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Content archived on 2024-04-19



This project aims to establish appropriate hardware and software for fast, sensitive and reliable quality control of agro-industrial processes using fluorescence based spectroscopy and video image analysis. It links experts in various areas of processing with instrument companies. The project considers both food and non-food applications covering sugar, cereals and other seeds, lignocellulose (paper and fibres) and meat. Suitable equipment has been obtained, set up and calibrated in order to initiate spectroscopy and image-analysis calibration, together with experimental and operational protocols. The tasks can be divided into two groups. The first relates to general techniques. The second looks at applications. This report does not cover the work on meat, but includes studies on cereals and oil-seed where food and non-food applications may overlap.

In agro-industrial production systems, where efficiency has so far been considered mostly in financial terms, there is presently a growing need for reliable, rapid and cheap screening methods for quality control and environmental protection in each production step. The fluorescence phenomenon is unique because of its specificity (e.g. in detecting NADH, Shiffs bases, lignin and mycotoxins) which can be exploited both by spectrofluorimetry and by video image analysis combing specific chemical information with structural/physical. Fluorescence is up to 1000 times more sensitive than other spectroscopic methods.

The emergence of new methods in this area depends on the development of appropriate hardware and software to solve a series of problems related to the physical/chemical aspects of the fluorescence phenomenon in relation to spectra and image recording, calibration and evaluation.

In this project, the development of hardware/software for non-destructive fluorescence techniques will be based on the one hand on application of advanced computer techniques to reflectance and transmission spectroscopy and on the other hand on innovative video imaging with the aim to establish on line industrial quality control methods (task A): These techniques are applied in three major industrial areas (task B): Considering meat, fibres (e.g. pulping) and cereals (e.g. oilseeds and wheat) with regard to oxidation (meat), lignin composition (fibre), tissue composition (meat, cereals) and filth and damage (seeds). In cooperation with the instrument industry spectrofluorimetric and video sensors will be designed on the basis of the research and their markets investigated. The opportunities explored are tested in cooperation with the production industry.
Spectrofluorimetry: Two identical spectrofluorimeters (Perkin Elmer LS 50B) with computers were acquired and set up in Copenhagen and Athens. Using sugar as a model it has been found possible to predict the chemical composition of inpurities such as ash, amino nitrogen and colour using fluorescence spectra in the near infrared area. Aspects such as lamp age, temperature, slit width, scanning velocity were standardised enabling complete spectra to be applied to various specific components using appropriate software from one state of measurement to another. Using sugar obtained from six separate factories, it was shown that each sample had a unique set of fluorescence characteristics. To resolve the spectra and establish the chemical basis, compounds were separated from samples of thick juice from the same factories using capillary electrophoresis. It was found the electrophoresis pattern of the pure components correlated with the factory classification and with specific wavelengths of the spectra. The experience gained from fluorescence measurements of sugars was then applied to wheat straw pulp for which it was found that emission maxima were dependant on several chromophores in the pulp. Bleaching by hydrogen peroxide increased fluorescence while photo-yellowing of pulps was accompanied by reduced emission intensity at excitation wavelengths below 400 nm. The fluorescent microstructure of samples was investigated using a DIPEX scanning fluorescence microscope with ccd camera. Other observations ranged from simple fluorescence microscopy to the use of a high sensitivity TIDAS diode-array apparatus used to obtain fluorescence and UV spectra from flow-cuvettes and from probes.

Fluorescence video image spectroscopy: In order to design a prototype system, various experimental setups were investigated using the a cooled Photometrics ccd camera. For low magnification imaging, an Oriel lamp with 2 computer-driven filter wheels was linked to the ccd camera and a computer. Software was developed for image discrimination. Mixtures of Cassava, maize and pea flours and the pure samples were tested in a model system. The system was able to identify the mixing levels with a very high efficiency. For higher magnification the ccd camera was installed on a Leica fluorescence microscope. Fluorescence microscopy was used to photographically document impurities in oilseed lots. It was confirmed that various contaminants including weed seeds, straw and the cereals, etc have typical autofluorescence characteristics which confirm that these may be detected by the ccd camera. Such investigations are now underway with the equipment participant optimising hardware and software.

Fibre quality assessment: Work has been initiated to correlated a wide range of paper pulp quality parameters with specific fluorescence spectra.

Oilseed quality assessment: Cooperation between an oilseed growers association, a French research institute and the hardware manufacturer has resulted in an image-based device for detection of impurities in oilseeds based on fluorescence.

Cereal grain processing industries: Attempts have been made to exploit the autofluorescence characteristics of the botanical components (pericarp, aleuron, endosperm) of wheat to monitor the separation in wheat mill flour streams using a Dipex scanning fluorescence microscope, with detection of particles in a ccd-camera by image analysis software. However, this has not been commercially successful. A wide range of wheat flours with known chemical composition such as ash, protein and colour were investigated using the Dipex microscope and compared to direct reflectance measurements in the Perkin Elmer LS50B spectrofluorimeter. Results were evaluated using Unscrambler software. Excellent correlations with ash indicative for aleuron were obtained by both methods but the Dipex method was too laborious. New software is being designed to speed up the method.

This project aims to develop reliable, rapid and cheap screening methods for quality control and environmental protection in each production step within a number of agro-industrial activities. The work focuses on systems using fluorescence to detect signals which are associated with specific chemical compounds. These can then be used to characterise materials using spectrofluorimetry and/or video image analysis combing specific chemical information with structural and physical properties. Fluorescence can be up to 1000 times more sensitive than other spectroscopic methods. Applications in this area depend on the combination of appropriate hardware with computer software to solve aspects of the fluorescence phenomenon including characterisation of spectra, image recording, calibration and evaluation. This approach is applied to the development of hardware and software for non destructive fluorescence testing using advanced computer techniques for both reflectance and transmission spectroscopy together with innovative video imaging with the aim to establish on-line industrial quality control methods for both food and non-food applications. The latter includes looking at plant fibres (e.g. pulping) and cereals (e.g. oilseeds and wheat) lignin composition (fibre), tissue composition (cereals) and contamination and damage (seeds). In cooperation with the instrument industry, spectrofluorimetric and video sensors will be designed on the basis of the research and their markets investigated.

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