Feasibility study on the potential of visible and near infrared reflectance spectroscopy to measure alpaca fibre characteristics

Visible (Vis) and near infrared (NIR) reflectance spectroscopy is a rapid and non-destructive technique that has found many applications in assessing the quality of agricultural commodities, including wool. In this study, Vis and NIR spectroscopy combined with multivariate data analysis was investigated regarding its feasibility in predicting a range of fibre characteristics in raw alpaca wool samples. Mid-side samples (n = 149) were taken from alpacas from a range of colours and ages at shearing time over 4 years (2000 to 2004) and subsequently analysed for fibre characteristics such as mean fibre diameter (MFD) and standard deviation (and coefficient of variation), spin fineness, curvature degree (and standard deviation), comfort factor, medullation percentage (by weight and number in white samples only) using traditional reference laboratory testing methods. Samples were scanned in a large cuvette using a FOSS NIRSystems 6500 monochromator instrument in reflectance mode in the Vis and NIR regions (400 to 2500 nm). Partial least squares (PLS) regression was used to develop a number of calibration models between the spectral and reference data. Mathematical pre-treatment of the spectra (second derivative) as well as various combinations of wavelength range were used in model development. The best calibration model was found when using the NIR region (1100 to 2500 nm) for the prediction of MFD, which had a coefficient of determination in cross-validation (R2) of 0.88 with a root mean square standard error of cross validation (RMSECV) of 2.62 μm. The results show the NIR technique to have promise as a semi-quantitative method for screening purposes. The lack of grease in alpaca wool samples suggests that the technique might find ready application as a rapid measurement technique for preliminary classing of shorn fleeces or, if used directly on the animal, the technology might offer an objective tool to assist in the selection of animals in breeding programmes or shows.     

Reliability of visible reflectance spectroscopy in discriminating between pasture and stall-fed lambs from thin and fat-tailed sheep breeds in dry and hot environment

Considering the additional market value of pasture meat, many authentication methods were developed to discriminate it from meat produced in conventional systems. The visible reflectance spectroscopy technique has proved its efficiency under European conditions and breeds. The present study tested the reliability of this method to discriminate between pasture-fed (P) and stall-fed (S) lambs under North African conditions and investigated the effect of feeding system (FS) (P v. S) and breed (Barbarine; Queue Fine de l’Ouest; and Noire de Thibar) on weight and colour of perirenal, subcutaneous and caudal fat. A total of 18 P and 18 S lambs were used with 6 P and 6 S lambs for each breed. The colour and the reflectance spectrum of different fat tissues were measured. The FS affected weights of all fat tissues and all colour parameters of perirenal and subcutaneous fat (P ≤ 0.01); it almost affected redness and yellowness of caudal fat (P ≤ 0.05; P ≤ 0.01). In all adipose tissues, lightness was higher and both redness and yellowness were lower for S lambs than P lambs. The breed affected weight, lightness and redness of perirenal fat and weight and redness of subcutaneous fat with significant interaction with FS for subcutaneous fat data. To discriminate P lambs from S lambs, the reflectance spectrum of perirenal, subcutaneous and caudal fat at wavelengths between 450 and 510 nm (Method 1, M1) or at wavelengths between 400 and 700 nm using partial least squares discriminative analysis as a classification method (Method 2, M2) were used. M2 yielded to a higher proportion of correctly classified lambs compared with M1 (P = 0.001). The proportion of correctly classified lambs using M2 was 76.4, 75.0 and 80.0% for perirenal, subcutaneous and caudal fat for P lambs and 83.3, 76.4 and 100.0% for S lambs. Despite lower reliability in comparisons to European researches, this study confirmed the efficiency of visible reflectance spectroscopy technique applied on perirenal fat in feeding systems authentication under North African conditions and spotted the caudal fat as a new support for better classification of fat-tailed breeds.     

Discrimination of pasture-fed lambs from lambs fed dehydrated alfalfa indoors using different compounds measured in the fat, meat and plasma

The last decade has seen important developments in the use of carotenoid pigments to authenticate pasture-feeding in ruminants. However, dehydrated alfalfa is sometimes incorporated in grain-based concentrates fed to stall-raised lambs, which may affect the reliability of the pasture-feeding authentication methods based on carotenoids in plasma and fat, due to significant residual carotenoid levels post-dehydration. The aim of this study was to examine whether other compounds can give additional information to authenticate diet and discriminate pasture-fed lambs from lambs fed high levels of alfalfa indoors. Two feeding treatments were compared: pasture-feeding (P) v. stall-feeding with dehydrated alfalfa (A). Each treatment group consisted of seven male Romanov × Berrichon lambs. Pasture-fed (P) lambs grazed a permanent graminaceae-rich pasture maintained at a leafy, green stage, offered ad libitum; they received no supplementation at pasture. A-group lambs were individually penned and fed dehydrated alfalfa and straw; their feed level was adjusted to achieve a similar growth pattern as for P-group lambs. Plasma carotenoid concentration was measured at slaughter by spectrophotometry. The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at 24-h post mortem and used to calculate an index (absolute value of the mean integral (AVMI)) quantifying light absorption by carotenoid pigments present in the fat. The nitrogen (N) stable isotopes ratio (δ15N) in both feed and longissimus dorsi muscle was measured by isotopes ratio mass spectrometry (IRMS). Volatile compounds were analyzed in perirenal fat for five randomly chosen lambs per treatment, using dynamic headspace-gas chromatography-mass spectrometry. Plasma carotenoid concentration and AVMI of the fat did not differ significantly between P- and A-group lambs, but there were significant between-treatment differences in meat δ15N values and in the terpene profiles of perirenal fat. A discriminant analysis performed using three compounds in different animal tissues (δ-cadinene in perirenal fat, δ15N value of the meat and plasma carotenoid concentration) clearly separated pasture-fed lambs from lambs fed high levels of alfalfa indoors.     

Methodological developments in the use of visible reflectance spectroscopy for discriminating pasture-fed from concentrate-fed lamb carcasses

The ability to authenticate the feed given to animals from the animal products has become a major challenge for scientists, monitoring bodies and commercial entities alike. This study compared two methods based on the use of the visible reflectance spectrum of the fat to discriminate pasture-fed (P) from stall concentrate-fed (S) lamb carcasses. A total of 307 (143 P and 164 S) Limousine lambs were used over 2 years. Pasture-fed lambs grazed a permanent pasture that was maintained at a leafy, green vegetative stage, and offered ad libitum; they received no supplementation at pasture. Body weight of P lambs when turning out to pasture and at slaughter averaged 9.2 (standard deviation (s.d.) 2.21) kg and 33.2 (s.d. 2.89) kg, respectively. S lambs were fed indoors on an ad libitum diet of commercial concentrate and hay until slaughter at a mean body weight of 33.7 (s.d. 3.62) kg. The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at slaughter and at 24 h post mortem. Plasma carotenoid concentration was measured at slaughter. In method 1, the fat reflectance spectrum data were used at wavelengths between 450 and 510 nm to calculate an index quantifying light absorption by carotenoid pigments. In method 2, a multivariate analysis was performed over the full set of fat reflectance data at wavelengths between 400 and 700 nm. Method 2 yielded a higher proportion of correctly classified lambs compared with method 1 (P < 0.05 to 0.001), except for measurements made at 24 h post mortem on perirenal fat for S lambs. The proportion of lambs correctly classified using method 2 was 87.4% and 92.9% for measurements made on perirenal and caudal fat at slaughter, and 93.9% and 91.0% for measurements made on perirenal and caudal fat 24 h post mortem. Plasma carotenoid concentrations were higher in P lambs than in S lambs (P < 0.001), which led to correct classification of 90.7% of the lambs.     

应用近红外光谱预测水稻叶片氮含量

以水稻(Oryza sativa)新鲜叶片和干叶粉末两种状态的样品为研究对象, 基于近红外光谱(NIRS)技术, 应用偏最小二乘法(PLS)、主成分回归(PCR)和逐步多元回归(SMLR), 建立并评价了水稻叶片氮含量(NC)近红外光谱模型。结果表明, 基于PLS建立的模型表现最好, 鲜叶氮含量近红外光谱校正模型校正决定系数R_C²为0.940, 校正标准误差RMSEC为0.226; 干叶粉末氮含量的近红外光谱校正模型R_C²为0.977, RMSEC为0.136。模型的内部交叉验证分析表明, 预测鲜叶氮含量内部验证决定系数R_CV²为0.866, 内部验证标准误差RMSECV为0.243; 预测干叶粉末氮含量R_CV²为0.900, RMSECV为0.202。模型的外部验证分析表明, 预测水稻鲜叶氮含量的外部验证决定系数R_V²大于0.800, 外部验证标准误差RMSEP小于0.500, 预测干叶粉末氮含量的R_V²为0.944, RMSEP为0.142。说明, 近红外光谱分析技术与化学分析方法一致性较好, 且基于干叶粉末建立的近红外光谱预测模型的准确性和精确度较新鲜叶片高。     

Differentiation between carcasses from suckling lambs reared with ewe milk or milk replacers by near infrared reflectance spectroscopy of perirenal fat

Near infrared reflectance spectroscopy (NIRS) was used to discriminate between carcasses from Churra breed suckling lambs reared with ewe milk or milk replacers. Samples were scanned over the NIR spectral range (1100–2500 nm). The results showed that NIRS could be used successfully to discriminate the suckling lambs depending on milk source, with a 100% of correctly classified samples. NIRS technology would be a good method, since it is a rapid, economical and little complex method.     

Non-structural carbohydrate: Analysis by near infrared reflectance spectroscopy and its importance as an indicator of plant growth

Plant shoot samples are frequently analysed to assess if crops require additional nitrogen or mineral elements to maintain satisfactory growth. If plant growth is limited by temperature, water stress, disease, lodging or a mineral deficiency, non-structural carbohydrates (NSC) may be accumulated in, or depleted from, tissues especially those in the lower stems. Plant testing laboratories do not routinely analyse NSC to assist in the identification of plant stress probably because skilled technicians and time are required for the wet chemical determination. In this paper we report that routine determination of NSC is possible using near-infrared reflectance spectroscopy; the errors of determination are comparable with traditional chemical methods.The concentration of NSC in the shoots of rice grown in south eastern Australia ranges from 1.6 to 22.8%, as starch. In the shoots of wheat grown in eastern Australia the range is from 2.4 to 35.2%, as fructans. In both crops the NSC content is highly inversely correlated with the shoot nitrogen content. Based on data from commercial wheat and rice crops we suggest that the ratio between nitrogen and NSC can be used to identify crops in which growth has been limited by a stress other than nitrogen and so are unlikely to show the predicted response to an application of nitrogen fertilizer.     

On-line monitoring of the transesterification reaction between triglycerides and ethanol using near infrared spectroscopy combined with gas chromatography

Many analytical procedures have been developed to determine the composition of reaction mixtures during transesterification of vegetable oils with alcohols. However, despite their accuracy, these methods are time consuming and cannot be easily used for on-line monitoring. In this work, a fast analytical method was developed to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol using Near InfraRed spectroscopy and a multivariate approach. The reactions were monitored through sequential scans of the reaction medium with a probe in a one-liter batch reactor without collecting and preparing samples. To calibrate the NIR analytical method, gas chromatography-flame ionization detection was used as a reference method. The method was validated by studying the kinetics of the EtONa-catalyzed transesterification reaction. Activation energy (51.0 kJ/mol) was also determined by considering a pseudo second order kinetics model.     

Use of near infrared reflectance spectroscopy to predict nitrogen uptake by winter wheat within fields with high variability in organic matter

In this study, the ability to predict N-uptake in winter wheat crops using NIR-spectroscopy on soil samples was evaluated. Soil samples were taken from unfertilized plots in one winter wheat field for three years (1997–1999) and in another winter wheat field nearby for one year (2000). Soil samples were analyzed for organic C content and their NIR-spectra. N-uptake was measured as total N-content in aboveground plant materials at harvest. Models calibrated to predict N-uptake were internally cross-validated and validated across years and across fields. Cross-validated calibrations predicted N-uptake with an average error of 12.1 to 15.4 kg N ha⁻¹. The standard deviation divided by this error (RPD) ranged between 1.9 and 2.5. In comparison, the corresponding calibrations based on organic C alone had an error from 11.7 to 28.2 kg N ha⁻¹ and RPDs from 1.3 to 2.5. In three of four annual calibrations within a field, the NIR based calibrations worked better than the organic C based calibrations. The prediction of N-uptake across years, but within a field, worked slightly better with an organic C based calibration than with a NIR based one, RPD = 1.9 and 1.7, respectively. Across fields, the corresponding difference was large in favour of the NIR-calibration, RPD = 2.5 for the NIR-calibration and 1.5 for the organic C calibration. It was concluded that NIR-spectroscopy integrates information about organic C with other relevant soil components and therefore has a good potential to predict complex functions of soils such as N-mineralization. A relatively good agreement of spectral relationships to parameters related to the N-mineralization of datasets across the world suggests that more general models can be calibrated.     

A novel method for analyzing thick tablets by near infrared spectroscopy

A near-infrared (NIR) spectroscopic method to determine content uniformily of a large, thick tablet using an approach that could facilitate future validations has been developed. A CT ibuprofen 800-mg tablet weighs about 1150 mg and is about 18.6 mm wide and 7.6 mm thick. The FT NIR spectrometer was optimized for transmission spectra of the tablets by moving it to the sample compartment and placing it immediately behind the tablet. In spite of this dedicated setup, the transmission spectra obtained were very poor, indicating that the NIR radiation was not reaching the detector. The spectra of the tablet improved with use of a simple preparation in which a flat-face die applies pressure of 20 000 psi to the tablet, this reduced the thickness of the tablet from 7.6 mm to 3.6 mm. A calibration model was developed for tablets with drug content ranging from 70% to 130% of label. The calibration model was tested using a validation set of tablets with a drug content of 752, 800, and 848 mg. The results obtained were within 1.5% of the known drug content of the validation set, tablets. Even with the sample preparation, the content uniformity results of 10 tablets could be determined using this method in less than 1 hour. The approach described in this article could also be used to validate NIR content uniformity methods for orther formulations. Published: July 12, 2001.     

Hemoglobin plus myoglobin concentrations and near infrared light pathlength in phantom and pig hearts determined by diffuse reflectance spectroscopy

To noninvasively determine absolute concentrations of hemoglobin (Hb) plus myoglobin (Mb) in cardiac tissue by means of regular near infrared (NIR) light diffuse reflectance measurements, a first derivative approach was applied. The method was developed to separately calculate oxygenated and deoxygenated [Hb + Mb] as well as an effective pathlength, which NIR light passes through in the tissue between optodes. Applying a cotton wool-based phantom, which mimics muscle tissue, it was shown that the intensity of the pseudo-optical density first derivative depends linearly on both oxygenated and deoxygenated Hb concentration, thereby validating the Lambert-Beer law in the range of 0 to 0.25 mM tetrameric Hb. A high correlation (R = 0.995) was found between concentrations of Hb loaded onto the phantom and those determined spectrophotometrically, thereby verifying the first derivative method validity. The efficiency of the method was tested using in vivo pig hearts prior to and after ischemia initiated experimentally by left anterior descending artery branches occlusion. The results showed that the total [Hb + Mb] was 0.9-1.2 mM heme, the average tissue oxygen saturation was approximately 70% (which reduced to nearly 0% after occlusion), and the NIR (700-965 nm) light pathlength was 2.3 mm (differential pathlength factor [DPF] = 2.7-2.8) in a living heart tissue.     

Evaluation of the bony repair in rat cranial defect using near infrared reflectance spectroscopy and discriminant analysis

We set out to determine whether near infrared reflectance spectroscopy (NIRS) combined with principal component analysis–linear discriminant analysis (LDA) or, variable selection techniques employing successive projection algorithm or genetic algorithm (GA) could evaluate the bone repair in cranial critical‐size (5 mm) defect after stimulation with collagen sponge scaffold and/or infrared low‐level laser therapy directly on the local. Forty‐five Winstar rats were divided into nine groups of five each, namely: group H – healthy, n = 5 (without treatment and without cranial critical‐size defect), (GI positive control – n = 5, 21 days or n = 5, 30 days) without treatment and with cranial critical‐size defect; (GII‐n = 5, 21 days or n = 5, 30 days) cranial critical‐size defect filled with collagen sponge scaffold; (GIII–n = 5, 21 days or n = 5, 30 days) cranial critical‐size defect submitted to low‐level laser therapy; (GIV–n = 5, 21 days or n = 5, 30 days) cranial critical‐size defect submitted to combined collagen sponge scaffold + low‐level laser therapy treatment. In relation to the histological analysis, the collagen sponge scaffold + low‐level laser therapy treatment group (GIV) 30 days showed the best result with the presence of secondary bone, immature bone (osteoid) and newly formed connective tissue (periosteum). GA–LDA model also successfully classified control class of the others classes. Thus, the results provided by the good‐quality classification model revealed the feasibility of NIRS for application to evaluation of the wound healing in rat cranial defect, thanks to the short analysis time of a few seconds and nondestructive advantages of NIRS as an alternative approach for bone repair purposes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1160–1168, 2017     

Synthesis and spectroscopy of near infrared fluorescent dyes for investigating dichromic fluorescence

We developed a series of near infrared (NIR) cyanine dyes to study dichromic fluorescence phenomenon, which provides new protocols for in vivo optical imaging. Preliminary spectroscopic studies show that dichromic fluorescence correlates with structural symmetry. This feature suggests the potential use of dichromic fluorescent molecules to study biological processes that can alter the structural symmetry of the molecular probes.     

Online prediction of fatty acid profiles in crossbred Limousin and Aberdeen Angus beef cattle using near infrared reflectance spectroscopy

The objective of this study was to examine the online use of near infrared reflectance (NIR) spectroscopy to estimate the concentration of individual and groups of fatty acids (FA) as well as intramuscular fat (IMF) in crossbred Aberdeen Angus (AA×) and Limousin (LIM×) cattle. This was achieved by direct application of a fibre-optic probe to the muscle immediately after exposing the meat surface in the abattoir at 48 h post mortem. Samples of M. longissimus thoracis from 88 AA× and 106 LIM× were scanned over the NIR spectral range from 350 to 1800 nm and samples of the M. longissimus lumborum were analysed for IMF content and FA composition. Statistically significant differences (P < 0.001) were observed in most FA between the two breeds studied, with FA concentration being higher in AA× meat mainly. NIR calibrations, tested by cross-validation, showed moderate to high predictability in LIM× meat samples for C16:0, C16:1, C18:0, trans11 C18:1, C18:1, C18:2 n-6, C20:1, cis9, trans11 C18:2, SFA (saturated FA), MUFA (monounsaturated FA), PUFA (polyunsaturated FA) and IMF content with R(2) (SE(CV), mg/100 g muscle) of 0.69 (146), 0.69 (28), 0.71 (62), 0.70 (8.1), 0.76 (192), 0.65 (13), 0.71 (0.9), 0.71 (2.9), 0.68 (235), 0.75 (240), 0.64 (17) and 0.75 (477), respectively. FA such as C14:0, C18:3 n-3, C20:4 n-6, C20:5 n-3, C22:6 n-3, n-6 and n-3 were more difficult to predict by NIR in these LIM× samples (R(2) = 0.12 to 0.62; SECV = 0.5 to 26 mg/100 g muscle). In contrast, NIR showed low predictability for FA in AA× beef samples. In particular for LIM×, the correlations of NIR measurements and several FA in the range from 0.81 to 0.87 indicated that the NIR spectroscopy is a useful online technique for the early, fast and relatively inexpensive estimation of FA composition in the abattoir.     

Comparison of meat and carcass quality in organically reared and conventionally reared pasture-fed lambs

The 'Organic' product label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises recourse to pharmaceuticals or veterinary drugs; however, the product's quality remains an issue that needs to be addressed in response to consumer demand. Consequently, this study was conducted to compare the sensory and nutritional qualities of meat and carcasses from pasture-fed lambs reared organically (O) or conventionally (C). Mean lamb growth profile was kept similar between the two treatments to avoid confounding effects with lamb age or weight at slaughter. The experiment was conducted over 3 years (2005 to 2007) with 12 O and 12 C lambs each year. The O and C treatments differed in the level of on-pasture mineral N fertilisation inducing a higher proportion of white clover in the organic pasture than the conventional pasture. Lambs were slaughtered when they attained a fat class of 2 to 3, and carcass and meat quality were evaluated. Lambs were slaughtered at an average weight and age of 35.3 kg and 156 days in the O treatment, respectively, and 35.2 kg and 155 days in the C treatment, respectively. Sensory evaluation indicated that loin chops from the O treatment had a higher level of abnormal fat odour compared with the C treatment. Carcasses from the O treatment had a softer subcutaneous fat one among 3 years (2007) compared to the C treatment. These results are probably due to a higher proportion of white clover in the diet. Organically reared lambs did offer the slight advantage of muscle fatty acid containing a higher level of stearic acid, which may have positive effects in the prevention of cardiovascular disease in humans. This may be the result of a higher rumen bio-hydrogenation of C18:3n-3 due to differences in the botanical composition between the O and the C pasture. Production system had no effect on the colour characteristics of the meat and subcutaneous fat, except lightness of subcutaneous dorsal fat, which was slightly higher in the O lambs. There were no differences between O and C lambs in terms of colour stability and lipid oxidation of the meat during the 6-day refrigerated storage under gas-permeable film.     

Near infrared reflectance spectroscopy compared with soil clay and organic matter content for estimating within-field variation in N uptake in cereals

Adjusting fertiliser applications to within-field variations in nitrogen (N) mineralisation during the growing season can increase yields, improve crop quality, reduce costs and decrease nutrient losses to the environment. Predicting such variations at a reasonable cost is therefore important. In a 3-year study, Near Infrared Reflectance (NIR) spectroscopy was compared with soil organic matter (SOM) and clay content as predictors of plant N uptake using cross-validated PLS (Partial Least Squares) regression models. Plant N uptake was measured as total nitrogen in aboveground plant parts at harvest, in plots without N fertilisation within three different fields in southern Sweden. NIR spectroscopy and combined clay and SOM content resulted in equally good estimations of plant N uptake in fields with large variation in SOM content. Cross-validated NIR calibrations for plant N uptake within fields for separate years resulted in r ² values of 0.75–0.85 and average cross-validation errors of 11–16 kg N ha⁻¹ for two fields (1 year excluded at one field because of farmyard manure application). No significant improvements were seen when NIR-spectra, clay and SOM were included in the same model, suggesting that the additional predictive capacity of NIR over SOM relates to soil texture variations. NIR calibrations also performed poorly in one field where plant N uptake could not be explained by SOM or clay content. Predictions within fields between years produced r ² values of 0.56–0.89 and prediction errors of 12–26 kg N ha⁻¹ for one field. These results confirm that N uptake prediction accuracy can be improved by using NIR spectroscopy in fields with large SOM variations. However, good estimations could not be made between fields, indicating difficulties in creating more general calibration models for large geographical areas.     

Blend uniformity analysis using stream sampling and near infrared spectroscopy

A near infrared spectroscopic method was developed to determine drug content in a 20% (wt/wt) ibuprofen and spray-dried hydous lactose blend. A blending profile was obtained after blending for 0.5, 1, 3, 5, 10, and 20 minutes. Stream sampling was used to collect about 20 blend samples at each of the blending times from a laboratory scale V-blender. The samples collected were used to develop a near infrared calibration model. The calibration model was then used to determine the drug content of unknown samples from 2 validation blends. The validation blends were not included in the calibration model; they were used to evaluate the effectiveness of the calibration model. A total of 45 samples from the 2 validation blends were predicted by the near infrared calibration model and then analyzed by a validated UV spectrophotometric method. The root mean square error of prediction for the first validation blend was 5.69 mg/g and 3.30 mg/g for the samples from the second blend. A paired t test at the 95% confidence level did not indicate any differences between the drug content predicted by the near infrared spectroscopy (NIRS) method and the validated UV method for the 2 blends. The results show that the NIRS method could be developed while the blending profile is generated and used to thoroughly characterize a new formulation during development by analyzing a large number of samples. The new formulation could be transferred to a manufacturing plant with an NIRS method to facilitate blend uniformity analysis.     

Rapid techniques for assessing fibre quality of flax breeding lines and cultivars using visible and near infrared spectroscopy, and thermal analysis

Fifteen different flax cultivars and breeding lines (E‐68, Baltu?iai, Belinka, Vega 2, Ilona, Elise, Kasty?iai, Evelin, 1963‐3, Ariane, Hermes, 01057‐12, 1698‐13a, 2017‐3, 1864‐24) were cultivated, harvested, water‐retted, scutched and resulting fibres passed through pin frames to produce representative samples for each variety. The aim of this investigation was to develop rapid techniques for assessing quality of fibre obtained from a comparative agronomical trial. The fibres produced were then assessed using visible and near infrared spectroscopy (Vis–NIRS), thermal analysis, scanning electron microscopy and airflow method for measuring fibre fineness. The relationships between agronomical characteristics, fibre fineness, thermal and spectral results were assessed using principal component analysis and partial least squares regression methods. The micrographs of the samples revealed the presence of residual pectic and cuticular tissues on all fibres, and significant differences between the 15 fibre samples were not observed. A significant relationship of the differences in fibre fineness of the test samples as measured by airflow method and Vis–NIR spectra was observed with an R² of 0.97 and standard error of calibration (SEC) of 1.69 dtex, and the former parameter also correlated with the measured thermal combustion parameters showing an R² of 0.91 and SEC of 2.86 dtex, indicating that the two rapid techniques could be used for the assessment of fibre quality of selected plants from the breeding programme. The advantages of using the two instrumental techniques compared with the existing airflow method are briefly discussed.     

Response of lamb plasma carotenoid concentration to a shift from a low to a high dietary carotenoid level

This study was conducted to investigate the pattern of plasma carotenoid concentration (PCC) in lambs switching from a low to a high dietary carotenoid level. A total of 12 Romane lambs were individually penned indoors and fed a low dietary carotenoid level for 23 days (period 1) and then a high dietary carotenoid level for 15 days (period 2). At the beginning of period 2, the lambs were 15 weeks old and weighed 29.9 kg (s.d. 2.7) on average. Lambs were fed daily (dry matter) 0.558 kg alfalfa pellets, 0.181 kg straw and 0.181 kg barley. Plasma content of total carotenoids was measured daily in period 2 by spectrophotometry. PCC (μg/l) varied with the animal (P < 0.001) and with time elapsed since the beginning of alfalfa distribution (P < 0.001). Mean PCC was 8 μg/l (s.d. 3.3) at the beginning of period 2, then increased curvilinearly with the time elapsed since the beginning of alfalfa distribution. As early as 24 h on the alfalfa diet, PCC was already higher than before the switch (P < 0.001). Mean PCC continued to increase until day 6 on average and reached a plateau thereafter. We propose a monomolecular function to model this pattern, the equation obtained on the mean data being: PCC = 97 (s.e. 2.2) × (1−exp^{(−0.3378 (s.e. 0.0282)×d)}), where r² = 0.997, r.s.d. = 4.47, n = 15 and d = day. The percentage of variance explained by the model ranged between 95.9% and 99.2%, depending on the animal. The parameters of the monomolecular function varied among animals, confirming the interindividual variability in animal response. Plateau for PCC was reached slightly earlier for the six lambs with the lowest values of the asymptote than for the six lambs with the highest values of the asymptote.     

An innovative spectroelectrochemical reflection cell for rapid protein electrochemistry and ultraviolet/visible/infrared spectroscopy

A novel electrochemical reflection cell combining electrochemical techniques and spectroscopy which uses a solid gold working electrode as an optical mirror is described. This cell can be used at path lengths as low as a few micrometers and thus is suitable for ultraviolet/visible (UV/Vis) and infrared spectroscopy even for aqueous solutions and suspensions. The cell was designed for small sample volumes of only a few microliters, thus reducing the effort for sample preparation. Due to the short path length of some micrometers, the entire volume is within the Nernst diffusion layer, hence resulting in fast equilibration. Evaluation of the technique is described with direct electrochemistry of horse heart cytochrome c at the gold electrode modified with 4,4'-dithiodipyridine. Cyclic voltammograms indicate rapid and reversible electrochemistry with the correct midpoint potential (52 mV vs Ag/AgCl/3 M KCl). Chronoamperometry and coulometry confirm rapid and complete oxidation and reduction; the cell volume can be entirely fully reduced within less than 10-20 s. Spectroscopy in the UV/Vis region, with potentials at the working electrode stepped between -390 and 390 mV, show perfect titration of the cytochrome c heme bands. A Nernst fit of the alpha band absorption, with redox potential Em and number of electrons n left as parameters, yields a midpoint potential of 49 mV and n=0.9. The potential of this cell in the investigation of biological electron transfer reactions and in the study of bioenergetic systems is discussed.