Application of fluorescence spectroscopy and chemometrics in the evaluation of processed cheese during storage

Front face fluorescence spectroscopy is applied for an evaluation of the stability of processed cheese during storage. Fluorescence landscapes with excitation from 240 to 360 nm and emission in the range of 275 to 475 nm were obtained from cheese samples stored in darkness and light in up to 259 d, at 5, 20 and 37 degrees C, respectively. Parallel factor (PARAFAC) analysis of the fluorescence landscapes exhibits four fluorophores present in the cheese, all related to the storage conditions. The chemometric analysis resolves the fluorescence signal into excitation and emission profiles of the pure fluorescent compounds, which are suggested to be tryptophan, vitamin A and a compound derived from oxidation. Thus, it is concluded that fluorescence spectroscopy in combination with chemometrics has a potential as a fast method for monitoring the stability of processed cheese.     

Application of fluorescence spectroscopy for monitoring changes in nonfat dry milk during storage

The objective of this study was to determine if fluorescence spectroscopy could be used to characterize the biochemical characteristics of nonfat dry milk (NDM) caused by manufacturing and storage conditions. Nine low-heat NDM samples were collected from 3 manufacturers and stored at 4 temperatures (4, 22, 35, and 50°C) for 8 wk. The spectra of Maillard products, tryptophan, and riboflavin were recorded and analyzed with principal components analysis. Colorimetric indices L*, a*, and b* were also determined. The before-storage NDM samples collected from each manufacturer had different fluorescent characteristics. Inconsistency was observed for the NDM samples collected from 1 manufacturer, whereas the samples from the other 2 manufacturers displayed consistent fluorescence characteristics. Biochemical reactions, such as Maillard reaction, modification of the tryptophan environment, and degradation of riboflavin occurred during the manufacturing process. For each of the data collections, discrimination of the NDM samples stored at 50°C from the samples stored at 4, 22, and 35°C was observed in the similarity maps. The factor loadings of the first 2 principal components for the fluorescence spectra of the samples before storage were similar to the principal components analysis results of the samples during storage. It appears that similar factors are responsible for the variation in the samples before storage and their changes during storage. Additionally, storage of the samples at 50°C accelerated these reactions. The results demonstrate that front-face fluorescence spectroscopy, coupled with multivariate statistical methods, can be utilized as an analytical technique to monitor variation in NDM samples from different manufacturers and changes during storage.     

前表面荧光法在牛奶美拉德反应检测中的应用

在热处理中,牛奶中的乳蛋白容易与乳糖发生美拉德反应,使牛奶的色泽、风味、营养等发生变化。与传统化学检测法相比,前表面荧光法具有快速灵敏、前处理简便等优点。为了评估前表面荧光法在检测牛奶美拉德反应程度上的准确性和适用性,本文对比了不同热处理下牛奶的美拉德反应的荧光图谱和美拉德产物的含量,分析了指标间的相关性。并以前表面荧光法和羟甲基糠醛含量建立模型对商业乳品进行预测,结果良好,为荧光检测的工业应用提供理论依据。结果显示,前表面荧光法可应用于牛奶前中期美拉德产物的无损检测。     

基于三维荧光光谱的多种植物油中多菌灵残留测定

目的 开发一种适用于植物油中多菌灵残留的快速准确的检测方法。方法 采用三维荧光光谱结合化学计量学方法对植物油中残留多菌灵进行定量分析。在多菌灵中添加3种不同植物油提取物来制备样本,并测其三维荧光光谱。采用平行因子（PARAFAC）、满秩平行因子（FPA-PARAFAC）和交替三线性分解（ATLD）3种算法对样本中的多菌灵进行分析,比较3种算法的选择性、灵敏度、检出限、定量限等品质因子（FOM）,并采用椭圆联合置信区间（EJCR）进行检验。结果 PARAFAC、FPA-PARAFAC和ATLD对多菌灵加标回收率分别为96.98%~112.64%,97.05%~112.36%,93.07%~104.47%,ATLD的平均回收率最接近100%。在FOM及EJCR分析中,ATLD相比其他两种算法有着更好的表现。结论 采用三维荧光光谱结合化学计量学测定植物油中残留多菌灵,可获得优秀的定量结果。     

Front-face fluorescence spectroscopy and chemometrics in analysis of yogurt: rapid analysis of riboflavin

The present study demonstrates the use of front-face fluorescence spectroscopy and chemometrics for monitoring light-induced changes in plain yogurt during storage. Fluorescence analysis is suggested as a new rapid method for measuring riboflavin content in yogurt. Fluorescence landscapes with excitation wavelengths from 270 to 550 nm and emission wavelengths in the range 310 to 590 nm were obtained from front-face fluorescence measurements directly on yogurt samples during two storage experiments over a period of 5 wk at 4 degrees C. Yogurts were stored in two different packaging materials (polylactate and polystyrene) and under fluorescent light (3500 lux) or in darkness. Principal Component Analysis of unfolded fluorescence emission spectra revealed systematic changes in fluorescence signal throughout the storage period, strongly related to the storage conditions, i.e. storage time and differences in packaging materials. Correlation between fluorescence spectra and riboflavin content determined by the standard AOAC fluorometric method was evaluated using a Partial Least Square Regression model. The regression model showed a good ability to predict riboflavin in plain yogurt with a high correlation (R = 0.99) and a prediction error of 0.092 microgram riboflavin/g. Thus, it is concluded that nondestructive fluorescence spectroscopy can be used to monitor riboflavin content in yogurt, and that the suggested rapid method has the potential to substitute the standard method for analysis of riboflavin in yogurt.     

荧光-化学计量学法快速检测牛奶中磺胺甲基异恶唑残留

食品中抗生素的残留威胁着消费者的健康。目前用于食品中抗生素残留的检测方法通常经过复杂的预处理、耗时繁琐,而荧光检测具有快速、灵敏度高的特点。本文旨在利用荧光-化学计量学方法建立牛奶中磺胺类抗生素残留的快速检测方法,应用所建立的校正模型对6个品牌共14种商业巴氏奶和UHT奶（包括全脂奶、脱脂奶、半脱脂、高钙）的未知样品进行预测,结果表明,偏最小二乘-判别法（PLS-DA）模型能准确地区分磺胺甲基异恶唑最大残留量上下的样品,假阴性的概率为3.12%,远小于欧盟规定的5%。偏最小二乘法（PLS）法对样品进行定量测定时,在0～210μg/L范围内有良好的线性关系,相关系数为0.9992,样品的回收率可达到87.9%～131.6%,方法的检测限（CCα）为2.54μg/L,定量限（CCβ）为5.07μg/L,平均相对标准偏差为3.24%。该方法可应用于液态乳中磺胺甲基异恶唑残留的快速检测。      

近红外光谱分析技术在制浆过程中的应用

近红外光谱分析技术是一种高效、无损的快速分析方法,作为实时成分分析和过程控制的先导技术,正逐渐成为制浆过程分析测量领域的研究热点。文中介绍了近红外光谱分析技术的测量原理、技术特点、建模方法等,并对近红外光谱分析技术在制浆过程中的原料分类筛选、材性分析、纸浆性能评估等方面的应用进行了综述。     

红外光谱技术在食品检测中的应用

红外光谱在食品检测研究中的应用较为广泛, 具有样品前处理简单、操作方便、易于推广, 且对气体、液体和固体样品均可准确检测等优点, 表现出良好的发展前景。本文概述红外光谱技术的检测基本原理和化学计量学在红外光谱技术中的应用, 在简要对比常用检测分析方法的优缺点基础上, 对红外光谱技术在食品鉴伪、品质研究、有害物检测和成分分析等领域的研究进展进行了综述, 详细介绍该技术与化学计量学结合评价食品品质的应用实例, 同时提出目前研究存在的局限性, 并陈述改进建议, 且对该技术在食品检测研究的未来发展方向作出展望, 以期为该技术的深入研究提供参考。     

近红外光谱结合化学计量学方法在油脂检测中的应用

近红外光谱结合化学计量学技术由其独特的技术优势在油脂掺假分析领域已取得广泛应用。本文主要对近红外光谱结合化学计量学技术的原理及特点进行论述,并综述了近年来在油脂定性及定量分析方法中应用较为广泛、实用性较强的化学计量学方法,即聚类分析、主成分分析、支持向量机、人工神经网络、主成分回归以及偏最小二乘法结合近红外光谱在油脂掺假分析中的应用,并展望了该技术的发展前景。     

Rapid determination of tetracycline in milk by FT-MIR and FT-NIR spectroscopy

The feasibility of measuring tetracycline at the ppb levels in milk was investigated by Fourier transform mid-infrared (FT-MIR) and Fourier transform near-infrared (FT-NIR) spectroscopic techniques. Milk samples spiked with different concentrations of tetracycline were scanned using FT-MIR and FT-NIR spectroscopy. Suitable spectral wave number regions were selected for principal least square (PLS) regression models development. Prediction errors were high when the calibration model was developed using the wide range of tetracycline concentrations (4 to 2000 ppb) in milk. Maximum correlation coefficient (R2) value of about 0.89 was obtained for the validation models developed using different concentration ranges. Prediction errors were high for FT-NIR method. Results indicated that FT-MIR spectroscopy could be used for rapid detection of tetracycline hydrochloride residues in milk.     

Quantitation of Lamb Content in Mixtures with Raw Minced Beef Using Visible, Near and Mid-Infrared Spectroscopy

Samples of beef (32), lamb (33) and 5%, 10% and 20% (w/w) lamb-in-beef mixtures (33 each) were minced and reflectance scanned in the visible, near and mid-infrared spectral regions. Partial least squares (PLS) regression models were developed to predict percentage lamb content using each spectral region alone and combinations of all three. The most accurate models combined mid-IR (800-2000 cm^-1) and near IR (1100-2498 nm) spectral data following 2^nd derivatization; standard errors of prediction of 0.91% (0–20% range in lamb content) and 4.1% (0–100% range in lamb) were obtained. This technique may be useful for screening such meat mixtures.     

柑橘近红外光谱无损检测技术研究进展

柑橘是世界第一大水果,中国是柑橘生产和销售大国.现阶段我国柑橘产业存在各环节分离、加工技术粗糙、采后品质分级落后等问题,导致我国柑橘在国际市场上缺乏竞争力.对柑橘产品进行检测与分级是提高竞争力的有效手段,然而传统的柑橘品质检测手段如肉眼识别法、图像识别法、化学滴定法等存在费时费力、精度不高等缺陷,且化学滴定法等对样品具...     

近红外光谱在酒精发酵过程检测中的应用

论述了近红外光谱DA7200在酒精发酵过程检测中的应用,对液化、糖化、发酵工序的过程产物、低聚糖及有机酸的检测,探讨了改善进样装置及HPLC双检测器系统对定标模型的改进效果,并进行了准确性和重复性验证。结果表明,近红外光谱法可以满足低聚糖及有机酸的检测要求,为发酵工业提供了过程产物控制的参考方法。     

红外光谱分析技术在白酒行业中的应用进展

傅里叶变换红外光谱分析技术具有制样简单,检测方便快捷的特点,在实际工农业生产过程中发挥着重要作用。该文评述了近20年来傅里叶变换红外光谱分析技术在白酒行业研究与应用进展,内容涉及白酒酒体质量控制研究,白酒香型、真伪、年份及等级等真实性特征鉴别,高粱原料、大曲、酒醅等生产过程主要物料的关键指标检测,并对今后红外光谱技术在白酒行业的应用发展方向进行了展望,旨在为红外光谱分析技术在白酒行业的深入应用提供参考依据。     

A NOVEL METHOD FOR BITTERNESS DETERMINATION IN BEER USING A DELAYED FLUORESCENCE TECHNIQUE

The established technique of time-resolved fluorescent spectroscopy has been applied to the rapid measurement of beer bitterness. This novel application utilises the unique long-lived fluorescence properties of the lanthanide, europium. Europium ions have the ability to selectively chelate β-tricarbonyl structures such as the iso-humulones. The resultant complex is measured by irradiating the sample at a specific wavelength and measuring the intensity of the long-lived emission. The bitterness method measures the total contribution of iso-alpha acids and related congeners. A linear relationship between standard iso-alpha acids solutions and emission intensity was found. However, in beer the effects of colour and other interfering compounds were significant. Decolourization of the beer did not improve the correlation with BU. This paper presents a preliminary investigation into the potential applications of this novel method.     

近红外光谱技术及其在液态食品上应用的研究进展

近红外光谱技术结合化学计量手段的分析方法具有快速、无损等优点,在农产品和食品安全检测中的应用日渐广泛。通过对近红外光谱技术的理论基础和常用的化学计量手段概述,从食用油类,酒类,蜂蜜、果汁饮料类,食醋等调味品类,奶制品类5个方面,综述了该技术在液态食品中的最新应用,提出了应用中的问题和未来的发展方向。