC (DSCC), which expresses the percentage of neutrophils and lymphocytes over total SCC. Quarter milk samples were collected in triplicate (d 1 to 3) from 10 Simmental cows, 5 defined as cases and 5 defined as controls according to SCC levels at d 0. A total of 120 samples were collected and analyzed for bacteriology, milk composition, SCC, DSCC, and milk metabolome. Bacteriological analysis revealed the presence of mostly coagulase-negative staphylococci in quarter milk samples of cows defined as cases. Nuclear magnetic resonance spectra of all quarter samples were first analyzed using the unsupervised multivariate approach principal component analysis, which revealed a specific metabolomic fingerprint of each cow. Then, the supervised cross-validated orthogonal projections to latent structures discriminant analysis unquestionably showed that each cow could be very well identified according to its milk metabolomic fingerprint (accuracy = 95.8%). The comparison of 12 different models, built on bucketed 1-dimensional NOESY spectra (noesygppr1d, Bruker BioSpin) using different SCC and DSCC thresholds, corroborated the assumption of improved udder health status classification ability by joining information provided by both SCC and DSCC. Univariate analysis performed on the 34 quantitated metabolites revealed lower levels of riboflavin, galactose, galactose-1-phosphate, dimethylsulfone, carnitine, hippurate, orotate, lecithin, succinate, glucose, and lactose, and greater levels of lactate, phenylalanine, choline, acetate, O-acetylcarnitine, 2-oxoglutarate, and valine, in milk samples with high somatic cells. In the 5 cases, results of the udder quarter with the highest SCC compared with its symmetrical relative were in line with quarter-level findings. Our study suggests that increased SCC is associated with changes in milk metabolite fingerprint and highlights the potential use of different metabolites as novel indicators of udder health status and milk quality. 相似文献
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《Journal of dairy science》2022,105(12):9702-9712
Effective traceability tools able to characterize milk from pasture are important to safeguard low-input farming systems, niche dairy products, and local traditions. The aims of the present study were to investigate the ability of proton nuclear magnetic resonance (1H NMR) spectroscopy to discriminate between milk produced from cows before and after the beginning of the grazing season, and to assess the effects of grazing on milk metabolites. The research trial involved a single alpine holding with 72 lactating cows. Individual milks were repeatedly sampled from the same animals before (i.e., d ?3 and ?1) and after (i.e., d 2, 3, 7, 10, and 14) the onset of the grazing period. One-dimensional 1H NMR spectra of milk extracts were collected through a Bruker spectrometer. Random forest discriminant analysis was applied to 1H NMR spectra to predict the period of collection for each sample. Data concerning the relative abundance of milk metabolites were analyzed through a linear mixed model, which included the fixed effects of period of sampling, cow breed, stage of lactation, and parity, and the random effect of cow nested within breed. The random forest model exhibited great accuracy (93.1%) in discriminating between samples collected on d ?3, ?1, 2, and 3 and those collected on d 7, 10, and 14. Univariate analysis performed on the 40 detected metabolites highlighted that milk samples from pasture had lower levels of 14 compounds (with fumarate being the most depressed metabolite) and greater levels of 15 compounds (with methanol and hippurate being the most elevated metabolites). Results indicate that milk 1H NMR spectra are promising to identify milk produced in different conditions. Also, our study highlights that grazing is associated with significant changes of milk metabolic profile, suggesting the potential use of several metabolites as indicators of farm management. 相似文献
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将玉米抗性淀粉和普通玉米淀粉按不同比例配合,加入传统中式香肠中,通过测定核磁共振参数、质构参数及感官评定来评价抗性淀粉及其含量的大小对香肠品质的影响。结果表明:香肠样品体系中抗性淀粉替代率过低或过高都有可能造成样品体系中结合水减少,而体系中自由水则随抗性淀粉替代率的增大而增加。抗性淀粉的替代率在40%~60%之间时,香肠的硬度较小,咀嚼性和弹性相对较好;香肠样品的磁共振弛豫参数与其质构特性显著相关,这充分说明,水分含量及其存在状态是影响香肠质构品质的主要因素之一。 相似文献
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目的:建立一种由氢核磁共振技术(1H-NMR)和偏最小二乘回归分析(PLS)结合的方法来对不同种类食醋进行判别分析。方法:由1H-NMR技术测定的样本化学信息,经MestRe Nova软件转化成数字信息,将数据导入SIMCAP13.0软件中采用PLS进行建模和预测,统计其判别的准确率。结果:山西陈醋、镇江香醋和白醋在PLS得分图中能明显分开,并利用内部和外部的数据模型进行了验证,得出的预测准确率较高,所获得的RMSEE和RMSEP值也说明PLS模型对判别不同种类食醋具有较强的可预测性。结论:本分析方法在不同种类食醋的判别中具有较高的准确性,可为不同食醋的判别提供一种简单方法。 相似文献
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核磁共振(nuclear magnetic resonance,NMR)波谱分析利用具有自旋性质的原子核在感应磁场中的能级跃迁分析物质的化学组成和空间结构,基于NMR代谢组学技术主要利用生物体液的核磁共振谱图所提供的生物体内全部小分子代谢物的丰富信息,通过对这些信息的多元统计分析,定性或者定量分析所有小分子代谢物。由于这种技术具有独特的优势,因而在肉品科学中的应用受到广泛的关注。本文介绍了NMR基本原理、NMR波谱解析和NMR代谢组学数据处理方法,综述了NMR代谢组学技术在肉品科学中的应用,为进一步阐明小分子代谢物对肉品质的影响机理提供了支持。 相似文献