Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Non-destructive detection of flawed hazelnut kernels and lipid oxidation assessment using NIR spectroscopy
    Pannico, A. ; Schouten, R.E. ; Basile, B. ; Woltering, E.J. ; Cirillo, C. - \ 2015
    Journal of Food Engineering 160 (2015). - ISSN 0260-8774 - p. 42 - 48.
    corylus-avellana l. - fatty-acid-composition - near-infrared spectroscopy - reflectance spectroscopy - vis/nir spectroscopy - chemical-composition - quality - storage - fungal - seeds
    Microbial contamination, seed browning, bad taste and lipid oxidation are primary causes of quality deterioration in stored hazelnuts, affecting their marketability. The feasibility of NIR spectroscopy to detect flawed kernels and estimate lipid oxidation in in-shell and shelled hazelnuts was investigated. ‘Mortarella’ hazelnuts were measured twice by NIR spectroscopy, first in-shell, and then as kernels. Afterwards, the kernels were evaluated visually, externally and internally, and by sensory evaluation with a subsequent measurement of fat oxidation. A satisfactory PLS model was created for the detection of flawed kernels. For lipid oxidation estimation the best performance of PLS models was obtained by first removing the flawed kernels from the calibration set. The PLS model for the K232 extinction coefficient, that is indicative of lipid primary oxidation, was able to predict K232 for both in-shell (R2 = 0.79) and shelled (R2 = 0.85) hazelnuts. Our results suggest, for shelled hazelnuts, a two-step NIR procedure: a first PLS model to detect and separate flawed kernels and then a second PLS model to grade healthy kernels by lipid oxidation levels.
    Optical properties, ethylene production and softening in mango fruits
    Eccher Zerbini, P.C. ; Vanoli, M. ; Rizzolo, A. ; Grassi, M. ; Meirelles de Azevedo Pementel, A. ; Spinelli, L. ; Torricelli, A. - \ 2015
    Postharvest Biology and Technology 101 (2015). - ISSN 0925-5214 - p. 58 - 65.
    resolved reflectance spectroscopy - mangifera-indica l. - near-infrared spectroscopy - beta-carotene accumulation - kensington pride mango - long supply chains - harvest maturity - tomato fruit - postharvest behavior - biological variation
    Firmness decay, chlorophyll breakdown and carotenoid accumulation, controlled by ethylene, are major ripening events in mango fruit. Pigment content and tissue structure affect the optical properties of the mesocarp, which can be measured nondestructively in the intact fruit by time-resolved reflectance spectroscopy (TRS). This work is aimed at improving the maturity assessment in mango (Mangifera indica L. cv Haden) from Brazil, using TRS absorption in both the carotenoid and chlorophyll regions in order to develop a model for fruit ripening. Scattering and absorption in the 540–900 nm spectral range by TRS, ethylene production and respiration rate, and firmness, were measured in one day on each individual fruit of a sample covering the range of maturity. The fruit displayed a variability which was attributed to the different biological age. Absorption spectra showed two peaks at 540 and 670 nm, corresponding respectively to the tail of carotenoid absorption and to chlorophyll-a absorption. Carotenoids increased substantially only in fruit where chlorophyll had almost disappeared. The absorptions at 540 and 670 nm, which described the maturity state of each fruit relative to the range of each wavelength, were combined in one index of biological age (biological shift factor) for each fruit and used in logistic models of ethylene increase and firmness decay respectively. The model explained about 80% of the variability in ethylene production rate. A similar result was obtained for firmness when scattering was added in the model. The combination of absorption at 540 and 670 nm measured by TRS in the intact fruit can be used to classify mango fruit according to maturity and to predict the ripening of individual fruit.
    Chemical Composition, Sensory Properties, Provenance, and Bioactivity of Fruit Juices as Assessed bij Chemometrics: A Critical Review and Guideline
    Ziekinski, A.F. ; Haminiuk, C.W.I. ; Nunes, C.A. ; Schnitzler, E. ; Ruth, S.M. van; Granato, D. - \ 2014
    Comprehensive Reviews in Food Science and Food Safety 13 (2014)3. - ISSN 1541-4337 - p. 300 - 316.
    principal component analysis - near-infrared spectroscopy - performance liquid-chromatography - commercial grape juices - antioxidant activity - consumer segmentation - geographical origin - electronic tongue - phenolic content - orange juice
    The use of univariate, bivariate, and multivariate statistical techniques, such as analysis of variance, multiple comparisons of means, and linear correlations, has spread widely in the area of Food Science and Technology. However, the use of supervised and unsupervised statistical techniques (chemometrics) in order to analyze and model experimental data from physicochemical, sensory, metabolomics, quality control, nutritional, microbiological, and chemical assays in food research has gained more space. Therefore, we present here a manuscript with theoretical details, a critical analysis of published work, and a guideline for the reader to check and propose mathematical models of experimental results using the most promising supervised and unsupervised multivariate statistical techniques, namely: principal component analysis, hierarchical cluster analysis, linear discriminant analysis, partial least square regression, k-nearest neighbors, and soft independent modeling of class analogy. In addition, the overall features, advantages, and limitations of such statistical methods are presented and discussed. Published examples are focused on sensory, chemical, and antioxidant activity of a wide range of fruit juices consumed worldwide.
    Verification of fresh grass feeding, pasture grazing and organic farming by cows farm milk fatty acid profile
    Capuano, E. ; Veer, G. van der; Boerrigter-Eenling, G.R. ; Elgersma, A. ; Rademaker, J. ; Sterian, A. ; Ruth, S.M. van - \ 2014
    Food Chemistry 164 (2014). - ISSN 0308-8146 - p. 234 - 241.
    near-infrared spectroscopy - stable-isotope - linoleic-acid - cutting date - diet - authentication - transition - systems - origin
    The present study investigated the use of fatty acid (FA) profiling in combination with chemometric modelling to verify claims for cow milk in terms of fresh grass feeding, pasture grazing and organic/biodynamic farming. The FA profile was determined for 113 tank milk samples collected in the Netherlands from 30 farms over four different months, and used to develop classification models based on the PLS-DA algorithm. Milk from cows with daily rations of fresh grass could be successfully distinguished from milk from cows with no fresh grass in their diet. Milk from cows at pasture could easily be distinguished from milk from stabled cows without fresh grass in the diet, but the correct prediction of milk from stabled cows fed fresh grass indoors proved difficult. The FA profile of organic/biodynamic milk was different compared to conventional milk but an unequivocal discrimination was not possible either in summer or in winter.
    Effect of fresh grass feeding, pasture grazing and organic/biodynamic farming on bovine milk triglyceride profile and implications for authentication
    Capuano, E. ; Boerrigter-Eenling, G.R. ; Eigersma, A. ; Ruth, S.M. van - \ 2014
    European Food Research and Technology 238 (2014)4. - ISSN 1438-2377 - p. 573 - 580.
    near-infrared spectroscopy - fat composition - organic feed - dairy-cows - acid - forage
    In the present study, 113 tank milk samples were collected from 30 farms located in the Netherlands and analyzed for their triacylglycerol (TAG) and cholesterol profiles. Significant differences in the TAG profile between winter and spring–early summer milk were observed. The differences between milk from cows on pasture and stabled cows collected in spring–early summer were less remarkable than those between spring–early summer and winter milk. Classification models based on partial least square discriminant analysis of the TAG profile were developed for the prediction of fresh grass feeding, pasture grazing and organic farming. Milk from cows that had fresh grass in the daily ration could be distinguished from milk from cows that had no fresh grass with sensitivity and specificity values >85 %. However, the specificity reduced to 72 % when the samples collected in spring–early summer were considered only. Authentication of pasture grazing and of organic/biodynamic farming based on TAG profile proved difficult during the grazing period.
    Verification of fresh grass feeding, pasture grazing and organic farming by FTIR spectroscopy analysis of bovine milk
    Capuano, E. ; Rademaker, J. ; Bijgaart, H. van den; Ruth, S.M. van - \ 2014
    Food Research International 60 (2014). - ISSN 0963-9969 - p. 59 - 65.
    near-infrared spectroscopy - fatty-acid-composition - total mixed ration - geographic origin - edible oils - dairy-cows - fluorescence - cheese - food - differentiation
    In the present study, a total of 116 tank milk samples were collected from 30 farms located in The Netherlands and analysed by Fourier-transform infrared (FTIR) spectroscopy. Samples were collected in April, May and June 2011 and in February 2012. The samples differed in the time spent by the cows on pasture, presence/absence of fresh grass in the daily ration and the farming system (organic/biodynamic or conventional). Classification models based on partial least square discriminant analysis (PLS-DA) of FTIR spectra were developed for the prediction of fresh grass feeding, pasture grazing and organic farming. The PLS-DA model discriminated between milk from cows that had fresh grass in the daily ration and milk from cows that had not fresh grass with sensitivity and specificity values of 88% and 83% in external validation and all the samples from cows that had no fresh grass collected in spring were correctly classified. The PLS-DA model developed for the authentication of pasture grazing showed comparable accuracy when the whole sample set is considered but was less accurate on the spring samples (75% of samples from cows indoors in spring correctly classified). Discrimination of organic and conventional milk was also accomplished with acceptable accuracy with % correct classification of 80% and 94% respectively in external validation. The results suggest that milk FTIR spectra contain valuable information on cows' diet that can be used for authentication purposes.
    Evaluation and implementation of vis-NIR spectroscopy models to determine workability
    Mahmood, H.S. ; Bartholomeus, H. ; Hoogmoed, W.B. ; Henten, E. van - \ 2013
    Soil & Tillage Research 134 (2013). - ISSN 0167-1987 - p. 172 - 179.
    near-infrared spectroscopy - diffuse-reflectance spectroscopy - soil organic-carbon - spectral library - workable range - tropical zone - prediction - field - calibrations - veracruz
    Quantitative information of soil properties and their spatial distribution is needed for site-specific soil management. Conventional laboratory methods to obtain high-resolution soil data are expensive and labour intensive. Visible-near infrared (vis-NIR) reflectance spectroscopy is a rapid and cost-effective technique for successful soil characterisation. The objective of this study was to determine the accuracy of vis-NIR reflectance models to predict tillage (workability) related soil properties, such as texture and total organic carbon (TOC) and other common soil properties on a field scale using different types of modelling strategies. For prediction of these properties, spectral data were related to soil properties using support vector regression. For this method, the influence of calibration set on the accuracy of prediction for independent samples was evaluated. The types of models included local models (LMs; models of individual fields), general models (GMs; models of combining equal proportions of samples from all fields), spiked models (SMs; using 10 samples from the target field and all samples from other fields) and true validation models (TVMs; calibration from four fields and validation in the remaining field). The main difference between these models lies in the number of soil samples that need to be taken from a specific field of interest, which determines the investments that have to be made. Results revealed that LMs gave the best results (e.g. the RMSEP was less than 1.7% for clay in all fields), but a large number of samples has to be taken from each field, which costs a lot of time and money. Therefore, this type of models may not be so practical for a farmer having multiple fields. The GMs showed variable accuracies for different sized models, where the accuracy increases with increasing the number of samples in the calibration subset. This means that a large number of samples is needed for making a good calibration model and therefore GMs may also not be so effective. The TVMs are cheap to make, but the risk of wrong predictions in the target field, which is different from the calibration fields, is present. The SMs yielded predictions comparable to the LMs and yielded an acceptable RMSEP with a limited number of samples per field (10 samples) for clay and TOC. This makes SMs very effective with the potential to predict workability related soil properties with a limited number of samples in the target fields
    Differentiation of specialty coffees by proton transfer reaction-mass spectrometry
    Özdestan, Ö. ; Ruth, S.M. van; Alewijn, M. ; Koot, A.H. ; Romano, A. ; Cappelin, L. ; Biasioli, F. - \ 2013
    Food Research International 53 (2013)1. - ISSN 0963-9969 - p. 433 - 439.
    near-infrared spectroscopy - volatile organic-compounds - geographical origin - roasted coffee - ptr-ms - gas-chromatography - authentication - discrimination - products - identification
    In the coffee sector a diversity of certifications is available, with the most well-known being organic and fair trade. Intrinsic markers of products may help to assure the authenticity of food products and complement administrative controls. In the present study 110 market coffees with special production traits were characterized by high sensitivity proton transfer reaction mass spectrometry (HS PTR-MS) and volatiles were tentatively identified by PTR-time of flight MS. Espresso coffees, Kopi Luwak coffee and organic coffees could be distinguished by their profiles of volatile compounds with the help of chemometrics. A PLS-DA classification model was estimated to classify the organic and regular coffees by their HS PTR-MS mass spectra. Cross validation showed correct prediction of 42 out of the 43 (98%) organic coffee samples and 63 out of the 67 (95%) regular coffee samples. Therefore, the presented strategy is a promising approach to rapid organic coffee authentication.
    Changes in plant defense chemistry (pyrrolizidine alkaloids) revealed through high-resolution spectroscopy
    Almeida De Carvalho, S. ; Macel, M. ; Schlerf, M. ; Moghaddam, F.E. ; Mulder, P.P.J. ; Skidmore, A.K. ; Putten, W.H. van der - \ 2013
    ISPRS Journal of Photogrammetry and Remote Sensing 80 (2013). - ISSN 0924-2716 - p. 51 - 60.
    near-infrared spectroscopy - senecio-jacobaea - red edge - nitrogen - leaf - reflectance - forest - regression - vegetation - prediction
    Plant toxic biochemicals play an important role in defense against natural enemies and often are toxic to humans and livestock. Hyperspectral reflectance is an established method for primary chemical detection and could be further used to determine plant toxicity in the field. In order to make a first step for pyrrolizidine alkaloids detection (toxic defense compound against mammals and many insects) we studied how such spectral data can estimate plant defense chemistry under controlled conditions. In a greenhouse, we grew three related plant species that defend against generalist herbivores through pyrrolizidine alkaloids: Jacobaea vulgaris, Jacobaea erucifolia and Senecio inaequidens, and analyzed the relation between spectral measurements and chemical concentrations using multivariate statistics. Nutrient addition enhanced tertiary-amine pyrrolizidine alkaloids contents of J. vulgaris and J. erucifolia and decreased N-oxide contents in S. inaequidens and J. vulgaris. Pyrrolizidine alkaloids could be predicted with a moderate accuracy. Pyrrolizidine alkaloid forms tertiary-amines and epoxides were predicted with 63% and 56% of the variation explained, respectively. The most relevant spectral regions selected for prediction were associated with electron transitions and CH, OH, and NH bonds in the 1530 and 2100 nm regions. Given the relatively low concentration in pyrrolizidine alkaloids concentration (in the order of mg g-1) and resultant predictions, it is promising that pyrrolizidine alkaloids interact with incident light. Further studies should be considered to determine if such a non-destructive method may predict changes in PA concentration in relation to plant natural enemies. Spectroscopy may be used to study plant defenses in intact plant tissues, and may provide managers of toxic plants, food industry and multitrophic-interaction researchers with faster and larger monitoring possibilities
    Predicting foliar biochemistry of tea (Camellia sinensis) using reflectance spectra measured at powder, leaf and canopy levels
    Bian, B.M. ; Skidmore, A.K. ; Schlerf, M. ; Wang, T. ; Liu, X. ; Zeng, R. ; Fei, T. - \ 2013
    ISPRS Journal of Photogrammetry and Remote Sensing 78 (2013). - ISSN 0924-2716 - p. 148 - 156.
    near-infrared spectroscopy - green tea - chlorophyll content - squares regression - amino-acids - hyperspectral measurements - imaging spectrometry - vegetation indexes - continuum removal - forest canopy
    Some biochemical compounds are closely related with the quality of tea (Camellia sinensis (L.)). In this study, the concentration of these compounds including total tea polyphenols, free amino acids and soluble sugars were estimated using reflectance spectroscopy at three different levels: powder, leaf and canopy, with partial least squares regression. The focus of this study is to systematically compare the accuracy of tea quality estimations based on spectroscopy at three different levels. At the powder level, the average r2 between predictions and observations was 0.89 for polyphenols, 0.81 for amino acids and 0.78 for sugars, with relative root mean square errors (RMSE/mean) of 5.47%, 5.50% and 2.75%, respectively; at the leaf level, the average r2 decreased to 0.46-0.81 and the relative RMSE increased to 4.46-7.09%. Compared to the results yielded at the leaf level, the results from canopy spectra were slightly more accurate, yielding average r2 values of 0.83, 0.77 and 0.56 and relative RMSE of 6.79%, 5.73% and 4.03% for polyphenols, amino acids and sugars, respectively. We further identified wavelength channels that influenced the prediction model. For powder and leaves, some bands identified can be linked to the absorption features of chemicals of interest (1648nm for phenolic, 1510nm for amino acids, 2080nm and 2270nm for sugars), while more indirectly related wavelengths were found to be important at the canopy level for predictions of chemical compounds. Overall, the prediction accuracies achieved at canopy level in this study are encouraging for future study on tea quality estimated at the landscape scale using airborne and space-borne sensors.
    Developments in mycotoxin analysis: an update for 2008-2009
    Shephard, G.S. ; Berthiller, F. ; Dorner, J. ; Krska, R. ; Lombaert, G.A. ; Malone, B. ; Maragos, C. ; Sabino, M. ; Solfrizzo, M. ; Trucksess, M.W. ; Egmond, H.P. van; Whitaker, T.B. - \ 2010
    World Mycotoxin Journal 3 (2010)1. - ISSN 1875-0710 - p. 3 - 23.
    performance liquid-chromatography - linked-immunosorbent-assay - tandem mass-spectrometry - corn-based food - immunoaffinity column cleanup - fluorescence detection method - single-laboratory validation - near-infrared spectroscopy - resorcylic acid lactones - afl
    This review highlights developments in mycotoxin analysis and sampling over a period between mid-2008 and mid-2009. It covers the major mycotoxins: aflatoxins, alternaria toxins, cyclopiazonic acid, fumonisins, ochratoxin, patulin, trichothecenes and zearalenone. Developments in mycotoxin analysis continue, with emphasis on novel immunological methods and further description of LC-MS and LC-MS/MS, particularly as multimycotoxin applications for different ranges of mycotoxins. Although falling outside the main emphasis of the review, some aspects of natural occurrence have been mentioned, especially if linked to novel method developments.
    Gene-expression-based quality scores indicate optimal harvest point in Bordetella pertussis cultivation for vaccine production
    Waterbeemd, B. van de; Streefland, M. ; Pennings, J. ; Pol, L.A. van der; Beuvery, E.C. ; Tramper, J. ; Martens, D.E. - \ 2009
    Biotechnology and Bioengineering 103 (2009)5. - ISSN 0006-3592 - p. 900 - 908.
    near-infrared spectroscopy - escherichia-coli - culture - transcriptome - complex - design - growth - pat
    The evolution of vaccine product quality during batch cultivation of Bordetella pertussis, the causative agent of whooping cough, was investigated with the goal to determine the optimal harvest point. The process was explored by measuring mRNA expression at frequent intervals during cultivation. The genes that are involved in virulence are already known for this product and changes in their expression levels are proposed to be indicative for product quality. A quantitative product quality score is calculated based on the expression levels of these virulence genes, which allows comparison of expected product quality between culture samples. Product quality scores were maximal throughout the logarithmic growth phase, but dropped significantly at the start of the stationary phase. This showed that the decreasing lactate and glutamate concentrations towards the end of the batch are critical for product quality. On-line measurement of these nutrients allows the cultivation process to be harvested at the optimal harvest point, increasing process robustness and consistency
    Spectral reflectance based indices for soil organic carbon quantification
    Bartholomeus, H. ; Schaepman, M.E. ; Kooistra, L. ; Stevens, A. ; Hoogmoed, W.B. ; Spaargaren, O.C. - \ 2008
    Geoderma 145 (2008)1-2. - ISSN 0016-7061 - p. 28 - 36.
    near-infrared spectroscopy - least-squares regression - agricultural soils - matter - nitrogen - calibration - moisture - world - nm
    We investigated 40 samples from nine different soil types, originating from several climatic zones and a large variety in SOC content (0.06-45.1%). Spectral measurements for all soil samples were performed in a controlled laboratory environment. We tested the performance of several spectral indices which have been developed to detect biochemical constituents (e.g., cellulose, lignin) for their ability to retrieve SOC, and compared it to PLS. Good relations were found for indices based on the visible part of the spectrum(R-2=0.80) and for the absorption features related to cellulose (around 2100 nm) (R-2=0.81). The best index based relations were compared to the results for PLS (R-2=0.87). Cross validation was used to evaluate the predictive capacity of the spectral indices. The results demonstrate that it is feasible to use spectral indices derived from laboratory measurements to predict SOC in various soil types. However, a large variance in SOC is required for the calibration of the prediction model, since extrapolation beyond the SOC range in the training dataset results in large errors. PLS proves to be much less sensitive towards extrapolation of the model beyond the mineralogy and SOC levels used during the calibration. (c) 2008 Elsevier B.V. All rights reserved.
    The potential of field spectroscopy for the determination of sediment properties in river floodplains
    Kooistra, L. ; Wanders, J. ; Epema, G.F. ; Leuven, R.S.E.W. ; Wehrens, H.R.M.J. ; Buydens, L.M.C. - \ 2003
    Analytica Chimica Acta 484 (2003)2. - ISSN 0003-2670 - p. 189 - 200.
    bodemeigenschappen - geologische sedimentatie - stroomvlakten - rivieren - spectroscopie - klei - organische stof - nederland - bodemkwaliteit - rijn - soil properties - geological sedimentation - floodplains - rivers - spectroscopy - clay - organic matter - netherlands - soil quality - river rhine - diffuse-reflectance spectroscopy - near-infrared spectroscopy - organic-matter - contamination - calibration - networks
    Investigations have shown that visible-near-infrared (VNIR) spectroscopy can accurately determine soil properties under laboratory conditions. In situ assessment of soil properties is of great benefit for several applications, as spectra can be acquired fast and almost continuously. The present study used partial least squares (PLS) regression to establish a relationship between soil reflectance spectra measured under field conditions and the organic matter and clay content of the soil. Spectra were acquired with a fieldspectrometer in a recently reconstructed floodplain along the river Rhine in The Netherlands. Several spectral pre-processing methods were employed to improve the performance and robustness of the models. Results indicate that, under varying surface conditions, field spectroscopy in combination with multivariate calibration does result in a qualitative relation for organic matter (R2=0.45) and clay content (R2=0.43) while under laboratory conditions more accurate results are obtained (R2=0.69 and 0.92, respectively). Soil moisture and vegetation cover had a negative influence on the prediction capabilities for both soil properties. Although the performance of the spectra measured in situ is not as accurate as physical analysis, the accuracy obtained is useful for rapid soil characterisation and remote sensing applications.
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