Browsing by Subject "Near-infrared spectroscopy"

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    Application of Near-Infrared Spectroscopy in Plant Breeding Programs
    (2006) Montes, Juan Manuel; Melchinger, Albrecht E.
    The success of plant breeding programs depends on the availability of genetic variation and efficient data collection processes that allow large-scale screenings of genotypes. When genetic variation is present, the goal is to identify those genotypes that are closest to the breeding objectives. In this context, the evaluation of a large number of genotypes requires optimization of the data collection process in order to provide reliable information for making selection decisions. The process of data collection must yield an accurate and precise assessment of genotypes timely because the information is needed to plan the next generation for breeding and cultivar development. Laboratory NIRS is routinely used in the data collection process of many breeding programs, but it requires the withdrawal of field plot samples and involves manual work. Applications of the near-infrared spectroscopy on choppers (NOC) and near-infrared spectroscopy on combine harvester (NOCH) are a step forward to the automation of data collection processes, by which sampling, labor, and sources of error in the data can be reduced. The objective of this thesis research was to assess the potential of NOC and NOCH for application in breeding programs of grain maize, rapeseed, and silage maize. Plot combine harvesters and choppers were equipped with diode-array spectrometers for collection of near-infrared plot spectra, and used to harvest experimental varieties of breeding programs in Central Europe. Two alternative sample presentation designs (conveyor belt and spout) were used for the NOC systems. The NOCH systems used the conveyor belt as sample presentation design. NOCH showed a high potential for determination of dry matter (DM), crude protein (CP), and starch (ST) contents of maize grain. NOCH calibration models yielded standard errors of prediction (SEP) and coefficients of determination of validation (R2V) of 1.2% and 0.95 for DM, 0.3% and 0.88 for CP, and 1.0% and 0.79 for ST, respectively. The potential of NOCH for determination of DM, CP, oil and glucosinolate contents of rapeseed was also high. NOCH calibration models yielded standard errors of cross validation (SECV) and coefficients of determination of cross validation (R2CV) of 0.3% and 0.96 for DM, 0.6% and 0.69 for CP, 0.9% and 0.71 for oil, and 2.2 μmol/g and 0.40 for glucosinolate, respectively. The NOC systems showed high potential for the determination of DM, ST, and soluble sugars (SS) content of silage maize hybrids. The NOC system equipped with a conveyor belt design yielded calibration models with SEP and R2V of 0.9% and 0.93 for DM, and 2.1% and 0.78 for ST, respectively. For the NOC system equipped with the spout design, the SEP and R2V amounted to 1.4% and 0.84 for DM, 2.3% and 0.75 for ST, and 0.9% and 0.81 for SS. The potential of both NOC systems for determination of fiber contents (CF, ADF, and NDF), digestibility and energy-related traits was lower than for DM, ST, and SS. The precision of NOCH for the determination of DM content in maize grain was higher than by traditional drying-oven method. A higher precision of NOCH is also expected for other traits and may also be extended to the NOC systems because the sampling error associated with traditional processes of data collection is reduced drastically by NOC and NOCH. The investigation of the effects caused by the calibration technique, mathematical transformation of the near-infrared spectra, and scatter correction on the development of NOCH calibration models for the prediction of DM, CP, and ST content in maize grain revealed that calibration technique was the most important factor affecting the prediction ability, whereas the importance of mathematical transformation and scatter correction depended on the particular constituent considered. Presently, there exists high uncertainty about the optimal NOC and NOCH sample presentation designs for agricultural harvesters. The dynamic signal range, i.e., the range of spectral values on which predictions are based, and the amount of plot material measured were identified as guide parameters for optimization of sample presentation designs. In addition, calibration transferability between NOC systems with different sample presentation designs proved to be feasible after merging spectra from both NOC systems in the calibration set. In conclusion, NOC and NOCH show high potential for replacing laboratory NIRS analysis of several traits in a plant breeding context and yield a more accurate and precise evaluation of field plot characteristics. Therefore, technological applications of the electromagnetic radiation is predicted to have a high impact in plant breeding, precision farming, and agriculture.
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    The potential of near-infrared spectroscopy (NIRS) as a rapid method to evaluate the aroma profiles of winemaking grapes
    (2023) Gehlken, Jana; Zörb, Christian
    The production of high-quality wines requires the use of high-quality grapes. For wines produced from certain grape varieties or grapes grown in specific cultivation regions, certain aroma impressions are expected, which often result from compounds already present in the grapes. Other compounds may negatively influence odour or flavour of the wine in their original form or as precursors for off-odours or off-flavours. Therefore, a rapid evaluation of grape aroma quality directly upon receival at the winery is advantageous. Grape aroma is usually evaluated by tasting, which leads to subjective results. Common instrumental analysis for aroma evaluation is time- and cost-intensive, which makes it inappropriate for rapid quality evaluation. The use of near-infrared (NIR) spectroscopy allows the simultaneous determination of various compounds without previous sample preparation. Moreover, the measurement is non-destructive, which allows an easy integration into existing processes and real-time analysis without additional sampling. Preliminary studies on the use of NIR spectroscopy for the evaluation of fruits and fruit products, with special regards to grapes, wine and wine aroma, were reviewed. In fruits and fruit products, a large number of different compounds was examined for maturity and quality evaluation. Only in few studies, sensory attributes were examined for quality evaluation and no published reports were available about the determination of specific fruit aroma compounds. In grapes and wine, NIR spectroscopy was mainly used for maturity determination and control of the alcoholic fermentation. For the evaluation of wine quality, numerous different compounds as well as the differentiation of grape varieties and cultivation regions were examined. For aroma evaluation, both specific aroma compounds and sensory attributes were examined in finished wines. Grape aroma was only evaluated in very few studies and in all of them glycosylated compounds were examined. Although these compounds play a key role in wine aroma, grapes contain numerous other compounds from various chemical classes, which may also considerably influence the aroma of the wine. Therefore, it is beneficial to acquire precise knowledge about the total aroma profile of winemaking grapes. Moreover, the majority of the preliminary studies was only performed under laboratory conditions. Based on these findings, the aroma profiles of grapes upon receival at wineries were examined. Grape mash samples from different wineries were examined for aroma compounds by gas chromatography-mass spectrometry (GC-MS). Instead of previous extraction of the aroma compounds, the conditions for measurement were chosen as similar as possible to those in the mouth (e.g. temperature, pH value, enzymes), to detect only compounds, which are released during tasting. The determined concentrations of the aroma compounds were related to the corresponding NIR spectra to calculate calibration models. Additionally, selected aroma compounds were grouped according to their flavour descriptions and calibration models for the determination of sensory attributes were developed. The aroma profiles of several grape mash samples showed clear differences. In some grape varieties, high concentration of four different terpenoids were measured, while other varieties showed considerably lower concentrations or no detection was possible. The concentrations of these four compounds allowed a rough classification of the samples into different aroma types. The phytosanitary status of the grapes also influenced the aroma profiles. Samples, which had been classified as “rotten” in previous examinations, showed significantly higher concentrations of various aroma compounds than samples from “sound” grapes. The addition of artificial saliva solution before analysis had no significant effect on the concentrations of the aroma compounds. The calibration models for the single aroma compounds showed varying results. Separate calibration models for cultivation region and/or grape colour lead to increased prediction accuracies compared to global calibration models. For the determination of sensory attributes only global calibration models could be developed due to the small number of samples. All models already showed very high prediction accuracies. The calibration models for the sensory attributes were compared to the result from a sensory evaluation of grape model solutions, which contained the same aroma compounds used for the calculation of the reference values for the development of the calibration models. The results from the sensory evaluation showed a large variation of the single values, however, the average values for the single odour and flavour impressions partly showed clear differences. In most cases, this could be explained by high concentrations of certain aroma compounds, which were related to the same sensory impressions for calibration model development (e.g. linalool for “floral”). However, grouping of the results according to the different model solutions was not possible. The calibration models for the single aroma compounds allow a semi-quantitative determination of numerous compounds by NIR spectroscopy, partly even a quantitative determination is possible. The intensity of various sensory attributes can also be determined. However, to ensure sufficient prediction accuracies, further samples need to be evaluated to extend the calibration models. The use of NIR spectroscopy upon receival at the winery enables an immediate evaluation of grape aroma quality, which can be used as an additional quality parameter. Furthermore, decisions can be made about the treatment of the grapes based on the results to choose the optimum conditions for the production of high-quality wines.
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    Ruminal degradation characteristics of barley, rye, and triticale grains assayed in situ and in vitro, and by near-infrared spectroscopy
    (2017) Krieg, Jochen; Rodehutscord, Markus
    The milk yield of dairy cows and related energy and protein requirements have steadily increased in the last few decades. Since feed intake has not increased to the same extent as nutritional requirements, the concentration of nutrients in mixed rations had to be increased. An increase in energy concentration is often achieved by the inclusion of high levels of cereal grains. In the EU—apart from wheat—barley, rye, and triticale are widely cultivated cereal grains. Starch (ST), followed by crude protein (CP), is the main constituent of cereal grains. The rate and extent of ruminal CP and ST degradation can influence the performance and health of dairy cows, but data that can enable the comparison of ruminal degradation within and between barley, rye, and triticale grains are scarce. Commonly used techniques to explore ruminal degradation of feed are in situ and in vitro incubations. Both techniques require ruminal-fistulated animals, but alternative methods are being demanded by the community, in order to reduce the number of animal trials. An approach with the potential to estimate the nutritional value of various feeds is near-infrared spectroscopy (NIRS). The present thesis has two major parts. In the first part, ruminal degradation parameters and the effective degradability (ED) of DM, CP, and ST from barley, rye, and triticale grains are investigated using standardised in situ and in vitro incubation techniques. A total of 20 genotypes per grain species were used. In the second part, NIRS calibrations were developed with the aim of estimating the CP and ST concentrations of cereal grains and their incubation residues. Subsequently, data from in situ experiments were used to establish the calibrations for estimating the ruminal in situ degradation of cereal grains from their spectral data. In situ degradation studies have been conducted by ruminal incubation, utilising three lactating cows. Ruminal degradation parameters and ED (ruminal passage rate = 8%//h) were calculated. For in vitro incubations, the samples were incubated in a rumen fluid-buffer mixture (‘Hohenheim Gas Test’). The gas production was recorded for estimating gas production kinetics. In vitro gas production—in combination with crude nutrient concentrations—was used to estimate the metabolisable energy concentration (ME) and digestibility of organic matter (dOM). The degradation rates differed between and within the grain species for DM, CP, and ST. The variation within grain species was not reflected in the ED of CP and ST, due to the relatively fast and almost complete degradation of the grains. The ED of CP was 77% (69–80%) for barley, 85% (83–86%) for rye, and 82% (79–84%) for triticale. The corresponding ED of ST was 86% (82–88%), 95% (92–96%), and 94% (90–95%). Accordingly, the estimated ME (barley: 13.5 MJ/kg DM, rye: 13.9 MJ/kg DM, triticale: 13.5 MJ/ kg DM) showed only relatively minor variation within one grain species. The dOM was overall at a high level (barley: 91.3%, rye: 95.3%, triticale: 95.8%). The relatively small variation within one grain species could not be explained by the chemical and physical characteristics of the samples. Hence, it was concluded that it is feasible to use mean values for every species in feed formulation and ration planning. In the second part of this thesis, it was shown that it is possible to replace chemical CP and ST analyses of samples from in situ studies by NIRS without affecting the calculated ruminal degradation characteristics. NIRS could be used to estimate the ED of CP and ST from cereal grains. The sample set to establish the calibrations included barley, durum, maize, rye, triticale, and wheat grains. Calibrations for the CP and ST concentration were extended to pea samples. The calibrations with the best validation performance for CP and ST concentration were obtained by using the wavelength segment of 1250 to 2450 nm and the first derivative of the spectra (CP: R2 = 0.99; SEP = 0.46% DM. ST: R2 = 0.99; SEP = 2.10% DM). The results of in situ studies did not differ, irrespective of whether chemical or NIRS analysis was used. Like the CP and ST concentration, the ED was estimated with a high accuracy (ED8 CP: R2 = 0.95; SEP = 2.43%. ED8 ST: R2 = 0.97; SEP = 2.45%). However, calibrations need to be extended before they can be recommended for routine use. The present thesis demonstrates that the ED of CP and ST of barley, rye, and triticale grains differ between the species, but variation within one grain species is relatively small and not related to the chemical and physical characteristics of the grain. Hence, under the prevailing cultivation conditions, the mean values for each grain species in feed evaluation are deemed adequate. It was demonstrated that NIRS has the potential to facilitate the evaluation of the nutritive value of cereal grains for ruminants.